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

描述（由申请人提供）：在BRCA 1或BRCA 2蛋白缺乏的细胞中发现的DNA损伤反应和DNA修复缺陷在过去十年中得到了广泛表征。然而，这两种蛋白质之间的连接仍然相对知之甚少，因为它们在同源重组途径的不同步骤中发挥作用。同源重组（HR）的BRCA 1-BRCA 2途径的主要作用是保护基因组免受DNA复制过程中产生的内源性双链断裂引起的错误。BRCA 1被激活以通过Chk 2在丝氨酸988上的关键翻译后修饰促进同源重组，这随后导致控制双链断裂处5 '端切除的程度。第一个目标将集中在BRCA 1如何控制两端切除和随后的招聘同源重组包括BRCA 2的下游因子。第二个目标是特别关注在没有BRCA 1或BRCA 2的情况下，在复制过程中或外源性地产生的双链断裂会发生什么。Rad 52蛋白对于哺乳动物细胞中的同源重组是多余的，但在缺乏功能性BRCA 1-BRCA 2途径的情况下，它对于细胞活力变得至关重要。第二个目标是了解哺乳动物细胞中的Rad 52-Rad 51通路，因为它可以了解BRCA 1-BRCA 2通路缺陷的肿瘤细胞如何在正常的DNA复制中存活。因此，Rad 52是BRCA缺陷肿瘤治疗的关键肿瘤特异性靶标。第三个目标计划研究BRCA 1-BRCA 2通路中的新连接，这些连接在散发性乳腺癌中是有缺陷的，其中BRCA 1或BRCA 2没有遗传缺陷，但该通路没有连接。观察到BRCA 1未能募集到DNA损伤位点，并且“路障”似乎发生在RAP 80和Abraxas之间的BRCA 1的上游DNA损伤途径中。所有这三个目标都集中在同源重组的BRCA 1-BRCA 2途径中的联系上，这些拟议实验的知识应该为治疗该途径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.