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 2 Zn(2+) ions per subunit. The RNAP catalytic core consists of 2 alpha, 1 beta/beta' and 1 omega subunit. When a sigma factor is associated with the core the holoenzyme is formed, which can initiate transcription. Fusion of rpoB and rpoC occurs naturally in Helicobacter species and at least some Wolbachia; the protein has been artificially split in two in H.pylori. The split protein seems to function normally. In the N-terminal section; belongs to the RNA polymerase beta chain family. In the C-terminal section; belongs to the RNA polymerase beta' chain family.