bims-crepig 2021-01-31 papers

bims-crepig

Biomed News

on Chromatin regulation and epigenetics in cell fate and cancer

Issue of 2021–01–31
thirty papers selected by
Connor Rogerson, University of Cambridge, MRC Cancer Unit

A comprehensive enhancer screen identifies TRAM2 as a key and novel mediator of YAP oncogenesis.
Inferring time series chromatin states for promoter-enhancer pairs based on Hi-C data.
Foxc1 establishes enhancer accessibility for craniofacial cartilage differentiation.
PEREGRINE: A genome-wide prediction of enhancer to gene relationships supported by experimental evidence.
Changes in genome architecture and transcriptional dynamics progress independently of sensory experience during post-natal brain development.
Conserved regulatory logic at accessible and inaccessible chromatin during the acute inflammatory response in mammals.
Transcriptionally active enhancers in human cancer cells.
Single cell epigenetic visualization assay.
DNA methylation-linked chromatin accessibility affects genomic architecture in Arabidopsis.
FIREcaller: Detecting frequently interacting regions from Hi-C data.
De novo DNA methyltransferase activity in colorectal cancer is directed towards H3K36me3 marked CpG islands.
H3K27me3-rich genomic regions can function as silencers to repress gene expression via chromatin interactions.
Brd2/4 and Myc regulate alternative cell lineage programmes during early osteoclast differentiation in vitro.
Hox13-Mediated Dbx2 Regulation In Limbs Suggests Inter-Tad Sharing Of Enhancers.
Epigenetic reprogramming rewires transcription during the alternation of generations in Arabidopsis.
Subtraction-free and bisulfite-free specific sequencing of 5-methylcytosine and its oxidized derivatives at base resolution.
Single-cell transcriptomic reveals molecular diversity and developmental heterogeneity of human stem cell-derived oligodendrocyte lineage cells.
Accessible chromatin regions and their functional interrelations with gene transcription and epigenetic modifications in sorghum genome.
Serine biosynthesis is a metabolic vulnerability in IDH2-driven breast cancer progression.
MED19 alters AR occupancy and gene expression in prostate cancer cells, driving MAOA expression and growth under low androgen.
Succinylation of H3K122 destabilizes nucleosomes and enhances transcription.
Epithelial expression of Gata4 and Sox2 regulates specification of the squamous-columnar junction via MAPK/ERK signaling in mice.
Dynamics of genome architecture and chromatin function during human B cell differentiation and neoplastic transformation.
CRISPRi enables isoform-specific loss-of-function screens and identification of gastric cancer-specific isoform dependencies.
The transcriptional regulator MEIS2 sets up the ground state for palatal osteogenesis in mice.
TALEN outperforms Cas9 in editing heterochromatin target sites.
3D Genome of macaque fetal brain reveals evolutionary innovations during primate corticogenesis.
IDH1 mutations induce organelle defects via dysregulated phospholipids.
The FKH domain in FOXP3 mRNA frequently contains mutations in hepatocellular carcinoma that influence the subcellular localization and functions of FOXP3.
Dynamic CTCF binding directly mediates interactions among cis-regulatory elements essential for hematopoiesis.

Genome Biol. 2021 Jan 29. 22(1): 54

A comprehensive enhancer screen identifies TRAM2 as a key and novel mediator of YAP oncogenesis.

Li Li, Alejandro P Ugalde, Colinda L G J Scheele, Sebastian M Dieter, Remco Nagel, Jin Ma, Abhijeet Pataskar, Gozde Korkmaz, Ran Elkon, Miao-Ping Chien, Li You, Pin-Rui Su, Onno B Bleijerveld, Maarten Altelaar, Lyubomir Momchev, Zohar Manber, Ruiqi Han, Pieter C van Breugel, Rui Lopes, Peter Ten Dijke, Jacco van Rheenen, Reuven Agami.

   BACKGROUND: Frequent activation of the co-transcriptional factor YAP is observed in a large number of solid tumors. Activated YAP associates with enhancer loci via TEAD4-DNA-binding protein and stimulates cancer aggressiveness. Although thousands of YAP/TEAD4 binding-sites are annotated, their functional importance is unknown. Here, we aim at further identification of enhancer elements that are required for YAP functions.
RESULTS: We first apply genome-wide ChIP profiling of YAP to systematically identify enhancers that are bound by YAP/TEAD4. Next, we implement a genetic approach to uncover functions of YAP/TEAD4-associated enhancers, demonstrate its robustness, and use it to reveal a network of enhancers required for YAP-mediated proliferation. We focus on EnhancerTRAM2, as its target gene TRAM2 shows the strongest expression-correlation with YAP activity in nearly all tumor types. Interestingly, TRAM2 phenocopies the YAP-induced cell proliferation, migration, and invasion phenotypes and correlates with poor patient survival. Mechanistically, we identify FSTL-1 as a major direct client of TRAM2 that is involved in these phenotypes. Thus, TRAM2 is a key novel mediator of YAP-induced oncogenic proliferation and cellular invasiveness.
CONCLUSIONS: YAP is a transcription co-factor that binds to thousands of enhancer loci and stimulates tumor aggressiveness. Using unbiased functional approaches, we dissect YAP enhancer network and characterize TRAM2 as a novel mediator of cellular proliferation, migration, and invasion. Our findings elucidate how YAP induces cancer aggressiveness and may assist diagnosis of cancer metastasis.

Keywords:  Enhancer; Gene regulation; Invasion; Migration; Proliferation; TRAM2; YAP

DOI:  https://doi.org/10.1186/s13059-021-02272-8
BMC Genomics. 2021 Jan 28. 22(1): 84

Inferring time series chromatin states for promoter-enhancer pairs based on Hi-C data.

Henriette Miko, Yunjiang Qiu, Bjoern Gaertner, Maike Sander, Uwe Ohler.

   BACKGROUND: Co-localized combinations of histone modifications ("chromatin states") have been shown to correlate with promoter and enhancer activity. Changes in chromatin states over multiple time points ("chromatin state trajectories") have previously been analyzed at promoter and enhancers separately. With the advent of time series Hi-C data it is now possible to connect promoters and enhancers and to analyze chromatin state trajectories at promoter-enhancer pairs.
RESULTS: We present TimelessFlex, a framework for investigating chromatin state trajectories at promoters and enhancers and at promoter-enhancer pairs based on Hi-C information. TimelessFlex extends our previous approach Timeless, a Bayesian network for clustering multiple histone modification data sets at promoter and enhancer feature regions. We utilize time series ATAC-seq data measuring open chromatin to define promoters and enhancer candidates. We developed an expectation-maximization algorithm to assign promoters and enhancers to each other based on Hi-C interactions and jointly cluster their feature regions into paired chromatin state trajectories. We find jointly clustered promoter-enhancer pairs showing the same activation patterns on both sides but with a stronger trend at the enhancer side. While the promoter side remains accessible across the time series, the enhancer side becomes dynamically more open towards the gene activation time point. Promoter cluster patterns show strong correlations with gene expression signals, whereas Hi-C signals get only slightly stronger towards activation. The code of the framework is available at https://github.com/henriettemiko/TimelessFlex .
CONCLUSIONS: TimelessFlex clusters time series histone modifications at promoter-enhancer pairs based on Hi-C and it can identify distinct chromatin states at promoter and enhancer feature regions and their changes over time.

