Abstract
In the present study, we report that ubiquitin-mediated degradation of dMyc, the Drosophila homologue of the human c-myc proto-oncogene, is regulated in vitro and in vivo by members of the casein kinase 1 (CK1) family and by glycogen synthase kinase 3beta (GSK3beta). Using Drosophila S2 cells, we demonstrate that CK1alpha promotes dMyc ubiquitination and degradation with a mechanism similar to the one mediated by GSK3beta in vertebrates. Mutation of ck1alpha or -epsilon or sgg/gsk3beta in Drosophila wing imaginal discs results in the accumulation of dMyc protein, suggesting a physiological role for these kinases in vivo. Analysis of the dMyc amino acid sequence reveals the presence of conserved domains containing potential phosphorylation sites for mitogen kinases, GSK3beta, and members of the CK1 family. We demonstrate that mutations of specific residues within these phosphorylation domains regulate dMyc protein stability and confer resistance to degradation by CK1alpha and GSK3beta kinases. Expression of the dMyc mutants in the compound eye of the adult fly results in a visible defect that is attributed to the effect of dMyc on growth, cell death, and inhibition of ommatidial differentiation.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Animals
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Animals, Genetically Modified
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Casein Kinase 1 epsilon / genetics
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Casein Kinase 1 epsilon / metabolism*
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Casein Kinase Ialpha / genetics
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Casein Kinase Ialpha / metabolism*
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Cell Line
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Conserved Sequence
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DNA-Binding Proteins / chemistry
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Drosophila Proteins / chemistry
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Drosophila Proteins / genetics
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Drosophila Proteins / metabolism*
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Drosophila melanogaster / genetics
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Drosophila melanogaster / metabolism
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Eye / growth & development
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Eye / metabolism
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Genes, Insect
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Glycogen Synthase Kinase 3 / genetics
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Glycogen Synthase Kinase 3 / metabolism*
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Glycogen Synthase Kinase 3 beta
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Humans
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Mutagenesis, Site-Directed
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Protein Structure, Tertiary
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Proto-Oncogene Mas
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Transcription Factors / chemistry
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Ubiquitin / metabolism*
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Wings, Animal / growth & development
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Wings, Animal / metabolism
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Wnt1 Protein / genetics
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Wnt1 Protein / metabolism
Substances
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DNA-Binding Proteins
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Drosophila Proteins
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MAS1 protein, human
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Myc protein, Drosophila
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Proto-Oncogene Mas
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Recombinant Proteins
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Transcription Factors
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Ubiquitin
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Wnt1 Protein
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wg protein, Drosophila
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Casein Kinase 1 epsilon
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Casein Kinase Ialpha
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GSK3B protein, human
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Glycogen Synthase Kinase 3 beta
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Sgg protein, Drosophila
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Glycogen Synthase Kinase 3