Nuclear localization and export signals of the human aryl hydrocarbon receptor.
The aryl hydrocarbon receptor (Ahr) is a ligand-activated transcription factor that binds DNA in the form of a heterodimer with the Ahr nuclear translocator (hypoxia-inducible factor 1beta). We found in this study that Ahr contains both nuclear localization and export signals in the NH2-terminal region. A fusion protein composed of beta-galactosidase and full-length Ahr translocates from the cytoplasm to the nucleus in a ligand-dependent manner. However, a fusion protein lacking the PAS (Per-Ahr nuclear translocator-Sim homology) domain of the Ahr showed strong nuclear localization activity irrespective of the presence or absence of ligand. A minimum bipartite Ahr nuclear localization signal (NLS) consisting of amino acid residues 13-39 was identified by microinjection of fused proteins with glutathione S-transferase-green fluorescent protein. A NLS having mutations in bipartite basic amino acids lost nuclear translocation activity completely, which may explain the reduced binding activity to the NLS receptor, PTAC58. A 21-amino acid peptide (residues 55-75) containing the Ahr nuclear export signal is sufficient to direct nuclear export of a microinjected complex of glutathione S-transferase-Ahr-green fluorescent protein. These findings strongly suggest that Ahr act as a ligand- and signal-dependent nucleocytoplasmic shuttling protein.
Ikuta
T
T
Department of Biochemistry, Saitama Cancer Center Research Institute, 818 Komuro, Ina-machi, Kitaadachi-gun, Saitama 362, Japan.
Eguchi
H
H
Tachibana
T
T
Yoneda
Y
Y
Kawajiri
K
K
D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008024:Ligands; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014157:Transcription Factors
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008024:Ligands; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D018336:Receptors, Aryl Hydrocarbon; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors