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8 results on '"Nathalie Theis-Febvre"'

1. Phosphorylation of CDC25B by Aurora-A at the centrosome contributes to the G2–M transition

Author

Bernard Monsarrat, Gladys Mirey, Nathalie Theis-Febvre, Estelle Schmitt, Stéphanie Dutertre, Carine Froment, Jean-Pierre Bouché, Martine Cazales, Christine Dozier, Bernard Ducommun, Muriel Quaranta, Valerie Trabut, Claude Prigent, Génétique et Développement, Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-IFR97-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération (LBCMCP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre de Biologie Intégrative (CBI), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Ducommun, Bernard, Université de Rennes (UR)-IFR97-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre de Biologie Intégrative (CBI), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Time Factors, Cell Cycle Proteins, Centrosome cycle, Xenopus Proteins, MESH: Microinjections, Aurora-A, MESH: Centrosome, MESH: Antibodies, Monoclonal, 0302 clinical medicine, MESH: cdc25 Phosphatases, Aurora Kinases, Serine, Phosphorylation, MESH: Xenopus Proteins, 0303 health sciences, Kinase, Antibodies, Monoclonal, Cell biology, 030220 oncology & carcinogenesis, MESH: Cell Division, RNA Interference, biological phenomena, cell phenomena, and immunity, Cell Division, Autre (Sciences du Vivant), CDC25B phosphatase, G2 Phase, Microinjections, MESH: RNA Interference, centrosome, mitosis, [SDV.BC]Life Sciences [q-bio]/Cellular Biology, macromolecular substances, Protein Serine-Threonine Kinases, Biology, MESH: Protein-Serine-Threonine Kinases, Antibodies, 03 medical and health sciences, MESH: Cell Cycle Proteins, Cyclin-dependent kinase, Humans, cdc25 Phosphatases, MESH: Serine, Protein kinase A, [SDV.BC] Life Sciences [q-bio]/Cellular Biology, MESH: Protein Kinases, Mitosis, 030304 developmental biology, Centrosome, MESH: Humans, MESH: Phosphorylation, MESH: Antibodies, MESH: Time Factors, G1/S transition, Cell Biology, MESH: Hela Cells, MESH: G2 Phase, enzymes and coenzymes (carbohydrates), biology.protein, Cancer research, Protein Kinases, HeLa Cells
Abstract

Aurora-A protein kinase, which is the product of an oncogene, is required for the assembly of a functional mitotic apparatus and the regulation of cell ploidy. Overexpression of Aurora-A in tumour cells has been correlated with cancer susceptibility and poor prognosis. Aurora-A activity is required for the recruitment of CDK1-cyclin B1 to the centrosome prior to its activation and the commitment of the cell to mitosis. In this report, we demonstrate that the CDC25B phosphatase, an activator of cyclin dependent kinases at mitosis, is phosphorylated both in vitro and in vivo by Aurora-A on serine 353 and that this phosphorylated form of CDC25B is located at the centrosome during mitosis. Knockdown experiments by RNAi confirm that the centrosome phosphorylation of CDC25B on S353 depends on Aurora-A kinase. Microinjection of antibodies against phosphorylated S353 results in a mitotic delay whilst overexpression of a S353 phosphomimetic mutant enhances the mitotic inducing effect of CDC25B. Our results demonstrate that Aurora-A phosphorylates CDC25B in vivo at the centrosome during mitosis. This phosphorylation might locally participate in the control of the onset of mitosis. These findings re-emphasise the role of the centrosome as a functional integrator of the pathways contributing to the triggering of mitosis.

