Role of BRCA1 phosphorylation in DNA DSB repair and genome stability maintenance

肿瘤抑制基因BRCA1在同源重组(HR)途径中发挥重要作用 DNA双链断裂(DSB)修复。从机制的角度来看，BRCA1促进了招聘 末端切除所需的核酸酶是HR修复中的承诺步骤，但矛盾的是，BRCA1一直是 体外显示对核酸酶活性有抑制作用。目前尚不清楚核酸酶的招募和抑制活性是如何 BRCA1可以在HR Repair中进行调节。从癌症病理生理学的角度来看，大多数BRCA1- 相关的乳腺肿瘤是基底样瘤，但它们起源于腔前体细胞，即所谓的起源细胞。 这提出了一个重要且在很大程度上尚未解决的问题：BRCA1是否影响HR修复和基因组 以一种细胞谱系和基因组位置偏好的方式稳定？ 我们的初步数据表明，BRCA1的修改发出了及时离开DSB的信号，因此 有效中和其在DSB的核酸酶抑制活性。使用临床样本，我们还发现鲁米纳 BRCA1突变携带者的细胞对辐射特别敏感，容易积聚DSB 在特定的基因组座位上的前体。基于这些令人信服的初步数据，我们假设BRCA1 修改是许可机制的一部分，该机制将HR的承诺步骤限制在S/G2阶段。我们 进一步提出BRCA1 HR修复活性对瘤胃基因的遗传完整性特别重要 乳腺组织的腔细胞。我们由实验室和临床科学家组成的多学科团队将结合 利用小鼠遗传学和人类样本的细胞培养系统来验证这一新的假设。 我们提议的工作旨在验证BRCA1在许可 HR中的承诺步骤，从而挑战了目前认为BRCA1仅仅是一个脚手架蛋白的观点。 此外，通过询问BRCA1 HR在临床相关细胞谱系和基因组区域的功能， 我们的工作与传统的以细胞系为中心的机制研究有很大的不同。我们的建议 这项工作有助于填补BRCA1机制研究和组织/细胞病因学之间的关键知识空白 谱系特异性BRCA1相关肿瘤的发生，从而显著推进BRCA1相关乳房 癌症研究。

The tumor suppressor BRCA1 plays an important role in the homologous recombination (HR) pathway of DNA double strand break (DSB) repair. From a mechanistic perspective, BRCA1 facilitates recruitment of nucleases required for end resection, the commitment step in HR repair, yet paradoxically, BRCA1 has been shown to inhibit the nuclease activity in vitro. It is unclear how nuclease-recruiting and -inhibiting activities of BRCA1 can be reconciled in HR repair. From a cancer pathophysiological perspective, most BRCA1- associated breast tumors are basal-like but they originate from luminal progenitor cells, so-called cells of origin. This poses an important and largely unaddressed question: does BRCA1 influence HR repair and genome stability in a cell lineage- and genomic locus-preferred manner? Our preliminary data indicate that BRCA1 modifications signal its timely departure from DSBs and thus effectively neutralize its nuclease-inhibiting activity at DSB. Using clinical samples, we also found that luminal cells from BRCA1 mutation carriers are particularly radiosensitive and prone to accumulation of DSB precursors at specific genomic loci. Based on these compelling preliminary data, we hypothesize that BRCA1 modifications are part of a licensing mechanism that confines the commitment step of HR to S/G2 phase. We further propose that BRCA1 HR repair activity is particularly important for genetic integrity at luminal genes in luminal cells of the breast tissue. Our multidisciplinary team of laboratory and clinician scientists will combine cell culture systems with mouse genetics and human samples to test this novel hypothesis. Our proposed work seeks to validate a previously unrecognized role of BRCA1 in licensing the commitment step in HR, thus challenging the current view of BRCA1 merely as a scaffolding protein. Furthermore, by interrogating BRCA1 HR function in the clinically relevant cell lineage and genomic regions, our work represents a significant departure from traditional cell line-focused mechanistic studies. Our proposed work helps fill a critical knowledge gap between mechanistic investigation of BRCA1 and etiology of tissue/cell lineage-specific BRCA1-associated tumor development, thus substantially advancing BRCA1-related breast cancer research.