Determinants of cellular responses to p53

描述：(由申请人提供)取决于特定的蜂窝 条件下，肿瘤抑制蛋白P53诱导生长停滞或介导 一种细胞凋亡性反应。尤其是使凋亡反应失活， 与肿瘤的发生和耐药有关 肿瘤细胞对特定疗法的影响。由于P53的DNA结合活性 在对P53的每一种生理反应中都扮演着一个角色，P53的能力 在不同的靶基因中进行选择以引发特定的细胞反应 可能是调节其生物学功能的核心。到目前为止， 靶基因选择性调控机制的鉴定 P53一直难以捉摸。在本申请中提出的研究是 旨在测试细胞对P53的反应是由 通过调节其靶基因的选择性和表达中的缺陷 特定的靶基因为缺陷提供了分子基础 肿瘤细胞中P53依赖性的细胞凋亡。先前的研究表明 对参与生长停滞的基因的P53依赖的不同调控， 细胞周期蛋白依赖的激酶抑制物p21，与参与 细胞凋亡，Bax。我们将探索这种选择性的分子基础。 通过三个具体目标。首先，由于p53在p21和bax中的结合部位 启动子需要额外的基因特异性元件才能产生强大的p53依赖性 转录调控，建议进行研究以阐明潜在的 这些顺式作用元件与特定的p53相互作用的机制 结合部位以基因特有的方式影响转录。二 此前已发现肿瘤来源的突变体保留了这种能力 导致生长停滞，但选择性地失去了触发 细胞凋亡。虽然这两个突变体能够上调p22启动子， 两者都显示了Bax启动子的激活缺陷。在第二个目标中 这两个突变型P53蛋白的活性将被检测以阐明 这些启动子特异性效应的基础。三个肿瘤细胞系已经被 其中53页有效地上调了p21启动子，但显示 BAX的激活有缺陷。第三个目的是确定分子基础 对于这种不同的规定。对DNA的最佳治疗反应 许多化疗药物造成的损害是细胞凋亡，而不是细胞 周期拘禁。阐明导致这一现象的分子机制 P53触发细胞凋亡的能力与抑制相比可能导致更有效的 治疗干预与克服化疗耐药的途径 在许多肿瘤中发现的表型。

DESCRIPTION: (provided by applicant) Depending upon particular cellular conditions, the tumor suppressor protein p53 induces growth arrest or mediates an apoptotic response. Inactivation of the apoptotic response, in particular, has been implicated in the process of oncogenesis as well as in the resistance of tumor cells to particular therapies. Since the DNA binding activity of p53 plays a role in each of the physiological responses to p53, the ability of p53 to select among various target genes to elicit a particular cellular response may be central to the regulation of its biological function. To date, the identification of a mechanism for the regulation of target gene selectivity by p53 has been elusive. The research that is proposed in this application is designed to test the hypothesis that the cellular response to p53 is determined by regulation of its target gene selectivity and that defects in the expression of particular target genes provide the molecular basis for defective p53-dependent apoptosis in tumor cells. Previous studies have shown differential p53-dependent regulation of a gene involved in growth arrest, the cyclin-dependent kinase inhibitor p21, as compared to one involved in apoptosis, bax. The molecular basis for this selectivity will be explored through three specific aims. First, since p53 binding sites in the p21 and bax promoters require additional gene-specific elements for robust p53-dependent transcriptional regulation, studies are proposed to elucidate the underlying mechanisms by which such cis-acting elements cooperate with particular p53 binding sites to affect transcription in a gene-specific manner. Two tumor-derived mutants had previously been identified which retain the ability to induce growth arrest but had selectively lost the capacity to trigger apoptosis. While the two mutants were capable of upregulating the p22 promoter, both showed defective activation of the bax promoter. In the second aim the activity of these two mutant p53 proteins will be examined to elucidate the basis for these promoter-specific effects. Three tumor cell lines have been identified in which p.53 efficiently upregulated the p21 promoter but showed defective activation of bax. The third aim is to determine the molecular basis for this differential regulations. The optimal therapeutic response to DNA damage caused by many chemotherapeutic agents is apoptosis rather than cell cycle arrest. Elucidating the molecular mechanisms that are responsible for the ability of p53 to trigger apoptosis versus arrest may lead to more effective therapeutic intervention and a way to overcome the chemotherapeutic-resistant phenotype found in many tumors.