DHSA Pilot Projects:
Project Title: "Discovery of inhibitors against the ubiquitin specific protease 11 in human DNA damage response"
Co-Investigators: Zhihao Zhuang, UD, Andrew Napper, Nemours, Jonathan Brody, TJU, and Zohra Ali-Khan Catts, CCHS
Background and Significance:
Deregulation of ubiquitin-proteasome system has been linked to many human diseases, including cancer, neurological disorder and viral infection. Although ubiquitin is best known for its role in proteasome-mediated protein degradation. The non-proteolytic functions of ubiquitin in diverse cellular processes, including protein trafficking, immune response, transcription regulation and DNA damage response, have attracted increasing attentions. Protein ubiquitylation is mediated by ubiquitin ligase and deubiquitinating enzymes (DUBs). Abnormal cellular expression of DUBs has been linked to various human diseases, especially cancer. DUBs are considered promising targets for pharmacological intervention. The advantage of inhibiting DUB lies in the potential specificity of therapeutic intervention that can lead to better efficacy and eliminate nonspecific side effects.
In this proposal we will target human ubiquitin specific protease 11 (USP11) for developing potent inhibitors. USP11 plays an important role in cellular response to DNA damage. Disruption of USP11 by active site mutation or reduction in cellular USP11 expression by shRNA sensitizes cancer cells to DNA crosslinker mitomycin C. USP11 forms a stable heterodimeric complex with BRCA2, an essential tumor suppressor gene product. Individuals who carry germ line mutations in the BRCA2 gene are predisposed to many types of cancers, including breast, ovarian, pancreatic and prostatic cancers. BRCA2 has been implicated in DNA double strand break repair. Recent studies suggest that BRCA2 likely plays additional roles in DNA damage response. Patients with deficiency in BRCA2 gene are hypersensitive to DNA crosslinking agents, e.g. cisplatin, carboplatin and mitomycin C. It has also been shown that in pancreatic cancer cells, alteration in BRCA2 results in hypersensitive to intrastrand cross-linking agents and platinum-based drugs in multiple in vitro and in vivo models. Because of the demonstrated prosurvival function of USP11 in response to DNA crosslinkers, selective inhibition of USP11 likely provide a means of sensitizing human cancer cells to DNA damaging drugs and provide the basis for new combination therapy.
Specific Aims:
- Develop fluorescence-based assay for the deubiquitinating activity of USP11.
- Identify USP11 inhibitors through HTS and validate the hits in both in-vitro and cell-based assays.
- Map the interaction between BRCA2 and USP11.