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Abstract
Lamins are evolutionarily conserved nuclear intermediate filament proteins. They provide structural support for the nucleus and help regulate many other nuclear activities. Mutations in human lamin genes, and especially in the LMNA gene, cause numerous diseases, termed laminopathies, including muscle, cardiac, metabolic, neuronal and early aging diseases. Most laminopathies arise from autosomal dominant missense mutations. Many of the mutant residues are conserved in the lamin genes of the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Our current understanding of the mechanisms leading to these diseases is mostly based on patients cell lines and animal models including C. elegans and D. melanogaster. The simpler lamin system and the powerful genetic tools offered by these invertebrate organisms greatly contributed to such studies. Here we provide an overview of the studies of laminopathies in Drosophila and C. elegans models.
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Affiliation(s)
- Ryszard Rzepecki
- a Laboratory of Nuclear Proteins, Faculty of Biotechnology , University of Wroclaw , Fryderyka Joliot-Curie, Wroclaw , Poland
| | - Yosef Gruenbaum
- a Laboratory of Nuclear Proteins, Faculty of Biotechnology , University of Wroclaw , Fryderyka Joliot-Curie, Wroclaw , Poland.,b Department of Genetics , Institute of Life Sciences, Hebrew University of Jerusalem , Jerusalem , Israel
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Machowska M, Piekarowicz K, Rzepecki R. Regulation of lamin properties and functions: does phosphorylation do it all? Open Biol 2016; 5:rsob.150094. [PMID: 26581574 PMCID: PMC4680568 DOI: 10.1098/rsob.150094] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The main functions of lamins are their mechanical and structural roles as major building blocks of the karyoskeleton. They are also involved in chromatin structure regulation, gene expression, intracellular signalling pathway modulation and development. All essential lamin functions seem to depend on their capacity for assembly or disassembly after the receipt of specific signals, and after specific, selective and precisely regulated interactions through their various domains. Reversible phosphorylation of lamins is crucial for their functions, so it is important to understand how lamin polymerization and interactions are modulated, and which sequences may undergo such modifications. This review combines experimental data with results of our in silico analyses focused on lamin phosphorylation in model organisms to show the presence of evolutionarily conserved sequences and to indicate specific in vivo phosphorylations that affect particular functions.
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Affiliation(s)
- Magdalena Machowska
- Laboratory of Nuclear Proteins, Faculty of Biotechnology, University of Wrocław, ul. Fryderyka Joliot-Curie 14a, Wrocław 50-383, Poland
| | - Katarzyna Piekarowicz
- Laboratory of Nuclear Proteins, Faculty of Biotechnology, University of Wrocław, ul. Fryderyka Joliot-Curie 14a, Wrocław 50-383, Poland
| | - Ryszard Rzepecki
- Laboratory of Nuclear Proteins, Faculty of Biotechnology, University of Wrocław, ul. Fryderyka Joliot-Curie 14a, Wrocław 50-383, Poland
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3
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The effect of the lamin A and its mutants on nuclear structure, cell proliferation, protein stability, and mobility in embryonic cells. Chromosoma 2016; 126:501-517. [PMID: 27534416 PMCID: PMC5509783 DOI: 10.1007/s00412-016-0610-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Revised: 07/11/2016] [Accepted: 08/02/2016] [Indexed: 01/26/2023]
Abstract
LMNA gene encodes for nuclear intermediate filament proteins lamin A/C. Mutations in this gene lead to a spectrum of genetic disorders, collectively referred to as laminopathies. Lamin A/C are widely expressed in most differentiated somatic cells but not in early embryos and some undifferentiated cells. To investigate the role of lamin A/C in cell phenotype maintenance and differentiation, which could be a determinant of the pathogenesis of laminopathies, we examined the role played by exogenous lamin A and its mutants in differentiated cell lines (HeLa, NHDF) and less-differentiated HEK 293 cells. We introduced exogenous wild-type and mutated (H222P, L263P, E358K D446V, and ∆50) lamin A into different cell types and analyzed proteins’ impact on proliferation, protein mobility, and endogenous nuclear envelope protein distribution. The mutants give rise to a broad spectrum of nuclear phenotypes and relocate lamin C. The mutations ∆50 and D446V enhance proliferation in comparison to wild-type lamin A and control cells, but no changes in exogenous protein mobility measured by FRAP were observed. Interestingly, although transcripts for lamins A and C are at similar level in HEK 293 cells, only lamin C protein is detected in western blots. Also, exogenous lamin A and its mutants, when expressed in HEK 293 cells underwent posttranscriptional processing. Overall, our results provide new insight into the maintenance of lamin A in less-differentiated cells. Embryonic cells are very sensitive to lamin A imbalance, and its upregulation disturbs lamin C, which may influence gene expression and many regulatory pathways.
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Czapiewski R, Robson MI, Schirmer EC. Anchoring a Leviathan: How the Nuclear Membrane Tethers the Genome. Front Genet 2016; 7:82. [PMID: 27200088 PMCID: PMC4859327 DOI: 10.3389/fgene.2016.00082] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 04/20/2016] [Indexed: 12/21/2022] Open
Abstract
It is well established that the nuclear envelope has many distinct direct connections to chromatin that contribute to genome organization. The functional consequences of genome organization on gene regulation are less clear. Even less understood is how interactions of lamins and nuclear envelope transmembrane proteins (NETs) with chromatin can produce anchoring tethers that can withstand the physical forces of and on the genome. Chromosomes are the largest molecules in the cell, making megadalton protein structures like the nuclear pore complexes and ribosomes seem small by comparison. Thus to withstand strong forces from chromosome dynamics an anchoring tether is likely to be much more complex than a single protein-protein or protein-DNA interaction. Here we will briefly review known NE-genome interactions that likely contribute to spatial genome organization, postulate in the context of experimental data how these anchoring tethers contribute to gene regulation, and posit several hypotheses for the physical nature of these tethers that need to be investigated experimentally. Significantly, disruption of these anchoring tethers and the subsequent consequences for gene regulation could explain how mutations in nuclear envelope proteins cause diseases ranging from muscular dystrophy to lipodystrophy to premature aging progeroid syndromes. The two favored hypotheses for nuclear envelope protein involvement in disease are (1) weakening nuclear and cellular mechanical stability, and (2) disrupting genome organization and gene regulation. Considerable experimental support has been obtained for both. The integration of both mechanical and gene expression defects in the disruption of anchoring tethers could provide a unifying hypothesis consistent with both.
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Affiliation(s)
| | | | - Eric C. Schirmer
- The Wellcome Trust Centre for Cell Biology and Institute of Cell Biology, University of EdinburghEdinburgh, UK
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5
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Kinney NA, Sharakhov IV, Onufriev AV. Investigation of the chromosome regions with significant affinity for the nuclear envelope in fruit fly--a model based approach. PLoS One 2014; 9:e91943. [PMID: 24651400 PMCID: PMC3961273 DOI: 10.1371/journal.pone.0091943] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 02/18/2014] [Indexed: 12/16/2022] Open
Abstract
Three dimensional nuclear architecture is important for genome function, but is still poorly understood. In particular, little is known about the role of the “boundary conditions” – points of attachment between chromosomes and the nuclear envelope. We describe a method for modeling the 3D organization of the interphase nucleus, and its application to analysis of chromosome-nuclear envelope (Chr-NE) attachments of polytene (giant) chromosomes in Drosophila melanogaster salivary glands. The model represents chromosomes as self-avoiding polymer chains confined within the nucleus; parameters of the model are taken directly from experiment, no fitting parameters are introduced. Methods are developed to objectively quantify chromosome territories and intertwining, which are discussed in the context of corresponding experimental observations. In particular, a mathematically rigorous definition of a territory based on convex hull is proposed. The self-avoiding polymer model is used to re-analyze previous experimental data; the analysis suggests 33 additional Chr-NE attachments in addition to the 15 already explored Chr-NE attachments. Most of these new Chr-NE attachments correspond to intercalary heterochromatin – gene poor, dark staining, late replicating regions of the genome; however, three correspond to euchromatin – gene rich, light staining, early replicating regions of the genome. The analysis also suggests 5 regions of anti-contact, characterized by aversion for the NE, only two of these correspond to euchromatin. This composition of chromatin suggests that heterochromatin may not be necessary or sufficient for the formation of a Chr-NE attachment. To the extent that the proposed model represents reality, the confinement of the polytene chromosomes in a spherical nucleus alone does not favor the positioning of specific chromosome regions at the NE as seen in experiment; consequently, the 15 experimentally known Chr-NE attachment positions do not appear to arise due to non-specific (entropic) forces. Robustness of the key conclusions to model assumptions is thoroughly checked.
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Affiliation(s)
- Nicholas Allen Kinney
- Genomics Bioinformatics and Computational Biology, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Igor V. Sharakhov
- Department of Entomology, Virginia Tech, Blacksburg, Virginia, United States of America
- * E-mail: (IVS); (AVO)
| | - Alexey V. Onufriev
- Department of Physics, Virginia Tech, Blacksburg, Virginia, United States of America
- Department of Computer Science, Virginia Tech, Blacksburg, Virginia, United States of America
- * E-mail: (IVS); (AVO)
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6
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Stancheva I, Schirmer EC. Nuclear Envelope: Connecting Structural Genome Organization to Regulation of Gene Expression. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 773:209-44. [DOI: 10.1007/978-1-4899-8032-8_10] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Dubinska-Magiera M, Zaremba-Czogalla M, Rzepecki R. Muscle development, regeneration and laminopathies: how lamins or lamina-associated proteins can contribute to muscle development, regeneration and disease. Cell Mol Life Sci 2012; 70:2713-41. [PMID: 23138638 PMCID: PMC3708280 DOI: 10.1007/s00018-012-1190-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 09/28/2012] [Accepted: 10/03/2012] [Indexed: 12/22/2022]
Abstract
The aim of this review article is to evaluate the current knowledge on associations between muscle formation and regeneration and components of the nuclear lamina. Lamins and their partners have become particularly intriguing objects of scientific interest since it has been observed that mutations in genes coding for these proteins lead to a wide range of diseases called laminopathies. For over the last 10 years, various laboratories worldwide have tried to explain the pathogenesis of these rare disorders. Analyses of the distinct aspects of laminopathies resulted in formulation of different hypotheses regarding the mechanisms of the development of these diseases. In the light of recent discoveries, A-type lamins—the main building blocks of the nuclear lamina—together with other key elements, such as emerin, LAP2α and nesprins, seem to be of great importance in the modulation of various signaling pathways responsible for cellular differentiation and proliferation.
