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Curr Biol. 2002 Dec 23;12(24):2142-6.

The cell cycle regulatory factor TAF1 stimulates ribosomal DNA transcription by binding to the activator UBF.

Author information

1
Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.

Abstract

Control of ribosome biogenesis is a potential mechanism for the regulation of cell size during growth, and a key step in regulating ribosome production is ribosomal RNA synthesis by RNA polymerase I (Pol I). In humans, Pol I transcription requires the upstream binding factor UBF and the selectivity factor SL1 to assemble coordinately on the promoter. UBF is an HMG box-containing factor that binds to the rDNA promoter and activates Pol I transcription through its acidic carboxy-terminal tail. Using UBF (284-670) as bait in a yeast two-hybrid screen, we have identified an interaction between UBF and TAF1, a factor involved in the transcription of cell cycle and growth regulatory genes. Coimmunoprecipitation and protein-protein interaction assays confirmed that TAF1 binds to UBF. Confocal microscopy showed that TAF1 colocalizes with UBF in Hela cells, and cell fractionation experiments provided further evidence that a portion of TAF1 is localized in the nucleolus, the organelle devoted to ribosomal DNA transcription. Cotransfection and in vitro transcription assays showed that TAF1 stimulates Pol I transcription in a dosage-dependent manner. Thus, TAF1 may be involved in the coordinate expression of Pol I- and Pol II-transcribed genes required for protein biosynthesis and cell cycle progression.

PMID:
12498690
[Indexed for MEDLINE]
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