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Arifulin EA, Sorokin DV, Tvorogova AV, Kurnaeva MA, Musinova YR, Zhironkina OA, Golyshev SA, Abramchuk SS, Vassetzky YS, Sheval EV. Heterochromatin restricts the mobility of nuclear bodies. Chromosoma 2018; 127:529-537. [PMID: 30291421 DOI: 10.1007/s00412-018-0683-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 09/25/2018] [Accepted: 09/26/2018] [Indexed: 12/24/2022]
Abstract
Nuclear bodies are relatively immobile organelles. Here, we investigated the mechanisms underlying their movement using experimentally induced interphase prenucleolar bodies (iPNBs). Most iPNBs demonstrated constrained diffusion, exhibiting infrequent fusions with other iPNBs and nucleoli. Fusion events were actin-independent and appeared to be the consequence of stochastic collisions between iPNBs. Most iPNBs were surrounded by condensed chromatin, while fusing iPNBs were usually found in a single heterochromatin-delimited compartment ("cage"). The experimentally induced over-condensation of chromatin significantly decreased the frequency of iPNB fusion. Thus, the data obtained indicate that the mobility of nuclear bodies is restricted by heterochromatin.
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Affiliation(s)
- Eugene A Arifulin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Dmitry V Sorokin
- Laboratory of Mathematical Methods of Image Processing, Faculty of Computational Mathematics and Cybernetics, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Anna V Tvorogova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Margarita A Kurnaeva
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Yana R Musinova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
- Koltzov Institute of Developmental Biology of Russian Academy of Sciences, Vavilov str. 26, 119334, Moscow, Russia
| | - Oxana A Zhironkina
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Sergey A Golyshev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Sergey S Abramchuk
- Faculty of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Yegor S Vassetzky
- Koltzov Institute of Developmental Biology of Russian Academy of Sciences, Vavilov str. 26, 119334, Moscow, Russia.
- LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, 94805, Villejuif, France.
- UMR8126, CNRS, Institut de Cancérologie Gustave Roussy, Université Paris-Sud, 94805, Villejuif, France.
| | - Eugene V Sheval
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia.
- LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, 94805, Villejuif, France.
- Department of Cell Biology and Histology, Faculty of Biology, Lomonosov Moscow State University, 119991, Moscow, Russia.
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2
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Xu P, Roizman B. The SP100 component of ND10 enhances accumulation of PML and suppresses replication and the assembly of HSV replication compartments. Proc Natl Acad Sci U S A 2017; 114:E3823-E3829. [PMID: 28439026 PMCID: PMC5441741 DOI: 10.1073/pnas.1703395114] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nuclear domain 10 (ND10) bodies are small (0.1-1 μM) nuclear structures containing both constant [e.g., promyelocytic leukemia protein (PML), SP100, death domain-associated protein (Daxx)] and variable proteins, depending on the function of the cells or the stress to which they are exposed. In herpes simplex virus (HSV)-infected cells, ND10 bodies assemble at the sites of DNA entering the nucleus after infection. In sequence, the ND10 bodies become viral replication compartments, and ICP0, a viral E3 ligase, degrades both PML and SP100. The amounts of PML and SP100 and the number of ND10 structures increase in cells exposed to IFN-β. Earlier studies have shown that PML has three key functions. Thus, (i) the interaction of PML with viral components facilitates the initiation of replication compartments, (ii) viral replication is significantly less affected by IFN-β in PML-/- cells than in parental PML+/+ cells, and (iii) viral yields are significantly lower in PML-/- cells exposed to low ratios of virus per cell compared with parental PML+/+ cells. This report focuses on the function of SP100. In contrast to PML-/- cells, SP100-/- cells retain the sensitivity of parental SP100+/+ cells to IFN-β and support replication of the ΔICP0 virus. At low multiplicities of infection, wild-type virus yields are higher in SP100-/- cells than in parental HEp-2 cells. In addition, the number of viral replication compartments is significantly higher in SP100-/- cells than in parental SP100+/+ cells or in PML-/- cells.
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Affiliation(s)
- Pei Xu
- Marjorie B. Kovler Viral Oncology Laboratories, The University of Chicago, Chicago, IL 60637
| | - Bernard Roizman
- Marjorie B. Kovler Viral Oncology Laboratories, The University of Chicago, Chicago, IL 60637
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3
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Banko MI, Krzyzanowski MK, Turcza P, Maniecka Z, Kulis M, Kozlowski P. Identification of amino acid residues of ERH required for its recruitment to nuclear speckles and replication foci in HeLa cells. PLoS One 2013; 8:e74885. [PMID: 24015320 PMCID: PMC3755989 DOI: 10.1371/journal.pone.0074885] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 08/07/2013] [Indexed: 11/18/2022] Open
Abstract
ERH is a small, highly evolutionarily conserved nuclear protein of unknown function. Its three-dimensional structure is absolutely unique and it can form a homodimer through a β sheet surface. ERH has been shown to interact, among others, with PDIP46/SKAR and Ciz1. When coexpressed with the latter protein, ERH accumulates in replication foci in the nucleus of HeLa cells. Here, we report that when ERH is coexpressed with PDIP46/SKAR in HeLa cells, it is recruited to nuclear speckles, and identify amino acid residues critical for targeting ERH to both these subnuclear structures. ERH H3A Q9A shows a diminished recruitment to nuclear speckles but it is recruited to replication foci. ERH E37A T51A is very poorly recruited to replication foci while still accumulating in nuclear speckles. Consequently, ERH H3A Q9A E37A T51A is recruited neither to nuclear speckles nor to replication foci. The lack of interactions of these three ERH forms with PDIP46/SKAR and/or Ciz1 was further confirmed in vitro by GST pull-down assay. The residues whose substitutions interfere with the accumulation in nuclear speckles are situated on the β sheet surface of ERH, indicating that only the monomer of ERH can interact with PDIP46/SKAR. Substitutions affecting the recruitment to replication foci map to the other side of ERH, near a long loop between the α1 and α2 helices, thus both the monomer and the dimer of ERH could interact with Ciz1. The construction of the ERH mutants not recruited to nuclear speckles or replication foci will facilitate further studies on ERH actions in these subnuclear structures.
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Affiliation(s)
- Monika I. Banko
- Department of Molecular Biology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Marek K. Krzyzanowski
- Department of Molecular Biology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Paulina Turcza
- Department of Molecular Biology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Zuzanna Maniecka
- Department of Molecular Biology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Marta Kulis
- Department of Molecular Biology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Piotr Kozlowski
- Department of Molecular Biology, Faculty of Biology, University of Warsaw, Warsaw, Poland
- * E-mail:
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4
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Rajendra T, Praveen K, Matera AG. Genetic analysis of nuclear bodies: from nondeterministic chaos to deterministic order. Cold Spring Harb Symp Quant Biol 2011; 75:365-74. [PMID: 21467138 PMCID: PMC4062921 DOI: 10.1101/sqb.2010.75.043] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The eukaryotic nucleus is a congested place, and macromolecular crowding is thought to have an important role in increasing the relative concentrations of nuclear proteins, thereby accelerating the rates of biochemical reactions. Crowding is also thought to provide the environment needed for formation of nuclear bodies/subcompartments, such as the Cajal body (CB) and the histone locus body (HLB), via self-organization. In this chapter, we contrast the theories of stochastic self-organization and hierarchical self-organization in their application to nuclear body assembly, using CBs and HLBs as paradigms. Genetic ablation studies in Drosophila on components of CBs and HLBs have revealed an order to the assembly of these structures that is suggestive of a hierarchical model of self-organization. These studies also show that functions attributed to the nuclear bodies are largely unaffected in their absence, reinforcing an emerging theme in the field that the purpose of these subdomains may be to enhance the efficiency and specificity of reactions.
