Connections and redundancy in the BRCA1-BRCA2 pathway of homologous recombination

描述(由申请人提供)：在BRCA1或BRCA2蛋白缺失的细胞中发现的DNA损伤反应和DNA修复缺陷在过去十年中得到了广泛的表征。然而，这两种蛋白质之间的联系仍然相对知之甚少，因为它们在同源重组的不同步骤中发挥作用。同源重组(HR)的BRCA1-BRCA2途径的主要作用是保护基因组免受DNA复制过程中内源性双链断裂造成的错误的影响。通过Chk2对丝氨酸988进行关键的翻译后修饰，BRCA1被激活以促进同源重组，从而控制双链断裂时5‘端切除的程度。第一个目标将集中在BRCA1如何控制末端切除和包括BRCA2在内的同源重组中下游因子的随后招募。第二个目标是特别关注在复制过程中或在没有BRCA1或BRCA2的情况下，双链断裂会发生什么。在哺乳动物细胞中，Rad52蛋白对于同源重组是多余的，但在缺乏功能的BRCA1-BRCA2途径的情况下，它对细胞活力至关重要。第二个目标是了解哺乳动物细胞中的Rad52-RAD51通路，因为它可能有助于深入了解BRCA1-BRCA2通路缺陷的肿瘤细胞如何在正常的DNA复制中存活。因此，RAD52是治疗BRCA缺陷肿瘤的一个关键的肿瘤特异性靶点。第三个目标计划寻找BRCA1-BRCA2通路中的新连接，这些连接在散发性乳腺癌中存在缺陷，其中BRCA1或BRCA2没有遗传缺陷，但该通路没有连接。观察到未能将BRCA1招募到DNA损伤部位，并且在RAP80和Abraxas之间到BRCA1的上游DNA损伤途径中似乎出现了“路障”。这三个目标都集中在BRCA1-BRCA2同源重组途径中的联系上，来自这些拟议实验的知识应该会为治疗这一途径存在缺陷的人类癌症提供新的见解。

DESCRIPTION (provided by applicant): The DNA damage response and DNA repair defects found in cells with a deficiency of the BRCA1 or BRCA2 protein have been extensively characterized in the last decade. However, the connections between the two proteins remain relatively poorly understood, as they function at different steps in the pathway of homologous recombination. The major role of the BRCA1-BRCA2 pathway of homologous recombination (HR) is to protect the genome from errors arising out of endogenously created double-strand breaks, which are created during DNA replication. BRCA1 is activated to promote homologous recombination by a critical post-translational modification by Chk2 on serine 988, which then results in controlling the extent of 5'-end resection at double- strand breaks. The first aim will focus on how BRCA1 controls both end resection and the subsequent recruitment of downstream factors in homologous recombination including BRCA2. The second aim is specifically focused on what happens to double-strand breaks, created during replication or exogenously, in the absence of BRCA1 or BRCA2. The Rad52 protein is redundant for homologous recombination in mammalian cells, but in the absence of a functioning BRCA1-BRCA2 pathway, it becomes critical for cell viability. The goals of this second aim are to understand the Rad52-Rad51 pathway in mammalian cells as it may give insight on how tumor cells defective in BRCA1-BRCA2 pathway survive normal DNA replication. Rad52 is therefore a key tumor-specific target for therapy in BRCA-deficient tumors. The third aim plans to look at new connections in the BRCA1-BRCA2 pathway that are defective in sporadic breast cancers, where there is no genetic defect in BRCA1 or BRCA2, but the pathway is not connected. A failure to recruit BRCA1 to sites of DNA damage is observed and the "road-block" appears to occur in the upstream DNA damage pathway to BRCA1 between RAP80 and Abraxas. All three aims are focused on the connections in the BRCA1-BRCA2 pathway of homologous recombination, and the knowledge from these proposed experiments should allow new insight for treating human cancers with defects in this pathway.