Studies on DNA repair in Bacillus subtilis. I. A cellular factor acting on gamma-irradiated DNA and promoting its priming activity for DNA polymerase I.

Initiation of new DNA synthesis was observed in B. subtilis cells upon gamma-ray irradiation followed by toluene treatment and incubation in the presence of the four deoxynucleotide triphosphates and Mg2+. This DNA synthesis took place in the absence of ATP and was refractory to 6-(p-hydroxyphenylazo)-uracil which is a specific inhibitor for the type III polymerase of Bacillus subtilis. This repair-type DNA synthesis was greatly reduced in mutant cells deficient in DNA polymerase I. Restoration of transforming activity of cellular DNA was found to occur in parellel with the above repair type DNA synthesis. A protein factor which enhances the priming activity of gamma-irradiated DNA for DNA polymerase I was detected in DNA-free extracts prepared from B. subtilis cells by means of lysis with a buffer containing lysozyme, Brij-58 and EDTA.