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Liu SY, Ikegami K. Nuclear lamin phosphorylation: an emerging role in gene regulation and pathogenesis of laminopathies. Nucleus 2021; 11:299-314. [PMID: 33030403 PMCID: PMC7588210 DOI: 10.1080/19491034.2020.1832734] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Decades of studies have established that nuclear lamin polymers form the nuclear lamina, a protein meshwork that supports the nuclear envelope structure and tethers heterochromatin to the nuclear periphery. Much less is known about unpolymerized nuclear lamins in the nuclear interior, some of which are now known to undergo specific phosphorylation. A recent finding that phosphorylated lamins bind gene enhancer regions offers a new hypothesis that lamin phosphorylation may influence transcriptional regulation in the nuclear interior. In this review, we discuss the regulation, localization, and functions of phosphorylated lamins. We summarize kinases that phosphorylate lamins in a variety of biological contexts. Our discussion extends to laminopathies, a spectrum of degenerative disorders caused by lamin gene mutations, such as cardiomyopathies and progeria. We compare the prevailing hypothesis for laminopathy pathogenesis based on lamins’ function at the nuclear lamina with an emerging hypothesis based on phosphorylated lamins’ function in the nuclear interior.
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Affiliation(s)
- Sunny Yang Liu
- Department of Pediatrics, The University of Chicago , Chicago, Illinois, USA
| | - Kohta Ikegami
- Department of Pediatrics, The University of Chicago , Chicago, Illinois, USA.,Division of Molecular and Cardiovascular Biology, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio, USA
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2
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Hah J, Kim DH. Deciphering Nuclear Mechanobiology in Laminopathy. Cells 2019; 8:E231. [PMID: 30862117 PMCID: PMC6468464 DOI: 10.3390/cells8030231] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 02/23/2019] [Accepted: 03/05/2019] [Indexed: 12/13/2022] Open
Abstract
Extracellular mechanical stimuli are translated into biochemical signals inside the cell via mechanotransduction. The nucleus plays a critical role in mechanoregulation, which encompasses mechanosensing and mechanotransduction. The nuclear lamina underlying the inner nuclear membrane not only maintains the structural integrity, but also connects the cytoskeleton to the nuclear envelope. Lamin mutations, therefore, dysregulate the nuclear response, resulting in abnormal mechanoregulations, and ultimately, disease progression. Impaired mechanoregulations even induce malfunction in nuclear positioning, cell migration, mechanosensation, as well as differentiation. To know how to overcome laminopathies, we need to understand the mechanisms of laminopathies in a mechanobiological way. Recently, emerging studies have demonstrated the varying defects from lamin mutation in cellular homeostasis within mechanical surroundings. Therefore, this review summarizes recent findings highlighting the role of lamins, the architecture of nuclear lamina, and their disease relevance in the context of nuclear mechanobiology. We will also provide an overview of the differentiation of cellular mechanics in laminopathy.
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Affiliation(s)
- Jungwon Hah
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Korea.
| | - Dong-Hwee Kim
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Korea.
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3
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Bikkul MU, Clements CS, Godwin LS, Goldberg MW, Kill IR, Bridger JM. Farnesyltransferase inhibitor and rapamycin correct aberrant genome organisation and decrease DNA damage respectively, in Hutchinson-Gilford progeria syndrome fibroblasts. Biogerontology 2018; 19:579-602. [PMID: 29907918 PMCID: PMC6223735 DOI: 10.1007/s10522-018-9758-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 05/30/2018] [Indexed: 12/20/2022]
Abstract
Hutchinson–Gilford progeria syndrome (HGPS) is a rare and fatal premature ageing disease in children. HGPS is one of several progeroid syndromes caused by mutations in the LMNA gene encoding the nuclear structural proteins lamins A and C. In classic HGPS the mutation G608G leads to the formation of a toxic lamin A protein called progerin. During post-translational processing progerin remains farnesylated owing to the mutation interfering with a step whereby the farnesyl moiety is removed by the enzyme ZMPSTE24. Permanent farnesylation of progerin is thought to be responsible for the proteins toxicity. Farnesyl is generated through the mevalonate pathway and three drugs that interfere with this pathway and hence the farnesylation of proteins have been administered to HGPS children in clinical trials. These are a farnesyltransferase inhibitor (FTI), statin and a bisphosphonate. Further experimental studies have revealed that other drugs such as N-acetyl cysteine, rapamycin and IGF-1 may be of use in treating HGPS through other pathways. We have shown previously that FTIs restore chromosome positioning in interphase HGPS nuclei. Mis-localisation of chromosomes could affect the cells ability to regulate proper genome function. Using nine different drug treatments representing drug regimes in the clinic we have shown that combinatorial treatments containing FTIs are most effective in restoring specific chromosome positioning towards the nuclear periphery and in tethering telomeres to the nucleoskeleton. On the other hand, rapamycin was found to be detrimental to telomere tethering, it was, nonetheless, the most effective at inducing DNA damage repair, as revealed by COMET analyses.
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Affiliation(s)
- Mehmet U Bikkul
- Progeria Research Team, Healthy Ageing Theme, Institute for Environment, Health and Societies, College of Health and Life Sciences, Brunel University London, Kingston Lane, Uxbridge, UB8 3PH, UK
| | - Craig S Clements
- Progeria Research Team, Healthy Ageing Theme, Institute for Environment, Health and Societies, College of Health and Life Sciences, Brunel University London, Kingston Lane, Uxbridge, UB8 3PH, UK
| | - Lauren S Godwin
- Progeria Research Team, Healthy Ageing Theme, Institute for Environment, Health and Societies, College of Health and Life Sciences, Brunel University London, Kingston Lane, Uxbridge, UB8 3PH, UK
| | - Martin W Goldberg
- Department of Biosciences, Durham University, Science Laboratories, South Road, Durham, DH1 3LE, UK
| | - Ian R Kill
- Progeria Research Team, Healthy Ageing Theme, Institute for Environment, Health and Societies, College of Health and Life Sciences, Brunel University London, Kingston Lane, Uxbridge, UB8 3PH, UK
| | - Joanna M Bridger
- Progeria Research Team, Healthy Ageing Theme, Institute for Environment, Health and Societies, College of Health and Life Sciences, Brunel University London, Kingston Lane, Uxbridge, UB8 3PH, UK.
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4
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Luca G, Calvitti M, Nastruzzi C, Macchiarulo G, Becchetti E, Neri LM, Capitani S, Basta G, Brunetti P, Calafiore R, Cameron DF. Effects of Simulated Microgravity on the Morphology and Function of Neonatal Porcine Cell Clusters Cultured with and without Sertoli Cells. Cell Transplant 2017; 15:55-65. [PMID: 16700330 DOI: 10.3727/000000006783982223] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Human islet allografts are well known to induce full and sustained remission of hyperglycemia, with complete normalization of key metabolic parameters. Nevertheless, acquiring human islets, even from cadaveric human donor pancreases, remains a significant impediment to successful transplantation therapy for diabetes. To overcome this difficulty, neonatal porcine cell clusters (NPCCs) have been considered for human islet substitutes because they are easily obtained by collagenase digestion of the neonatal piglet pancreas. Currently, the major hurdle in using NPCCs for xenograft is the delay (time lag) in achieving the posttransplant normalization of blood glucose levels in animal diabetic recipients. The present work is the first attempt to evaluate whether incubation of NPCCs in simulated microgravity, in the presence or absence of Sertoli cells (SC), may reduce the maturation time lag of β-cells by differentiation acceleration in vitro, thereby expediting production, viability, and acquisition of functional competence of pretransplantation β-cell-enriched islets. Following a 3-day incubation period, NPCCs maintained in conventional culture, NPCCs incubated in simulated microgravity in the HARV biochamber, and NPCCs plus co-incubated SC in simulated microgravity were examined for viability, morphology, and insulin secretion. Results show that NPCCs grown alone in the HARV biochamber are superior in quality, both in terms of viability and functional competence, when compared to other culture pretreatment protocols. This finding strongly suggests that NPCC pretreatment in simulated microgravity may enhance the transplantation success of NPCCs in the diabetic recipient.
