Hypoxia-driven deSUMOylation of EXOSC10 promotes adaptive changes in the transcriptome profile
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ABSTRACT: Reduced oxygen availability (hypoxia) triggers adaptive cellular responses via hypoxia-inducible factor (HIF)-dependent transcriptional activation. Adaptation to hypoxia also involves transcription-independent processes like post-translational modifications, however these mechanisms are poorly characterized. Investigating the involvement of protein SUMOylation in response to hypoxia, we discovered that hypoxia strongly decreases the SUMOylation of Exosome subunit 10 (EXOSC10), the catalytic subunit of the RNA exosome, in a HIF-independent manner. EXOSC10 is a multifunctional exoribonuclease enriched in the nucleolus that mediates the processing and degradation of various RNA species. We demonstrate that the Ubiquitin-specific protease 36 (USP36) SUMOylates EXOSC10 and we reveal SUMO1/sentrin-specific peptidase 3 (SENP3) as the enzyme mediating deSUMOylation of EXOSC10. Under hypoxia, EXOSC10 dissociates from USP36 and translocates from the nucleolus to the nucleoplasm concomitant with its deSUMOylation. Loss of EXOSC10 SUMOylation does not detectably affect rRNA maturation but affects the mRNA transcriptome by modulating the expression levels of hypoxia-related genes. Our data suggest that dynamic modulation of EXOSC10 SUMOylation and localization under hypoxia regulates the RNA degradation machinery to facilitate cellular adaptation to low oxygen conditions.
Project description:The RNA exosome is an essential 3’ to 5’ processing exoribonuclease complex that mediates degradation, processing, and quality control of virtually all eukaryotic RNAs. The nucleolar RNA exosome, consisting of a 9-subunit core and a distributive 3ʹ to 5ʹ exonuclease EXOSC10, plays a critical role in processing and degrading nucleolar RNAs, including pre-ribosomal RNA (pre-rRNA). However, how the RNA exosome is regulated in the nucleolus is poorly understood. Here, we report that the nucleolar ubiquitin-specific protease USP36 is a novel regulator of the nucleolar RNA exosome. USP36 binds to the RNA exosome through direct interaction with EXOSC10. Interestingly, USP36 does not significantly regulate the levels of EXOSC10 and other exosome subunits. Instead, it mediates EXOSC10 SUMOylation at Lys (K) 583. Mutating K583 impaired the binding of EXOSC10 to pre-rRNAs and the K583R mutant failed to rescue the defects in rRNA processing and cell growth inhibition caused by knockdown of endogenous EXOSC10, indicating that EXOSC10 SUMOylation is critical for the exosome function in rRNA processing. Furthermore, USP36 itself is a rRNA-binding protein that associates pre-rRNA. These results suggest that USP36 acts as a novel SUMO ligase to mediate EXOSC10 SUMOylation critical for the RNA exosome function in rRNA processing and ribosome biogenesis.
Project description:Growing mammalian oocytes accumulate substantial amounts of RNA, most of which are degraded during the subsequent maturation stage. The growth-to-maturation transition begins with germinal vesicle breakdown (GVBD, envisioned as nuclear envelope breakdown) and is critical for oocyte quality. However, the concomitant changes in the transcriptome during GVBD as well as the underlying machinery remained unclear. Here, we report that an RNA exosome-associated RNase, EXOSC10, sculpts the transcriptome at multiple level to facilitate the oocyte growth-to-maturation transition. We establish an oocyte-specific knockout of Exosc10 in mice using CRISPR/Cas9 and find female subfertility due to failed GVBD. By performing single oocyte RNA-seq in different ways, we document dysregulated transcriptomes, unsuccessfully processed rRNAs in mutant oocytes, and many up-regulated RNAs that encode proteins important for endomembrane trafficking, meiotic cell cycle and RNA metabolism. EXOSC10-depleted oocytes have impaired endomembrane components including endosome, lysosome, ER and Golgi. In addition, CDK1 fails to be activated possibly due to persistent WEE1 activity, which blocked lamina phosphorylation and disassembly in mutant oocytes. Collectively, we propose that EXOSC10 promotes the growth-to-maturation transition in mouse oocytes by degrading mRNAs that encode growth-phase factors and sculpting the transcriptome to support the maturation phase of oogenesis.
Project description:Cell-based studies of human ribonucleases traditionally relies on methods that deplete proteins slowly. To assess their immediate roles in nuclear RNA biology, we engineered cells where the 3’->5’ exoribonucleases of the exosome complex, Dis3 and EXOSC10, can be eliminated within 60 minutes. Loss of Dis3 has the greatest impact, causing thousands of enhancer RNAs, intragenic transcripts, promoter upstream transcripts (PROMPTs) and products of premature cleavage and polyadenylation (PCPA) to accumulate. Interestingly, EXOSC10 only targets these substrates when Dis3 is absent, which is explained by its rapid mis-localization to the nucleoplasm following Dis3 loss. Direct detection of EXOSC10 substrates revealed a more specific role in trimming of short 3’ extensions on ribosomal and small nucleolar RNAs. Finally, the 5’-3’ exoribonuclease, Xrn2, has little activity on exosome substrates, but promotes termination following PCPA. Interestingly, Xrn2 is not rate limiting for PROMPT termination providing a distinction between sense and anti-sense transcriptional regulation.
