Tolerance of spontaneous and induced DNA damage in yeast

基因组DNA是多种内源性和外源性DNA损伤剂的靶点。 由此产生的病变是诱变和基因组不稳定性的重要来源，并有助于 遗传疾病、癌症和人类衰老。为了减轻DNA损伤的有害影响， 存在去除损伤以恢复双链体DNA完整性的专门切除机制。 尽管存在这些高效的切除修复机制，但病变可以持续存在， 在DNA合成过程中遇到的。一些病变改变了受影响的碱基配对特性 核苷酸，导致DNA合成过程中的突变，而其他人则有可能阻止DNA合成。 复制分叉的进度。为了抵消聚合酶阻断病变的存在，细胞 具有冗余的损伤耐受机制，以促进绕过DNA损伤，从而 允许复制继续。这些旁路机制包括高保真链切换和 同源重组过程从未受损的姐妹染色单体复制信息，如 以及潜在的易出错的途径，涉及招募专门的跨病变 合成（TLS）DNA聚合酶。由于基因操作相对容易， 酿酒酵母为研究这些高度保守的 DNA损伤处理机制本提案的目标1和2将侧重于 旁路/耐受自发性DNA损伤，重点是定义遗传控制， 无错误旁路路径与易出错旁路路径。目标3和4将扩大这些研究， 由模型诱变剂，紫外线（UV）光诱导的损伤的细胞周期依赖性后果。 虽然大多数紫外线诱导的突变被认为发生在S期的病变旁路过程中，但我们也将 检查切除修复过程中出现的突变。最后，目标5将解决 除了它们的病变旁路活性外，TLS聚合酶是否也对 通过复制型DNA聚合酶掺入的延伸错配。这些研究将 促进我们对真核基因组损伤相关机制的理解， 不稳定，这是人类疾病发展的核心过程。

Genomic DMA is the target of a wide variety of endogenous and exogenous DMA-damaging agents. The resulting lesions are an important source of mutagenesis and genome instability, and contribute to genetic disease, cancer and aging in humans. To alleviate the deleterious effects of DNA damage, there are specialized excision mechanisms that remove lesions to restore the integrity of duplex DNA. In spite of the presence of these highly-efficient excision repair mechanisms, lesions can persist and be encountered during DNA synthesis. Some lesions alter the base-pairing properties of the affected nucleotide, leading to mutations during DNA synthesis, while others have the potential to block the progress of a replication fork. To counteract the presence of polymerase-blocking lesions, cells possess redundant damage tolerance mechanisms to promote the bypass of DNA damage, thereby allowing replication to continue. These bypass mechanisms include high-fidelity strand-switching and homologous recombination processes that copy information from an undamaged sister chromatid, as well as potentially error-prone pathways that involve the recruitment of specialized translesion synthesis (TLS) DNA polymerases. Because of the relative ease of genetic manipulation, the yeast Saccharomyces cerevisiae provides an excellent model system for studying these highly conserved DNA damage processing mechanisms. Aims 1 and 2 of this proposal will focus on the bypass/tolerance of spontaneous DNA damage, with an emphasis on defining the genetic control of the error-free versus error-prone bypass pathways. Aims 3 and 4 will expand these studies to examine the cell cycle-dependent consequences of lesions induced by a model mutagen, ultraviolet (UV) light. While most UV-induced mutations are assumed to occur during lesion bypass in S phase, we also will examine mutations that arise in the context of the excision repair process. Finally, Aim 5 will address whether, in addition to their lesion bypass activity, the TLS polymerases also are important for extending mismatches incorporated by replicative DNA polymerases. Together, these studies will advance our understanding of the damage-related mechanisms that contribute to eukaryotic genome instability, a process that is central in the development of human diseases.