Published
2004
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2. Protein kinase CK2 regulates CDC25B phosphatase activity

Author

Claude Cochet, Martine Cazales, Bernard Ducommun, Nathalie Theis-Febvre, Véronique Baldin, Odile Filhol, Bernard Monsarrat, Carine Froment, Biologie du Cancer et de l'Infection (BCI ), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut de pharmacologie et de biologie structurale (IPBS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération (LBCMCP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre de Biologie Intégrative (CBI), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Transduction du signal : signalisation calcium, phosphorylation et inflammation, Université Joseph Fourier - Grenoble 1 (UJF)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre de recherches de biochimie macromoléculaire (CRBM), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-IFR122-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre de Biologie Intégrative (CBI), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Cancer Research, Cdc25, Molecular Sequence Data, Cell Cycle Proteins, [SDV.BC.BC]Life Sciences [q-bio]/Cellular Biology/Subcellular Processes [q-bio.SC], Protein tyrosine phosphatase, Protein Serine-Threonine Kinases, Spodoptera, Epitopes, 03 medical and health sciences, 0302 clinical medicine, Cyclin-dependent kinase, Serine, Genetics, Animals, Humans, cdc25 Phosphatases, Protein phosphorylation, Amino Acid Sequence, c-Raf, Phosphorylation, Casein Kinase II, Protein kinase A, Molecular Biology, Cells, Cultured, ComputingMilieux_MISCELLANEOUS, 030304 developmental biology, 0303 health sciences, Cyclin-dependent kinase 1, biology, fungi, Peptide Fragments, Recombinant Proteins, Protein Structure, Tertiary, Up-Regulation, Cell biology, Biochemistry, 030220 oncology & carcinogenesis, biology.protein, Protein Kinases, Protein Processing, Post-Translational
Abstract

Human dual-specificity phosphatases CDC25 (A, B and C) play an important role in the control of cell cycle progression by activating the cyclin-dependent kinases (CDKs). Regulation of these phosphatases during the cell cycle involves post-translational modifications such as phosphorylation and protein-protein interactions. Given the suspected involvement of the protein kinase CK2 at the G2/M transition, we have investigated its effects on the CDC25B phosphatase. We show that in vitro CK2 phosphorylates CDC25B, but not CDC25C. Mass spectrometry analysis demonstrates that at least two serine residues, Ser-186 and Ser-187, are phosphorylated in vivo. We also report that CDC25B interacts with CK2, and this interaction, mediated by the CK2beta regulatory subunit, involves domains that are located within the first 55 amino acids of CK2beta and between amino acids 122 and 200 on CDC25B. This association was confirmed in vivo, in Sf9 insect cells and in U(2)OS human cells expressing an HA epitope-tagged CDC25B. Finally, we demonstrate that phosphorylation of CDC25B by protein kinase CK2 increases the catalytic activity of the phosphatase in vitro as well as in vivo. We discuss the possibility that CDC25B phosphorylation by CK2 could play a role in the regulation of the activity of CDC25B as a starter of mitosis.

Published
2003
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3. Protein kinase CK2 and cell polarity

Author

Véronique Martel, Claude Cochet, Odile Filhol, Alexandre Deshiere, Nathalie Theis-Febvre, Transduction du signal : signalisation calcium, phosphorylation et inflammation, Université Joseph Fourier - Grenoble 1 (UJF)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de la Santé et de la Recherche Médicale (INSERM), and Cochet, Claude

Subjects
Clinical Biochemistry, MESH: Casein Kinase II, MESH: Dogs, Mice, Cell polarity, MESH: Protein Kinase Inhibitors, MESH: Animals, Casein Kinase II, Epithelial polarity, 0303 health sciences, biology, 030302 biochemistry & molecular biology, Cell Polarity, General Medicine, MESH: Protein Subunits, Cell biology, Protein Transport, Phenotype, MESH: Epithelial Cells, embryonic structures, MESH: Cell Polarity, Subcellular Fractions, MESH: Protein Transport, animal structures, [SDV.CAN]Life Sciences [q-bio]/Cancer, MESH: Phenotype, Cell Line, 03 medical and health sciences, Dogs, [SDV.CAN] Life Sciences [q-bio]/Cancer, Animals, Humans, Integrin-linked kinase, Protein kinase A, Molecular Biology, Protein kinase B, Protein Kinase Inhibitors, MESH: Mice, 030304 developmental biology, MESH: Humans, Cyclin-dependent kinase 5, Cyclin-dependent kinase 2, Cell Membrane, fungi, Cyclin-dependent kinase 3, Epithelial Cells, Cell Biology, MESH: Cell Line, Protein Subunits, MESH: Subcellular Fractions, biology.protein, MESH: Cell Membrane
Abstract

International audience; There is increasing evidence that protein kinase CK2 is involved, among a wide variety of cellular processes, in the maintenance of mammalian cell morphology and cell polarity. Here, we show that in epithelial cells, a fraction of CK2 is associated to the plasma membrane and that this localization is controlled by cell-matrix interactions. In addition, inhibition of CK2 activity in mammary epithelial cells (MCF10A), using either the specific CK2 inhibitor TBB or siRNA-mediated CK2beta knockdown, induced differential phenotypes revealing an important role of this enzyme in epithelial cell morphology.

Published
2008
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4. Highlighting protein kinase CK2 movement in living cells

Author

Catherine Souchier, Béatrice Laudet, Nathalie Theis-Febvre, Véronique Martel, Didier Grunwald, Claude Cochet, Odile Filhol, Département Réponse et Dynamique Cellulaires, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de la Santé et de la Recherche Médicale (INSERM), Biologie moléculaire et cellulaire de la différenciation, Université Joseph Fourier - Grenoble 1 (UJF)-Institut Albert Bonniot-Institut National de la Santé et de la Recherche Médicale (INSERM), ANTE-INSERM U836, équipe 4, Muscles et pathologies, Canaux Ioniques et Signalisation, Université Joseph Fourier - Grenoble 1 (UJF)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Joseph Fourier - Grenoble 1 (UJF)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de la Santé et de la Recherche Médicale (INSERM), and Cochet, Claude

Subjects
MESH: Cell Nucleus, Fluorescence-lifetime imaging microscopy, MESH: Protein Transport, MESH: 3T3 Cells, Recombinant Fusion Proteins, Protein subunit, Green Fluorescent Proteins, Clinical Biochemistry, Active Transport, Cell Nucleus, Fluorescence correlation spectroscopy, MESH: Casein Kinase II, MESH: Microscopy, Fluorescence, [SDV.CAN]Life Sciences [q-bio]/Cancer, MESH: Active Transport, Cell Nucleus, Biology, Mice, 03 medical and health sciences, Bimolecular fluorescence complementation, 0302 clinical medicine, MESH: Green Fluorescent Proteins, [SDV.CAN] Life Sciences [q-bio]/Cancer, MESH: Recombinant Fusion Proteins, Animals, MESH: Animals, Casein Kinase II, Molecular Biology, MESH: Mice, 030304 developmental biology, Cell Nucleus, 0303 health sciences, fungi, 3T3 Cells, Cell Biology, General Medicine, MESH: Protein Subunits, Cell biology, Protein Subunits, Protein Transport, Förster resonance energy transfer, Microscopy, Fluorescence, Cytoplasm, 030220 oncology & carcinogenesis, Nuclear transport, Nuclear localization sequence
Abstract

International audience; Protein kinase CK2 has traditionally been described as a stable heterotetrameric complex (alpha2beta2) but new approaches that effectively capture the dynamic behavior of proteins, are bringing a new picture of this complex into focus. To track the spatio-temporal dynamics of CK2 in living cells, we fused its catalytic alpha and regulatory beta subunits with GFP and analog proteins. Beside the mostly nuclear localization of both subunits, and the identification of specific domains on each subunit that triggers their localization, the most significant finding was that the association of both CK2 subunits in a stable tetrameric holoenzyme eliminates their nuclear import (Mol Cell Biol 23: 975-987, 2003). Molecular movements of both subunits in the cytoplasm and in the nucleus were analyzed using different new and updated fluorescence imaging methods such as: fluorescence recovery after photo bleaching (FRAP), fluorescence loss in photo bleaching (FLIP), fluorescence correlation spectroscopy (FCS), and photoactivation using a biphoton microscope. These fluorescence-imaging techniques provide unprecedented ways to visualize and quantify the mobility of each individual CK2 subunit with high spatial and temporal resolution. Visualization of CK2 heterotetrameric complex formation could also be recorded using the fluorescence resonance energy transfer (FRET) technique. FRET imaging revealed that the assembling of this molecular complex can take place both in the cytoplasmic and nuclear compartments. The spatio-temporal organization of individual CK2 subunits and their dynamic behavior remain now to be correlated with the functioning of this kinase in the complex environment of the cell.

