Numbers of engaged RNA Polymerase complexes

Range pol I ~30,000: pol II ~60,000: pol III 3,000 complexes/cell
Organism Mouse Mus musculus
Reference Jackson DA, Pombo A, Iborra F. The balance sheet for transcription: an analysis of nuclear RNA metabolism in mammalian cells. FASEB J. 2000 Feb14(2):242-54. p.243 right column top paragraphPubMed ID10657981
Method "Kinetic analyses of the entry of [3H]adenosine into ATP and RNA establish levels of RNA synthesis within intact cells."
Comments "Mouse L cells, which divide every 12–14 h, support a continuous synthetic rate of ~2×10^8 nucleotides/min with 39, 58, and 3% into prerRNA, pre-mRNA (hnRNA), and 4–5S RNA, respectively (Brandhorst et al., 1974 PMID 22003578). With synthetic rates of 2.5 and 2 kbp/min for pol I and pol II/III, respectively (see above), and average transcript lengths of 13, 10, and 0.1 kb for pol I, pol II, and pol III, respectively, these values correspond to ~30,000, 60,000, and 3,000 engaged pol I, II, and III complexes/cell, respectively. In rabbit erythroid cells, levels of RNA synthesis are at least 10-fold lower (Hunt 1976 PMID 1016252), though similar proportions of pol I and II activity are seen."
Entered by Uri M
ID 111161