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Affiliation(s)
- G Luca
- Department of Internal Medicine and Endocrine and Metabolic Sciences, University of Perugia, Perugia, Italy
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5
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Mitchell TRH, Zhu XD. Methylated TRF2 associates with the nuclear matrix and serves as a potential biomarker for cellular senescence. Aging (Albany NY) 2014; 6:248-63. [PMID: 24721747 PMCID: PMC4032793 DOI: 10.18632/aging.100650] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 04/03/2014] [Indexed: 11/25/2022]
Abstract
Methylation of N-terminal arginines of the shelterin component TRF2 is important for cellular proliferation. While TRF2 is found at telomeres, where it plays an essential role in maintaining telomere integrity, little is known about the cellular localization of methylated TRF2. Here we report that the majority of methylated TRF2 is resistant to extraction by high salt buffer and DNase I treatment, indicating that methylated TRF2 is tightly associated with the nuclear matrix. We show that methylated TRF2 drastically alters its nuclear staining as normal human primary fibroblast cells approach and enter replicative senescence. This altered nuclear staining, which is found to be overwhelmingly associated with misshapen nuclei and abnormal nuclear matrix folds, can be suppressed by hTERT and it is barely detectable in transformed and cancer cell lines. We find that dysfunctional telomeres and DNA damage, both of which are potent inducers of cellular senescence, promote the altered nuclear staining of methylated TRF2, which is dependent upon the ATM-mediated DNA damage response. Collectively, these results suggest that the altered nuclear staining of methylated TRF2 may represent ATM-mediated nuclear structural alteration associated with cellular senescence. Our data further imply that methylated TRF2 can serve as a potential biomarker for cellular senescence.
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Affiliation(s)
- Taylor R H Mitchell
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
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6
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Legartová S, Stixová L, Laur O, Kozubek S, Sehnalová P, Bártová E. Nuclear Structures Surrounding Internal Lamin Invaginations. J Cell Biochem 2014; 115:476-87. [DOI: 10.1002/jcb.24681] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 09/23/2013] [Indexed: 12/16/2022]
Affiliation(s)
- Soňa Legartová
- Institute of Biophysics; Academy of Sciences of the Czech Republic; 612 65 Brno Czech Republic
| | - Lenka Stixová
- Institute of Biophysics; Academy of Sciences of the Czech Republic; 612 65 Brno Czech Republic
| | - Oskar Laur
- Emory University School of Medicine; Emory University; Atlanta Georgia 30322
| | - Stanislav Kozubek
- Institute of Biophysics; Academy of Sciences of the Czech Republic; 612 65 Brno Czech Republic
| | - Petra Sehnalová
- Institute of Biophysics; Academy of Sciences of the Czech Republic; 612 65 Brno Czech Republic
| | - Eva Bártová
- Institute of Biophysics; Academy of Sciences of the Czech Republic; 612 65 Brno Czech Republic
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7
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Mahen R, Hattori H, Lee M, Sharma P, Jeyasekharan AD, Venkitaraman AR. A-type lamins maintain the positional stability of DNA damage repair foci in mammalian nuclei. PLoS One 2013; 8:e61893. [PMID: 23658700 PMCID: PMC3642183 DOI: 10.1371/journal.pone.0061893] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 03/14/2013] [Indexed: 02/02/2023] Open
Abstract
A-type lamins encoded by LMNA form a structural fibrillar meshwork within the mammalian nucleus. How this nuclear organization may influence the execution of biological processes involving DNA transactions remains unclear. Here, we characterize changes in the dynamics and biochemical interactions of lamin A/C after DNA damage. We find that DNA breakage reduces the mobility of nucleoplasmic GFP-lamin A throughout the nucleus as measured by dynamic fluorescence imaging and spectroscopy in living cells, suggestive of incorporation into stable macromolecular complexes, but does not induce the focal accumulation of GFP-lamin A at damage sites. Using a proximity ligation assay and biochemical analyses, we show that lamin A engages chromatin via histone H2AX and its phosphorylated form (γH2AX) induced by DNA damage, and that these interactions are enhanced after DNA damage. Finally, we use three-dimensional time-lapse imaging to show that LMNA inactivation significantly reduces the positional stability of DNA repair foci in living cells. This defect is partially rescued by the stable expression of GFP-lamin A. Thus collectively, our findings suggest that the dynamic structural meshwork formed by A-type lamins anchors sites of DNA repair in mammalian nuclei, providing fresh insight into the control of DNA transactions by nuclear structural organization.
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Affiliation(s)
- Robert Mahen
- The Medical Research Council Cancer Cell Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Hiroyoshi Hattori
- The Medical Research Council Cancer Cell Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Miyoung Lee
- The Medical Research Council Cancer Cell Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Pooja Sharma
- The Medical Research Council Cancer Cell Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Anand D. Jeyasekharan
- The Medical Research Council Cancer Cell Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Ashok R. Venkitaraman
- The Medical Research Council Cancer Cell Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
- * E-mail:
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8
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Stixová L, Matula P, Kozubek S, Gombitová A, Cmarko D, Raška I, Bártová E. Trajectories and nuclear arrangement of PML bodies are influenced by A-type lamin deficiency. Biol Cell 2012; 104:418-32. [PMID: 22443097 DOI: 10.1111/boc.201100053] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 03/16/2012] [Indexed: 01/08/2023]
Abstract
BACKGROUND INFORMATION Promyelocytic leukaemia (PML) bodies are specific nuclear structures with functional significance for acute promyelocytic leukaemia. In this study, we analysed the trajectories of PML bodies using single-particle tracking. RESULTS We observed that the recovery of PML protein after photobleaching was ATP dependent in both wild-type (wt) and A-type lamin-deficient cells. The movement of PML bodies was faster and the nuclear area occupied by particular PML bodies was larger in A-type lamin-deficient fibroblasts compared with their wt counterparts. Moreover, dysfunction of the LMNA gene increased the frequency of mutual interactions between individual PML bodies and influenced the morphology of these domains at the ultrastructural level. As a consequence of A-type lamin deficiency, PML protein accumulated in nuclear blebs and frequently appeared at the nuclear periphery. CONCLUSIONS We suggest that the physiological function of lamin A proteins is important for events that occur in the compartment of PML bodies. This observation was confirmed in other experimental models characterised by lamin changes, including apoptosis or the differentiation of mouse embryonic stem cells.
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Affiliation(s)
- Lenka Stixová
- Institute of Biophysics, Academy of Sciences of the Czech Republic, 61265 Brno, Czech Republic
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9
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Nuclear actin and lamins in viral infections. Viruses 2012; 4:325-47. [PMID: 22590674 PMCID: PMC3347030 DOI: 10.3390/v4030325] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 02/20/2012] [Accepted: 02/21/2012] [Indexed: 12/11/2022] Open
Abstract
Lamins are the best characterized cytoskeletal components of the cell nucleus that help to maintain the nuclear shape and participate in diverse nuclear processes including replication or transcription. Nuclear actin is now widely accepted to be another cytoskeletal protein present in the nucleus that fulfills important functions in the gene expression. Some viruses replicating in the nucleus evolved the ability to interact with and probably utilize nuclear actin for their replication, e.g., for the assembly and transport of capsids or mRNA export. On the other hand, lamins play a role in the propagation of other viruses since nuclear lamina may represent a barrier for virions entering or escaping the nucleus. This review will summarize the current knowledge about the roles of nuclear actin and lamins in viral infections.
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10
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Affiliation(s)
- Kris Noel Dahl
- Department of Biomedical Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA.
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11
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Takata H, Nishijima H, Ogura SI, Sakaguchi T, Bubulya PA, Mochizuki T, Shibahara KI. Proteome analysis of human nuclear insoluble fractions. Genes Cells 2010; 14:975-90. [PMID: 19695025 DOI: 10.1111/j.1365-2443.2009.01324.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The interphase nucleus is a highly ordered and compartmentalized organelle. Little is known regarding what elaborate mechanisms might exist to explain these properties of the nucleus. Also unresolved is whether some architectural components might facilitate the formation of functional intranuclear compartments or higher order chromatin structure. As the first step to address these questions, we performed an in-depth proteome analysis of nuclear insoluble fractions of human HeLa-S3 cells prepared by two different approaches: a high-salt/detergent/nuclease-resistant fraction and a lithium 3,5-diiodosalicylate/nuclease-resistant fraction. Proteins of the fractions were analyzed by liquid chromatography electrospray ionization tandem mass spectrometry, identifying 333 and 330 proteins from each fraction respectively. Among the insoluble nuclear proteins, we identified 37 hitherto unknown or functionally uncharacterized proteins. The RNA recognition motif, WD40 repeats, HEAT repeats and the SAP domain were often found in these identified proteins. The subcellular distribution of selected proteins, including DEK protein and SON protein, demonstrated their novel associations with nuclear insoluble materials, corroborating our MS-based analysis. This study establishes a comprehensive catalog of the nuclear insoluble proteins in human cells. Further functional analysis of the proteins identified in our study will significantly improve our understanding of the dynamic organization of the interphase nucleus.
