bims-rimeca Biomed News
on RNA methylation in cancer
Issue of 2021‒02‒14
eighteen papers selected by
Sk Ramiz Islam
Saha Institute of Nuclear Physics


  1. Ann Transl Med. 2021 Jan;9(1): 59
    Shen S, Yan J, Zhang Y, Dong Z, Xing J, He Y.
      Background: N6-methyladenosine (m6A)-mediated ribonucleic acid (RNA) methylation is considered to be the most significant and abundant epigenetic modification in eukaryotic cells, and plays an essential role in the carcinogenesis and molecular pathogenesis of hepatocellular carcinoma (HCC). However, the relationship between m6A regulation and immune cell infiltration of the tumor immune microenvironment (TIME) has not yet been clarified. We aimed to investigate the roles of m6A RNA gene regulators in HCC immune regulation and prognosis.Methods: The Cancer Genome Atlas (TCGA) database was used, and unsupervised clustering of 21 m6A regulators was performed based on differential gene expression. Gene Set Variation Analysis (GSVA), single-sample Gene Set Enrichment Analysis (ssGSEA), the empirical Bayes method, and m6A scores were used in our analyses.
    Results: Of 433 samples, 101 (23.22%) had m6A regulatory factor mutations. From these, we identified three m6A subtypes, which correlated with different TIME phenotypes: immune rejection, immune infiltration, and immune deficiency. Tumors with low methyltransferase-like 3 (METTL3) expression had increased infiltration of dendritic cells (DCs) in the TIME. Reduced METTL3 expression also led to an overall increase in expression of major histocompatibility complex (MHC) molecules, costimulatory molecules, and adhesion molecules. The m6A subtypes were scored and analyzed for correlations. Patients with epithelial-mesenchymal transition (EMT) subtypes had lower m6A scores than the other three molecular subtypes. Survival analysis found that patients with low m6A scores had better overall survival [hazard ratio (HR) 1.6 (1.1-2.3)] and a 1.16 times better 5-year survival rate than patients with high m6A scores (56% vs. 48%).
    Conclusions: Our results demonstrated that three different m6A modification subtypes contribute to immune regulation in HCC and have potential as novel prognostic indicators and immune therapeutic targets.
    Keywords:  Hepatocellular carcinoma (HCC); N6-methyladenosine (m6A); methyltransferase-like 3 (METTL3); survival; tumor immune microenvironment (TIME)
    DOI:  https://doi.org/10.21037/atm-20-7396
  2. Metabolites. 2021 Jan 30. pii: 80. [Epub ahead of print]11(2):
    Kim J, Lee G.
      Nutrients and metabolic pathways regulate cell growth and cell fate decisions via epigenetic modification of DNA and histones. Another key genetic material, RNA, also contains diverse chemical modifications. Among these, N6-methyladenosine (m6A) is the most prevalent and evolutionarily conserved RNA modification. It functions in various aspects of developmental and disease states, by controlling RNA metabolism, such as stability and translation. Similar to other epigenetic processes, m6A modification is regulated by specific enzymes, including writers (methyltransferases), erasers (demethylases), and readers (m6A-binding proteins). As this is a reversible enzymatic process, metabolites can directly influence the flux of this reaction by serving as substrates and/or allosteric regulators. In this review, we will discuss recent understanding of the regulation of m6A RNA modification by metabolites, nutrients, and cellular metabolic pathways.
    Keywords:  N6-methyladenosine; RNA chemical modification; RNA epitranscriptome; RNA methylation; m6A; metabolic pathways; metabolites; nutrient signaling
    DOI:  https://doi.org/10.3390/metabo11020080
  3. Front Cell Dev Biol. 2020 ;8 616972
    Chen S, Zhang N, Zhang E, Wang T, Jiang L, Wang X, Zheng J.
