title: Preferential association of irreversibly silenced E2F-target genes with pericentromeric heterochromatin in differentiated muscle cells.
abstract: The heterochromatin-associated H3K9 tri-methylase Suv39h1 is involved in the permanent silencing of E2F target genes in differentiating but not in quiescent cells. Here, we tested the hypothesis that permanent silencing of E2F target genes is associated with their subnuclear positioning close to the pericentromeric heterochromatin compartment, enriched in Suv39h1. Using fluorescence in situ hybridization, we analyzed the subnuclear localization of three E2F target genes relative to the pericentromeric heterochromatin, in cycling fibroblasts or differentiating myoblasts. We observed that all three E2F-target genes have a tendency to relocate closer to the pericentromeric heterochromatin, only when cells differentiate and undergo an irreversible cell cycle withdrawal. These data suggest that repression of E2F target genes in cycling or in differentiating cells is achieved through distinct mechanisms. In differentiating cells, permanent silencing is driven by a Suv39h1-dependent H3K9 tri-methylation and positioning close to the heterochromatin compartment, whereas repression in cycling cells seems independent from subnuclear positioning and requires distinct H3K9 methylation levels.
authors: Institut André Lwoff, Centre National de la Recherche Scientifique (CNRS), FRE2944, Université Paris-Sud, Villejuif, France.
authors: Valentina
authors: V
authors: Guasconi
authors: Linda-Louise
authors: LL
authors: Pritchard
authors: Lauriane
authors: L
authors: Fritsch
authors: Larry D
authors: LD
authors: Mesner
authors: Claire
authors: C
authors: Francastel
authors: Annick
authors: A
authors: Harel-Bellan
authors: Slimane
authors: S
authors: Ait-Si-Ali
mesh_terms: D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D050684:E2F Transcription Factors / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D020868:Gene Silencing / Q000502:physiology*; D006570:Heterochromatin / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D032342:Muscle Cells / Q000166:cytology / Q000378:metabolism*; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D050684:E2F Transcription Factors; D006570:Heterochromatin; D006657:Histones; D012097:Repressor Proteins; C407843:SUV39H1 protein, human; D008780:Methyltransferases