Modification of DNA Polymerase d by a Novel Mechanism During Replication Stress

具有BRCA 1/2的生殖系或体细胞突变的癌症具有受损的DNA修复途径， 重组（HR）缺陷。这些癌症对PARP抑制剂有独特的反应， BRCA1/2突变是决定乳腺癌和卵巢癌治疗选择的标志物。有一个 迫切需要在所有癌症中确定指示HR缺乏的其他标志物， PARP抑制剂在这些癌症中的应用。DNA同源修复途径需要许多蛋白质 和酶来协调DNA双链断裂的修复。其中，DNA聚合酶是 这是D环延伸的关键步骤。在这个应用中，我们假设一种特定形式的DNA 因此，没有Pol β 4的癌细胞是HR缺陷的，并且对HR敏感。 PARP抑制。该假设是基于我们在表征Pol β 4的酶性质方面的工作， 特别是链置换合成的能力。事实上，已经表明，大多数小细胞 肺癌（SCLC）细胞缺乏Pol β 4，这也得到了我们的初步数据的支持。这个的主要目标 该项目是为了验证我们的中心假设，即Pol β 4是可以执行D环的聚合酶的关键形式 延伸以促进DNA双链断裂的同源重组修复。癌细胞缺陷 在Pol β 4中，是HR缺陷的，并且对PARP抑制是敏感的。具体而言，该项目将1）建立该Pol 同源重组和Pol β 4缺陷对基因组稳定性的后果需要Pol β 4; 2） 表征Pol β 4缺陷型细胞对化疗剂和PARP抑制剂的独特反应; 3） 阐明通过3'-5 '解旋酶（包括BLM、WRN和DHX9）通过Pol d4进行的D-环延伸的调节。的 拟议的研究是创新的，因为我们采用多学科的方法，包括细胞研究， 酶表征以阐明D-环延伸中Pol β 4功能的潜在机制。的 从Poly的亚基组成的变化如何影响其在DNA复制和修复中的功能， 新颖啊这项提案的完成将大大有助于我们理解DNA是如何 损伤导致由于改变的Poly四级结构的致癌作用。该提案的结果可以 可能改变癌症治疗的临床实践，并定义一种新的可以治疗的癌症类别。 PARP抑制剂。

Cancers with germline or somatic mutations of BRCA1/2 have compromised DNA repair pathway, homologous recombination (HR) deficiency. These cancers have a unique response to PARP inhibitors and consequently BRCA1/2 mutations are markers to determine treatment options for breast and ovarian cancers. There is an urgent need to identify additional markers in all cancers that indicate deficiency in HR and consequently application of PARP inhibitors for these cancers. The DNA homologous repair pathway requires many proteins and enzymes to coordinate the repair of DNA double-stranded breaks. Among them, a DNA polymerase is essential for the key step of D-loop extension. In this application, we hypothesize that a specific form of DNA polymerase , Pol 4, is required for HR. Thus, cancer cells without Pol 4 are HR deficient and sensitive to PARP inhibition. The hypothesis is based on our work in characterization of the enzymatic properties of Pol 4, especially the ability in strand displacement synthesis. Indeed, it has been shown that the majority of small cell lung cancer (SCLC) cells lack Pol 4, which is also supported by our preliminary data. The main goal of this project is to test our central hypothesis that Pol 4 is the key form of polymerase that can perform D-loop extension to facilitate homologous recombination repair of DNA double-stranded breaks. Cancer cells deficient in Pol 4 are HR deficient and amendable to PARP inhibition. Specifically, this project will 1) Establish that Pol 4 is required for homologous recombination and the consequences of Pol 4-deficiency to genomic stability; 2) Characterize the unique response of Pol 4 deficient cells to chemotherapeutic agents and PARP inhibitors; 3) Elucidate the regulation of D-loop extension by Pol d4 by 3’-5’ helicases, including BLM, WRN and DHX9. The proposed research is innovative as we employ multidisciplinary approaches that include cellular studies and enzymatic characterization to elucidate the underlying mechanisms of Pol 4 function in D-loop extension. The insight from how changes in subunit composition of Pol  affect its function in DNA replication and repair is innovative. Completion of this proposal will be a significant contribution to our understanding of how DNA damages lead to carcinogenesis due to alteration of Pol  quaternary structure. The results in this proposal can potentially change clinical practice in cancer treatment and define a new class of cancers that can be treated with PARP inhibitors.