Mediation of CTCF transcriptional insulation by DEAD-box RNA-binding protein p68 and steroid receptor RNA activator SRA.
CCCTC-binding factor (CTCF) is a DNA-binding protein that plays important roles in chromatin organization, although the mechanism by which CTCF carries out these functions is not fully understood. Recent studies show that CTCF recruits the cohesin complex to insulator sites and that cohesin is required for insulator activity. Here we showed that the DEAD-box RNA helicase p68 (DDX5) and its associated noncoding RNA, steroid receptor RNA activator (SRA), form a complex with CTCF that is essential for insulator function. p68 was detected at CTCF sites in the IGF2/H19 imprinted control region (ICR) as well as other genomic CTCF sites. In vivo depletion of SRA or p68 reduced CTCF-mediated insulator activity at the IGF2/H19 ICR, increased levels of IGF2 expression, and increased interactions between the endodermal enhancer and IGF2 promoter. p68/SRA also interacts with members of the cohesin complex. Depletion of either p68 or SRA does not affect CTCF binding to its genomic sites, but does reduce cohesin binding. The results suggest that p68/SRA stabilizes the interaction of cohesin with CTCF by binding to both, and is required for proper insulator function.
Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Hongjie
H
Yao
Kevin
K
Brick
Yvonne
Y
Evrard
Tiaojiang
T
Xiao
R Daniel
RD
Camerini-Otero
Gary
G
Felsenfeld
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000483:Alleles; D000818:Animals; D000076246:CCCTC-Binding Factor; D018797:Cell Cycle Proteins / Q000378:metabolism; D002478:Cells, Cultured; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D002874:Chromosome Mapping; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D055106:Genome-Wide Association Study; D006367:HeLa Cells; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D041681:NIH 3T3 Cells; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D000097722:Cohesins
D048868:Adaptor Proteins, Signal Transducing; D000076246:CCCTC-Binding Factor; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D053487:DEAD-box RNA Helicases; D007335:Insulin-Like Growth Factor II; D012313:RNA; D012097:Repressor Proteins; D000097722:Cohesins; C000619697:CTCF protein, human; C109916:CYFIP1 protein, human; C000619698:Ctcf protein, mouse; C115472:Cyfip1 protein, mouse