COMPARISON OF THE SEQUENCE SELECTIVITY OF THE DNA-ALKYLATING PLURAMYCIN ANTITUMOR ANTIBIOTICS DC92-B AND HEDAMYCIN

The sequence selectivity of DNA alkylation by the recently isolated pl uramycin antitumour antibiotic DC92-B has been investigated using two methods: a piperidine-induced strand-breaking procedure and a Tag DNA polymerase/linear amplification method. These techniques reveal that g uanines are the most reactive sites for alkylation and that the level of adduct formation at these sites is clearly sequence dependent. The highest levels of alkylation occurred at isolated guanines located in 5'-CGT sequences and also at the 5'-G in some 5'-CGG sequences. Isolat ed guanines in 5'-TGT sequences were also quite reactive. We have also reexamined, in parallel, the sequence selectivity of binding of the s tructurally-related compound hedamycin: the first known example of a b is(epoxide)-containing, DNA-alkylating pluramycin. Our Studies include d a more extensive sequence analysis of hedamycin binding than that pr eviously reported and we are able, therefore, to define more precisely the sequence preference. Despite significant differences in the stere ochemistry and substitution of their bis(epoxide) sidechains, hedamyci n and DC92-B exhibited very similar Sequence selectivities in our assa ys.