DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Common core component of RNA polymerases I and III which synthesize ribosomal RNA precursors and small RNAs, such as 5S rRNA and tRNAs, respectively. 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. Belongs to the archaeal Rpo11/eukaryotic RPB11/RPC19 RNA polymerase subunit family. Contrary to isoform 2, isoform 1 contains an RNA polymerase domain and has DNA-dependent RNA polymerase function. Synteny studies in vertebrates suggest that this isoform has been created by a mammalian-specific retrotransposition event of an ancestral gene which has been lost later on in this lineage.