Cloning, sequencing, and genetic characterization of regulatory genes, rinA and rinB, required for the activation of staphylococcal phage phi 11 int expression.

The int gene of staphylococcal bacteriophage phi 11 is the only viral gene responsible for the integrative recombination of phi 11. To study the regulation of int gene expression, we determined the 5' end of the transcript by S1 mapping. The presumed promoter is located just 22 nucleotides upstream of the int open reading frame in a region which is conserved between phi 11 and a closely related staphylococcal phage, L54a. To clone the possible regulatory gene, a vector which contained the reporter gene, xylE, of Pseudomonas putida under the control of the phi 11 int promoter was constructed. Subsequently, a 2-kb DNA fragment from the phi 11 genome, which mapped distal to the int gene, was shown to increase the XylE activity from the int promoter. Sequencing and subsequent deletion analysis of the 2-kb fragment revealed that two phi 11 regulatory genes, rinA and rinB, were both required to activate expression of the int gene. Northern (RNA) analysis suggested that the activation was, at least partly, at the transcriptional level. In addition, one of these regulatory genes, rinA, was capable of activating L54a int gene transcription.