Keywords:  Chromatin immunoprecipitation; Differentiation; Enhancer; Gene regulation; Hi-C; Histone modifications

DOI:  https://doi.org/10.1186/s12864-021-07373-z
Elife. 2021 Jan 27. pii: e63595. [Epub ahead of print]10

Foxc1 establishes enhancer accessibility for craniofacial cartilage differentiation.

Pengfei Xu, Haoze V Yu, Kuo-Chang Tseng, Mackenzie Flath, Peter Fabian, Neil Segil, J Gage Crump.

  The specification of cartilage requires Sox9, a transcription factor with broad roles for organogenesis outside the skeletal system. How Sox9 and other factors gain access to cartilage-specific cis-regulatory regions during skeletal development was unknown. By analyzing chromatin accessibility during the differentiation of neural crest cells into chondrocytes of the zebrafish head, we find that cartilage-associated chromatin accessibility is dynamically established. Cartilage-associated regions that become accessible after neural crest migration are co-enriched for Sox9 and Fox transcription factor binding motifs. In zebrafish lacking Foxc1 paralogs, we find a global decrease in chromatin accessibility in chondrocytes, consistent with a later loss of dorsal facial cartilages. Zebrafish transgenesis assays confirm that many of these Foxc1-dependent elements function as enhancers with region- and stage-specific activity in facial cartilages. These results show that Foxc1 promotes chondrogenesis in the face by establishing chromatin accessibility at a number of cartilage-associated gene enhancers.

Keywords:  chromosomes; developmental biology; gene expression; zebrafish

DOI:  https://doi.org/10.7554/eLife.63595
PLoS One. 2020 ;15(12): e0243791

PEREGRINE: A genome-wide prediction of enhancer to gene relationships supported by experimental evidence.

Caitlin Mills, Anushya Muruganujan, Dustin Ebert, Crystal N Marconett, Juan Pablo Lewinger, Paul D Thomas, Huaiyu Mi.

Enhancers are powerful and versatile agents of cell-type specific gene regulation, which are thought to play key roles in human disease. Enhancers are short DNA elements that function primarily as clusters of transcription factor binding sites that are spatially coordinated to regulate expression of one or more specific target genes. These regulatory connections between enhancers and target genes can therefore be characterized as enhancer-gene links that can affect development, disease, and homeostatic cellular processes. Despite their implication in disease and the establishment of cell identity during development, most enhancer-gene links remain unknown. Here we introduce a new, publicly accessible database of predicted enhancer-gene links, PEREGRINE. The PEREGRINE human enhancer-gene links interactive web interface incorporates publicly available experimental data from ChIA-PET, eQTL, and Hi-C assays across 78 cell and tissue types to link 449,627 enhancers to 17,643 protein-coding genes. These enhancer-gene links are made available through the new Enhancer module of the PANTHER database and website where the user may easily access the evidence for each enhancer-gene link, as well as query by target gene and enhancer location.

DOI: https://doi.org/10.1371/journal.pone.0243791
Cell. 2021 Jan 18. pii: S0092-8674(20)31754-2. [Epub ahead of print]

Changes in genome architecture and transcriptional dynamics progress independently of sensory experience during post-natal brain development.

Longzhi Tan, Wenping Ma, Honggui Wu, Yinghui Zheng, Dong Xing, Ritchie Chen, Xiang Li, Nicholas Daley, Karl Deisseroth, X Sunney Xie.

  Both transcription and three-dimensional (3D) architecture of the mammalian genome play critical roles in neurodevelopment and its disorders. However, 3D genome structures of single brain cells have not been solved; little is known about the dynamics of single-cell transcriptome and 3D genome after birth. Here, we generated a transcriptome (3,517 cells) and 3D genome (3,646 cells) atlas of the developing mouse cortex and hippocampus by using our high-resolution multiple annealing and looping-based amplification cycles for digital transcriptomics (MALBAC-DT) and diploid chromatin conformation capture (Dip-C) methods and developing multi-omic analysis pipelines. In adults, 3D genome "structure types" delineate all major cell types, with high correlation between chromatin A/B compartments and gene expression. During development, both transcriptome and 3D genome are extensively transformed in the first post-natal month. In neurons, 3D genome is rewired across scales, correlated with gene expression modules, and independent of sensory experience. Finally, we examine allele-specific structure of imprinted genes, revealing local and chromosome (chr)-wide differences. These findings uncover an unknown dimension of neurodevelopment.

Keywords:  chromatin folding; developmental biology; epigenetics of plasticity; epigenomics; higher-order chromatin structure; molecular modeling; molecular psychiatry; neurogenesis; single-cell transcriptomics; structural biology

DOI:  https://doi.org/10.1016/j.cell.2020.12.032
Nat Commun. 2021 01 25. 12(1): 567

Conserved regulatory logic at accessible and inaccessible chromatin during the acute inflammatory response in mammals.

Azad Alizada, Nadiya Khyzha, Liangxi Wang, Lina Antounians, Xiaoting Chen, Melvin Khor, Minggao Liang, Kumaragurubaran Rathnakumar, Matthew T Weirauch, Alejandra Medina-Rivera, Jason E Fish, Michael D Wilson.

The regulatory elements controlling gene expression during acute inflammation are not fully elucidated. Here we report the identification of a set of NF-κB-bound elements and common chromatin landscapes underlying the acute inflammatory response across cell-types and mammalian species. Using primary vascular endothelial cells (human/mouse/bovine) treated with the pro-inflammatory cytokine, Tumor Necrosis Factor-α, we identify extensive (~30%) conserved orthologous binding of NF-κB to accessible, as well as nucleosome-occluded chromatin. Regions with the highest NF-κB occupancy pre-stimulation show dramatic increases in NF-κB binding and chromatin accessibility post-stimulation. These 'pre-bound' regions are typically conserved (~56%), contain multiple NF-κB motifs, are utilized by diverse cell types, and overlap rare non-coding mutations and common genetic variation associated with both inflammatory and cardiovascular phenotypes. Genetic ablation of conserved, 'pre-bound' NF-κB regions within the super-enhancer associated with the chemokine-encoding CCL2 gene and elsewhere supports the functional relevance of these elements.

