The Role of p53 and 14-3-3 in Genomic Instability

描述（由申请人提供）：基因组不稳定性是癌症的一个标志，也是促进肿瘤发展和向恶性发展的一个有利特征。已知p53肿瘤抑制因子在基因组稳定中起主要作用。然而，p53执行其“基因组守护者”功能的机制尚不清楚。在初步研究中，我们已经确定14-3-3 - γ，一种已知与p53肿瘤抑制因子相互作用的蛋白质，可以导致一种形式的基因组不稳定，表现为内复制和产生含有bbbb4n DNA含量的细胞。我们发现，这种活性发生在缺乏功能性p53的细胞中，但不会发生在p53保持活性的细胞中。由于多倍体是发生在非整倍体之前的一种不稳定状态，我们假设14-3-3 γ水平升高时可能会降低基因组的稳定性。为了支持这一点，有报道称14-3-3在肺癌中的表达升高，我们的初步数据表明14-3-3 γ是这些肿瘤中过度表达的亚型之一。由于14-3-3 γ与p53蛋白发生物理相互作用，并且由于14-3-3 γ介导的rereplication表型发生在缺乏功能性p53的情况下，我们假设p53通过两种蛋白质之间的直接物理相互作用抑制14-3-3 γ引起基因组不稳定的能力。为了验证这一点，我们将通过检测14-3-3 γ对细胞周期控制蛋白功能、DNA复制起始和细胞周期检查点的影响来确定1)14-3-3 γ是否会导致内重复，2)野生型p53是否可以抑制内重复，以及这是否需要与14-3-3 γ直接物理相互作用，3)表征14-3-3在人肺肿瘤中的表达。

DESCRIPTION (provided by applicant): Genomic instability is a hallmark of cancer and an enabling feature that facilitates tumor development and advancement to malignancy. The p53 tumor suppressor is known to play a major role in the stabilization of the genome. However, the mechanism by which p53 executes it's function as "guardian of the genome" is unclear. In preliminary studies we have determined that 14-3-3gamma, a protein known to interact with the p53 tumor suppressor, can cause a form of genomic instability that is manifested by endoreduplication and production of cells with > 4N DNA content. We have found that this activity occurs in cells that lack a functional p53, but does not occur in cells where p53 remains active. Because polyploidy is an unstable condition that precedes aneuploidy, we postulate that 14-3-3gamma may decrease genomic stability when present at elevated levels. In support of this it has been reported that 14-3-3 expression is elevated in lung cancer and our preliminary data indicates that 14-3-3gamma is one of the isoforms that is overexpressed in these tumors. Because 14-3-3gamma physically interacts with the p53 protein and because the 14-3-3gamma-mediated rereplication phenotype occurs in the absence of a functional p53 we hypothesize that p53 suppresses 14-3-3gamma's ability to cause genomic instability through a direct physical interaction between the two proteins. To test this we will determine 1) whether 14-3-3gamma causes endoreduplication by examining its affect on the function of cell cycle control proteins, initiation of DNA replication, and cell cycle checkpoints, 2) whether wild-type p53 can suppress the endoreduplication and whether this requires a direct physical interaction with 14-3-3gamma and 3) characterize 14-3-3 expression in human lung tumors.