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Affiliation(s)
- T.K. Rajendra
- Departments of Biology and Genetics, Program in Molecular Biology & Biotechnology, Lineberger Comprehensive Cancer Center University of North Carolina, Chapel Hill, NC 27599
| | - Kavita Praveen
- Departments of Biology and Genetics, Program in Molecular Biology & Biotechnology, Lineberger Comprehensive Cancer Center University of North Carolina, Chapel Hill, NC 27599
| | - A. Gregory Matera
- Departments of Biology and Genetics, Program in Molecular Biology & Biotechnology, Lineberger Comprehensive Cancer Center University of North Carolina, Chapel Hill, NC 27599
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5
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Contreras-Dominguez M, Moraes CB, Dorval T, Genovesio A, Dossin FDM, Freitas-Junior LH. A modified fluorescence in situ hybridization protocol for Plasmodium falciparum greatly improves nuclear architecture conservation. Mol Biochem Parasitol 2010; 173:48-52. [PMID: 20433875 DOI: 10.1016/j.molbiopara.2010.04.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2009] [Revised: 04/14/2010] [Accepted: 04/19/2010] [Indexed: 12/17/2022]
Abstract
Fluorescence in situ hybridization (FISH) has been used extensively in the study of nuclear organization and gene positioning in Plasmodium falciparum. While performing FISH with published protocols, we observed large variations in parasite nuclear morphology. We hypothesized that these inconsistencies might be due to the type of parasite preparation prior to FISH, which commonly involves air-drying, prompting us to develop a new fixation protocol. Here we show both qualitatively and quantitatively that compared to air-dried and briefly fixed parasites, longer fixation in suspension leads to improved conservation of nuclear structure and lower intra-population variation of nuclear shape as well as area after FISH development. While the fixation protocol per se does not cause detectable disruptions in nuclear morphology, it greatly influences the conservation of nuclear shape and size during the most stringent steps of FISH. The type of fixation used also influences the detection of telomeric clusters, and we show that the new fixation protocol permits improved conservation of the chromosome end cluster perinuclear distribution and higher colocalization indexes for two adjacent chromosome end probes, Rep20 and telomere. Overall, the results indicate that our alternative protocol dramatically improves conservation of the nuclear architecture compared to previously reported Plasmodium DNA-FISH protocols and highlights the necessity of carefully choosing the fixation protocol for FISH.
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Affiliation(s)
- Monica Contreras-Dominguez
- Center for Neglected Diseases Drug Discovery, Institut Pasteur Korea, Bundang-gu, Seongnam-si, Gyeonggi-do, South Korea
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6
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Schmitt E, Stein S, Hausmann M. Conception of an image data base for cell nuclei and geometric algorithms for diagnosis and therapy monitoring. Stud Health Technol Inform 2009; 147:251-256. [PMID: 19593063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Parameters of the genome architecture of cell nuclei like copy number changes of genes or numerical and structural aberrations of chromosomes displayed by changes of size, shape, form and geometric arrangement of the related territories and domains play an important role in tumour diagnosis and monitoring of tumour therapy. We have defined data structures for such parameters, accompanied by meta data describing cell biology and microscopy protocols, and developed algorithms to deduce geometric data from microscopic raw images of fluorescently labelled cell nuclei. The statistical evaluation of nucleus geometry and architecture data is a valuable aid for diagnostic decisions and monitoring of cancer development, as indicated by several research case studies. The algorithms and data storage devices are presently administrated by different operating systems. Unification of workflow is being achieved for a local cluster, but gridification is still subject to problems of licensing, monitoring, and administering systems, including data security.
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Affiliation(s)
- Eberhard Schmitt
- Kirchhoff Institute of Physics, University of Heidelberg, Germany
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7
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Salsman J, Zimmerman N, Chen T, Domagala M, Frappier L. Genome-wide screen of three herpesviruses for protein subcellular localization and alteration of PML nuclear bodies. PLoS Pathog 2008; 4:e1000100. [PMID: 18617993 PMCID: PMC2438612 DOI: 10.1371/journal.ppat.1000100] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Accepted: 06/11/2008] [Indexed: 01/22/2023] Open
Abstract
Herpesviruses are large, ubiquitous DNA viruses with complex host interactions, yet many of the proteins encoded by these viruses have not been functionally characterized. As a first step in functional characterization, we determined the subcellular localization of 234 epitope-tagged proteins from herpes simplex virus, cytomegalovirus, and Epstein–Barr virus. Twenty-four of the 93 proteins with nuclear localization formed subnuclear structures. Twelve of these localized to the nucleolus, and five at least partially localized with promyelocytic leukemia (PML) bodies, which are known to suppress viral lytic infection. In addition, two proteins disrupted Cajal bodies, and 19 of the nuclear proteins significantly decreased the number of PML bodies per cell, including six that were shown to be SUMO-modified. These results have provided the first functional insights into over 120 previously unstudied proteins and suggest that herpesviruses employ multiple strategies for manipulating nuclear bodies that control key cellular processes. Herpes simplex virus, Epstein–Barr virus, and cytomegalovirus are three types of human herpesviruses that infect most people for their entire life and, under some circumstances, cause significant diseases. Each virus encodes a large number of proteins that function to manipulate the host cell to the best advantage of the virus; however, many of these encoded proteins have never been studied. We have generated constructs to express most of the proteins encoded by these three viruses in human cells and have determined the precise localization of each in the cell. We have also examined how each viral protein affects host nuclear structures called PML bodies, which are part of the cellular response to suppress viral replication. We identified several proteins from all three viruses that disrupt PML bodies, suggesting that they would enable viral infection. Our study has given the first information on the potential function of 120 previously unstudied viral proteins and shows that each virus has multiple mechanisms to disrupt PML bodies that were not previously recognized.
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Affiliation(s)
- Jayme Salsman
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Nicole Zimmerman
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Tricia Chen
- Affinium Pharmaceuticals Inc., Toronto, Ontario, Canada
| | | | - Lori Frappier
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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8
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Kolas NK, Chapman JR, Nakada S, Ylanko J, Chahwan R, Sweeney FD, Panier S, Mendez M, Wildenhain J, Thomson TM, Pelletier L, Jackson SP, Durocher D. Orchestration of the DNA-damage response by the RNF8 ubiquitin ligase. Science 2007; 318:1637-40. [PMID: 18006705 PMCID: PMC2430610 DOI: 10.1126/science.1150034] [Citation(s) in RCA: 687] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Cells respond to DNA double-strand breaks by recruiting factors such as the DNA-damage mediator protein MDC1, the p53-binding protein 1 (53BP1), and the breast cancer susceptibility protein BRCA1 to sites of damaged DNA. Here, we reveal that the ubiquitin ligase RNF8 mediates ubiquitin conjugation and 53BP1 and BRCA1 focal accumulation at sites of DNA lesions. Moreover, we establish that MDC1 recruits RNF8 through phosphodependent interactions between the RNF8 forkhead-associated domain and motifs in MDC1 that are phosphorylated by the DNA-damage activated protein kinase ataxia telangiectasia mutated (ATM). We also show that depletion of the E2 enzyme UBC13 impairs 53BP1 recruitment to sites of damage, which suggests that it cooperates with RNF8. Finally, we reveal that RNF8 promotes the G2/M DNA damage checkpoint and resistance to ionizing radiation. These results demonstrate how the DNA-damage response is orchestrated by ATM-dependent phosphorylation of MDC1 and RNF8-mediated ubiquitination.
