title: S1-1/RBM10: multiplicity and cooperativity of nuclear localisation domains.
abstract: BACKGROUND
  S1-1, also called RBM10, is an RNA-binding protein of 852 residues. An alteration of its activity causes TARP syndrome, a severe X-linked disorder with pre- or post-natal lethality in affected males. Its molecular function, although still largely unknown, has been suggested to be transcription and alternative splicing. In fact, S1-1 localises in the nucleus in tissue cells and cultured cells.
  
  
  RESULTS
  By deletion and substitution mutagenesis, a classical 17-amino-acid (aa) nuclear localisation sequence (NLS1) was identified at aa 743-759 in the C-terminal region of S1-1. NLS1 was bipartite, with its N-terminal basic cluster weakly contributing to the NLS activity. S1-1 contained two additional NLSs. One was in the aa 60-136 RNA recognition motif region (NLS2), and the other was a novel NLS motif sequence in the aa 481-540 octamer-repeat (OCRE) region (NLS3). The OCRE is a domain known to be critical in splicing regulation, as shown with RBM5, a close homologue of RBM10 [Bonnal et al. (2008) Mol. Cell 32, 81-95]. The NLS activities were verified by expressing each DNA sequence linked to EGFP or a FLAG tag. These multiple NLSs acted cooperatively, and S1-1 became completely cytoplasmic after the concomitant removal of all NLS domains. In some cell types, however, S1-1 was partly cytoplasmic, suggesting that cellular localisation of S1-1 is subjected to regulation.
  
  
  CONCLUSIONS
  The present results indicate that S1-1 contains multiple NLSs that act cooperatively. Among them, the OCRE is a hitherto unreported NLS. The nuclear localisation of S1-1 appears to be regulated under certain circumstances. We discuss these NLSs in relation to the biochemical processes they are involved in.
authors.affiliation: Department of Immunology, Osaka City University Graduate School of Medicine, Osaka 545-8585, Japan.
authors.forename: Sheng-Jun
authors.initials: SJ
authors.lastname: Xiao
authors.forename: Ling-Yu
authors.initials: LY
authors.lastname: Wang
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Kimura
authors.forename: Hirotada
authors.initials: H
authors.lastname: Kojima
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kunimoto
authors.forename: Fumiko
authors.initials: F
authors.lastname: Nishiumi
authors.forename: Naoki
authors.initials: N
authors.lastname: Yamamoto
authors.forename: Koji
authors.initials: K
authors.lastname: Nishio
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Fujimoto
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kato
authors.forename: Seiichi
authors.initials: S
authors.lastname: Kitagawa
authors.forename: Hideo
authors.initials: H
authors.lastname: Yamane
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakajima
authors.forename: Akira
authors.initials: A
authors.lastname: Inoue
mesh_terms: D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D019913:Nuclear Localization Signals; C512260:RBM10 protein, human; D016601:RNA-Binding Proteins