title: Ets-2 repressor factor silences extrasynaptic utrophin by N-box mediated repression in skeletal muscle.
abstract: Utrophin is the autosomal homologue of dystrophin, the protein product of the Duchenne's muscular dystrophy (DMD) locus. Utrophin expression is temporally and spatially regulated being developmentally down-regulated perinatally and enriched at neuromuscular junctions (NMJs) in adult muscle. Synaptic localization of utrophin occurs in part by heregulin-mediated extracellular signal-regulated kinase (ERK)-phosphorylation, leading to binding of GABPalpha/beta to the N-box/EBS and activation of the major utrophin promoter-A expressed in myofibers. However, molecular mechanisms contributing to concurrent extrasynaptic silencing that must occur to achieve NMJ localization are unknown. We demonstrate that the Ets-2 repressor factor (ERF) represses extrasynaptic utrophin-A in muscle. Gel shift and chromatin immunoprecipitation studies demonstrated physical association of ERF with the utrophin-A promoter N-box/EBS site. ERF overexpression repressed utrophin-A promoter activity; conversely, small interfering RNA-mediated ERF knockdown enhanced promoter activity as well as endogenous utrophin mRNA levels in cultured muscle cells in vitro. Laser-capture microscopy of tibialis anterior NMJ and extrasynaptic transcriptomes and gene transfer studies provide spatial and direct evidence, respectively, for ERF-mediated utrophin repression in vivo. Together, these studies suggest "repressing repressors" as a potential strategy for achieving utrophin up-regulation in DMD, and they provide a model for utrophin-A regulation in muscle.
authors.affiliation: Department of Physiology and Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6085, USA.
authors.forename: Kelly J
authors.initials: KJ
authors.lastname: Perkins
authors.forename: Utpal
authors.initials: U
authors.lastname: Basu
authors.forename: Murat T
authors.initials: MT
authors.lastname: Budak
authors.forename: Caroline
authors.initials: C
authors.lastname: Ketterer
authors.forename: Santhosh M
authors.initials: SM
authors.lastname: Baby
authors.forename: Olga
authors.initials: O
authors.lastname: Lozynska
authors.forename: John A
authors.initials: JA
authors.lastname: Lunde
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Jasmin
authors.forename: Neal A
authors.initials: NA
authors.lastname: Rubinstein
authors.forename: Tejvir S
authors.initials: TS
authors.lastname: Khurana
mesh_terms: D000818:Animals; D001483:Base Sequence; D047369:Chromatin Immunoprecipitation; D023902:Chromosome Pairing; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000378:metabolism*; D004331:Drosophila melanogaster; D005121:Extremities; D051268:GA-Binding Protein Transcription Factor / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D018014:Gene Transfer Techniques; D006801:Humans; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D049411:Utrophin / Q000235:genetics* / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C522019:Erf protein, mouse; D051268:GA-Binding Protein Transcription Factor; C495656:Gabpa protein, mouse; D012333:RNA, Messenger; D012097:Repressor Proteins; D049411:Utrophin