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 small RNAs, such as 5S rRNA and tRNAs, respectively. RPAC1 is part of the Pol core element with the central large cleft and probably a clamp element that moves to open and close the cleft (By similarity). Component of the RNA polymerase I (Pol I) and RNA polymerase III (Pol III) complexes consisting of at least 13 and 17 subunits, respectively. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the archaeal Rpo3/eukaryotic RPB3 RNA polymerase subunit family.