DOI: https://doi.org/10.1038/s41467-020-20765-1
Mol Syst Biol. 2021 Jan;17(1): e9873

Transcriptionally active enhancers in human cancer cells.

Katja Lidschreiber, Lisa A Jung, Henrik von der Emde, Kashyap Dave, Jussi Taipale, Patrick Cramer, Michael Lidschreiber.

  The growth of human cancer cells is driven by aberrant enhancer and gene transcription activity. Here, we use transient transcriptome sequencing (TT-seq) to map thousands of transcriptionally active putative enhancers in fourteen human cancer cell lines covering seven types of cancer. These enhancers were associated with cell type-specific gene expression, enriched for genetic variants that predispose to cancer, and included functionally verified enhancers. Enhancer-promoter (E-P) pairing by correlation of transcription activity revealed ~ 40,000 putative E-P pairs, which were depleted for housekeeping genes and enriched for transcription factors, cancer-associated genes, and 3D conformational proximity. The cell type specificity and transcription activity of target genes increased with the number of paired putative enhancers. Our results represent a rich resource for future studies of gene regulation by enhancers and their role in driving cancerous cell growth.

Keywords:  TT-seq; cancer; eRNAs; enhancers; transcription

DOI:  https://doi.org/10.15252/msb.20209873
Nucleic Acids Res. 2021 Jan 28. pii: gkab009. [Epub ahead of print]

Single cell epigenetic visualization assay.

Sam Kint, Wim Van Criekinge, Linos Vandekerckhove, Winnok H De Vos, Karol Bomsztyk, Diane S Krause, Oleg Denisenko.

Characterization of the epigenetic status of individual cells remains a challenge. Current sequencing approaches have limited coverage, and it is difficult to assign an epigenetic status to the transcription state of individual gene alleles in the same cell. To address these limitations, a targeted microscopy-based epigenetic visualization assay (EVA) was developed for detection and quantification of epigenetic marks at genes of interest in single cells. The assay is based on an in situ biochemical reaction between an antibody-conjugated alkaline phosphatase bound to the epigenetic mark of interest, and a 5'-phosphorylated fluorophore-labeled DNA oligo tethered to a target gene by gene-specific oligonucleotides. When the epigenetic mark is present at the gene, phosphate group removal by the phosphatase protects the oligo from λ-exonuclease activity providing a quantitative fluorescent readout. We applied EVA to measure 5-methylcytosine (5mC) and H3K9Ac levels at different genes and the HIV-1 provirus in human cell lines. To link epigenetic marks to gene transcription, EVA was combined with RNA-FISH. Higher 5mC levels at the silenced compared to transcribed XIST gene alleles in female somatic cells validated this approach and demonstrated that EVA can be used to relate epigenetic marks to the transcription status of individual gene alleles.

DOI: https://doi.org/10.1093/nar/gkab009
Proc Natl Acad Sci U S A. 2021 Feb 02. pii: e2023347118. [Epub ahead of print]118(5):

DNA methylation-linked chromatin accessibility affects genomic architecture in Arabidopsis.

Zhenhui Zhong, Suhua Feng, Sascha H Duttke, Magdalena E Potok, Yiwei Zhang, Javier Gallego-Bartolomé, Wanlu Liu, Steven E Jacobsen.

  DNA methylation is a major epigenetic modification found across species and has a profound impact on many biological processes. However, its influence on chromatin accessibility and higher-order genome organization remains unclear, particularly in plants. Here, we present genome-wide chromatin accessibility profiles of 18 Arabidopsis mutants that are deficient in CG, CHG, or CHH DNA methylation. We find that DNA methylation in all three sequence contexts impacts chromatin accessibility in heterochromatin. Many chromatin regions maintain inaccessibility when DNA methylation is lost in only one or two sequence contexts, and signatures of accessibility are particularly affected when DNA methylation is reduced in all contexts, suggesting an interplay between different types of DNA methylation. In addition, we found that increased chromatin accessibility was not always accompanied by increased transcription, suggesting that DNA methylation can directly impact chromatin structure by other mechanisms. We also observed that an increase in chromatin accessibility was accompanied by enhanced long-range chromatin interactions. Together, these results provide a valuable resource for chromatin architecture and DNA methylation analyses and uncover a pivotal role for methylation in the maintenance of heterochromatin inaccessibility.

Keywords:  DNA methylation; chromatin accessibility; epigenetics

DOI:  https://doi.org/10.1073/pnas.2023347118
Comput Struct Biotechnol J. 2021 ;19 355-362

FIREcaller: Detecting frequently interacting regions from Hi-C data.

Cheynna Crowley, Yuchen Yang, Yunjiang Qiu, Benxia Hu, Armen Abnousi, Jakub Lipiński, Dariusz Plewczyński, Di Wu, Hyejung Won, Bing Ren, Ming Hu, Yun Li.

  Hi-C experiments have been widely adopted to study chromatin spatial organization, which plays an essential role in genome function. We have recently identified frequently interacting regions (FIREs) and found that they are closely associated with cell-type-specific gene regulation. However, computational tools for detecting FIREs from Hi-C data are still lacking. In this work, we present FIREcaller, a stand-alone, user-friendly R package for detecting FIREs from Hi-C data. FIREcaller takes raw Hi-C contact matrices as input, performs within-sample and cross-sample normalization, and outputs continuous FIRE scores, dichotomous FIREs, and super-FIREs. Applying FIREcaller to Hi-C data from various human tissues, we demonstrate that FIREs and super-FIREs identified, in a tissue-specific manner, are closely related to gene regulation, are enriched for enhancer-promoter (E-P) interactions, tend to overlap with regions exhibiting epigenomic signatures of cis-regulatory roles, and aid the interpretation or GWAS variants. The FIREcaller package is implemented in R and freely available at https://yunliweb.its.unc.edu/FIREcaller.

Keywords:  Chromatin spatial organization; Frequently Interacting Regions (FIREs); Hi-C

DOI:  https://doi.org/10.1016/j.csbj.2020.12.026
Nat Commun. 2021 Jan 29. 12(1): 694

De novo DNA methyltransferase activity in colorectal cancer is directed towards H3K36me3 marked CpG islands.

Roza H Ali Masalmeh, Francesca Taglini, Cristina Rubio-Ramon, Kamila I Musialik, Jonathan Higham, Hazel Davidson-Smith, Ioannis Kafetzopoulos, Kamila P Pawlicka, Hannah M Finan, Richard Clark, Jimi Wills, Andrew J Finch, Lee Murphy, Duncan Sproul.

