title: Atypical CRM1-dependent nuclear export signal mediates regulation of hypoxia-inducible factor-1alpha by MAPK.
abstract: Hypoxia-inducible factor 1 (HIF-1) is the key transcriptional activator of hypoxia-inducible genes and an important anti-cancer target. Its regulated subunit, HIF-1alpha, is controlled by oxygen levels and major signaling pathways. We reported previously that phosphorylation of Ser(641/643) by p42/44 MAPK is essential for HIF-1alpha nuclear accumulation and activity. We now show that a fragment of HIF-1alpha (amino acids 616-658), termed MAPK target domain, contains a nuclear export signal (NES), which has atypical hydrophobic residue spacing. Localization, reporter gene, and co-immunoprecipitation assays demonstrate that the identified NES interacts with CRM1 in a phosphorylation-sensitive manner. Furthermore, disruption of the NES (I637A/L638A/I639A) restores nuclear localization and activity of nonphosphorylated HIF-1alpha and renders it largely resistant to inhibition of MAPK, an effect reproduced by a phosphomimetic mutation (S641E). As these data predict, overexpression of wild-type or mutant (S641A/S643A) MAPK target domain in HeLa cells modulates the activity and subcellular distribution of endogenous HIF-1alpha. We suggest that control of HIF-1alpha nuclear transport represents an important MAPK-dependent regulatory mechanism.
authors.affiliation: Laboratory of Biochemistry, Mezourlo, 41110 Larissa, Greece; Institute of Biomedical Research and Technology (BIOMED), Mezourlo, 41110 Larissa, Greece.
authors.forename: Ilias
authors.initials: I
authors.lastname: Mylonis
authors.affiliation: Laboratory of Biochemistry, Mezourlo, 41110 Larissa, Greece; Institute of Biomedical Research and Technology (BIOMED), Mezourlo, 41110 Larissa, Greece.
authors.forename: Georgia
authors.initials: G
authors.lastname: Chachami
authors.affiliation: Institute of Biomedical Research and Technology (BIOMED), Mezourlo, 41110 Larissa, Greece; Laboratory of Physiology, Department of Medicine, University of Thessaly, Mezourlo, 41110 Larissa, Greece.
authors.forename: Efrosyni
authors.initials: E
authors.lastname: Paraskeva
authors.affiliation: Laboratory of Biochemistry, Mezourlo, 41110 Larissa, Greece; Institute of Biomedical Research and Technology (BIOMED), Mezourlo, 41110 Larissa, Greece. Electronic address: simos@med.uth.gr.
authors.forename: George
authors.initials: G
authors.lastname: Simos
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D049790:Nuclear Export Signals / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D000097606:Exportin 1 Protein
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D028884:Karyopherins; D019950:Mitogen-Activated Protein Kinase 1; D049790:Nuclear Export Signals; D018160:Receptors, Cytoplasmic and Nuclear; D000097606:Exportin 1 Protein; C497442:HIF1A protein, human