摘要：Since environmental exposure to arsenicals has been correlated with a high skin cancer risk among populations exposed to sunlight, it is possible that arsenicals might interfere with the repair of damage to DNA (mostly thymine dimers) resulting from the ultraviolet rays in sunlight. To test this hypothesis, strains of E. coli , differing from each other only in one or more repair functions, were exposed to UV light and then plated in the presence or absence of sodium arsenite. Survival after irradiation of wild type E. coli (WP2) was significantly decreased by 0.5 mM arsenite. This effect was also seen in strains which are unable to carry out excision repair, suggesting that arsenite inhibits one or more steps in the post-replication repair pathways. This is confirmed by the finding that arsenite has no effect on the post-irradiation survival of a recA mutant, which does not carry out post-replication repair. Mutagenesis after ultraviolet irradiation depends on the rec + and lex + genes. Arsenite decreases mutagenesis in strains containing these genes. In order to determine its mechanism of action, dose-response relationships of arsenite on a number of cellular functions were carried out. The most sensitive cellular functions found were the induction of β-galactosidase and the synthesis of RNA. Since error-prone repair in E. coli is an inducible process, the inhibition of mutagenesis after UV irradiation may be the result of inhibition of messenger RNA synthesis. Full text Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (662K), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References . 229 230 231 232 233
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