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 in duced by bizelesin in genomic DNA of BSC-1 cells, as well as intracell ular-and purified simian virus 40 (SV40) DNA, were examined. Alkaline sucrose sedimentation analysis indicated a nonrandom distribution of h eat-labile damage in BSC-1 cell genomic DNA with frequencies of 1-60 l esions/10(6) base pairs (bp) for bizelesin concentrations from 10 to 4 00 nM, respectively. Extrapolation of these data suggested that, at 0. 15 nM bizelesin, similar to 10(2) adducts per cell may be sufficient t o inhibit cell growth by 90% (D-10). While the frequency of bizelesin adducts in intracellular SV40 DNA was comparable to that in genomic DN A, higher levels of lesion formation are observed with purified SV40 D NA. 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 a t 50-100 bp resolution) are found in regions centered at 4200, 3900, 4 700, and similar to 5200. The location of these regions of intense biz elesin bonding coincides with the sites of potential cross-links predi cted 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 indic ated 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. Biz elesin-induced interstrand cross-links have been demonstrated directly in the 3943-4451 SV40 DNA fragment by alkaline electrophoresis.