Phosphorylation of UBF at serine 388 is required for interaction with RNA polymerase I and activation of rDNA transcription.
Modulation of the activity of the upstream binding factor (UBF) plays a key role in cell cycle-dependent regulation of rRNA synthesis. Activation of rDNA transcription on serum stimulation requires phosphorylation of UBF at serine 484 by G(1)-specific cyclin-dependent kinase (cdk)/cyclin complexes. After G(1) progression UBF is phosphorylated at serine 388 by cdk2/cyclin E and cdk2/cyclin A. Conversion of serine 388 to glycine abolishes UBF activity, whereas substitution by aspartate enhances the transactivating function of UBF. Protein-protein interaction studies reveal that phosphorylation at serine 388 is required for the interaction between RNA polymerase I and UBF. The results suggest that phosphorylation of UBF represents a powerful means of modulating the assembly of the transcription initiation complex in a proliferation- and cell cycle-dependent fashion.
Voit
R
R
Division of Molecular Biology of the Cell II, German Cancer Research Center, D-69120 Heidelberg, Germany. R.Voit@DKFZ-Heidelberg.de
Grummt
I
I
D016475:3T3 Cells; D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation; D035463:Pol1 Transcription Initiation Complex Proteins; D012318:RNA Polymerase I / Q000378:metabolism*; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D018411:Spodoptera; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D035463:Pol1 Transcription Initiation Complex Proteins; D014157:Transcription Factors; C063844:transcription factor UBF; D012694:Serine; D012318:RNA Polymerase I