title: Differential sub-nuclear distribution of hypoxia-inducible factors (HIF)-1 and -2 alpha impacts on their stability and mobility.
abstract: Cellular adaptation to hypoxia occurs via a complex programme of gene expression mediated by the hypoxia-inducible factor (HIF). The oxygen labile alpha subunits, HIF-1α/-2α, form a heterodimeric transcription factor with HIF-1β and modulate gene expression. HIF-1α and HIF-2α possess similar domain structure and bind to the same consensus sequence. However, they have different oxygen-dependent stability and activate distinct genes. To better understand these differences, we used fluorescent microscopy to determine precise localization and dynamics. We observed a homogeneous distribution of HIF-1α in the nucleus, while HIF-2α localized into speckles. We demonstrated that the number, size and mobility of HIF-2α speckles were independent of cellular oxygenation and that HIF-2α molecules were capable of exchanging between the speckles and nucleoplasm in an oxygen-independent manner. The concentration of HIF-2α into speckles may explain its increased stability compared with HIF-1α and its slower mobility may offer a mechanism for gene specificity.
authors.affiliation: Department of Biochemistry, Centre for Cell Imaging, University of Liverpool, Institute of Integrated Biology, Liverpool L69 7ZB, UK.
authors.forename: S E
authors.initials: SE
authors.lastname: Taylor
authors.affiliation: Department of Biochemistry, Centre for Cell Imaging, University of Liverpool, Institute of Integrated Biology, Liverpool L69 7ZB, UK.
authors.forename: J
authors.initials: J
authors.lastname: Bagnall
authors.affiliation: Department of Biochemistry, Centre for Cell Imaging, University of Liverpool, Institute of Integrated Biology, Liverpool L69 7ZB, UK.
authors.forename: D
authors.initials: D
authors.lastname: Mason
authors.affiliation: Department of Biochemistry, Centre for Cell Imaging, University of Liverpool, Institute of Integrated Biology, Liverpool L69 7ZB, UK.
authors.forename: R
authors.identifier: http://orcid.org/0000-0001-5728-0531
authors.initials: R
authors.lastname: Levy
authors.affiliation: Department of Biochemistry, Centre for Cell Imaging, University of Liverpool, Institute of Integrated Biology, Liverpool L69 7ZB, UK.
authors.forename: D G
authors.identifier: http://orcid.org/0000-0003-4875-4293
authors.initials: DG
authors.lastname: Fernig
authors.affiliation: Department of Biochemistry, Centre for Cell Imaging, University of Liverpool, Institute of Integrated Biology, Liverpool L69 7ZB, UK violaine@liverpool.ac.uk.
authors.forename: V
authors.identifier: http://orcid.org/0000-0001-6384-8381
authors.initials: V
authors.lastname: See
keywords: HIF-2α; confocal microscopy; fluorescence recovery after photo-bleaching; hypoxia; hypoxia-inducible factor; nuclear speckles