Published
2005

5. PKB/Akt phosphorylates the CDC25B phosphatase and regulates its intracellular localisation

Author

Véronique Baldin, Bernard Ducommun, Carine Froment, Martine Cazales, Clarisse Benne, Nathalie Theis-Febvre, Odile Burlet-Schiltz, Centre de recherches de biochimie macromoléculaire (CRBM), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-IFR122-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération (LBCMCP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre de Biologie Intégrative (CBI), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de pharmacologie et de biologie structurale (IPBS), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées

Subjects
Cytoplasm, Genetic Vectors, Nuclear Localization Signals, AKT1, Receptors, Cytoplasmic and Nuclear, Cell Cycle Proteins, [SDV.BC.BC]Life Sciences [q-bio]/Cellular Biology/Subcellular Processes [q-bio.SC], Karyopherins, Protein Serine-Threonine Kinases, mTORC2, Cell Line, 3-Phosphoinositide-Dependent Protein Kinases, 03 medical and health sciences, 0302 clinical medicine, Cyclin-dependent kinase, Proto-Oncogene Proteins, Animals, Humans, Point Mutation, cdc25 Phosphatases, Protein kinase A, Protein kinase B, ComputingMilieux_MISCELLANEOUS, 030304 developmental biology, Cell Nucleus, 0303 health sciences, biology, Kinase, Akt/PKB signaling pathway, Cell Biology, General Medicine, Hydrogen Peroxide, Recombinant Proteins, Cell biology, Oxidative Stress, Protein Transport, 030220 oncology & carcinogenesis, biology.protein, Cancer research, Phosphorylation, Proto-Oncogene Proteins c-akt, HeLa Cells, Plasmids
Abstract

Regulation of the intracellular localisation of its actors is one of the key mechanisms underlying cell cycle control. CDC25 phosphatases are activators of Cyclin-Dependent Kinases (CDK) that undergo nucleo-cytoplasmic shuttling during the cell cycle and in response to checkpoint activation. Here we report that the protein kinase PKB/Akt phosphorylates CDC25B on serine 353, resulting in a nuclear export-dependent cytoplasmic accumulation of the phosphatase. Oxidative stress activates PKB/Akt and reproduces the effect on CDC25B phosphorylation and localisation. However, inhibition of PKB/Akt activity only partially reverted the effect of oxidative stress on CDC25B localisation and mutation of serine 353 abolishes phosphorylation but only delays nuclear exclusion. These results indicate that additional mechanisms are also involved in preventing nuclear import of CDC25B. Our findings identify CDC25B as a target of PKB/Akt and provide new insight into the regulation of its localisation in response to stress-activated signalling pathways.

Published
2003
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6. Protein kinase CK2 and cell polarity.

Author

Alexandre Deshière, Nathalie Theis-Febvre, Véronique Martel, Claude Cochet, and Odile Filhol

Abstract

Abstract  There is increasing evidence that protein kinase CK2 is involved, among a wide variety of cellular processes, in the maintenance of mammalian cell morphology and cell polarity. Here, we show that in epithelial cells, a fraction of CK2 is associated to the plasma membrane and that this localization is controlled by cell–matrix interactions. In addition, inhibition of CK2 activity in mammary epithelial cells (MCF10A), using either the specific CK2 inhibitor TBB or siRNA-mediated CK2β knockdown, induced differential phenotypes revealing an important role of this enzyme in epithelial cell morphology. [ABSTRACT FROM AUTHOR]

Published
2008

7. Highlighting protein kinase CK2 movement in living cells.

Author

Nathalie Theis-Febvre, Véronique Martel, Béatrice Laudet, Catherine Souchier, Didier Grunwald, Claude Cochet, and Odile Filhol

