Deubiquitinases in regulation of BRCA1 pathway

 描述(由申请人提供)：保持基因组的稳定性对生物体的福祉至关重要。细胞基因组不断受到外源性和内源性DNA损伤因素的攻击，如辐射、致癌物和活性自由基。为了保持基因组的稳定性，细胞开发了一种复杂的DNA损伤反应(DDR)系统，负责检测DNA损伤，停止正在进行的细胞周期，并修复受损的DNA。DDR途径的失败导致基因组不稳定，这是肿瘤发生的驱动力之一。许多人类遗传性癌症易感综合征与DDR缺陷有关。例如，在大约50%的家族性乳腺癌病例中发现了BRCA1基因的突变。由于个别肿瘤往往在DDR途径中存在独特的缺陷，深入了解细胞修复不同DNA损伤的基本机制也可以指导个体化治疗。一个有希望的例子是在BRCA1和BRCA2突变的癌症中使用PARP抑制剂。另一方面，许多研究表明，DNA修复因子的过度表达导致了化疗耐药。因此，研究该通路对肿瘤的发病机制和肿瘤治疗具有重要意义。该提案中的初步数据首次表明，去泛素酶USP13调节同源重组介导的DNA修复。在机械上，USP13与RAP80相互作用并使RAP80去泛素化，这反过来又促进RAP80-BRCA1复合体的招募以双链断裂并促进同源重组。耗尽或抑制USP13可使卵巢癌细胞对顺铂和PARP抑制剂敏感，但对正常卵巢上皮细胞不敏感。该提议的中心假设是，USP13是DNA修复中的一个新因子。USP13通过去泛素化RAP80来调节DNA损伤反应和HR修复。USP13的过表达通过促进DNA修复而参与化疗耐药。这些实验将揭示USP13在DNA修复和化疗反应中的新功能。此外，它还将揭示一个新的治疗靶点，通过靶向USP13-RAP80-BRCA1通路来敏化卵巢癌细胞，特别是那些高表达USP13的细胞。具体目的如下：1.研究USP13对RAP80的调控。2.研究DDR信号对USP13的调控。3.探讨USP13在化疗耐药中的作用。

 DESCRIPTION (provided by applicant): Maintenance of genomic stability is critical for the well-being of organisms. The genome of a cell is under constant attack from exogenous and endogenous DNA damaging factors such as radiation, carcinogens and reactive radicals. To maintain genomic stability, cells have developed an elaborate DNA damage response (DDR) system, which is responsible for sensing DNA damage, halting the ongoing cell cycle, and repairing the damaged DNA. Failure in the DDR pathway leads to genomic instability, which is one of the driving forces of tumorigenesis. Many human genetic cancer predisposition syndromes are linked to defective DDR. For example, mutations in the BRCA1 gene are found in about 50% of familial breast cancer cases. Since individual tumors often have unique defects in the DDR pathway, insight into the basic mechanisms by which cells repair different DNA lesions can also guide individualized therapy. A promising example is the use of PARP inhibitors in cancers with BRCA1 and BRCA2 mutations. On the other hand, many studies suggest that overexpression of DNA repair factors contributes to resistance to chemotherapy. Therefore, studying this pathway has important implications in cancer pathogenesis and cancer therapy. Preliminary data within this proposal showed for the first time that the deubiquitinase, USP13, regulates homologous recombination mediated DNA repair. Mechanically, USP13 interacts with RAP80 and deubiquitinates RAP80, which in turn facilitates the recruitment of RAP80-BRCA1 complex to double strand breaks and promotes homologous recombination. Depleting or inhibiting USP13 sensitizes ovarian cancer cells but not the normal ovarian epithelial cells to cisplatin and PARP inhibitor. The central hypothesis of the proposal is that USP13 is a new factor in DNA repair. USP13 regulates DNA damage response and HR repair by deubiquitinating RAP80. Overexpression of USP13 contributes to chemotherapeutic resistance by enhancing DNA repair. These experiments will reveal a novel function of USP13 in DNA repair and response to chemotherapy. In addition, it will reveal a new therapeutic target in sensitizing ovarian cancer cells, especially those overexpressing USP13, by targeting the USP13-RAP80-BRCA1 pathway. The Specific Aims are the following: 1. Investigate the regulation of RAP80 by USP13. 2. Study the regulation of USP13 by DDR signaling. 3. Investigate the role of USP13 in chemoresistance.