E2F mediates cell cycle-dependent transcriptional repression in vivo by recruitment of an HDAC1/mSin3B corepressor complex.
Despite biochemical and genetic data suggesting that E2F and pRB (pocket protein) families regulate transcription via chromatin-modifying factors, the precise mechanisms underlying gene regulation by these protein families have not yet been defined in a physiological setting. In this study, we have investigated promoter occupancy in wild-type and pocket protein-deficient primary cells. We show that corepressor complexes consisting of histone deacetylase (HDAC1) and mSin3B were specifically recruited to endogenous E2F-regulated promoters in quiescent cells. These complexes dissociated from promoters once cells reached late G1, coincident with gene activation. Interestingly, recruitment of HDAC1 complexes to promoters depended absolutely on p107 and p130, and required an intact E2F-binding site. In contrast, mSin3B recruitment to certain promoters did not require p107 or p130, suggesting that recruitment of this corepressor can occur via E2F-dependent and -independent mechanisms. Remarkably, loss of pRB had no effect on HDAC1 or mSin3B recruitment. p107/p130 deficiency triggered a dramatic loss of E2F4 nuclear localization as well as transcriptional derepression, which is suggested by nucleosome mapping studies to be the result of localized hyperacetylation of nucleosomes proximal to E2F-binding sites. Taken together, these findings show that p130 escorts E2F4 into the nucleus and, together with corepressor complexes that contain mSin3B and/or HDAC1, directly represses transcription from target genes as cells withdraw from the cell cycle.
Rayman
Joseph B
JB
Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Takahashi
Yasuhiko
Y
Indjeian
Vahan B
VB
Dannenberg
Jan-Hermen
JH
Catchpole
Steven
S
Watson
Roger J
RJ
te Riele
Hein
H
Dynlacht
Brian David
BD
D016475:3T3 Cells; D000107:Acetylation; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050704:E2F4 Transcription Factor; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D020868:Gene Silencing / Q000502:physiology*; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases / Q000378:metabolism*; D046911:Macromolecular Substances; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D009707:Nucleosomes / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology; D011485:Protein Binding / Q000502:physiology; D011506:Proteins; D012097:Repressor Proteins / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D014157:Transcription Factors / Q000378:metabolism*
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050704:E2F4 Transcription Factor; C493763:E2f4 protein, mouse; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D009707:Nucleosomes; D010750:Phosphoproteins; D011506:Proteins; C489485:Rbl1 protein, mouse; C493838:Rbl2 protein, mouse; D012097:Repressor Proteins; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; C492042:SIN3B protein, human; C115812:Sin3b protein, mouse; D014157:Transcription Factors; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases