Genetic analysis of the cIII gene of bacteriophage HK022

The cIII gene product of lambdoid bacteriophages promotes lysogeny by stabilizing the phage-encoded CII protein, a transcriptional activator of the repressor and integrase genes. Previous works showed that the synthesis of the bacteriophage λ CIII protein has specific translational requirements imposed hy the structure of the mRNA. To gain insight into the mRNA structure and its role in regulating cIII translation, we undertook a mutational analysis of the cIII gene of the related bacteriophage HK022. Our data support the hypothesis that in HK022, as in λ, translation initiation requires a specific mRNA structure. In addition, we found that translation of HK022 cIII, like that of λ, is strongly reduced in a host deficient in the endonuclease RNase III.