title: Immediate early gene X1 (IEX-1) is organized in subnuclear structures and partially co-localizes with promyelocytic leukemia protein in HeLa cells.
abstract: Immediate early gene X1 (IEX-1) represents a stress response gene involved in growth control and modulation of apoptosis. Here, we report a detailed analysis of IEX-1 with respect to its intracellular localization. By means of confocal laser scanning microscopy, a green fluorescent protein-IEX-1 fusion protein transfected into HeLa cells, as well as endogenous IEX-1, could be detected in distinct subnuclear structures. This particular subnuclear localization of IEX-1 was not observed with a green fluorescent protein-IEX-1 fusion protein lacking a putative nuclear localization sequence, along with a decreased effect on apoptosis. Double immunofluorescence staining revealed a partial co-localization of endogenous promyelocytic leukemia protein (PML) and IEX-1 in these subnuclear structures. Nuclear localization of IEX-1 is also enhanced upon treatment of cells with leptomycin B, an inhibitor of the nuclear exporter CRM1. These observations indicate that IEX-1 is specifically shuttled to and from the nucleus. Overexpression experiments using PML isoforms III and IV revealed distinct intranuclear interaction of IEX-1 and PML. Coprecipitation experiments showed physical interaction between IEX-1 and PML. The close structural relation of IEX-1-containing nuclear subdomains and PML nuclear bodies suggests a function of IEX-1 related to the multiple functions of these unique subnuclear regions, particularly during stress response and growth control.
authors.affiliation: Laboratory of Molecular Gastroenterology and Hepatology, First Department of Medicine, Christian-Albrechts-University of Kiel, Schittenhelmstrasse 12, D-24105 Kiel, Germany.
authors.forename: Marie-Luise
authors.initials: ML
authors.lastname: Kruse
authors.forename: Alexander
authors.initials: A
authors.lastname: Arlt
authors.forename: Alexander
authors.initials: A
authors.lastname: Sieke
authors.forename: Frauke
authors.initials: F
authors.lastname: Grohmann
authors.forename: Maike
authors.initials: M
authors.lastname: Grossmann
authors.forename: Jörg
authors.initials: J
authors.lastname: Minkenberg
authors.forename: Ulrich R
authors.initials: UR
authors.lastname: Fölsch
authors.forename: Heiner
authors.initials: H
authors.lastname: Schäfer
mesh_terms: D021581:Active Transport, Cell Nucleus; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D017781:Genes, Immediate-Early; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics* / Q000502:physiology*; D047468:Immunoprecipitation; D008565:Membrane Proteins; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D000071156:Promyelocytic Leukemia Protein; D011485:Protein Binding; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000378:metabolism / Q000502:physiology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D005231:Fatty Acids, Unsaturated; C099815:IER3 protein, human; D017874:Immediate-Early Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; D049452:Green Fluorescent Proteins; D005982:Glutathione Transferase; D020169:Caspases; C038753:leptomycin B