Role of HELB in the Replication Stress Response

总结 基因组的准确和完整复制对于增殖和基因组稳定性都是必不可少的。 基因组DNA不断受到外源和内源因子的攻击。所得DNA 损伤可导致复制叉的停滞和复制应激反应（RSR）的激活。这 激活一组保护和重新启动复制叉的蛋白质，以维持基因组的完整性。 不正确的修复会导致癌症和衰老，RSR的缺陷使个体容易患上癌症。 我们的总体目标是确定在复制应激期间保护基因组的分子机制。我们 已经发现DNA解旋酶B（HELB）通过以下方式保护停滞的复制叉免于异常降解 核酸酶和促进复制重新启动。这与数据显示的恢复率降低一致， 复制压力与HELB敲低;然而，HELB促进恢复的机制 复制应力未知。此外，我们发现HELB通过G-四链体增强复制 (G4)结构，这表明HELB可能使复制叉能够通过难以复制的方式进行 网站.由于复制停滞可导致表观遗传不稳定性，HELB可能参与表观遗传不稳定性。 除了基因组的维护。HELB也与DNA复制的启动有关 以及同源重组（HR）中末端切除的调节。由于其在多个过程中的不同作用， 可能需要对HELB活动进行监管。事实上，我们有证据表明，HELB活动是由后- 翻译修饰（translational modifications，PTM）。我们假设HELB通过以下方式维持基因组和表观遗传的完整性： 保护新生DNA免于降解，帮助复制重新启动，并通过困难的复制来帮助复制。 网站.我们将通过以下具体目标来检验这一假设：（1）确定HELB在保护中的作用 （2）通过对HELB基因的复杂性分析，确定HELB基因在复制中的作用。 基因组的复制区域，以及（3）描述HELB PTM和蛋白质-蛋白质相互作用（PPI）的作用 在复制应激反应中。

Summary Accurate and complete replication of the genome is essential for both proliferation and genomic stability. Genomic DNA is constantly under assault from both exogenous and endogenous agents. The resulting DNA lesions can cause stalling of the replication fork and activation of the replication stress response (RSR). This activates a group of proteins that protect and restart the replication fork so that genomic integrity is maintained. Incorrect repair can lead to cancer and aging, and defects in the RSR predispose individuals to develop cancer. Our overall goal is to define the molecular mechanisms that protect the genome during replication stress. We have discovered that DNA Helicase B (HELB) protects stalled replication forks from aberrant degradation by nucleases and promotes replication restart. This is consistent with data showing reduced recovery from replication stress with HELB knockdown; however, the mechanism by which HELB promotes recovery from replication stress is unknown. In addition, we have found that HELB enhances replication through G-quadruplex (G4) structures, suggesting that HELB may enable the replication fork to progress through difficult to replicate sites. Since replication stalling can result in epigenetic instability, HELB may be involved in epigenetic maintenance in addition to genomic maintenance. HELB has also been implicated in initiation of DNA replication and regulation of end resection in homologous recombination (HR). Due to its varied roles in multiple processes, regulation of HELB activity is likely required. Indeed, we have evidence that HELB activity is regulated by post- translational modifications (PTMs). We hypothesize that HELB maintains genomic and epigenetic integrity by protecting nascent DNA from degradation, aiding in replication restart, and assisting in replication through difficult sites. We will test this hypothesis through the following Specific Aims: (1) Ascertain the role of HELB in protection and restart of stalled DNA replication forks, (2) Determine the function of HELB in replication through difficult to replicate regions of the genome, and (3) Delineate the role of HELB PTMs and protein-protein interactions (PPIs) in the replication stress response.