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Affiliation(s)
- Nadine K. Kolas
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, M5G 1X5, Ontario, Canada
| | - J. Ross Chapman
- The Wellcome Trust and Cancer Research UK Gurdon Institute, and the Department of Zoology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Shinichiro Nakada
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, M5G 1X5, Ontario, Canada
| | - Jarkko Ylanko
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, M5G 1X5, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Richard Chahwan
- The Wellcome Trust and Cancer Research UK Gurdon Institute, and the Department of Zoology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Frédéric D. Sweeney
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, M5G 1X5, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Stephanie Panier
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, M5G 1X5, Ontario, Canada
| | - Megan Mendez
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, M5G 1X5, Ontario, Canada
| | - Jan Wildenhain
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, M5G 1X5, Ontario, Canada
| | - Timothy M. Thomson
- Department of Molecular and Cellular Biology, Instituto de Biología Molecular de Barcelona c. Jordi Girona 18-2608034 Barcelona, Spain
| | - Laurence Pelletier
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, M5G 1X5, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Stephen P. Jackson
- The Wellcome Trust and Cancer Research UK Gurdon Institute, and the Department of Zoology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Daniel Durocher
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, M5G 1X5, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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9
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Fasching CL, Neumann AA, Muntoni A, Yeager TR, Reddel RR. DNA damage induces alternative lengthening of telomeres (ALT) associated promyelocytic leukemia bodies that preferentially associate with linear telomeric DNA. Cancer Res 2007; 67:7072-7. [PMID: 17652140 DOI: 10.1158/0008-5472.can-07-1556] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The linear chromosomes of vertebrates terminate in telomeres that consist of a tandemly repeated hexameric sequence, 5'TTAGGG3'. Telomeres form a protective loop structure (t-loop), which is thought to prevent them from being recognized as a double-strand break. Approximately 10% of human tumors prevent shortening of their telomeres by using a recombination-mediated alternative lengthening of telomeres (ALT) mechanism. ALT-positive human cells contain extrachromosomal telomere repeat (ECTR) DNA that may either be circular or linear. It has been proposed that ECTR may be generated by recombination events involving the t-loop. A proportion of the cells within ALT-positive cell populations contain promyelocytic leukemia (PML) nuclear bodies that contain telomeric DNA and telomere-binding proteins that are called ALT-associated PML bodies (APB). Although the presence of APBs is very useful for determining whether tumors and cell lines use the ALT mechanism, the function of APBs is unknown. It has previously been shown that telomeric DNA is particularly susceptible to damage by hydrogen peroxide and N-methyl-N'-nitro-N-nitrosoguanidine. We report here that these DNA-damaging agents induce both linear and circular ECTR DNA in ALT cells and increase the proportion of cells that contain APBs. We partially purified APBs and showed that the telomeric repeat DNA they contain is predominantly linear. We propose that a function of APBs is to sequester linear telomeric DNA.
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Affiliation(s)
- Clare L Fasching
- Children's Medical Research Institute, Westmead, and University of Sydney, New South Wales, Sydney, Australia
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10
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Abstract
The eukaryotic nucleus has been the neglected child of cell biology. The "International Symposium on Functional Organization of the Nucleus" held in January on Awaji Island, Japan, highlighted recent work on nuclear organization and function. Emerging from this conference was a holistic view in which diverse chemical and physical signals link the nuclear and cytoplasmic compartments of cells.
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Affiliation(s)
- Abby F Dernburg
- Lawrence Berkeley National Laboratory and University of California, Berkeley, Berkeley, CA 94720, USA.
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11
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Tyrsina EG, Alipov ED, Ivanenko TV. [Structural rearrangements of the chromatin during the adaptive response in two genetically close djungarian hamster fibroblast cell lines with different radiosensitivity]. Radiats Biol Radioecol 2006; 46:697-705. [PMID: 17323698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The capacity of cell for the adaptive response (AR) induction after gamma-irradiation using micronuclear test was investigated. Our model consists of the parental djungarian hamster embryonic fibroblast cell line DH-TK- and its radioresistant progeny (PIC-20). We demonstrated that AR for the more radiosensitive parental cell line was shifted to the lower adaptive and to the challenge doses. The maximal AR for DH-TK- cells was induced at 0.3 Gy adaptive dose and 1.5 Gy challenge dose (adaptive response coefficient (ARC) was 0.4+/- 0.1), whereas for PIC-20 cells these means were 0.5 Gy and 3.0 Gy correspondingly (ARC = 0.45+/-0.1). Using the method of anomalous viscosity time dependence (AVTD) we demonstrated the chromatin rearrangements in both cell lines during 3-5 h after adaptive dose application. The rearrangement degree evaluated by the relative maximal reduced viscosity was considerably higher in PIC-20 cell line than that in DH-TK cells (2.4+/-0.3 vs 1.4+/-0. 1). Interestingly, the time of chromatin rearrangement did not depend neither on the dose nor on the cell type and was similar in both cell lines after 5 h of adaptive dose application. It was also shown that during the AR chromatin relaxation was lower after exposure to both the adaptive and challenge doses than after challenge dose only. In contrast, in the degree of AR chromatin relaxation was higher for both cell lines.
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12
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Beauregard A, Chalamcharla VR, Piazza CL, Belfort M, Coros CJ. Bipolar localization of the group II intron Ll.LtrB is maintained in Escherichia coli deficient in nucleoid condensation, chromosome partitioning and DNA replication. Mol Microbiol 2006; 62:709-22. [PMID: 17005014 DOI: 10.1111/j.1365-2958.2006.05419.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Group II introns are mobile genetic elements that invade their cognate intron-minus alleles via an RNA intermediate, in a process known as retrohoming. They can also retrotranspose to ectopic sites at low frequency. In Escherichia coli, retrotransposition of the lactococcal group II intron, Ll.LtrB, occurs preferentially within the Ori and Ter macrodomains of the E. coli chromosome. These macrodomains migrate towards the poles of the cell, where the intron-encoded protein, LtrA, localizes. Here we investigate whether alteration of nucleoid condensation, chromosome partitioning and replication affect retrotransposition frequencies, as well as bipolar localization of the Ll.LtrB intron integration and LtrA distribution in E. coli. We thus examined these properties in the absence of the nucleoid-associated proteins H-NS, StpA and MukB, in variants of partitioning functions including the centromere-like sequence migS and the actin homologue MreB, as well as in the replication mutants DeltaoriC, seqA, tus and topoIV (ts). Although there were some dramatic fluctuations in retrotransposition levels in these hosts, bipolar localization of integration events was maintained. LtrA was consistently found in nucleoid-free regions, with its localization to the cellular poles being largely preserved in these hosts. Together, these results suggest that bipolar localization of group II intron retrotransposition results from the residence of the intron-encoded protein at the poles of the cell.
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Affiliation(s)
- Arthur Beauregard
- Molecular Genetics Program, Wadsworth Center, New York State Department of Health, Center for Medical Sciences, 150 New Scotland Avenue, Albany, NY 12208, USA
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13
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Sciurano R, Rahn M, Rey-Valzacchi G, Solari AJ. The asynaptic chromatin in spermatocytes of translocation carriers contains the histone variant γ-H2AX and associates with the XY body. Hum Reprod 2006; 22:142-50. [PMID: 16920723 DOI: 10.1093/humrep/del330] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The close apposition of multivalents with the XY body has been repeatedly described in heterozygous carriers of chromosomal rearrangements. Because in many of these carriers spermatogenesis is deeply disturbed at the spermatocyte level, the association of autosomal chromatin with the XY body may impair the spermatocyte life. METHODS Testicular biopsies from three men carriers of three different chromosomal rearrangements have been analysed by electron microscopy (EM) and immunolocalization of meiotic proteins. RESULTS There is an ordered transition from isolated multivalents at early pachytene to XY body association in late pachytene, as shown in a carrier of a rob t(13;14) translocation by EM and in a reciprocal translocation t(9;14) carrier by immunofluorescence. The non-synapsed ends of the quadrivalent show BRCA1 located on the axes and the variant histone gamma-H2AX located on the chromatin. The area covered by gamma-H2AX increases with the association of the asynaptic ends with the XY body in the t(9;14) carrier, and the area covered with gamma-H2AX in the t(Y;15) carrier is larger than that of the XY body of controls. CONCLUSIONS The affinity between the inactive XY body and asynaptic regions of multivalents is given a material basis, and transcriptional inactivation is probably shared by these two chromatin types.
