Catalytic component of the DNA-directed RNA polymerase (RNAP) that catalyzes the transcription in the cytoplasm of viral DNA into RNA using the four ribonucleoside triphosphates as substrates (By similarity). Forms the polymerase active center together with RPB2 (By similarity). Part of the core element with the central large cleft, the clamp element that moves to open and close the cleft and the jaws that are thought to grab the incoming DNA template (By similarity). a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Part of the viral DNA-directed RNA polymerase that consists of 8 polII-like subunits (RPB1, RPB2, RPB3, RPB5, RPB6, RPB7, RPB9, RPB10), a capping enzyme and a termination factor. Found in association with viral nucleoid. Expressed in the late phase of the viral replicative cycle. Lacks the typical C-terminal domain (CTD). Belongs to the RNA polymerase beta' chain family.