DNA-binding of sulfur-containing metabolites from 35S-(pentachlorobutadienyl)-L-cysteine in bacteria and isolated renal tubular cells.

S-(Pentachlorobutadienyl)-L-cysteine (PCBC) is the penultimate metabolite formed from the nephrocarcinogen hexachlorobutadiene (HCBD). It is activated by cysteine conjugate beta-lyase (beta-lyase) to yield thioacylating metabolites thought to be responsible for PCBC-induced cytotoxicity and mutagenicity. We have investigated the beta-lyase dependent DNA-binding of metabolites formed from 35S-PCBC in Salmonella typhimurium (S. typhimurium) TA100 and in rat renal proximal tubule cells. 35Sulfur was found in DNA isolated from S. typhimurium (410 +/- 93 DNA-adducts per 10(6) nucleotides) and renal cells (68 or 97 DNA-adducts per 10(6) nucleotides). Enzymatic hydrolysis of the isolated DNA to yield 3'-nucleotide phosphates and fractionation of the hydrolysate by HPLC indicated the presence of 3 distinct, 35S-containing metabolites which did not coelute with unchanged 3'-nucleotide phosphates and likely represent DNA constituents modified by 35S-PCBC metabolites. Identical retention volumes were obtained for altered bases isolated from bacteria and from renal cells. The results obtained indicate that PCBC metabolites may covalently bind to DNA and implicate genotoxic mechanisms in HCBD-induced nephrocarcinogenicity.