title: The enhanced rate of transcription of methyl mercury-exposed DNA by RNA polymerase is not sufficient to explain the stimulatory effect of methyl mercury on RNA synthesis in isolated nuclei.
abstract: Previous work demonstrated two stimulatory effects of methyl mercury on nucleic acid synthesis: (1) in isolated nuclei, methyl mercury stimulates RNA synthesis which is catalyzed by RNA polymerase II [Frenkel and Randles, J. Biol. Chem. 257, 6275-6279 (1982)]. (2) Brief exposure of purified DNA to methyl mercury increases the rate of its transcription by purified RNA polymerase II [Frenkel, Cain, and Chao, Biochem. Biophys. Res. Commun. 127, 849-856 (1985)]. The latter effect was considered as a possible mechanism of the former. Two lines of evidence are presented here which demonstrate that the latter effect is not a sufficient explanation for the former. (1) Mercuric perchlorate has been found to increase the rate of DNA transcription by purified polymerase and the template properties of the mercuric perchlorate-exposed DNA have been found to resemble those of methyl mercury-exposed DNA. Nevertheless, mercuric perchlorate has been shown not to stimulate RNA synthesis in isolated HeLa nuclei. (2) In isolated nuclei of the B50 rat neuroblastoma cell line, RNA synthesis has been found to be stimulated only minimally by methyl mercury. Nevertheless, RNA polymerase II purified from the B50 cells has been found to transcribe methyl mercury-exposed DNA at a higher rate than unexposed control DNA.
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism*; D004247:DNA / Q000187:drug effects* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008628:Mercury / Q000494:pharmacology; D017669:Mercury Compounds; D008767:Methylmercury Compounds / Q000494:pharmacology*; D010472:Perchlorates / Q000494:pharmacology; D012313:RNA / Q000096:biosynthesis / Q000187:drug effects*; D012319:RNA Polymerase II / Q000378:metabolism*; D013698:Templates, Genetic; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D017669:Mercury Compounds; D008767:Methylmercury Compounds; D010472:Perchlorates; D012313:RNA; C054683:mercuric perchlorate; D004247:DNA; D012319:RNA Polymerase II; C020771:methylmercury hydroxide; D008628:Mercury