Environmentally-modulated cytosine deamination in genome instability and cancer

胞苷脱氨为脱氧尿苷是生殖细胞和癌细胞中突变的主要来源。 碱基切除和错配修复途径从双链DNA中去除脱氧尿苷。然而，在这方面， 这种损伤通常发生在复制、转录和转录后形成的单链DNA中。 暴露在DNA破坏剂中哺乳动物细胞还表达AID/APOBEC家族的酶， 催化ssDNA中的胞苷脱氨基作用，其异常活性与致癌作用有关。像 它们靶向的ssDNA，APOBEC酶的表达由多种环境因子诱导 这表明这些暴露可能在致癌作用中起重要作用， 酶和底物水平。APOBEC胞苷脱氨酶损伤核DNA的程度， 与环境DNA损伤剂的潜在协同作用，以及脱氨基诱导的 突变与癌症病因的关系尚不清楚。同样不清楚的是脱氨基胞苷是如何在细胞内加工的。 ssDNA本提案的目标是描述胞苷脱氨基诱导的细胞凋亡的机制和来源。 突变及其对环境诱发癌症的可能贡献。目的我将解决，如果 人类癌症中APOBEC诱导突变的数量与疾病的临床测量相关 进展和预后。通过APOBEC诱导的突变改变癌症相关基因也将 被确定。AIM II将确定脱氧尿苷转换为ssDNA中的碱基位点如何影响 诱变和异位重组。将测量脱氨基诱导的突变和重组 在酵母中缺乏损伤耐受机制来访问这些途径在突变中的作用， 易位回避目的III将解决人染色体上APOBECs的致突变能力 细胞系模型中的DNA。诱导ssDNA形成和/或APOBEC的影响环境暴露 表达将得到解决。全基因组测序将用于识别“有风险”的基因组特征， APOBEC介导的突变。这些目标将提供对细胞和环境的理解 胞苷脱氨基诱导突变的机制及其对致癌作用的贡献。

Cytidine deamination to deoxyuridine is a major source of mutation in both the germ-line and cancer cells. Base excision and mismatch repair pathways remove deoxyuridine from double stranded DNA. However, this lesion occurs commonly in single-strand (ss) DNA formed during replication, transcription, and after exposure to DNA damaging agents. Mammalian cells also express the AID/APOBEC family of enzymes that catalyze cytidine deamination in ssDNA and whose aberrant activity has been linked to carcinogenesis. Like the ssDNA they target, expression of APOBEC enzymes is induced by a variety of environmental agents suggesting these exposures may have an important role in carcinogenesis by increasing both APOBEC enzyme and substrate levels. The extent to which APOBEC cytidine deaminases damage nuclear DNA, their potential synergism with environmental DNA damaging agents, and the contribution of deamination-induced mutation to cancer etiology are unknown. Also unclear is how deaminated cytidines are processed within ssDNA. The goal of this proposal is to characterize mechanisms and sources of cytidine deamination-induced mutation and their possible contribution to environmentally-induced cancer. AIM I will address if the number of APOBEC-induced mutations in human cancers correlates with clinical measures of disease progression and prognosis. The alteration of cancer-related genes by APOBEC-induced mutations will also be determined. AIM II will determine how conversion of deoxyuridine to abasics sites in ssDNA impacts mutagenesis and ectopic recombination. Deamination-induced mutation and recombination will be measured in yeast lacking damage tolerance mechanisms to access these pathways' roles in mutation and translocation avoidance. AIM III will address the mutagenic capacity of APOBECs on human chromosomal DNA in a cell line model. The impact environmental exposures that induce ssDNA formation and/or APOBEC expression will be addressed. Whole genome sequencing will be used to identify genome features "at risk" of APOBEC-mediated mutation. These aims will provide an understanding of cellular and environmental mechanisms governing cytidine deamination-induced mutation and their contribution to carcinogenesis.