Design, synthesis, and sequence selective DNA cleavage of functional models of bleomycin. 1. Hybrids incorporating a simple offal-complexing moiety of bleomycin and lexitropsin carriers.

The syntheses of functional models for bleomycin, which are composed of a simple analog of the metal-complexing moiety of bleomycin and oligo-N-methylpyrrole peptide DNA-binding moieties, are described. The extent and the relative rate of their cleavage of DNA in the presence of reductants were determined independently by an ethidium binding assay and by agarose gel electrophoresis experiments. The rate of DNA cleavage increases with the number of N-methylpyrrole units in the carrier moiety. The sequence selectivity of DNA cleavage was demonstrated by polyacrylamide sequencing gel electrophoresis of cleavage reactions on two 5'-32P labeled restriction fragments: a 158 bp GC-rich fragment from pBR322 and a 241 bp AT-rich fragment fragment from SV40. Comparison of the sequence selectivity with that of bleomycin A2 indicates that the poly-N-methylpyrrole moiety directs the hybrid compounds to AT-rich sequences of DNA. High-resolution denaturing gel electrophoresis of DNA cleaved by the model compounds reveals that 3' phosphate is produced exclusively, indicating that the chemistry of DNA cleavage differs from that of bleomycin.