Ets-2 repressor factor silences extrasynaptic utrophin by N-box mediated repression in skeletal muscle.
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.
Perkins
Kelly J
KJ
Department of Physiology and Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6085, USA.
Basu
Utpal
U
Budak
Murat T
MT
Ketterer
Caroline
C
Baby
Santhosh M
SM
Lozynska
Olga
O
Lunde
John A
JA
Jasmin
Bernard J
BJ
Rubinstein
Neal A
NA
Khurana
Tejvir S
TS
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
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