bims-nucpor 2022-06-26 papers

bims-nucpor

Biomed News

on Nuclear pore complex and nucleoporins in stress, aging and disease

Issue of 2022–06–26
seven papers selected by
Sara Mingu, Johannes Gutenberg University

Nuclear pore complex acetylation regulates mRNA export and cell cycle commitment in budding yeast.
Up-regulation of POM121 is linked to prostate cancer aggressiveness and serves as a prognostic biomarker.
Hepatitis B virus virion secretion is a CRM1-spike-mediated late event.
Anaplasma phagocytophilum Ankyrin A Protein (AnkA) Enters the Nucleus Using an Importin-β-, RanGTP-Dependent Mechanism.
Nuclear Transporter IPO13 Is Central to Efficient Neuronal Differentiation.
Cardiac Allograft Rejection Induces Changes in Nucleocytoplasmic Transport: RANGAP1 as a Potential Non-Invasive Biomarker.
Inhibition of karyopherin β1-mediated nuclear import disrupts oncogenic lineage- defining transcription factor activity in small cell lung cancer.

EMBO J. 2022 Jun 23. e2021110271

Nuclear pore complex acetylation regulates mRNA export and cell cycle commitment in budding yeast.

Mercè Gomar-Alba, Vasilisa Pozharskaia, Bogdan Cichocki, Celia Schaal, Arun Kumar, Basile Jacquel, Gilles Charvin, J Carlos Igual, Manuel Mendoza.

  Nuclear pore complexes (NPCs) mediate communication between the nucleus and the cytoplasm, and regulate gene expression by interacting with transcription and mRNA export factors. Lysine acetyltransferases (KATs) promote transcription through acetylation of chromatin-associated proteins. We find that Esa1, the KAT subunit of the yeast NuA4 complex, also acetylates the nuclear pore basket component Nup60 to promote mRNA export. Acetylation of Nup60 recruits the mRNA export factor Sac3, the scaffolding subunit of the Transcription and Export 2 (TREX-2) complex, to the nuclear basket. The Esa1-mediated nuclear export of mRNAs in turn promotes entry into S phase, which is inhibited by the Hos3 deacetylase in G1 daughter cells to restrain their premature commitment to a new cell division cycle. This mechanism is not only limited to G1/S-expressed genes but also inhibits the expression of the nutrient-regulated GAL1 gene specifically in daughter cells. Overall, these results reveal how acetylation can contribute to the functional plasticity of NPCs in mother and daughter yeast cells. In addition, our work demonstrates dual gene expression regulation by the evolutionarily conserved NuA4 complex, at the level of transcription and at the stage of mRNA export by modifying the nucleoplasmic entrance to nuclear pores.

Keywords:  G1-S transition; Hos3; NuA4; mRNA export; nuclear pore complex

DOI:  https://doi.org/10.15252/embj.2021110271
Urol Oncol. 2022 Jun 17. pii: S1078-1439(22)00190-9. [Epub ahead of print]

Up-regulation of POM121 is linked to prostate cancer aggressiveness and serves as a prognostic biomarker.

Finn Becker, Anne Offermann, Marie C Roesch, Vincent Joerg, Doris Roth, Verena Lubczyk, Rainer Kuefer, Verena Sailer, Jutta Kirfel, Axel S Merseburger, Sven Perner.

