The role of basal and myogenic factors in the transcriptional activation of utrophin promoter A: implications for therapeutic up-regulation in Duchenne muscular dystrophy.
Duchenne muscular dystrophy (DMD) is an X-linked recessive muscle wasting disease caused by the absence of a muscle cytoskeletal protein, dystrophin. Utrophin is the autosomal homologue of dystrophin. We previously demonstrated that overexpression of utrophin in the muscles of dystrophin-null transgenic mice completely prevented the phenotype arising from dystrophin deficiency. Two independently regulated promoters control utrophin expression and the upstream promoter (promoter A) is synaptically regulated in muscle. In this study, we have investigated basal regulation and myogenic induction of promoter A. Interactions between Ap2 and Sp1 and their cognate DNA motifs are critical for basal transcription from the minimal promoter region. During differentiation of C2C12 myoblasts in vitro, a 2-fold increase in A-utrophin mRNA level was observed. Expression of a reporter gene, whose transcription was driven by a 1.3 kb promoter A fragment, paralleled expression of the endogenous transcript. Myogenic induction mapped to a conserved upstream muscle-specific E-box, which was shown to bind myogenic regulatory factors, transactivating the promoter up to 18-fold in transient assays. This study provides a basis for further understanding the regulatory mechanisms that control utrophin expression in muscle and may facilitate the development of reagents to effect therapeutic up-regulation of utrophin in DMD.
Perkins
K J
KJ
Department of Human Anatomy and Genetics and MRC Functional Genetics Unit, University of Oxford, South Parks Road, Oxford OX1 3QX, UK.
Burton
E A
EA
Davies
K E
KE
D024506:5' Flanking Region; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002460:Cell Line; D017124:Conserved Sequence; D003598:Cytoskeletal Proteins / Q000096:biosynthesis / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000502:physiology; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism*; D020388:Muscular Dystrophy, Duchenne / Q000628:therapy*; D018006:Myogenic Regulatory Factors / Q000502:physiology*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D016329:Sp1 Transcription Factor / Q000502:physiology; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000502:physiology*; D015533:Transcriptional Activation; D015854:Up-Regulation; D049411:Utrophin
D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D018006:Myogenic Regulatory Factors; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D050656:Transcription Factor AP-2; D014157:Transcription Factors; C483600:Utrn protein, mouse; D049411:Utrophin