Transactivation of cardiac MLC-2 promoter by MyoD in 10T1/2 fibroblast cells is independent of E-box requirement but depends upon new proteins that recognize MEF-2 site.
MyoD-mediated activation of skeletal muscle genes, which is dependent upon the consensus E-box sequence, involves, at least in one group of muscle genes, another transcription factor, the myocyte enhancer factor-2 (MEF-2). Since the cardiac myosin light chain-2 (MLC-2) gene promoter lacks the functional E-box but contains the activator MEF-2 site, we tested the effect of ectopic expression of MyoD on cardiac MLC-2 promoter function. Here, we demonstrate that either transient or stable expression of MyoD in otherwise nonpermissive C3H10T1/2 fibroblast cells can promote the expression of MLC-2/CAT. Deletion and site-specific mutation analysis demonstrate that the MEF-2 site (Element B) in the MLC-2 promoter is the target of activation by MyoD. Gel mobility shift assay using nuclear extracts from the normal and MyoD-transfected fibroblast cells did not show a difference in the major MEF-2 binding complexes, except for one complex of fast-moving mobility, which suggested that new MEF-2-like regulatory proteins are induced by MyoD.
Goswami
S K
SK
Department of Anatomy and Cell Biology, SUNY Health Science Center at Brooklyn 11203, USA.
Siddiqui
M A
MA
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D064326:MEF2 Transcription Factors; D051379:Mice; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000096:biosynthesis* / Q000235:genetics; D017570:MyoD Protein / Q000502:physiology*; D018006:Myogenic Regulatory Factors; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D064326:MEF2 Transcription Factors; D009124:Muscle Proteins; D017570:MyoD Protein; D018006:Myogenic Regulatory Factors; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors