Radiation sensitivity of a mutant of Escherichia coli K-12 associated with DNA replication: evidence for a new repair function.

The isolation and properties of a new radiation sensitive mutant of Escherichia coli K-12 are described which shows a correlation between radiation sensitivity and replication of irradiated DNA. The mutation, called rer, is located between arg B and pur D loci. The mutant, when grown in tryptone broth after irradiation, is sensitive to UV and lambda-rays and incorporates little or no 3H-thymidine but in minimal glucose-salts medium both the radiation sensitivity and incorporation of 3H-thymidine remain identical to that of the parent strain. Studies with a temperature sensitive double mutant rer dnaC show that 1 hr incubation of irradiated cells at 42 degrees C before their transfer to 30 degrees C results in higher survival as compared to their incubation at 30 degrees C only. It is suggested that rer controls the replication of irradiated DNA and thus regulates the coordination between replication and repair of DNA.