The aberrant gain of DNA methylation at CpG islands is frequently observed in colorectal tumours and may silence the expression of tumour suppressors such as MLH1. Current models propose that these CpG islands are targeted by de novo DNA methyltransferases in a sequence-specific manner, but this has not been tested. Using ectopically integrated CpG islands, here we find that aberrantly methylated CpG islands are subject to low levels of de novo DNA methylation activity in colorectal cancer cells. By delineating DNA methyltransferase targets, we find that instead de novo DNA methylation activity is targeted primarily to CpG islands marked by the histone modification H3K36me3, a mark associated with transcriptional elongation. These H3K36me3 marked CpG islands are heavily methylated in colorectal tumours and the normal colon suggesting that de novo DNA methyltransferase activity at CpG islands in colorectal cancer is focused on similar targets to normal tissues and not greatly remodelled by tumourigenesis.

DOI: https://doi.org/10.1038/s41467-020-20716-w
Nat Commun. 2021 Jan 29. 12(1): 719

H3K27me3-rich genomic regions can function as silencers to repress gene expression via chromatin interactions.

Yichao Cai, Ying Zhang, Yan Ping Loh, Jia Qi Tng, Mei Chee Lim, Zhendong Cao, Anandhkumar Raju, Erez Lieberman Aiden, Shang Li, Lakshmanan Manikandan, Vinay Tergaonkar, Greg Tucker-Kellogg, Melissa Jane Fullwood.

The mechanisms underlying gene repression and silencers are poorly understood. Here we investigate the hypothesis that H3K27me3-rich regions of the genome, defined from clusters of H3K27me3 peaks, may be used to identify silencers that can regulate gene expression via proximity or looping. We find that H3K27me3-rich regions are associated with chromatin interactions and interact preferentially with each other. H3K27me3-rich regions component removal at interaction anchors by CRISPR leads to upregulation of interacting target genes, altered H3K27me3 and H3K27ac levels at interacting regions, and altered chromatin interactions. Chromatin interactions did not change at regions with high H3K27me3, but regions with low H3K27me3 and high H3K27ac levels showed changes in chromatin interactions. Cells with H3K27me3-rich regions knockout also show changes in phenotype associated with cell identity, and altered xenograft tumor growth. Finally, we observe that H3K27me3-rich regions-associated genes and long-range chromatin interactions are susceptible to H3K27me3 depletion. Our results characterize H3K27me3-rich regions and their mechanisms of functioning via looping.

DOI: https://doi.org/10.1038/s41467-021-20940-y
iScience. 2021 Jan 22. 24(1): 101989

Brd2/4 and Myc regulate alternative cell lineage programmes during early osteoclast differentiation in vitro.

Valentina S Caputo, Nikolaos Trasanidis, Xiaolin Xiao, Mark E Robinson, Alexia Katsarou, Kanagaraju Ponnusamy, Rab K Prinjha, Nicholas Smithers, Aristeidis Chaidos, Holger W Auner, Anastasios Karadimitris.

  Osteoclast (OC) development in response to nuclear factor kappa-Β ligand (RANKL) is critical for bone homeostasis in health and in disease. The early and direct chromatin regulatory changes imparted by the BET chromatin readers Brd2-4 and OC-affiliated transcription factors (TFs) during osteoclastogenesis are not known. Here, we demonstrate that in response to RANKL, early OC development entails regulation of two alternative cell fate transcriptional programmes, OC vs macrophage, with repression of the latter following activation of the former. Both programmes are regulated in a non-redundant manner by increased chromatin binding of Brd2 at promoters and of Brd4 at enhancers/super-enhancers. Myc, the top RANKL-induced TF, regulates OC development in co-operation with Brd2/4 and Max and by establishing negative and positive regulatory loops with other lineage-affiliated TFs. These insights into the transcriptional regulation of osteoclastogenesis suggest the clinical potential of selective targeting of Brd2/4 to abrogate pathological OC activation.

Keywords:  Bioinformatics; Biological Sciences; Developmental Biology; Omics; Transcriptomics

DOI:  https://doi.org/10.1016/j.isci.2020.101989
Dev Dyn. 2021 Jan 26.

Hox13-Mediated Dbx2 Regulation In Limbs Suggests Inter-Tad Sharing Of Enhancers.

Leonardo Beccari, Gabriel Jaquier, Lucille Lopez-Delisle, Eddie Rodriguez-Carballo, Bénédicte Mascrez, Sandra Gitto, Joost Woltering, Denis Duboule.

   BACKGROUND: During tetrapod limb development, the HOXA13 and HOXD13 transcription factors are critical for the emergence and organization of the autopod, the most distal aspect where digits will develop. Since previous work had suggested that the Dbx2 gene is a target of these factors, we set up to analyze in detail this potential regulatory interaction.
RESULTS: We show that HOX13 proteins bind to mammalian-specific sequences at the vicinity of the Dbx2 locus that have enhancer activity in developing digits. However, the functional inactivation of the DBX2 protein did not elicit any particular phenotype related to Hox genes inactivation in digits, suggesting either redundant or compensatory mechanisms. We report that the neighboring Nell2 and Ano6 genes are also expressed in distal limb buds and are in part controlled by the same Dbx2 enhancers despite being localized into two different topologically associating domains (TADs) flanking the Dbx2 locus.
CONCLUSIONS: We conclude that Hoxa13 and Hoxd genes cooperatively activate Dbx2 expression in developing digits through binding to mammalian specific regulatory sequences in the Dbx2 neighborhood. Furthermore, these enhancers can overcome TAD boundaries in either direction to co-regulate a set of genes located in distinct chromatin domains. This article is protected by copyright. All rights reserved.

Keywords:  Hox; TAD boundary; chromatin architecture; digit development; gene regulation

DOI:  https://doi.org/10.1002/dvdy.303
Elife. 2021 Jan 25. pii: e61894. [Epub ahead of print]10

Epigenetic reprogramming rewires transcription during the alternation of generations in Arabidopsis.

Michael Borg, Ranjith K Papareddy, Rodolphe Dombey, Elin Axelsson, Michael D Nodine, David Twell, Frédéric Berger.

  Alternation between morphologically distinct haploid and diploid life forms is a defining feature of most plant and algal life cycles, yet the underlying molecular mechanisms that govern these transitions remain unclear. Here, we explore the dynamic relationship between chromatin accessibility and epigenetic modifications during life form transitions in Arabidopsis. The diploid-to-haploid life form transition is governed by the loss of H3K9me2 and DNA demethylation of transposon-associated cis-regulatory elements. This event is associated with dramatic changes in chromatin accessibility and transcriptional reprogramming. In contrast, the global loss of H3K27me3 in the haploid form shapes a chromatin accessibility landscape that is poised to re-initiate the transition back to diploid life after fertilization. Hence, distinct epigenetic reprogramming events rewire transcription through major reorganization of the regulatory epigenome to guide the alternation of generations in flowering plants.

Keywords:  A. thaliana; developmental biology; plant biology

DOI:  https://doi.org/10.7554/eLife.61894
Nat Commun. 2021 01 27. 12(1): 618

Subtraction-free and bisulfite-free specific sequencing of 5-methylcytosine and its oxidized derivatives at base resolution.

