Plays a role in the transcription of the viral late genes by acting as a late promoter recognition subunit (PubMed:33602900). Associates with host RNA polymerase (RNAP) core and thus replaces the host sigma-70/rpoD subunit in the complex (PubMed:33602900). May also play a role in DNA packaging by interacting with the terminase subunit gp17 (PubMed:12051907). Interacts with the host RNA polymerase catalytic core formed by RpoA, RpoB, RpoC and RpoZ to form the RNAP-gp55 holoenzyme (PubMed:3305506, PubMed:12496274, PubMed:33602900). Part of the transcription activation complex containing host RNAP, the viral RNA polymerase sigma-like factor, the late transcription coactivator, and the sliding clamp (PubMed:33602900). Interacts with the terminase large subunit; this interaction may load the terminase onto DNA for packaging (PubMed:12051907). Belongs to the Tevenvirinae RNA polymerase sigma-like factor family.