MOLECULAR MECHANISMS OF BRCA1-DEPENDENT DNA DAMAGE RESPONSE AND TUMORIGENESIS

描述(申请人提供)：BRCA1是一种核多肽，用于抑制家族性乳腺癌和卵巢癌。越来越多的证据表明BRCA1参与了DNA损伤反应。然而，BRCA1参与DNA损伤反应的分子机制仍然不清楚。最近，我们确定了两个新的BRCA1合作伙伴，RAP80和CCDC98。RAP80和CCDC98都与BRCA1BRCT结构域相关，并参与DNA损伤反应。在功能上，RAP80和CCDC98促进BRCA1‘S易位到DNA损伤部位。为了寻找将这个BRCA1复合体招募到DNA损伤损伤中的信号，我们发现BRCA1相关蛋白RAP80识别泛素化的组蛋白H2A和H2B。DNA损伤后，组蛋白H_2A和H_2B进一步泛素化。此外，我们在乳腺和卵巢癌细胞中发现了RAP80基因的两个双等位错义突变和一个截断突变，提示RAP80可能是BRCA1依赖途径中的另一个乳腺和卵巢肿瘤抑制基因。因此，我们假设RAP80识别泛素化的组蛋白是将BRCA1加载到DNA损伤位置的分子基础，这调节了适当的DNA损伤反应，保护了基因组的完整性，并防止了乳腺和卵巢肿瘤的发展。我们建议进行以下实验来检验我们的假设。 目的：探讨RAP80和CCDC98靶向BRCA1损伤DNA的分子机制。目的：检测BRCA1依赖的DNA损伤反应中RAP80突变的功能缺陷。目的：探讨RAP80在肿瘤预防中的作用。综上所述，本文概述的研究不仅将揭示BRCA1参与DNA损伤反应的分子机制，而且还将确定BRCA1在肿瘤抑制中的功能伙伴。公共卫生相关性：积累的证据表明，BRCA1保护基因组完整性，以应对DNA双链断裂。在这里，我们已经确定了两个BRCA1合作伙伴，CCDC98和RAP80，它们参与了DNA损伤反应。在这项提议中，我们计划不仅剖析这种BRCA1复合体在DNA损伤反应中的分子机制，而且还研究这种复合体在体内肿瘤发生中的作用。

DESCRIPTION (provided by applicant): BRCA1 is a nuclear polypeptide to suppress familial breast and ovarian cancers. Accumulated evidence suggests that BRCA1 participates in DNA damage response. However, the molecular mechanisms by which BRCA1 participates in DNA damage response remain elusive. Recently, we have identified two new BRCA1 partners, RAP80 and CCDC98. Both RAP80 and CCDC98 associate with BRCA1 BRCT domain and participate in DNA damage response. Functionally, RAP80 and CCDC98 facilitate BRCA1's translocation to DNA damage sites. To search for the signals that recruit this BRCA1 complex to the DNA damage lesions, we have found that BRCA1-associated protein RAP80 recognizes ubiquitinated histone H2A and H2B. And both histone H2A and H2B are further ubiquitinated following DNA damage. In addition, we have identified two biallelic missense mutations and one truncation mutation of RAP80 gene in breast and ovarian cancer cells, suggesting that RAP80 could be another breast and ovarian tumors suppressor in BRCA1-dependent pathway. Thus, we hypothesize that recognition of ubiquitinated histone by RAP80 is the molecular basis that loads BRCA1 to DNA damage sites, which regulates proper DNA damage response, protects genomic integrity and prevents breast and ovarian tumor development. We propose following experiments to examine our hypothesis. Aim1: To examine the molecular mechanism by which RAP80 and CCDC98 target BRCA1 to DNA damage lesions. Aim2: To examine the functional defects of RAP80 mutations in BRCA1-dependent DNA damage response. Aim3: To examine the role of RAP80 in tumor prevention. In summary, studies outlined here will not only reveal the molecular mechanism by which BRCA1 participates in DNA damage response, but also identify the functional partners of BRCA1 in tumor suppression. PUBLIC HEALTH RELEVANCE: Accumulated evidence suggests that BRCA1 protects genomic integrity in response to DNA double strand breaks. Here, we have identified two BRCA1 partners, CCDC98 and RAP80, which participate in DNA damage response. In this proposal, we plan to not only dissect the molecular mechanism of this BRCA1 complex in DNA damage response, but also examine the role of this complex in tumorigenesis in vivo.