The deubiquitinating protein OTUD6B promotes lung adenocarcinoma progression by stabilizing RIPK1.

BACKGROUND: There is growing evidence indicating that deubiquitinating enzymes may contribute to tumor progression and can serve as promising therapeutic targets. METHODS: The overexpression of deubiquitinase OTUD6B in lung adenocarcinoma (LUAD) and its adjacent tissues was analyzed by immunohistochemistry and TCGA/GO database. Survival analysis further supported OTUD6B as a potential target for LUAD treatment. We assessed the effect of OTUD6B on LUAD cell growth using cell viability assays and conducted TUNEL staining, migration, and invasion experiments to investigate the impact of OTUD6B on the apoptosis and metastasis of LUAD cells. Additionally, we established a transplanted tumor model in nude mice to validate our findings in vivo. Finally, using IP mass spectrometry and co-IP experiments, we screened and confirmed the influence of RIPK1 as a substrate of OTUD6B in LUAD. RESULTS: OTUD6B is highly overexpressed in human LUAD and predicts poor prognosis in LUAD patients. OTUD6B knockdown inhibited the proliferation of LUAD cells and enhanced apoptosis and inhibited metastasis in LUAD cells suppressed. A549 xenografts revealed that OTUD6B deletion can slow down tumour growth. Additionally, OTUD6B can bind to RIPK1, reduce its ubiquitination level and increase its protein stability. CONCLUSIONS: Our results suggest that OTUD6B is a promising clinical target for LUAD treatment and that targeting OTUD6B may constitute an effective anti-LUAD strategy.

A protein sequence-based deep transfer learning framework for identifying human proteome-wide deubiquitinase-substrate interactions.

Protein ubiquitination regulates a wide range of cellular processes. The degree of protein ubiquitination is determined by the delicate balance between ubiquitin ligase (E3)-mediated ubiquitination and deubiquitinase (DUB)-mediated deubiquitination. In comparison to the E3-substrate interactions, the DUB-substrate interactions (DSIs) remain insufficiently investigated. To address this challenge, we introduce a protein sequence-based ab initio method, TransDSI, which transfers proteome-scale evolutionary information to predict unknown DSIs despite inadequate training datasets. An explainable module is integrated to suggest the critical protein regions for DSIs while predicting DSIs. TransDSI outperforms multiple machine learning strategies against both cross-validation and independent test. Two predicted DUBs (USP11 and USP20) for FOXP3 are validated by "wet lab" experiments, along with two predicted substrates (AR and p53) for USP22. TransDSI provides new functional perspective on proteins by identifying regulatory DSIs, and offers clues for potential tumor drug target discovery and precision drug application.

OTUD1 enhances gastric cancer aggressiveness by deubiquitinating EBV-encoded protein BALF1 to stabilize the apoptosis inhibitor Bcl-2.

The Epstein-Barr virus (EBV) is implicated in several cancers, including EBV-associated gastric cancer (EBVaGC). This study focuses on EBV-encoded BALF1 (BamH1 A fragment leftward reading frame 1), a key apoptosis regulator in EBV-related cancers, whose specific impact on EBVaGC was previously unknown. Our findings indicate that BALF1 overexpression in gastric cancer cells significantly enhances their proliferation, migration, and resistance to chemotherapy-induced apoptosis, confirming BALF1's oncogenic potential. A novel discovery is that BALF1 undergoes degradation via the ubiquitin-proteasome pathway. Through analysis of 69 deubiquitinating enzymes (DUBs), ovarian tumor protease (OTU) domain-containing protein 1 (OTUD1) emerged as a vital regulator for maintaining BALF1 protein stability. Furthermore, BALF1 was found to play a role in regulating the stability of the B-cell lymphoma-2 (Bcl-2) protein, increasing its levels through deubiquitination. This mechanism reveals BALF1's multifaceted oncogenic role in gastric cancer, as it contributes both directly and indirectly to cancer progression, particularly by stabilizing Bcl-2, known for its anti-apoptotic characteristics. These insights significantly deepen our understanding of EBV's involvement in the pathogenesis of gastric cancer. The elucidation of OTUD1's role in BALF1 regulation and its influence on Bcl-2 stabilization provide new avenues for therapeutic intervention in EBVaGC, bridging the gap between viral oncogenesis and cellular protein regulation and offering a more holistic view of gastric cancer development under the influence of EBV.

