Research Projects

This proposal aims to explore the functional link between USP7 deubiquitinase and CRL4Cdt2 E3 ubiquitin ligase, and extend its role in regulating homologous recombination repair (HR). USP7 is a deubiquitinating enzyme that stabilizes substrates by protecting them from ubiquitin-mediated degradation. CRL4Cdt2 promotes ubiquitin-mediated degradation of substrates during the cell cycle and accumulates at double-stranded break sites after DNA damage. The E3 ubiquitin ligases RNF8 and RNF168 are responsible for H2AX ubiquitination at damaged sites, which triggers the recruitment of 53BP1 and RAP80/BRCA1 complex to DSB sites. USP7 has been recently implicated in the promotion of HR, but how it promotes HR remains unclear. Based on existing literature and preliminary data, the study hypothesizes that the USP7 and CRL4Cdt2 complex form a novel axis with a regulatory role in HR. Experiments suggest that USP7 deubiquitinase activity is required for the stability of the functional CRL4Cdt2 complex. Objectives include establishing the functional link between USP7 and CRL4Cdt2, determining the effect of inactivation of USP7 on the CRL4Cdt2 complex under basal and DNA-damaging conditions, and evaluating the role of the USP7-CRL4Cdt2 axis in HR using I-SecI-based HR assay. The study aims to implicate this novel axis of the USP7-CR4Cdt2 in HR, as both USP7 and CRL4Cdt2 are druggable enzymes. By understanding the role of the USP7-CR4Cdt2 novel axis in HR, this study could serve as a foundation for targeting USP7 and CRL4Cdt2 and disrupting the HR pathway as a therapeutic strategy for various malignancies.