Pocket protein complexes are recruited to distinct targets in quiescent and proliferating cells.
Biochemical and genetic studies have determined that retinoblastoma protein (pRB) tumor suppressor family members have overlapping functions. However, these studies have largely failed to distinguish functional differences between the highly related p107 and p130 proteins. Moreover, most studies pertaining to the pRB family and its principal target, the E2F transcription factor, have focused on cells that have reinitiated a cell cycle from quiescence, although recent studies suggest that cycling cells exhibit layers of regulation distinct from mitogenically stimulated cells. Using genome-wide chromatin immunoprecipitation, we show that there are distinct classes of genes directly regulated by unique combinations of E2F4, p107, and p130, including a group of genes specifically regulated in cycling cells. These groups exhibit both distinct histone acetylation signatures and patterns of mammalian Sin3B corepressor recruitment. Our findings suggest that cell cycle-dependent repression results from recruitment of an unexpected array of diverse complexes and reveals specific differences between transcriptional regulation in cycling and quiescent cells. In addition, factor location analyses have, for the first time, allowed the identification of novel and specific targets of the highly related transcriptional regulators p107 and p130, suggesting new and distinct regulatory networks engaged by each protein in continuously cycling cells.
Balciunaite
Egle
E
Department of Pathology, MSB 504, New York University School of Medicine and New York University Cancer Institute, 550 First Avenue, New York, NY 10016, USA.
Spektor
Alexander
A
Lents
Nathan H
NH
Cam
Hugh
H
Te Riele
Hein
H
Scime
Anthony
A
Rudnicki
Michael A
MA
Young
Richard
R
Dynlacht
Brian David
BD
D000107:Acetylation; D002453:Cell Cycle / Q000235:genetics*; D049109:Cell Proliferation; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D050704:E2F4 Transcription Factor; D016193:G1 Phase / Q000235:genetics; D005786:Gene Expression Regulation; D015894:Genome, Human; D006657:Histones / Q000378:metabolism; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D050704:E2F4 Transcription Factor; D006657:Histones; D009687:Nuclear Proteins; D011506:Proteins; C493844:RBL1 protein, human; C493837:RBL2 protein, human; D012097:Repressor Proteins; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; C492042:SIN3B protein, human; D014157:Transcription Factors