In this study, we have mapped the intracellular alkylation sites of
adozelesin and
bizelesin, two potent analogs of
CC-1065, in individual genes at the single-
nucleotide level. Human colon
carcinoma cells were treated with
adozelesin and
bizelesin, and the position of adducts were mapped within the PGK-1 and p53 genes by means of
ligation-mediated polymerase chain reaction. The monofunctional
alkylating agent adozelesin was found to alkylate genomic
DNA predominantly within 5'-(A/T)(A/T)A* sequences. Additional sites of alkylation were observed within 5'-(A/T)(G/C)(A/T)A* sequences; however, these were considered to represent sites of medium to low preference.
Bizelesin, a bifunctional analog capable of both
DNA monofunctional alkylation and
DNA interstrand cross-link formation, was also found to alkylate 5'-(A/T)(A/T)A* sequences. Putative
bizelesin DNA interstrand cross-link sites indicated that AT-rich sequences are preferred in the intervening sequence between the two cross-linked adenines. Both six- and seven-
nucleotide regions were identified as putative sites of
DNA interstrand cross-link formation with 5'-TTTTTTA*, 5'-TTTATCA* and 5'-GTACTAA* sequences being preferred. Non-
adenine bases are not observed as potential intracellular sites of either
DNA interstrand cross-linking formation or monofunctional alkylation. Thus, the patterns of alkylation induced by
adozelesin and
bizelesin in genomic
DNA are similar but not identical to that observed in purified
cell-free DNA.