Transport of hypoxia-inducible factor HIF-1alpha into the nucleus involves importins 4 and 7.

Abstract

Hypoxia-inducible transcription factor 1 (HIF-1) mediates the cellular response to hypoxia. HIF-1 activity is controlled via the synthesis, degradation or intracellular localization of its alpha subunit. HIF-1alpha contains a C-terminal bipartite basic NLS that interacts with importins alpha. We have recently shown that HIF-1alpha also contains an atypical hydrophobic CRM1- and phosphorylation-dependent NES and can therefore shuttle in and out of the nucleus. We now report that C-terminal NLS mutants of HIF-1alpha can still enter the nucleus when CRM1-dependent nuclear export is inhibited, indicating that HIF-1alpha contains an additional functional nuclear import signal. Using an in vitro nuclear import assay, we further show that importins 4 and 7 accomplish nuclear import of HIF-1alpha more efficiently than the classical importin alpha/beta NLS receptor. Binding assays confirmed the specific physical interaction between HIF-1alpha and importins 4 and 7. Moreover, the interaction of importin 7 with HIF-1alpha is mapped at its N-terminal part encompassing the bHLH-PAS(A) domain. By expressing functional HIF-1 in yeast, we show that Nmd5, the yeast orthologue of importin 7, is required for HIF-1alpha nuclear accumulation and activity. Taken together, our data show that shuttling of HIF-1alpha between cytoplasm and nucleus is a complex process involving several members of the nuclear transport receptor family.

• Authors: Georgia Chachami, Efrosyni Paraskeva, José-Manuel Mingot, Georgia G Braliou, Dirk Görlich, George Simos
• Journal: Biochemical and biophysical research communications (Biochem Biophys Res Commun) Vol. 390 Issue 2 Pg. 235-40 (Dec 11 2009) ISSN: 1090-2104 [Electronic] United States
• PMID: 19788888 (Publication Type: Journal Article)

Chemical References

• HIF1A protein, human
• Hypoxia-Inducible Factor 1, alpha Subunit
• IPO4 protein, human
• IPO7 protein, human
• Karyopherins
• Membrane Transport Proteins
• Receptors, Cytoplasmic and Nuclear

Topics

• Active Transport, Cell Nucleus
• Cell Nucleus (metabolism)
• Cytoplasm (metabolism)
• HeLa Cells
• Humans
• Hypoxia-Inducible Factor 1, alpha Subunit (genetics, metabolism)
• Karyopherins (genetics, metabolism)
• Membrane Transport Proteins (genetics, metabolism)
• Receptors, Cytoplasmic and Nuclear (genetics, metabolism)