      The important role of N6-methyladenosine (m6A) RNA methylation regulator in carcinogenesis and progression of clear-cell renal cell carcinoma (ccRCC) is poorly understood by now. In this study, we performed comprehensive analyses of m6A RNA methylation regulators in 975 ccRCC samples and 332 adjacent normal tissues and identified ccRCC-related m6A regulators. Moreover, the m6A diagnostic score based on ccRCC-related m6A regulators could accurately distinguish ccRCC from normal tissue in the Meta-cohort, which was further validated in the independent GSE-cohort and The Cancer Genome Atlas-cohort, with an area under the curve of 0.924, 0.867, and 0.795, respectively. Effective survival prediction of ccRCC by m6A risk score was also identified in the Cancer Genome Atlas training cohort and verified in the testing cohort and the independent GSE22541 cohort, with hazard ratio values of 3.474, 1.679, and 2.101 in the survival prognosis, respectively. The m6A risk score was identified as a risk factor of overall survival in ccRCC patients by the univariate Cox regression analysis, which was further verified in both the training cohort and the independent validation cohort. The integrated nomogram combining m6A risk score and predictable clinicopathologic factors could accurately predict the survival status of the ccRCC patients, with an area under the curve values of 85.2, 82.4, and 78.3% for the overall survival prediction in 1-, 3- and 5-year, respectively. Weighted gene co-expression network analysis with functional enrichment analysis indicated that m6A RNA methylation might affect clinical prognosis through regulating immune functions in patients with ccRCC.
    Keywords:  N6-methyladenosine (m6A); WGCNA; clear cell renal cell carcinoma; nomogram; regulatory immune function
    DOI:  https://doi.org/10.3389/fcell.2020.616972
  4. Life Sci. 2021 Feb 08. pii: S0024-3205(21)00165-X. [Epub ahead of print] 119180
    Zhu K, Li Y, Xu Y.
      AIMS: N6-Methyladenosine (m6A) is the most frequent posttranscriptional modification and plays important roles in tumorigenesis and metastasis. The roles of fat mass and obesity-associated (FTO) in metabolic diseases have been widely explored. However, the molecular mechanisms and physiological functions of FTO in prostate cancer remain largely unknown. This study aimed to explore the exact functions of FTO in the progression of prostate cancer metastasis.MAIN METHODS: Dot blot and m6A RNA methylation quantification assays were performed to determine m6A levels. The protein and mRNA expression levels were detected using immunoblot (IB) and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analyses. Cell invasion and migration abilities were measured using transwell and wound healing assays. Bioinformatics was used to measure the expression level of FTO and possible correlation between FTO levels and advanced tumor stage. Immunofluorescence (IF) was performed to measure the cellular localization of FTO.
    KEY FINDINGS: FTO was downregulated in prostate cancer tissues and cell lines, and the m6A content was increased. Importantly, patients with lower FTO expression had advanced tumor stage and higher Gleason scores. Gain- and loss-of-function assays revealed that FTO inhibits prostate cancer cell invasion and migration in vitro. Moreover, we confirmed that FTO can decrease the total m6A level.
    SIGNIFICANCE: The present study revealed that the FTO m6A demethylase inhibits prostate cancer cell invasion and migration by regulating total m6A levels.
    Keywords:  FTO; Metastasis; N6-methyladenosine; Prostate cancer
    DOI:  https://doi.org/10.1016/j.lfs.2021.119180
  5. Front Oncol. 2020 ;10 623634
    Tian S, Lai J, Yu T, Li Q, Chen Q.
      N6-methyladenosine (m6A), an important RNA modification, is a reversible behavior catalyzed by methyltransferase complexes (m6A "writers"), demethylated transferases (m6A "erasers"), and binding proteins (m6A "readers"). It plays a vital regulatory role in biological functions, involving in a variety of physiological and pathological processes. The level of m6A will affect the RNA metabolism including the degradation of mRNA, and processing or translation of the modified RNA. Its abnormal changes will lead to disrupting the regulation of gene expression and promoting the occurrence of aberrant cell behavior. The abnormal expression of m6A enzyme system can be a crucial impact disturbing the abundance of m6A, thus affecting the expression of oncogenes or tumor suppressor genes in various types of cancer. In this review, we elucidate the special role of m6A "writers", "erasers", and "readers" in normal physiology, and how their altered expression affects the cell metabolism and promotes the occurrence of tumors. We also discuss the potential to target these enzymes for cancer diagnosis, prognosis, and the development of new therapies.
