Sensitivity Mechanisms in Chromium Toxicity

描述(申请人提供)：六价铬(CrVI)是一种有毒的DNA损伤剂，在许多职业中有充分的暴露记录，它是一种常见的环境污染物。铬(VI)被ATSDR和EPA列为前20种高优先级毒剂之一。在生物体系中，铬的最终氧化形式是铬(111)，它能产生几种稳定的DNA加合物。我们最近发现，铬(III)-DNA加合物是铬(VI)致突变性的主要原因之一。我们的新数据表明，铬-DNA加合物在铬(VI)的毒性中也起着重要作用。对铬-DNA加合物的毒性反应强烈依赖于与铬损伤的染色质结合的一小部分蛋白质的存在。这一建议旨在验证我们的工作假设，即铬-DNA加合物的细胞毒性效应是由于损伤感觉蛋白识别和处理加合物而产生的继发性DNA损伤造成的。生化方法和损伤处理蛋白水平下调的细胞模型将被用来获得支持所提出的假说的证据。我们构建了一系列逆转录病毒siRNA编码载体，这将使我们能够检查各种蛋白质在靶向原代人支气管上皮细胞细胞毒反应中的作用，这些细胞以前不适合机制研究。这项工作的结果有望促进对主要靶细胞中铬(VI)损伤的分子理解，并识别能够增强铬-DNA修饰毒性的损伤处理蛋白。

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.