Tolerance of spontaneous and induced DNA damage in yeast

基因组DMA是多种内源性和外源性DMA损伤剂的靶标。 由此产生的损伤是突变和基因组不稳定的重要来源，并有助于 人类的遗传病、癌症和衰老。为了减轻DNA损伤的有害影响， 有专门的切除机制来移除病变，以恢复双链DNA的完整性。 尽管存在这些高效的切除修复机制，但病变可以持续和 在DNA合成过程中会遇到。一些病变改变了受影响的碱基配对属性 核苷酸，导致DNA合成过程中的突变，而其他核苷酸则可能阻止 复制分叉的进度。为了抵消聚合酶阻断损伤的存在，细胞 拥有冗余的损伤容忍机制，促进DNA损伤的旁路，从而 允许复制继续。这些旁路机制包括高保真的串交换和 从未受损的姐妹染色单体复制信息的同源重组过程，如 以及涉及专门化跨病变招募的潜在容易出错的途径 合成(TLS)DNA聚合酶。由于基因操作相对容易，酵母菌 酿酒酵母为研究这些高度保守的基因提供了一个很好的模型系统 DNA损伤处理机制。本提案的目标1和目标2将重点放在 绕过/耐受自发的DNA损伤，重点是定义基因控制 无错误旁路与易出错旁路。目标3和目标4将扩展这些研究以检查 模型诱变剂紫外线(UV)诱导的损伤的细胞周期依赖的后果。 虽然大多数紫外线诱导的突变被认为发生在S阶段的病变旁路期间，但我们也将 检查在切除修复过程中出现的突变。最后，目标5将解决 除了病变旁路活性外，TLS聚合酶是否也对 延长复制型DNA聚合酶结合的错配。总而言之，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.