Characterization:novel genotoxic stress-regulated gene

描述（由申请人提供）：细胞持续暴露于各种环境因子，其中一些可诱导DNA损伤，即遗传毒性应激。细胞对遗传毒性应激的反应是复杂的，因此，需要更多的研究来更好地了解控制这种反应的机制。在这里，我们提出了一个新的基因，我们命名为PIQ（p53调节的智商蛋白），编码的智商基序蛋白。IQ基序促进蛋白质与钙调蛋白（CaM）的相互作用。CaM是一种钙结合蛋白，控制着几个重要的信号事件。这里提出的证据表明，PIQ确实与钙调素结合。此外，与匹配的正常组织相比，PIQ mRNA在原发性结肠肿瘤中过表达，并且PIQ响应于遗传毒性应激和p53激活而下调。p53依赖性基因毒性应激诱导的细胞凋亡中，p53依赖性基因毒性应激诱导的细胞凋亡重要的是，CD 4A启动子含有预测由CaM依赖性信号通路调节的调节元件。因此，我们提出，在未应激的细胞中，PIQ可能通过干扰钙调素依赖性信号传导事件来负调控CRAMA表达，而遗传毒性应激后PIQ下调可部分通过钙调素依赖性途径促进CRAMA上调。我们的总体假设是，PIQ是细胞凋亡的负调节因子，结肠癌中较高水平的PIQ表达可能会改变细胞凋亡的阈值，从而部分促进结肠肿瘤的发生。本文提出了三个具体目标，以进一步表征PIQ，以阐明其在细胞对遗传毒性应激反应中的作用，特别是在结肠癌的发生和/或进展中的作用。具体目标1是研究PIQ在p53和遗传毒性应激诱导的细胞凋亡中的作用。具体目标2是研究PIQ负调控CCRIA启动子表达的机制。具体目标3是在原发性结肠肿瘤及其匹配的正常组织的较大池中分析mRNA和蛋白质水平的PIQ表达，并评价肿瘤PIQ状态与临床病理特征之间的关系。

DESCRIPTION (provided by applicant): Cells are constantly exposed to a variety of environmental agents some of which induce DNA damage i.e. genotoxic stress. Cellular responses to genotoxic stress are complex and therefore, more studies are needed to better understand the mechanisms that control such responses. Here we propose to characterize a novel gene, which we have named PIQ (p53-regulated IQ protein) that codes for an IQ motif protein. IQ motifs promote protein interactions with calmodulin (CaM). CaM is a calcium-binding protein that controls several important signaling events. Evidence presented here show that PIQ does indeed bind to CaM. Furthermore, PIQ mRNA is overexpressed in primary colon tumors when compared with matching normal tissues and that PIQ is down-regulated in response to genotoxic stress and p53 activation. PUMA is a key mediator of p53- dependent genotoxic stress-induced apoptosis and our results indicate that PIQ down-regulates PUMA promoter expression. Importantly, PUMA promoter harbors regulatory elements that are predicted to be regulated by CaM-dependent signaling pathways. We, therefore, propose that in unstressed cells, PIQ may negatively regulate PUMA expression by interfering with CaM-dependent signaling events and PIQ downregulation following genotoxic stress serves to promote PUMA upregulation partly via CaM-dependent pathways. Our overall hypothesis is that PIQ is a negative modulator of apoptosis and that higher levels of PIQ expression noted in colon cancer may alter the threshold of apoptosis and consequently contribute in part to colon tumorigenesis. Three specific aims are proposed here to further characterize PIQ in order to elucidate its role in cellular response to genotoxic stress in general and in the development and/or progression of colon cancer in particular. Specific Aim 1 is to investigate the role of PIQ during p53 and genotoxic stress-induced apoptosis. Specific Aim 2 is to investigate the mechanism by which PIQ negatively regulates PUMA promoter expression. Specific Aim 3 is to analyze PIQ expression at the mRNA and protein levels in a larger pool of primary colon tumors and their matching normal tissues and to evaluate a relationship between tumor PIQ-status and the clinicopathologic features.