The intracellular domain of mouse Notch: a constitutively activated repressor of myogenesis directed at the basic helix-loop-helix region of MyoD.
We show that Myf-5 and mNotch mRNA are both present in the presomitic mesoderm before muscle cell commitment and before muscle structural gene activation. The failure of presomitic mesoderm to respond to Myf-5 and express myogenic properties implies that there may be a mechanism in presomitic mesoderm to suppress muscle differentiation. Here we show that ectopic expression of the intracellular domain of mNotch (mNotchIC) functions as a constitutively activated repressor of myogenesis both in cultured cells and in frog embryos. Mutagenesis experiments indicate that the target for inactivation by mNotch is the MyoD basic helix-loop-helix domain. mNotchIC contains a nuclear localization signal and localizes to the nucleus. Removal of the nuclear localization signal (NLS) reduces nuclear localization and diminishes the inhibition of myogenesis caused by Myf-5 or MyoD. Additional experiments show that the CDC10/SWI6/ankyrin repeats are also necessary for myogenic inhibition.
Fred Hutchinson Cancer Research Center, Howard Hughes Medical Institute, Seattle, WA 98104.
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Kopan
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JS
Nye
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Weintraub
D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins; D015870:Gene Expression; D018257:Helix-Loop-Helix Motifs; D017403:In Situ Hybridization; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000235:genetics; D009124:Muscle Proteins / Q000235:genetics; D009132:Muscles / Q000196:embryology*; D017570:MyoD Protein / Q000235:genetics*; D051787:Myogenic Regulatory Factor 5; D016133:Polymerase Chain Reaction; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D012097:Repressor Proteins / Q000235:genetics*; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics
D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; C497418:Myf5 protein, mouse; D017570:MyoD Protein; C057363:MyoD1 myogenic differentiation protein; D051787:Myogenic Regulatory Factor 5; C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors