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 of DNA recombinat ion in Escherichia coli and both possess DNA unwinding activities whic h 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 cis-diamminedichloroplatinum(II) on those activities. For this purpose, we have constructed a partially duplex synthetic oligonucleotide containing the intrastrand d(GpG) cr osslink positioned at a specific site. We report here that both the DN A strand separating and DNA-dependent ATPase activities of the RecB pr otein 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.