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Affiliation(s)
- Magda Dubinska-Magiera
- Department of Animal Developmental Biology, University of Wroclaw, 21 Sienkiewicza Street, 50-335, Wroclaw, Poland
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8
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Zaremba-Czogalla M, Piekarowicz K, Wachowicz K, Kozioł K, Dubińska-Magiera M, Rzepecki R. The different function of single phosphorylation sites of Drosophila melanogaster lamin Dm and lamin C. PLoS One 2012; 7:e32649. [PMID: 22393432 PMCID: PMC3290585 DOI: 10.1371/journal.pone.0032649] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 01/28/2012] [Indexed: 11/18/2022] Open
Abstract
Lamins' functions are regulated by phosphorylation at specific sites but our understanding of the role of such modifications is practically limited to the function of cdc 2 (cdk1) kinase sites in depolymerization of the nuclear lamina during mitosis. In our study we used Drosophila lamin Dm (B-type) to examine the function of particular phosphorylation sites using pseudophosphorylated mutants mimicking single phosphorylation at experimentally confirmed in vivo phosphosites (S(25)E, S(45)E, T(435)E, S(595)E). We also analyzed lamin C (A-type) and its mutant S(37)E representing the N-terminal cdc2 (mitotic) site as well as lamin Dm R(64)H mutant as a control, non-polymerizing lamin. In the polymerization assay we could observe different effects of N-terminal cdc2 site pseudophosphorylation on A- and B-type lamins: lamin Dm S(45)E mutant was insoluble, in contrast to lamin C S(37)E. Lamin Dm T(435)E (C-terminal cdc2 site) and R(64)H were soluble in vitro. We also confirmed that none of the single phosphorylation site modifications affected the chromatin binding of lamin Dm, in contrast to the lamin C N-terminal cdc2 site. In vivo, all lamin Dm mutants were incorporated efficiently into the nuclear lamina in transfected Drosophila S2 and HeLa cells, although significant amounts of S(45)E and T(435)E were also located in cytoplasm. When farnesylation incompetent mutants were expressed in HeLa cells, lamin Dm T(435)E was cytoplasmic and showed higher mobility in FRAP assay.
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Affiliation(s)
| | | | | | | | | | - Ryszard Rzepecki
- Laboratory of Nuclear Proteins, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
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9
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Abstract
In the past 15 years our perception of nuclear envelope function has evolved perhaps nearly as much as the nuclear envelope itself evolved in the last 3 billion years. Historically viewed as little more than a diffusion barrier between the cytoplasm and the nucleoplasm, the nuclear envelope is now known to have roles in the cell cycle, cytoskeletal stability and cell migration, genome architecture, epigenetics, regulation of transcription, splicing, and DNA replication. Here we will review both what is known and what is speculated about the role of the nuclear envelope in genome organization, particularly with respect to the positioning and repositioning of genes and chromosomes within the nucleus during differentiation.
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Affiliation(s)
- Nikolaj Zuleger
- The Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, EH9 3JR, UK
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10
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Embryonic and adult isoforms of XLAP2 form microdomains associated with chromatin and the nuclear envelope. Cell Tissue Res 2011; 344:97-110. [PMID: 21347574 PMCID: PMC3112025 DOI: 10.1007/s00441-011-1129-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 01/12/2011] [Indexed: 11/10/2022]
Abstract
Laminin-associated polypeptide 2 (LAP2) proteins are alternatively spliced products of a single gene; they belong to the LEM domain family and, in mammals, locate to the nuclear envelope (NE) and nuclear lamina. Isoforms lacking the transmembrane domain also locate to the nucleoplasm. We used new specific antibodies against the N-terminal domain of Xenopus LAP2 to perform immunoprecipitation, identification and localization studies during Xenopus development. By immunoprecipitation and mass spectrometry (LC/MS/MS), we identified the embryonic isoform XLAP2γ, which was downregulated during development similarly to XLAP2ω. Embryonic isoforms XLAP2ω and XLAP2γ were located in close association with chromatin up to the blastula stage. Later in development, both embryonic isoforms and the adult isoform XLAP2β were localized in a similar way at the NE. All isoforms colocalized with lamin B2/B3 during development, whereas XLAP2β was colocalized with lamin B2 and apparently with the F/G repeat nucleoporins throughout the cell cycle in adult tissues and culture cells. XLAP2β was localized in clusters on chromatin, both at the NE and inside the nucleus. Embryonic isoforms were also localized in clusters at the NE of oocytes. Our results suggest that XLAP2 isoforms participate in the maintenance and anchoring of chromatin domains to the NE and in the formation of lamin B microdomains.
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Prokocimer M, Davidovich M, Nissim-Rafinia M, Wiesel-Motiuk N, Bar DZ, Barkan R, Meshorer E, Gruenbaum Y. Nuclear lamins: key regulators of nuclear structure and activities. J Cell Mol Med 2009; 13:1059-85. [PMID: 19210577 PMCID: PMC4496104 DOI: 10.1111/j.1582-4934.2008.00676.x] [Citation(s) in RCA: 201] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Accepted: 01/19/2009] [Indexed: 11/27/2022] Open
Abstract
The nuclear lamina is a proteinaceous structure located underneath the inner nuclear membrane (INM), where it associates with the peripheral chromatin. It contains lamins and lamin-associated proteins, including many integral proteins of the INM, chromatin modifying proteins, transcriptional repressors and structural proteins. A fraction of lamins is also present in the nucleoplasm, where it forms stable complexes and is associated with specific nucleoplasmic proteins. The lamins and their associated proteins are required for most nuclear activities, mitosis and for linking the nucleoplasm to all major cytoskeletal networks in the cytoplasm. Mutations in nuclear lamins and their associated proteins cause about 20 different diseases that are collectively called laminopathies'. This review concentrates mainly on lamins, their structure and their roles in DNA replication, chromatin organization, adult stem cell differentiation, aging, tumorogenesis and the lamin mutations leading to laminopathic diseases.
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Affiliation(s)
- Miron Prokocimer
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Maya Davidovich
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Malka Nissim-Rafinia
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Naama Wiesel-Motiuk
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Daniel Z Bar
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Rachel Barkan
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Eran Meshorer
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Yosef Gruenbaum
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of JerusalemJerusalem, Israel
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Dechat T, Adam SA, Goldman RD. Nuclear lamins and chromatin: when structure meets function. ADVANCES IN ENZYME REGULATION 2008; 49:157-66. [PMID: 19154754 PMCID: PMC3253622 DOI: 10.1016/j.advenzreg.2008.12.003] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Thomas Dechat
- Northwestern University Medical School, Department of Cell and Molecular Biology, Chicago, Illinois 60611, USA
| | - Stephen A. Adam
- Northwestern University Medical School, Department of Cell and Molecular Biology, Chicago, Illinois 60611, USA
| | - Robert D. Goldman
- Northwestern University Medical School, Department of Cell and Molecular Biology, Chicago, Illinois 60611, USA
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Rasala BA, Ramos C, Harel A, Forbes DJ. Capture of AT-rich chromatin by ELYS recruits POM121 and NDC1 to initiate nuclear pore assembly. Mol Biol Cell 2008; 19:3982-96. [PMID: 18596237 DOI: 10.1091/mbc.e08-01-0012] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Assembly of the nuclear pore, gateway to the genome, from its component subunits is a complex process. In higher eukaryotes, nuclear pore assembly begins with the binding of ELYS/MEL-28 to chromatin and recruitment of the large critical Nup107-160 pore subunit. The choreography of steps that follow is largely speculative. Here, we set out to molecularly define early steps in nuclear pore assembly, beginning with chromatin binding. Point mutation analysis indicates that pore assembly is exquisitely sensitive to the change of only two amino acids in the AT-hook motif of ELYS. The dependence on AT-rich chromatin for ELYS binding is borne out by the use of two DNA-binding antibiotics. AT-binding Distamycin A largely blocks nuclear pore assembly, whereas GC-binding Chromomycin A(3) does not. Next, we find that recruitment of vesicles containing the key integral membrane pore proteins POM121 and NDC1 to the forming nucleus is dependent on chromatin-bound ELYS/Nup107-160 complex, whereas recruitment of gp210 vesicles is not. Indeed, we reveal an interaction between the cytoplasmic domain of POM121 and the Nup107-160 complex. Our data thus suggest an order for nuclear pore assembly of 1) AT-rich chromatin sites, 2) ELYS, 3) the Nup107-160 complex, and 4) POM121- and NDC1-containing membrane vesicles and/or sheets, followed by (5) assembly of the bulk of the remaining soluble pore subunits.
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Affiliation(s)
- Beth A Rasala
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0347, USA
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Dechat T, Pfleghaar K, Sengupta K, Shimi T, Shumaker DK, Solimando L, Goldman RD. Nuclear lamins: major factors in the structural organization and function of the nucleus and chromatin. Genes Dev 2008; 22:832-53. [PMID: 18381888 PMCID: PMC2732390 DOI: 10.1101/gad.1652708] [Citation(s) in RCA: 718] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Over the past few years it has become evident that the intermediate filament proteins, the types A and B nuclear lamins, not only provide a structural framework for the nucleus, but are also essential for many aspects of normal nuclear function. Insights into lamin-related functions have been derived from studies of the remarkably large number of disease-causing mutations in the human lamin A gene. This review provides an up-to-date overview of the functions of nuclear lamins, emphasizing their roles in epigenetics, chromatin organization, DNA replication, transcription, and DNA repair. In addition, we discuss recent evidence supporting the importance of lamins in viral infections.
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Affiliation(s)
- Thomas Dechat
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA
| | - Katrin Pfleghaar
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA
| | - Kaushik Sengupta
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA
| | - Takeshi Shimi
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA
| | - Dale K. Shumaker
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA
| | - Liliana Solimando
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA
| | - Robert D. Goldman
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA
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15
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Salpingidou G, Rzepecki R, Kiseleva E, Lyon C, Lane B, Fusiek K, Golebiewska A, Drummond S, Allen T, Ellis JA, Smythe C, Goldberg MW, Hutchison CJ. NEP-A and NEP-B both contribute to nuclear pore formation in Xenopus eggs and oocytes. J Cell Sci 2008; 121:706-16. [PMID: 18270266 DOI: 10.1242/jcs.019968] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In vertebrates, the nuclear envelope (NE) assembles and disassembles during mitosis. As the NE is a complex structure consisting of inner and outer membranes, nuclear pore complexes (NPCs) and the nuclear lamina, NE assembly must be a controlled and systematic process. In Xenopus egg extracts, NE assembly is mediated by two distinct membrane vesicle populations, termed NEP-A and NEP-B. Here, we re-investigate how these two membrane populations contribute to NPC assembly. In growing stage III Xenopus oocytes, NPC assembly intermediates are frequently observed. High concentrations of NPC assembly intermediates always correlate with fusion of vesicles into preformed membranes. In Xenopus egg extracts, two integral membrane proteins essential for NPC assembly, POM121 and NDC1, are exclusively associated with NEP-B membranes. By contrast, a third integral membrane protein associated with the NPCs, gp210, associates only with NEP-A membranes. During NE assembly, fusion between NEP-A and NEP-B led to the formation of fusion junctions at which >65% of assembling NPCs were located. To investigate how each membrane type contributes to NPC assembly, we preferentially limited NEP-A in NE assembly assays. We found that, by limiting the NEP-A contribution to the NE, partially formed NPCs were assembled in which protein components of the nucleoplasmic face were depleted or absent. Our data suggest that fusion between NEP-A and NEP-B membranes is essential for NPC assembly and that, in contrast to previous reports, both membranes contribute to NPC assembly.
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Affiliation(s)
- Georgia Salpingidou
- Integrative Cell Biology Laboratories, School of Biological and Biomedical Sciences, The University of Durham, South Road, Durham DH1 3LE, UK
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16
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Girton JR, Johansen KM. Chromatin structure and the regulation of gene expression: the lessons of PEV in Drosophila. ADVANCES IN GENETICS 2008; 61:1-43. [PMID: 18282501 DOI: 10.1016/s0065-2660(07)00001-6] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Position-effect variegation (PEV) was discovered in 1930 in a study of X-ray-induced chromosomal rearrangements. Rearrangements that place euchromatic genes adjacent to a region of centromeric heterochromatin give a variegated phenotype that results from the inactivation of genes by heterochromatin spreading from the breakpoint. PEV can also result from P element insertions that place euchromatic genes into heterochromatic regions and rearrangements that position euchromatic chromosomal regions into heterochromatic nuclear compartments. More than 75 years of studies of PEV have revealed that PEV is a complex phenomenon that results from fundamental differences in the structure and function of heterochromatin and euchromatin with respect to gene expression. Molecular analysis of PEV began with the discovery that PEV phenotypes are altered by suppressor and enhancer mutations of a large number of modifier genes whose products are structural components of heterochromatin, enzymes that modify heterochromatic proteins, or are nuclear structural components. Analysis of these gene products has led to our current understanding that formation of heterochromatin involves specific modifications of histones leading to the binding of particular sets of heterochromatic proteins, and that this process may be the mechanism for repressing gene expression in PEV. Other modifier genes produce products whose function is part of an active mechanism of generation of euchromatin that resists heterochromatization. Current studies of PEV are focusing on defining the complex patterns of modifier gene activity and the sequence of events that leads to the dynamic interplay between heterochromatin and euchromatin.
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Affiliation(s)
- Jack R Girton
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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Dorner D, Gotzmann J, Foisner R. Nucleoplasmic lamins and their interaction partners, LAP2alpha, Rb, and BAF, in transcriptional regulation. FEBS J 2007; 274:1362-73. [PMID: 17489094 DOI: 10.1111/j.1742-4658.2007.05695.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lamins are major structural components of the nuclear envelope in multicellular eukaryotes. Particularly A-type lamins are also located in the nucleoplasm, likely involving a specific binding partner, lamina-associated polypeptide 2alpha (LAP2alpha). LAP2alpha-lamins A/C complexes in the nucleoplasm have been implicated in the regulation of gene expression by various means. They bind chromatin proteins and chromatin modifying enzymes, and can thus participate in epigenetic control pathways. Furthermore, binding of lamins A/C complexes to specific transcription factors and repressors may directly affect their transcriptional activity. LAP2alpha-lamins A/C also regulate retinoblastoma protein and influence cell cycle progression and differentiation, which could have important implications for molecular mechanisms of laminopathic diseases, linked to lamins A/C mutations.
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Affiliation(s)
- Daniela Dorner
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Dr. Bohrgasse 9/3, A-1030 Vienna, Austria
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18
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Mattout A, Goldberg M, Tzur Y, Margalit A, Gruenbaum Y. Specific and conserved sequences in D. melanogaster and C. elegans lamins and histone H2A mediate the attachment of lamins to chromosomes. J Cell Sci 2006; 120:77-85. [PMID: 17148572 DOI: 10.1242/jcs.03325] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The intimate association between nuclear lamins and chromatin is thought to regulate higher order chromatin organization. Previous studies have mapped a region between the rod domain and the Ig fold in the tail domain of Drosophila melanogaster lamin Dm0, which binds chromatin in vitro via the histone H2A/H2B dimer. This region contains an evolutionarily conserved nuclear localization signal (NLS) KRKR, and a sequence composed of the amino acids TRAT. Here we show that binding of lamin Dm0 to chromatin requires both NLS and TRAT sequences. Substituting either of the threonine residues in the TRAT sequence with negatively charged residues decreases the binding of lamin Dm0 to chromatin, indicating that this binding could be regulated by phosphorylation. Both lamin Dm0 and C. elegans Ce-lamin bind directly to histone H2A in vitro and this binding requires the NLS. The amino and carboxyl tail domains of histone H2A are each essential, but not sufficient, for binding to lamin Dm0; only a polypeptide containing both histone H2A tail domains binds efficiently to lamin Dm0. Taken together, these results suggest that specific residues in lamin Dm0 and histone H2A mediate the attachment of the nuclear lamina to chromosomes in vivo, which could have implications on the understanding of laminopathic diseases.
