title: Identification of a nuclear localization signal, RRMKWKK, in the homeodomain transcription factor PDX-1.
abstract: Pancreatic duodenal homeobox-containing transcription factor 1 (PDX-1) plays a crucial role in pancreas development and beta-cell gene regulation. Absence of PDX-1 leads to pancreas agenesis and its malfunction causes MODY4 diabetes mellitus. PDX-1 has been suggested to be involved in the glucose-dependent regulation of insulin gene transcription. Whereas DNA-binding and transactivation domains of PDX-1 are in the process of being characterized, protein sequences responsible for its nuclear translocation remain unknown. By combining site-directed mutagenesis of putative phosphorylation sites and nuclear localization signal (NLS) motifs with on-line monitoring of GFP-tagged PDX-1 translocation, we demonstrate that the NLS motif RRMKWKK is necessary and in conjunction with the integrity of the 'helix 3' domain of the PDX-1 homeodomain is sufficient for the nuclear import of PDX-1. Furthermore, we show that there is no glucose-dependent cytoplasmic-nuclear cycling of PDX-1.
authors.affiliation: Karolinska Institutet, Rolf Luft Center of Diabetes Research L6B:01, Department of Molecular Medicine, 171 76, Stockholm, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Moede
authors.forename: B
authors.initials: B
authors.lastname: Leibiger
authors.forename: H G
authors.initials: HG
authors.lastname: Pour
authors.forename: P
authors.initials: P
authors.lastname: Berggren
authors.forename: I B
authors.initials: IB
authors.lastname: Leibiger
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology; D018398:Homeodomain Proteins; D006801:Humans; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D015534:Trans-Activators / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D018398:Homeodomain Proteins; D011965:Receptors, Glucocorticoid; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein; D003907:Dexamethasone