Virion-associated RNA polymerase required for bacteriophage N4 development.

Escherichia coli phage N4 transcription is resistant to rifampicin, an inhibitor of the host RNA polymerase, even when the drug is added prior to infection. A rifampicin-resistant RNA polymerase has been detected in disrupted N4 virions. This enzyme shows a requirement for the four ribonucleoside 5'-triphosphates and exogenous denatured DNA. With denatured N4 DNA, the preferred template, transcription is asymmetric. The virion RNA polymerase apparently is necessary for phage development because a conditional lethal N4 mutant shows temperature-sensitive RNA synthesis in vivo as well as a temperature-sensitive RNA polymerase in disrupted virions.