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Affiliation(s)
- Hideaki Takata
- Department of Integrated Genetics, National Institute of Genetics, Research Organization of Information and Systems, Mishima 411-8540, Japan
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12
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Barboro P, D'Arrigo C, Repaci E, Bagnasco L, Orecchia P, Carnemolla B, Patrone E, Balbi C. Proteomic analysis of the nuclear matrix in the early stages of rat liver carcinogenesis: identification of differentially expressed and MAR-binding proteins. Exp Cell Res 2008; 315:226-39. [PMID: 19000672 DOI: 10.1016/j.yexcr.2008.10.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 09/24/2008] [Accepted: 10/20/2008] [Indexed: 11/19/2022]
Abstract
Tumor progression is characterized by definite changes in the protein composition of the nuclear matrix (NM). The interactions of chromatin with the NM occur via specific DNA sequences called MARs (matrix attachment regions). In the present study, we applied a proteomic approach along with a Southwestern assay to detect both differentially expressed and MAR-binding NM proteins, in persistent hepatocyte nodules (PHN) in respect with normal hepatocytes (NH). In PHN, the NM undergoes changes both in morphology and in protein composition. We detected over 500 protein spots in each two dimensional map and 44 spots were identified. Twenty-three proteins were differentially expressed; among these, 15 spots were under-expressed and 8 spots were over-expressed in PHN compared to NH. These changes were synchronous with several modifications in both NM morphology and the ability of NM proteins to bind nuclear RNA and/or DNA containing MARs sequences. In PHN, we observed a general decrease in the expression of the basic proteins that bound nuclear RNA and the over-expression of two species of Mw 135 kDa and 81 kDa and pI 6.7-7.0 and 6.2-7.4, respectively, which exclusively bind to MARs. These results suggest that the deregulated expression of these species might be related to large-scale chromatin reorganization observed in the process of carcinogenesis by modulating the interaction between MARs and the scaffold structure.
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Affiliation(s)
- Paola Barboro
- Istituto Nazionale per la Ricerca sul Cancro, Largo Rosanna Benzi, 10-16132 Genova, Italy
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Dreuillet C, Harper M, Tillit J, Kress M, Ernoult-Lange M. Mislocalization of human transcription factor MOK2 in the presence of pathogenic mutations of lamin A/C. Biol Cell 2008; 100:51-61. [PMID: 17760566 DOI: 10.1042/bc20070053] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND INFORMATION hsMOK2 (human MOK2) is a DNA-binding transcriptional repressor. For example, it represses the IRBP (interphotoreceptor retinoid-binding protein) gene by competing with the CRX (cone-rod homeobox protein) transcriptional activator for DNA binding. Previous studies have shown an interaction between hsMOK2 and nuclear lamin A/C. This interaction could be important to explain hsMOK2 ability to repress transcription. RESULTS In the present study, we have tested whether missense pathogenic mutations of lamin A/C, which are located in the hsMOK2-binding domain, could affect the interaction with hsMOK2. We find that none of the tested mutations is able to disrupt hsMOK2 binding in vitro or in vivo. However, we observe an aberrant cellular localization of hsMOK2 into nuclear aggregates when pathogenic lamin A/C mutant proteins are expressed. CONCLUSIONS These results indicate that pathogenic mutations in lamin A/C lead to sequestration of hsMOK2 into nuclear aggregates, which may deregulate MOK2 target genes.
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Affiliation(s)
- Caroline Dreuillet
- CNRS-FRE2937, Institut André Lwoff, 7 rue Guy Môquet, 94801 Villejuif, France
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Foster HA, Bridger JM. The genome and the nucleus: a marriage made by evolution. Genome organisation and nuclear architecture. Chromosoma 2005; 114:212-29. [PMID: 16133352 DOI: 10.1007/s00412-005-0016-6] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Revised: 06/29/2005] [Accepted: 07/04/2005] [Indexed: 01/15/2023]
Abstract
Genomes are housed within cell nuclei as individual chromosome territories. Nuclei contain several architectural structures that interact and influence the genome. In this review, we discuss how the genome may be organised within its nuclear environment with the position of chromosomes inside nuclei being either influenced by gene density or by chromosomes size. We compare interphase genome organisation in diverse species and reveal similarities and differences between evolutionary divergent organisms. Genome organisation is also discussed with relevance to regulation of gene expression, development and differentiation and asks whether large movements of whole chromosomes are really observed during differentiation. Literature and data describing alterations to genome organisation in disease are also discussed. Further, the nuclear structures that are involved in genome function are described, with reference to what happens to the genome when these structures contain protein from mutant genes as in the laminopathies.
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Affiliation(s)
- Helen A Foster
- Laboratory of Nuclear and Genomic Health, Cell and Chromosome Biology Group, Division of Biosciences, School of Health Sciences and Social Care, Brunel University, Uxbridge UB8 3PH, UK
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15
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Luca G, Nastruzzi C, Calvitti M, Becchetti E, Baroni T, Neri LM, Capitani S, Basta G, Brunetti P, Calafiore R. Accelerated functional maturation of isolated neonatal porcine cell clusters: in vitro and in vivo results in NOD mice. Cell Transplant 2005; 14:249-61. [PMID: 16052907 DOI: 10.3727/000000005783983034] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Neonatal porcine cell clusters (NPCCs) might replace human for transplant in patients with type 1 diabetes mellitus (T1DM). However, these islets are not immediately functional, due to their incomplete maturation/ differentiation. We then have addressed: 1) to assess whether in vitro coculture of islets with homologous Sertoli cells (SC) would shorten NPCCs' functional time lag, by accelerating the beta-cell biological maturation/differentiation; 2) to evaluate metabolic outcome of the SC preincubated, and microencapsulated NPCCs, upon graft into spontaneously diabetic NOD mice. The islets, isolated from < 3 day piglets, were examined in terms of morphology/viability/function and final yield. SC effects on the islet maturation pathways, both in vitro and in vivo, upon microencapsulation in alginate/poly-L-ornithine, and intraperitoneal graft into spontaneously diabetic NOD mice were determined. Double fluorescence immunolabeling showed increase in beta-cell mass for SC+ neonatal porcine islets versus islets alone. In vitro insulin release in response to glucose, as well as mRNA insulin expression, were significantly higher for SC+ neonatal porcine islets compared with control, thereby confirming SC-induced increase in viable and functional beta-cell mass. Graft of microencapsulated SC+ neonatal porcine islets versus encapsulated islets alone resulted in significantly longer remission of hyperglycemia in NOD mice. We have preliminarily shown that the in vitro NPCCs' maturation time lag can dramatically be curtailed by coincubating these islets with SC. Graft of microencapsulated neonatal porcine islets, precultured in Sertoli cells, has been proven successful in correcting hyperglycemia in stringent animal model of spontaneous diabetes.