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MESH Headings
- Adult
- Azoospermia/genetics
- Azoospermia/pathology
- BRCA1 Protein/genetics
- Biopsy
- Cell Cycle Proteins
- Cell Nucleus Structures/genetics
- Chromatin/genetics
- Chromatin/ultrastructure
- Chromosomes, Human, Pair 13/genetics
- Chromosomes, Human, Pair 14/genetics
- Chromosomes, Human, Pair 15/genetics
- Chromosomes, Human, Pair 9/genetics
- Chromosomes, Human, X/genetics
- Chromosomes, Human, Y/genetics
- DNA-Binding Proteins
- Histones/genetics
- Humans
- Male
- Nuclear Proteins/genetics
- Oligospermia/genetics
- Oligospermia/pathology
- Spermatocytes/ultrastructure
- Testis/pathology
- Translocation, Genetic/genetics
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Affiliation(s)
- R Sciurano
- Biologia Celular, CIR, Facultad de Medicina, Universidad de Buenos Aires, Argentina
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14
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Bøe SO, Haave M, Jul-Larsen A, Grudic A, Bjerkvig R, Lønning PE. Promyelocytic leukemia nuclear bodies are predetermined processing sites for damaged DNA. J Cell Sci 2006; 119:3284-95. [PMID: 16868026 DOI: 10.1242/jcs.03068] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The promyelocytic leukemia protein (PML) participates in several cellular functions, including transcriptional regulation, apoptosis and maintenance of genomic stability. A key feature of this protein is its ability to induce the assembly of nuclear compartments termed PML-nuclear bodies (PML-NBs). Here we show that these nuclear structures recruit single-stranded DNA (ssDNA) molecules in response to exogenous DNA damage. ssDNA was readily detected in PML-NBs within 1 hour following exposure of cells to UV light. Confocal real-time imaging of cells expressing YFP-tagged PML did not reveal de novo formation of new PML-NBs following UV-irradiation, which shows that ssDNA focus formation occurred within pre-existing PML-NBs. Moreover, siRNA-mediated depletion of PML prevented ssDNA focus formation and sensitized cells to UV-induced apoptosis. PML-dependent ssDNA focus formation was found to be particularly efficient during S-phase of the cell cycle, and PML-depleted cells became retarded in S-phase upon growth in the presence of etoposide. In addition, we found that caffeine and the poly(ADP-ribose) polymerase (PARP) inhibitor NU1027 enhanced UV-induced recruitment of ssDNA to PML-NBs. Together, our results show that PML-NBs have the capacity to accommodate DNA metabolic activities that are associated with processing of damaged DNA.
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Affiliation(s)
- Stig Ove Bøe
- Section of Oncology, Department of Medicine, Haukeland University Hospital, Bergen, Norway.
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15
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Harata M, Kitayama K, Oma Y. [Nuclear structure: its molecular basis and dynamics]. Tanpakushitsu Kakusan Koso 2006; 51:591-9. [PMID: 16719317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
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16
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Kimura H. [Robustness and plasticity of chromatin that is organized functionally in the nucleus]. Tanpakushitsu Kakusan Koso 2006; 51:293-300. [PMID: 16613165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
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17
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Abstract
Studies of how the eukaryotic nucleus is functionally organized have led to the realization that nuclei are incredibly dynamic. Many nuclear structures are actually by products of a large steady-state flux of macromolecules through a given domain. A recent conference in the south of France on Nuclear Structure and Dynamics brought together scientists with diverse perspectives on the nucleus to try to provide a more coherent picture of the nucleus's dynamic organization and how this architecture is entwined with epigenetic control of gene expression.
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Affiliation(s)
- Asifa Akhtar
- European Molecular Biology Laboratory (EMBL), Gene Expression Program, Meyerhof Str. 1, 69117 Heidelberg, Germany.
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18
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Kobori T, Kodama M, Hizume K, Yoshimura SH, Ohtani T, Takeyasu K. Comparative structural biology of the genome: nano-scale imaging of single nucleus from different kingdoms reveals the common physicochemical property of chromatin with a 40 nm structural unit. J Electron Microsc (Tokyo) 2006; 55:31-40. [PMID: 16495343 DOI: 10.1093/jmicro/dfi076] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Genome function is closely linked to the higher-order chromatin structures. To reveal a structural basis for the interphase chromatin organization, the 'on-substrate' lysis procedure was applied to nuclei isolated from human HeLa cells, chicken erythrocyte cells and yeast Schizosaccharomyces pombe, which possessed different intrinsic properties of the genomes such as histone composition and inter-nucleosomal distance. The isolated nuclei on a coverslip were successively treated with a detergent and a high-salt solution to extract the nuclear membrane and the nucleoplasm, and therefore, atomic force microscopy (AFM) visualized the structural changes in response to the lysis procedure. After the nucleoplasm was extracted, AFM clarified that chromatin fibers, approximately 40 nm in width, were partially released out of the nuclei and that the other chromatin still remaining in the nuclei was composed of granular structures with diameter of 80-100 nm. Thus, these results suggest that the approximately 40 nm fiber would be a stable structural unit and fold the 80-100 nm granules into a one-step higher unit. A common mechanism could be implied regardless of the intrinsic properties of the eukaryotic genomes.
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Affiliation(s)
- Toshiro Kobori
- Laboratory of Plasma Membrane and Nuclear Signaling, Graduate School of Biostudies, Kyoto University, Kitashirakawa, Kyoto 606-8502, Japan.
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19
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Straub T, Neumann MF, Prestel M, Kremmer E, Kaether C, Haass C, Becker PB. Stable chromosomal association of MSL2 defines a dosage-compensated nuclear compartment. Chromosoma 2005; 114:352-64. [PMID: 16179989 DOI: 10.1007/s00412-005-0020-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Accepted: 07/15/2005] [Indexed: 11/30/2022]
Abstract
Dosage compensation in Drosophila is controlled by a complex (DCC) of proteins and noncoding RNA that binds specifically to the male X chromosome and leads to fine-tuning of transcription. Here, we employ male SL2 cells to characterize DCC function and dynamics during steady state of dosage compensation. Knocking down the key regulator of dosage compensation, male-specific-lethal 2 (MSL2), leads to loss of propagation of histone H4 lysine 16 acetylation and of the twofold elevation of transcription characteristic of the compensated male X chromosome. Surprisingly, lack of dosage compensation does not impair cell viability. Targeting of MSL2 to a reporter gene suffices to initiate dosage compensation in the cell model. Using photobleaching techniques in living cells, we found the association of MSL2 with the X chromosome to be exceptionally stable, essentially excluding dynamic redistribution of the DCC during interphase. This immobility distinguishes MSL2 from most other chromosomal proteins. Our findings have profound implications for the mechanism underlying dosage compensation and furthermore provide a new, conceptual reference of stability in an otherwise highly dynamic nuclear environment.
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Affiliation(s)
- Tobias Straub
- Department of Molecular Biology, Adolf Butenandt-Institute, Schillerstr. 44, 80336, Munich, Germany
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20
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Morito Y, Terada Y, Nakamura S, Morita J, Yoshimoto T, Murakami T, Yaegashi N, Okamura K. Dynamics of microtubules and positioning of female pronucleus during bovine parthenogenesis. Biol Reprod 2005; 73:935-41. [PMID: 15987826 DOI: 10.1095/biolreprod.105.042366] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The zygote centrosome, consisting of both paternal and maternal centrosomal components, is the microtubule-organizing center necessary for pronuclear migration and positioning in fertilization. Maternal centrosomal function in microtubule organization and pronuclear positioning, however, remains unclear. In the present study, we sought to elucidate the function of maternal centrosomes during bovine parthenotes in the microtubule organizational processes required to move the pronucleus to the cell center without sperm centrosomal components. Microtubule organization, pronuclear position, and distribution of gamma-tubulin, which is thought to be the major component of maternal centrosomal material, were imaged by immunocytochemistry and conventional epifluorescence microscopy. In bovine parthenotes treated with paclitaxel, a microtubule-stabilizing drug, the cytoplasmic microtubule asters became organized after chemical activation, and the microtubules radiated dynamically toward the female pronucleus. The microtubule patterns correlated well with pronuclear movement to the cell center. Microtubules aggregated at regions of gamma-tubulin concentration, but gamma-tubulin did not localize to a spot until the first interphase of bovine parthenogenesis. These findings indicate that gamma-tubulin is responsible for microtubule organization as the maternal centrosome. In bovine parthenogenesis, the maternal centrosome then organizes cytoplasmic microtubules to move the female pronucleus into the cell center. We propose that the maternal centrosome plays a role as a functional centrosome despite the lack of a sperm contribution, making this structure less competent for microtubule organization in comparison with centrosomes containing sperm centrosomal components.
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Affiliation(s)
- Yuki Morito
- Department of Obstetrics and Gynecology, Tohoku University School of Medicine, Sendai, Miyagi 980-8574, Japan
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21
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Hivin P, Frédéric M, Arpin-André C, Basbous J, Gay B, Thébault S, Mesnard JM. Nuclear localization of HTLV-I bZIP factor (HBZ) is mediated by three distinct motifs. J Cell Sci 2005; 118:1355-62. [PMID: 15755797 DOI: 10.1242/jcs.01727] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genome of the human T-cell leukemia virus type I (HTLV-I) codes for a basic leucine zipper protein, HBZ, capable of repressing JUN activity and viral transcription. Transient expression in mammalian cells showed that HBZ was targeted to the nucleus, where it accumulated in nuclear speckles. By using a complementary set of deletion mutants, we report here that the nuclear targeting of HBZ is mediated by three distinct nuclear localization signals and that at least two are necessary for the translocation of HBZ to the nucleus. Moreover, the resulting mutant proteins distribute throughout the nucleoplasm and/or into the nucleoli, whereas the wild-type HBZ exclusively accumulates in nuclear speckles, suggesting that the integrity of the protein is required for its speckle localization. We also demonstrate that the HBZ-containing speckles do not correspond to Cajal bodies, splicing factor compartments, or promyelocytic leukemia oncoprotein bodies. Unexpectedly, by using immunogold electron microscopy, we found HBZ localized to heterochromatin. Until now, such characteristics had never been described for a transcription factor and could explain the inhibitory activity of HBZ.
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Affiliation(s)
- Patrick Hivin
- Laboratoire Infections Rétrovirales et Signalisation Cellulaire, CNRS/UM I UMR 5121/IFR 122, Institut de Biologie, 34960 Montpellier Cedex 2, France
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22
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Metz A, Soret J, Vourc'h C, Tazi J, Jolly C. A key role for stress-induced satellite III transcripts in the relocalization of splicing factors into nuclear stress granules. J Cell Sci 2005; 117:4551-8. [PMID: 15331664 DOI: 10.1242/jcs.01329] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Exposure of cells to stressful conditions results in the rapid synthesis of a subset of specialized proteins termed heat shock proteins (HSPs) which function in protecting the cell against damage. The stress-induced activation of hsp genes is controlled by the heat shock transcription factor 1 (HSF1). At the cellular level, one of the most striking effects of stress is the rapid and reversible redistribution of HSF1 into a few nuclear structures termed nuclear stress granules which form primarily on the 9q12 locus in humans. Within these structures, HSF1 binds to satellite III repeated elements and drives the RNA polymerase II-dependent transcription of these sequences into stable RNAs which remain associated with the 9q12 locus for a certain time after synthesis. Other proteins, in particular splicing factors, were also shown to relocalize to the granules upon stress. Here, we investigated the role of stress-induced satellite III transcripts in the relocalization of splicing factors to the granules. We show that the recruitment of the two serine/arginine-rich (SR) proteins SF2/ASF and SRp30c requires the presence of stress-induced satellite III transcripts. In agreement with these findings, we identified the second RNA-recognition motif (RRM2) of hSF2/ASF as the motif required for the targeting to the granules, and we showed by immunoprecipitation that the endogenous hSF2/ASF protein is present in a complex with satellite III transcripts in stressed cells in vivo. Interestingly, satellite III transcripts also immunoprecipitate together with small nuclear ribonucleoproteins (snRNPs) in vivo whereas the intronless hsp70 transcripts do not, supporting the proposal that these transcripts are subject to splicing. Altogether, these data highlight the central role for satellite III transcripts in the targeting and/or retention of splicing factors into the granules upon stress.
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Affiliation(s)
- Alexandra Metz
- INSERM U309, Institut Albert Bonniot, Domaine de la Merci, 38706 La Tronche CEDEX, France
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23
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Abstract
Nuclear stress granules are subnuclear compartments that form in response to heat shock and other stress stimuli. Although many components of nuclear stress granules have been identified, including HSF1 and pre-mRNA processing factors, their function remains a mystery. A paper in this issue describes the stress-induced transcriptional activation of one of the nuclear stress granule target sites, a heterochromatic region that has been considered silent (Jolly et al., 2004). These intriguing findings will certainly give the research of these structures a new twist.
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Affiliation(s)
- Anton Sandqvist
- Turku Centre for Biotechnology, BioCity, P.O. Box 123, FIN-20521 Turku, Finland
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24
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Jul-Larsen A, Visted T, Karlsen BO, Rinaldo CH, Bjerkvig R, Lønning PE, Bøe SO. PML-nuclear bodies accumulate DNA in response to polyomavirus BK and simian virus 40 replication. Exp Cell Res 2004; 298:58-73. [PMID: 15242762 DOI: 10.1016/j.yexcr.2004.03.045] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2003] [Revised: 03/10/2004] [Indexed: 01/08/2023]
Abstract
Promyelocytic nuclear bodies (PML-NBs) are distinct nuclear structures that are involved in apoptosis, differentiation, transcriptional regulation and DNA damage response. These bodies have also been shown to associate with nuclear sites of viral DNA replication. In the present study, we used BrdU pulse labeling to demonstrate that PML-NBs accumulate newly synthesized DNA in cells infected by the polyomaviruses simian virus 40 (SV40) or polyomavirus BK (BKV). Sequestration of DNA molecules in these structures depended on active viral DNA replication, and was observed exclusively in cells that contained prominent viral replication domains. Furthermore, a significant portion of the accumulated DNA was found to be single-stranded, indicating that the sequestered DNA had been subjected to processing by nuclease or DNA unwinding activities. siRNA-mediated suppression of the PML protein prevented the recruitment of single-stranded DNA into nuclear foci, but did not significantly affect the overall efficiency of viral DNA replication. These results indicate a role of PML and PML-NBs in post-replication DNA processing, and suggest that PML-NBs become linked to sites of viral DNA synthesis due to a role of these structures in DNA metabolism.
