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In ovarian cancer patients, the 5-year survival rate is 90% for stages I and II, but only 30% for stages III and IV. Unfortunately, as 75% of the patients are diagnosed at stages III and IV, many experience a recurrence. To ameliorate this, it is necessary to develop new biomarkers for early diagnosis and treatment. The ubiquitin–proteasome system is a post-translational modification that plays an important role in regulating protein stability through ubiquitination. In particular, deubiquitinating enzymes (DUBs) regulate protein stability through deubiquitinating substrate proteins. In this review, DUBs and substrates regulated by these enzymes are summarized based on their functions in ovarian cancer cells. This would be useful for the discovery of biomarkers for ovarian cancer and developing new therapeutic candidates. [ABSTRACT FROM AUTHOR]

The CDC73/HRPT2 gene, a defect which causes hyperparathyroidism–jaw tumor (HPT-JT) syndrome, encodes CDC73/parafibromin. We aimed to investigate whether CDC73 would be a target for ubiquitin–proteasome degradation. We cloned full-length cDNAs encoding a family of 58 ubiquitin-specific deubiquitinating enzymes (DUBs), also known as ubiquitin-specific proteases (USPs). Use of the yeast two-hybrid system then enabled us to identify USP37 as interacting with CDC73. The biochemical interaction between the USP37 and CDC73 and their reciprocal binding domains were studied. Co-localization of CDC73 and USP37 was observed in cells. CDC73 was found to be polyubiquitinated, and polyubiquitination of CDC73 was prominent in mutants. CDC73 was deubiquitinated via K48-specific ubiquitin chains by USP37, but not by the catalytically inactive USP37C350S mutant. Observation of the binding between deletion mutants of CDC73 and USP37 revealed that the β-catenin binding site of CDC73 and the ubiquitin-interacting motifs 2 and 3 (UIM2 and 3) of USP37 were responsible for the interaction between the two proteins. Moreover, these two enzymes co-existed within the nucleus of COS7 cells. We conclude that USP37 is a DUB for CDC73 and that the two proteins interact through specific domains, suggesting that USP37 is responsible for the stability of CDC73 in HPT-JT syndrome. [ABSTRACT FROM AUTHOR]

Deubiquitinating enzymes (DUBs) play an important role in the ubiquitin‐proteasome system (UPS) by eliminating ubiquitins from substrates and inhibiting proteasomal degradation. Protein phosphatase methylesterase 1 (PME‐1) inactivates protein phosphatase 2A (PP2A) and enhances the ERK and Akt signaling pathways, which increase cell proliferation and malignant cell transformation. In this study, we demonstrate that USP36 regulates PME‐1 through its deubiquitinating enzyme activity. USP36 increases PME‐1 stability, and depletion of USP36 decreases the PME‐1 expression level. Furthermore, we demonstrate that USP36 promotes the ERK and Akt signaling pathways. In summary, it is suggested that USP36 regulates PME‐1 as a DUB and participates in the ERK and Akt signaling pathways. [ABSTRACT FROM AUTHOR]

RNA-binding protein with serine-rich domain 1 ( RNPS1) is a component of pre-splicing and post-splicing multiprotein complexes, which activates constitutive and alternative splicing. RNPS1 participates in the formation of the spliceosome and activates the pre- mRNA splicing process. In the present study, we found that ubiquitin-specific protease 4 ( USP4) is a binding partner of RNPS1. Although RNPS1 is polyubiquitinated by both K48- and K63-linkages, USP4 exclusively deubiquitinates K63-linked polyubiquitin chains of RNPS1. We also demonstrate that the catalytic activity of USP4 on ubiquitinated RNPS1 is elevated by squamous cell carcinoma antigen recognized by T cells 3 (Sart3). [ABSTRACT FROM AUTHOR]

Abstract: The tumor suppressor protein p53 is ubiquitinated and neddylated by MDM2 and then degraded by 26S proteasome. However, p53 is stabilized by the HAUSP (Herpes-virus-associated ubiquitin-specific protease) deubiquitinating enzyme. In this study, we discovered that rat HAUSP (rHAUSP) is polyubiquitinated, polyneddylated, and dimerized using co-immunoprecipitation assays. This suggests that rHAUSP may function as a dimer or multimer and is also degraded through the proteasome-mediated degradation. Transfection of rHAUSP into RGC-Lac-Z cell line with the integrated p53 response element revealed that rHAUSP contributed to p53 stabilization, and a rHAUSP (C224S) mutant contributed to p53 destabilization in a dose-dependent manner. [Copyright &y& Elsevier]

