Enzymology Of Eukaryotic Mismatch Repair

描述（由申请人提供）：DNA错配修复是一种关键的突变避免途径，由于几个原因而具有临床意义。失活的错配修复是一种常见形式的遗传性结肠癌的原因，并已牵连在一个子集的散发性肿瘤的发展。错配修复缺陷也对癌症治疗有影响，因为该途径的失活使细胞对某些抗肿瘤药物的细胞毒性作用具有抗性，这是该系统参与DNA损伤反应的结果。也许令人惊讶的是，错配修复功能也是产生某些突变所必需的，例如（CAG）n重复序列的扩增，这是许多神经退行性疾病的主要原因。通过阐明人类错配修复的分子本质，我们希望了解它在控制突变发生中的作用。为此，我们提出了四条工作路线：（1）现有的信息链导向的人类错配修复的性质表明，反应的过程是由一组不断发展的蛋白质-蛋白质和蛋白质-DNA相互作用，并启动错配识别活动MutS 1和MutS 2修复事件在显着的方式不同。通过分析所选择的多蛋白质和多蛋白质-DNA复合物的性质，我们希望进一步阐明MutS 1和MutS 2启动的修复事件的机制。(2)（CAG）n神经退行性疾病的体细胞扩增阶段依赖于错配修复活性MutS 2和MutL 1，可发生在有丝分裂后细胞中，表明修复DNA合成参与了该过程。将在提取物和纯化系统中讨论人错配修复系统对（CAG）n重复元件的加工性质。(3)错配修复功能是SN 1 DNA甲基化的检查点和凋亡反应所必需的。使用生化方法，我们将追求的ATR损伤信号激酶的MutS 1和MutL 1依赖性激活的机制，响应O 6-甲基鸟嘌呤，这类药物产生的主要细胞毒性病变。(4)与洛雷纳比斯实验室的合作研究将解决人类错配识别系统识别和处理病变的结构基础。

DESCRIPTION (provided by applicant): DNA mismatch repair is a key mutation avoidance pathway that is of clinical interest for several reasons. Inactivation of mismatch repair is the cause of a common form of hereditary colon cancer and has been implicated in the development of a subset of sporadic tumors. Mismatch repair defects also have implications for cancer therapy because inactivation of the pathway renders cells resistant to the cytotoxic effects of certain anti-tumor drugs, a consequence of participation of the system in the DNA damage response. Perhaps surprisingly, mismatch repair function is also required for the production of certain mutations, such as the expansion of (CAG)n repeat sequences, the primary cause of a number of neurodegenerative diseases. By elucidating the molecular nature of human mismatch repair, we hope to understand its roles in controlling the occurrence of mutation. To this end we propose four lines of work: (1) Available information on the nature of strand-directed human mismatch repair indicates that the course of the reaction is dictated by an evolving set of protein-protein and protein-DNA interactions, and that repair events initiated by the mismatch recognition activities MutS1 and MutS2 differ in significant ways. By analyzing the nature of selected multi-protein and multi-protein-DNA complexes, we hope to further clarify the mechanisms of MutS1- and MutS2-initiated repair events. (2) The somatic expansion stage of (CAG)n neurodegenerative diseases, which depends on the mismatch repair activities MutS2 and MutL1, can occur in postmitotic cells, suggesting involvement of repair DNA synthesis in this process. The nature of processing of (CAG)n repeat elements by the human mismatch repair system will be addressed in both extract and purified systems. (3) Mismatch repair function is required for checkpoint and apoptotic responses to SN1 DNA methylators. Using a biochemical approach, we will pursue the mechanisms of MutS1- and MutL1-dependent activation of the ATR damage-signaling kinase in response to O6-methylguanine, the primary cytotoxic lesion produced by this class of drug. (4) Collaborative studies with the laboratory of Lorena Beese will address the structural basis of lesion recognition and processing by the human mismatch recognition system.