title: Structural basis for the nuclear import of the human androgen receptor.
abstract: Ligand-dependent nuclear import is crucial for the function of the androgen receptor (AR) in both health and disease. The unliganded AR is retained in the cytoplasm but, on binding 5alpha-dihydrotestosterone, it translocates into the nucleus and alters transcription of its target genes. Nuclear import of AR is mediated by the nuclear import factor importin-alpha, which functions as a receptor that recognises and binds to specific nuclear localisation signal (NLS) motifs on cargo proteins. We show here that the AR binds to importin-alpha directly, albeit more weakly than the NLS of SV40 or nucleoplasmin. We describe the 2.6-angstroms-resolution crystal structure of the importin-alpha-AR-NLS complex, and show that the AR binds to the major NLS-binding site on importin-alpha in a manner different from most other NLSs. Finally, we have shown that pathological mutations within the NLS of AR that are associated with prostate cancer and androgen-insensitivity syndrome reduce the binding affinity to importin-alpha and, subsequently, retard nuclear import; surprisingly, however, the transcriptional activity of these mutants varies widely. Thus, in addition to its function in the nuclear import of AR, the NLS in the hinge region of AR has a separate, quite distinct role on transactivation, which becomes apparent once nuclear import has been achieved.
authors.affiliation: Uro-Oncology Research Group, Cancer Research UK Cambridge Research Institute, Robinson Way, Cambridge, CB2 0RE, UK.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Cutress
authors.forename: Hayley C
authors.initials: HC
authors.lastname: Whitaker
authors.forename: Ian G
authors.initials: IG
authors.lastname: Mills
authors.forename: Murray
authors.initials: M
authors.lastname: Stewart
authors.forename: David E
authors.initials: DE
authors.lastname: Neal
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D018360:Crystallography, X-Ray; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011944:Receptors, Androgen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D028901:alpha Karyopherins / Q000378:metabolism
chemical_list: C410798:AR protein, human; D019913:Nuclear Localization Signals; D011944:Receptors, Androgen; D028901:alpha Karyopherins