DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Rpo30 may have a role in RNA chain elongation. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) This enzyme consists of at least eight subunits. Belongs to the poxviridae DNA-directed RNA polymerase 30 kDa subunit family.