Separable features of the ligand-binding domain determine the differential subcellular localization and ligand-binding specificity of glucocorticoid receptor and progesterone receptor.
Glucocorticoid receptor (GR) and progesterone receptor (PR) are closely related members of the steroid receptor family of transcription factors. The two receptors share a similar domain structure, substantial sequence identity, DNA binding specificity, and the ability to induce many of the same genes. Despite these similarities, the unliganded GR is localized predominantly in the cytoplasm, while unliganded PR is found predominantly in the nucleus. By expressing green fluorescent protein (GFP)-tagged receptors and assessing subcellular localization in living cells by confocal microscopy, we have investigated the structural basis for the differential localization of GR and PR. By constructing a series of GFP-tagged receptor chimeras between GR and PR, we have shown that multiple features in the N-terminal half of the ligand-binding domain (LBD) are the critical determinants that mandate the differential localization of GR and PR. Replacement of residues encompassing helices 1-5 of GR with those of PR yields a receptor that is nuclear. However, this domain is unable to mediate nuclear import by itself when removed from the context of the receptor. The chimeric receptors also indicate that regions encompassing helices 6 and 7 are key determinants of the ligand binding potential and the transactivation potential of receptors. Thus, the determinants specifying localization of hormone-free receptors are separable from those governing ligand binding character.
Wan
Y
Y
Department of Pathology and Program in Molecular Biology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
Coxe
K K
KK
Thackray
V G
VG
Housley
P R
PR
Nordeen
S K
SK
D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry*; D003593:Cytoplasm / Q000737:chemistry*; D004247:DNA / Q000378:metabolism; D015870:Gene Expression; D049452:Green Fluorescent Proteins; D008024:Ligands; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D018613:Microscopy, Confocal; D011965:Receptors, Glucocorticoid / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D011980:Receptors, Progesterone / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D015533:Transcriptional Activation; D014162:Transfection
D008024:Ligands; D008164:Luminescent Proteins; D011965:Receptors, Glucocorticoid; D011980:Receptors, Progesterone; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D004247:DNA