Yibin Liu, Zhiyuan Hu, Jingfei Cheng, Paulina Siejka-Zielińska, Jinfeng Chen, Masato Inoue, Ahmed Ashour Ahmed, Chun-Xiao Song.

Although various methods have been developed for sequencing cytosine modifications, it is still challenging for specific and quantitative sequencing of individual modification at base-resolution. For example, to obtain both true 5-methylcytosine (5mC) and true 5-hydroxymethylcytosine (5hmC) information, the two major epigenetic modifications, it usually requires subtraction of two methods, which increases noise and requires high sequencing depth. Recently, we developed TET-assisted pyridine borane sequencing (TAPS) for bisulfite-free direct sequencing of 5mC and 5hmC. Here we demonstrate that two sister methods, TAPSβ and chemical-assisted pyridine borane sequencing (CAPS), can be effectively used for subtraction-free and specific whole-genome sequencing of 5mC and 5hmC, respectively. We also demonstrate pyridine borane sequencing (PS) for whole-genome profiling of 5-formylcytosine and 5-carboxylcytosine, the further oxidized derivatives of 5mC and 5hmC. This work completes the set of versatile borane reduction chemistry-based methods as a comprehensive toolkit for direct and quantitative sequencing of all four cytosine epigenetic modifications.

DOI: https://doi.org/10.1038/s41467-021-20920-2
Nat Commun. 2021 01 28. 12(1): 652

Single-cell transcriptomic reveals molecular diversity and developmental heterogeneity of human stem cell-derived oligodendrocyte lineage cells.

Xitiz Chamling, Alyssa Kallman, Weixiang Fang, Cynthia A Berlinicke, Joseph L Mertz, Prajwal Devkota, Itzy E Morales Pantoja, Matthew D Smith, Zhicheng Ji, Calvin Chang, Aniruddha Kaushik, Liben Chen, Katharine A Whartenby, Peter A Calabresi, Hai-Quan Mao, Hongkai Ji, Tza-Huei Wang, Donald J Zack.

Injury and loss of oligodendrocytes can cause demyelinating diseases such as multiple sclerosis. To improve our understanding of human oligodendrocyte development, which could facilitate development of remyelination-based treatment strategies, here we describe time-course single-cell-transcriptomic analysis of developing human stem cell-derived oligodendrocyte-lineage-cells (hOLLCs). The study includes hOLLCs derived from both genome engineered embryonic stem cell (ESC) reporter cells containing an Identification-and-Purification tag driven by the endogenous PDGFRα promoter and from unmodified induced pluripotent (iPS) cells. Our analysis uncovers substantial transcriptional heterogeneity of PDGFRα-lineage hOLLCs. We discover sub-populations of human oligodendrocyte progenitor cells (hOPCs) including a potential cytokine-responsive hOPC subset, and identify candidate regulatory genes/networks that define the identity of these sub-populations. Pseudotime trajectory analysis defines developmental pathways of oligodendrocytes vs astrocytes from PDGFRα-expressing hOPCs and predicts differentially expressed genes between the two lineages. In addition, pathway enrichment analysis followed by pharmacological intervention of these pathways confirm that mTOR and cholesterol biosynthesis signaling pathways are involved in maturation of oligodendrocytes from hOPCs.

DOI: https://doi.org/10.1038/s41467-021-20892-3
Plant Commun. 2021 Jan 11. 2(1): 100140

Accessible chromatin regions and their functional interrelations with gene transcription and epigenetic modifications in sorghum genome.

Chao Zhou, Zhu Yuan, Xueping Ma, Huilan Yang, Ping Wang, Lanlan Zheng, Yonghong Zhang, Xiaoyun Liu.

  Accessible chromatin regions (ACRs) provide physical scaffolds to recruit transcriptional co-regulators and displace their nearby nucleosomes in multiple plant species. Characterization of ACRs and investigation of their biological effects in Sorghum bicolor has lagged behind. Regulation of gene expression relies on the transcriptional co-regulators that are recruited to ACRs to affect epigenomic modifications of surrounding nucleosomes. In this study, we employed transposase-accessible chromatin sequencing to identify ACRs and decipher how the presence of ACRs affects gene expression and epigenetic signatures in the Sorghum genome. As a result, 21 077 ACRs, which are mapped to 22.9% of genes and 2.7% of repeats, were identified. The profiling of ACRs on gene structures reveals a narrow and sharp peak around the transcription start site, with relatively weak and broad signals covering the entire gene body and an explicit but wide peak from the transcription termination site to its downstream regions. We discovered that the correlations between gene expression levels and profiled ACR densities are dependent on the positions of ACRs. The occurrence of genic ACRs cumulatively enhances the transcriptional activity of intergenic ACR-associated genes. In addition, an intricate crosstalk among ACRs, gene expression, and epigenetic marks has been unveiled by integrating multiple-omics analyses of whole-genome bisulfite sequencing, 6mA immunoprecipitation followed by sequencing, RNA sequencing, chromatin immunoprecipitation sequencing, and DNase I hypersensitive sites sequencing datasets. Our study provides a genome-wide landscape of ACRs in sorghum, decrypts their interrelations with various epigenetic marks, and sheds new light on their roles in transcriptional regulation.

Keywords:  Sorghum bicolor; accessible chromatin regions; epigenetic mark; transcriptional regulation

DOI:  https://doi.org/10.1016/j.xplc.2020.100140
Cancer Res. 2021 Jan 26. pii: canres.3020.2019. [Epub ahead of print]

Serine biosynthesis is a metabolic vulnerability in IDH2-driven breast cancer progression.

Georgina D Barnabas, Joo Sang Lee, Tamar Shami, Michal Harel, Lir Beck, Michael Selitrennik, Livnat Jerby-Arnon, Neta Erez, Eytan Ruppin, Tamar Geiger.

Cancer-specific metabolic phenotypes and their vulnerabilities represent a viable area of cancer research. In this study, we explored the association of breast cancer subtypes with different metabolic phenotypes and identified isocitrate dehydrogenase 2 (IDH2) as a key player in triple-negative breast cancer (TNBC) and HER2. Functional assays combined with mass spectrometry-based analyses revealed the oncogenic role of IDH2 in cell proliferation, anchorage-independent growth, glycolysis, mitochondrial respiration, and antioxidant defense. Genome-scale metabolic modeling identified PHGDH and PSAT1 as the synthetic dosage lethal (SDL) partners of IDH2. In agreement, CRISPR-Cas9 knockout of PHGDH and PSAT1 showed the essentiality of serine biosynthesis proteins in IDH2-high cells. The clinical significance of the SDL interaction was supported by patients with IDH2-high/PHGDH-low tumors, who exhibited longer survival than patients with IDH2-high/PHGDH-high tumors. Furthermore, PHGDH inhibitors were effective in treating IDH2-high cells in vitro and in vivo. Altogether, our study creates a new link between two known cancer regulators and emphasizes PHGDH as a promising target for TNBC with IDH2 overexpression.

