BIOCHEMICAL ROLE OF THE P53 GENE PRODUCT IN HUMAN CANCER

P53抑癌基因产物的突变失活是 迄今为止在人类癌症中发现的最常见的基因异常。 了解P53在负生长控制中的生化作用可能 可能导致早期发现新的生物标记物 人类癌症的检测和新药的开发 心理治疗。大多数(大于95%)错义点突变 在P53基因中发现的基因聚集在P53的保守区内 位于氨基酸115和300之间，被指定为 构象结构域。可以想象，这个区域内的突变可能 破坏介导和/或调节细胞周期的蛋白质的正常结合 P53的抑癌活性。为了支持这一假设，SV40 DNA肿瘤病毒转化蛋白是一种大T抗原，与 P53的构象结构域，并诱导构象变化 稳定蛋白质。构象的改变也导致了 T抗原与P53的结合。构象中的错义突变 结构域也会导致类似的构象变化和稳定性 P53。P53与一种或多种细胞内同系物的相互作用(S) 因此，构象结构域中的SV40大T抗原可能是 被错义突变破坏的。一种或多种推定的蛋白质 必须确定在p53构象结构域内的相互作用 开始阐明其生化功能。使用过量的 P53嵌合蛋白(P53[115-300])用于探测肺癌细胞裂解物 已经能够分离出几种特定结合到 野生型P53的氨基酸序列介于115到300之间。两个突变型p53 嵌合蛋白与这些蛋白的结合显著减少。 蛋白质。这项建议的具体目标是针对目标的 描述、识别和确定这些因素的相关性 与P53相关的蛋白质在体外和体内的功能。它是 预计这类研究将提供对 抑癌基因的生化机制及其调控 P53。此外，其他影响基因表达的基因改变 在p53构象结构域内相互作用的调节蛋白 可能在其他约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.