1
|
Brehm M, Schenk T, Zhou X, Fanick W, Lin H, Windhorst S, Nalaskowski M, Kobras M, Shears S, Mayr G. Intracellular localization of human Ins(1,3,4,5,6)P5 2-kinase. Biochem J 2007; 408:335-45. [PMID: 17705785 PMCID: PMC2267366 DOI: 10.1042/bj20070382] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Revised: 07/18/2007] [Accepted: 08/17/2007] [Indexed: 01/05/2023]
Abstract
InsP6 is an intracellular signal with several proposed functions that is synthesized by IP5K [Ins(1,3,4,5,6)P5 2-kinase]. In the present study, we overexpressed EGFP (enhanced green fluorescent protein)-IP5K fusion proteins in NRK (normal rat kidney), COS7 and H1299 cells. The results indicate that there is spatial microheterogeneity in the intracellular localization of IP5K that could also be confirmed for the endogenous enzyme. This may facilitate changes in InsP6 levels at its sites of action. For example, overexpressed IP5K showed a structured organization within the nucleus. The kinase was preferentially localized in euchromatin and nucleoli, and co-localized with mRNA. In the cytoplasm, the overexpressed IP5K showed locally high concentrations in discrete foci. The latter were attributed to stress granules by using mRNA, PABP [poly(A)-binding protein] and TIAR (TIA-1-related protein) as markers. The incidence of stress granules, in which IP5K remained highly concentrated, was further increased by puromycin treatment. Using FRAP (fluorescence recovery after photobleaching) we established that IP5K was actively transported into the nucleus. By site-directed mutagenesis we identified a nuclear import signal and a peptide segment mediating the nuclear export of IP5K.
Collapse
Key Words
- euchromatin
- ins(1,3,4,5,6)p5 2-kinase (ip5k)
- in situ hybridization
- nuclear localization
- stress granule
- dapi, 4′,6-diamidino-2-phenylindole
- dtt, dithiothreitol
- egfp, enhanced green fluorescent protein
- fish, fluorescence in situ hybridization
- frap, fluorescence recover after photobleaching
- ipmk, inositol phosphate multikinase
- ipk, inositol phosphate kinase
- ip3k, ins(1,4,5)p3 3-kinase
- ip5k, ins(1,3,4,5,6)p5 2-kinase
- lmb, leptomycin b
- mdd-hplc, metal-dye-detection-hplc
- mrnp, messenger ribonucleoprotein
- nls, nuclear localization sequence
- nrk, normal rat kidney
- orf, open reading frame
- pabp, poly(a)-binding protein
- rnai, rna interference
- roi, region of interest
- sg, stress granule
- sirna, small-interfering rna
- tiar, tia-1-related protein
Collapse
Affiliation(s)
- Maria A. Brehm
- *NIEHS/NIH, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, U.S.A
| | - Tobias M. H. Schenk
- †Universitätsklinikum Hamburg-Eppendorf, Institut für Medizinische Biochemie und Molekularbiologie I: Zelluläre Signaltransduktion, Martinistraße 52, 20246 Hamburg, Germany
| | - Xuefei Zhou
- †Universitätsklinikum Hamburg-Eppendorf, Institut für Medizinische Biochemie und Molekularbiologie I: Zelluläre Signaltransduktion, Martinistraße 52, 20246 Hamburg, Germany
| | - Werner Fanick
