An additional function for bacteriophage λ rex: The rexB product prevents degradation of the λ O protein

The rex operon of bacteriophage λ excludes the development of several unrelated bacteriophages. Here we present an additional λ rexB function: it prevents degradation of the short-lived protein λ O known to be involved in λ DNA replication. We have shown that it is the product of rexB that is responsible for the stabilization of λ O: when a nonsense mutation is present in rexB, λ O protein is labile; suppression of the mutation by the corresponding nonsense suppressor causes partial restabilization of λ O. λ rexB also stabilizes λ O in trans. We discuss our results in relation to the function of rexB in λ DNA replication and its role in the protein degradation pathways of bacteriophage λ.