title: In vitro analysis of huntingtin-mediated transcriptional repression reveals multiple transcription factor targets.
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.
authors.affiliation: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, 401 Barker Hall, Berkeley, CA 94720, USA.
authors.forename: Weiguo
authors.initials: W
authors.lastname: Zhai
authors.forename: Hyunkyung
authors.initials: H
authors.lastname: Jeong
authors.forename: Libin
authors.initials: L
authors.lastname: Cui
authors.forename: Dimitri
authors.initials: D
authors.lastname: Krainc
authors.forename: Robert
authors.initials: R
authors.lastname: Tjian
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods; D019556:COS Cells; D002474:Cell-Free System; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D000071058:Huntingtin Protein; D051379:Mice; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017448:Receptors, Dopamine D2 / Q000235:genetics; D016329:Sp1 Transcription Factor / Q000037:antagonists & inhibitors; D035362:Transcription Factor TFIID / Q000037:antagonists & inhibitors / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors*; D019473:Transcription Factors, TFII / Q000037:antagonists & inhibitors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*
chemical_list: C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D021122:Protein Subunits; D017448:Receptors, Dopamine D2; D016329:Sp1 Transcription Factor; D035362:Transcription Factor TFIID; D014157:Transcription Factors; D019473:Transcription Factors, TFII; C056604:transcription factor TFIIF