title: The importance of serine 776 in Ataxin-1 partner selection: a FRET analysis.
abstract: Anomalous expansion of a polymorphic tract in Ataxin-1 causes the autosomal dominant spinocerebellar ataxia type 1. In addition to polyglutamine expansion, requirements for development of pathology are phosphorylation of serine 776 in Ataxin-1 and nuclear localization of the protein. The phosphorylation state of serine 776 is also crucial for selection of the Ataxin-1 multiple partners. Here, we have used FRET for an in cell study of the interaction of Ataxin-1 with the spliceosome-associated U2AF65 and the adaptor 14-3-3 proteins. Using wild-type Ataxin-1 and Ser776 mutants to a phosphomimetic aspartate and to alanine, we show that U2AF65 binds Ataxin-1 in a Ser776 phosphorylation independent manner whereas 14-3-3 interacts with phosphorylated wild-type Ataxin-1 but not with the mutants. These results indicate that Ser776 acts as the molecular switch that discriminates between normal and aberrant function and that phosphomimetics is not a generally valid approach whose applicability should be carefully validated.
authors.affiliation: MRC National Institute for Medical Research , The Ridgeway, London NW7 1AA UK. rmenon@nimr.mrc.ac.uk
authors.forename: Rajesh P
authors.initials: RP
authors.lastname: Menon
authors.forename: Daniel
authors.initials: D
authors.lastname: Soong
authors.forename: Cesira
authors.initials: C
authors.lastname: de Chiara
authors.forename: Mark R
authors.initials: MR
authors.lastname: Holt
authors.forename: Narayana
authors.initials: N
authors.lastname: Anilkumar
authors.forename: Annalisa
authors.initials: A
authors.lastname: Pastore
mesh_terms: D048948:14-3-3 Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000067696:Ataxin-1; D000067528:Ataxins; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D031541:Fluorescence Resonance Energy Transfer; D017930:Genes, Reporter; D006801:Humans; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012261:Ribonucleoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000072668:Splicing Factor U2AF
chemical_list: D048948:14-3-3 Proteins; C000593749:ATXN1 protein, human; D000067696:Ataxin-1; D000067528:Ataxins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins; D000072668:Splicing Factor U2AF; C000607494:U2AF2 protein, human; D012694:Serine