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Affiliation(s)
- Giovanni Luca
- Department of Internal Medicine (Di.M.I.), Section of Internal Medicine and Endocrine and Metabolic Sciences, University of Perugia, Via E. Dal Pozzo, Perugia 06126, Italy
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16
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Arikawa M, Saito A, Omura G, Mostafa Kamal Khan SM, Suetomo Y, Kakuta S, Suzaki T. Ca2+-dependent nuclear contraction in the heliozoon Actinophrys sol. Cell Calcium 2005; 38:447-55. [PMID: 16099499 DOI: 10.1016/j.ceca.2005.06.034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Revised: 06/25/2005] [Accepted: 06/27/2005] [Indexed: 11/26/2022]
Abstract
Ca2+-dependent contractility was found to exist in the nucleus of the heliozoon protozoan Actinophrys sol. Upon addition of Ca2+ ([Ca2+]free = 2.0 x 10(-3) M), diameters of isolated and detergent-extracted nuclei became reduced from 16.5+/-1.7 microm to 11.0+/-1.3 microm. The threshold level of [Ca2+]free for the nuclear contraction was 2.9 x 10(-7) M. The nuclear contraction was not induced by Mg2+, and was not inhibited by colchicine or cytochalasin B. Contracted nuclei became expanded when Ca2+ was removed by EGTA; thus cycles of contraction and expansion could be repeated many times by alternating addition of Ca2+ and EGTA. The Ca2+-dependent nuclear contractility remained even after high salt treatment, suggesting a possible involvement of nucleoskeletal components in the nuclear contraction. Electron microscopy showed that, in the relaxed state, filamentous structures were observed to spread in the nucleus to form a network. After addition of Ca2+, they became aggregated and constructed a mass of thicker filaments, followed by re-distribution of the filaments spread around inside of the nucleus when Ca2+ was removed. These results suggest that the nuclear contraction is induced by Ca2+-dependent transformation of the filamentous structures in the nucleus.
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Affiliation(s)
- Mikihiko Arikawa
- Department of Biological Sciences, Faculty of Science, Nara Women's University, Kitauoyanishi-machi, Nara 630-8506, Japan.
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17
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Senda T, Iizuka-Kogo A, Shimomura A. Visualization of the nuclear lamina in mouse anterior pituitary cells and immunocytochemical detection of lamin A/C by quick-freeze freeze-substitution electron microscopy. J Histochem Cytochem 2005; 53:497-507. [PMID: 15805424 DOI: 10.1369/jhc.4a6478.2005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the nuclear lamina in the quickly frozen anterior pituitary cells by electron microscopic techniques combined with freeze substitution, deep etching, and immunocytochemistry and compared it with that in the chemically fixed cells. By quick-freeze freeze-substitution electron microscopy, an electron-lucent layer, as thick as 20 nm, was revealed just inside the inner nuclear membrane, whereas in the conventionally glutaraldehyde-fixed cells the layer was not seen. By quick-freeze deep-etch electron microscopy, we could not distinguish definitively the layer corresponding to the nuclear lamina in either fresh unfixed or glutaraldehyde-fixed cells. Immunofluorescence microscopy showed that lamin A/C in the nucleus was detected in the acetone-fixed cells and briefly in paraformaldehyde-fixed cells but not in the cells with prolonged paraformaldehyde fixation. Nuclear localization of lamin A/C was revealed by immunogold electron microscopy also in the quickly frozen and freeze-substituted cells, but not in the paraformaldehyde-fixed cells. Lamin A/C was localized mainly in the peripheral nucleoplasm within 60 nm from the inner nuclear membrane, which corresponded to the nuclear lamina. These results suggest that the nuclear lamina can be preserved both ultrastructurally and immunocytochemically by quick-freezing fixation, rather than by conventional chemical fixation.
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Affiliation(s)
- Takao Senda
- Department of Anatomy I, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan.
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18
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Muralikrishna B, Thanumalayan S, Jagatheesan G, Rangaraj N, Karande AA, Parnaik VK. Immunolocalization of detergent-susceptible nucleoplasmic lamin A/C foci by a novel monoclonal antibody. J Cell Biochem 2004; 91:730-9. [PMID: 14991764 DOI: 10.1002/jcb.10765] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The A-type lamins are localized in the interior of the nucleus as well as on the nuclear periphery. In this study, we have characterized a monoclonal antibody LA-2F9 produced against recombinant rat lamin A which stains a subpopulation of various cell types in a pattern of small nucleoplasmic foci that are unusually susceptible to mild detergent/salt extraction. The specific reactivity of mAb LA-2F9 towards lamins was confirmed by immunoblotting of HeLa and C3H10T(1/2) whole cell lysates and nuclear lysates. The epitope for LA-2F9 was narrowed down to amino acid residues 268-278 (SAKLDNARQSA). To check whether the appearance of lamin foci was cell-cycle-dependent, C3H10T(1/2) cells were serum-starved and then refed to trigger cells to enter the G(1) phase of the cell-cycle. The intensity of staining increased 3.5-fold within 6 h of refeeding, when the maximum number of cells were labeled with LA-2F9. We also checked whether the LA-2F9 foci colocalized with nuclear proteins known to be distributed in small foci such as hnRNPs, snRNPs, SC-35, and p80 coilin, but did not find evidence of colocalization. Our studies suggest that LA-2F9 has a novel and specific reactivity towards detergent-susceptible lower order lamin structures that are likely to be assembly intermediates.
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Affiliation(s)
- Bh Muralikrishna
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad-500007, India
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19
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Vlcek S, Foisner R, Wilson KL. Lco1 is a novel widely expressed lamin-binding protein in the nuclear interior. Exp Cell Res 2004; 298:499-511. [PMID: 15265697 DOI: 10.1016/j.yexcr.2004.04.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2004] [Revised: 04/20/2004] [Indexed: 12/25/2022]
Abstract
A-type lamins are localized at the nuclear envelope and in the nucleoplasm, and are implicated in human diseases called laminopathies. In a yeast two-hybrid screen with lamin C, we identified a novel widely expressed 171-kDa protein that we named Lamin companion 1 (Lco1). Three independent biochemical assays showed direct binding of Lco1 to the C-terminal tail of A-type lamins with an affinity of 700 nM. Lco1 also bound the lamin B1 tail with lower affinity (2 microM). Ectopic Lco1 was found primarily in the nucleoplasm and colocalized with endogenous intranuclear A-type lamins in HeLa cells. Overexpression of prelamin A caused redistribution of ectopic Lco1 to the nuclear rim together with ectopic lamin A, confirming association of Lco1 with lamin A in vivo. Whereas the major C-terminal lamin-binding fragment of Lco1 was cytoplasmic, the N-terminal Lco1 fragment localized in the nucleoplasm upon expression in cells. Furthermore, full-length Lco1 was nuclear in cells lacking A-type lamins, showing that A-type lamins are not required for nuclear targeting of Lco1. We conclude that Lco1 is a novel intranuclear lamin-binding protein. We hypothesize that Lco1 is involved in organizing the internal lamin network and potentially relevant as a laminopathy disease gene or modifier.
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Affiliation(s)
- Sylvia Vlcek
- Max F. Perutz Laboratories, University Departments at the Vienna Biocenter, Department of Medical Biochemistry, Medical University of Vienna, A-1030 Vienna, Austria
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20
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Bode J, Goetze S, Heng H, Krawetz SA, Benham C. From DNA structure to gene expression: mediators of nuclear compartmentalization and dynamics. Chromosome Res 2004; 11:435-45. [PMID: 12971720 DOI: 10.1023/a:1024918525818] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Eukaryotic genomes are functionally compartmentalized into chromatin domains by their attachment to a supporting structure that has traditionally been termed the nuclear matrix. Present evidence indicates the dynamics of this entity, which requires particular properties of the elements that mediate this kind of interaction. Above all, this is enabled by the so-called 'mass binding phenomenon' by which scaffold/matrix-attachment regions (S/MARs) reversibly associate with ubiquitous factors. Recent investigations and novel techniques have shown that these contacts can be altered by modulators as well as by specific interactions with the components of enhancers and locus control regions.
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Affiliation(s)
- J Bode
- GBF-German Research Center for Biotechnology/Epigenetic Regulation, Mascheroder Weg 1, D-38124 Braunschweig.