   PURPOSE: Nucleoporins as components of the nuclear pore complex (NCP) are known for regulating nuclear-cytoplasmatic transport. Recently, the nucleoporin POM121 was found to have an important impact on intranuclear translocation of prostate cancer (PCa)-specific tumor drivers including the androgen receptor (AR). The aim of our study was to assess the potential of POM121 as a prognostic biomarker.
METHODS: Therefore, we performed immunohistochemistry (IHC) for POM121 on a large clinically, well characterized PCa tissue cohort comprising benign prostatic samples, radical prostatectomy (RPE) samples, lymph node metastases, local recurrent tumors and distant metastases of 289 patients. Using a semi automated tissue image analysis software we evaluated POM121 protein expression level based on IHC.
RESULTS: We could show that POM121 expression increases during tumor progression. Expression levels were significantly higher in primary tumors compared to benign samples (P = 0.001), and substantially higher in advanced tumors (P < 0.001) and in distant metastases (P = 0.006) compared to primary tumors. Furthermore, POM121 expression predicts biochemical recurrence free survival (BFS) after surgery independent of the WHO group and other clinicopathological markers. 5-years BFS with primary tumors lacking POM121 and expressing POM121 was 88.8% and 68.9%, respectively.
CONCLUSION: Our study reveals the potential of POM121 as a potential biomarker for PCa, predicting BFS independent of other common clinicopathological parameters. Furthermore, POM121 might be a new targetable structure for patients suffering from advanced PCa.

Keywords:  Androgen receptor; Biomarker; Nuclear pore complex; Nucleoporins; POM121; Prostate cancer

DOI:  https://doi.org/10.1016/j.urolonc.2022.05.019
J Biomed Sci. 2022 Jun 21. 29(1): 44

Hepatitis B virus virion secretion is a CRM1-spike-mediated late event.

Pei-Yi Su, Shin-Chwen Bruce Yen, Ching-Chun Yang, Chih-Hsu Chang, Wen-Chang Lin, Chiaho Shih.

   BACKGROUND: Hepatitis B virus (HBV) is a major human pathogen worldwide. To date, there is no curative treatment for chronic hepatitis B. The mechanism of virion secretion remains to be investigated. Previously, we found that nuclear export of HBc particles can be facilitated via two CRM1-specific nuclear export signals (NES) at the spike tip.
METHODS: In this study, we used site-directed mutagenesis at the CRM1 NES, as well as treatment with CRM1 inhibitors at a low concentration, or CRM1-specific shRNA knockdown, in HBV-producing cell culture, and measured the secretion of various HBV viral and subviral particles via a native agarose gel electrophoresis assay. Separated HBV particles were characterized by Western blot analysis, and their genomic DNA contents were measured by Southern blot analysis. Secreted extracellular particles were compared with intracellular HBc capsids for DNA synthesis and capsid formation. Virion secretion and the in vivo interactions among HBc capsids, CRM1 and microtubules, were examined by proximity ligation assay, immunofluorescence microscopy, and nocodazole treatment.
RESULTS: We report here that the tip of spike of HBV core (HBc) particles (capsids) contains a complex sensor for secretion of both HBV virions and naked capsids. HBV virion secretion is closely associated with HBc nuclear export in a CRM1-dependent manner. At the conformationally flexible spike tips of HBc particles, NES motifs overlap extensively with motifs important for secretion of HBV virions and naked capsids.
CONCLUSIONS: We provided experimental evidence that virions and naked capsids can egress via two distinct, yet overlapping, pathways. Unlike the secretion of naked capsids, HBV virion secretion is highly CRM1- and microtubule-dependent. CRM1 is well known for its involvement in nuclear transport in literature. To our knowledge, this is the first report that CRM1 is required for virion secretion. CRM1 inhibitors could be a promising therapeutic candidate for chronic HBV patients in clinical medicine.

Keywords:  CRM1 (chromosome region maintenance 1); HBV core protein (HBc); HBc capsids; Hepatitis B virus (HBV); Microtubule; Naked capsids; Proximity ligation assay (PLA); Spike; Therapeutic treatment; Virion secretion

DOI:  https://doi.org/10.1186/s12929-022-00827-w
Front Cell Infect Microbiol. 2022 ;12 828605

Anaplasma phagocytophilum Ankyrin A Protein (AnkA) Enters the Nucleus Using an Importin-β-, RanGTP-Dependent Mechanism.

Yuri Kim, Jianyang Wang, Emily G Clemens, Dennis J Grab, J Stephen Dumler.