DOI: https://doi.org/10.1158/0008-5472.CAN-19-3020
PLoS Genet. 2021 Jan 29. 17(1): e1008540

MED19 alters AR occupancy and gene expression in prostate cancer cells, driving MAOA expression and growth under low androgen.

Hannah Weber, Rachel Ruoff, Michael J Garabedian.

Androgen deprivation therapy (ADT) is a mainstay of prostate cancer treatment, given the dependence of prostate cells on androgen and the androgen receptor (AR). However, tumors become ADT-resistant, and there is a need to understand the mechanism. One possible mechanism is the upregulation of AR co-regulators, although only a handful have been definitively linked to disease. We previously identified the Mediator subunit MED19 as an AR co-regulator, and reported that MED19 depletion inhibits AR transcriptional activity and growth of androgen-insensitive LNCaP-abl cells. Therefore, we proposed that MED19 upregulation would promote AR activity and drive androgen-independent growth. Here, we show that stable overexpression of MED19 in androgen-dependent LNCaP cells promotes growth under conditions of androgen deprivation. To delineate the mechanism, we determined the MED19 and AR transcriptomes and cistromes in control and MED19-overexpressing LNCaP cells. We also examined genome-wide H3K27 acetylation. MED19 overexpression selectively alters AR occupancy, H3K27 acetylation, and gene expression. Under conditions of androgen deprivation, genes regulated by MED19 correspond to genes regulated by ELK1, a transcription factor that binds the AR N-terminus to induce select AR target gene expression and proliferation, and genomic sites occupied by MED19 and AR are enriched for motifs associated with ELK1. Strikingly, MED19 upregulates expression of monoamine oxidase A (MAOA), a factor that promotes prostate cancer growth. MAOA depletion reduces androgen-independent growth. MED19 and AR occupy the MAOA promoter, with MED19 overexpression enhancing AR occupancy and H3K27 acetylation. Furthermore, MED19 overexpression increases ELK1 occupancy at the MAOA promoter, and ELK1 depletion reduces MAOA expression and androgen-independent growth. This suggests that MED19 cooperates with ELK1 to regulate AR occupancy and H3K27 acetylation at MAOA, upregulating its expression and driving androgen independence in prostate cancer cells. This study provides important insight into the mechanisms of prostate cancer cell growth under low androgen, and underscores the importance of the MED19-MAOA axis in this process.

DOI: https://doi.org/10.1371/journal.pgen.1008540
EMBO Rep. 2021 Jan 29. e51009

Succinylation of H3K122 destabilizes nucleosomes and enhances transcription.

Lara Zorro Shahidian, Mariska Haas, Stephanie Le Gras, Sandra Nitsch, André Mourão, Arie Geerlof, Raphael Margueron, Jens Michaelis, Sylvain Daujat, Robert Schneider.

  Histone post-translational modifications (PTMs) are key players in chromatin regulation. The identification of novel histone acylations raises important questions regarding their role in transcription. In this study, we characterize the role of an acylation on the lateral surface of the histone octamer, H3K122 succinylation (H3K122succ), in chromatin function and transcription. Using chromatin succinylated at H3K122 in in vitro transcription assays, we show that the presence of H3K122succ is sufficient to stimulate transcription. In line with this, we found in our ChIP assays H3K122succ enriched on promoters of active genes and H3K122succ enrichment scaling with gene expression levels. Furthermore, we show that the co-activators p300/CBP can succinylate H3K122 and identify sirtuin 5 (SIRT5) as a new desuccinylase. By applying single molecule FRET assays, we demonstrate a direct effect of H3K122succ on nucleosome stability, indicating an important role for histone succinylation in modulating chromatin dynamics. Together, these data provide the first insights into the mechanisms underlying transcriptional regulation by H3K122succ.

Keywords:  acylation; histones; succinylation

DOI:  https://doi.org/10.15252/embr.202051009
Nat Commun. 2021 01 25. 12(1): 560

Epithelial expression of Gata4 and Sox2 regulates specification of the squamous-columnar junction via MAPK/ERK signaling in mice.

Nao Sankoda, Wataru Tanabe, Akito Tanaka, Hirofumi Shibata, Knut Woltjen, Tsutomu Chiba, Hironori Haga, Yoshiharu Sakai, Masaki Mandai, Takuya Yamamoto, Yasuhiro Yamada, Shinji Uemoto, Yoshiya Kawaguchi.

The squamous-columnar junction (SCJ) is a boundary consisting of precisely positioned transitional epithelium between the squamous and columnar epithelium. Transitional epithelium is a hotspot for precancerous lesions, and is therefore clinically important; however, the origins and physiological properties of transitional epithelium have not been fully elucidated. Here, by using mouse genetics, lineage tracing, and organoid culture, we examine the development of the SCJ in the mouse stomach, and thus define the unique features of transitional epithelium. We find that two transcription factors, encoded by Sox2 and Gata4, specify primitive transitional epithelium into squamous and columnar epithelium. The proximal-distal segregation of Sox2 and Gata4 expression establishes the boundary of the unspecified transitional epithelium between committed squamous and columnar epithelium. Mechanistically, Gata4-mediated expression of the morphogen Fgf10 in the distal stomach and Sox2-mediated Fgfr2 expression in the proximal stomach induce the intermediate regional activation of MAPK/ERK, which prevents the differentiation of transitional epithelial cells within the SCJ boundary. Our results have implications for tissue regeneration and tumorigenesis, which are related to the SCJ.

DOI: https://doi.org/10.1038/s41467-021-20906-0
Nat Commun. 2021 01 28. 12(1): 651

Dynamics of genome architecture and chromatin function during human B cell differentiation and neoplastic transformation.

Roser Vilarrasa-Blasi, Paula Soler-Vila, Núria Verdaguer-Dot, Núria Russiñol, Marco Di Stefano, Vicente Chapaprieta, Guillem Clot, Irene Farabella, Pol Cuscó, Marta Kulis, Xabier Agirre, Felipe Prosper, Renée Beekman, Silvia Beà, Dolors Colomer, Hendrik G Stunnenberg, Ivo Gut, Elias Campo, Marc A Marti-Renom, José Ignacio Martin-Subero.