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21
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Chun TH, Itoh H, Subramanian L, Iñiguez-Lluhí JA, Nakao K. Modification of GATA-2 transcriptional activity in endothelial cells by the SUMO E3 ligase PIASy. Circ Res 2003; 92:1201-8. [PMID: 12750312 DOI: 10.1161/01.res.0000076893.70898.36] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
GATA sequences are required for the optimal expression of endothelial cell-specific genes, including endothelin-1 (ET-1). We have identified PIASy in a search for new GATA-2 interacting proteins that can regulate GATA-2-mediated endothelial gene expression. Notably, among the cell populations comprising vascular walls, PIASy mRNA is selectively expressed in endothelial cells, and its expression can be regulated by angiogenic growth factors. We show that GATA-2 is covalently modified by small ubiquitin-like modifier (SUMO)-1 and -2 and that PIASy, through its E3 SUMO ligase activity, preferentially enhances the conjugation of SUMO-2 to GATA-2. Through a functional analysis, we demonstrate that PIASy potently suppresses the activity of the GATA-2-dependent human ET-1 promoter in endothelial cells. The suppressive effect of PIASy requires the GATA-binding site in the ET-1 promoter and depends on its interaction with GATA-2, which requires both N-terminal (amino acids 1-183) and C-terminal (amino acids 414-510) sequences in PIASy. We conclude that PIASy enhances the conjugation of SUMO-2 to GATA-2 and that the interaction of PIASy with GATA-2 can modulate GATA-mediated ET-1 transcription activity in endothelial cells through a RING-like domain-independent mechanism.
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Affiliation(s)
- Tae-Hwa Chun
- Department of Medicine and Clinical Science, University Graduate School of Medicine, Kyoto, Japan.
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22
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Luca G, Calvitti M, Basta G, Baroni T, Neri LM, Becchetti E, Capitani S, Novaes G, Correa-Giannella ML, Kalapothakis E, Engler SSM, Eliaschewitz FG, Sogayar MC, Fanelli C, Brunetti P, Calafiore R. Mitogenic Effects of Brazilian Arthropod Venom on Isolated Islet Beta Cells: In Vitro Morphologic Ultrastructural and Functional Studies. J Investig Med 2003. [DOI: 10.1177/108155890305100209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Background One of the major pitfalls associated with use of isolated adult islets of Langerhans’ cells is their minimal mitotic capacity. Consequently, maintenance of a steady viable islet cell mass is very difficult. To explore how to enhance beta-cell mitogenesis, we have examined the effects of venom fractions extracted from a Brazilian scorpion on morphologic and functional beta-cell patterns. The venom was previously known to induce nesidioblastosis-like effects with chronic hypoglycemia and pancreatitis in animal models. Methods Venom fractions purified from Tityus bahiensis were incubated with batches of isolated rat islets, while a morphologic examination, glucose-stimulated insulin release, insulin content, and insulin messenger ribonucleic acid (mRNA) were carried out early during incubation. On fixation and double fluorescence immunolabeling (rhodamine for anti-insulin monoclonal antibodies; fluorescein for anti-5-bromodeoxyuridine), the preparations were imaged by confocal laser microscopy (CLM) for morphometric quantification of the mitoses. Insulin recovery and mRNA were also assessed at 21 days of culture. Results Under CLM examination, the beta-cell mitotic rate significantly rose from 1 to 12.8% for the venom-exposed islets. At day 7, insulin release and content were significantly lower for the venom-exposed than the control islets. However, at day 21 of culture, insulin release in response to static incubation with glucose and insulin mRNA from the venom-exposed islets was higher than controls ( p < .05). Conclusions Incubation with the scorpion venom induced a rapid and significant increase in the beta-cell proliferation not associated with a short-term increase in insulin secretion. The latter fully resumed and overcame controls later in culture, possibly after completion of the beta-cell expansion process.
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Affiliation(s)
- Giovanni Luca
- From the Departments of Internal Medicine, Section of Internal Medicine and Endocrine and Metabolic Sciences, University of Perugia, Perugia, Italy
| | - Mario Calvitti
- Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
| | - Giuseppe Basta
- From the Departments of Internal Medicine, Section of Internal Medicine and Endocrine and Metabolic Sciences, University of Perugia, Perugia, Italy
| | - Tiziano Baroni
- Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
| | - Luca M. Neri
- Department of Morphology and Embryology, Section of Human Anatomy, University of Ferrara, Ferrara, Italy, and Consorzio Interuniversitario peri Trapianti d'Organo, Rome, Italy
| | - Ennio Becchetti
- Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
| | - Silvano Capitani
- Department of Morphology and Embryology, Section of Human Anatomy, University of Ferrara, Ferrara, Italy, and Consorzio Interuniversitario peri Trapianti d'Organo, Rome, Italy
| | | | | | | | | | | | | | - Carmine Fanelli
- From the Departments of Internal Medicine, Section of Internal Medicine and Endocrine and Metabolic Sciences, University of Perugia, Perugia, Italy
| | - Paolo Brunetti
- From the Departments of Internal Medicine, Section of Internal Medicine and Endocrine and Metabolic Sciences, University of Perugia, Perugia, Italy
| | - Riccardo Calafiore
- From the Departments of Internal Medicine, Section of Internal Medicine and Endocrine and Metabolic Sciences, University of Perugia, Perugia, Italy
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23
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Luca G, Calvitti M, Basta G, Baroni T, Neri LM, Becchetti E, Capitani S, Novaes G, Correa-Giannella ML, Kalapothakis E, Engler SSM, Eliaschewitz FG, Sogayar MC, Fanelli C, Brunetti P, Calafiore R. Mitogenic Effects of Brazilian Arthropod Venom on Isolated Islet Beta Cells: In Vitro Morphologic Ultrastructural and Functional Studies. J Investig Med 2003. [DOI: 10.2310/6650.2003.34200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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24
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Barboro P, D'Arrigo C, Mormino M, Coradeghini R, Parodi S, Patrone E, Balbi C. An intranuclear frame for chromatin compartmentalization and higher-order folding. J Cell Biochem 2003; 88:113-20. [PMID: 12461780 DOI: 10.1002/jcb.10378] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Recent ultrastructural, immunoelectron, and confocal microscopy observations done in our laboratory [Barboro et al. [2002] Exp. Cell. Res. 279:202-218] have confirmed that lamins and the nuclear mitotic apparatus protein (NuMA) are localized inside the interphase nucleus in a polymerized form. This provided evidence of the existence of a RNA stabilized lamin/NuMA frame, consisting of a web of thin ( approximately 3 and approximately 5 nm) lamin filaments to which NuMA is anchored mainly in the form of discrete islands, which might correspond to the minilattices described by Harborth et al. [1999] (EMBO. J. 18:1689-1700). In this article we propose that this scaffold is involved in the compartmentalization of both chromatin and functional domains and further determines the higher-order nuclear organization. This hypothesis is strongly supported by the scrutiny of different structural transitions which occur inside the nucleus, such as chromatin displacement and rearrangements, the collapse of the internal nuclear matrix after RNA digestion and the disruption of chromosome territories induced by RNase A and high salt treatment. All of these destructive events directly depend on the loss of the stabilizing effect exerted on the different levels of structural organization by the interaction of RNA with lamins and/or NuMA. Therefore, the integrity of nuclear RNA must be safeguarded as far as possible to isolate the matrix in the native form. This material will allow for the first time the unambiguous ultrastructural localization inside the INM of the components of the functional domains, so opening new avenues of investigation on the mechanisms of gene expression in eukaryotes.
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Affiliation(s)
- Paola Barboro
- Istituto Nazionale per la Ricerca sul Cancro, I-16132 Genova, Italy
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25
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Dreuillet C, Tillit J, Kress M, Ernoult-Lange M. In vivo and in vitro interaction between human transcription factor MOK2 and nuclear lamin A/C. Nucleic Acids Res 2002; 30:4634-42. [PMID: 12409453 PMCID: PMC135794 DOI: 10.1093/nar/gkf587] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The human and murine MOK2 proteins are factors able to recognize both DNA and RNA through their zinc finger motifs. This dual affinity of MOK2 suggests that MOK2 might be involved in transcription and post-transcriptional regulation of MOK2 target genes. The IRBP gene contains two MOK2-binding elements, a complete 18 bp MOK2-binding site located in intron 2 and the essential core MOK2-binding site (8 bp of conserved 3'-half-site) located in the IRBP promoter. We have demonstrated that MOK2 can bind to the 8 bp present in the IRBP promoter and repress transcription from this promoter by competing with the CRX activator for DNA binding. In this study, we identify a novel interaction between lamin A/C and hsMOK2 by using the yeast two-hybrid system. The interaction, which was confirmed by GST pull-down assays and co-immunolocalization studies in vivo, requires the N-terminal acidic domain of hsMOK2 and the coiled 2 domain of lamin A/C. Furthermore, we show that a fraction of hsMOK2 protein is associated with the nuclear matrix. We therefore suggest that hsMOK2 interactions with lamin A/C and the nuclear matrix may be important for its ability to repress transcription.
