In Vitro Analysis of Huntingtin-Mediated Transcriptional Repression Reveals Multiple Transcription Factor Targets

Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, 401 Barker Hall, Berkeley, CA 94720, USA.
Cell (Impact Factor: 33.12). 01/2006; 123(7):1241-53. DOI: 10.1016/j.cell.2005.10.030
Source: PubMed

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.

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