    Keywords:  N6-methyladenosine; cancer; m6A; m6A enzyme system; oncogene and tumor suppressor gene
    DOI:  https://doi.org/10.3389/fonc.2020.623634
  6. Biochem Biophys Res Commun. 2021 Feb 06. pii: S0006-291X(21)00153-4. [Epub ahead of print]546 54-58
    Bade D, Cai Q, Li L, Yu K, Dai X, Miao W, Wang Y.
      Protein α-N-methylation is an evolutionarily conserved type of post-translational modification; however, little is known about the regulatory mechanisms for this modification. Methylation at the N6 position of adenosine in mRNAs is dynamic and modulates their stability, splicing, and translational efficiency. Here, we found that the expression of N-terminal methyltransferase 1 (NTMT1) protein is altered by depletion of those genes encoding the reader/writer/eraser proteins of N6-methyladenosine (m6A). We also observed that MRG15 is N-terminally methylated by NTMT1, and this methylation could also be modulated by reader/writer/eraser proteins of m6A. Together, these results revealed a novel m6A-based epitranscriptomic mechanism in regulating protein N-terminal methylation.
    Keywords:  Epitranscriptomics; Mass spectrometry; N-terminal methylation; N6-methyladenosine; Post-translational modification; RNA modification
    DOI:  https://doi.org/10.1016/j.bbrc.2021.01.088
  7. Cell Biol Int. 2021 Feb 09.
    Li Q, Wang C, Dong W, Su Y, Ma Z.
      The N6-methyladenosine (m6A) modification is one of the most prevalent methylations in eukaryotic mRNA and it is essential for the development of many important biological processes as multiple types of tumors. One of the most important enzymes catalyzing generation of m6A on mRNA is Wilms' tumor 1-associating protein (WTAP), however, the potential role of WTAP in endometrial cancer (EC) still remains unknown. Here, we investigated WTAP expression level in cancer tissue and paracancerous tissue from EC patient. Subsequently, WTAP was knocked down by siRNA in endometrial cancer cell line of Ishikawa and HEC-1A respectively. Cell proliferation, migration and invasion were studied. The expression of Caveolin-1 (CAV-1) was detected by qPCR. The enrichments of m6A and METTL3 on CAV-1 were detected using RIP-qPCR. The activity of NF-κB was studied using Western Blot. We observed that WTAP was dramatically up-regulated in cancer tissue, and enhanced cell proliferation, migration and invasion and decreased apoptotic in EC in vivo and in vitro, which indicated higher tumor malignancy and worse survival outcome. After WTAP was knocked down in EC cells, CAV-1 was significantly upregulated, and the enrichments of m6A and METTL3 at 3'UTR region of CAV-1 were decreased. Moreover, the activity of NF-κB signaling pathway was inhibited by its regulator CAV-1. Taken together, we concluded that WTAP could methylate 3'UTR of CAV-1 and downregulate CAV-1 expression to activate NF-κB signaling pathway in EC, which promoted endometrial cancer progression. This article is protected by copyright. All rights reserved.
    Keywords:  N6-methyladenosine; NF-κB signaling pathway; Wilms' tumor 1-associating protein; caveolin-1; endometrial cancer
    DOI:  https://doi.org/10.1002/cbin.11570
  8. Genes Dis. 2021 Jan;8(1): 6-7
    He RZ, Jiang J, Luo DX.
      Circular RNAs (circRNAs) are playing emerging role in the pathogenesis of cancers, but the mechanisms still unknown. In the recent issue of the Nature Communications, Chen and colleagues have demonstrated that YTHDC1 facilitates N6-methyladenosine modified circNSUN2 cytoplasmic export and the circNSUN2/IGF2BP2/HMGA2 complex stabilizes HMGA2 to promote colorectal liver metastasis. These discoveries not only expand our understanding of circRNAs biology in tumor, but also demonstrate that m6A modification plays a key role for circRNAs in RNA metabolism. Therefore, these findings indicate that circRNAs may be a new approach for therapeutic target of cancers.
