Functional analysis of BRCA1 in DNA damage response and tumor suppression

描述（申请人提供）：BRCA是常见乳腺癌和卵巢癌的重要肿瘤抑制因子。越来越多的证据表明BRCA 1参与DNA损伤反应，包括细胞周期检查点激活和DNA损伤修复。BRCA 1的突变消除了DNA损伤反应，并在遗传毒性应激下诱导基因组不稳定性。有趣的是，最近的证据表明，PARP抑制剂可以特异性抑制BRCA 1突变诱导的乳腺肿瘤。同样，PARP抑制剂选择性杀死携带BRCA 1突变的肿瘤细胞的分子机制尚不清楚。研究表明，BARD 1是BRCA 1的功能伴侣。与BRCA 1一样，BARD 1的生殖系突变已在乳腺癌和卵巢癌患者中发现。BARD 1突变携带者也易患乳腺癌和卵巢癌，这表明BARD 1与BRCA 1一样是一种重要的肿瘤抑制因子。出乎意料的是，我们发现BARD 1的BRCT结构域识别聚（ADP-核糖）（PAR）。BARD 1 BRCT结构域和PAR之间的相互作用是将BRCA 1靶向DNA损伤位点所必需的，并促进相关的DNA损伤修复。基于我们的初步研究，我们假设PAR和BRCA 1-BARD 1复合物之间的结合在乳腺和卵巢肿瘤抑制中起着关键作用。因此，在本项目中，我们计划：1）研究PAR调节BRCA 1-BARD 1复合物响应DNA损伤的分子机制; 2）表征PAR依赖性DNA损伤反应中癌症相关BRCA 1和BARD 1突变的功能缺陷; 3）研究PARP抑制剂治疗BRCA 1突变诱导的乳腺肿瘤的疗效。这些研究不仅将揭示BRCA通路在DNA损伤反应中的分子机制，而且将把我们的基础科学研究转化为肿瘤预防。

DESCRIPTION (provided by applicant): BRCA is an important tumor suppressor for familiar breast and ovarian cancers. Accumulated evidence suggests that BRCA1 participates in DNA damage response including cell cycle checkpoint activation and DNA damage repair. Mutations of BRCA1 abrogate DNA damage response and induce genomic instability under genotoxic stress. Interestingly, recent evidence suggests that PARP inhibitors can specifically suppress BRCA1 mutation-induced breast tumors. Again, the molecular mechanism by which PARP inhibitor selectively kill tumor cells bearing BRCA1 mutations is not clear. It has been shown that BARD1 is a functional partner of BRCA1. Like BRCA1, germline mutations of BARD1 have been found in breast and ovarian cancer patients. Carriers of BARD1 mutations are also predisposed to breast and ovarian cancers, suggesting that like BRCA1, BARD1 is an important tumor suppressor. Unexpectedly, we found that the BRCT domain of BARD1 recognizes poly(ADP-ribose) (PAR). The interaction between the BARD1 BRCT domain and PAR is required for targeting BRCA1 to the sites of DNA damage and facilitates the correlated DNA damage repair. Based on our preliminary study, we hypothesize that the binding between PAR and the BRCA1-BARD1 complex plays a critical role for breast and ovarian tumor suppression. Thus, in this project, we plan to: 1) examine the molecular mechanism by which PAR regulates the BRCA1-BARD1 complex in response to DNA damage; 2) characterize the functional defects of the cancer-associated BRCA1 and BARD1 mutations in PAR-dependent DNA damage response; 3) study the efficacy of PARP inhibitors in the treatment of BRCA1 mutation-induced mammary tumors. These studies will not only reveal the molecular mechanism of BRCA pathway in DNA damage response, but also translate our basic science research into tumor prevention.