title: A novel conserved nuclear localization signal is recognized by a group of yeast importins.
abstract: Nucleo-cytoplasmic transport of proteins is mostly mediated by specific interaction between transport receptors of the importin beta family and signal sequences present in their cargo. While several signal sequences, in particular the classical nuclear localization signal (NLS) recognized by the heterodimeric importin alpha/beta complex are well known, the signals recognized by other importin beta-like transport receptors remain to be characterized in detail. Here we present the systematic analysis of the nuclear import of Saccharomyces cerevisiae Asr1p, a nonessential alcohol-responsive Ring/PHD finger protein that shuttles between nucleus and cytoplasm but accumulates in the nucleus upon alcohol stress. Nuclear import of Asr1p is constitutive and mediated by its C-terminal domain. A short sequence comprising residues 243-280 is sufficient and necessary for active targeting to the nucleus. Moreover, the nuclear import signal is conserved from yeast to mammals. In vitro, the nuclear localization signal of Asr1p directly interacts with the importins Kap114p, Kap95p, Pse1p, Kap123p, or Kap104p, interactions that are sensitive to the presence of RanGTP. In vivo, these importins cooperate in nuclear import. Interestingly, the same importins mediate nuclear transport of histone H2A. Based on mutational analysis and sequence comparison with a region mediating nuclear import of histone H2A, we identified a novel type of NLS with the consensus sequence R/KxxL(x)(n)V/YxxV/IxK/RxxxK/R that is recognized by five yeast importins and connects them into a highly efficient network for nuclear import of proteins.
authors.affiliation: Universität des Saarlandes, Medizinische Biochemie und Molekularbiologie, Gebaüde 61.4, D-66421 Homburg/Saar, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Fries
authors.forename: Christian
authors.initials: C
authors.lastname: Betz
authors.forename: Kai
authors.initials: K
authors.lastname: Sohn
authors.forename: Stefanie
authors.initials: S
authors.lastname: Caesar
authors.forename: Gabriel
authors.initials: G
authors.lastname: Schlenstedt
authors.forename: Susanne M
authors.initials: SM
authors.lastname: Bailer
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000235:genetics; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D064211:Connectin; D000431:Ethanol / Q000494:pharmacology; D006657:Histones / Q000235:genetics / Q000378:metabolism; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism*; D008322:Mammals / Q000235:genetics / Q000378:metabolism; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D019913:Nuclear Localization Signals / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D012997:Solvents / Q000494:pharmacology; D013312:Stress, Physiological / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C488254:Asr1 protein, S cerevisiae; D002352:Carrier Proteins; D064211:Connectin; D006657:Histones; D028884:Karyopherins; D009124:Muscle Proteins; D019913:Nuclear Localization Signals; D029701:Saccharomyces cerevisiae Proteins; D012997:Solvents; D000431:Ethanol; D011494:Protein Kinases