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Affiliation(s)
- Asne Jul-Larsen
- Section of Anatomy and Cell Biology, Department of Biomedicine, University of Bergen, 5009, Norway
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25
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Abstract
A systematic analysis of the spatial positioning of a subset of mouse chromosomes reveals that chromosomes exhibit tissue-specific organization in the nucleus. Background Genomes are organized in vivo in the form of chromosomes. Each chromosome occupies a distinct nuclear subvolume in the form of a chromosome territory. The spatial positioning of chromosomes within the interphase nucleus is often nonrandom. It is unclear whether the nonrandom spatial arrangement of chromosomes is conserved among tissues or whether spatial genome organization is tissue-specific. Results Using two-dimensional and three-dimensional fluorescence in situ hybridization we have carried out a systematic analysis of the spatial positioning of a subset of mouse chromosomes in several tissues. We show that chromosomes exhibit tissue-specific organization. Chromosomes are distributed tissue-specifically with respect to their position relative to the center of the nucleus and also relative to each other. Subsets of chromosomes form distinct types of spatial clusters in different tissues and the relative distance between chromosome pairs varies among tissues. Consistent with the notion that nonrandom spatial proximity is functionally relevant in determining the outcome of chromosome translocation events, we find a correlation between tissue-specific spatial proximity and tissue-specific translocation prevalence. Conclusions Our results demonstrate that the spatial organization of genomes is tissue-specific and point to a role for tissue-specific spatial genome organization in the formation of recurrent chromosome arrangements among tissues.
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Affiliation(s)
- Luis A Parada
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Philip G McQueen
- Mathematical and Statistical Laboratory, Division of Computational Biology, Center for Information Technology, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tom Misteli
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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26
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Abstract
The sex chromosomes of mammalian spermatocytes form a specialized nuclear territory known as the XY body, where both transcription and homologous recombination are restricted. The array of proteins assembled into the XY body is typical of heterochromatin. This special subnuclear domain is in distinct contrast to the autosomal domain of the spermatocyte nucleus, where both homologous recombination and transcription occur. The special features of the XY body might reflect absence of homology between the sex chromosomes, rather than any form of dosage compensation, and may also serve to mark parental origin of the paternal X chromosome.
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27
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Abstract
While genomic DNA, packaged into chromatin, is known to be locally constrained but highly dynamic in the nuclei of living cells, little is known about the localization and dynamics of small circular DNA molecules that invade cells by virus infection, application of gene therapy vectors or experimental transfection. To address this point, we have created traceable model substrates by direct labeling of plasmid DNA with fluorescent peptide nucleic acids, and have investigated their fate after microinjection into living cells. Here, we report that foreign DNA rapidly undergoes interactions with intranuclear structural sites that strongly reduce its mobility and restrict the DNA to regions excluding nucleoli and nuclear bodies such as PML bodies. The labeled plasmids partially co-localize with SAF-A, a well characterized marker protein for the nuclear 'scaffold' or 'matrix', and are resistant towards extraction by detergent and, in part, elevated salt concentrations. We show that the localization and the low mobility of plasmids is independent of the plasmid sequence, and does not require the presence of either a scaffold attachment region (SAR) DNA element or a functional promoter.
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Affiliation(s)
- Giulia Mearini
- Department of Molecular Cell Biology, Heinrich-Pette-Institute, Martinistrasse 52, 20251 Hamburg, Germany
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28
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Badin-Larçon AC, Boscheron C, Soleilhac JM, Piel M, Mann C, Denarier E, Fourest-Lieuvin A, Lafanechère L, Bornens M, Job D. Suppression of nuclear oscillations in Saccharomyces cerevisiae expressing Glu tubulin. Proc Natl Acad Sci U S A 2004; 101:5577-82. [PMID: 15031428 PMCID: PMC397425 DOI: 10.1073/pnas.0307917101] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In most eukaryotic cells, the C-terminal amino acid of alpha-tubulin is aromatic (Tyr in mammals and Phe in Saccharomyces cerevisiae) and is preceded by two glutamate residues. In mammals, the C-terminal Tyr of alpha-tubulin is subject to cyclic removal from the peptide chain by a carboxypeptidase and readdition to the chain by a tubulin-Tyr ligase. There is evidence that tubulin-Tyr ligase suppression and the resulting accumulation of detyrosinated (Glu) tubulin favor tumor growth, both in animal models and in human cancers. However, the molecular basis for this apparent stimulatory effect of Glu tubulin accumulation on tumor progression is unknown. Here we have developed S. cerevisiae strains expressing only Glu tubulin and used them as a model to assess the consequences of Glu tubulin accumulation in cells. We find that Glu tubulin strains show defects in nuclear oscillations. These defects are linked to a markedly decreased association of the yeast ortholog of CLIP170, Bik1p, with microtubule plus-ends. These results indicate that the accumulation of Glu tubulin in cells affects microtubule tip complexes that are important for microtubule interactions with the cell cortex.
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Affiliation(s)
- A C Badin-Larçon
- Laboratoire du Cytosquelette, Commissariat à l'Energie Atomique Grenoble, Département de Réponse et Dynamique Cellulaire, Institut National de la Santé et de la Recherche Médicale U366, 38054 Grenoble, France
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29
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Abstract
Exposure of mammalian cells to stress induces the activation of heat shock transcription factor 1 (HSF1) and the subsequent transcription of heat shock genes. Activation of the heat shock response also correlates with a rapid relocalization of HSF1 within a few nuclear structures termed nuclear stress granules. These stress-induced structures, which form primarily on the 9q12 region in humans through direct binding of HSF1 to satellite III repeats, do not colocalize with transcription sites of known hsp genes. In this paper, we show that nuclear stress granules correspond to RNA polymerase II transcription factories where satellite III repeats are transcribed into large and stable RNAs that remain associated with the 9q12 region, even throughout mitosis. This work not only reveals the existence of a new major heat-induced transcript in human cells that may play a role in chromatin structure, but also provides evidence for a transcriptional activity within a locus considered so far as heterochromatic and silent.
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Affiliation(s)
- Caroline Jolly
- INSERM U309, Institut A. Bonniot, 38706 La Tronche cedex, France.
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30
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Weger S, Hammer E, Engstler M. The DNA topoisomerase I binding protein topors as a novel cellular target for SUMO-1 modification: characterization of domains necessary for subcellular localization and sumolation. Exp Cell Res 2003; 290:13-27. [PMID: 14516784 DOI: 10.1016/s0014-4827(03)00292-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Over the past years, modification by covalent attachment of SUMO (small ubiquitin-like modifier) has been demonstrated for of a number of cellular and viral proteins. While increasing evidence suggests a role for SUMO modification in the regulation of protein-protein interactions and/or subcellular localization, most SUMO targets are still at large. In this report we show that Topors, a Topoisomerase I and p53 interacting protein of hitherto unknown function, presents a novel cellular target for SUMO-1 modification. In a yeast two-hybrid system, Topors interacted with both SUMO-1 and the SUMO-1 conjugating enzyme UBC9. Multiple SUMO-1 modified forms of Topors could be detected after cotransfection of exogenous SUMO-1 and Topors induced the colocalization of a YFP tagged SUMO-1 protein in a speckled pattern in the nucleus. A subset of these Topors' nuclear speckles were closely associated with the PML nuclear bodies (POD, ND10). A central domain comprising Topors residues 437 to 574 was sufficient for both sumolation and localization to nuclear speckles. One SUMO-1 acceptor site at lysine residue 560 could be identified within this region. However, sumolation-deficient Topors mutants showed that sumolation obviously is not required for localization to nuclear speckles.
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Affiliation(s)
- Stefan Weger
- Department of Virology, Institute of Infectious Diseases, Free University of Berlin, Hindenburgdamm 27, 12203 Berlin, Germany.
