Effect of mutations in the cII and cIII genes of bacteriophage λ on macromolecular synthesis in infected cells

We have investigated the time-course of macromolecular synthesis following infection by cI^-, cII^- and cIII^- mutants of λ in an effort to understand the role of the cII and cIII genes in the establishment of repression and lysogeny. cII^- and cIII^- mutants of λ begin to synthesize the "late" proteins tail antigen and lysozyme substantially before a cI^- mutant; the shift to late messenger RNA production from the head and tail genes also occurs earlier after cII^- or cIII^- infection. In contrast, no appreciable difference among cI^-, cII^-, or cIII^- mutants was found in synthesis of the "early" protein λ-exonuclease or in the rate of total or λ-specific DNA synthesis. These results suggest that the λ cII and cIII gene products function to delay the lytic response by inhibiting, directly or indirectly, the production of messenger RNA from the late λ genes. When lysozyme synthesis was studied after infection by cI^- cII^- and cI^- cIII^- double mutants, results were obtained which were similar to those found in the case of single cII^- and cIII^- mutants. The results with the double mutants suggest that the cII and cIII gene products may also participate in the regulation of cI represser synthesis or activity.