Viral deubiquitinating proteases and the promising strategies of their inhibition.

Several viruses are now known to code for deubiquitinating proteases in their genomes. Ubiquitination is an essential post-translational modification of cellular substrates involved in many processes in the cell, including in innate immune signalling. This post-translational modification is regulated by the ubiquitin conjugation machinery, as well as various host deubiquitinating enzymes. The conjugation of ubiquitin chains to several innate immune related factors is often needed to induce downstream signalling, shaping the antiviral response. Viral deubiquitinating proteins, besides often having a primary function in the viral replication cycle by cleaving the viral polyprotein, are also able to cleave ubiquitin chains from such host substrates, in that way exerting a function in innate immune evasion. The presence of viral deubiquitinating enzymes has been firmly established for numerous animal-infecting viruses, such as some well-researched and clinically important nidoviruses, and their presence has now been confirmed in several plant viruses as well. Viral proteases in general have long been highlighted as promising drug targets, with a current focus on small molecule inhibitors. In this review, we will discuss the range of viral deubiquitinating proteases known to date, summarise the various avenues explored to inhibit such proteases and discuss novel strategies and models intended to inhibit and study these specific viral enzymes.

OTUD5 promotes the growth of hepatocellular carcinoma by deubiquitinating and stabilizing SLC38A1.

BACKGROUND: Deubiquitinating enzymes (DUBs) cleave ubiquitin on substrate molecules to maintain protein stability. DUBs reportedly participate in the tumorigenesis and tumour progression of hepatocellular carcinoma (HCC). OTU deubiquitinase 5 (OTUD5), a DUB family member, has been recognized as a critical regulator in bladder cancer, breast cancer and HCC. However, the expression and biological function of OTUD5 in HCC are still controversial. RESULTS: We determined that the expression of OTUD5 was significantly upregulated in HCC tissues. High levels of OTUD5 were also detected in most HCC cell lines. TCGA data analysis demonstrated that high OTUD5 expression indicated poorer overall survival in HCC patients. OTUD5 silencing prominently suppressed HCC cell proliferation, while its overexpression markedly enhanced the proliferation of HCC cells. Mass spectrometry analysis revealed solute carrier family 38 member 1 (SLC38A1) as a candidate downstream target protein of OTUD5. Coimmunoprecipitation analysis confirmed the interaction between OTUD5 and SLC38A1. OTUD5 knockdown reduced and OTUD5 overexpression increased SLC38A1 protein levels in HCC cells. However, OTUD5 alteration had no effect on SLC38A1 mRNA expression. OTUD5 maintained SLC38A1 stability by preventing its ubiquitin-mediated proteasomal degradation. SLC38A1 silencing prominently attenuated the OTUD5-induced increase in HCC cell proliferation. Finally, OTUD5 knockdown markedly suppressed the growth of HCC cells in vivo. CONCLUSIONS: OTUD5 is an oncogene in HCC. OTUD5 contributes to HCC cell proliferation by deubiquitinating and stabilizing SLC38A1. These results may provide a theoretical basis for the development of new anti-HCC drugs.

Deubiquitination of CDC6 by OTUD6A promotes tumour progression and chemoresistance.

