Transcriptional regulation of apoptosis

描述（由申请人提供）：对细胞凋亡的抵抗有助于肿瘤的发生以及不良的治疗效果。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独立效应物和p53依赖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。这些研究通过检测Sp/KLF家族成员与p53在调节基因表达方面的相互作用来验证这一假设，重点关注p21CIP1作为凋亡反应衰减器的作用，并阐明凋亡通路关键成员基础表达水平的改变是否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应答元件参与了DNA损伤诱导的p21CIP1上调，p21CIP1启动子中的两个位点以不同的方式受到调节。在第一个目标中，将阐明两种类型p53位点之间差异的分子基础，并研究p53， Sp1和其他Sp/KLF家族成员之间的相互作用。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手段加以解决。已发表的研究和初步数据表明，周期蛋白依赖性激酶抑制剂p21CIP1能够干扰细胞凋亡并影响细胞命运。在第二个目标中，将验证和表征p21CIP1在减轻细胞死亡反应中的作用，并阐明p21CIP1这种有趣作用的潜在分子基础。调节凋亡通路关键成分的基础表达水平是决定细胞命运结局的另一种机制。已经确定了bax基因中赋予bax组成性转录调控的元件。NHE1是一种新的p53靶基因，已被证明通过脱酰胺调节Bcl-XL的抗凋亡作用。在第三个目标中，我们将探索Bax、NHE1和Bcl-XL之间的分子相互作用，以确定这种机制是否可以解释特定肿瘤细胞的抗凋亡表型。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。对许多化疗药物引起的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展。阐明负责调节p53触发细胞凋亡与阻滞能力的分子机制可能会导致更有效的治疗干预，并找到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.