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Affiliation(s)
- Anna Mattout
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904 Israel
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19
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Haque F, Lloyd DJ, Smallwood DT, Dent CL, Shanahan CM, Fry AM, Trembath RC, Shackleton S. SUN1 interacts with nuclear lamin A and cytoplasmic nesprins to provide a physical connection between the nuclear lamina and the cytoskeleton. Mol Cell Biol 2006; 26:3738-51. [PMID: 16648470 PMCID: PMC1488999 DOI: 10.1128/mcb.26.10.3738-3751.2006] [Citation(s) in RCA: 386] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nuclear migration and positioning within cells are critical for many developmental processes and are governed by the cytoskeletal network. Although mechanisms of nuclear-cytoskeletal attachment are unclear, growing evidence links a novel family of nuclear envelope (NE) proteins that share a conserved C-terminal SUN (Sad1/UNC-84 homology) domain. Analysis of Caenorhabditis elegans mutants has implicated UNC-84 in actin-mediated nuclear positioning by regulating NE anchoring of a giant actin-binding protein, ANC-1. Here, we report the identification of SUN1 as a lamin A-binding protein in a yeast two-hybrid screen. We demonstrate that SUN1 is an integral membrane protein located at the inner nuclear membrane. While the N-terminal domain of SUN1 is responsible for detergent-resistant association with the nuclear lamina and lamin A binding, lamin A/C expression is not required for SUN1 NE localization. Furthermore, SUN1 does not interact with type B lamins, suggesting that NE localization is ensured by binding to an additional nuclear component(s), most likely chromatin. Importantly, we find that the luminal C-terminal domain of SUN1 interacts with the mammalian ANC-1 homologs nesprins 1 and 2 via their conserved KASH domain. Our data provide evidence of a physical nuclear-cytoskeletal connection that is likely to be a key mechanism in nuclear-cytoplasmic communication and regulation of nuclear position.
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Affiliation(s)
- Farhana Haque
- Department of Genetics, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
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20
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Maraldi NM, Lattanzi G, Capanni C, Columbaro M, Mattioli E, Sabatelli P, Squarzoni S, Manzoli FA. Laminopathies: A chromatin affair. ACTA ACUST UNITED AC 2006; 46:33-49. [PMID: 16857244 DOI: 10.1016/j.advenzreg.2006.01.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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21
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The M/SAR Elements of the bithorax Complex in Drosophila melanogaster. RUSS J GENET+ 2005. [DOI: 10.1007/s11177-005-0221-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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22
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Pang M, McConnell M, Fisher PA. The Drosophila mus 308 gene product, implicated in tolerance of DNA interstrand crosslinks, is a nuclear protein found in both ovaries and embryos. DNA Repair (Amst) 2005; 4:971-82. [PMID: 15961355 DOI: 10.1016/j.dnarep.2005.04.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2004] [Revised: 04/08/2005] [Accepted: 04/11/2005] [Indexed: 10/25/2022]
Abstract
mus 308 designates one of over 30 mutagen sensitivity loci found in Drosophila. It is predicted to code for a 229-kDa polypeptide. Published sequence analyses of others indicate that this polypeptide would have helicase motifs near its N-terminus, and similarities to bacterial DNA polymerase I-like enzymes near its C-terminus. In our studies, two different and highly specific antibodies were prepared and used for identification as well as characterization of the mus 308 gene product. Western blot analyses reveal a single reactive polypeptide in both ovaries and embryos as well as in two Drosophila embryo tissue culture cell lines; it is nearly absent in homozygous mus 308 mutants. This polypeptide is about 229 kDa in size, and indirect immunofluorescence shows that the mus 308 gene product localizes throughout nuclei in wild-type cells but appears to be absent in a mus 308 mutant. Immunoblot analyses throughout development suggest greatest abundance at the end of embryogenesis, immediately before hatching of first instar larvae. They also showed a smaller ( approximately 100 kDa) antigenically and genetically related polypeptide found only in adult males. Immunoprecipitation, a highly effective method of specific purification, suggests that the mus 308 protein has DNA polymerase activity that is NEM-sensitive but largely aphidicolin-resistant. In addition, the immunoprecipitated material has DNA-dependent ATPase but lacks detectable helicase.
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Affiliation(s)
- Maria Pang
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA
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23
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Schulze SR, Curio-Penny B, Li Y, Imani RA, Rydberg L, Geyer PK, Wallrath LL. Molecular genetic analysis of the nested Drosophila melanogaster lamin C gene. Genetics 2005; 171:185-96. [PMID: 15965247 PMCID: PMC1456510 DOI: 10.1534/genetics.105.043208] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Lamins are intermediate filaments that line the inner surface of the nuclear envelope, providing structural support and making contacts with chromatin. There are two types of lamins, A- and B-types, which differ in structure and expression. Drosophila possesses both lamin types, encoded by the LamC (A-type) and lamin Dm0 (B-type) genes. LamC is nested within an intron of the essential gene ttv. We demonstrate that null mutations in LamC are lethal, and expression of a wild-type LamC transgene rescues lethality of LamC but not ttv mutants. Mutations in the human A-type lamin gene lead to diseases called laminopathies. To determine if Drosophila might serve as a useful model to study lamin biology and disease mechanisms, we generated transgenic flies expressing mutant LamC proteins modeled after human disease-causing lamins. These transgenic animals display a nuclear lamin aggregation phenotype remarkably similar to that observed when human mutant A-type lamins are expressed in mammalian cells. LamC aggregates also cause disorganization of lamin Dm0, indicating interdependence of both lamin types for proper lamina assembly. Taken together, these data provide the first detailed genetic analysis of the LamC gene and support using Drosophila as a model to study the role of lamins in disease.