    Keywords:  CircRNAs; Colorectal carcinoma; IGF2BP2; Metastasis; N6-methyladenosine
    DOI:  https://doi.org/10.1016/j.gendis.2019.12.002
  9. J Immunother Cancer. 2021 Feb;pii: e001646. [Epub ahead of print]9(2):
    Zhong J, Liu Z, Cai C, Duan X, Deng T, Zeng G.
      BACKGROUND: Recent studies have focused on the correlation between N6-methyladenosine (m6A) modification and specific tumor-infiltrating immune cells. However, the potential roles of m6A modification in the tumor immune landscape remain elusive.METHODS: We comprehensively evaluated the m6A modification patterns and tumor immune landscape of 513 clear cell renal cell carcinoma (ccRCC) patients, and correlated the m6A modification patterns with the immune landscape. The m6Ascore was established using principal component analysis. Multivariate Cox regression analysis was performed to evaluate the prognostic value of the m6Ascore.
    RESULTS: We identified three m6Aclusters-characterized by differences in Th17 signature, extent of intratumor heterogeneity, overall cell proliferation, aneuploidy, expression of immunomodulatory genes, overall somatic copy number alterations, and prognosis. The m6Ascore was established to quantify the m6A modification pattern of individual ccRCC patients. Further analyses revealed that the m6Ascore was an independent prognostic factor of ccRCC. Finally, we verified the prognostic value of the m6Ascore in the programmed cell death protein 1 (PD-1) blockade therapy of patients with advanced ccRCC.
    CONCLUSIONS: This study demonstrated the correlation between m6A modification and the tumor immune landscape in ccRCC. The comprehensive evaluation of m6A modification patterns in individual ccRCC patients enhances our understanding of the tumor immune landscape and provides a new approach toward new and improved immunotherapeutic strategies for ccRCC patients.
    Keywords:  immunotherapy; kidney neoplasms
    DOI:  https://doi.org/10.1136/jitc-2020-001646
  10. Nucleic Acids Res. 2021 Feb 12. pii: gkab065. [Epub ahead of print]
    Hou G, Zhao X, Li L, Yang Q, Liu X, Huang C, Lu R, Chen R, Wang Y, Jiang B, Yu J.
      N 6-Methyladenosine (m6A) is the most abundant modification within diverse RNAs including mRNAs and lncRNAs and is regulated by a reversible process with important biological functions. Human YTH domain family 2 (YTHDF2) selectively recognized m6A-RNAs to regulate degradation. However, the possible regulation of YTHDF2 by protein post-translational modification remains unknown. Here, we show that YTHDF2 is SUMOylated in vivo and in vitro at the major site of K571, which can be induced by hypoxia while reduced by oxidative stress and SUMOylation inhibitors. SUMOylation of YTHDF2 has little impact on its ubiquitination and localization, but significantly increases its binding affinity of m6A-modified mRNAs and subsequently results in deregulated gene expressions which accounts for cancer progression. Moreover, Disease-free survival analysis of patients with lung adenocarcinoma derived from TCGA dataset reveals that higher expression of YTHDF2 together with higher expression of SUMO1 predicts poor prognosis. Our works uncover a new regulatory mechanism for YTHDF2 recognition of m6A-RNAs and highlight the importance of YTHDF2 SUMOylation in post-transcriptional gene expression regulation and cancer progression.
    DOI:  https://doi.org/10.1093/nar/gkab065
  11. Mol Cancer Res. 2021 Feb 09.
    Xiao P, Liu YK, Han W, Hu Y, Zhang BY, Liu WL.
