DUB3 and USP7 de-ubiquitinating enzymes control replication inhibitor Geminin: molecular characterization and associations with breast cancer

Abstract

Correct control of DNA replication is crucial to maintain genomic stability in dividing cells. Inappropriate re-licensing of replicated origins is associated with chromosomal instability (CIN), a hallmark of cancer progression that at the same time provides potential opportunities for therapeutic intervention. Geminin is a critical inhibitor of the DNA replication licensing factor Cdt1. To properly achieve its functions, Geminin levels are tightly regulated through the cell cycle by ubiquitin-dependent proteasomal degradation, but the de-ubiquitinating enzymes (DUBs) involved had not been identified. Here we report that DUB3 and USP7 control human Geminin. Overexpression of either DUB3 or USP7 increases Geminin levels through reduced ubiquitination. Conversely, depletion of DUB3 or USP7 reduces Geminin levels, and DUB3 knockdown increases re-replication events, analogous to the effect of Geminin depletion. In exploring potential clinical implications, we found that USP7 and Geminin are strongly correlated in a cohort of invasive breast cancers (P<1.01E-08). As expected, Geminin expression is highly prognostic. Interestingly, we found a non-monotonic relationship between USP7 and breast cancer-specific survival, with both very low or high levels of USP7 associated with poor outcome, independent of estrogen receptor status. Altogether, our data identify DUB3 and USP7 as factors that regulate DNA replication by controlling Geminin protein stability, and suggest that USP7 may be involved in Geminin dysregulation during breast cancer progression.

Expression of MAGE‐A and NY‐ESO‐1 cancer/testis antigens is enriched in triple‐negative invasive breast cancers

“…Tumour cell percentage staining was subsequently stratified as either >75% or <75%, as this adequately described the positive cases. IHC analysis was performed for the markers, the results for some of which have been published previously . The cut‐off value for HER2 positivity was based on a silver in‐situ hybridisation (SISH) score of >6 and an IHC score of 3+ if SISH was unsuccessful.…”

Targeting ubiquitin specific protease 7 in cancer: A deubiquitinase with great prospects

“…USP7 is also a regulator of cell cycle protein Geminin. Lack of Geminin can cause re‐replication events ultimately leading to genome instability . It is proposed that USP7 can be targeted for treatment of haematological malignancies with DDR defects .…”

“…Lack of Geminin can cause re-replication events ultimately leading to genome instability. 76 It is proposed that USP7 can be targeted for treatment of haematological malignancies with DDR defects. 50 In case of CLL, USP7 inhibition prevents homologous recombination repair (HRR) and…”

Ubiquitin‐specific protease 7 (USP7) is essential for endometrial stromal cell decidualization in mice

“…They protect proteins from proteasomal degradation and it was suggested that their inhibition could promote the degradation of otherwise "undruggable" targets (Maertens et al, 2010;McClurg & Robson, 2015). Deregulation of the ubiquitination/deubiquitination PTM system was demonstrated to be associated with various disorders such as cancers (Glasser & Julian, 1986;Hernandez-Perez et al, 2017;Maertens et al, 2010;McClurg & Robson, 2015;Turnbull et al, 2017).…”

“…Ubiquitin-specific protease 7 (USP7), otherwise known as herpesvirus-associated ubiquitin-specific protease 7 (HAUSP), is a 135 kDa protein and a member of the DUB family, which functions in regulating protein stability and localization (Hussain et al, 2009). It plays a critical role in vital intracellular processes such as epigenetic regulation, cell cycle regulation, cell growth and survival (Gallo & Dirks, 2016;Glasser & Julian, 1986;Hernandez-Perez et al, 2017;Ma & Yu, 2016;Roby et al, 1993). Of note, its role in stabilizing various tumor suppressors, such as p53, Mdm2, PTEN and Myc (Castracane & Jordan, 1975;He et al, 2014;Hernandez-Perez et al, 2017;Hussain et al, 2009;Ma & Yu, 2016;Roby et al, 1993), has been well-characterized and its upregulation has been associated with many cancers (Hernandez-Perez et al, 2017;Jiang et al, 2016;Roby et al, 1993;Turnbull et al, 2017).…”