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Affiliation(s)
- Caroline Dreuillet
- GMIFC-CNRS-UPR1983, Institut André Lwoff, 7 Rue Guy Môquet, 94801 Villejuif, France
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26
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Vlcek S, Korbei B, Foisner R. Distinct functions of the unique C terminus of LAP2alpha in cell proliferation and nuclear assembly. J Biol Chem 2002; 277:18898-907. [PMID: 11864981 DOI: 10.1074/jbc.m200048200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The non-membrane-bound lamina-associated polypeptide 2 isoform, LAP2alpha, forms nucleoskeletal structures with A-type lamins and interacts with chromosomes in a cell cycle-dependent manner. LAP2alpha contains a LEM (LAP2, emerin, and MAN1) domain in the constant N terminus that binds to chromosomal barrier-to-autointegration factor, and a C-terminal unique region that is essential for chromosome binding. Here we show that C-terminal LAP2alpha fragment efficiently bound to mitotic chromosomes and inhibited assembly of endogenous LAP2alpha, nuclear membranes, and lamins A/C in in vitro nuclear assembly assays. Full-length recombinant LAP2alpha, which bound to chromosomes, and N-terminal fragment, which did not bind, had no effect on assembly. This suggested an essential role for the LAP2alpha C terminus in chromosome association and for the N-terminal LEM domain in subsequent assembly stages. In vivo analysis upon transient expression of GFP-tagged LAP2alpha fragments confirmed that, unlike the N-terminal fragment, the C-terminal fragment was able to bind to chromosomes during mitosis, if expressed weakly. At higher expression levels, C-terminal LAP2alpha fragment and full-length protein led to cell cycle arrest in interphase and apoptosis, as shown by fluorescence-activated cell sorter analysis, time lapse microscopy, and BrdUrd incorporation assays. These data indicated distinct functions of LAP2alpha in cell cycle progression during interphase and in nuclear reassembly during mitosis.
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Affiliation(s)
- Sylvia Vlcek
- Department of Biochemistry and Molecular Cell Biology, Vienna Biocenter, University of Vienna, A-1030 Vienna, Austria
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27
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Bortul R, Aluigi M, Tazzari PL, Tabellini G, Baldini G, Bareggi R, Narducci P, Martelli AM. Phosphoinositide-specific phospholipase Cbeta1 expression is not linked to nerve growth factor-induced differentiation, cell survival or cell cycle control in PC12 rat pheocromocytoma cells. J Cell Biochem 2002; 84:56-67. [PMID: 11746516 DOI: 10.1002/jcb.1266] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Recent reports have highlighted that phosphoinositide-specific phospholipase Cbeta1 expression is linked to neuronal differentiation in different experimental models. We sought to determine whether or not this is also true for nerve growth factor (NGF)-induced neuronal differentiation of rat PC12 cells. However, we did not find differences in the expression of both the forms of phosphoinositide-specific phospholipase Cbeta1 (a and b) during sympathetic differentiation of these cells. Also, PC12 cell clones stably overexpressing phosphoinositide-specific phospholipase Cbeta1 were not more susceptible to the differentiating effect of NGF. Furthermore, since it is well established that phosphoinositide-specific phospholipase Cbeta1 affects cell proliferation, we investigated whether or not PC12 cell clones stably overexpressing phosphoinositide-specific phospholipase Cbeta1 showed differences in survival to serum deprivation and cell cycle, when compared to wild type cells. Nevertheless, we did not find any differences in these parameters between wild type cells and the overexpressing clones. Interestingly, in PC12 cells the overexpressed phosphoinositide-specific phospholipase Cbeta1 did not localize to the nucleus, but by immunofluorescence analysis, was detected in the cytoplasm. Therefore, our findings may represent another important clue to the fact that only when it is located within the nucleus phosphoinositide-specific phospholipase Cbeta1 is able to influence cell proliferation.
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Affiliation(s)
- R Bortul
- Dipartimento di Morfologia Umana Normale, Università di Trieste, via Manzoni 16, 34138 Trieste, Italy
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28
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Luca G, Calafiore R, Basta G, Ricci M, Calvitti M, Neri L, Nastruzzi C, Becchetti E, Capitani S, Brunetti P, Rossi C. Improved function of rat islets upon co-microencapsulation with Sertoli's cells in alginate/poly-L-ornithine. AAPS PharmSciTech 2001; 2:E15. [PMID: 14727874 PMCID: PMC2750580 DOI: 10.1208/pt020315] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2001] [Accepted: 08/02/2001] [Indexed: 01/12/2023] Open
Abstract
The purpose of this study was to assess whether Sertoli's cells would improve functional performance of homologous pancreatic islets within microcapsules. Purified rat Sertoli's cells were co-enveloped with islets in microcapsules that had been fabricated with alginic acid and poly-L-ornithine. Confocal laser microscopy was used to determine any mitogenic effects of Sertoli's cells on islets beta-cells. Insulin secretion from islets, with or without Sertoli's cells, was examined, and grafts of Sertoli's cells with islets in microcapsules into diabetic mice were carried out. Co-incubation of Sertoli's cells with islets resulted in a significant increase in the islet beta-cell mitotic rate, which was coupled with significantly higher insulin release under glucose stimulation, as compared to controls. Grafts of co-microencapsulated Sertoli's cells with islets resulted in prolongation of the achieved normoglycemia in the animals receiving Sertoli's cells with islets as compared to controls that received islets only. Sertoli's cells do promote mitogenic activities upon in vitro co-incubation with islets, whose in vitro functional and in vivo post-transplant consequences were evident. Sertoli's cells could, therefore, be co-microencapsulated with islets for transplantation in diabetic recipients.
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Affiliation(s)
- G Luca
- Department of Chemistry and Pharmaceutical Technology of Drugs, University of Perugia, Perugia, Italy.
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29
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Biondi C, Pavan B, Ferretti ME, Corradini FG, Neri LM, Vesce F. Formyl-methionyl-leucyl-phenylalanine induces prostaglandin E2 release from human amnion-derived WISH cells by phospholipase C-mediated [Ca+]i rise. Biol Reprod 2001; 64:865-70. [PMID: 11207202 DOI: 10.1095/biolreprod64.3.865] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The presence of binding sites for formyl-methionyl-leucyl-phenylalanine (fMLP), its effect on prostaglandin E (PGE) release, and the signal transduction pathway activated by the peptide were investigated in human amnion-derived WISH cells. Our results demonstrate that specific binding sites for fMLP are present on WISH cells and that the peptide induces a significant increase of prostaglandin (PG)E2 release. The kinetic properties of binding are similar to those previously found in amnion tissue prior to the onset of labor, i.e., only one population of binding sites with low affinity for the peptide is present. Binding of 3H-fMLP in WISH cells is inhibited by N-t-butoxycarbonyl-methionyl-leucyl-phenylalanine, an fMLP receptor antagonist, with an IC50 value very close to that shown by nonlaboring amnion. The fMLP-induced PGE2 output is inhibited by indomethacin, quinacrine, and U-73122, inhibitors of cyclooxygenase, phospholipase A2, and phospholipase C, respectively. As regards the transduction pathway activated by fMLP, we demonstrate that phospholipase C activation, followed by an increase of intracellular calcium concentration ([Ca2+]i), is involved in response to the peptide. Our results add further evidence to the role of proinflammatory agents in the determination of labor. Furthermore, because WISH cells appear to behave like nonlaboring amnion tissue, they represent the ideal candidate for in vitro investigation of the events triggering the mechanism of delivery.
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Affiliation(s)
- C Biondi
- Department of Biology, Section of General Physiology, University of Ferrara, 44100-I Ferrara, Italy.