      Gefitinib is suitable for the treatment of locally advanced or metastatic non-small cell lung cancer. However, the development of acquired resistance limits its long-term efficacy in regardless of significant clinical benefit to patients. Therefore, to elucidate the mechanism of gefitinib resistance in addition to target gene mutation may greatly increase its clinical efficacy. It was found first that N 6-methyladenosine RNA demethylase FTO was significantly enriched in serum exosomes of gefitinib-resistant (GR) patients compared with that of gefitinib-sensitive (GS) patients through exosomal RNA sequencing. Meanwhile, the average m6A proportion in GR patients was significantly lower when compared with that in GS patients. Besides, GR cell-derived exosome internalization attenuated the total m6A abundance and gefitinib sensitivity of PC9 cells. Not only FTO knockdown enhanced the gefitinib sensitivity of GR cells but also FTO reduction in donor exosomes alleviated the acquired resistance of recipient PC9 cells. GR cell-derived exosomal-FTO promoted ABCC10 of recipient cells in a m6A-dependent manner. FTO/YTHDF2/ABCC10 axis played a role in intercellular transmission of GR cell-derived exosome-mediated gefitinib resistance both in vitro and in vivo. In general, this research showed that m6A modification was involved in the decrease of gefitinib sensitivity. GR cell-derived exosomes could decrease gefitinib sensitivity of recipient cells in exosomal delivery of FTO-dependent manner. FTO/YTHDF2/ABCC10 axis played a role in intercellular transmission of GR cell-derived exosome-mediated gefitinib resistance. IMPLICATIONS: Our results elucidated another potential molecular mechanism of gefitinib resistance in non-small cell lung cancer besides secondary EGFR mutations.
    DOI:  https://doi.org/10.1158/1541-7786.MCR-20-0541
  12. Cancer Cell Int. 2021 Feb 10. 21(1): 99
    Wang J, Chen L, Qiang P.
      The human insulin-like growth factor 2 (IGF2) mRNA binding proteins 2 (IGF2BP2/IMP2) is an RNA-binding protein that regulates multiple biological processes. Previously, IGF2BP2 was thought to be a type 2 diabetes (T2D)-associated gene. Indeed IGF2BP2 modulates cellular metabolism in human metabolic diseases such as diabetes, obesity and fatty liver through post-transcriptional regulation of numerous genes in multiple cell types. Emerging evidence shows that IGF2BP2 is an N6-methyladenosine (m6A) reader that participates in the development and progression of cancers by communicating with different RNAs such as microRNAs (miRNAs), messenger RNAs (mRNAs) and long non-coding RNAs (lncRNAs). Additionally, IGF2BP2 is an independent prognostic factor for multiple cancer types. In this review, we summarize the current knowledge on IGF2BP2 with regard to diverse human metabolic diseases and its potential for cancer prognosis.
    Keywords:  Biological function; Cancers; IGF2BP2; Metabolic disease; m6A
    DOI:  https://doi.org/10.1186/s12935-021-01799-x
  13. Front Cell Dev Biol. 2020 ;8 629030
    Zhang Y, Xu S, Xu G, Gao Y, Li S, Zhang K, Tian Z, Guo J, Li X, Xu J, Li Y.
      N6-methyladenosine (m6A) plays critical roles in human development and cancer progression. However, our knowledge regarding the dynamic expression of m6A regulators during human tissue development is still lacking. Here, we comprehensively analyzed the dynamic expression alterations of m6A regulators during seven tissue development and eight cancer types. We found that m6A regulators globally exhibited decreased expression during development. In addition, IGF2BP1/2/3 (insulinlike growth factor 2 MRNA-binding protein 1/2/3) exhibited reverse expression pattern in cancer progression, suggesting an oncofetal reprogramming in cancer. The expressions of IGF2BP1/2/3 were regulated by genome alterations, particularly copy number amplification in cancer. Clinical association analysis revealed that higher expressions of IGF2BP1/2/3 were associated with worse survival of cancer patients. Finally, we found that genes significantly correlated with IGF2BP1/2/3 were significantly enriched in cancer hallmark-related pathways. In summary, dynamic expression analysis will guide both mechanistic and therapeutic roles of m6A regulators during tissue development and cancer progression.
    Keywords:  cancer; gene experession; m6A regulators; survival; tissue development
    DOI:  https://doi.org/10.3389/fcell.2020.629030
  14. Mol Cancer. 2021 02 08. 20(1): 29
    Chen H, Yao J, Bao R, Dong Y, Zhang T, Du Y, Wang G, Ni D, Xun Z, Niu X, Ye Y, Li HB.
      BACKGROUND: The four major RNA adenosine modifications, i.e., m6A, m1A, alternative polyadenylation, and adenosine-to-inosine RNA editing, are mediated mostly by the "writer" enzymes and constitute critical mechanisms of epigenetic regulation in immune response and tumorigenesis. However, the cross-talk and potential roles of these "writers" in the tumor microenvironment (TME), drug sensitivity, and immunotherapy remain unknown.METHODS: We systematically characterized mRNA expression and genetic alterations of 26 RNA modification "writers" in colorectal cancer (CRC), and evaluated their expression pattern in 1697 CRC samples from 8 datasets. We used an unsupervised clustering method to assign the samples into two patterns of expression of RNA modification "writers". Subsequently, we constructed the RNA modification "writer" Score (WM_Score) model based on differentially expressed genes (DEGs) responsible for the RNA modification patterns to quantify the RNA modification-related subtypes of individual tumors. Furthermore, we performed association analysis for WM_Score and characteristics of TME, consensus molecular subtypes (CMSs), clinical features, transcriptional and post-transcriptional regulation, drug response, and the efficacy of immunotherapy.
    RESULTS: We demonstrated that multi-layer alterations of RNA modification "writer" are associated with patient survival and TME cell-infiltrating characteristics. We identified two distinct RNA modification patterns, characterized by a high and a low WM_Score. The WM_Score-high group was associated with worse patient overall survival and with the infiltration of inhibitory immune cells, such as M2 macrophages, EMT activation, and metastasis, while the WM_Score-low group was associated with a survival advantage, apoptosis, and cell cycle signaling pathways. WM_Score correlated highly with the regulation of transcription and post-transcriptional events contributing to the development of CRC. In response to anti-cancer drugs, WM_Score highly negatively correlated (drug sensitive) with drugs which targeted oncogenic related pathways, such as MAPK, EGFR, and mTOR signaling pathways, positively correlated (drug resistance) with drugs which targeted in apoptosis and cell cycle. Importantly, the WM_Score was associated with the therapeutic efficacy of PD-L1 blockade, suggesting that the development of potential drugs targeting these "writers" to aid the clinical benefits of immunotherapy.
    CONCLUSIONS: Our study is the first to provide a comprehensive analysis of four RNA modifications in CRC. We revealed the potential function of these writers in TME, transcriptional and post-transcriptional events, and identified their therapeutic liability in targeted therapy and immunotherapy. This work highlights the cross-talk and potential clinical utility of RNA modification "writers" in cancer therapy.
    Keywords:  Colorectal cancer; Drug sensitivity; Immunotherapy; RNA modification “writer”; Tumor microenvironment; WM_Score
    DOI:  https://doi.org/10.1186/s12943-021-01322-w
  15. Biochem Biophys Res Commun. 2021 Feb 08. pii: S0006-291X(21)00177-7. [Epub ahead of print]546 65-73
    Wang S, Fan X, Zhu J, Xu D, Li R, Chen R, Hu J, Shen Y, Hao J, Wang K, Jiang X, Wang Y, Jiang Y, Li J, Zhang J.
      The occurrence and development of tumors cannot be separated from the influence of differentiation at different stages and levels. Our study found that E-cadherin was significantly increased in cell model induced by sodium butyrate and cell density, while METTL3, METTL16 and WTAP were decreased during the differentiation of cells. In the clinicopathological tissues, E-cadherin was low expressed in poorly differentiated tumor tissues and above three regulators were highly expressed in poorly differentiated tissues. At the levels of clinicopathological differentiation, tissue differentiation and cell differentiation, the result indicated that the poor prognosis of colorectal cancer (CRC) may be closely related to high expression of total m6A level and high expression of METTL3, METTL16 and WTAP.
    Keywords:  Colorectal cancer; Differentiation; E-cadherin; METTL3; WTAP
    DOI:  https://doi.org/10.1016/j.bbrc.2021.02.001
  16. Brief Funct Genomics. 2021 Feb 10. pii: elab003. [Epub ahead of print]
    Miano V, Codino A, Pandolfini L, Barbieri I.
