Effects of bizelesin (U-77779), a bifunctional alkylating minor groove agent, on genomic and simian virus 40 DNA.

Bizelesin is a bifunctional covalent minor groove binding agent which forms adducts with 3'-adenines on opposite DNA strands. DNA lesions induced by bizelesin in genomic DNA of BSC-1 cells, as well as intracellular and purified simian virus 40 (SV40) DNA, were examined. Alkaline sucrose sedimentation analysis indicated a nonrandom distribution of heat-labile damage in BSC-1 cell genomic DNA with frequencies of 1-60 lesions/10(6) base pairs (bp) for bizelesin concentrations from 10 to 400 nM, respectively. Extrapolation of these data suggested that, at 0.15 nM bizelesin, approximately 10(2) adducts per cell may be sufficient to inhibit cell growth by 90% (D10). While the frequency of bizelesin adducts in intracellular SV40 DNA was comparable to that in genomic DNA, higher levels of lesion formation are observed with purified SV40 DNA. Chromatin structure has little effect on localization of bizelesin adducts since treatment of either infected cells or purified SV40 DNA reveals a similar pattern of drug-induced damage. Bizelesin adduction sites (mapped on the SV40 genome as thermally-induced strand breaks at 50-100 bp resolution) are found in regions centered at 4200, 3900, 4700, and approximately 5200. The location of these regions of intense bizelesin bonding coincides with the sites of potential cross-links predicted using the 5'-T-(A/T)4-A-3' sequence. The analysis of bizelesin adducts at the sequence level in the 3943-4451 SV40 DNA fragment indicated that 40% of total damage was in potential cross-linking sites and an additional 35% in the 5'-A-(A/T)4-A-3' monoalkylating sites.(ABSTRACT TRUNCATED AT 250 WORDS)