MEF-2 and Oct-1 bind to two homologous promoter sequence elements and participate in the expression of a skeletal muscle-specific gene.
The murine adult IIB myosin heavy chain (IIB MyHC) gene is expressed only in certain skeletal muscle fibers. Within the proximal promoter are two A + T-rich motifs, mAT1 and mAT2, which greatly enhance muscle-specific transcription; myogenic cells contain proteins that bind to these sequences. MEF-2 binds to both mAT1 and mAT2; a mutation abolishing its binding to mAT1 greatly diminishes the activity of the promoter. Both mAT motifs also form complexes with a protein requiring a target sequence typical of POU domain proteins, which migrate in electrophoretic mobility shift assays to the same position as a complex containing purified Oct-1 and which are supershifted by an antibody specific to Oct-1; this protein is therefore probably Oct-1. Footprinting experiments demonstrate that mAT1 is preferentially occupied by MEF-2 and mAT2 by Oct-1 and that these two proteins appear to bind cooperatively to their respective sites. Although the two mAT motifs have sequences that are very similar, they nonetheless exhibit distinct behaviors and perform differently in the activation of the promoter. The contribution of the IIB MyHC gene to specification of the myogenic phenotype is thus at least in part regulated by MEF-2 and Oct-1.
Lakich
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MM
Unité de Biochimie, Département de Biologie Moléculaire, Institut Pasteur, 28 rue du Dr. Roux, 75724 Paris Cedex 15, France. melissa-lakich@rp.rorer.com
Diagana
T T
TT
North
D L
DL
Whalen
R G
RG
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000235:genetics*; D017930:Genes, Reporter / Q000235:genetics; D051863:Host Cell Factor C1; D064326:MEF2 Transcription Factors; D051379:Mice; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics; D018482:Muscle, Skeletal / Q000502:physiology*; D018006:Myogenic Regulatory Factors; D018995:Myosin Heavy Chains / Q000235:genetics*; D009687:Nuclear Proteins / Q000032:analysis; D050811:Octamer Transcription Factor-1; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*
D004268:DNA-Binding Proteins; C497693:Hcfc1 protein, mouse; D051863:Host Cell Factor C1; D064326:MEF2 Transcription Factors; D009124:Muscle Proteins; D018006:Myogenic Regulatory Factors; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; C494166:Pou2f1 protein, mouse; D014157:Transcription Factors; D018995:Myosin Heavy Chains