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Molecular basis of Rrn3-regulated RNA polymerase I initiation and cell growth.

Genes & development | Oct 1, 2011

http://www.ncbi.nlm.nih.gov/pubmed/21940764

Cell growth is regulated during RNA polymerase (Pol) I transcription initiation by the conserved factor Rrn3/TIF-IA in yeast/humans. Here we provide a structure-function analysis of Rrn3 based on a combination of structural biology with in vivo and in vitro functional assays. The Rrn3 crystal structure reveals a unique HEAT repeat fold and a surface serine patch. Phosphorylation of this patch represses human Pol I transcription, and a phospho-mimetic patch mutation prevents Rrn3 binding to Pol I in vitro and reduces cell growth and Pol I gene occupancy in vivo. Cross-linking indicates that Rrn3 binds Pol I between its subcomplexes, AC40/19 and A14/43, which faces the serine patch. The corresponding region of Pol II binds the Mediator head that cooperates with transcription factor (TF) IIB. Consistent with this, the Rrn3-binding factor Rrn7 is predicted to be a TFIIB homolog. This reveals the molecular basis of Rrn3-regulated Pol I initiation and cell growth, and indicates a general architecture of eukaryotic transcription initiation complexes.

Pubmed ID: 21940764 RIS Download

Mesh terms: Amino Acid Sequence | Cell Proliferation | DNA Polymerase I | Humans | Models, Molecular | Molecular Sequence Data | Mutation | Pol1 Transcription Initiation Complex Proteins | Promoter Regions, Genetic | Protein Binding | Protein Multimerization | Protein Structure, Tertiary | Saccharomyces cerevisiae | Saccharomyces cerevisiae Proteins | Sequence Alignment | Serine

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