Determinants of cellular responses to p53

描述：（由申请人提供）取决于特定的蜂窝 在某些条件下，肿瘤抑制蛋白p53诱导生长停滞或介导 凋亡反应凋亡反应的失活，特别是， 与肿瘤发生过程以及抗肿瘤药物 肿瘤细胞到特定的治疗方法。由于p53的DNA结合活性 在对p53的每一种生理反应中起作用， 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。迄今为止 通过以下方法鉴定调节靶基因选择性的机制： p53已经消失了。本申请中提出的研究是 旨在检验细胞对p53的反应是由 通过调节其靶基因的选择性和表达缺陷， 特定靶基因的表达提供了缺陷性 肿瘤细胞中p53依赖的凋亡。先前的研究表明 差异p53依赖性调控的基因参与生长停滞， 细胞周期蛋白依赖性激酶抑制剂p21，相比之下， 凋亡，bax。将探讨这种选择性的分子基础 通过三个具体目标。首先，由于p53结合位点在p21和bax中， 启动子需要额外的基因特异性元件，以实现强大的p53依赖性 转录调控，研究建议阐明潜在的 这种顺式作用元件与特定的p53 结合位点以基因特异性方式影响转录。两 先前已经鉴定出肿瘤衍生的突变体， 诱导生长停滞，但选择性地失去了触发 凋亡虽然这两种突变体能够上调p22启动子， 两者均显示Bax启动子的缺陷性激活。在第二个目标中， 将检测这两种突变型p53蛋白的活性以阐明 这些特定的启动子效应的基础。三种肿瘤细胞系已经被 53有效上调p21启动子，但显示 bax的激活缺陷。第三个目标是确定分子基础 这种差异化的规定。对DNA的最佳治疗反应 许多化疗药物引起的损伤是凋亡而不是细胞 循环停滞阐明了导致 p53触发细胞凋亡的能力与抑制细胞凋亡的能力相比， 治疗性干预和克服化疗耐药的方法 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.