The Human Mismatch Repair Proteins and Carcinogenesis

描述（由申请人提供）：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，其特征在于结直肠癌以及子宫内膜癌、卵巢癌、皮肤癌、胃癌和上尿路癌的早期发病。HNPCC病例的绝大多数是由7个有丝分裂人类错配修复（MMR）相关基因中的两个hMSH 2和hMLH 1的种系突变引起的，而hMSH 6和hPMS 2 MMR基因的突变是罕见的。此外，10-40%的散发性肿瘤显示遗传不稳定性（突变体表型），这是人类错配修复缺陷的标志。 自从我们最初发现hMSH 2和hMLH 1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/试剂库。在上一个资助期，我们询问了人类MMR的生物化学、遗传学、细胞和肿瘤生物学。我们详细介绍了MMR的一种新机制，hMSH 2 HNPCC错义突变的功能后果，并修订了致癌过程中MMR突变的原因和后果。在本持续申请中，我们提出：I.）使用人蛋白质异源二聚体作为模型，在任何生物体中进行MutS同源物（MSH）的错配/损伤识别和ATP加工的第一个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滑动夹的相互作用和ATP加工活性的生物物理和蛋白质遗传学表征，III.）检查MSH/MLH信号滑动夹与BLM解旋酶、ExoI和PCNA的相互作用和切除机制，IV.）确定HNPCC错义突变对MMR中MLH、hExoI和PCNA生化功能的功能缺陷，以及V.）整个MMR信号传导和切除修复过程的逐渐重建，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，详细说明导致HNPCC的信号传导过程，并协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.