Abstract

Abstract Protein kinase CK2 has traditionally been described as a stable heterotetrameric complex (a < eqid1 > ß2) but new approaches that effectively capture the dynamic behavior of proteins, are bringing a new picture of this complex into focus. To track the spatio-temporal dynamics of CK2 in living cells, we fused its catalytic a and regulatory ß subunits with GFP and analog proteins. Beside the mostly nuclear localization of both subunits, and the identification of specific domains on each subunit that triggers their localization, the most significant finding was that the association of both CK2 subunits in a stable tetrameric holoenzyme eliminates their nuclear import (Mol Cell Biol {23}: 975–987, 2003). Molecular movements of both subunits in the cytoplasm and in the nucleus were analyzed using different new and updated fluorescence imaging methods such as: fluorescence recovery after photo bleaching (FRAP), fluorescence loss in photo bleaching (FLIP), fluorescence correlation spectroscopy (FCS), and photoactivation using a biphoton microscope. These fluorescence-imaging techniques provide unprecedented ways to visualize and quantify the mobility of each individual CK2 subunit with high spatial and temporal resolution. Visualization of CK2 heterotetrameric complex formation could also be recorded using the fluorescence resonance energy transfer (FRET) technique. FRET imaging revealed that the assembling of this molecular complex can take place both in the cytoplasmic and nuclear compartments. The spatio–temporal organization of individual CK2 subunits and their dynamic behavior remain now to be correlated with the functioning of this kinase in the complex environment of the cell. [ABSTRACT FROM AUTHOR]

Published
2005

8. Regulation of CDC25B phosphatases subcellular localization

Author

Nathalie Theis-Febvre, Brian Gabrielli, Véronique Baldin, Bernard Ducommun, Alistair R. R. Forrest, Minoru Yashida, Noélie Davezac, Centre de biologie du développement (CBD), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre de Biologie Intégrative (CBI), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre de recherches de biochimie macromoléculaire (CRBM), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-IFR122-Centre National de la Recherche Scientifique (CNRS), The University of Western Australia (UWA), Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération (LBCMCP), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre de Biologie Intégrative (CBI)

Subjects
Cytoplasm, Cancer Research, Tyrosine 3-Monooxygenase, Molecular Sequence Data, Nuclear Localization Signals, Cell Cycle Proteins, [SDV.BC.BC]Life Sciences [q-bio]/Cellular Biology/Subcellular Processes [q-bio.SC], Plasma protein binding, Cyclin B, Biology, Models, Biological, 03 medical and health sciences, chemistry.chemical_compound, 0302 clinical medicine, Dual-specificity phosphatase, Genetics, Humans, cdc25 Phosphatases, Amino Acid Sequence, Nuclear export signal, Molecular Biology, Peptide sequence, ComputingMilieux_MISCELLANEOUS, 030304 developmental biology, Cell Nucleus, 0303 health sciences, Proteins, Biological Transport, Leptomycin, Subcellular localization, Cell Compartmentation, Cell biology, 14-3-3 Proteins, chemistry, Biochemistry, 030220 oncology & carcinogenesis, Mutation, biology.protein, Nuclear localization sequence, HeLa Cells, Protein Binding
Abstract

The CDC25B dual specificity phosphatase is involved in the control of the G2/M transition of the cell cycle. Subcellular localization might represent an important aspect of the regulation of its activity. We have examined in transiently transfected asynchronous HeLa cells the localization of HA-tagged CDC25B proteins and found that they are nuclear or cytoplasmic suggesting the existence of an active shuttling. Accordingly, localization analysis of deletion and truncation proteins indicates that CDC25B contains a putative nuclear localization signal located between residues 335 and 354. We also demonstrated that a short 58 residues deletion of the amino-terminus end of CDC25B is sufficient to retain it to the nucleus. Mutational analysis indicates that a nuclear export sequence is located between residues 28 and 40. In addition, treatment of the cells with the exportin inhibitor, Leptomycin B, has the same effect. The mutation of Ser-323, a residue that is essential for the interaction with 14-3-3 proteins, also abolishes cytoplasmic staining. The subcellular localization of CDC25B is therefore dependent on the combined effects of a nuclear localization signal, a nuclear export signal and on the interaction with 14-3-3 proteins.

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