Mechanisms of transcriptional repression by p53 during hypoxic stress

描述(申请人提供)：细胞缺氧是一种生理上相关的细胞应激，可触发一系列与组织修复、血管生成和肿瘤发生有关的细胞反应。这种现象的一个主要细胞成分是肿瘤抑制因子P53，它可以通过低氧应激稳定下来。与DNA损伤应激时观察到的反式激活现象相反，低氧似乎具有明显不同的转录调控机制，尽管许多下游细胞效应是相似的。这意味着P53可以通过几条不相交的途径来介导其许多肿瘤抑制功能。这项建议的目的是确定P53如何在低氧应激期间抑制肿瘤进展。为了实现这一目标，我们将使用一系列低氧调节的P53结构来识别在低氧过程中特异下调的基因。我们将使用表达微阵列技术和染色质免疫沉淀相结合的方法，在细胞培养模型中识别P53抑制的直接靶点。补充的小鼠肿瘤研究将被用来验证一般和特定的基因抑制对肿瘤缺氧区肿瘤细胞凋亡的重要性。这些研究将是未来确定P53转录抑制的功能后果的实验所必需的。肿瘤中出现的低氧浓度(缺氧)通常会导致更具侵袭性的肿瘤的形成。抑癌基因P53在缺氧性肿瘤中经常发生突变，有助于肿瘤的生长。了解p53如何调节缺氧性肿瘤的基因表达将有助于识别新的靶向癌症治疗的途径。

DESCRIPTION (provided by applicant): Cellular hypoxia is a physiologically relevant cellular stress that triggers a host of cellular responses involved in tissue repair, angiogenesis, and tumorigenesis. A major cellular component of this phenomena is the tumor suppressor p53, which is stabilized by hypoxic stress. In contrast to transactivation phenomena observed during DNA damaging stress, hypoxia appears to have a distinctly different mechanism of transcriptional regulation, even though many of the downstream cellular effects are similar. This implies that p53 can mediate a number of its tumor suppressive functions through several non-intersecting pathways. The objective of this proposal is to determine how p53 suppresses tumor progression during hypoxic stress. To achieve this goal we will use a series of hypoxia regulated p53 constructs to identify genes that are specifically downregulated during hypoxia. We will use a combination of expression microarray technology and chromatin immunoprecipitation to identify direct targets of p53 repression in a cell culture model. Complementary mouse tumor studies will be used to verify the importance of general and specific gene repression on tumor cell apoptosis in the hypoxic regions of tumors. These studies will be essential for future experiments defining the functional consequences of transcriptional repression by p53. The low oxygen concentrations (hypoxia) that occur in tumors often lead to the formation of more aggressive tumors. The tumor suppressor gene p53 is frequently mutated in hypoxic tumors, aiding in the progression of tumor growth. Understanding how p53 regulates gene expression in hypoxic tumors will lead to the identification of new pathways to target for cancer therapies.