Multiple interactions between RNA polymerase I, TIF-IA and TAF(I) subunits regulate preinitiation complex assembly at the ribosomal gene promoter.
In mammals, growth-dependent regulation of rRNA synthesis is brought about by the transcription initiation factor TIF-IA. TIF-IA is associated with a fraction of the TBP-containing factor TIF-IB/SL1 and the initiation-competent form of RNA polymerase I (Pol I). We investigated the mechanisms that down-regulate cellular pre-rRNA synthesis and demonstrate that nutrient starvation, density arrest and protein synthesis inhibitors inactivate TIF-IA and impair the association of TIF-IA with Pol I. Moreover, we used a panel of TIF-IA deletion mutants to map the domains that mediate the interaction of TIF-IA with Pol I and TIF-IB/SL1. We found that amino acids 512-609 interact with two subunits of Pol I, RPA43 and PAF67, whereas a short, conserved motif (LARAK, amino acids 411-415) is required for the association of TIF-IA with TAF(I)95 and TAF(I)68. The results uncover an interphase for essential protein-protein interactions that facilitate Pol I preinitiation complex formation.
Yuan
Xuejun
X
Division of Molecular Biology of the Cell II, German Cancer Research Center, D-69120 Heidelberg, Germany.
Zhao
Jian
J
Zentgraf
Hanswalter
H
Hoffmann-Rohrer
Urs
U
Grummt
Ingrid
I
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D017930:Genes, Reporter; D020459:Genes, rRNA; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D035463:Pol1 Transcription Initiation Complex Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D021122:Protein Subunits / Q000378:metabolism; D012318:RNA Polymerase I / Q000235:genetics / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D035463:Pol1 Transcription Initiation Complex Proteins; D021122:Protein Subunits; D012335:RNA, Ribosomal; C428423:RRN3 protein, human; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D012318:RNA Polymerase I