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Affiliation(s)
- Sandra R Schulze
- Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242, USA
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24
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Zhang L, Zhang K, Prändl R, Schöffl F. Detecting DNA-binding of proteins in vivo by UV-crosslinking and immunoprecipitation. Biochem Biophys Res Commun 2004; 322:705-11. [PMID: 15336521 DOI: 10.1016/j.bbrc.2004.07.202] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2004] [Indexed: 10/26/2022]
Abstract
The temporal and spatial binding of proteins on DNA is important to the regulation of genome expression and maintenance. However, examining how the protein-DNA complexes assemble in living cells is challenging. The development of UV-crosslinking/immunoprecipitation (UV-X-ChIP) technique and the progress of its applications show the powerful potential of this method in detecting such binding behavior in vivo. UV light is a zero length crosslinker and is believed to produce less perturbation of the complex than chemical crosslinker. The use of UV laser as UV light source allows the number of photons required for crosslinking to be delivered in nano- or pico- or femtosecond intervals, extremely shortening the irradiation time and achieving higher crosslinking efficiency than conventional UV lamp, thus being well suitable for kinetic studies. UV-X-ChIP technique has been successfully applied on the study of DNA replication, transcription, chromatin structure, and genome-wide location of DNA-binding proteins.
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Affiliation(s)
- Lemin Zhang
- Laboratory for Conservation and Utilization of Bio-resource, Yunnan University, Kunming, Yunnan 650091, PR China.
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25
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Politi V, Perini G, Trazzi S, Pliss A, Raska I, Earnshaw WC, Della Valle G. CENP-C binds the alpha-satellite DNA in vivo at specific centromere domains. J Cell Sci 2002; 115:2317-27. [PMID: 12006616 DOI: 10.1242/jcs.115.11.2317] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CENP-C is a fundamental component of the centromere, highly conserved among species and necessary for the proper assembly of the kinetochore structure and for the metaphase-anaphase transition. Although CENP-C can bind DNA in vitro,the identification of the DNA sequences associated with it in vivo and the significance of such an interaction have been, until now, elusive. To address this problem we took advantage of a chromatin-immunoprecipitation procedure and applied this technique to human HeLa cells. Through this approach we could establish that: (1) CENP-C binds the alpha-satellite DNA selectively; (2) the CENP-C region between amino acids 410 and 537, previously supposed to contain a DNA-binding domain, is indeed required to perform such a function in vivo;and (3) the profile of the alpha-satellite DNA associated with CENP-C is essentially identical to that recognized by CENP-B. However, further biochemical and ultrastructural characterization of CENP-B/DNA and CENP-C/DNA complexes, relative to their DNA components and specific spatial distribution in interphase nuclei, surprisingly reveals that CENP-C and CENP-B associate with the same types of alpha-satellite arrays but in distinct non-overlapping centromere domains. Our results, besides extending previous observations on the role of CENP-C in the formation of active centromeres, show, for the first time, that CENP-C can associate with the centromeric DNA sequences in vivo and, together with CENP-B, defines a highly structured organization of the alpha-satellite DNA within the human centromere.
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Affiliation(s)
- Valeria Politi
- Department of Biology, University of Bologna, via Selmi 3, 40126 Bologna, Italy
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26
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Tolstonog GV, Wang X, Shoeman R, Traub P. Intermediate filaments reconstituted from vimentin, desmin, and glial fibrillary acidic protein selectively bind repetitive and mobile DNA sequences from a mixture of mouse genomic DNA fragments. DNA Cell Biol 2000; 19:647-77. [PMID: 11098216 DOI: 10.1089/10445490050199054] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Employing the whole-genome PCR technique, intermediate filaments (IFs) reconstituted from vimentin, desmin, and glial fibrillary acidic protein were shown to select repetitive and mobile DNA sequence elements from a mixture of mouse genomic DNA fragments. The bound fragments included major and minor satellite DNA, telomere DNA, minisatellites, microsatellites, short and long interspersed nucleotide elements (SINEs and LINEs), A-type particle elements, members of the mammalian retrotransposon-like (MaLR) family, and a series of repeats not assignable to major repetitive DNA families. The latter sequences were either similar to flanking regions of genes; possessed recombinogenic elements such as polypurine/polypyrimidine stretches, GT-rich arrays, or GGNNGG signals; or were characterized by the distribution of oligopurine and pyrimidine motifs whose sequential and vertical alignment resulted in patterns indicative of high recombination potentials of the respective sequences. The different IF species exhibited distinct quantitative differences in DNA selectivities. Complexes consisting of vimentin IFs and DNA fragments containing LINE, (GT)(n) microsatellite, and major satellite DNA sequences were saturable and dynamic and were formed with high efficiency only when the DNAs were partially denatured. The major-groove binder methyl green exerted a stronger inhibitory effect on the binding reaction than did the minor-groove binder distamycin A; the effects of the two compounds were additive. In addition, DNA footprinting studies revealed significant configurational changes in the DNA fragments on interaction with vimentin IFs. In the case of major satellite DNA, vimentin IFs provided protection of the T-rich strand from cleavage by DNase I, whereas the A-rich strand was totally degraded. Taken together, these observations suggest that IF protein(s) bind to double-stranded DNAs at existing single-stranded sites and, taking advantage of their helix-destabilizing potential, further unwind them via a cooperative effort of their N-terminal DNA-binding regions. A comparison of the present results with literature data, as well as a search in the NCBI database, showed that IF proteins are related to nuclear matrix attachment region (MAR)-binding proteins, and the DNA sequences they interact with are very similar or even identical to those involved in a plethora of DNA recombination and related repair events. On the basis of these comparisons, IF proteins are proposed to contribute in a global fashion, not only to genetic diversity, but also to genomic integrity, in addition to their role in gene expression.
