Phosphorylation by casein kinase 2 facilitates rRNA gene transcription by promoting dissociation of TIF-IA from elongating RNA polymerase I.
The protein kinase casein kinase 2 (CK2) phosphorylates different components of the RNA polymerase I (Pol I) transcription machinery and exerts a positive effect on rRNA gene (rDNA) transcription. Here we show that CK2 phosphorylates the transcription initiation factor TIF-IA at serines 170 and 172 (Ser170/172), and this phosphorylation triggers the release of TIF-IA from Pol I after transcription initiation. Inhibition of Ser170/172 phosphorylation or covalent tethering of TIF-IA to the RPA43 subunit of Pol I inhibits rDNA transcription, leading to perturbation of nucleolar structure and cell cycle arrest. Fluorescence recovery after photobleaching and chromatin immunoprecipitation experiments demonstrate that dissociation of TIF-IA from Pol I is a prerequisite for proper transcription elongation. In support of phosphorylation of TIF-IA switching from the initiation into the elongation phase, dephosphorylation of Ser170/172 by FCP1 facilitates the reassociation of TIF-IA with Pol I, allowing a new round of rDNA transcription. The results reveal a mechanism by which the functional interplay between CK2 and FCP1 sustains multiple rounds of Pol I transcription.
Molecular Biology of Cell II, German Cancer Research Center, DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany.
Holger
H
Bierhoff
Miroslav
M
Dundr
Annemieke A
AA
Michels
Ingrid
I
Grummt
D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II / Q000378:metabolism*; D002453:Cell Cycle; D002466:Cell Nucleolus / Q000378:metabolism; D049109:Cell Proliferation; D004275:DNA, Ribosomal / Q000235:genetics; D006801:Humans; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D035463:Pol1 Transcription Initiation Complex Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012318:RNA Polymerase I / Q000378:metabolism*; D012322:RNA Precursors / Q000096:biosynthesis; D012335:RNA, Ribosomal / Q000235:genetics*; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic
D004275:DNA, Ribosomal; D035463:Pol1 Transcription Initiation Complex Proteins; D012322:RNA Precursors; D012335:RNA, Ribosomal; C428423:RRN3 protein, human; D014157:Transcription Factors; D010768:Phosphoserine; D047390:Casein Kinase II; D012318:RNA Polymerase I; D010749:Phosphoprotein Phosphatases; C116022:carboxy-terminal domain phosphatase