[Regulation of int gene expression in phage phi 81]

Phi 81 phage, like lambda, was shown to possess, in addition to cI (repressor) gene, two other genes--cII and cIII, essential for immunity establishment. Expression of phi 81 int gene is positively controlled by cII and cIII gene products. The products of cII and cIII genes of phi 81 phage do not complement analogous lambda genes functions.