title: Nonspecific cleavage of phi X174 RFI deoxyribonucleic acid by bleomycin.
abstract: The covalently closed circular duplex deoxyribonucleic acid (DNA) of phi X174 underwent progressive conversion to nicked and linear DNA with increasing bleomycin/phi X174 RFI DNA molecule ratios. The formation of linear DNA (a double-strand break) occurred under limited reaction conditions as low as an average of 0.2 single-strand break/phi X174 RFI DNA molecule. As bleomycin-produced linear DNA was further fragmented by bleomycin, a broad distribution of DNA fragments without notable concentrations of unique size was formed. Restriction enzymes PstI and SstII did not generate discrete fragments from bleomycin-produced full-length linear phi X174 DNA, nor did bleomycin cleavage generate discrete fragments from HpaII or PstI digests of phi X174 RFI. These findings suggest that bleomycin does not act at a few specific sites on phi X174 RFI DNA. The single-strand nick appeared to be the preferred site for bleomycin action for a second cleavage in a phi X174 molecule.
mesh_terms: D010584:Bacteriophage phi X 174 / Q000032:analysis*; D001665:Binding Sites; D001761:Bleomycin / Q000494:pharmacology*; D055598:Chemical Phenomena; D002621:Chemistry; D004262:DNA Restriction Enzymes; D004279:DNA, Viral / Q000302:isolation & purification*; D004591:Electrophoresis, Polyacrylamide Gel
chemical_list: D004279:DNA, Viral; D001761:Bleomycin; D004262:DNA Restriction Enzymes