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31
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Young TM, Wang Q, Pe'ery T, Mathews MB. The human I-mfa domain-containing protein, HIC, interacts with cyclin T1 and modulates P-TEFb-dependent transcription. Mol Cell Biol 2003; 23:6373-84. [PMID: 12944466 PMCID: PMC193714 DOI: 10.1128/mcb.23.18.6373-6384.2003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Positive transcription elongation factor b (P-TEFb) hyperphosphorylates the carboxy-terminal domain of RNA polymerase II, permitting productive transcriptional elongation. The cyclin T1 subunit of P-TEFb engages cellular transcription factors as well as the human immunodeficiency virus type 1 (HIV-1) transactivator Tat. To identify potential P-TEFb regulators, we conducted a yeast two-hybrid screen with cyclin T1 as bait. Among the proteins isolated was the human I-mfa domain-containing protein (HIC). HIC has been reported to modulate expression from both cellular and viral promoters via its C-terminal cysteine-rich domain, which is similar to the inhibitor of MyoD family a (I-mfa) protein. We show that HIC binds cyclin T1 in yeast and mammalian cells and that it interacts with intact P-TEFb in mammalian cell extracts. The interaction involves the I-mfa domain of HIC and the regulatory histidine-rich region of cyclin T1. HIC also binds Tat via its I-mfa domain, although the sequence requirements are different. HIC colocalizes with cyclin T1 in nuclear speckle regions and with Tat in the nucleolus. Expression of the HIC cDNA modulates Tat transactivation of the HIV-1 long terminal repeat (LTR) in a cell type-specific fashion. It is mildly inhibitory in CEM cells but stimulates gene expression in HeLa, COS, and NIH 3T3 cells. The isolated I-mfa domain acts as a dominant negative inhibitor. Activation of the HIV-1 LTR by HIC in NIH 3T3 cells occurs at the RNA level and is mediated by direct interactions with P-TEFb.
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Affiliation(s)
- Tara M Young
- Department of Biochemistry and Molecular Biology, New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07013-2714, USA
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32
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Girdwood D, Bumpass D, Vaughan OA, Thain A, Anderson LA, Snowden AW, Garcia-Wilson E, Perkins ND, Hay RT. P300 transcriptional repression is mediated by SUMO modification. Mol Cell 2003; 11:1043-54. [PMID: 12718889 DOI: 10.1016/s1097-2765(03)00141-2] [Citation(s) in RCA: 359] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
p300 and CREB binding protein can both activate and repress transcription. Here, we locate the CRD1 transcriptional repression domain between residues 1017 and 1029 of p300. This region contains two copies of the sequence psiKxE that are modified by the ubiquitin-like protein SUMO-1. Mutations that reduce SUMO modification increase p300-mediated transcriptional activity and expression of a SUMO-specific protease or catalytically inactive Ubc9 relieved repression, demonstrating that p300 repression was mediated by SUMO conjugation. SUMO-modified CRD1 domain bound HDAC6 in vitro, and p300 repression was relieved by histone deacetylase inhibition and siRNA-mediated ablation of HDAC6 expression. These results reveal a mechanism controlling p300 function and suggest that SUMO-dependent repression is mediated by recruitment of HDAC6.
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Affiliation(s)
- David Girdwood
- Institute of Biomolecular Sciences, University of Street Andrews, North Haugh, United Kingdom
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33
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Abstract
Double-stranded RNA (dsRNA) has emerged as a modulator of gene expression, from gene silencing to antiviral responses. Here we show that dsRNA stem-loop structures found in intronic regions of the S. cerevisiae RPS22B and RPL18A transcripts trigger degradation of unspliced pre-mRNAs and lariat introns and can control the level of mRNA produced from these intron-containing genes. The dsRNA regions are cleaved by Rnt1p, the yeast ortholog of RNase III, which creates an entry site for complete degradation by the Xrn1p and Rat1p exonucleases and by the nuclear exosome. These results identify an alternative discard pathway for precursors and products of the splicing machinery and a physiological function for dsRNA in eukaryotic RNA catabolism.
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Affiliation(s)
- Michal Danin-Kreiselman
- Department of Chemistry and Biochemistry and The Molecular Biology Institute, University of California, Los Angeles, Box 951569, Los Angeles, CA 90095, USA
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34
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Thrower DA, Stemple J, Yeh E, Bloom K. Nuclear oscillations and nuclear filament formation accompany single-strand annealing repair of a dicentric chromosome in Saccharomyces cerevisiae. J Cell Sci 2003; 116:561-9. [PMID: 12508116 DOI: 10.1242/jcs.00251] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dicentric chromosomes undergo breakage during mitosis as a result of the attachment of two centromeres on one sister chromatid to opposite spindle poles. Studies utilizing a conditional dicentric chromosome III in Saccharomyces cerevisiae have shown that dicentric chromosome repair occurs primarily by deletion of one centromere via a RAD52-dependent recombination pathway. We report that dicentric chromosome resolution requires RAD1, a gene involved in the single-strand annealing DNA repair pathway. We additionally show that single-strand annealing repair of a dicentric chromosome can occur in the absence of RAD52. RAD52-independent repair requires the adaptation-defective cdc5-ad allele of the yeast polo kinase and the DNA damage checkpoint gene RAD9. Dicentric chromosome breakage in cdc5-ad rad52 mutant cells is associated with a prolonged mitotic arrest, during which nuclei undergo microtubule-dependent oscillations, accompanied by dynamic changes in nuclear morphology. We further demonstrate that the frequency of spontaneous direct repeat recombination is suppressed in yeast cells treated with benomyl, a drug that perturbs microtubules. Our findings indicate that microtubule-dependent processes facilitate recombination.
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Affiliation(s)
- Douglas A Thrower
- Department of Biology, CB3280 University of North Carolina, Chapel Hill, NC 27599-3280, USA
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Nefkens I, Negorev DG, Ishov AM, Michaelson JS, Yeh ETH, Tanguay RM, Müller WEG, Maul GG. Heat shock and Cd2+ exposure regulate PML and Daxx release from ND10 by independent mechanisms that modify the induction of heat-shock proteins 70 and 25 differently. J Cell Sci 2003; 116:513-24. [PMID: 12508112 DOI: 10.1242/jcs.00253] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nuclear domains called ND10 or PML bodies might function as nuclear depots by recruiting or releasing certain proteins. Although recruitment of proteins through interferon-induced upregulation and SUMO-1 modification level of PML had been defined, it is not known whether release of proteins is regulated and has physiological consequences. Exposure to sublethal environmental stress revealed a sequential release of ND10-associated proteins. Upon heat shock Daxx and Sp100 were released but PML remained, whereas exposure to subtoxic concentrations of CdCl(2) induced the release of ND10-associated proteins, including PML, with Sp100 remaining in a few sites. In both cases, recovery times were similar and were followed by a burst of mitotic activity. Cadmium-induced release of proteins from ND10 could be blocked by inhibiting activation of p38 MAPK or ERK1/2. By contrast, heat-shock-induced desumolation of PML and release of proteins from ND10 are unaffected by these inhibitors but can be recapitulated by overexpression of the SUMO isopeptidase SENP-1. Therefore, activation of SENP-1-like SUMO isopeptidase(s) during heat shock is not affected by these kinases. Thus, the release of ND10-associated proteins is not due to a general dispersal of nuclear domains but seems to be regulated by rapid desumolation during thermal stress and through the phosphorylation cascade of stress and mitogenic signaling pathways in the case of CdCl(2). Whether the release of certain proteins had consequences was tested for heat-shock-protein transcription and synthesis. Release of Daxx correlated with Hsp25 suppression, suggesting that Daxx normally inhibits immediate Hsp25 production. Release of PML correlated with lower production of Hsp70. These results suggest that segregation or release of PML or Daxx have differential physiological relevance during the stress response. The fact that enzymatic activation of protein release or segregation after stress modifies the heat-shock response strengthens the concept of ND10 as a regulated depot of effector proteins.
