DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Binds 1 Mg(2+) ion per subunit. Binds 1 Zn(2+) ion per subunit. Belongs to the RNA polymerase beta' chain family. RpoC1 subfamily.