Repair of DNA double-strand breaks in Escherichia coli cells requires synthesis of proteins that can be induced by UV light.

The repair of DNA double-strand breaks in Escherichia coli cells irradiated with gamma rays occurs only after new proteins are synthesized in response to damage introduced in the genome DNA. One protein whose synthesis is thus induced is the recA protein, and previous work has shown that recA- cells do not repair double-strand breaks. However, inducing recA protein by treating cells with nalidixic acid does not induce repair of double-strand breaks, so this repair requires more than the presence of the recA protein. When repair of double-strand breaks is blocked, the genome DNA is degraded by an endonuclease-like action. Evidence is presented to show that the inducible inhibition of DNA degradation after x-irradiation [Pollard, E. C. & Randall, E. P. (1973) Radiat. Res. 55, 265] is probably caused by the inducible repair of DNA double-strand breaks.