DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Common component of RNA polymerases I and III which synthesize ribosomal RNA precursors and short non-coding RNAs including 5S rRNA, snRNAs, tRNAs and miRNAs, respectively. POLR1C/RPAC1 is part of the polymerase core and may function as a clamp element that moves to open and close the cleft.