The human genome contains nearly 100 deubiquitinating enzymes (DUBs) responsible for removing ubiquitin moieties from a large variety of substrates. Which DUBs are responsible for targeting which substrates remain mostly unknown. Here we implement the bioUb approach to identify DUB substrates in a systematic manner, combining gene silencing and proteomics analyses. Silencing of individual DUB enzymes is used to reduce their ubiquitin deconjugating activity, leading to an increase of the ubiquitination of their substrates, which can then be isolated and identified. We report here quantitative proteomic data of the putative substrates of 5 human DUBs. Furthermore, we have built a novel interactive database of DUB substrates to provide easy access to our data and collect DUB proteome data from other groups as a reference resource in the DUB substrates research field. [ABSTRACT FROM AUTHOR]

Premature ovarian failure (POF) is defined as loss of ovarian function in women less than 40 years of age. The causes of POF are diverse and include environmental factors. Di-2-ethylhexyl phthalate (DEHP) is one factor that may cause POF. The ubiquitin-proteasome system maintains intracellular balance by promoting or inhibiting protein degradation. To investigate the differential expressions of deubiquitinating enzyme (DUB) genes in patients with POF, we developed two in vitro POF models by treating A2780 or OVCAR5 with DEHP. Using these models, a multiplex RT-PCR system for DUB genes was applied to identify biomarkers by comparing expression patterns and DUB mRNA levels; multiplex RT-PCR results were validated by qRT-PCR and Western blotting analyses. Observed differential expression levels of several DUB genes including USP12, COPS5, ATXN3L, USP49, and USP34 in A2780 and OVCAR5 cells at the mRNA and protein levels suggest that they should be investigated as potential biomarkers of POF. [ABSTRACT FROM AUTHOR]

• Neurological disorders become dependent on failure of the ubiquitin-proteasome system (UPS) during aging. • The UPS is reversibly regulated by deubiquitinating enzymes (DUBs). • DUBs are a new therapeutic target in cases of neurodegenerative diseases. Most proteins undergo posttranslational modification such as acetylation, methylation, phosphorylation, biotinylation, and ubiquitination to regulate various cellular processes. Ubiquitin-targeted proteins from the ubiquitin-proteasome system (UPS) are degraded by 26S proteasome, along with this, deubiquitinating enzymes (DUBs) have specific activity against the UPS through detaching of ubiquitin on ubiquitin-targeted proteins. Balancing between protein expression and degradation through interplay between the UPS and DUBs is important to maintain cell homeostasis, and abnormal expression and elongation of proteins lead to diverse diseases such as cancer, diabetes, and autoimmune response. Therefore, development of DUB inhibitors as therapeutic targets has been challenging. In addition, understanding of the roles of DUBs in neurodegeneration, specifically brain diseases, has emerged gradually. This review highlights recent studies on the molecular mechanisms for DUBs, and discusses potential therapeutic targets for DUBs in cases of brain diseases. [ABSTRACT FROM AUTHOR]

Abstract: Deubiquitinating enzymes regulate a number of cellular mechanisms including pre-implantation, growth and differentiation, oncogenesis, cell cycle progression, transcriptional activation, and signal transduction. In this study, we have identified a novel human deubiquitinating enzyme gene, USP22, and its mouse homologue, Usp22. They encode 525 amino acids (approximate MW: 60kDa) and contains Cys, Asp (I), His and Asp/Asn (II), the highly conserved domains of the UBP family of deubiquitinating enzymes. The biochemical assay revealed that they have deubiquitinating enzyme activity. Northern blot analysis for USP22 showed moderate expression in various organs including human heart and skeletal muscle, and weak expression in lung and liver. However, Usp22 is expressed strongly in brain and weakly in other organs. We investigated the expression level of Usp22 mRNA and the localization during implantation and early pregnancy by in situ hybridization. Interestingly, Northern blot analysis showed the strong expression of Usp22 between embryonic days E10.5 and E12.5. Whole mount in situ hybridization staining revealed that Usp22 was expressed in the midbrain, forebrain, hindbrain and dorsal root ganglia of embryos at E12.5. Embryos at E12.5 showed the pronounced expression of Usp22 during the early embryonic development, although its expression was not detectable in the gut, liver and heart. [Copyright &y& Elsevier]