Sensitivity Mechanisms in Chromium Toxicity

描述（由申请人提供）：六价铬（CrVI）是一种有毒的DNA损伤剂，在大量职业中有充分的记录，是一种常见的环境污染物。Cr（VI）被美国毒物与疾病登记署和美国环保署列为20种最优先的有毒物质之一。Cr在生物系统中的最终氧化形式是Cr（III），其产生几种稳定的DNA加合物。我们最近发现Cr（III）-DNA加合物是Cr（VI）致突变的主要原因之一。我们的新数据表明Cr-DNA加合物在Cr（VI）的毒性中也起着重要作用。Cr-DNA加合物的毒性反应强烈依赖于一小群蛋白质的存在下，结合铬受损的染色质。该建议旨在测试我们的工作假设，即Cr-DNA加合物的细胞毒性作用是由损伤感觉蛋白对加合物的识别和加工所产生的二级DNA损伤的形成引起的。生物化学方法和下调损伤处理蛋白水平的细胞模型将用于获得支持所提出的假设的证据。我们构建了一系列的逆转录病毒siRNA编码载体，这将使我们能够检查各种蛋白质在靶原代人支气管上皮细胞的细胞毒性反应中的作用，这些细胞以前没有进行过机制研究。这项工作的结果预计将推进Cr（VI）损伤的主要靶细胞的分子理解，并确定损伤处理蛋白质，增强毒性的Cr-DNA修饰。

DESCRIPTION (provided by applicant): Hexavalent chromium (CrVI) is a toxic DNA-damaging agent with a well-documented exposure in a large number of occupations, and it is a common environmental contaminant. Cr(VI) is listed by the ATSDR and EPA as one of the top 20 high priority toxic agents. The final oxidative form of Cr in biological systems is Cr(lll) that produces several stable DNA adducts. We have recently found that Cr(III)-DNA adducts are one of the major causes of mutagenicity of Cr(VI). Our new data indicate that Cr-DNA adducts also play an important role in toxicity of Cr(VI). Toxic responses to Cr-DNA adducts were strongly dependent on the presence of a small group of proteins that bind to Cr-damaged chromatin. This proposal is designed to test our working hypothesis that cytotoxic effects of Cr-DNA adducts are caused by the formation of secondary DNA lesions generated as a result of the recognition and processing of adducts by damage sensory proteins. Biochemical approaches and cellular models with downregulated levels of damage-processing proteins will be used to gain evidence supporting the proposed hypothesis. We constructed a series of the retroviral siRNA-encoding vectors, which will allow us to examine the role of various proteins in the cytotoxic responses in the target primary human bronchial epithelial cells that have not been previously amenable to the mechanistic studies. The results of this work are expected to advance molecular understanding of Cr(VI) injury in the major target cells and to identify damage processing proteins that enhance toxicity of Cr-DNA modifications.