The Human Mismatch Repair Proteins and Carcinogenesis

描述(申请人提供)：遗传性非息肉病性结直肠癌(HNPCC)是最常见的癌症易感综合征之一，以早发结直肠癌以及子宫内膜癌、卵巢癌、皮肤癌、胃癌和上尿路癌为特征。与人类有丝分裂错配修复(MMR)相关的七个基因中的两个，hMSH2和hMLH1的种系突变占HNPCC病例的绝大多数，而hMSH6和hPMS2 MMR基因的突变很少。此外，10-40%的散发性肿瘤表现出遗传不稳定性(突变表型)，这是人类错配修复缺陷的标志。 自从我们最初发现hMSH2和hMLH1以来，我们可以说已经积累了最完整的MMR和MMR相关基因/蛋白质/试剂库。在上一次资助期间，我们询问了人类MMR的生物化学、遗传学、细胞和肿瘤生物学。我们详细阐述了MMR的新机制，hMSH2 HNPCC错义突变的功能后果，并修订了MMR突变在癌变过程中的原因和后果。在这一持续申请中，我们建议：i)使用人类蛋白质异源二聚体作为模型，首次在任何生物体中对MutS同源物(MSH)的错配/损伤识别和ATP处理进行第一次完整的生物物理和蛋白质遗传学表征，II。)人MutL同源物(MLH)与ATP结合的人MSH滑动夹相互作用和ATP加工活性的生物物理和蛋白质遗传学特征。研究MSH/MLH信号滑动钳与BLM解旋酶ExoI和增殖细胞核抗原IV的相互作用和切除机制。)确定MMR和V.HNPCC错义突变在MLH、hExoI和增殖细胞核抗原生化功能上的功能缺陷。逐步重建整个MMR信号和切除修复过程，以表征与完全修复反应相关的纳米级生物物理事件。 这些研究将提供人类MMR组分的分子和功能作用，详细说明促进HNPCC的信号传递过程，并帮助确定明确的分子靶点，用于功能性治疗干预和提高人类癌症的临床疗效。

DESCRIPTION (provided by applicant): Hereditary NonPolyposis Colorectal Cancer (HNPCC) is one of the most frequent cancer predisposition syndromes and is characterized by early onset of colorectal cancers as well as cancers of the endometrium, ovary, skin, stomach and upper urinary tract. Germline mutations in two of the seven mitotic human mismatch repair (MMR) related genes, hMSH2 and hMLH 1, account for the vast majority of HNPCC cases, while mutations in the hMSH6 and hPMS2 MMR genes are rare. In addition, 10-40% of sporadic tumors display the genetic instability (mutator phenotype) that is a hallmark of human mismatch repair defects. Since our initial discovery of hMSH2 and hMLH1, we have arguably accumulated the most complete repertoire of MMR and MMR-related genes/proteins/reagents. In the last grant period we interrogated the biochemistry, genetics, cell and tumor biology of human MMR. We have detailed a novel mechanism for MMR, the functional consequences of hMSH2 HNPCC missense mutations, and revised the causes and consequences of MMR mutations in the process of carcinogenesis. In this continuing application we propose to: I.) perform the first complete biophysical and proteogenetic characterization of mismatch/lesion recognition and ATP-processing ofMutS homologs (MSH) in any organism using the human protein heterodimers as a model, II.) biophysical and proteo-genetic characterization of the interactions and ATP processing activities of the human MutL homologs (MLH) with ATP-bound human MSH sliding clamps, IlI.) examine the interaction and excision mechanics of MSH/MLH signaling sliding clamps with the BLM helicase, ExoI, and PCNA, IV.) determine the functional defects of HNPCC missense mutations on MLH, hExoI, and PCNA biochemical function in MMR, and V.) gradual reconstitution of the entire MMR signaling and excision-repair process in order to characterize the nanoscale biophysical events associated with the complete repair reaction. These studies will provide the molecular and functional roles of the human MMR components, detail the signaling processes that contribute to HNPCC, and assist in the identification of clear molecular targets for functional therapeutic intervention and increased clinical efficacy in human cancer.