hRRN3 is essential in the SL1-mediated recruitment of RNA Polymerase I to rRNA gene promoters.
A crucial step in transcription is the recruitment of RNA polymerase to promoters. In the transcription of human rRNA genes by RNA Polymerase I (Pol I), transcription factor SL1 has a role as the essential core promoter binding factor. Little is known about the mechanism by which Pol I is ... recruited. We provide evidence for an essential role for hRRN3, the human homologue of a yeast Pol I transcription factor, in this process. We find that whereas the bulk of human Pol I complexes (I alpha) are transcriptionally inactive, hRRN3 defines a distinct subpopulation of Pol I complexes (I beta) that supports specific initiation of transcription. Human RRN3 interacts directly with TAF(I)110 and TAF(I)63 of promoter-selectivity factor SL1. Blocking this connection prevents recruitment of Pol I beta to the rDNA promoter. Furthermore, hRRN3 can be found in transcriptionally autonomous Pol I holoenzyme complexes. We conclude that hRRN3 functions to recruit initiation-competent Pol I to rRNA gene promoters. The essential role for hRRN3 in linking Pol I to SL1 suggests a mechanism for growth control of Pol I transcription.
Mesh Terms:
Binding Sites, Cell Nucleolus, DNA-Binding Proteins, Gene Expression Regulation, Holoenzymes, Humans, Models, Genetic, Pol1 Transcription Initiation Complex Proteins, Promoter Regions, Genetic, Protein Binding, RNA Polymerase I, RNA, Ribosomal, Transcription Factors, Transcription, Genetic
Binding Sites, Cell Nucleolus, DNA-Binding Proteins, Gene Expression Regulation, Holoenzymes, Humans, Models, Genetic, Pol1 Transcription Initiation Complex Proteins, Promoter Regions, Genetic, Protein Binding, RNA Polymerase I, RNA, Ribosomal, Transcription Factors, Transcription, Genetic
EMBO J.
Date: Mar. 15, 2001
PubMed ID: 11250903
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