- †Universitätsklinikum Hamburg-Eppendorf, Institut für Medizinische Biochemie und Molekularbiologie I: Zelluläre Signaltransduktion, Martinistraße 52, 20246 Hamburg, Germany
| | - Hongying Lin
- †Universitätsklinikum Hamburg-Eppendorf, Institut für Medizinische Biochemie und Molekularbiologie I: Zelluläre Signaltransduktion, Martinistraße 52, 20246 Hamburg, Germany
| | - Sabine Windhorst
- †Universitätsklinikum Hamburg-Eppendorf, Institut für Medizinische Biochemie und Molekularbiologie I: Zelluläre Signaltransduktion, Martinistraße 52, 20246 Hamburg, Germany
| | - Marcus M. Nalaskowski
- †Universitätsklinikum Hamburg-Eppendorf, Institut für Medizinische Biochemie und Molekularbiologie I: Zelluläre Signaltransduktion, Martinistraße 52, 20246 Hamburg, Germany
| | - Mario Kobras
- †Universitätsklinikum Hamburg-Eppendorf, Institut für Medizinische Biochemie und Molekularbiologie I: Zelluläre Signaltransduktion, Martinistraße 52, 20246 Hamburg, Germany
| | - Stephen B. Shears
- *NIEHS/NIH, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, U.S.A
| | - Georg W. Mayr
- †Universitätsklinikum Hamburg-Eppendorf, Institut für Medizinische Biochemie und Molekularbiologie I: Zelluläre Signaltransduktion, Martinistraße 52, 20246 Hamburg, Germany
| |
Collapse
|
2
|
Biondi C, Das D, Howell M, Islam A, Bikoff E, Hill C, Robertson E. Mice develop normally in the absence of Smad4 nucleocytoplasmic shuttling. Biochem J 2007; 404:235-45. [PMID: 17300215 PMCID: PMC1868808 DOI: 10.1042/bj20061830] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2006] [Revised: 02/08/2007] [Accepted: 02/14/2007] [Indexed: 01/02/2023]
Abstract
Smad4 in partnership with R-Smads (receptor-regulated Smads) activates TGF-beta (transforming growth factor-beta)-dependent signalling pathways essential for early mouse development. Smad4 null embryos die shortly after implantation due to severe defects in cell proliferation and visceral endoderm differentiation. In the basal state, Smad4 undergoes continuous shuttling between the cytoplasm and the nucleus due to the combined activities of an N-terminal NLS (nuclear localization signal) and an NES (nuclear export signal) located in its linker region. Cell culture experiments suggest that Smad4 nucleocytoplasmic shuttling plays an important role in TGF-beta signalling. In the present study we have investigated the role of Smad4 shuttling in vivo using gene targeting to engineer two independent mutations designed to eliminate Smad4 nuclear export. As predicted this results in increased levels of Smad4 in the nucleus of homozygous ES cells (embryonic stem cells) and primary keratinocytes, in the presence or absence of ligand. Neither mutation affects Smad4 expression levels nor its ability to mediate transcriptional activation in homozygous cell lines. Remarkably mouse mutants lacking the Smad4 NES develop normally. Smad4 NES mutants carrying one copy of a Smad4 null allele also fail to display developmental defects. The present study clearly demonstrates that Smad4 nucleocytoplasmic shuttling is not required for embryonic development or tissue homoeostasis in normal, healthy adult mice.
