Photodynamic effect of proflavine on 0X174 bacteriophage, its DNA replicative form and its isolated single-stranded DNA

In contrast to that what is observed with most inactivating agents, proflavine-mediated photoinactivation is about 10 times more efficient on double-stranded 0X174 replicative form DNA (RFI) than on isolated single-stranded 0X174 DNA. Both 0XRFI DNA and encapsidated DNA have similar sensitivities to proflavine and light treatment. With the three substrates studied, reactivation can occur through high multiplicity of infection and depends upon the cellular rec A gene product. No effect of the pol A, uvr A or lex A gene mutations has been found on either phage of DNA inactivation rates. The photodynamically induced lesions can be repaired, at least in part, by the SOS repair system induced in the host-cells by a 100 J x m-2 UV irradiation. SOS repair does not occur with bacteria (or spheroplasts) irradiated in the presence of chloramphenicol. Reversion frequency of the 0X174 amber mutations indicates that 1) photodynamically induced lesions are mutagenic whether the rec A gene product is present or not in the indicator bacteria; 2) induction of the SOS repair system is accompanied by a mutagenic process which results in a almost twofold increase of the reversion frequency; and 3) multiplicity reactivation occurs through a re ombinational process and is not mutagenic per se. (orig./AJ)