title: Insights into the evolution and domain structure of Ataxin-2 proteins across eukaryotes.
abstract: BACKGROUND
  Ataxin-2 is an evolutionarily conserved protein first identified in humans as responsible for spinocerebellar ataxia type 2 (SCA2). The molecular basis of SCA2 is the expansion of a polyglutamine tract in Ataxin-2, encoding a Lsm domain that may bind RNA and a PAM2 motif that enables interaction with the poly (A) binding protein. Although the association with SCA2 has been verified, a detailed molecular function for Ataxin-2 has not been established.
  
  
  RESULTS
  We have undertaken a survey of Ataxin-2 proteins across all eukaryotic domains. In eukaryotes, except for vertebrates and land plants, a single ortholog was identified. Notably, with the exception of birds, two Ataxin-2 genes exist in vertebrates. Expansion was observed in land plants and a novel class lacking the LsmAD domain was identified. Large polyQ tracts appear limited to primates and insects of the orders Hymenoptera and Diptera. A common feature across Ataxin-2 orthologs is the presence of proline-rich motifs, formerly described in the human protein.
  
  
  CONCLUSIONS
  Our analysis provides valuable information on the evolution and domain structure of Ataxin-2 proteins. Proline-rich motifs that may mediate protein interactions are widespread in Ataxin-2 proteins, but expansion of polyglutamine tracts associated with spinocerebellar ataxia type 2, is present only in primates, as well as some insects. Our analysis of Ataxin-2 proteins provides also a source to examine orthologs in a number of different species.
authors.forename: Domingo
authors.initials: D
authors.lastname: Jiménez-López
authors.affiliation: Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados, Unidad Irapuato, Apartado Postal 629, Irapuato, Gto 36821, México. pguzman@ira.cinvestav.mx.
authors.forename: Plinio
authors.initials: P
authors.lastname: Guzmán
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000067528:Ataxins; D019143:Evolution, Molecular; D006801:Humans; D007448:Invertebrates / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics*; D010455:Peptides / Q000737:chemistry / Q000235:genetics; D010802:Phylogeny; D010944:Plants / Q000145:classification / Q000235:genetics*; D055232:Proline-Rich Protein Domains / Q000235:genetics; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014714:Vertebrates / Q000145:classification / Q000235:genetics*
chemical_list: D000067528:Ataxins; D009419:Nerve Tissue Proteins; D010455:Peptides; D020033:Protein Isoforms; C097188:polyglutamine