To investigate the three-dimensional (3D) genome architecture across normal B cell differentiation and in neoplastic cells from different subtypes of chronic lymphocytic leukemia and mantle cell lymphoma patients, here we integrate in situ Hi-C and nine additional omics layers. Beyond conventional active (A) and inactive (B) compartments, we uncover a highly-dynamic intermediate compartment enriched in poised and polycomb-repressed chromatin. During B cell development, 28% of the compartments change, mostly involving a widespread chromatin activation from naive to germinal center B cells and a reversal to the naive state upon further maturation into memory B cells. B cell neoplasms are characterized by both entity and subtype-specific alterations in 3D genome organization, including large chromatin blocks spanning key disease-specific genes. This study indicates that 3D genome interactions are extensively modulated during normal B cell differentiation and that the genome of B cell neoplasias acquires a tumor-specific 3D genome architecture.

DOI: https://doi.org/10.1038/s41467-020-20849-y
Genome Biol. 2021 Jan 26. 22(1): 47

CRISPRi enables isoform-specific loss-of-function screens and identification of gastric cancer-specific isoform dependencies.

Rebecca Davies, Ling Liu, Sheng Taotao, Natasha Tuano, Richa Chaturvedi, Kie Kyon Huang, Catherine Itman, Amit Mandoli, Aditi Qamra, Changyuan Hu, David Powell, Roger J Daly, Patrick Tan, Joseph Rosenbluh.

INTRODUCTION: Genes contain multiple promoters that can drive the expression of various transcript isoforms. Although transcript isoforms from the same gene could have diverse and non-overlapping functions, current loss-of-function methodologies are not able to differentiate between isoform-specific phenotypes.
RESULTS: Here, we show that CRISPR interference (CRISPRi) can be adopted for targeting specific promoters within a gene, enabling isoform-specific loss-of-function genetic screens. We use this strategy to test functional dependencies of 820 transcript isoforms that are gained in gastric cancer (GC). We identify a subset of GC-gained transcript isoform dependencies, and of these, we validate CIT kinase as a novel GC dependency. We further show that some genes express isoforms with opposite functions. Specifically, we find that the tumour suppressor ZFHX3 expresses an isoform that has a paradoxical oncogenic role that correlates with poor patient outcome.
CONCLUSIONS: Our work finds isoform-specific phenotypes that would not be identified using current loss-of-function approaches that are not designed to target specific transcript isoforms.

DOI: https://doi.org/10.1186/s13059-021-02266-6
J Biol Chem. 2020 Apr 17. pii: S0021-9258(17)48561-9. [Epub ahead of print]295(16): 5449-5460

The transcriptional regulator MEIS2 sets up the ground state for palatal osteogenesis in mice.

Linyan Wang, Qinghuang Tang, Jue Xu, Hua Li, Tianfang Yang, Liwen Li, Ondrej Machon, Tao Hu, YiPing Chen.

  Haploinsufficiency of Meis homeobox 2 (MEIS2), encoding a transcriptional regulator, is associated with human cleft palate, and Meis2 inactivation leads to abnormal palate development in mice, implicating MEIS2 functions in palate development. However, its functional mechanisms remain unknown. Here we observed widespread MEIS2 expression in the developing palate in mice. Wnt1Cre-mediated Meis2 inactivation in cranial neural crest cells led to a secondary palate cleft. Importantly, about half of the Wnt1Cre;Meis2f/f mice exhibited a submucous cleft, providing a model for studying palatal bone formation and patterning. Consistent with complete absence of palatal bones, the results from integrative analyses of MEIS2 by ChIP sequencing, RNA-Seq, and an assay for transposase-accessible chromatin sequencing identified key osteogenic genes regulated directly by MEIS2, indicating that it plays a fundamental role in palatal osteogenesis. De novo motif analysis uncovered that the MEIS2-bound regions are highly enriched in binding motifs for several key osteogenic transcription factors, particularly short stature homeobox 2 (SHOX2). Comparative ChIP sequencing analyses revealed genome-wide co-occupancy of MEIS2 and SHOX2 in addition to their colocalization in the developing palate and physical interaction, suggesting that SHOX2 and MEIS2 functionally interact. However, although SHOX2 was required for proper palatal bone formation and was a direct downstream target of MEIS2, Shox2 overexpression failed to rescue the palatal bone defects in a Meis2-mutant background. These results, together with the fact that Meis2 expression is associated with high osteogenic potential and required for chromatin accessibility of osteogenic genes, support a vital function of MEIS2 in setting up a ground state for palatal osteogenesis.

Keywords:  Meis homeobox 2 (MEIS2); bone; chromatin accessibility; craniofacial development; gene knockout; gene regulation; osteogenesis; palatal development; short stature homeobox 2 (SHOX2); transcription; transcription factor; transgenic mice

DOI:  https://doi.org/10.1074/jbc.RA120.012684
Nat Commun. 2021 01 27. 12(1): 606

TALEN outperforms Cas9 in editing heterochromatin target sites.

Surbhi Jain, Saurabh Shukla, Che Yang, Meng Zhang, Zia Fatma, Manasi Lingamaneni, Shireen Abesteh, Stephan Thomas Lane, Xiong Xiong, Yuchuan Wang, Charles M Schroeder, Paul R Selvin, Huimin Zhao.

Genome editing critically relies on selective recognition of target sites. However, despite recent progress, the underlying search mechanism of genome-editing proteins is not fully understood in the context of cellular chromatin environments. Here, we use single-molecule imaging in live cells to directly study the behavior of CRISPR/Cas9 and TALEN. Our single-molecule imaging of genome-editing proteins reveals that Cas9 is less efficient in heterochromatin than TALEN because Cas9 becomes encumbered by local searches on non-specific sites in these regions. We find up to a fivefold increase in editing efficiency for TALEN compared to Cas9 in heterochromatin regions. Overall, our results show that Cas9 and TALEN use a combination of 3-D and local searches to identify target sites, and the nanoscopic granularity of local search determines the editing outcomes of the genome-editing proteins. Taken together, our results suggest that TALEN is a more efficient gene-editing tool than Cas9 for applications in heterochromatin.

DOI: https://doi.org/10.1038/s41467-020-20672-5
Cell. 2021 Jan 22. pii: S0092-8674(21)00001-5. [Epub ahead of print]

3D Genome of macaque fetal brain reveals evolutionary innovations during primate corticogenesis.

Xin Luo, Yuting Liu, Dachang Dang, Ting Hu, Yingping Hou, Xiaoyu Meng, Fengyun Zhang, Tingting Li, Can Wang, Min Li, Haixu Wu, Qiushuo Shen, Yan Hu, Xuerui Zeng, Xiechao He, Lanzhen Yan, Shihua Zhang, Cheng Li, Bing Su.

