An additional function for bacteriophage lambda rex: the rexB product prevents degradation of the lambda O protein.

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