Project description:In our RIP-seq experiment, RNAs were purified from the E12.5 WT mouse cortex. By sequencing of the Exosc10-bound RNAs, binding enrichment of Exosc10 on 3159 transcripts was identified (adjusted p-value < 0.05). GO analysis revealed that the Exosc10-bound transcripts participate in various processes of brain development.
Project description:EXOSC10 is a catalytic subunit of the nuclear RNA exosome with an exoribonuclease activity. The enzyme processes and degrades different classes of RNAs. To delineate the role of EXOSC10 during oocyte growth, specific Exosc10 inactivation was performed in the oocytes from the primordial follicle stage onward using the Gdf9-iCre; Exosc10f/- mouse model (Exosc10cKO(Gdf9)). Exosc10cKO(Gdf9) female mice are infertile. The onset of puberty and the estrus cycle in mutants are initially normal and ovaries contain all follicle classes. By the age of eight weeks, vaginal smears reveal irregular estrus cycles and mutant ovaries display a complete depletion of follicles. Mutant oocytes retrieved from the oviduct are degenerated, sometimes showing an enlarged polar body which may reflect a defective first meiotic division. Under fertilization conditions, the mutant oocytes do not enter into an embryonic development process. Furthermore, we conducted a comparative proteome analysis of wild type and Exosc10 knockout mouse ovaries and identified EXOSC10-dependent proteins involved in many biological processes, such as meiotic cell cycle progression and oocyte maturation. Our results unambiguously demonstrate an essential role for EXOSC10 in oogenesis and may serve as a model for primary ovarian insufficiency in humans.
Project description:Certain organs are capable of containing the replication of various types of viruses. In the liver, infection of Hepatitis B virus (HBV), the etiological factor of Hepatitis B and hepatocellular carcinoma (HCC), often remains asymptomatic and leads to a chronic carrier state. Here we investigated how hepatocytes contain HBV replication and promote their own survival by orchestrating a translational defense mechanism via the stress-sensitive SUMO-2/3-specific peptidase SENP3. We found that SENP3 expression level decreased in HBV-infected hepatocytes in various models including HepG2-NTCP cell lines and a humanized mouse model. Downregulation of SENP3 reduced HBV replication and boosted host protein translation. We also discovered that IQGAP2, a Ras GTPase-activating-like protein, is a key substrate for SENP3-mediated de-SUMOylation. Downregulation of SENP3 in HBV infected cells facilitated IQGAP2 SUMOylation and degradation, which leads to suppression of HBV gene expression and restoration of global translation of host genes via modulation of AKT phosphorylation. Thus, The SENP3-IQGAP2 de-SUMOylation axis is a host defense mechanism of hepatocytes that restores host protein translation and suppresses HBV gene expression.
Project description:Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the ongoing coronavirus disease 2019 (COVID-19) pandemic. Alongside investigations into the virology of SARS-CoV-2, understanding the host–virus dependencies are vital for the identification and rational design of effective antiviral therapy. Here, we report the dominant SARS-CoV-2 entry receptor, ACE2, conjugates with small ubiquitin-like modifier 3 (SUMO3) through a proteome-wide protein interaction analysis. We further demonstrate that E3 SUMO ligase PIAS4 prompts the SUMOylation and stabilization of ACE2, whereas deSUMOylation enzyme SENP3 reverses this process. Conjugation of SUMO3 with ACE2 at lysine (K) 187 hampers the K48-linked ubiquitination of ACE2, thus suppressing its subsequent cargo receptor TOLLIP-dependent autophagic degradation. Pharmacological intervention of ACE2 SUMOylation blocks the entry of SARS-CoV-2 and viral infection-triggered immune responses. Collectively, our findings suggest selective autophagic degradation of ACE2 orchestrated by SUMOylation and ubiquitination can be targeted to future antiviral therapy of SARS-CoV-2.
Project description:To identify changes in gene expression following EXOSC10 and XRN2 silencing, 3'-end RNA-sequencing was performed on RNA extracted from shEXOSC10 and shXRN2 cells.
Project description:Adaptation to hypoxia is mediated through a coordinated transcriptional response driven largely by Hypoxia-Inducible Factor 1 (HIF-1). The direct transcriptional targets of HIF-1 play important roles in facilitating both short-term and long-term adaptation to hypoxia. Alignment of the sequences encompassing all well-characterized HIF-1 binding sites has revealed a consensus core HRE motif of 5'-RCGTG-3' (R = A or G). Since the consensus HIF-1 binding motif is too promiscuous to accurately predict binding a priori, we used ChIP-chip to define HIF-1 chromatin binding on a genome-wide level. We integrated these results with gene expression profiling to interrogate mechanisms regulating hypoxia-induced gene expression, and to more comprehensively identify direct targets of HIF-1 transactivation.