      Post-synthesis modification of biomolecules is an efficient way of regulating and optimizing their functions. The human epitranscriptome includes a variety of more than 100 modifications known to exist in all RNA subtypes. Modifications of non-coding RNAs are particularly interesting since they can directly affect their structure, stability, interaction and function. Indeed, non-coding RNAs such as tRNA and rRNA are the most modified RNA species in eukaryotic cells. In the last 20 years, new functions of non-coding RNAs have been discovered and their involvement in human disease, including cancer, became clear. In this review, we will present the evidence connecting modifications of different non-coding RNA subtypes and their role in cancer.
    Keywords:  RNA epigenetics; RNA methylation; RNA modifications; cancer; epitranscriptomics; non-coding RNA
    DOI:  https://doi.org/10.1093/bfgp/elab003
  17. Nucleic Acids Res. 2021 Feb 09. pii: gkab033. [Epub ahead of print]
    Ieong KW, Indrisiunaite G, Prabhakar A, Puglisi JD, Ehrenberg M.
      We used quench flow to study how N6-methylated adenosines (m6A) affect the accuracy ratio between kcat/Km (i.e. association rate constant (ka) times probability (Pp) of product formation after enzyme-substrate complex formation) for cognate and near-cognate substrate for mRNA reading by tRNAs and peptide release factors 1 and 2 (RFs) during translation with purified Escherichia coli components. We estimated kcat/Km for Glu-tRNAGlu, EF-Tu and GTP forming ternary complex (T3) reading cognate (GAA and Gm6AA) or near-cognate (GAU and Gm6AU) codons. ka decreased 10-fold by m6A introduction in cognate and near-cognate cases alike, while Pp for peptidyl transfer remained unaltered in cognate but increased 10-fold in near-cognate case leading to 10-fold amino acid substitution error increase. We estimated kcat/Km for ester bond hydrolysis of P-site bound peptidyl-tRNA by RF2 reading cognate (UAA and Um6AA) and near-cognate (UAG and Um6AG) stop codons to decrease 6-fold or 3-fold by m6A introduction, respectively. This 6-fold effect on UAA reading was also observed in a single-molecule termination assay. Thus, m6A reduces both sense and stop codon reading accuracy by decreasing cognate significantly more than near-cognate kcat/Km, in contrast to most error inducing agents and mutations, which increase near-cognate at unaltered cognate kcat/Km.
    DOI:  https://doi.org/10.1093/nar/gkab033
  18. Genome Med. 2021 Feb 10. 13(1): 23
    Mancarella D, Plass C.
      Epigenetic alterations are associated with normal biological processes such as aging or differentiation. Changes in global epigenetic signatures, together with genetic alterations, are driving events in several diseases including cancer. Comparative studies of cancer and healthy tissues found alterations in patterns of DNA methylation, histone posttranslational modifications, and changes in chromatin accessibility. Driven by sophisticated, next-generation sequencing-based technologies, recent studies discovered cancer epigenomes to be dominated by epigenetic patterns already present in the cell-of-origin, which transformed into a neoplastic cell. Tumor-specific epigenetic changes therefore need to be redefined and factors influencing epigenetic patterns need to be studied to unmask truly disease-specific alterations. The underlying mechanisms inducing cancer-associated epigenetic alterations are poorly understood. Studies of mutated epigenetic modifiers, enzymes that write, read, or edit epigenetic patterns, or mutated chromatin components, for example oncohistones, help to provide functional insights on how cancer epigenomes arise. In this review, we highlight the importance and define challenges of proper control tissues and cell populations to exploit cancer epigenomes. We summarize recent advances describing mechanisms leading to epigenetic changes in tumorigenesis and briefly discuss advances in investigating their translational potential.
    Keywords:  Cancer; Cell-of-origin; Epigenetic signatures; Epigenetic therapy; Epigenomics; Oncohistones; Precision oncology; Tumor subclassification
    DOI:  https://doi.org/10.1186/s13073-021-00837-7