  Anaplasma phagocytophilum, a tick-borne obligately intracellular bacterium of neutrophils, causes human granulocytic anaplasmosis. Ankyrin A (AnkA), an effector protein with multiple ankyrin repeats (AR) is injected via type IV-secretion into the host neutrophil to gain access to the nucleus where it modifies the epigenome to promote microbial fitness and propagation. AR proteins transported into the host cell nucleus must use at least one of two known eukaryotic pathways, the classical importin β-dependent pathway, and/or the RanGDP- and AR (ankyrin-repeat)-dependent importin β-independent (RaDAR) pathway. Truncation of the first four AnkA N-terminal ARs (AR1-4), but not other regions, prevents AnkA nuclear accumulation. To investigate the mechanism of nuclear import, we created point mutations of AnkA N-terminal ARs, predicted to interfere with RaDAR protein import, and used importazole, a specific inhibitor of the importin α/β, RanGTP-dependent pathway. Nuclear colocalization analysis shows that nuclear localization of AnkA is unaffected by single AR1-4 mutations but is significantly reduced by single mutations in consecutive ARs suggesting RaDAR protein nuclear import. However, AnkA nuclear localization was also decreased with importazole, and with GTPγS. Furthermore, A. phagocytophilum growth in HL-60 cells was completely suppressed with importazole, indicating that A. phagocytophilum propagation requires a β-importin-dependent pathway. A typical classical NLS overlapping AR4 was subsequently identified suggesting the primacy of the importin-α/β system in AnkA nuclear localization. Whether the mutational studies of putative key residues support RaDAR NLS function or simply reflect structural changes that diminish engagement of an AR-NLS-importin pathway needs to be resolved through careful structure-function studies.

Keywords:  Anaplasma phagocytophilum; AnkA; RaDAR; ankyrin repeat proteins; nuclear localization signal

DOI:  https://doi.org/10.3389/fcimb.2022.828605
Cells. 2022 Jun 12. pii: 1904. [Epub ahead of print]11(12):

Nuclear Transporter IPO13 Is Central to Efficient Neuronal Differentiation.

Katarzyna A Gajewska, John M Haynes, David A Jans.

  Molecular transport between the nucleus and cytoplasm of the cell is mediated by the importin superfamily of transport receptors, of which the bidirectional transporter Importin 13 (IPO13) is a unique member, with a critical role in early embryonic development through nuclear transport of key regulators, such as transcription factors Pax6, Pax3, and ARX. Here, we examined the role of IPO13 in neuronal differentiation for the first time, using a mouse embryonic stem cell (ESC) model and a monolayer-based differentiation protocol to compare IPO13-/- to wild type ESCs. Although IPO13-/- ESCs differentiated into neural progenitor cells, as indicated by the expression of dorsal forebrain progenitor markers, reduced expression of progenitor markers Pax6 and Nestin compared to IPO13-/- was evident, concomitant with reduced nuclear localisation/transcriptional function of IPO13 import cargo Pax6. Differentiation of IPO13-/- cells into neurons appeared to be strongly impaired, as evidenced by altered morphology, reduced expression of key neuronal markers, and altered response to the neurotransmitter glutamate. Our findings establish that IPO13 has a key role in ESC neuronal differentiation, in part through the nuclear transport of Pax6.

Keywords:  embryonic stem cells; neurogenesis; nuclear transport

DOI:  https://doi.org/10.3390/cells11121904
J Pers Med. 2022 May 31. pii: 913. [Epub ahead of print]12(6):

Cardiac Allograft Rejection Induces Changes in Nucleocytoplasmic Transport: RANGAP1 as a Potential Non-Invasive Biomarker.

Silvia Lozano-Edo, Esther Roselló-Lletí, Ignacio Sánchez-Lázaro, Estefanía Tarazón, Manuel Portolés, Maryem Ezzitouny, Raquel Lopez-Vilella, Miguel Angel Arnau, Luis Almenar, Luis Martínez-Dolz.

