On the effect of bacteriophage infection on host RNA polymerase

The infection of E. coli with T-even bacteriophages results in modification of α-polypeptide of the host RNA polymerase which can be revealed by its changed electrophoretic mobility after treatment with 6 M urea. The infection with bacteriophages T3 and T7 does not lead to such a change of the bacterial core enzyme. The core enzyme from T7-infected cells is shown to compete efficiently with host RNA polymerase for a DNA template while the core from T2-infected bacteria fails to do so. These differences in the fate of bacterial RNA polymerase after infection with the two groups of T-phages can be explained by the fact that in T3- and T7-infection new phage-induced RNA polamerases carry out the transcription of late genes while in T-even infection all transcription, is performed by the host enzyme. After T7 infections the bacterial RNA polymerase loses its sigma factor. This process requires protein synthesis.