Coordinated regulation of the cI and int genes in coliphage λ and specificity of the cII/cIII activators

Abstract

Expression of the cI (repressor) and int (integrase) genes in the λ lysogenic pathway has been studied by following protein synthesis in uv-irradiated cells. Gene expression following infection by λ +, a phage carrying an intact repressor gene, and by λ vir, a phage carrying operator mutations with reduced affinity for the repressor, substantiated previous findings on the coordinated regulation of these two genes, and showed that their expression can be dissociated from that of other early genes. Experiments with λ hybrid phages showed that the cII gene products of λ imm21 and of λ imm22, which are of origin of phages 21 and P22, can activate Int synthesis from P I of λ origin. Possible homology between the various cII genes is discussed.