title: Xenopus single-minded (xSim) is a nuclear factor allowing nuclear translocation of its cytoplasmic partner xArnt.
abstract: Transcription factors belonging to the basic helix-loop-helix Per-Arnt-Sim (bHLH/PAS) family control a wide variety of biological processes in mammalian and/or Drosophila. We have previously isolated bHLH/PAS Xenopus amphibian homologs of Single-minded (xSim) and aryl receptor nuclear translocator (xArnt) and characterized their expression pattern during embryogenesis. We show in this paper that xSim protein is a functional homolog of Drosophila or mammalian Sim(s). Biochemical analysis indicates that xSim forms a heterodimer with xArnt. Subcellular localization analysis of bHLH/PAS chimeric fluorescent versions in Xenopus or mammalian cell lines shows that xSim is constitutively localized in the nuclear compartment. On the opposite, xArnt appears to be predominantly expressed in the cytoplasm. In addition, we demonstrate that xArnt nuclear localization depends on the presence of xSim. Thus xSim appears to be an essential factor in the nuclear translocation of the xSim/xArnt complex. In perfect agreement, we show that the C-terminal half of xSim contains the information for this nuclear localization.
authors.affiliation: Université Pierre et Marie Curie, UMR7622-CNRS Biologie Moléculaire et Cellulaire du Développement, 9 quai St Bernard, 75252 Paris Cedex 05, France. pascal.coumailleau@snv.jussieu.fr
authors.forename: Pascal
authors.initials: P
authors.lastname: Coumailleau
authors.forename: Karine
authors.initials: K
authors.lastname: Bollérot
authors.forename: Céline
authors.initials: C
authors.lastname: Lecomte
authors.forename: Nicole
authors.initials: N
authors.lastname: Angelier
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D051792:Basic Helix-Loop-Helix Proteins; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins; D019281:Dimerization; D004330:Drosophila / Q000235:genetics; D029721:Drosophila Proteins; D049452:Green Fluorescent Proteins; D018257:Helix-Loop-Helix Motifs / Q000235:genetics*; D019476:Insect Proteins / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008954:Models, Biological; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus / Q000196:embryology*; D029867:Xenopus Proteins
chemical_list: D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D051792:Basic Helix-Loop-Helix Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D049452:Green Fluorescent Proteins; D019476:Insect Proteins; D008164:Luminescent Proteins; D016271:Proto-Oncogene Proteins c-myc; D018336:Receptors, Aryl Hydrocarbon; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; C420993:SIM1 protein, Xenopus; C109766:tgo protein, Drosophila