DNA-dependent RNA polymerases catalyze the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Component of RNA polymerase I (Pol I) which synthesizes ribosomal RNA precursors. Besides, RNA polymerase I has intrinsic RNA cleavage activity. Proposed to contribute to the polymerase catalytic activity and form the polymerase active center together with the two largest subunits. Subunit RPA12 contributes a catalytic zinc ribbon that is required for RNA cleavage by Pol I. Involved in transcriptional termination. Component of the RNA polymerase I (Pol I) complex consisting of 14 subunits: RPA135, RPA190, RPC40, RPA14, RPB5, RPO26, RPA43, RPB8, RPA12, RPB10, RPC19, RPC10, RPA49 and RPA34. The complex is composed of a horseshoe-shaped core containing ten subunits (RPA135, RPA190, RPB5, RPO26, RPB8, RPB10, RPC10, RPA12, RPC19 and RPC40) where RPA135 and RPA190 form the DNA-binding cleft. Outside of the core, RPA14 and RPA43 form the stalk that mediates interactions with transcription initiation factors and newly synthesized RNA. Interacts with RPA2/RPA135. Peripheral subunit that binds the catalytic zinc ion that is required for RNA cleavage. The heterodimer formed by RPA34 and RPA49 stabilizes subunit RPA12 and stimulates RPA12-dependent RNA cleavage. Involved in the recruitment of RPA49 to Pol I. Present with 8450 molecules/cell in log phase SD medium. Belongs to the archaeal RpoM/eukaryotic RPA12/RPB9/RPC11 RNA polymerase family.