The RING finger protein SNURF modulates nuclear trafficking of the androgen receptor.
The androgen receptor (AR) is a transcription factor that mediates androgen action. We have used the green fluorescent protein (GFP) technique to investigate dynamics of nuclear trafficking of human AR in living cells. In the absence of ligand, the GFP-AR fusion protein is distributed between cytoplasm and nuclei. Androgen exposure leads to a rapid and complete import of GFP-AR to nuclei of CV-1 cells (>=90% nuclear in 30 minutes), whereas a pure antiandrogen, Casodex, elicits a slower (<40% nuclear in 30 minutes) and incomplete transfer. Unliganded ARs with mutations in the basic amino acids of the bipartite nuclear localization signal (NLS) within the second zinc finger and the hinge region are predominantly cytoplasmic and their androgen-dependent nuclear import is severely compromised ((3/4)20% nuclear in 30 minutes). Interestingly, substitutions of the Leu residues flanking the bipartite NLS lead to inefficient nuclear transfer in response to androgen ((3/4)20% nuclear in 30 minutes). The ligand-binding domain of AR, which represses bipartite NLS activity, contains an agonist-specific NLS. The small nuclear RING finger protein SNURF, which interacts with AR through a region overlapping with the bipartite NLS, facilitates AR import to nuclei and retards its export on hormone withdrawal. More AR is associated with the nuclear matrix in the presence than absence of coexpressed SNURF. We suggest that the SNURF-mediated tethering of AR in nuclei represents a novel mechanism for activating steroid receptor functions.
Poukka
H
H
Department of Physiology, Institute of Biomedicine and Department of Clinical Chemistry, University of Helsinki, FIN-00014 Helsinki, Finland.
Karvonen
U
U
Yoshikawa
N
N
Tanaka
H
H
Palvimo
J J
JJ
Jänne
O A
OA
D000595:Amino Acid Sequence; D059002:Androgen Receptor Antagonists; D000728:Androgens / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006801:Humans; D007202:Indicators and Reagents / Q000494:pharmacology; D007930:Leucine / Q000235:genetics; D008164:Luminescent Proteins / Q000235:genetics / Q000494:pharmacology; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000235:genetics; D015530:Nuclear Matrix / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D017354:Point Mutation; D011944:Receptors, Androgen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017384:Sequence Deletion; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection; D016335:Zinc Fingers / Q000235:genetics
D059002:Androgen Receptor Antagonists; D000728:Androgens; D007202:Indicators and Reagents; D008164:Luminescent Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; C114070:RNF4 protein, human; D011944:Receptors, Androgen; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; D007930:Leucine