Collapse
Key Words
- embryonic
- gene targetting
- nuclear export
- nucleocytoplasmic shuttling
- smad4
- transforming growth factor-β signal
- bmp, bone morphogenetic proteins
- crm1, chromosomal region maintenance 1
- d.p.c., days post-coitum
- es cell, embryonic stem cell
- fbs, foetal bovine serum
- gdf, growth and differentiation factor
- lmb, leptomycin b
- mef, murine embryonic fibroblast
- mh domain, mad homology domain
- nes, nuclear export signal
- nls, nuclear localization signal
- rpa, ribonuclease protection assay
- r-smad, receptor-regulated smad
- snon, ski-related novel protein n
- tgf-β, transforming growth factor-β
Collapse
Affiliation(s)
- Christine A. Biondi
- *The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, U.K
| | - Debipriya Das
- †Laboratory of Developmental Signalling, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, U.K
| | - Michael Howell
- †Laboratory of Developmental Signalling, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, U.K
| | - Ayesha Islam
- *The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, U.K
| | - Elizabeth K. Bikoff
- *The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, U.K
| | - Caroline S. Hill
- †Laboratory of Developmental Signalling, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, U.K
| | - Elizabeth J. Robertson
- *The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, U.K
| |
Collapse
|
3
|
Williams B, Boyne J, Goodwin D, Roaden L, Hautbergue G, Wilson S, Whitehouse A. The prototype gamma-2 herpesvirus nucleocytoplasmic shuttling protein, ORF 57, transports viral RNA through the cellular mRNA export pathway. Biochem J 2005; 387:295-308. [PMID: 15537388 PMCID: PMC1134957 DOI: 10.1042/bj20041223] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2004] [Revised: 10/27/2004] [Accepted: 11/10/2004] [Indexed: 12/27/2022]
Abstract
HVS (herpesvirus saimiri) is the prototype gamma-2 herpesvirus. This is a subfamily of herpesviruses gaining importance since the identification of the first human gamma-2 herpesvirus, Kaposi's sarcoma-associated herpesvirus. The HVS ORF 57 (open reading frame 57) protein is a multifunctional transregulatory protein homologous with genes identified in all classes of herpesviruses. Recent work has demonstrated that ORF 57 has the ability to bind viral RNA, shuttles between the nucleus and cytoplasm and promotes the nuclear export of viral transcripts. In the present study, we show that ORF 57 shuttles between the nucleus and cytoplasm in a CRM-1 (chromosomal region maintenance 1)-independent manner. ORF 57 interacts with the mRNA export factor REF (RNA export factor) and two other components of the exon junction complex, Y14 and Magoh. The association of ORF 57 with REF stimulates recruitment of the cellular mRNA export factor TAP (Tip-associated protein), and HVS infection triggers the relocalization of REF and TAP from the nuclear speckles to several large clumps within the cell. Using a dominant-negative form of TAP and RNA interference to deplete TAP, we show that it is essential for bulk mRNA export in mammalian cells and is required for ORF 57-mediated viral RNA export. Furthermore, we show that the disruption of TAP reduces viral replication. These results indicate that HVS utilizes ORF 57 to recruit components of the exon junction complex and subsequently TAP to promote viral RNA export through the cellular mRNA export pathway.
Collapse
Key Words
- chromosomal region maintenance 1 (crm-1)
- exon junction complex
- herpesvirus
- mrna export
- open reading frame 57 (orf 57)
- tip-associated protein (tap)
- cmv, cytomegalovirus
- crm-1, chromosomal region maintenance 1
- cte, constitutive transport element
- ejc, exon junction complex
- fish, fluorescence in situ hybridization
- gb, glycoprotein b
- gfp, green fluorescent protein
- gst, glutathione s-transferase
- hek-293t cells, human embryonic kidney 293t cells
- hsv, herpes simplex virus
- hvs, herpesvirus saimiri
- kshv, kaposi's sarcoma associated herpesvirus
- lmb, leptomycin b
- moi, multiplicity of infection
- ref, rna export factor
- mref2-1, murine ref2-1
- nes, nuclear export signal
- nmd, nonsense-mediated decay
- omk cells, owl monkey kidney cells
- orf 57, open reading frame 57
- rnai, rna interference
- rnps1, rna-binding protein prevalent during s phase
- rrm, rna recognition motif
- tap, tip-associated protein
- trex complex, transcription and export complex
- yfp, yellow fluorescent protein
Collapse
Affiliation(s)
- Ben J. L. Williams
- *Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, Manchester M60 1QD, U.K
| | - James R. Boyne
- †School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, U.K
| | - Delyth J. Goodwin
- †School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, U.K
| | - Louise Roaden
- *Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, Manchester M60 1QD, U.K
| | - Guillaume M. Hautbergue
- *Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, Manchester M60 1QD, U.K
| | - Stuart A. Wilson
- *Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, Manchester M60 1QD, U.K
| | - Adrian Whitehouse
- †School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, U.K
- ‡Molecular and Cellular Biology Research Group, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| |
Collapse
|