Zhai Weiguo, Jeong Hyunkyung, Cui Libin, Krainc Dimitri, Tjian Robert
Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, 401 Barker Hall, Berkeley, CA 94720, USA.
Cell. 2005 Dec 29;123(7):1241-53. doi: 10.1016/j.cell.2005.10.030.
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.
转录失调已成为亨廷顿舞蹈症潜在的重要致病机制，亨廷顿舞蹈症是一种与亨廷顿蛋白（htt）中多聚谷氨酰胺扩展相关的神经退行性疾病。在此，我们报告了一种对突变型htt有反应的生化定义的体外转录测定法的开发。我们证明基因特异性激活蛋白Sp1以及核心转录装置的选择性组分，包括TFIID和TFIIF，都是被突变型htt以多聚谷氨酰胺依赖的方式直接抑制的靶点。TFIIF的RAP30亚基在体外和体内均与突变型htt特异性相互作用，以干扰RAP30-RAP74天然复合物的形成。重要的是，在原代培养的纹状体细胞中过表达RAP30可保护神经元免受突变型htt诱导的细胞毒性，并减轻突变型htt对多巴胺D2受体基因的转录抑制。我们的结果提示了一种涉及基础转录装置多个特定组分的突变型htt定向抑制机制。