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Affiliation(s)
- G V Tolstonog
- Max-Planck-Institut für Zellbiologie, 68526 Ladenburg, Germany
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27
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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: 162] [Impact Index Per Article: 6.8] [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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28
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Dynamics of chromatin position in the interphase nucleus volume. Russ J Dev Biol 2000. [DOI: 10.1007/bf02758828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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29
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Rzepecki R, Fisher PA. During both interphase and mitosis, DNA topoisomerase II interacts with DNA as well as RNA through the protein's C-terminal domain. J Cell Sci 2000; 113 ( Pt 9):1635-47. [PMID: 10751154 DOI: 10.1242/jcs.113.9.1635] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
DNA topoisomerase II (topo II) is thought to be a nuclear enzyme; during interphase most was insoluble and could be recovered in the pellet after centrifugation of cell homogenates at 10,000 g (P-10). Upon entry into mitosis, the majority of topo II did not associate with condensed chromosomes but was apparently solubilized and redistributed throughout the cell. Although two non-chromosomal subfractions of mitotic topo II were defined by centrifugation at 130,000 g, the vast majority (>90%) was recovered in the pellet (P-130). In vivo nucleic acid interactions with topo II were monitored by a recently developed approach of UV-photo-crosslinking, immunoprecipitation and (32)P-labeling. P-10 (interphase) topo II was largely associated with DNA. P-130 (mitotic non-chromosomal) topo II was primarily associated with RNA. These nucleic acid interactions with both interphase and mitotic topo II occurred through the catalytically inert and as yet, poorly understood C-terminal domain of the protein. P-10 topo II was highly active enzymatically. Activity, measured by the ability of topo II to decatenate kDNA minicircles, was reduced by treatment with phosphatase. In contrast, P-130 topo II was relatively inactive but activity could be increased by phosphatase treatment. In vivo, P-130 topo II was more heavily phosphorylated than P-10 topo II; in both, only the C-terminal domain of topo II was detectably modified. Our observations suggest that cell cycle-dependent changes in the distribution, nucleic acid interactions and enzymatic activity of topo II are regulated, at least in part, by phosphorylation/dephosphorylation.
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Affiliation(s)
- R Rzepecki
- The Department of Pharmacological Sciences, University Medical Center, The State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA
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30
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Goldberg M, Lu H, Stuurman N, Ashery-Padan R, Weiss AM, Yu J, Bhattacharyya D, Fisher PA, Gruenbaum Y, Wolfner MF. Interactions among Drosophila nuclear envelope proteins lamin, otefin, and YA. Mol Cell Biol 1998; 18:4315-23. [PMID: 9632815 PMCID: PMC109015 DOI: 10.1128/mcb.18.7.4315] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The nuclear envelope plays many roles, including organizing nuclear structure and regulating nuclear events. Molecular associations of nuclear envelope proteins may contribute to the implementation of these functions. Lamin, otefin, and YA are the three Drosophila nuclear envelope proteins known in early embryos. We used the yeast two-hybrid system to explore the interactions between pairs of these proteins. The ubiquitous major lamina protein, lamin Dm, interacts with both otefin, a peripheral protein of the inner nuclear membrane, and YA, an essential, developmentally regulated protein of the nuclear lamina. In agreement with this interaction, lamin and otefin can be coimmunoprecipitated from the vesicle fraction of Drosophila embryos and colocalize in nuclear envelopes of Drosophila larval salivary gland nuclei. The two-hybrid system was further used to map the domains of interaction among lamin, otefin, and YA. Lamin's rod domain interacts with the complete otefin protein, with otefin's hydrophilic NH2-terminal domain, and with two different fragments derived from this domain. Analogous probing of the interaction between lamin and YA showed that the lamin rod and tail plus part of its head domain are needed for interaction with full-length YA in the two-hybrid system. YA's COOH-terminal region is necessary and sufficient for interaction with lamin. Our results suggest that interactions with lamin might mediate or stabilize the localization of otefin and YA in the nuclear lamina. They also suggest that the need for both otefin and lamin in mediating association of vesicles with chromatin might reflect the function of a protein complex that includes these two proteins.
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Affiliation(s)
- M Goldberg
- Department of Genetics, The Life Sciences Institute, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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31
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Fisher PA. Preparation of karyoskeletal protein-enriched fractions from Drosophila melanogaster cells and tissues. Methods Cell Biol 1997; 53:23-32. [PMID: 9348502 DOI: 10.1016/s0091-679x(08)60872-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- P A Fisher
- Department of Pharmacological Sciences, University Medical Center, State University of New York at Stony Brook 11794, USA
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