Transcriptional regulation of apoptosis

描述（由申请方提供）：对细胞凋亡的抗性有助于肿瘤发生以及不良的治疗结果。肿瘤抑制因子p53介导两种主要的细胞反应，细胞周期阻滞和细胞凋亡，但这种细胞命运决定的分子基础仍然难以捉摸。有人提出，p53-独立的效应子和p53-依赖的基因表达之间的相互作用可能是细胞结果的关键决定因素。拟议的研究测试这一假设，通过检查SP/KLF家族成员和p53之间的相互作用，调节基因表达，侧重于p21 CIP 1作为衰减剂的凋亡反应的作用，并阐明是否改变在基础水平的表达的关键成员的凋亡途径有助于细胞命运的决定。位于启动子和第一内含子中的多个p53应答元件参与DNA损伤诱导的p21 CIP 1上调，其中p21 CIP 1启动子中的两个位点以不同的方式被调节。在第一个目标中，两种类型的p53位点之间的差异的分子基础将被阐明和p53，Sp1，和其他Sp/KLF家族成员之间的相互作用将被检查。其他细胞因子，如Sp/KLF家族成员在p53依赖性基因调控中的关键作用将作为影响细胞结果的一种手段来解决。细胞周期蛋白依赖性激酶抑制剂p21 CIP 1干扰细胞凋亡和影响细胞命运的能力已被发表的研究以及初步数据所证实。在第二个目标中，p21 CIP 1在减弱细胞死亡反应中的作用将被验证和表征，并且p21 CIP 1的这种有趣的作用的潜在分子基础将被阐明。调节细胞凋亡途径关键组分的基础表达水平是决定细胞命运结果的另一种机制。Bax基因中赋予Bax组成型转录调控的元件已经被鉴定。NHE 1是一种新型的p53靶基因，已显示其通过脱酰胺作用调节Bcl-XL的抗凋亡作用。在第三个目标中，Bax，NHE 1和Bcl-XL之间的分子相互作用将被探索，以确定这些机制是否可以解释特定肿瘤细胞的凋亡抗性表型。根据特定的细胞条件，肿瘤抑制蛋白p53诱导生长停滞或介导凋亡反应。对许多化疗剂引起的DNA损伤的最佳治疗反应是细胞死亡，而不是抑制细胞周期进程。阐明负责调节p53触发细胞凋亡与细胞停滞能力的分子机制可能会导致更有效的治疗干预和克服许多肿瘤中发现的化疗耐药表型的方法。公共卫生相关性：根据特定的条件，肿瘤抑制蛋白p53诱导生长停滞或介导凋亡反应。对许多化疗剂引起的DNA损伤的最佳治疗反应是细胞死亡，而不是抑制细胞周期进程。阐明负责调节p53触发细胞凋亡与细胞停滞能力的分子机制可能会导致更有效的治疗干预和克服许多肿瘤中发现的化疗耐药表型的方法。

DESCRIPTION (provided by applicant): Resistance to apoptosis contributes to tumorigenesis as well as poor therapeutic outcome. The tumor suppressor p53 mediates two predominant cellular responses, cell cycle arrest and apoptosis, but the molecular basis for this cell fate determination has remained elusive. It is proposed that an interplay between p53-independent effectors and p53-dependent gene expression may be the crucial determinant for cellular outcome. The proposed studies test this hypothesis by examining the interplay between Sp/KLF family members and p53 on regulating gene expression, focusing on the role of p21CIP1 as an attenuator of the apoptotic response, and elucidating whether alterations in basal levels of expression of key members of apoptotic pathways contribute to cell fate decisions. Multiple p53 response elements located in both the promoter and first intron are involved in the DNA damage-induced upregulation of p21CIP1 with the two sites in the p21CIP1 promoter being regulated in distinct manners. In the first aim, the molecular basis for the differences between the two types of p53 sites will be elucidated and the interplay between p53, Sp1, and other Sp/KLF family members will be examined. The key role of other cellular factors such as Sp/KLF family members in p53-dependent gene regulation will be addressed as a means for influencing cellular outcomes. The ability of the cyclin-dependent kinase inhibitor p21CIP1 to interfere with apoptosis and influence cell fate has been suggested by published studies as well as preliminary data. In the second aim, the role of p21CIP1 in attenuating the cell death response will be validated and characterized and the underlying molecular basis for this intriguing effect of p21CIP1 will be elucidated. Regulating the basal levels of expression of key components of apoptotic pathways is an alternative mechanism for determining cell fate outcomes. Elements in the bax gene that confer constitutive transcriptional regulation of Bax have been identified. NHE1 is a novel p53 target gene that has been shown to regulate the anti-apoptotic effects of Bcl-XL via deamidation. In the third aim, the molecular interplay between Bax, NHE1, and Bcl-XL will be explored to determine whether such mechanisms can explain the apoptotic resistant phenotype of particular tumor cells. Depending upon particular cellular conditions, the tumor suppressor protein p53 induces growth arrest or mediates an apoptotic response. The optimal therapeutic response to DNA damage caused by many chemotherapeutic agents is cell death rather than inhibition of cell cycle progression. Elucidating the molecular mechanisms that are responsible for regulating 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. PUBLIC HEALTH RELEVANCE: Depending upon particular conditions, the tumor suppressor protein p53 induces growth arrest or mediates an apoptotic response. The optimal therapeutic response to DNA damage caused by many chemotherapeutic agents is cell death rather than inhibition of cell cycle progression. Elucidating the molecular mechanisms that are responsible for regulating 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.