The JAMM motif of human deubiquitinase Poh1 is essential for cell viability
ABSTRACT Poh1 deubiquitinase activity is required for proteolytic processing of polyubiquitinated substrates by the 26S proteasome, linking deubiquitination to complete substrate degradation. Poh1 RNA interference (RNAi) in HeLa cells resulted in a reduction in cell viability and an increase in polyubiquitinated protein levels, supporting the link between Poh1 and the ubiquitin proteasome pathway. To more specifically test for any requirement of the zinc metalloproteinase motif of Poh1 to support cell viability and proteasome function, we developed a RNAi complementation strategy. Effects on cell viability and proteasome activity were assessed in cells with RNAi of endogenous Poh1 and induced expression of wild-type Poh1 or a mutant form of Poh1, in which two conserved histidines of the proposed catalytic site were replaced with alanines. We show that an intact zinc metalloproteinase motif is essential for cell viability and 26S proteasome function. As a required enzymatic component of the proteasome, Poh1 is an intriguing therapeutic drug target for cancer.
- SourceAvailable from: Selvaraju Karthik
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- "In particular, targeting proteasome-associated deubiquitination has the potential of increasing the levels of ubiquitin conjugated proteins, hence triggering proteotoxic stress and apoptosis similar to that observed with inhibitors of proteolytic activity. The metalloprotease POH1 is an obvious target since it is absolutely required for cell viability and is overexpressed in a variety of tumours (Gallery et al., 2007). "
ABSTRACT: Although more traditionally associated with degradation and maintenance of protein homeostasis, the ubiquitin-proteasome system (UPS) has emerged as a critical component in the regulation of cancer cell growth and survival. The development of inhibitors that block the proteolytic activities of the proteasome have highlighted its suitability as a bona fide anti-cancer drug target. However, key determinants including the development of drug resistance and dose-limiting toxicity call for the identification of alternative components of the UPS for novel drug targeting. Recently the deubiquitinases (DUBs), a diverse family of enzymes that catalyze ubiquitin removal, have attracted significant interest as targets for the development of next generation UPS inhibitors. In particular, pharmacological inhibition of the proteasomal cysteine DUBs (i.e., USP14 and UCHL5) has been shown to be particularly cytotoxic to cancer cells and inhibit tumour growth in several in vivo models. In the current review we focus on the modes of action of proteasome DUB inhibitors and discus the potential of DUB inhibitors to circumvent acquired drug resistance and provide a therapeutic option for the treatment of cancer. Copyright © 2015 Elsevier Ltd. All rights reserved.Drug resistance updates: reviews and commentaries in antimicrobial and anticancer chemotherapy 07/2015; 21-22. DOI:10.1016/j.drup.2015.06.001 · 9.12 Impact Factor
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- "PSMD14 is also expressed in many tissues and functions as a component of the 26S proteasome, which plays a role in protein degradation via deubiquitination [Verma et al., 2002; Yao and Cohen, 2002]. Knock-down of PSMD14 expression in human cell lines 842 AMERICAN JOURNAL OF MEDICAL GENETICS PART A revealed decreased cell viability [Gallery et al., 2007] and in carcinoma cells it leads to cell cycle arrest [Byrne et al., 2010]. Furthermore, knock-down of this gene in postmitotic neurons resulted in apoptosis [Staropoli and Abeliovich, 2005]. "
ABSTRACT: Interstitial deletions involving 2q24 have been associated with a wide range of phenotypes including intellectual disability and short stature. To date, the smallest common region among reported cases of deletions in this region is approximately 2.65 Mb and contains 15 genes. In the present case report, we describe an 18-year-old male with mild intellectual disability, short stature, and mosaicism for a 0.422 Mb deletion on 2q24.2 that was diagnosed by comparative genomic hybridization and confirmed with fluorescent in situ hybridization (FISH). This deletion, which is present in approximately 61% of cells, includes three genes: TBR1, TANK, and PSMD14. The findings suggest that the critical region for intellectual disability and short stature in 2q24.2 can be narrowed to a 0.422 Mb segment. TBR1, a transcription factor involved in early cortical development, is a strong candidate for the intellectual disability phenotype seen in our patient and in patients with larger deletions in this region of the genome. © 2013 Wiley Periodicals, Inc.American Journal of Medical Genetics Part A 04/2013; 161A(4). DOI:10.1002/ajmg.a.35751 · 2.16 Impact Factor
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- "Indeed, a single point mutation on the conserved zinc-coordinating histidine 113 abolished DUB activity. These results are in agreement with mutational studies on Psmd14 function in human protein orthologues (Gallery et al., 2007). In contrast, we found cysteine 120 to be dispensable for Psmd14 function in ES cells, consistent with the fact that it belongs to a family distinct from the cysteine proteases. "
ABSTRACT: Although transcriptional regulation of stem cell pluripotency and differentiation has been extensively studied, only a small number of studies have addressed the roles for posttranslational modifications in these processes. A key mechanism of posttranslational modification is ubiquitination by the ubiquitin-proteasome system (UPS). Here, using shotgun proteomics, we map the ubiquitinated protein landscape during embryonic stem cell (ESC) differentiation and induced pluripotency. Moreover, using UPS-targeted RNAi screens, we identify additional regulators of pluripotency and differentiation. We focus on two of these proteins, the deubiquitinating enzyme Psmd14 and the E3 ligase Fbxw7, and characterize their importance in ESC pluripotency and cellular reprogramming. This global characterization of the UPS as a key regulator of stem cell pluripotency opens the way for future studies that focus on specific UPS enzymes or ubiquitinated substrates.Cell stem cell 10/2012; 11(6). DOI:10.1016/j.stem.2012.09.011 · 22.27 Impact Factor