BACTERIOPHAGE-P2 OGR AND BACTERIOPHAGE-P4 DELTA-GENES ACT INDEPENDENTLY AND ARE ESSENTIAL FOR BACTERIOPHAGE-P4 MULTIPLICATION

Satellite bacteriophage P4 requires the products of the late genes of a helper phage such as P2 for lytic growth. Expression of the P2 late genes is positively regulated by the P2 ogr gene in a process requiring P2 DNA replication. Transactivation of P2 late gene expression by P4 requires the P4 δ gene product and works even in the absence of P2 DNA replication. We have made null mutants of the P2 ogr and P4 δ genes. In the absence of the P4 δ gene product, P4 multiplication required both the P2 ogr protein and P2 DNA replication. In the absence of the P2 ogr gene product, P4 multiplication required the P4 δ protein. In complementation experiments, we found that the P2 ogr protein was made in the absence of P2 DNA replication but could not function unless P2 DNA replicated. We produced P4 δ protein from a plasmid and found that it complemented the null P4 δ and P2 ogr mutants.