FACT facilitates chromatin transcription by RNA polymerases I and III.
Efficient transcription elongation from a chromatin template requires RNA polymerases (Pols) to negotiate nucleosomes. Our biochemical analyses demonstrate that RNA Pol I can transcribe through nucleosome templates and that this requires structural rearrangement of the nucleosomal core particle. The subunits of the histone chaperone FACT (facilitates chromatin transcription), SSRP1 and Spt16, co-purify and co-immunoprecipitate with mammalian Pol I complexes. In cells, SSRP1 is detectable at the rRNA gene repeats. Crucially, siRNA-mediated repression of FACT subunit expression in cells results in a significant reduction in 47S pre-rRNA levels, whereas synthesis of the first 40 nt of the rRNA is not affected, implying that FACT is important for Pol I transcription elongation through chromatin. FACT also associates with RNA Pol III complexes, is present at the chromatin of genes transcribed by Pol III and facilitates their transcription in cells. Our findings indicate that, beyond the established role in Pol II transcription, FACT has physiological functions in chromatin transcription by all three nuclear RNA Pols. Our data also imply that local chromatin dynamics influence transcription of the active rRNA genes by Pol I and of Pol III-transcribed genes.
Birch
Joanna L
JL
Wellcome Trust Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee, UK.
Tan
Bertrand C-M
BC
Panov
Kostya I
KI
Panova
Tatiana B
TB
Andersen
Jens S
JS
Owen-Hughes
Tom A
TA
Russell
Jackie
J
Lee
Sheng-Chung
SC
Zomerdijk
Joost C B M
JC
D002843:Chromatin / Q000235:genetics* / Q000378:metabolism; D004275:DNA, Ribosomal / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020459:Genes, rRNA; D006367:HeLa Cells; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D009707:Nucleosomes / Q000378:metabolism; D012318:RNA Polymerase I / Q000378:metabolism*; D012320:RNA Polymerase III / Q000378:metabolism*; D014158:Transcription, Genetic; D035602:Transcriptional Elongation Factors / Q000235:genetics / Q000378:metabolism*
D002843:Chromatin; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D006657:Histones; D009707:Nucleosomes; C073537:SSRP1 protein, human; D035602:Transcriptional Elongation Factors; D012318:RNA Polymerase I; D012320:RNA Polymerase III