By sequencing cDNAs obtained from umbilical cord blood CD34-positive hematopoietic stem/progenitor cells, Mao et al. (1998) cloned POLR1C, which they called RPA40. The deduced protein contains 342 amino acids.

By sequencing proteins contained within RNA polymerase III complexes purified from HeLa cells, followed by database analysis, Hu et al. (2002) identified POLR1C, which they called RPAC1. The deduced 342-amino acid protein has a calculated molecular mass of 38.6 kD and shares 47% amino acid identity with its yeast homolog, AC40.The International Radiation Hybrid Mapping Consortium mapped the POLR1C gene to chromosome 6.