  The non-invasive diagnosis of acute cellular rejection (ACR) is a major challenge. We performed a molecular study analyzing the predictive capacity of serum RanGTPase AP1 (RANGAP1) for diagnosing ACR during the first year after heart transplantation (HT). We included the serum samples of 75 consecutive HT patients, extracted after clinical stability, to determine the RANGAP1 levels through ELISA. In addition, various clinical, analytical, and echocardiographic variables, as well as endomyocardial biopsy results, were collected. RANGAP1 levels were higher in patients who developed ACR (median 63.15 ng/mL; (inter-quartile range (IQR), 36.61-105.69) vs. 35.33 ng/mL (IQR, 19.18-64.59); p = 0.02). Receiver operating characteristic (ROC) curve analysis confirmed that RANGAP1 differentiated between patients with and without ACR (area under curve (AUC), 0.70; p = 0.02), and a RANGAP1 level exceeding the cut-off point (≥90 ng/mL) was identified as a risk factor for the development of ACR (OR, 6.8; p = 0.006). Two independent predictors of ACR identified in this study were higher RANGAP1 and N-terminal pro-brain natriuretic peptide levels. The analysis of the ROC curve of the model showed a significant AUC of 0.77, p = 0.001. Our findings suggest that RANGAP1 quantification facilitates risk prediction for the occurrence of ACR and could be considered as a novel non-invasive biomarker of ACR.

Keywords:  RANGAP1; biomarkers; cardiac rejection; heart transplantation; nucleocytoplasmic transport

DOI:  https://doi.org/10.3390/jpm12060913
Cancer Res. 2022 Jun 24. pii: canres.3713.2021. [Epub ahead of print]

Inhibition of karyopherin β1-mediated nuclear import disrupts oncogenic lineage- defining transcription factor activity in small cell lung cancer.

Demetra P Kelenis, Kathia E Rodarte, Rahul K Kollipara, Karine Pozo, Shreoshi Pal Choudhuri, Kyle B Spainhower, Sarah J Wait, Victor Stastny, Trudy G Oliver, Jane E Johnson.

Genomic studies support the classification of small cell lung cancer (SCLC) into subtypes based on expression of lineage-defining transcription factors ASCL1 and NEUROD1, which together are expressed in ~86% of SCLC. ASCL1 and NEUROD1 activate SCLC oncogene expression, drive distinct transcriptional programs, and maintain the in vitro growth and oncogenic properties of ASCL1 or NEUROD1-expressing SCLC. ASCL1 is also required for tumor formation in SCLC mouse models. A strategy to inhibit the activity of these oncogenic drivers may therefore provide both a targeted therapy for the predominant SCLC subtypes, and a tool to investigate the underlying lineage-plasticity of established SCLC tumors. However, there are no known agents that inhibit ASCL1 or NEUROD1 function. In this study, we identify a novel strategy to pharmacologically target ASCL1 and NEUROD1 activity in SCLC, by exploiting the nuclear localization required for function of these transcription factors. Karyopherin β1 (KPNB1) was identified as a nuclear import receptor for both ASCL1 and NEUROD1 in SCLC, and inhibition of KPNB1 led to impaired ASCL1 and NEUROD1 nuclear accumulation and transcriptional activity. Pharmacologic targeting of KPNB1 preferentially disrupted the growth of ASCL1+ and NEUROD1+ SCLC cells in vitro, and suppressed ASCL1+ tumor growth in vivo, an effect mediated by a combination of impaired ASCL1 downstream target expression, cell cycle activity, and proteostasis. These findings broaden the support for targeting nuclear transport as an anticancer therapeutic strategy and have implications for targeting lineage transcription factors in tumors beyond SCLC.

DOI: https://doi.org/10.1158/0008-5472.CAN-21-3713