Identification of two new bacteriophage T4 genes that may have roles in transcription and DNA replication.

We have identified two bacteriophage T4 genes, 45.1 and 45.2, that map in the intergenic space between phage replication genes 46 (which encodes a recombination initiation protein) and 45 (which encodes a bifunctional protein required in replication and transcription). The existence of genes 45.1 and 45.2 had not been previously recognized by mutation analysis of the T4 genome. We cloned the T4 gene 45.1/45.2 segment, determined its nucleotide sequence, and expressed its two reading frames at high levels in bacterial plasmids. The results predicted molecular weights of 11,400 (100 amino acids) for gp45.1 and 7,500 (62 amino acids) for gp45.2. We also determined that in T4-infected Escherichia coli, genes 45.1 and 45.2 are cotranscribed with their distal neighbor, gene 45, by at least one mode of transcription. In an accompanying report (K. P. Williams, G. A. Kassavetis, F. S. Esch, and E. P. Geiduschek, J. Virol. 61:600-603, 1987), it is shown that the product of gene 45.1 is the so-called T4-induced 15K protein, an RNA polymerase-binding protein of unknown role in phage development. Possibly, T4 genes 45.2, 45.1, and 45 constitute an operon for host RNA polymerase-binding phage proteins. Jointly with Williams et al., we propose the term rpb (RNA polymerase-binding) to refer to T4 genes whose products bind to the host RNA polymerase and have adopted the name rpbA for T4 gene 45.1.