AFFECTS OF ARSENITE ON DNA DAMAGE INDUCIBLE RESPONSE

描述：通过饮用水接触砷与以下因素有关： 增加人类癌症的风险，以及许多其他功能障碍。 研究人员已经证明，虽然亚砷酸盐（可能的 致癌形式的砷）不是基因诱变剂，它作为共诱变剂 通过干扰DNA修复 然而，DNA修复酶在体外 对砷不敏感，这意味着砷对DNA修复的影响， 细胞不是通过酶抑制。 调查人员认为， 亚砷酸盐对DNA修复的抑制是由于干扰了 p53依赖性途径控制细胞对DNA损伤的反应。 人类 暴露于砷，例如饮用水中的砷，发生在很长一段时间内， 时间 该提案将解决长期、低水平的影响， 亚砷酸盐治疗的一些p53相关终点。 因为他们有 发现啮齿动物细胞暴露于低水平的亚砷酸盐会产生耐受性， 而人体细胞没有，重点将放在人体细胞上。 的 具体目标是首先确定亚砷酸盐及其 代谢产物二甲基胂酸（DMAA）干扰细胞 X射线对正常人二倍体成纤维细胞DNA损伤的影响 和角质形成细胞。 DNA损伤诱导的反应包括瞬时细胞 细胞周期阻滞，p53蛋白丰度增加， p-53下游的基因（特别是gadd 45和p21）。 二是 研究人员将确定人类细胞是否经历了 突变，基因扩增，或由于长期， 低水平的亚砷酸盐或DMAA暴露（单独或与低剂量的UVB）显示， 与类似处理相比，基因组不稳定性频率增加 没有改变的细胞。 第三，他们将研究氧化剂的作用 强调亚砷酸盐的行动，通过确定是否有任何影响， 1（测量p53依赖性功能）和2（遗传效应 可被抗坏血酸盐、抗生育酚或 N-乙酰半胱氨酸 最后，通过表达克隆基因， 他们克隆了2个cDNA，fau（一种据称的肿瘤）， 抑制基因）和ASR 2（其产物在细胞凋亡中起作用）。 的 研究者将确定FAU或ASR 2，当过表达时， 导致人类细胞基因组不稳定。

DESCRIPTION: Arsenic exposure via drinking water is associated with increased risk of human cancers, as well as a number of other dysfunctions. The investigators have demonstrated that although arsenite (the likely carcinogenic form of arsenic) is not a gene mutagen, it acts as a comutagen by interfering with DNA repair. However, DNA repair enzymes in vitro are not sensitive to arsenite implying that arsenite s effect on DNA repair in cells is not via enzyme inhibition. The investigators suggest that inhibition of DNA repair by arsenite results from an interference with p53-dependent pathways controlling cellular responses to DNA damage. Human exposure to arsenic, e.g. in drinking water, occurs over a long period of time. This proposal will address the effects of long term, low level arsenite treatment of a number of p53-related endpoints. Because they have found that rodent cells exposed to low levels of arsenite develop tolerance, whereas human cells do not, the emphasis will be on human cells. The specific aims are first to determine the ability of arsenite and its metabolite dimethylarsinic acid (DMAA) to interfere with the cellular resoponse to x-ray-induced DNA damage in normal human diploid fibroblasts and keratinocytes. DNA-damage-in-ducible responses include transient cell cycle arrest, increase in p53 protein abundance, and the up-regulation of genes downstream of p-53(particularly gadd45 and p21). Second, the investigators will determine whether human cells which have undergone mutation, gene amplification, or transformation as a result of long term, low level arsenite or DMAA exposure(alone or with low doses of UVB) show increased frequencies of genomic instability compared with similarly treated cells which were not altered. Third, they will study the role of oxidant stress in arsenite's action by determining whether any effects seen in aims 1 (where p53-dependent fucntions are measured) and 2 (where genetic effects are measured) can be blocked by ascorbate, atocopherol, or N-acetyl-cysteine. Lastly, by expression cloning for genes which confer resistance to arsenite, they have cloned 2 cDNAs, fau (a purported tumor suppressor gene) and asr2 (whose product plays a role in apoptosis). The investigators will determine whether fau or asr2 will, when overexpressed, contribute to genomic instability in human cells.