Induction of AT-specific DNA-interstrand crosslinks by bizelesin in genomic and simian virus 40 DNA

Bizelesn is a bifunctional AT-specific DNA alkylating drug. Our study chara cterized the ability of bizelesin to induce interstrand crosslinks, a poten tial lethal lesion. In genomic DNA of BSC-1 cells, bizelesin formed from ap prox. 0.3 to 6.03 +/- 0.85 interstrand crosslinks per 10(6) base pairs, at 5-100 nM drug concentration, respectively, comparable to the number of tota l adducts previously determined in the same system (J.M. Woynarowski, M.M. McHugh, L.S. Gawron, T,A. Beerman, Biochemistry 34 (1995) 13042-13050). Biz elesin did not induce DNA-protein crosslinks or strand breaks. A model defi ned target, intracellular simian virus 40 (SV40) DNA, was employed to map a t the nucleotide level sites of bizelesin adducts, including potential inte rstrand crosslinks. Preferential adduct formation was observed at AT tracts which are abundant in the SV40 matrix associated region and the origin of replication. Many sites, including each occurrence of 5'-T(A/T)(4)A-3' co-m apped on both DNA strands suggesting interstrand crosslinks, although monoa dducts were also I formed. Bizelesin adducts in naked SV40 DNA were found a t similar sites. The localization of bizelesin-induced crosslinks in AT-ric h tracts of replication-related regions is consistent with the potent anti- replicative properties of bizelesin. Given the apparent lack of other types of lesions in genomic DNA, interstrand crosslinks localized in AT-rich tra cts, and to some extent perhaps also monoadducts, are likely to be lethal e ffects of bizelesin. (C) 1999 Published by Elsevier Science B.V. All rights reserved.