title: Effects of exposure of DNA to methyl mercury on its activity as a template-primer for DNA polymerases.
abstract: A previous publication [Frenkel, Cain, and Chao, Biochem. Biophys. Res. Commun. 127, 849-856 (1985)] described the observation that double-stranded DNA which was briefly exposed to methyl mercury (MeHg) and purified to remove free methyl mercury was transcribed at a higher rate by RNA polymerase II from wheat germ. The specificity of this phenomenon has now been investigated by examining the activity of this MeHg-exposed DNA as a template-primer for DNA polymerases. DNA synthesis by the bacteriophage T4-induced DNA polymerase was higher with the MeHg-exposed DNA as a template-primer than with control DNA. In contrast, the rate of DNA synthesis by E. coli DNA polymerase I was lower with the MeHg-exposed DNA as template-primer. With both enzymes (as well as with RNA polymerase II), after denaturation of the MeHg-exposed and control DNAs the differences in template activity were either eliminated or markedly reduced. The enzymes are thus able to detect a MeHg-induced alteration in DNA. In contrast, circular dichroism, a physical method that is sensitive to conformational changes in DNA, did not detect any difference between the MeHg-exposed and control DNAs.
mesh_terms: D004247:DNA / Q000378:metabolism*; D004256:DNA Polymerase I / Q000378:metabolism; D004261:DNA Replication / Q000187:drug effects*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D007700:Kinetics; D008767:Methylmercury Compounds / Q000633:toxicity*; D013604:T-Phages / Q000201:enzymology; D013698:Templates, Genetic
chemical_list: D008767:Methylmercury Compounds; D004247:DNA; D012321:DNA-Directed RNA Polymerases; D004256:DNA Polymerase I; D004259:DNA-Directed DNA Polymerase; C020771:methylmercury hydroxide