Perturbation of U2AF65/NXF1-mediated RNA nuclear export enhances RNA toxicity in polyQ diseases

• Published in: Human molecular genetics 2011-10, Vol.20 (19), p.3787-3797
• Main Authors: Tsoi, Ho, Lau, Chi Kong, Lau, Kwok Fai, Chan, Ho Yin Edwin
• Format: Article
• Language: English
• Subjects: Active Transport, Cell Nucleus; Animals; Animals, Genetically Modified; Biological and medical sciences; Cell Line; Cell Nucleus - genetics; Cell Nucleus - metabolism; Disease Models, Animal; Drosophila; Drosophila - genetics; Drosophila - metabolism; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; Humans; Mice; Mice, Transgenic; Molecular and cellular biology; Neurodegenerative Diseases - genetics; Neurodegenerative Diseases - metabolism; Nuclear Proteins - chemistry; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Nucleocytoplasmic Transport Proteins - genetics; Nucleocytoplasmic Transport Proteins - metabolism; Protein Binding; Protein Structure, Tertiary; Ribonucleoprotein, U2 Small Nuclear; Ribonucleoproteins - chemistry; Ribonucleoproteins - genetics; Ribonucleoproteins - metabolism; RNA - genetics; RNA - metabolism; RNA - toxicity; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; Splicing Factor U2AF; Trinucleotide Repeat Expansion
• ISSN: 0964-6906; 1460-2083
• DOI: 10.1093/hmg/ddr297

Expanded CAG RNA has recently been reported to contribute to neurotoxicity in polyglutamine (polyQ) degeneration. In this study, we showed that RNA carrying an expanded CAG repeat progressively accumulated in the cell nucleus of transgenic Drosophila that displayed degeneration. Our gene knockdown and mutant analyses demonstrated that reduction of U2AF50 function, a gene involved in RNA nuclear export, intensified nuclear accumulation of expanded CAG RNA and resulted in a concomitant exacerbation of expanded CAG RNA-mediated toxicity in vivo. We found that the human U2AF50 ortholog, U2AF65, interacted directly and specifically with expanded CAG RNA via its RRM3 domain. We further identified an RNA/protein complex that consisted of expanded CAG RNA, U2AF65 and the NXF1 nuclear export receptor. The U2AF65 protein served as an adaptor to link expanded CAG RNA to NXF1 for RNA export. Finally, we confirmed the nuclear accumulation of expanded CAG RNA in symptomatic polyQ transgenic mice and also observed a neurodevelopmental downregulation of U2AF65 protein levels in mice. Altogether, our findings demonstrate that the cell nucleus is a site where expanded CAG RNA exerts its toxicity. We also provide a novel mechanistic explanation to how perturbation of RNA nuclear export would contribute to polyQ degeneration.