  Elucidating the regulatory mechanisms of human brain evolution is essential to understanding human cognition and mental disorders. We generated multi-omics profiles and constructed a high-resolution map of 3D genome architecture of rhesus macaque during corticogenesis. By comparing the 3D genomes of human, macaque, and mouse brains, we identified many human-specific chromatin structure changes, including 499 topologically associating domains (TADs) and 1,266 chromatin loops. The human-specific loops are significantly enriched in enhancer-enhancer interactions, and the regulated genes show human-specific expression changes in the subplate, a transient zone of the developing brain critical for neural circuit formation and plasticity. Notably, many human-specific sequence changes are located in the human-specific TAD boundaries and loop anchors, which may generate new transcription factor binding sites and chromatin structures in human. Collectively, the presented data highlight the value of comparative 3D genome analyses in dissecting the regulatory mechanisms of brain development and evolution.

Keywords:  3D genome; EPHA7; TAD; brain; brain evolution; chromatin structure; corticogenesis; loop; macaque; subplate

DOI:  https://doi.org/10.1016/j.cell.2021.01.001
Nat Commun. 2021 01 27. 12(1): 614

IDH1 mutations induce organelle defects via dysregulated phospholipids.

Adrian Lita, Artem Pliss, Andrey Kuzmin, Tomohiro Yamasaki, Lumin Zhang, Tyrone Dowdy, Christina Burks, Natalia de Val, Orieta Celiku, Victor Ruiz-Rodado, Elena-Raluca Nicoli, Michael Kruhlak, Thorkell Andresson, Sudipto Das, Chunzhang Yang, Rebecca Schmitt, Christel Herold-Mende, Mark R Gilbert, Paras N Prasad, Mioara Larion.

Infiltrating gliomas are devastating and incurable tumors. Amongst all gliomas, those harboring a mutation in isocitrate dehydrogenase 1 mutation (IDH1mut) acquire a different tumor biology and clinical manifestation from those that are IDH1WT. Understanding the unique metabolic profile reprogrammed by IDH1 mutation has the potential to identify new molecular targets for glioma therapy. Herein, we uncover increased monounsaturated fatty acids (MUFA) and their phospholipids in endoplasmic reticulum (ER), generated by IDH1 mutation, that are responsible for Golgi and ER dilation. We demonstrate a direct link between the IDH1 mutation and this organelle morphology via D-2HG-induced stearyl-CoA desaturase (SCD) overexpression, the rate-limiting enzyme in MUFA biosynthesis. Inhibition of IDH1 mutation or SCD silencing restores ER and Golgi morphology, while D-2HG and oleic acid induces morphological defects in these organelles. Moreover, addition of oleic acid, which tilts the balance towards elevated levels of MUFA, produces IDH1mut-specific cellular apoptosis. Collectively, these results suggest that IDH1mut-induced SCD overexpression can rearrange the distribution of lipids in the organelles of glioma cells, providing new insight into the link between lipid metabolism and organelle morphology in these cells, with potential and unique therapeutic implications.

DOI: https://doi.org/10.1038/s41467-020-20752-6
J Biol Chem. 2020 Apr 17. pii: S0021-9258(17)48564-4. [Epub ahead of print]295(16): 5484-5495

The FKH domain in FOXP3 mRNA frequently contains mutations in hepatocellular carcinoma that influence the subcellular localization and functions of FOXP3.

Jianwei Ren, Yi Liu, Shanshan Wang, Yu Wang, Wende Li, Siyu Chen, Dexuan Cui, Shengli Yang, Ming-Yue Li, Bo Feng, Paul B S Lai, George G Chen.

  The transcription factor forkhead box P3 (FOXP3) is a biomarker for regulatory T cells and can also be expressed in cancer cells, but its function in cancer appears to be divergent. The role of hepatocyte-expressed FOXP3 in hepatocellular carcinoma (HCC) is unknown. Here, we collected tumor samples and clinical information from 115 HCC patients and used five human cancer cell lines. We examined FOXP3 mRNA sequences for mutations, used a luciferase assay to assess promoter activities of FOXP3's target genes, and employed mouse tumor models to confirm in vitro results. We detected mutations in the FKH domain of FOXP3 mRNAs in 33% of the HCC tumor tissues, but in none of the adjacent nontumor tissues. None of the mutations occurred at high frequency, indicating that they occurred randomly. Notably, the mutations were not detected in the corresponding regions of FOXP3 genomic DNA, and many of them resulted in amino acid substitutions in the FKH region, altering FOXP3's subcellular localization. FOXP3 delocalization from the nucleus to the cytoplasm caused loss of transcriptional regulation of its target genes, inactivated its tumor-inhibitory capability, and changed cellular responses to histone deacetylase (HDAC) inhibitors. More complex FKH mutations appeared to be associated with worse prognosis in HCC patients. We conclude that mutations in the FKH domain of FOXP3 mRNA frequently occur in HCC and that these mutations are caused by errors in transcription and are not derived from genomic DNA mutations. Our results suggest that transcriptional mutagenesis of FOXP3 plays a role in HCC.

Keywords:  FKH domain; forkhead box P3 (FOXP3); gene transcription; hepatocellular carcinoma (HCC); liver cancer; mutagenesis; mutations; signal transduction; subcellular location; suppression; transcription factor; transcriptional mutagenesis; translocation; tumor suppressor

DOI:  https://doi.org/10.1074/jbc.RA120.012518
Blood. 2020 Dec 09. pii: blood.2020005780. [Epub ahead of print]

Dynamic CTCF binding directly mediates interactions among cis-regulatory elements essential for hematopoiesis.

Qian Qi, Li Cheng, Xing Tang, Yanghua He, Yichao Li, Tiffany Yee, Dewan Shrestha, Ruopeng Feng, Peng Xu, Xin Zhou, Shondra M Pruett-Miller, Ross C Hardison, Mitchell J Weiss, Yong Cheng.

While constitutive CTCF-binding sites are needed to maintain relatively invariant chromatin structures, such as topologically associating domains, the precise roles of CTCF to control cell type-specific transcriptional regulation remain poorly explored. We examined CTCF occupancy in different types of primary blood cells derived from the same donor to elucidate a new role for CTCF in gene regulation during blood cell development. We identified dynamic, cell type-specific binding sites for CTCF that colocalize with lineage-specific transcription factors. These dynamic sites are enriched for single nucleotide polymorphisms that are associated with blood cell traits in different linages, and they coincide with the key regulatory elements governing hematopoiesis. CRISPR/Cas9-based perturbation experiments demonstrated that these dynamic CTCF-binding sites play a critical role in red blood cell development. Furthermore, precise deletion of CTCF-binding motifs in dynamic sites abolished interactions of erythroid genes, such as RBM38, with their associated enhancers and led to abnormal erythropoiesis. These results suggest a novel, cell type-specific function for CTCF in which it may serve to facilitate interaction of distal regulatory emblements with target promoters. Our study of the dynamic, cell type-specific binding and function of CTCF provides new insights into transcriptional regulation during hematopoiesis.

DOI: https://doi.org/10.1182/blood.2020005780