title: ATAXIN-1 interacts with the repressor Capicua in its native complex to cause SCA1 neuropathology.
abstract: Spinocerebellar ataxia type 1 (SCA1) is one of several neurodegenerative diseases caused by expansion of a polyglutamine tract in the disease protein, in this case, ATAXIN-1 (ATXN1). A key question in the field is whether neurotoxicity is mediated by aberrant, novel interactions with the expanded protein or whether its wild-type functions are augmented to a deleterious degree. We examined soluble protein complexes from mouse cerebellum and found that the majority of wild-type and expanded ATXN1 assembles into large stable complexes containing the transcriptional repressor Capicua. ATXN1 directly binds Capicua and modulates Capicua repressor activity in Drosophila and mammalian cells, and its loss decreases the steady-state level of Capicua. Interestingly, the S776A mutation, which abrogates the neurotoxicity of expanded ATXN1, substantially reduces the association of mutant ATXN1 with Capicua in vivo. These data provide insight into the function of ATXN1 and suggest that SCA1 neuropathology depends on native, not novel, protein interactions.
authors.affiliation: Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Yung C
authors.initials: YC
authors.lastname: Lam
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Bowman
authors.forename: Paymaan
authors.initials: P
authors.lastname: Jafar-Nejad
authors.forename: Janghoo
authors.initials: J
authors.lastname: Lim
authors.forename: Ronald
authors.initials: R
authors.lastname: Richman
authors.forename: John D
authors.initials: JD
authors.lastname: Fryer
authors.forename: Eric D
authors.initials: ED
authors.lastname: Hyun
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Duvick
authors.forename: Harry T
authors.initials: HT
authors.lastname: Orr
authors.forename: Juan
authors.initials: J
authors.lastname: Botas
authors.forename: Huda Y
authors.initials: HY
authors.lastname: Zoghbi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D000067696:Ataxin-1; D000067528:Ataxins; D001921:Brain / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism*; D017124:Conserved Sequence; D004330:Drosophila / Q000196:embryology / Q000502:physiology*; D005124:Eye Abnormalities / Q000209:etiology; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D020754:Spinocerebellar Ataxias / Q000209:etiology* / Q000235:genetics; D014158:Transcription, Genetic; D014921:Wings, Animal / Q000002:abnormalities
chemical_list: C000593749:ATXN1 protein, human; D000067696:Ataxin-1; D000067528:Ataxins; C000593750:Atxn1 protein, mouse; C498611:Cic protein, mouse; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D012097:Repressor Proteins; C097188:polyglutamine