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Polyglutamine domain modulates the TBP-TFIIB interaction: implications for its normal function and neurodegeneration
Meyer J Friedman1, Anjali G Shah, Zhi-Hui Fang
1Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Atlanta, Georgia 30322, USA.
Nature Neuroscience
|November 13, 2007
Summary
Polyglutamine (polyQ) expansion in TATA-box binding protein (TBP) causes spinocerebellar ataxia 17 (SCA17). Expanded polyQ tracts disrupt TBP function and neuroprotection, offering insights into SCA17 molecular pathogenesis.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- Spinocerebellar ataxia 17 (SCA17) is a neurodegenerative disease linked to polyglutamine (polyQ) tract expansion in the TATA-box binding protein (TBP).
- The precise mechanisms by which polyQ expansion in TBP affects protein function and leads to neuropathology are not fully understood.
Purpose of the Study:
- To investigate the functional consequences of polyQ-expanded TBP on protein interactions and transcriptional regulation.
- To elucidate the molecular pathogenesis of SCA17 by examining TBP's role in neurodegeneration and neuroprotection.
Main Methods:
- Generation of transgenic mice expressing polyglutamine-expanded TBP.
- Analysis of TBP dimerization and interaction with general transcription factor IIB (TFIIB).
- Assessment of small heat shock protein HSPB1 (a neuroprotective factor) levels and TFIIB promoter occupancy in SCA17 models.
Main Results:
- Transgenic mice exhibited weight loss, neurological deficits, and neurodegeneration.
- Expanded polyQ tracts in TBP reduced dimerization but increased TFIIB interaction.
- Downregulation of HSPB1 and decreased TFIIB occupancy at the Hspb1 promoter were observed in SCA17 mice.
- Overexpression of HSPB1 or TFIIB ameliorated mutant TBP-induced neuritic defects.
Conclusions:
- The polyglutamine domain of TBP plays a critical role in transcriptional regulation.
- Dysregulation of TBP function and impaired neuroprotective mechanisms contribute to SCA17 pathogenesis.
- Targeting HSPB1 or TFIIB may offer therapeutic strategies for SCA17.
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