The in vivo cross-linking of proteins and DNA by heavy metals.
Cross-linking of proteins to DNA in live, intact Novikoff ascites hepatoma cells exposed in vitro to different concentrations of CuSO4, Pb(NO3)2, HgCl2, and AlCl3 was studied. Protein-DNA complexes were separated by high-speed centrifugation of cells solubilized in buffered 4% sodium dodecyl sulfate and assayed by electrophoretic separation of proteins associated with the DNA-containing pellets. Concentration dependence experiments showed that the optimal cross-linking occurred at metal concentration of 0.5 mM for CuSO4, HgCl2, and AlCl3 while the optimal cross-linking for Pb(NO3)2 was at 5 mM. For some metals at concentrations higher than optimal, the amounts of cross-linked proteins decreased significantly. Immunochemical analysis of the cross-linked proteins using antibodies to matrix, chromatin, lamins, and cytokeratin fractions demonstrated that some, but not all, members of these protein families became cross-linked to the DNA. Each metal exhibited a cross-linking pattern of its own, different from those of the other metals. Radioactive labeling experiments showed that all the metals tested became associated with the DNA-protein pellets within 1 h after their addition to the incubation medium. However, hexavalent chromium required more than 2 h before appearing in the DNA-protein pellets in significant amounts.
D000535:Aluminum / Q000494:pharmacology*; D000077410:Aluminum Chloride; D017607:Aluminum Compounds; D000818:Animals; D002712:Chlorides; D003300:Copper / Q000494:pharmacology*; D019327:Copper Sulfate; D004247:DNA / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D007163:Immunosorbent Techniques; D007854:Lead / Q000494:pharmacology*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D008297:Male; D008627:Mercuric Chloride / Q000494:pharmacology*; D008970:Molecular Weight; D009566:Nitrates / Q000494:pharmacology*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D017607:Aluminum Compounds; D002712:Chlorides; D009566:Nitrates; D011506:Proteins; D007854:Lead; D000077410:Aluminum Chloride; D008627:Mercuric Chloride; C017461:lead nitrate; D003300:Copper; D004247:DNA; D000535:Aluminum; D019327:Copper Sulfate