BACKGROUND: CDC6 is an oncogenic protein whose expression level fluctuates during the cell cycle. Although several E3 ubiquitin ligases responsible for the ubiquitin-mediated proteolysis of CDC6 have been identified, the deubiquitination pathway for CDC6 has not been investigated. METHODS: The proteome-wide deubiquitinase (DUB) screening was used to identify the potential regulator of CDC6. Immunofluorescence, protein half-life and deubiquitination assays were performed to determine the protein stability of CDC6. Gain- and loss-of-function experiments were implemented to analyse the impacts of OUTD6A-CDC6 axis on tumour growth and chemosensitivity in vitro. N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced conditional Otud6a knockout (CKO) mouse model and tumour xenograft model were performed to analyse the role of OTUD6A-CDC6 axis in vivo. Tissue specimens were used to determine the association between OTUD6A and CDC6. RESULTS: OTUD6A interacts with, depolyubiquitinates and stabilizes CDC6 by removing K6-, K33-, and K48-linked polyubiquitination. Moreover, OTUD6A promotes cell proliferation and decreases sensitivity to chemotherapy by upregulating CDC6. CKO mice are less prone to BCa tumorigenesis induced by BBN, and knockdown of OTUD6A inhibits tumour progression in vivo. Furthermore, OTUD6A protein level has a positive correlation with CDC6 protein level, and high protein levels of OTUD6A and CDC6 are associated with poor prognosis in patients with bladder cancer. CONCLUSIONS: We reveal an important yet missing piece of novel DUB governing CDC6 stability. In addition, our findings propose a model for the OTUD6A-CDC6 axis that provides novel insights into cell cycle and chemosensitivity regulation, which may become a potential biomarker and promising drug target for cancer treatment.

Deubiquitinase BRCC3 promotes the migration, invasion and EMT progression of colon adenocarcinoma by stabilizing MET expression.

BACKGROUND: Breast cancer type 1 susceptibility protein/breast cancer type 2 susceptibility protein-containing complex subunit 3 (BRCC3), a deubiquitinase (DUBs), is overexpressed in various cancers. However, the underlying biological roles of BRCC3 in adenocarcinoma colon (COAD) have yet to be decrypted. OBJECTIVE: In this work, we explored the potential biological function of BRCC3 in the natural process of COAD cells. METHODS: The expression levels of BRCC3 in COAD tissues and cell lines were investigated via quantitative real time polymerase chain reaction and western blotting analyses. Meanwhile, short hairpin RNAs targeting BRCC3 (sh-BRCC3) or mesenchymal-epithelial transition factor (MET) (sh-MET) were used to investigate the biological function, including proliferation, apoptosis, migration, invasion, and epithelial-mesenchymal transition (EMT) progression in COAD cells. Furthermore, the expression levels of EMT-related biomarkers were detected with western blotting analysis. Furthermore, we also performed Co-IP assay to identify the correlation between BRCC3 and MET. RESULTS: BRCC3 expression was increased in COAD tissues and cell lines. ShRNA-mediated downmodulation of BRCC3 in COAD cell lines induced EMT progression. BRCC3 knockdown resulted in decreased migration as well as invasion and increased apoptosis of SW480 and Lovo cells. Besides, MET was regulated by BRCC3 and involved in the migration, invasion, and EMT in SW480 and Lovo cells. Finally, we uncovered that the overexpressed MET reversed the effects of BRCC3 knockdown in COAD cell development. CONCLUSIONS: BRCC3 acted as a critical factor in the development of COAD by deubiquitinating and stabilizing MET, which might provide an emerging biomarker for the therapeutic and diagnosis strategy of COAD.

The deubiquitinase BRCC3 increases the stability of ZEB1 and promotes the proliferation and metastasis of triple-negative breast cancer cells.

