PHOTOACTIVATED GILVOCARCIN-V INDUCES DNA-PROTEIN CROSS-LINKING IN GENES FOR HUMAN RIBOSOMAL-RNA AND DIHYDROFOLATE-REDUCTASE

The nature of DNA interactions with photoactivated gilvocarcin V has b een analyzed at the gene level in both rRNA and dihydrofolate reductas e genes of human fibroblasts, utilizing a modified Southern hybridizat ion technique. Neither interstrand DNA crosslinking nor RNA linkage to DNA was detected. However, we consistently observed in both genes ret arded DNA bands appearing in a dose-dependent fashion following exposu re to photoactivated gilvocarcin V. These retarded bands were enhanced when genomic DNA was prepared without proteinase K treatment, suggest ing involvement of protein in this DNA interaction. Because these band s disappear following proteinase K treatment, it is probable that phot oactivated gilvocarcin V induces DNA-protein crosslinking.