DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Component of RNA polymerase I which synthesizes ribosomal RNA precursors. Required for growth at higher temperatures. Component of the RNA polymerase I (Pol I) complex consisting of at least 13 subunits. The N-terminal zinc-finger domain but not the C-terminal one is required for rpa12 function. Belongs to the archaeal RpoM/eukaryotic RPA12/RPB9/RPC11 RNA polymerase family.