The RAP80-BRCC36 Deubiquitinating Complex in DNA Repair

 描述（由申请人提供）：乳腺癌1和2基因（BRCA 1和BRCA 2）的遗传突变赋予乳腺癌和卵巢癌以及胰腺癌和前列腺癌的易感性。BRCA蛋白是通过同源重组进行DNA修复所必需的，并且该功能与肿瘤抑制密切相关。BRCA突变状态也是化疗反应的重要预测因子。抑制特定的DNA修复途径已成为一种优雅而有效的策略，以诱导BRCA突变型癌症的合成致死性。因此，了解BRCA依赖性DNA修复的分子基础是癌症病因学和治疗的核心问题。我们发现BRCA 1通过RAP 80-BRCC 36复合物靶向于赖氨酸63连接的泛素区域，对齐DNA双链断裂染色质。这种复合物的缺乏导致BRCA 1 DNA损伤定位和基因组不稳定性降低。此外，编码该复合物成分的几个基因内的突变与家族性乳腺癌相关。这表明在双链断裂染色质处的泛素识别是BRCA依赖性肿瘤抑制的真正组成部分。该提案将采用体内、细胞和结构指导的生物化学方法来了解RAP 80-BRCC 36复合物对DNA双链断裂泛素的识别如何与BRCA依赖性同源重组修复机制和对治疗的反应相关。这些研究旨在阐明基本的DNA修复机制，并深入了解癌症病因和治疗。

 DESCRIPTION (provided by applicant): Inherited mutations in the Breast Cancer 1 and 2 genes (BRCA1 and BRCA2) confer susceptibility to breast and ovarian cancer, as well as to pancreatic and prostate cancers. The BRCA proteins are required for DNA repair by homologous recombination and this function is intimately connected to tumor suppression. BRCA mutation status is also an important predictor of response to chemotherapy. Inhibition of specific DNA repair pathways has emerged as an elegant and effective strategy to induce synthetic lethality in BRCA mutant cancers. Understanding the molecular basis of BRCA dependent DNA repair is therefore a central issue to cancer etiology and therapy. We have discovered that BRCA1 is targeted to lysine63-linked ubiquitin regions aligning DNA double-strand break chromatin by the RAP80-BRCC36 complex. Deficiency of this complex results in reduced BRCA1 DNA damage localization and genomic instability. Moreover, mutations within several genes that encode constituents of this complex are associated with familial breast cancer. This indicates that ubiquitin recognition at double-strand break chromatin is a bona fide component of BRCA dependent tumor suppression. This proposal will take in vivo, cellular, and structure guided biochemical approaches to understand how DNA double-strand break ubiquitin recognition by the RAP80-BRCC36 complex relates to BRCA dependent homologous recombination repair mechanisms and response to therapy. The studies are intended to elucidate basic DNA repair mechanisms and gain insights into cancer etiology and therapy.