Abstract
Transcriptional dysregulation has emerged as a potentially important pathogenic mechanism in Huntington's disease, a neurodegenerative disorder associated with polyglutamine expansion in the huntingtin (htt) protein. Here, we report the development of a biochemically defined in vitro transcription assay that is responsive to mutant htt. We demonstrate that both gene-specific activator protein Sp1 and selective components of the core transcription apparatus, including TFIID and TFIIF, are direct targets inhibited by mutant htt in a polyglutamine-dependent manner. The RAP30 subunit of TFIIF specifically interacts with mutant htt both in vitro and in vivo to interfere with formation of the RAP30-RAP74 native complex. Importantly, overexpression of RAP30 in cultured primary striatal cells protects neurons from mutant htt-induced cellular toxicity and alleviates the transcriptional inhibition of the dopamine D2 receptor gene by mutant htt. Our results suggest a mutant htt-directed repression mechanism involving multiple specific components of the basal transcription apparatus.
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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Animals
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Biological Assay / methods
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COS Cells
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Cell-Free System
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Cells, Cultured
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Chlorocebus aethiops
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Down-Regulation / drug effects
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Down-Regulation / physiology
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Huntingtin Protein
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Mice
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Mutation
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Nerve Tissue Proteins / genetics*
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Nerve Tissue Proteins / metabolism*
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Nerve Tissue Proteins / pharmacology
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Neurons / cytology
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Neurons / drug effects
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Nuclear Proteins / genetics*
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Nuclear Proteins / metabolism*
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Nuclear Proteins / pharmacology
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Protein Binding / drug effects
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Protein Binding / genetics
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Protein Subunits / antagonists & inhibitors
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Protein Subunits / metabolism
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Rats
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Receptors, Dopamine D2 / genetics
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Sp1 Transcription Factor / antagonists & inhibitors
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Transcription Factor TFIID / antagonists & inhibitors
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Transcription Factor TFIID / metabolism
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Transcription Factors / antagonists & inhibitors*
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Transcription Factors, TFII / antagonists & inhibitors
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Transcription Factors, TFII / metabolism
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Transcription, Genetic / drug effects
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Transcription, Genetic / physiology*
Substances
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HTT protein, human
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Huntingtin Protein
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Nerve Tissue Proteins
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Nuclear Proteins
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Protein Subunits
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Receptors, Dopamine D2
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Sp1 Transcription Factor
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Transcription Factor TFIID
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Transcription Factors
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Transcription Factors, TFII
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transcription factor TFIIF