Studies Of DNA Mismatch Repair

工作总结：该项目的目标是了解MMR在正常真核细胞中的生物化学和遗传学，以及MMR基因突变如何导致环境相关的人类疾病。今年，我们研究了镉抑制MMR的机制。我们之前曾指出，酵母长期暴露在低微米浓度的镉中，这是一种已知的人类致癌物质，会导致高度变异性。在校对缺失和MMR缺失突变体中的突变特异性以及反应强烈地表明，镉降低了小错位和碱基错配的MMR能力。今年，我们发表了生化支持的假说，即镉通过损害Msh2-MSH6的DNA结合和ATP水解功能来抑制MMR，并通过外推，Msh2-Msh3。我们还发表了一篇关于DNA MMR生物化学的综合综述。 罕见的DNA合成错误通过复制后DNA错配修复(MMR)得到纠正。除了修复复制错误外，一些真核MMR蛋白还参与其他DNA交易，这些交易对基因组的稳定性、毒性和人类健康都是重要的。这些包括关键的环境应激反应途径，如修复双链DNA断裂和监测DNA损伤以发出凋亡信号。MMR蛋白还阻止同源性不完全的DNA序列之间的重组，它们参与减数分裂重组，它们既调节免疫球蛋白基因的体细胞高度突变，也调节与某些遗传性退行性疾病相关的稳定性或三重重复序列。MMR的缺失增加了突变率，减少了对某些形式的DNA损伤的凋亡，最终导致癌症。某些MMR基因的突变会导致不孕。该项目的目标是了解正常真核细胞中MMR蛋白功能的生物化学和遗传学，以及MMR基因突变如何导致环境相关疾病。

Summary of Work: The goals of this project are to understand the biochemistry and genetics of MMR in normal eukaryotic cells, and how mutations in MMR genes lead to environmentally associated human diseases. This year we investigated the mechanism by which cadmium inhibits MMR. We previously showed that chronic exposure of yeast to low microM concentrations of cadmium, a known human carcinogen, results in hypermutability. The mutation specificity along with responses in proofreading-deficient and MMR-deficient mutants strongly suggested that cadmium reduces the capacity for MMR of small misalignments and base-base mismatches. This year we published biochemical support for the hypothesis that cadmium inhibits MMR by impairing the DNA binding and ATP hydrolysis functions of Msh2-Msh6, and by extrapolation, Msh2-Msh3. We also published a comprehensive review of the biochemistry of DNA MMR. Rare DNA synthesis errors are corrected by post-replication DNA mismatch repair (MMR). In addition to their functions in repairing replication errors, some eukaryotic MMR proteins also participate in other DNA transactions that are important for genome stability, toxicity and human health. These include critical environmental stress-response pathways such as repair of double-strand DNA breaks and DNA damage surveillance to signal apoptosis. MMR proteins also prevent recombination between DNA sequences with imperfect homology, they participate in meiotic recombination, and they modulate both somatic hypermutation of immunoglobulin genes and the stability or triplet repeat sequences whose instability is associated with certain hereditary degenerative diseases. Loss of MMR increases mutation rates and decreases apoptosis in response to certain forms of DNA damage, ultimately leading to cancer. Mutations in certain MMR genes result in infertility. The goals of this project are to understand the biochemistry and genetics of MMR protein function in normal eukaryotic cells, and how mutations in MMR genes lead to environmentally associated diseases.