Stimulation of recombination in phage T4 by nitrous acid-induced lesions

Recombination of phage T4 can be stimulated more than sixfold above the spontaneous level by treatment with nitrous acid, indicating that the lesions induced by this agent are strongly recombinogenic. Two temperature sensitive mutants defective in exonuclease functions showed less than the wild-type spontaneous level of recombination even after nitrous acid treatment and a ligase mutant showed a highly elevated frequency of recombination after treatment. Since these same mutants have analogous effects on spontaneous recombination, the results imply that nitrous acid-induced lesions in DNA stimulate a recombinational repair process similar in some of its enzymic steps to spontaneous recombination.