Mu-1 directed inhibition of DNA breakdown in Escherichia coli, recA cells.

The spontaneous DNA breakdown exhibited by recA strains, is reduced after heat induction of a thermoinducible Mu-1 prophage. This inhibition is dependent upon RNA synthesis, suggesting that Mu-1 directs synthesis of a recBC nuclease inhibitor, analogous to the product of the lambda gam gene. The genetic evidence presented here shows that Mu-1 enables a lambda red gam phage to grow on a recA host. The in vitro assay for ATP-dependent exonuclease activity reveals a complete inhibition of this activity 30 min after induction of the Mu-1 prophage.