BIOCHEMICAL ROLE OF THE P53 GENE PRODUCT IN HUMAN CANCER

p53肿瘤抑制基因产物的突变失活是肿瘤发生的重要原因。 迄今为止在人类癌症中发现的最常见的遗传畸变。 了解p53在负生长控制中的生化作用， 可能导致识别新的生物标志物， 检测人类癌症以及开发新药 疗法大多数（大于95%）错义点突变 在p53基因中鉴定出的10个突变在p53基因的保守区域内聚集 位于氨基酸115和300之间，被指定为 构象域可以想象，在这个区域内的突变 破坏介导和/或调节蛋白质的正常结合， p53的肿瘤抑制活性。 为了支持这一假设，SV 40 DNA肿瘤病毒转化蛋白，大T抗原，结合到 p53的构象结构域，并诱导构象变化， 稳定蛋白质。构象变化也导致了蛋白质的丢失。 T抗原与p53的结合。构象突变中的错义突变 结构域也导致类似构象变化和 第53页。p53与一种或多种细胞同源物的相互作用 因此，构象结构域内的SV 40大T抗原可能是 被错义突变破坏假定的蛋白质或蛋白质， 在p53的构象结构域内的相互作用必须被鉴定， 开始阐明其生化功能。使用过量的 p53嵌合蛋白（p53[115-300]）来探测肺癌细胞裂解物，我们 已经能够分离出几种蛋白质， 野生型p53序列在氨基酸115至300之间。两种突变型p53 嵌合蛋白表现出显著降低的结合这些 proteins.本提案的具体目标是实现以下目标： 特征，识别，并确定这些相关性， 与p53相关的蛋白质在体外和体内都起作用。是 预计这些研究将进一步深入了解 肿瘤抑制功能的生化机制和调控 第53页。此外，影响表达的其他遗传改变 在p53构象域内相互作用的调节蛋白 可能在其他大约50%的 表达正常p53的人类肿瘤。

Mutational inactivation of the p53 tumor suppressor gene product is the most common genetic aberration identified in human cancer to date. Understanding the biochemical role of p53 in negative growth control could potentially lead to the identification of new biomarkers for early detection of human cancer as well as of the development of novel drug therapy. A majority (greater than 95%) of the missense point mutations identified in the p53 gene are clustered within a conserved region of p53 located between amino acids 115 and 300 that is designated the conformational domain. Mutations within this domain could conceivably disrupt the normal binding of proteins that mediate and/or regulate the tumor suppressor activity of p53. In support of this hypothesis, the SV40 DNA tumor virus transforming protein, large T-antigen, binds to the conformational domain of p53 and induces a conformational change that stabilizes the protein. The conformational change also results in loss of binding of T-antigen to p53. Missense mutations in the conformational domain also result in a similar conformational change and stabilization of p53. The interaction of p53 with a cellular homologue or homologue(s) of SV40 large T-antigen within the conformational domain thus may be disrupted by missense mutations. The putative protein or proteins that interact within the conformational domain of p53 must be identified to begin to elucidate its biochemical function. Using excess quantities of a p53 chimeric protein (p53[115-300]) to probe lung cancer cell lysates, we have been able to isolate several proteins that specifically bind to the wild-type p53 sequence between amino acids 115 to 300. Two mutant p53 chimeric proteins exhibited significantly reduced binding to these proteins. The specific aims of this proposal are directed toward the goal of characterizing, identifying, and determining the relevance of these proteins with respect to p53 function both in vitro and in vivo. It is anticipated that such studies will provide further insight into the biochemical mechanism and regulation of the tumor suppressor function of p53. In addition, other genetic alterations affecting expression of regulatory proteins that interact within the conformational domain of p53 might play a role in the pathogenesis of the other approximately 50% of human tumors that express normal p53.