The deubiquitinase USP16 functions as an oncogenic factor in K-RAS-driven lung tumorigenesis

Roles of deubiquitinases in urologic cancers (Review)

Human health is endangered by the occurrence and progression of urological cancers, including renal cell carcinoma, prostate cancer and bladder cancer, which are usually associated with the activation of oncogenic factors and inhibition of cancer suppressors. The primary mechanism for protein breakdown in cells is the ubiquitin-proteasome system, whilst deubiquitinases contribute to the reversal of this process. However, both are important for protein homeostasis. Deubiquitination may also be involved in the control of the cell cycle, proliferation and apoptosis, and dysregulated deubiquitination is associated with the malignant transformation, invasion and metastasis of urologic malignancies. Therefore, a comprehensive summary of the mechanisms underlying deubiquitination in urological cancers may provide novel strategies and insights for diagnosis and treatment. The present review aimed to methodically clarify the role of deubiquitinating enzymes in urinary system cancers as well as their prospective application prospects for clinical treatment.

USP24 promotes autophagy-dependent ferroptosis in hepatocellular carcinoma by reducing the K48-linked ubiquitination of Beclin1

Ubiquitination is a post-translational modification (PTM), which is critical to maintain cell homeostasis. Ubiquitin-specific protease 24 (USP24) plays roles in various diseases, the mechanisms by which USP24 regulates hepatocellular carcinoma (HCC) remain poorly understood. In this study, USP24 is found to be significantly downregulated in HCC. Knocking down USP24 promotes HCC proliferation and migration, whereas USP24 overexpression inhibits HCC in vitro and in vivo. The endogenous interaction between USP24 and Beclin1 is confirmed. Mechanically, USP24 delays Beclin1 degradation by reducing its K48-linked ubiquitination, the effects of overexpressing USP24 on HCC proliferation can be partially reversed by silencing Beclin1. We find that increased autophagy is accompanied by ferroptosis in USP24 overexpressed HCC cells and USP24 increases the susceptibility of HCC to sorafenib. Collectively, this study highlights the critical role of USP24 in regulating autophagy-dependent ferroptosis by decreasing Beclin1 ubiquitination, suggesting that targeting USP24 may be a strategy for treating HCC.

O-GlcNAcylation stimulates the deubiquitination activity of USP16 and regulates cell cycle progression

Histone 2A monoubiquitination (uH2A) underscores a key epigenetic regulation of gene expression. In this report, we show that the deubiquitinase for uH2A, ubiquitin-specific peptidase 16 (USP16), is modified by O-linked N-acetylglucosamine (O-GlcNAc). O-GlcNAcylation involves the installation of the O-GlcNAc moiety to Ser/Thr residues. It crosstalks with Ser/Thr phosphorylation, affects protein-protein interaction, alters enzyme activity or protein folding, and changes protein subcellular localization. In our study, we first confirmed that USP16 is glycosylated on Thr203 and Ser214, as reported in a previous chemoenzymatic screen. We then discovered that mutation of the O-GlcNAcylation site Thr203, which is adjacent to deubiquitination-required Cys204, reduces the deubiquitination activity toward H2AK119ub in vitro and in cells, while mutation on Ser214 had the opposite effects. Using USP16 Ser552 phosphorylation-specific antibodies, we demonstrated that O-GlcNAcylation antagonizes cyclin-dependent kinase 1-mediated phosphorylation and promotes USP16 nuclear export. O-GlcNAcylation of USP16 is also required for deubiquitination of Polo-like kinase 1, a mitotic master kinase, and the subsequent chromosome segregation and cytokinesis. In summary, our study revealed that O-GlcNAcylation of USP16 at Thr203 and Ser214 coordinates deubiquitination of uH2A and Polo-like kinase 1, thus ensuring proper cell cycle progression.

USP10 promotes migration and cisplatin resistance in esophageal squamous cell carcinoma cells

Cisplatin-based chemotherapy is the main treatment option for advanced or metastatic esophageal squamous cell carcinoma (ESCC). However, most ESCC patients develop drug resistance within 2 years after receiving cisplatin chemotherapy. Ubiquitin-specific protease 10 (USP10) is abnormally expressed in a variety of cancers, but the mechanistic roles of USP10 in ESCC are still obscure. Here, the effects of USP10 on the migration and cisplatin resistance of ESCC in vivo and in vitro and the underlying mechanisms have been investigated by bioinformatics analysis, RT-PCR, western blotting, immunoprecipitation, immunohistochemistry, cell migration and MTS cell proliferation assays, deubiquitination assay, and mouse tail vein injection model. USP10 was significantly up-regulated in ESCC tissues compared with adjacent normal tissues in both public databases and clinical samples and was closely associated with overall survival. Subsequent results revealed that USP10 contributed to the migration and cisplatin resistance of ESCC cells, while knocking down USP10 in cisplatin-resistant cells exhibited opposite effects in vitro and in vivo. Further Co-IP experiments showed that integrin β1 and YAP might be targets for USP10 deubiquitination. Moreover, deficiency of USP10 significantly inhibited the migrative and chemo-resistant abilities of ESCC cells, which could be majorly reversed by integrin β1 or YAP reconstitution. Altogether, USP10 was required for migration and cisplatin resistance in ESCC through deubiquinating and stabilizing integrin β1/YAP, highlighting that inhibition of USP10 may be a potential therapeutic strategy for ESCC.

The Pleiotropic Ubiquitin-Specific Peptidase 16 and Its Many Substrates

Ubiquitin-specific peptidase 16 (USP16) is a deubiquitinase that plays a role in the regulation of gene expression, cell cycle progression, and various other functions. It was originally identified as the major deubiquitinase for histone H2A and has since been found to deubiquitinate a range of other substrates, including proteins from both the cytoplasm and nucleus. USP16 is phosphorylated when cells enter mitosis and dephosphorylated during the metaphase/anaphase transition. While much of USP16 is localized in the cytoplasm, separating the enzyme from its substrates is considered an important regulatory mechanism. Some of the functions that USP16 has been linked to include DNA damage repair, immune disease, tumorigenesis, protein synthesis, coronary artery health, and male infertility. The strong connection to immune response and the fact that multiple oncogene products are substrates of USP16 suggests that USP16 may be a potential therapeutic target for the treatment of certain human diseases.

Critical role of lncEPAT in coupling dysregulated EGFR pathway and histone H2A deubiquitination during glioblastoma tumorigenesis

Histone 2A (H2A) monoubiquitination is a fundamental epigenetics mechanism of gene expression, which plays a critical role in regulating cell fate. However, it is unknown if H2A ubiquitination is involved in EGFR-driven tumorigenesis. In the current study, we have characterized a previously unidentified oncogenic lncRNA (lncEPAT) that mediates the integration of the dysregulated EGFR pathway with H2A deubiquitination in tumorigenesis. LncEPAT was induced by the EGFR pathway, and high-level lncEPAT expression positively correlated with the glioma grade and predicted poor survival of glioma patients. Mass spectrometry analyses revealed that lncEPAT specifically interacted with deubiquitinase USP16. LncEPAT inhibited USP16's recruitment to chromatin, thereby blocking USP16-mediated H2A deubiquitination and repressing target gene expression, including CDKN1A and CLUSTERIN. Depletion of lncEPAT promoted USP16-induced cell cycle arrest and cellular senescence, and then repressed GBM cell tumorigenesis. Thus, the EGFR-lncEPAT-ubH2A coupling represents a previously unidentified mechanism for epigenetic gene regulation and senescence resistance during GBM tumorigenesis.