Triple negative breast cancer (TNBC) has a high recurrence rate, metastasis rate and mortality rate. The aim of this study is to identify new targets for the treatment of TNBC. Clinical samples are used for screening deubiquitinating enzymes (DUBs). MDA-MB-231 cells and a TNBC mouse model are used for in vitro and in vivo experiments, respectively. Western blot analysis is used to detect the protein expressions of DUBs, zinc finger E-box binding homeobox 1 (ZEB1), and epithelial-mesenchymal transition (EMT)-related markers. Colony formation and transwell assays are used to detect the proliferation, migration and invasion of TNBC cells. Wound healing assay is used to detect the mobility of TNBC cells. Immunoprecipitation assay is used to detect the interaction between breast cancer susceptibility gene 1/2-containing complex subunit 3 (BRCC3) and ZEB1. ZEB1 ubiquitination levels, protein stability, and protein degradation are also examined. Pathological changes in the lung tissues are detected via HE staining. Our results show a significant positive correlation between the expressions of BRCC3 and ZEB1 in clinical TNBC tissues. Interference with BRCC3 inhibits TNBC cell proliferation, migration, invasion and EMT. BRCC3 interacts with ZEB1 and interferes with BRCC3 to inhibit ZEB1 expression by increasing ZEB1 ubiquitination. Interference with BRCC3 inhibits TNBC cell tumorigenesis and lung metastasis in vivo. In all, this study demonstrates that BRCC3 can increase the stability of ZEB1, upregulate ZEB1 expression, and promote the proliferation, migration, invasion, EMT, and metastasis of TNBC cells, providing a new direction for cancer therapy.

YTHDF2 protein stabilization by the deubiquitinase OTUB1 promotes prostate cancer cell proliferation via PRSS8 mRNA degradation.

Prostate cancer is a leading cause of cancer-related mortality in males. Dysregulation of RNA adenine N-6 methylation (m6A) contributes to cancer malignancy. m6A on mRNA may affect mRNA splicing, turnover, transportation, and translation. m6A exerts these effects, at least partly, through dedicated m6A reader proteins, including YTH domain-containing family protein 2 (YTHDF2). YTHDF2 is necessary for development while its dysregulation is seen in various cancers, including prostate cancer. However, the mechanism underlying the dysregulation and function of YTHDF2 in cancer remains elusive. Here, we find that the deubiquitinase OUT domain-containing ubiquitin aldehyde-binding protein 1 (OTUB1) increases YTHDF2 protein stability by inhibiting its ubiquitination. With in vivo and in vitro ubiquitination assays, OTUB1 is shown to block ubiquitin transfer to YTHDF2 independent of its deubiquitinase activity. Furthermore, analysis of functional transcriptomic data and m6A-sequencing data identifies PRSS8 as a potential tumor suppressor gene. OTUB1 and YTHDF2 decrease mRNA and protein levels of PRSS8, which is a trypsin-like serine protease. Mechanistically, YTHDF2 binds PRSS8 mRNA and promotes its degradation in an m6A-dependent manner. Further functional study on cellular and mouse models reveals PRSS8 is a critical downstream effector of the OTUB1-YTHDF2 axis in prostate cancer. We find in prostate cancer cells, PRSS8 decreases nuclear ß-catenin level through E-cadherin, which is independent of its protease activity. Collectively, our study uncovers a key regulator of YTHDF2 protein stability and establishes a functional OTUB1-YTHDF2-PRSS8 axis in prostate cancer.

Relevance of mutations in protein deubiquitinases genes and TP53 in corticotroph pituitary tumors.

