Alternative titles; symbols
HGNC Approved Gene Symbol: POLR2I
Cytogenetic location: 19q13.12 Genomic coordinates (GRCh38) : 19:36,113,709-36,114,875 (from NCBI)
In eukaryotic cells, transcription of genes encoding mRNAs is effected by RNA polymerase II, in combination with a number of cofactors that control the selectivity and/or efficiency of transcription initiation, elongation, and termination. Depending on its origin, RNA polymerase II is found to consist of 10 to 14 polypeptides ranging from 220 to 10 kD. For general information on the structure and function of RNA polymerase II, see POLR2A (180660).
The cDNA of the largest subunit of human RNA polymerase II (POLR2A) codes for a polypeptide of average molecular mass 220 kD. The second largest subunit (POLR2B; 180661) has a molecular mass of about 140 kD. Acker et al. (1993) reported the genomic sequence for a human subunit homologous to RPB9 in yeast. The POLR2I gene is transcribed into 3 major RNA species. The corresponding mRNAs contain the same open reading frame encoding a 125-amino acid residue protein, with a calculated molecular mass of 14,523 daltons.
Acker et al. (1993) found that the POLR2I gene consists of 6 exons, ranging from 52 to over 110 bp.
Yeast cells lacking RPB9 are unable to grow at high and low temperatures and are defective in mRNA start site selection. McKune et al. (1995) found that expression of POLR2I on a high copy number plasmid, but not on a low copy number plasmid, restored growth at high temperatures. Recombinant POLR2I was also able to correct the start site selection defect seen at the CYC1 promoter in vitro as effectively as the yeast RPB9 subunit.
By in situ hybridization, Acker et al. (1994) assigned the POLR2I gene to chromosome 19q12.
Crystal Structure
Cramer et al. (2000) derived a backbone model of a 10-subunit yeast RNA polymerase II using x-ray diffraction data extending to 3-angstrom resolution. All 10 subunits exhibited a high degree of identity with the corresponding human proteins, and 9 of the 10 subunits are conserved among the 3 eukaryotic RNA polymerases I, II, and III. Notable features of the model include a pair of jaws, formed by subunits Rpb1 (180660), Rpb5 (180664), and Rpb9, that appears to grip DNA downstream of the active center. A clamp on the DNA nearer the active center, formed by Rpb1, Rpb2 (180661), and Rpb6 (604414), may be locked in the closed position by RNA, accounting for the great stability of transcribing complexes. A pore in the protein complex beneath the active center may allow entry of substrates for polymerization and exit of the transcript during proofreading and passage through pause sites in the DNA.
Acker, J., Mattei, M.-G., Wintzerith, M., Roeckel, N., Depetris, D., Vigneron, M., Kedinger, C. Chromosomal localization of human RNA polymerase II subunit genes. Genomics 20: 496-499, 1994. [PubMed: 8034326] [Full Text: https://doi.org/10.1006/geno.1994.1208]
Acker, J., Wintzerith, M., Vigeron, M., Kedinger, C. Structure of the gene encoding the 14.5 kDa subunit of human RNA polymerase II. Nucleic Acids Res. 21: 5345-5350, 1993. [PubMed: 8265347] [Full Text: https://doi.org/10.1093/nar/21.23.5345]
Cramer, P., Bushnell, D. A., Fu, J., Gnatt, A. L., Maier-Davis, B., Thompson, N. E., Burgess, R. R., Edwards, A. M., David, P. R., Kornberg, R. D. Architecture of RNA polymerase II and implications for the transcription mechanism. Science 288: 640-648, 2000. [PubMed: 10784442] [Full Text: https://doi.org/10.1126/science.288.5466.640]
McKune, K., Moore, P. A., Hull, M. W., Woychik, N. A. Six human RNA polymerase subunits functionally substitute for their yeast counterparts. Molec. Cell. Biol. 15: 6895-6900, 1995. [PubMed: 8524256] [Full Text: https://doi.org/10.1128/MCB.15.12.6895]