In vitro transcription from the late promoter of bacteriophage P4

The late genes of satellite bacteriophage P4 are cotranscribed from a single promoter which shares little homology with known classes of Escherichia coli promoters (E. Dale, G. Christie, and R. Calendar, J. Mol. Biol. 192:793-803, 1986). In a coupled transcription-translation system, the P4 late gene promoter was activated by either the delta protein of P4 or the ogr protein of helper phage P2 in the absence of any other phage-encoded factor. delta-dependent transcription was inhibited by antibodies to the sigma 70 subunit of E. coli RNA polymerase but was restored by purified sigma 70, indicating that activation of transcription by the delta protein of P4 is dependent on the sigma 70 holoenzyme.