Regulation of Initial Steps of Chromosomal Breaks Repair

重组是维持基因组稳定的关键，甚至是基因组中的微小缺陷 重组双链断裂(DSB)修复通路导致癌症或其他严重的 疾病。将DNADSB初步加工成单链，这一过程称为DNA末端 切除，是装载损伤所需的同源重组的关键第一步 反应和修复蛋白。切除在细胞周期中受到严格控制，并决定了 使用同源重组与非同源末端连接进行修复。在酵母和 在人类细胞中，Mre11-Rad50-Nbs1/Xrs2复合体启动切除，而Exo1或SGS1- DNA2介导了广泛的切除。到目前为止，对切除的系统研究只进行了一次。 在常染色质中，而我们建议在三种不同类型的沉默中研究它 异染色质。我们设计了许多新的分析方法来检查转录内的切除 裂解酵母中的沉默染色质(目标1)。裂解酵母系统提供了一个极好的模型 因为染色质的特征与人类细胞中的特征非常保守。在……里面 目标#2我们专注于控制DSB修复中最具突变性的途径之一，称为Break 诱导复制(BIR)。BIR通常用于修复单端DSB。这里的目标是 是为了了解该通路在双端双链断裂修复过程中是如何被抑制的。我们专注于 单链DNA RAD52退火法和DSB两端同时切除法的作用 Mre11-Rad50-Xrs2复合体。在目标#3中，我们重点讨论与切除无关的函数 同源重组过程中的DNA2核酸酶/解旋酶。

Recombination is essential in maintaining genome stability, and even minor deficiency in recombinational double-strand break (DSB) repair pathways results in cancer or other severe diseases. The initial processing of DNA DSBs to single strands, a process termed DNA end resection, is the critical first step of homologous recombination needed for the loading of damage response and repair proteins. Resection is tightly controlled in the cell cycle and determines the usage of homologous recombination versus nonhomologous end joining for repair. In yeast and human cells, the Mre11-Rad50-Nbs1/Xrs2 complex initiates resection, whereas Exo1 or Sgs1- Dna2 mediates extensive resection. Systematic studies of resection have thus far only been done in euchromatin, whereas we propose to study it in three different types of silenced heterochromatin. We designed many new assays to examine resection within transcriptionally silent chromatin in fission yeast (Aim #1). The fission yeast system provides an excellent model organism for this study as chromatin features are well conserved with those in human cells. In Aim #2 we focus on control of one of the most mutagenic pathways of DSB repair called Break Induced Replication (BIR). BIR is normally used for the repair of a single-end DSB. Here the goal is to understand how this pathway is suppressed during the repair of two-ended DSBs. We focus on the role of ssDNA annealing by Rad52 and synchronous resection of two ends of a DSB by the Mre11-Rad50-Xrs2 complex. In Aim #3 we focus on the resection-independent function of Dna2 nuclease/helicase during homologous recombination.