The involvement of an E. coli multiprotein complex in the complete repair of UV-damaged DNA

The bimodal nature of the E. coli uvrABC catalyzed incision reaction of UV irradiated DNA leads to potential excision of a 12-13 base long damaged fragment. However, the oligonucleotide fragment containing the UV-induced pyrimidine dimer is not released under non-denaturing in vitro reaction conditions. The uvrABC proteins, also, are stably bound to the incised DNA and do not turn over following the incision event. In this communication it is shown that damaged fragment release from the parental uvrABC incised DNA is dependent on either chelating conditions or upon the simultaneous addition of the uvrD gene product (helicase II) and the polA gene product (DNA polymerase I) when catalyzing concommitant polymerization of deoxynucleoside triphosphate substrates. The product of this multiprotein catalyzed series of reactions serves as a substrate for polynucleotide ligase which results in the restoration of the integrity of the strands of DNA. The addition of the uvrD protein to the incised DNA-uvrABC complex also results in turnover of only the uvrC protein. It is suggested that the repair processes of incision, excision, resynthesis and ligation are coordinately catalyzed by a protective complex of proteins in a 'repairosome' type of configuration.