Mercuric ion inhibition of eukaryotic transcription factor binding to DNA.
Mercury has harmful effects in both rodents and humans. In rodent tissue culture cells exposed to HgCl(2), the metal ions were observed to concentrate in cell nuclei and to associate with chromatin. Thus, transcription factors and other proteins associated with chromatin are possible targets of mercuric ion toxicity. In this study, mercuric ions were found to inhibit the DNA binding activity of the Cys(2)His(2) zinc finger proteins transcription factor IIIA (TFIIIA) and Sp1. These factors are prototypes of the largest eukaryotic protein superfamily. Neither the presence of excess zinc ions nor beta-mercaptoethanol prevented inhibition by mercuric ions. Mercuric ions also inhibited DNA binding by the non-zinc finger protein AP2. Zinc finger-DNA binding was inhibited when both TFIIIA/5S RNA complex and TFIIIA alone were preincubated with concentrations as low as 15 microM mercuric ion. Inhibition occurred in less than 1 min and was not readily reversible. Mercuric ions also inhibited the digestion of DNA by the restriction enzymes BamHI or EcoRI. Inhibition of transcription factors as well as potentially other DNA binding proteins by micromolar concentrations of mercuric ion suggests additional biochemical mechanisms for mercury toxicity in promoting disease via alterations in gene transcription patterns.
Rodgers
J S
JS
Department of Biochemistry and Molecular Biology, University of Oklahoma College of Medicine, 800 Research Parkway, Room 448, Oklahoma City, OK 73104, USA.
Hocker
J R
JR
Hanas
R J
RJ
Nwosu
E C
EC
Hanas
J S
JS
D000818:Animals; D004247:DNA / Q000187:drug effects* / Q000378:metabolism; D004262:DNA Restriction Enzymes / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004347:Drug Interactions; D005260:Female; D008628:Mercury / Q000494:pharmacology*; D010053:Ovary / Q000187:drug effects / Q000502:physiology; D012341:RNA, Ribosomal, 5S / Q000235:genetics / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism; D050656:Transcription Factor AP-2; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D029867:Xenopus Proteins; D014982:Xenopus laevis; D015032:Zinc / Q000494:pharmacology; D016335:Zinc Fingers / Q000187:drug effects
D004268:DNA-Binding Proteins; D012341:RNA, Ribosomal, 5S; D016329:Sp1 Transcription Factor; D050656:Transcription Factor AP-2; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors; D029867:Xenopus Proteins; C493675:tfap2a protein, Xenopus; D004247:DNA; D004262:DNA Restriction Enzymes; D008628:Mercury; D015032:Zinc