Introduction: Corticotroph pituitary neuroendocrine tumors (PitNETs) develop from ACTH-producing cells. They commonly cause Cushing's disease (CD), however, some remain clinically silent. Recurrent USP8, USP48, BRAF and TP53 mutations occur in corticotroph PitNETs. The aim of our study was to determine frequency and relevance of these mutations in a possibly large series of corticotroph PitNETs. Methods: Study included 147 patients (100 CD and 47 silent tumors) that were screened for hot-spot mutations in USP8, USP48 and BRAF with Sanger sequencing, while 128 of these patients were screened for TP53 mutations with next generation sequencing and immunohistochemistry. Results: USP8 mutations were found in 41% CD and 8,5% silent tumors, while USP48 mutations were found in 6% CD patients only. Both were more prevalent in women. They were related to higher rate of biochemical remission, non-invasive tumor growth, its smaller size and densely granulated histology, suggesting that these mutation may be favorable clinical features. Multivariate survival analyses did not confirm possible prognostic value of mutation in protein deubiquitinases. No BRAF mutations were found. Four TP53 mutations were identified (2 in CD, 2 in silent tumors) in tumors with size >10mm including 3 invasive ones. They were found in Crooke's cell and sparsely granulated tumors. Tumors with missense TP53 mutations had higher TP53 immunoreactivity score than wild-type tumors. Tumor with frameshift TP53 variant had low protein expression. TP53 mutation was a poor prognostic factor in CD according to uni- and multivariate survival analyses in spite of low mutations frequency. Conclusions: We confirmed high prevalence of USP8 mutations and low incidence of USP48 and TP53 mutations. Changes in protein deubiquitinases genes appear to be favorable prognostic factors in CD. TP53 mutations are rare, occur in both functioning and silent tumors and are related to poor clinical outcome in CD.

Role of deubiquitinase JOSD2 in the pathogenesis of esophageal squamous cell carcinoma.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) is a deadly malignancy with limited treatment options. Deubiquitinases (DUBs) have been confirmed to play a crucial role in the development of malignant tumors. JOSD2 is a DUB involved in controlling protein deubiquitination and influencing critical cellular processes in cancer. AIM: To investigate the impact of JOSD2 on the progression of ESCC. METHODS: Bioinformatic analyses were employed to explore the expression, prognosis, and enriched pathways associated with JOSD2 in ESCC. Lentiviral transduction was utilized to manipulate JOSD2 expression in ESCC cell lines (KYSE30 and KYSE150). Functional assays, including cell proliferation, colony formation, drug sensitivity, migration, and invasion, were performed, revealing the impact of JOSD2 on ESCC cell lines. JOSD2's role in xenograft tumor growth and drug sensitivity in vivo was also assessed. The proteins that interacted with JOSD2 were identified using mass spectrometry. RESULTS: Preliminary research indicated that JOSD2 was highly expressed in ESCC tissues, which was associated with poor prognosis. Further analysis demonstrated that JOSD2 was upregulated in ESCC cell lines compared to normal esophageal cells. JOSD2 knockdown inhibited ESCC cell activity, including proliferation and colony-forming ability. Moreover, JOSD2 knockdown decreased the drug resistance and migration of ESCC cells, while JOSD2 overexpression enhanced these phenotypes. In vivo xenograft assays further confirmed that JOSD2 promoted tumor proliferation and drug resistance in ESCC. Mechanistically, JOSD2 appears to activate the MAPK/ERK and PI3K/AKT signaling pathways. Mass spectrometry was used to identify crucial substrate proteins that interact with JOSD2, which identified the four primary proteins that bind to JOSD2, namely USP47, IGKV2D-29, HSP90AB1, and PRMT5. CONCLUSION: JOSD2 plays a crucial role in enhancing the proliferation, migration, and drug resistance of ESCC, suggesting that JOSD2 is a potential therapeutic target in ESCC.

Deubiquitinase USP4 suppresses antitumor immunity by inhibiting IRF3 activation and tumor cell-intrinsic interferon response in colorectal cancer.

Despite the approval of immune checkpoint blockade (ICB) therapy for various tumor types, its effectiveness is limited to only approximately 15% of patients with microsatellite instability-high (MSI-H) or mismatch repair deficiency (dMMR) colorectal cancer (CRC). Approximately 80%-85% of CRC patients have a microsatellite stability (MSS) phenotype, which features a rare T-cell infiltration. Thus, elucidating the mechanisms underlying resistance to ICB in patients with MSS CRC is imperative. In this study, we demonstrate that ubiquitin-specific peptidase 4 (USP4) is upregulated in MSS CRC tumors and negatively regulates the immune response against tumors in CRC. Additionally, USP4 represses the cellular interferon (IFN) response and antigen presentation and impairs PRR signaling-mediated cell death. Mechanistically, USP4 impedes the nuclear localization of interferon regulator Factor 3 (IRF3) by deubiquitinating the K63-polyubiquitin chain of TRAF6 and IRF3. Knockdown of USP4 enhances the infiltration of T cells in CRC tumors and overcomes ICB resistance in an MC38 syngeneic mouse model. Moreover, published datasets revealed that patients showing higher USP4 expression exhibited decreased responsiveness to anti-PD-L1 therapy. These findings highlight an essential role of USP4 in the suppression of antitumor immunity in CRC.

