Effects of a single intrastrand d(GpG) platinum adduct on the strand separating activity of the Escherichia coli proteins RecB and RecA

RecB and RecA proteins play key roles in the process ofDNA recombination in Escherichia coli and both possess DNA unwinding activities which can displace short regions of duplex DNA in an ATP-dependent manner in vitro. We have examined the effect of the most abundant DNA adduct caused by the chemotherapeutic agent cM-diamminedichloroplatinum(II) on those activities. For this purpose, we have constructed a partially duplex synthetic oligonucleotide containing the intrastrand d(GpG) crosslink positioned at a specific site. We report here that both the DNA strand separating and DNA-dependent ATPase activities of the RecB protein are inhibited by the d(GpG) cis-ddp adduct. In contrast, neither the unwinding nor the ATPase activities of RecA protein appear to be perturbed by this lesion.