POLR3A (polymerase (RNA) III (DNA directed) polypeptide A), also known as RPC1 or RPC155, is a 1,390 amino acid protein that localizes to the nucleus and belongs to the RNA polymerase beta chain family. Existing as the largest and catalytic core component of Pol III, POLR3A functions as a DNA-dependent RNA polymerase that catalyzes the conversion of a nucleoside triphosphate into a diphosphate, thereby transcribing DNA into RNA. The gene encoding POLR3A maps to human chromosome 10, which houses over 1,200 genes and comprises nearly 4.5% of the human genome.