DNA-dependent RNA polymerase, which is injected into the host upon infection and transcribes the phage early genes from promoters that have a 5-bp stem-3 nt loop hairpin structure. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Present in about 4 copies in the virion. Contains three functional domains; the central domain possesses the transcriptional activity. Belongs to the phage and mitochondrial RNA polymerase family.