Josephin domain containing 2 (JOSD2) promotes lung cancer by inhibiting LKB1 (Liver kinase B1) activity.

Non-small cell lung cancer (NSCLC) ranks as one of the leading causes of cancer-related deaths worldwide. Despite the prominence and effectiveness of kinase-target therapies in NSCLC treatment, these drugs are suitable for and beneficial to a mere ~30% of NSCLC patients. Consequently, the need for novel strategies addressing NSCLC remains pressing. Deubiquitinases (DUBs), a group of diverse enzymes with well-defined catalytic sites that are frequently overactivated in cancers and associated with tumorigenesis and regarded as promising therapeutic targets. Nevertheless, the mechanisms by which DUBs promote NSCLC remain poorly understood. Through a global analysis of the 97 DUBs' contribution to NSCLC survival possibilities using The Cancer Genome Atlas (TCGA) database, we found that high expression of Josephin Domain-containing protein 2 (JOSD2) predicted the poor prognosis of patients. Depletion of JOSD2 significantly impeded NSCLC growth in both cell/patient-derived xenografts in vivo. Mechanically, we found that JOSD2 restricts the kinase activity of LKB1, an important tumor suppressor generally inactivated in NSCLC, by removing K6-linked polyubiquitination, an action vital for maintaining the integrity of the LKB1-STRAD-MO25 complex. Notably, we identified the first small-molecule inhibitor of JOSD2, and observed that its pharmacological inhibition significantly arrested NSCLC proliferation in vitro/in vivo. Our findings highlight the vital role of JOSD2 in hindering LKB1 activity, underscoring the therapeutic potential of targeting JOSD2 in NSCLC, especially in those with inactivated LKB1, and presenting its inhibitors as a promising strategy for NSCLC treatment.

The dimeric deubiquitinase USP28 integrates 53BP1 and MYC functions to limit DNA damage.

DNA replication is a major source of endogenous DNA damage in tumor cells and a key target of cellular response to genotoxic stress. DNA replication can be deregulated by oncoproteins, such as transcription factor MYC, aberrantly activated in many human cancers. MYC is stringently regulated by the ubiquitin system - for example, ubiquitination controls recruitment of the elongation factor PAF1c, instrumental in MYC activity. Curiously, a key MYC-targeting deubiquitinase USP28 also controls cellular response to DNA damage via the mediator protein 53BP1. USP28 forms stable dimers, but the biological role of USP28 dimerization is unknown. We show here that dimerization limits USP28 activity and restricts recruitment of PAF1c by MYC. Expression of monomeric USP28 stabilizes MYC and promotes PAF1c recruitment, leading to ectopic DNA synthesis and replication-associated DNA damage. USP28 dimerization is stimulated by 53BP1, which selectively binds USP28 dimers. Genotoxic stress diminishes 53BP1-USP28 interaction, promotes disassembly of USP28 dimers and stimulates PAF1c recruitment by MYC. This triggers firing of DNA replication origins during early response to genotoxins and exacerbates DNA damage. We propose that dimerization of USP28 prevents ectopic DNA replication at transcriptionally active chromatin to maintain genome stability.

Identification and Analysis of Subtypes of Liver Cancer Based on Genes Related to E3 Ubiquitin Ligases and Deubiquitinating Enzymes.

