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.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Cell Cycle / physiology
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Cell-Free System
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Cells, Cultured
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Chromosomal Proteins, Non-Histone / genetics
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Chromosomal Proteins, Non-Histone / metabolism*
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DNA, Ribosomal / genetics*
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DNA, Ribosomal / metabolism
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DNA-Binding Proteins
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HeLa Cells
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Histone Acetyltransferases
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Histone Chaperones
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Humans
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Mutation
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Pol1 Transcription Initiation Complex Proteins / genetics
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Pol1 Transcription Initiation Complex Proteins / metabolism*
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RNA Polymerase I / genetics
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RNA Polymerase I / metabolism
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RNA Polymerase II / metabolism
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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TATA-Binding Protein Associated Factors / genetics
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TATA-Binding Protein Associated Factors / metabolism
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Transcription Factor TFIID / genetics
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Transcription Factor TFIID / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Transcription, Genetic / physiology
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Transfection
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Two-Hybrid System Techniques
Substances
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Chromosomal Proteins, Non-Histone
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DNA, Ribosomal
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DNA-Binding Proteins
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Histone Chaperones
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Pol1 Transcription Initiation Complex Proteins
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Recombinant Proteins
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SET protein, human
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TATA-Binding Protein Associated Factors
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Transcription Factor TFIID
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Transcription Factors
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transcription factor UBF
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Histone Acetyltransferases
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TATA-binding protein associated factor 250 kDa
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RNA Polymerase II
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RNA Polymerase I