title: LINE-1 silencing by retinoblastoma proteins is effected through the nucleosomal and remodeling deacetylase multiprotein complex.
abstract: BACKGROUND
  Long Interspersed Nuclear Element-1 (L1) is an oncogenic mammalian retroelement silenced early in development via tightly controlled epigenetic mechanisms. We have previously shown that the regulatory region of human and murine L1s interact with retinoblastoma (RB) proteins to effect retroelement silencing. The present studies were conducted to identify the corepressor complex responsible for RB-mediated silencing of L1.
  
  
  METHODS
  Chromatin immunoprecipitation and silencing RNA technology were used to identify the repressor complex that silences L1 in human and murine cells.
  
  
  RESULTS
  Components of the Nucleosomal and Remodeling Deacetylase (NuRD) multiprotein complex specifically enriched the L1 5'-untranslated DNA sequence in human and murine cells. Genetic ablation of RB proteins in murine cells destabilized interactions within the NuRD macromolecular complex and mediated nuclear rearrangement of Mi2-β, an ATP-dependent helicase subunit with nucleosome remodeling activity. Depletion of Mi2-β, RbAP46 and HDAC2 reduced the repressor activity of the NuRD complex and reactivated a synthetic L1 reporter in human cells. Epigenetic reactivation of L1 in RB-null cells by DNA damage was markedly enhanced compared to wild type cells.
  
  
  CONCLUSIONS
  RB proteins stabilize interactions of the NuRD corepressor complex within the L1 promoter to effect L1 silencing. L1 retroelements may serve as a scaffold on which RB builds heterochromatic regions that regulate chromatin function.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, KY, 40202, USA. diego.montoya-durango@louisville.edu.
authors.forename: Diego E
authors.initials: DE
authors.lastname: Montoya-Durango
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, KY, 40202, USA. kenramos@live.com.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Ramos
authors.affiliation: Department of Medicine, University of Arizona College of Medicine, Tucson, AZ, 85721, USA. pbojang@email.arizona.edu.
authors.forename: Pasano
authors.initials: P
authors.lastname: Bojang
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, KY, 40202, USA. lorellruiz@gmail.com.
authors.forename: Lorell
authors.initials: L
authors.lastname: Ruiz
authors.affiliation: Department of Health Promotion Sciences, University of Arizona College of Public Health, Tucson, AZ, 85721, USA. inramos@email.arizona.edu.
authors.forename: Irma N
authors.initials: IN
authors.lastname: Ramos
authors.affiliation: Department of Medicine, University of Arizona College of Medicine, Tucson, AZ, 85721, USA. ksramos@email.arizona.edu.
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Ramos
mesh_terms: D000818:Animals; D002843:Chromatin / Q000235:genetics; D042002:Chromatin Assembly and Disassembly / Q000235:genetics; D004265:DNA Helicases / Q000235:genetics; D044127:Epigenesis, Genetic; D006801:Humans; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics*; D056245:Mi-2 Nucleosome Remodeling and Deacetylase Complex / Q000235:genetics*; D051379:Mice; D009707:Nucleosomes / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D016160:Retinoblastoma Protein / Q000235:genetics*
chemical_list: D002843:Chromatin; D009707:Nucleosomes; D016160:Retinoblastoma Protein; D056245:Mi-2 Nucleosome Remodeling and Deacetylase Complex; D004265:DNA Helicases
references.citation: J Immunol. 2000 Sep 15;165(6):3239-49
references.pmid: 10975840
references.citation: Mol Oncol. 2013 Aug;7(4):812-25
references.pmid: 23648019
references.citation: Nucleic Acids Res. 2001 Nov 1;29(21):4493-501
references.pmid: 11691937
references.citation: Cell. 2003 Apr 18;113(2):207-19
references.pmid: 12705869
references.citation: J Biol Chem. 2003 Jul 25;278(30):28201-9
references.pmid: 12714586
references.citation: Immunity. 2004 Jun;20(6):719-33
references.pmid: 15189737
references.citation: Cell. 2004 Oct 1;119(1):75-86
references.pmid: 15454082
references.citation: Oncogene. 1999 Mar 25;18(12):2091-100
references.pmid: 10321733
references.citation: Genes Dev. 1999 Aug 1;13(15):1924-35
references.pmid: 10444591
references.citation: Mol Cell Biol. 1999 Oct;19(10):6632-41
references.pmid: 10490602
references.citation: Oncogene. 2004 Nov 18;23(54):8841-6
references.pmid: 15480421
references.citation: J Biol Chem. 2004 Dec 10;279(50):52456-64
references.pmid: 15456747
references.citation: EMBO J. 2005 Feb 23;24(4):800-12
references.pmid: 15678104
references.citation: Curr Opin Genet Dev. 2005 Apr;15(2):163-76
references.pmid: 15797199
references.citation: Cell. 2006 Apr 21;125(2):315-26
references.pmid: 16630819
references.citation: Cancer Epidemiol Biomarkers Prev. 2007 Jan;16(1):108-14
references.pmid: 17220338
references.citation: Genes Cells. 2007 Oct;12(10):1101-10
references.pmid: 17903170
references.citation: J Biol Chem. 2008 May 16;283(20):13825-33
references.pmid: 18353770
references.citation: Genome Res. 2009 Feb;19(2):221-33
references.pmid: 19047520
references.citation: Mutat Res. 2009 Jun 1;665(1-2):20-8
references.pmid: 19427507
references.citation: Mol Cell. 2010 Feb 26;37(4):457-68
references.pmid: 20188665
references.citation: Nucleic Acids Res. 2010 Jul;38(12):3909-22
references.pmid: 20215437
references.citation: Nature. 2010 Nov 18;468(7322):443-6
references.pmid: 21085180
references.citation: Epigenetics. 2011 Mar;6(3):355-67
references.pmid: 21150308
references.citation: Nat Rev Cancer. 2011 Aug;11(8):588-96
references.pmid: 21734722
references.citation: FEBS Lett. 2012 Jan 2;586(1):102-6
references.pmid: 22172279
references.citation: Hum Mutat. 2012 Feb;33(2):369-71
references.pmid: 22095564
references.citation: Science. 2012 Aug 24;337(6097):967-71
references.pmid: 22745252
references.citation: Mol Cell Biol. 2012 Dec;32(24):5078-88
references.pmid: 23071088
references.citation: Mol Cell Biol. 2001 Apr;21(8):2918-32
references.pmid: 11283269