InterPro domain: IPR033898

The eukaryotic AC19 subunit (also known as RPAC2 in mammals and RPC19 in yeast) of RNA polymerase (RNAP) I and RNAP III is involved in the assembly of RNAP subunits [ 1 ]. RNAP is a large multi-subunit complex responsible for the synthesis of RNA. It is the principal enzyme of the transcription process, and is a final target in many regulatory pathways that control gene expression in all living cells. At least three distinct RNAP complexes are found in eukaryotic nuclei: RNAP I, RNAP II, and RNAP III. RNAP I is responsible for the synthesis of ribosomal RNA precursor, while RNAP III functions in the synthesis of 5S and tRNA [ 2 ]. The AC19 subunit is the equivalent of the RPB11 subunit of RNAP II [ 3 ]. The RPB11 subunit heterodimerizes with the RPB3 subunit, and together with RPB10 and RPB12, anchors the two largest subunits, RPB1 and RPB2, and stabilizes their association. The homology of AC19 to RPB11 suggests a similar function. The AC19 subunit is likely to associate with the RPB3 counterpart, AC40, to form a heterodimer, which stabilizes the association of the two largest subunits of RNAP I and RNAP III [ 4 , 4 , 5 ].

1. Conservation between the RNA polymerase I, II, and III transcription initiation machineries. Mol. Cell 45, 439-46
2. Survey and summary: transcription by RNA polymerases I and III. Nucleic Acids Res. 28, 1283-98
3. RNA polymerase I structure and transcription regulation. Nature 502, 650-5
4. Mouse RNA polymerase I 16-kDa subunit able to associate with 40-kDa subunit is a homolog of yeast AC19 subunit of RNA polymerases I and III. J. Biol. Chem. 271, 32881-5
5. Rpc19 and Rpc40, two alpha-like subunits shared by nuclear RNA polymerases I and III, are interchangeable between the fission and budding yeasts. Curr. Genet. 36, 208-14