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30
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Sabatelli P, Lattanzi G, Ognibene A, Columbaro M, Capanni C, Merlini L, Maraldi NM, Squarzoni S. Nuclear alterations in autosomal-dominant Emery-Dreifuss muscular dystrophy. Muscle Nerve 2001; 24:826-9. [PMID: 11360268 DOI: 10.1002/mus.1076] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Electron microscopy study of muscle biopsies from patients with autosomal-dominant Emery-Dreifuss muscular dystrophy revealed nuclear alterations in about 10% of the preserved muscle fibers. The major findings consisted of peripheral heterochromatin loss or detachment from the nuclear envelope, and of interchromatin texture alterations. These abnormalities are similar to those reported in an animal model of the disease and to those found in the X-linked form of Emery-Dreifuss muscular dystrophy. These results suggest that an abnormal ultrastructural arrangement of the nuclear periphery is a common feature in the known forms of Emery-Dreifuss muscular dystrophy, and that several proteins of the nuclear scaffold are necessary in muscle cells to maintain the nuclear structural/functional integrity and a normal muscle cell metabolism.
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Affiliation(s)
- P Sabatelli
- Istituto di Citomorfologia, Consiglio Nazionale delle Ricerche, via Di Barbiano 1/10 c/o Istituti Ortopedici Rizzoli, 40136 Bologna, Italy
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31
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Moir RD, Yoon M, Khuon S, Goldman RD. Nuclear lamins A and B1: different pathways of assembly during nuclear envelope formation in living cells. J Cell Biol 2000; 151:1155-68. [PMID: 11121432 PMCID: PMC2190592 DOI: 10.1083/jcb.151.6.1155] [Citation(s) in RCA: 289] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/1999] [Accepted: 10/06/2000] [Indexed: 01/31/2023] Open
Abstract
At the end of mitosis, the nuclear lamins assemble to form the nuclear lamina during nuclear envelope formation in daughter cells. We have fused A- and B-type nuclear lamins to the green fluorescent protein to study this process in living cells. The results reveal that the A- and B-type lamins exhibit different pathways of assembly. In the early stages of mitosis, both lamins are distributed throughout the cytoplasm in a diffusible (nonpolymerized) state, as demonstrated by fluorescence recovery after photobleaching (FRAP). During the anaphase-telophase transition, lamin B1 begins to become concentrated at the surface of the chromosomes. As the chromosomes reach the spindle poles, virtually all of the detectable lamin B1 has accumulated at their surfaces. Subsequently, this lamin rapidly encloses the entire perimeter of the region containing decondensing chromosomes in each daughter cell. By this time, lamin B1 has assembled into a relatively stable polymer, as indicated by FRAP analyses and insolubility in detergent/high ionic strength solutions. In contrast, the association of lamin A with the nucleus begins only after the major components of the nuclear envelope including pore complexes are assembled in daughter cells. Initially, lamin A is found in an unpolymerized state throughout the nucleoplasm of daughter cell nuclei in early G1 and only gradually becomes incorporated into the peripheral lamina during the first few hours of this stage of the cell cycle. In later stages of G1, FRAP analyses suggest that both green fluorescent protein lamins A and B1 form higher order polymers throughout interphase nuclei.
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Affiliation(s)
- Robert D. Moir
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
| | - Miri Yoon
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
| | - Satya Khuon
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
| | - Robert D. Goldman
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
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32
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Abstract
Chromatin insulators might regulate gene expression by controlling the subnuclear organization of DNA. We found that a DNA sequence normally located inside of the nucleus moved to the periphery when the gypsy insulator was placed within the sequence. The presence of the gypsy insulator also caused two sequences, normally found in different regions of the nucleus, to come together at a single location. Alterations in this subnuclear organization imposed by the gypsy insulator correlated with changes in gene expression that took place during the heat-shock response. These global changes in transcription were accompanied by dramatic alterations in the distribution of insulator proteins and DNA. The results suggest that the nuclear organization imposed by the gypsy insulator on the chromatin fiber is important for gene expression.
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Affiliation(s)
- T I Gerasimova
- Department of Biology The Johns Hopkins University, Baltimore, MD 21218, USA
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33
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Dechat T, Korbei B, Vaughan OA, Vlcek S, Hutchison CJ, Foisner R. Lamina-associated polypeptide 2alpha binds intranuclear A-type lamins. J Cell Sci 2000; 113 Pt 19:3473-84. [PMID: 10984438 DOI: 10.1242/jcs.113.19.3473] [Citation(s) in RCA: 167] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The nucleoskeletal protein lamina-associated polypeptide 2(α) (LAP2*) contains a large, unique C terminus and differs significantly from its alternatively spliced, mostly membrane-integrated isoforms, such as LAP2beta. Unlike lamin B-binding LAP2beta, LAP2alpha was found by confocal immunofluorescence microscopy to colocalize preferentially with A-type lamins in the newly formed nuclei assembled after mitosis. While only a subfraction of lamins A and C (lamin A/C) was associated with the predominantly nuclear LAP2alpha in telophase, the majority of lamin A/C colocalized with LAP2alpha in G(1)-phase nuclei. Furthermore, selective disruption of A-type lamin structures by overexpression of lamin mutants in HeLa cells caused a redistribution of LAP2alpha. Coimmunoprecipitation experiments revealed that a fraction of lamin A/C formed a stable, SDS-resistant complex with LAP2alpha in interphase cells and in postmetaphase cell extracts. Blot overlay binding studies revealed a direct binding of LAP2alpha to exclusively A-type lamins and located the interaction domains to the C-terminal 78 amino acids of LAP2alpha and to residues 319–566 in lamin A/C, which include the C terminus of the rod and the entire tail common to lamin A/C. These findings suggest that LAP2alpha and A-type lamins cooperate in the organization of internal nuclear structures.
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Affiliation(s)
- T Dechat
- Department of Biochemistry and Molecular Cell Biology, Vienna Biocenter, University of Vienna, A-1030 Vienna, Austria
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34
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Martelli AM, Borgatti P, Bortul R, Manfredini M, Massari L, Capitani S, Neri LM. Phosphatidylinositol 3-kinase translocates to the nucleus of osteoblast-like MC3T3-E1 cells in response to insulin-like growth factor I and platelet-derived growth factor but not to the proapoptotic cytokine tumor necrosis factor alpha. J Bone Miner Res 2000; 15:1716-30. [PMID: 10976992 DOI: 10.1359/jbmr.2000.15.9.1716] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Changes in the metabolism of nuclear inositides phosphorylated in the D3 position of the inositol ring, which may act as second messengers, mainly have been linked to cell differentiation. To clarify a possible role of this peculiar class of inositides also during cell proliferation and/or apoptosis, we have examined the issue of whether or not in the osteoblast-like clonal cell line MC3T3-E1 it may be observed an insulin-like growth factor-I (IGF-I)- and platelet-derived growth factor (PDGF)-dependent nuclear translocation of an active phosphatidylinositol 3-kinase (PI 3-K). We found that both the growth factors increased rapidly and transiently both the amount and the activity of immunoprecipitable nuclear PI 3-K. Intranuclear PI 3-K exhibited a massive tyrosine phosphorylation on the p85 regulatory subunit. Moreover, by means of coimmunoprecipitation experiments, we showed the presence, in isolated nuclei, of the p110beta catalytic subunit of PI 3-K. Enzyme translocation was blocked by the specific PI 3-K inhibitor LY294002. In contrast, intranuclear translocation of PI 3-K did not occur in response to the proapoptotic cytokine tumor necrosis factor alpha (TNF-alpha). IGF-I was able to counteract the apoptotic stimulus of TNF-alpha and this was accompanied by the intranuclear translocation of PI 3-K. LY294002 inhibited both intranuclear translocation of PI 3-K and the rescuing effect of IGF-I. These findings strongly suggest that an important step in the signaling pathways that mediate both cell proliferation and survival is represented by the intranuclear translocation of PI 3-K.
