Restoring genome stability and tumor suppression in BRCA1 deficient cells

项目摘要/摘要： 作为DNA损伤反应的中心介质，BRCA1和BRCA2蛋白通常起到保护 基因组完整性。事实上，它们的基因组维持功能被认为是一个主要的，如果不是主要的， BRCA1/2抑制正常细胞肿瘤形成的途径。具体地，BRCA1和BRCA2是 同源重组修复双链DNA断裂所必需的(DSBR-HR)。然而，最近 研究发现了BRCA1/2的另一种功能，它也可以保持基因组的稳定性，因此有可能 有助于这两种蛋白质的肿瘤抑制活性。在DNA复制过程中，BRCA1和BRCA2 已被证明通过保护停滞的复制叉(SRF)免受核溶解而促进基因组的完整性 退化。这些发现提出了关于BRCA1/2肿瘤抑制机制的关键问题 以及BRCA1/2通路靶向治疗的前景。例如，是肿瘤抑制 BRCA1/2通路的活性是通过其促进DSBR-HR或SRF稳定性的能力介导的，还是两者兼而有之？ 此外，BRCA1/2的DSBR-HR或SRF稳定功能能否恢复以用于预防和/或治疗 携带BRCA1/2突变的女性的目的？我们的初步研究发现了一部小说 在BRCA1突变细胞中重建SRF稳定性的机制。特别是，我们展示了 耗尽SMARCAL1，一种与复制分叉动力学有关的DNA易位酶，恢复两个SRF 复制压力下BRCA1缺陷细胞的稳定性和染色体完整性。在…的基础上 这些结果，我们假设在BRCA1-SMARCAL1中复制叉子的不适当重塑 细胞缺陷会增加基因组的不稳定性，从而使这些细胞更容易患上乳腺癌。为了测试 这些假设，我们将1)定义SMARCAL1失活挽救SRF稳定性的机制 和BRCA1缺陷细胞的染色体完整性，以及2)决定肿瘤抑制活性是否可以 通过抑制SMARCAL1，使其恢复到BRCA1突变细胞。

PROJECT SUMMARY/ABSTRACT: As central mediators of the DNA damage response, the BRCA1 and BRCA2 proteins normally act to preserve genome integrity. Indeed, their genome maintenance functions are thought to be a major, if not the principal, means by which BRCA1/2 suppress tumor formation in normal cells. In particular, BRCA1 and BRCA2 are required for double-strand DNA break repair by homologous recombination (DSBR-HR). However, recent studies have uncovered another BRCA1/2 function that also preserves genome stability and thus potentially contributes to the tumor suppression activity of both proteins. During DNA replication, BRCA1 and BRCA2 have been shown to promote genome integrity by protecting stalled replication forks (SRFs) from nucleolytic degradation. These findings raise critical questions regarding the mechanisms of BRCA1/2 tumor suppression and the prospects for therapeutic targeting of the BRCA1/2 pathway. For example, is the tumor suppression activity of the BRCA1/2 pathway mediated through its ability to promote DSBR-HR or SRF stability, or both? Also, can the DSBR-HR or SRF stability functions of BRCA1/2 be restored for prophylactic and/or therapeutic purposes in women who carry BRCA1/2 mutations? Our preliminary studies have uncovered a novel mechanism by which SRF stability can be reconstituted in BRCA1 mutant cells. In particular, we show that depletion of SMARCAL1, a DNA translocase implicated in replication fork dynamics, restores both SRF stability and chromosome integrity in BRCA1-deficient cells subjected to replication stress. On the basis of these results, we hypothesize that inappropriate remodeling of replication forks by SMARCAL1 in BRCA1- deficient cells can increase genome instability and thereby predispose these cells to breast cancer. To test these hypotheses, we will 1) define the mechanisms by which SMARCAL1 inactivation rescues SRF stability and chromosomal integrity in BRCA1-deficient cells, and 2) determine whether tumor suppression activity can be restored to BRCA1-mutant cells by SMARCAL1 inhibition.