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  • Phosphatase Inhibitor Cocktail 2 (100X in ddH2O) sale As CP


    As CP110 is a crucial player in centriole duplication, it is intriguing to ask whether centriole duplication would also be affected in the absence of the CP110-stabilizing effects of USP33. Li et al.[4] found that USP33 depletion did not inhibit normal centriole duplication through loss of centrioles: instead, loss of USP33 inhibited centrosome re-duplication. In some cell lines, for example U2OS, centrosome re-duplication can be induced by the addition of hydroxyurea, which promotes cell-cycle arrest at the G1/S phase transition but does not affect centrosome duplication and thereby results in an increase in centrosome numbers. A similar effect on centrosome duplication is caused by CP110 depletion [5]. Intriguingly, co-depletion of USP33 and SCFcyclinF rescued the mitotic defects caused upon siRNA-mediated downregulation of SCFcyclinF[4]. Therefore, opposing activities of E3 ubiquitin ligases and DUBs that both target key regulators of centriole duplication may represent a general mechanism for regulating the levels of those factors during the cell cycle and centriole biogenesis. Supernumerary centrosomes are frequently found in cancer cells. During cell division too many centrosomes induce errors in chromosome segregation and lead to Phosphatase Inhibitor Cocktail 2 (100X in ddH2O) sale as a result of transient multipolar spindle formation [14]. Interestingly, Li et al.[4] also found that both USP33 and CP110 are upregulated and their protein levels strongly correlated in a variety of pancreatic tumor cell lines and pancreatic cancer tissue samples. CP110 is targeted for ubiquitination and degradation during G2 phase by SCFcyclinF and SCFcyclinF levels also peak in G2. It would be interesting to see whether SCFcyclinF levels correlate with USP33 and CP110 levels in pancreatic cancer cells. This work therefore reveals that a dynamic balance of ubiquitination by SCFcyclinF and deubiquitination by USP33 contributes to the onset of centriole duplication and elongation. In the future, it will be important to understand more about the roles of different DUBs in the control of other critical regulators of centriole biogenesis and ciliogenesis and their impact on the generation of aneuploidy.
    Main Text Removal of ubiquitin (Ub) “marks” from proteins regulates many aspects of eukaryotic cellular function. The ubiquitin signal is removed by deubiquitinases (DUBs), which cleave the ubiquitin-substrate bond to release ubiquitin. DUBs are divided into seven highly conserved families based on their architecture and each plays a critical role in counteracting ubiquitin attachment by E3 ligases (Clague et al., 2019). Dysregulation of DUB activity is associated with multiple cancers, including melanoma, mesothelioma, and renal cell carcinoma, as well as neurological and developmental disorders (Harrigan et al., 2018). As a result, there is considerable potential in modulating the activity of DUBs. DUBs are theoretically an easy target because most are cysteine proteases and their active sites are well defined and tempting for drug development. However, small-molecule inhibitor development has been difficult because of issues with the low specificity of these compounds (Kemp, 2016). Furthermore, the absence of potent inhibitors has limited progress on understanding DUB biology. In this issue, Sidhu and colleagues develop inhibitors for USP15, a member of the Ub-specific protease (USP) family of DUBs (Teyra et al., 2019). USP15 removes ubiquitin from a number of substrates, including transforming growth factor beta (TGF-β) receptor, as well as the E3 ligases MDM2, TRIM25, and BRCA1-associated protein (BRAP). Given the key regulatory role of these substrates, it is not surprising that USP15 copy-number variation is associated with cancer. The structure of the USP15 catalytic domain includes a ubiquitin binding pocket and a catalytic triad that hydrolyzes the isopeptide bond linking ubiquitin to its substrate. USP15 is highly similar to USP4 and USP11 (Clague et al., 2019), which means that the development of selective inhibitors is likely to be difficult.