RNA polymerase I transcription

Although the higher level of nucleolin in tumours and actively dividing cells suggests that nucleolin could play a positive role in the production of ribosomal RNA, most of the studies rather show a repressive effect of nucleolin on RNA polymerase I transcription. 

On the other side, it has been demonstrated that nucleolin phosphorylation and rRNA transcription go hand in hand. Nucleolin phosphorylation could be triggered by a variety of stimuli like androgens and growth factors (Bonnet et al, 1996 Bouche et al, 1987 Issinger et al, 1988 Suzuki et al, 1985, 1991 Tawfic et al, 1994) and the phosphorylation is invariably accompanied by increased rRNA transcription and cell proliferation. All these observations suggest that indeed nucleolin could have regulatory role in RNA polymerase I transcription. However, further experiments are clearly required to clarify the function of nucleolin in rRNA transcription. 

Roussel, P., Andre, C., Masson, C., Geraud, G., and Hemandez-Verdun, D. (1993) Localization of the RNA polymerase I transcription factor hUBF during the cell cycle. J. Cell. Sci. 104(Pt 2), 327-337. 

NoRC Snf2h Mouse TIP5 Interacts with RNA polymerase I transcription termination factor I (TTF-1), localized to nucleoli [292] and implicated in repression of ribosomal gene transcription [293]. 

Comai, L., N. Tanese, and R. Tjian, The TATA-binding protein and associated factors are integral components of the RNA polymerase I transcription factor, SL1. Cell 68 965-976, 1992. 

RNA polymerase I transcription results in a single precursor (45S in mammals) that encodes three RNA components of the ribosome the 18S rRNA, the 28S rRNA, and the 5.8S rRNA (Figure 29.23). The 18S rRNA is the RNA component of the small ribosomal subunit (40S), and the 28S and 5.8S rRNAs are two RNA components of the large ribosomal subunit (60S). The other RNA component of the large ribosomal subunit, the 5S rRNA, is transcribed by RNA polymerase 111 as a separate transcript. 

Rudloff U., Eberhard D., Tora L., Stunnenberg H., Grummt I. (1994) TBP-associated factors interact with DNA and govern species specificity of RNA polymerase I transcription. EMBO J 13 2611. 

See also RNA Polymerase I Transcription, RNA Polymerase III Transcription, RNA Polymerase II Transcription, Chromatin Structure and Transcription, Eukaryotic Transcription. Termination of Eukaryotic Transcription, Chromatin Remodeling, Transcription Factor Binding Domains... 

RNA Polymerase I Transcription of the Major Ribosomal RNA Genes (Figure 28.20)... 

Zhou, Y., Santoro, R., and Grummt, I. (2002). The chromatin remodeling complex NoRC targets HDAC1 to the ribosomal gene promoter and represses RNA polymerase I transcription. EMBO J. 21(17), 4632-4640. 

Rodrigo, R. M., Rendon, M. C., Torreblanca, J., Garcia-Herdugo, G., and Moreno, F. J. (1992). Characterization and immunolocalization of RNA polymerase I transcription factor UBF with anti-NOR serum in protozoa, higher plant and vertebrate cells. J. Cell Sci. 103, 1053-1063. 

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