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Affiliation(s)
- A M Martelli
- Dipartimento di Morfologia Umana Normale, Università di Trieste, Italy
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35
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Borgatti P, Martelli AM, Bellacosa A, Casto R, Massari L, Capitani S, Neri LM. Translocation of Akt/PKB to the nucleus of osteoblast-like MC3T3-E1 cells exposed to proliferative growth factors. FEBS Lett 2000; 477:27-32. [PMID: 10899305 DOI: 10.1016/s0014-5793(00)01758-0] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
An active phosphatidylinositol 3-kinase (PI3K) has been shown in nuclei of different cell types. The products of this enzyme, i.e. inositides phosphorylated in the D3 position of the inositol ring, may act as second messengers themselves. Nuclear PI3K translocation has been demonstrated to be related to an analogous translocation of a PtdIns(3,4,5)P(3) activated PKC, the zeta isozyme. We have examined the issue of whether or not in the osteoblast-like clonal cell line MC3T3-E1 there may be observed an insulin-like growth factor-I- (IGF-I) and platelet-derived growth factor- (PDGF) dependent nuclear translocation of an active Akt/PKB. Western blot analysis showed a maximal nuclear translocation after 20 min of IGF-I stimulation or after 30 min of PDGF treatment. Both growth factors increased rapidly and transiently the enzyme activity of immunoprecipitable nuclear Akt/PKB on a similar time scale and after 60 min the values were slightly higher than the basal levels. Enzyme translocation was blocked by the specific PI3K inhibitor, LY294002, as well as cell entry into S-phase. Confocal microscopy showed an evident increase in immunostaining intensity in the nuclear interior after growth factor treatment but no changes in the subcellular distribution of Akt/PKB when a LY294002 pre-treatment was administered to the cells. These findings strongly suggest that the intranuclear translocation of Akt/PKB is an important step in signalling pathways that mediate cell proliferation.
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Affiliation(s)
- P Borgatti
- Dipartmento di Morfologia ed Embriologia, Sezione di Anatomia Umana, Universitá di Ferrara, Via Fossata di Mortara 66, 44100 Ferrara, Italy
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36
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Moir RD, Spann TP, Herrmann H, Goldman RD. Disruption of nuclear lamin organization blocks the elongation phase of DNA replication. J Cell Biol 2000; 149:1179-92. [PMID: 10851016 PMCID: PMC2175110 DOI: 10.1083/jcb.149.6.1179] [Citation(s) in RCA: 168] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/1999] [Accepted: 05/01/2000] [Indexed: 11/22/2022] Open
Abstract
The role of nuclear lamins in DNA replication is unclear. To address this, nuclei were assembled in Xenopus extracts containing AraC, a reversible inhibitor that blocks near the onset of the elongation phase of replication. Dominant-negative lamin mutants lacking their NH(2)-terminal domains were added to assembled nuclei to disrupt lamin organization. This prevented the resumption of DNA replication after the release of the AraC block. This inhibition of replication was not due to gross disruption of nuclear envelope structure and function. The organization of initiation factors was not altered by lamin disruption, and nuclei resumed replication when transferred to extracts treated with CIP, an inhibitor of the cyclin-dependent kinase (cdk) 2-dependent step of initiation. This suggests that alteration of lamin organization does not affect the initiation phase of DNA replication. Instead, we find that disruption of lamin organization inhibited chain elongation in a dose-dependent fashion. Furthermore, the established organization of two elongation factors, proliferating cell nuclear antigen, and replication factor complex, was disrupted by DeltaNLA. These findings demonstrate that lamin organization must be maintained in nuclei for the elongation phase of DNA replication to proceed.
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Affiliation(s)
- Robert D. Moir
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
| | - Timothy P. Spann
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
| | - Harald Herrmann
- Division of Cell Biology, German Cancer Research Center, D-69120 Heidelberg, Germany
| | - Robert D. Goldman
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
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37
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Dechat T, Vlcek S, Foisner R. Review: lamina-associated polypeptide 2 isoforms and related proteins in cell cycle-dependent nuclear structure dynamics. J Struct Biol 2000; 129:335-45. [PMID: 10806084 DOI: 10.1006/jsbi.2000.4212] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The lamina-associated polypeptide (LAP) 2 family comprises up to six alternatively spliced proteins in mammalian cells and three isoforms in Xenopus. LAP2beta is a type II integral protein of the inner nuclear membrane, which binds to lamin B and the chromosomal protein BAF, and may link the nuclear membrane to the underlying lamina and provide docking sites for chromatin. LAP2alpha shares only the N-terminus with the other isoforms and contains a unique C-terminus. It is a nonmembrane protein associated with the nucleoskeleton and may help to organize higher order chromatin structure by interacting with A-lamins and chromosomes. Recent studies using mutant proteins have just begun to unravel functions of LAP2 isoforms during postmitotic nuclear reassembly. LAP2alpha associates with chromosomes via an alpha-specific domain at early stages of assembly, possibly providing a structural framework for chromosome reorganization. The subsequent interaction of both LAP2alpha and LAP2beta with the chromosomal BAF may stabilize chromatin structure and target membranes to the chromosomes. At later stages LAP2 may regulate the assembly of lamins. LAP2 isoforms have been found to share a homologous approximately 40 amino acid long region, the LEM domain, with nuclear membrane proteins MAN1 and emerin, which has been implicated in Emery-Dreifuss muscular dystrophy.
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Affiliation(s)
- T Dechat
- Department of Biochemistry and Molecular Cell Biology, Biocenter, Vienna, A-1030, Austria
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38
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Abstract
A cell fraction that would today be termed "the nuclear matrix" was first described and patented in 1948 by Russian investigators. In 1974 this fraction was rediscovered and promoted as a fundamental organizing principle of eukaryotic gene expression. Yet, convincing evidence for this functional role of the nuclear matrix has been elusive and has recently been further challenged. What do we really know about the nonchromatin elements (if any) of internal nuclear structure? Are there objective reasons (as opposed to thinly veiled disdain) to question experiments that use harsh nuclear extraction steps and precipitation-prone conditions? Are the known biophysical properties of the nucleoplasm in vivo consistent with the existence of an extensive network of anastomosing filaments coursing dendritically throughout the interchromatin space? To what extent may the genome itself contribute information for its own quarternary structure in the interphase nucleus? These questions and recent work that bears on the mystique of the nuclear matrix are addressed in this essay. The degree to which gene expression literally depends on nonchromatin nuclear structure as a facilitating organizational format remains an intriguing but unsolved issue in eukaryotic cell biology, and considerable skepticism continues to surround the nuclear matrix fraction as an accurate representation of the in vivo situation.
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Affiliation(s)
- T Pederson
- Department of Biochemistry and Molecular Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
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39
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Broers JL, Machiels BM, van Eys GJ, Kuijpers HJ, Manders EM, van Driel R, Ramaekers FC. Dynamics of the nuclear lamina as monitored by GFP-tagged A-type lamins. J Cell Sci 1999; 112 ( Pt 20):3463-75. [PMID: 10504295 DOI: 10.1242/jcs.112.20.3463] [Citation(s) in RCA: 172] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The behavior of chimeric proteins consisting of A-type lamins and green fluorescent protein (GFP) was studied to investigate the localization and dynamics of nuclear lamins in living cells. Cell line CHO-K1 was transfected with cDNA constructs encoding fusion proteins of lamin A-GFP, lamin Adelta10-GFP, or lamin C-GFP. In the interphase nucleus lamin-GFP fluorescence showed a perinuclear localization and incorporation into the lamina for all three constructs. Our findings show for the first time that the newly discovered lamin A 10 protein is localized to the nuclear membrane. The GFP-tagged lamins were processed and behaved similarly to the endogenous lamin molecules, at least in cells that expressed physiological levels of the GFP-lamins. In addition to the typical perinuclear localization, in the majority of transfected cells each individual A-type lamin-GFP revealed an extensive collection of branching intra- and trans-nuclear tubular structures, which showed a clear preference for a vertical orientation. Time-lapse studies of 3-D reconstructed interphase cells showed a remarkable stability in both number and location of these structures over time, while the lamina showed considerable dynamic movements, consisting of folding and indentation of large parts of the lamina. Fluorescence recovery after bleaching studies revealed a low protein turnover of both tubular and lamina-associated lamins. Repetitive bleaching of intranuclear areas revealed the presence of an insoluble intranuclear fraction of A-type lamins. Time-lapse studies of mitotic cells showed that reformation of the lamina and the tubular structures consisting of A-type lamins did not occur until after cytokinesis was completed.
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Affiliation(s)
- J L Broers
- Department of Molecular Cell Biology and Genetics, University of Maastricht, PO Box 616, The Netherlands.
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40
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Neri LM, Raymond Y, Giordano A, Borgatti P, Marchisio M, Capitani S, Martelli AM. Spatial distribution of lamin A and B1 in the K562 cell nuclear matrix stabilized with metal ions. J Cell Biochem 1999. [DOI: 10.1002/(sici)1097-4644(19991001)75:1<36::aid-jcb4>3.0.co;2-r] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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