RBP-Jkappa/SHARP recruits CtIP/CtBP corepressors to silence Notch target genes.
Notch is a transmembrane receptor that determines cell fates and pattern formation in all animal species. After ligand binding, proteolytic cleavage steps occur and the intracellular part of Notch translocates to the nucleus, where it targets the DNA-binding protein RBP-Jkappa/CBF1. In the absence of Notch, RBP-Jkappa represses Notch target genes through the recruitment of a corepressor complex. We and others have identified SHARP as a component of this complex. Here, we functionally demonstrate that the SHARP repression domain is necessary and sufficient to repress transcription and that the absence of this domain causes a dominant negative Notch-like phenotype. We identify the CtIP and CtBP corepressors as novel components of the human RBP-Jkappa/SHARP-corepressor complex and show that CtIP binds directly to the SHARP repression domain. Functionally, CtIP and CtBP augment SHARP-mediated repression. Transcriptional repression of the Notch target gene Hey1 is abolished in CtBP-deficient cells or after the functional knockout of CtBP. Furthermore, the endogenous Hey1 promoter is derepressed in CtBP-deficient cells. We propose that a corepressor complex containing CtIP/CtBP facilitates RBP-Jkappa/SHARP-mediated repression of Notch target genes.
Oswald
Franz
F
Department of Internal Medicine I, University of Ulm, Robert-Koch-Strasse 8, D-89081 Ulm, Germany. franz.oswald@uni-ulm.de
Winkler
Michael
M
Cao
Ying
Y
Astrahantseff
Kathy
K
Bourteele
Soizic
S
Knöchel
Walter
W
Borggrefe
Tilman
T
D000429:Alcohol Oxidoreductases; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism; D004706:Endodeoxyribonucleases; D020868:Gene Silencing; D006801:Humans; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics / Q000378:metabolism
D000429:Alcohol Oxidoreductases; D051792:Basic Helix-Loop-Helix Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D004706:Endodeoxyribonucleases; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D010750:Phosphoproteins; D051880:Receptors, Notch; D012097:Repressor Proteins; C422085:BHLHE41 protein, human; C497570:RBPJ protein, human; C096794:C-terminal binding protein; C410741:RBBP8 protein, human