Abstract
The Hairy/Enhancer of split/Deadpan family of basic helix-loop-helix (bHLH) proteins function as transcriptional repressors. We have examined the mechanisms of repression used by the Hairy and E(SPL) proteins by assaying the antagonism between wild-type or altered Hairy/E(SPL) and Scute bHLH proteins during sex determination in Drosophila melanogaster. Domain swapping and mutagenesis of the Hairy and E(SPL) proteins show that three evolutionarily conserved domains are required for their function: the bHLH, Orange, and WRPW domains. However, the suppression of Scute activity by Hairy does not require the WRPW domain. We show that the Orange domain is an important functional domain that confers specificity among members of the Hairy/E(SPL) family. In addition, we show that a Xenopus Hairy homology conserves not only Hairy's structure but also its biological activity in our assays. We propose that transcriptional repression by the Hairy/E(SPL) family of bHLH proteins involves two separable mechanisms: repression of specific transcriptional activators, such as Scute, through the bHLH and Orange domains and repression of other activators via interaction of the C-terminal WRPW motif with corepressors, such as the Groucho protein.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
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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Basic Helix-Loop-Helix Transcription Factors
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Biological Evolution
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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*
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Drosophila melanogaster / genetics
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Drosophila melanogaster / physiology*
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Enhancer Elements, Genetic*
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Female
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Gene Expression Regulation*
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Genotype
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Helix-Loop-Helix Motifs*
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Insect Hormones / chemistry
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Insect Hormones / genetics
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Insect Hormones / metabolism*
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Insect Proteins*
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Male
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Models, Genetic
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Molecular Sequence Data
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Mutagenesis
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Mutagenesis, Site-Directed
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Point Mutation
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / metabolism
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Repressor Proteins*
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Sequence Deletion
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Sequence Homology, Amino Acid
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Sex Determination Analysis
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Substrate Specificity
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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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Transcription, Genetic*
Substances
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Basic Helix-Loop-Helix Transcription Factors
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DNA-Binding Proteins
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Drosophila Proteins
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E(spl)mdelta-HLH protein, Drosophila
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Insect Hormones
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Insect Proteins
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Recombinant Fusion Proteins
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Repressor Proteins
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Transcription Factors
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hairy protein, Drosophila
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hairy protein, insect