Recent studies have reported a correlation between ubiquitination or deubiquitination and cancer development. But mechanisms underlying the roles of genes associated with E3 ubiquitin ligases and deubiquitinating enzymes (DUB) in liver cancer remain to be explored. We analyzed and screened differentially expressed genes related to E3 ubiquitin ligases and DUB in liver cancer on the basis of public databases. Cluster analysis was utilized to classify liver cancer samples into different subtypes. Survival analysis, immune analysis, and pathway enrichment analysis were performed on the subtypes. We constructed a protein-protein interaction network using STRING to screen hub genes. Finally, we used the Connectivity Map (CMap) database to predict targeted small molecules. The results show that a total of 139 differentially expressed E3/DUB genes in liver cancer were screened. Then, liver cancer was classified into two subtypes, cluster 1 and cluster 2, based on E3-related and DUB-related genes. Patients in cluster 1 had higher survival rates and immune levels than those in cluster 2. Four hub genes (RPSA, RPS5, RPL30, and RPL8) significantly affecting the survival of the two subtypes of liver cancer patients were identified based on cluster 1 and cluster 2. Finally, the CMap database predicted that small-molecule drugs including probenecid, dexamethasone, and etomidate may improve the prognosis of liver cancer patients. These findings may offer a reference for risk stratification studies and drug development in liver cancer.

Deubiquitinating enzyme PSMD7 promotes bladder cancer development: Involvement of RAB1A stabilization.

BACKGROUND: Proteasome 26S subunit, non-ATPase 7 (PSMD7) is a deubiquitinating enzyme that is involved in the stability of ubiquitinated proteins and participates in the development of multiple types of cancer. The roles of PSMD7 and its potential mechanisms in bladder cancer (BC) remain elusive. METHODS: In this study, we identified that PSMD7 was overexpressed in BC tissues based on gene expression omnibus (GEO) database and TNMplot web. To investigate the functional role of PSMD7, two BC cell lines, T24 and 5637, were selected. The cells were transfected with vectors containing short hairpin RNAs against PSMD7 or plasmids containing full-length PSMD7 to knockdown or overexpress PSMD7. RESULTS: Our results revealed that silencing PSMD7 inhibited cell proliferation, cycle progression, migration, invasion, and promoted cell apoptosis, whereas PSMD7 overexpression led to the opposite effects in the BC cells. Mechanically, PSMD7 influenced the protein expression but not the mRNA expression of the Ras-related protein Rab-1 A (RAB1A). PSMD7 combined with RAB1A and negatively regulated its ubiquitination, indicating that PSMD7 enhanced the stability of RAB1A through post-transcriptional modification. Moreover, the rescue experiment demonstrated that RAB1A was an important downstream effector molecule of PSMD7. Besides, the negative regulation of silencing PSMD7 on tumor growth was confirmed in mice. CONCLUSIONS: Our study substantiated a novel mechanism by which PSMD7 stabilized RAB1A to accelerate the progression of BC.

PSMD14 stabilizes estrogen signaling and facilitates breast cancer progression via deubiquitinating ERα.

The over-activation of ERα signaling is regarded as the major driver for luminal breast cancers, which could be effective controlled via selective estrogen receptor modulators (SERM), such as tamoxifen. The endocrine resistance is still a challenge for breast cancer treatment, while recently studies implicate the post-translational modification on ERα play important roles in endocrine resistance. The stability of ERα protein and ERα transcriptome are subject to a balance between E3 ubiquitin ligases and deubiquitinases. Through deubiquitinases siRNA library screening, we discover PSMD14 as a critical deubiquitinase for ERα signaling and breast cancer progression. PSMD14 could facilitate breast cancer progression through ERα signaling in vitro and in vivo, while pharmaceutical inhibition of PSMD14 via Thiolutin could block the tumorigenesis in breast cancer. In endocrine resistant models, PSMD14 inhibition could de-stabilize the resistant form of ERα (Y537S) and restore tamoxifen sensitivity. Molecular studies reveal that PSMD14 could inhibition K48-linked poly-ubiquitination on ERα, facilitate ERα transcriptome. Interestingly, ChIP assay shows that ERα could bind to the promoter region of PSMD14 and facilitate its gene transcription, which indicates PSMD14 is both the upstream modulator and downstream target for ERα signaling in breast cancer. In general, we identified a novel positive feedback loop between PSMD14 and ERα signaling in breast cancer progression, while blockade of PSMD14 could be a plausible strategy for luminal breast cancer.

Deubiquitylating Enzymes in Cancer and Immunity.

Deubiquitylating enzymes (DUBs) maintain relative homeostasis of the cellular ubiquitome by removing the post-translational modification ubiquitin moiety from substrates. Numerous DUBs have been demonstrated specificity for cleaving a certain type of ubiquitin linkage or positions within ubiquitin chains. Moreover, several DUBs perform functions through specific protein-protein interactions in a catalytically independent manner, which further expands the versatility and complexity of DUBs' functions. Dysregulation of DUBs disrupts the dynamic equilibrium of ubiquitome and causes various diseases, especially cancer and immune disorders. This review summarizes the Janus-faced roles of DUBs in cancer including proteasomal degradation, DNA repair, apoptosis, and tumor metastasis, as well as in immunity involving innate immune receptor signaling and inflammatory and autoimmune disorders. The prospects and challenges for the clinical development of DUB inhibitors are further discussed. The review provides a comprehensive understanding of the multi-faced roles of DUBs in cancer and immunity.

Deubiquitinase OTUD5 promotes hepatitis B virus replication by removing K48-linked ubiquitination of HBV core/precore and upregulates HNF4ɑ expressions by inhibiting the ERK1/2/mitogen-activated protein kinase pathway.

Hepatitis B virus (HBV) infection is a major public health problem worldwide, causing nearly one million deaths annually. OTUD5 is a deubiquitinase associated with cancer development and innate immunity response. However, the regulatory mechanisms of OTUD5 underlying HBV replication need to be deeply elucidated. In the present investigation, we found that HBV induced significant up-regulation of OTUD5 protein in HBV-infected cells. Further study showed that OTUD5 interacted with HBV core/precore, removing their K48-linked ubiquitination chains and protecting their stability. Meanwhile, overexpression of OTUD5 could inhibit the MAPK pathway and then increase the expression of HNF4ɑ, and ERK1/2 signaling was required for OTUD5-mediated activation of HNF4α, promoting HBV replication. Together, these data indicate that OTUD5 could deubiquitinate HBV core protein degradation by its deubiquitinase function and promote HBV activity by up-regulating HNF4α expression via inhibition of the ERK1/2 pathway. These results might present a novel therapeutic strategy against HBV infection.

GSE1 links the HDAC1/CoREST co-repressor complex to DNA damage.

Post-translational modifications of histones are important regulators of the DNA damage response (DDR). By using affinity purification mass spectrometry (AP-MS) we discovered that genetic suppressor element 1 (GSE1) forms a complex with the HDAC1/CoREST deacetylase/demethylase co-repressor complex. In-depth phosphorylome analysis revealed that loss of GSE1 results in impaired DDR, ATR signalling and γH2AX formation upon DNA damage induction. Altered profiles of ATR target serine-glutamine motifs (SQ) on DDR-related hallmark proteins point to a defect in DNA damage sensing. In addition, GSE1 knock-out cells show hampered DNA damage-induced phosphorylation on SQ motifs of regulators of histone post-translational modifications, suggesting altered histone modification. While loss of GSE1 does not affect the histone deacetylation activity of CoREST, GSE1 appears to be essential for binding of the deubiquitinase USP22 to CoREST and for the deubiquitination of H2B K120 in response to DNA damage. The combination of deacetylase, demethylase, and deubiquitinase activity makes the USP22-GSE1-CoREST subcomplex a multi-enzymatic eraser that seems to play an important role during DDR. Since GSE1 has been previously associated with cancer progression and survival our findings are potentially of high medical relevance.