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: 32.24). 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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    • "PROK2 is very promising biomarker of HD progression. Evidences suggest that gene repression mechanisms are also associated with HD and Zinc finger protein 238 (ZNF238) is a transcriptional repressor which is involved in brain development and myogenesis (Zhai et al., 2005). A recent gene expression study showed that the increase in mRNA levels of Aquaporin 9 (AQP9) and presence of AQP9 in blood could represent peripheral or central inflammatory events when accompanied with increase in levels of four other genes (Mesko et al., 2010). "
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    ABSTRACT: Molecular diagnostics provide a powerful method to detect and diagnose various neurological diseases such as Alzheimer’s and Parkinson’s disease. The confirmation of such diagnosis allows early detection and subsequent medical counseling that help specific patients to undergo clinically important drug trials. This provides a medical pathway to have better insight of neurogenesis and eventual cure of the neurodegenerative diseases. In this short review, we present recent advances in molecular diagnostics especially biomarkers and imaging spectroscopy for neurological diseases. We describe advances made in Alzheimer’s disease, Parkinson’s disease, Amyotrophic lateral sclerosis and Huntington’s disease, and finally present a perspective on the future directions to provide a framework for further developments and refinements of molecular diagnostics to combat neurodegenerative disorders.
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    • "Although there is not a consensus related to the role of SIRT1 in slowing HD lethal phenotype, the majority of the published work systemically describes beneficial effects of SIRT1 activation in multiple cellular pathways, which culminates in neuronal survival and motor improvement . One of them is the enhancement of transcriptional activity, since SIRT1 is primarily nuclear and deacetylates several transcription factors and coactivators [60] [61]. As described before in this review, transcriptional activity is severely impaired in HD models [62] [63] [64]. "
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    ABSTRACT: Sirtuins are a conserved family of NAD(+)-dependent class III lysine deacetylases, known to regulate longevity. In mammals, the sirtuin family has seven members (SIRT1-7), which vary in enzymatic activity, subcellular distribution and targets. Pharmacological and genetic modulation of SIRTs has been widely spread as a promising approach to slow aging and neurodegenerative processes. Huntington's disease (HD) is a neurodegenerative disorder linked to expression of polyglutamine-expanded huntingtin (HTT) protein for which there is still no disease-reversing treatment. Studies in different animal models provide convincing evidence that SIRT1 protects both cellular and animal models from mutant HTT toxicity, however controversial results were recently reported. Indeed, as a consequence of a variety of SIRT-activation pathways, either activation or inhibition of a specific SIRT appears to be neuroprotective. Therefore, this review summarizes the recent progress and knowledge in sirtuins (particularly SIRT1-3) and their implications for HD treatment. Copyright © 2015. Published by Elsevier B.V.
    Biochimica et Biophysica Acta 07/2015; DOI:10.1016/j.bbadis.2015.07.003 · 4.66 Impact Factor
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    • "Therefore, we suggest that at early stage of the disease, striatal enkephalin could play a role in the reduction of excitotoxicity. Nevertheless, based on downregulation of transcription of several important neuronal genes [80]–[82] and further disease progression (atrophy of corticostriatal afferents and the progressive neurodegeneration of striatonigral dynorphin-containing neurons at later stage of disease), the level of opioid receptors might also be gradually downregulated, and the positive effect of enkephalin on striatal neuron morphology may eventually fail. Indeed, the reduction of striatal opioid receptor binding (20% to 40%) was shown in HD patients [83]. "
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    ABSTRACT: The reduction of pre-enkephalin (pENK) mRNA expression might be an early sign of striatal neuronal dysfunction in Huntington's disease (HD), due to mutated huntingtin protein. Indeed, striatopallidal (pENK-containing) neurodegeneration occurs at earlier stage of the disease, compare to the loss of striatonigral neurons. However, no data are available about the functional role of striatal pENK in HD. According to the neuroprotective properties of opioids that have been recognized recently, the objective of this study was to investigate whether striatal overexpression of pENK at early stage of HD can improve motor dysfunction, and/or reduce striatal neuronal loss in the R6/2 transgenic mouse model of HD. To achieve this goal recombinant adeno-associated-virus (rAAV2)-containing green fluorescence protein (GFP)-pENK was injected bilaterally in the striatum of R6/2 mice at 5 weeks old to overexpress opioid peptide pENK. Striatal injection of rAAV2-GFP was used as a control. Different behavioral tests were carried out before and/or after striatal injections of rAAV2. The animals were euthanized at 10 weeks old. Our results demonstrate that striatal overexpression of pENK had beneficial effects on behavioral symptoms of HD in R6/2 by: delaying the onset of decline in muscular force; reduction of clasping; improvement of fast motor activity, short-term memory and recognition; as well as normalization of anxiety-like behavior. The improvement of behavioral dysfunction in R6/2 mice having received rAAV2-GFP-pENK associated with upregulation of striatal pENK mRNA; the increased level of enkephalin peptide in the striatum, globus pallidus and substantia nigra; as well as the slight increase in the number of striatal neurons compared with other groups of R6/2. Accordingly, we suggest that at early stage of HD upregulation of striatal enkephalin might play a key role at attenuating illness symptoms.
    PLoS ONE 09/2013; 8(9):e75099. DOI:10.1371/journal.pone.0075099 · 3.23 Impact Factor
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