DNA-dependent RNA polymerase (RNAP) catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Part of the RNA polymerase complex. Belongs to the archaeal Rpo5/eukaryotic RPB5 RNA polymerase subunit family. Extended N-terminus.