Checkpoint Responses for Protecting Genome Integrity in S-Phase

描述（由申请人提供）：保护基因组完整性对于预防可能导致癌症、衰老相关疾病、神经、免疫和发育疾病、不孕症、出生缺陷和许多其他疾病的基因突变和染色体重排至关重要。DNA损伤触发检查点激酶ATM和ATR磷酸化染色质侧翼DNA损伤中的组蛋白H2 AX的C末端。这种磷酸-H2 AX，称为gamma-H2 AX，作为信号和蛋白质对接平台来调节DNA修复和细胞周期检查点活动。虽然γ-H2 AX在由电离辐射和其他断裂剂产生的DNA双链断裂中具有众所周知的作用，但其在细胞周期的DNA合成（S）期期间停滞或受损的复制叉中的作用是神秘的。我们最近发现，γ-HAX招募基因组维持因子Brc 1停滞或损坏的复制叉。我们还发现，Brc 1结合γ-H2 AX是至关重要的，在没有Rqh 1，这是直系同源的人BLM DNA解旋酶，是突变的布卢姆氏综合征。在这个项目中，我们提出：（1），发现为什么<$H2AX是至关重要的，当Rqh 1 DNA解旋酶是有缺陷的;（2），定义和表征的遗传缺陷，创造了一个关键的要求<$H2AX和Brc 1;（3），评估的功能，负电性表面的BRCT 5 -6域间连接的Brc 1。这些研究的影响将显着提高对S期基因组完整性如何保护的理解。

DESCRIPTION (provided by applicant): Protection of genome integrity is critical for preventing genetic mutations and chromosomal rearrangements that can lead to cancer, aging-related disorders, neurological, immunological and developmental diseases, infertility, birth defects and many other disorders. DNA damage triggers the checkpoint kinases ATM and ATR to phosphorylate the C-terminus of histone H2AX in chromatin flanking DNA lesions. This phospho-H2AX, known as gamma-H2AX, serves as a signaling and protein docking platform to regulate DNA repair and cell cycle checkpoint activities. While gamma-H2AX has well known roles at DNA double- strand breaks created by ionizing radiation and other clastogens, its role at stalled or damaged replication forks during the DNA synthesis (S)-phase of the cell cycle is enigmatic. We recently discovered that gamma-HAX recruits the genome maintenance factor Brc1 to stalled or damaged replication forks. We also found that Brc1 binding to gamma-H2AX is crucial in the absence of Rqh1, which is the ortholog of human BLM DNA helicase that is mutated in Bloom's Syndrome. In this project we propose to: (1), discover why ¿H2AX is crucial when Rqh1 DNA helicase is defective; (2), define and characterize the genetic deficiencies that create a critical requirement for ¿H2AX and Brc1; (3), assess the functions of the electronegative surface in the BRCT5-6 interdomain linker of Brc1. The impact of these studies will be to significantly improve the understanding of how genome integrity is protected in S-phase.