ANTISENSE SEQUENCE-DIRECTED CROSS-LINKING OF DNA OLIGONUCLEOTIDES BY MITOMYCIN-C

Oligodeoxyribonucleotides (ODNs) conjugated with mitomycin C (MC) via (-CH2-)(n) tethers of different lengths (n = 6, 12) to their terminal 5'-phosphate were synthesized, and their interaction with target compl ementary single-stranded DNA oligonucleotides was investigated. MC, a clinically used natural anticancer drug, is known to act as a bioreduc tive alkylating agent of duplex DNA with a remarkable preference for 5 '-d(CG) sequences. The usual enzymatic bioreductive techniques known t o trigger MC to alkylate DNA were employed in the reaction between the MC-oligonucleotide conjugates and their targets radiolabeled by P-32 at their 5'-phosphate. A slow-moving radiolabeled product, detected by polyacrylamide gel electrophoresis using phosphorimaging techniques, was obtained in 15-25% yield with complementary DNA as target. Formati on of these products was dependent upon complementary duplex formation . Evidence is presented that the DNA target is alkylated by the mitomy cin C moiety of the ODN conjugate at the 2-amino group of a guanine ba se. These findings suggest that the MC-ODN conjugates may be useful sp ecific inhibitors of cellular or viral gene expression. To our knowled ge this is the first report on ODN conjugates of a reductively activat ed drug of known therapeutic value.