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Affiliation(s)
- Isabelle Nefkens
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
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36
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Engelhardt OG, Boutell C, Orr A, Ullrich E, Haller O, Everett RD. The homeodomain-interacting kinase PKM (HIPK-2) modifies ND10 through both its kinase domain and a SUMO-1 interaction motif and alters the posttranslational modification of PML. Exp Cell Res 2003; 283:36-50. [PMID: 12565818 DOI: 10.1016/s0014-4827(02)00025-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Homeodomain-interacting protein kinases (HIPK-1, -2, and -3) are a family of enzymes that have been implicated in the phosphorylation and repression of homeodomain-containing transcription factors. HIPK-2 has been found to interact with the SUMO-1-conjugating enzyme Ubc9 and can be covalently modified by SUMO-1. It has also been shown to interact with and phosphorylate p53 and to form punctate speckles in the nucleus of which a proportion colocalize with PML nuclear bodies (ND10). We have previously shown that the hamster equivalent of HIPK-2 (named PKM) interacts with the interferon-induced antiviral GTPase Mx1 and associates with ND10 in interferon-treated cells. Given the connections between the interferon response pathway, constituents of ND10, and SUMO-1-conjugated proteins, we have studied the effects of exogenously expressed PKM on endogenous ND10 proteins. We found that PKM induces structural changes in ND10 that can be attributed both to its kinase activity and to the presence of a functional SUMO-1 interaction motif in the C-terminal half of the protein. The changes in the localization of PML, Sp100, and hDaxx induced by exogenous PKM or fragments thereof correlate with changes in the posttranslationally modified species of PML. We propose that PKM is able to modify ND10 structure by inducing changes in the posttranslational modification of PML and by interacting with SUMO-1 modification pathways.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Animals
- Antigens, Nuclear/genetics
- Antigens, Nuclear/metabolism
- Autoantigens/genetics
- Autoantigens/metabolism
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cell Nucleus Structures/enzymology
- Cell Nucleus Structures/genetics
- Cells, Cultured
- Co-Repressor Proteins
- Eukaryotic Cells/cytology
- Eukaryotic Cells/enzymology
- Fluorescent Antibody Technique
- Humans
- Intracellular Signaling Peptides and Proteins
- Leukemia, Promyelocytic, Acute/enzymology
- Leukemia, Promyelocytic, Acute/genetics
- Microscopy, Confocal
- Molecular Chaperones
- Mutation/genetics
- Neoplasm Proteins/genetics
- Neoplasm Proteins/metabolism
- Nuclear Proteins/genetics
- Nuclear Proteins/metabolism
- Plasmids/genetics
- Promyelocytic Leukemia Protein
- Protein Binding/genetics
- Protein Biosynthesis/genetics
- Protein Serine-Threonine Kinases/genetics
- Protein Serine-Threonine Kinases/metabolism
- Protein Structure, Tertiary/genetics
- SUMO-1 Protein/genetics
- SUMO-1 Protein/metabolism
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Tumor Suppressor Proteins
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Affiliation(s)
- Othmar G Engelhardt
- Abteilung Virologie, Institut für Medizinische Mikrobiologie und Hygiene, Universität Freiburg, Hermann-Herder-Strasse 11, D-79104 Freiburg, Germany
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37
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Fenech M, Bonassi S, Turner J, Lando C, Ceppi M, Chang WP, Holland N, Kirsch-Volders M, Zeiger E, Bigatti MP, Bolognesi C, Cao J, De Luca G, Di Giorgio M, Ferguson LR, Fucic A, Lima OG, Hadjidekova VV, Hrelia P, Jaworska A, Joksic G, Krishnaja AP, Lee TK, Martelli A, McKay MJ, Migliore L, Mirkova E, Müller WU, Odagiri Y, Orsiere T, Scarfì MR, Silva MJ, Sofuni T, Surralles J, Trenta G, Vorobtsova I, Vral A, Zijno A, Suralles J. Intra- and inter-laboratory variation in the scoring of micronuclei and nucleoplasmic bridges in binucleated human lymphocytes. Results of an international slide-scoring exercise by the HUMN project. Mutat Res 2003; 534:45-64. [PMID: 12504754 DOI: 10.1016/s1383-5718(02)00248-6] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
One of the objectives of the HUman MicroNucleus (HUMN) project is to identify the methodological variables that have an important impact on micronucleus (MN) or micronucleated (MNed) cell frequencies measured in human lymphocytes using the cytokinesis-block micronucleus assay. In a previous study we had shown that the scoring criteria used were likely to be an important variable. To determine the extent of residual variation when laboratories scored cells from the same cultures using the same set of standard scoring criteria, an inter-laboratory slide-scoring exercise was performed among 34 laboratories from 21 countries with a total of 51 slide scorers involved. The results of this study show that even under these optimized conditions there is a great variation in the MN frequency or MNed cell frequency obtained by individual laboratories and scorers. All laboratories ranked correctly the MNed cell frequency in cells from cultures that were unirradiated, or exposed to 1 or 2Gy of gamma rays. The study also estimated that the intra-scorer median coefficient of variation for duplicate MNed cell frequency scores is 29% for unexposed cultures and 14 and 11% for cells exposed to 1 and 2Gy, respectively. These values can be used as a standard for quality or acceptability of data in future studies. Using a Poisson regression model it was estimated that radiation dose explained 67% of the variance, while staining method, cell sample, laboratory, and covariance explained 0.6, 0.3, 6.5, and 25.6% of the variance, respectively, leaving only 3.1% of the variance unexplained. As part of this exercise, nucleoplasmic bridges were also estimated by the laboratories; however, inexperience in the use of this biomarker of chromosome rearrangement was reflected in the much greater heterogeneity in the data and the unexplained variation estimated by the Poisson model. The results of these studies indicate clearly that even after standardizing culture and scoring conditions it will be necessary to calibrate scorers and laboratories if MN, MNed cell and nucleoplasmic bridge frequencies are to be reliably compared among laboratories and among populations.
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Affiliation(s)
- Michael Fenech
- CSIRO Health Sciences and Nutrition, Adelaide, SA, Australia
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Fenech M, Chang WP, Kirsch-Volders M, Holland N, Bonassi S, Zeiger E. HUMN project: detailed description of the scoring criteria for the cytokinesis-block micronucleus assay using isolated human lymphocyte cultures. Mutat Res 2003; 534:65-75. [PMID: 12504755 DOI: 10.1016/s1383-5718(02)00249-8] [Citation(s) in RCA: 904] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Criteria for scoring micronuclei and nucleoplasmic bridges in binucleated cells in the cytokinesis-block micronucleus assay for isolated human lymphocyte cultures are described in detail. Morphological characteristics of mononucleated cells, binucleated cells, and multinucleated cells as well as necrotic and apoptotic cells and nuclear buds are also described. These criteria are illustrated by a series of schematic diagrams as well as a comprehensive set of colour photographs that are of practical assistance during the scoring of slides. These scoring criteria, diagrams and photographs have been used in a HUman MicronNucleus (HUMN) project inter-laboratory slide-scoring exercise to evaluate the extent of variability that can be attributable to individual scorers and individual laboratories when measuring the frequency of micronuclei and nucleoplasmic bridges in binucleated cells as well as the nuclear division index. The results of the latter study are described in an accompanying paper. It is expected that these scoring criteria will assist in the development of a procedure for calibrating scorers and laboratories so that results from different laboratories for the cytokinesis-block micronucleus assay may be more comparable in the future.
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Affiliation(s)
- M Fenech
- CSIRO Health Sciences and Nutrition, Adelaide, SA, Australia.
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39
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Jabłońska A, Szklarzewicz T, Jankowska W, Kukiełka M, Biliński SM. rDNA amplification in previtellogenic and vitellogenic oocytes of symphylans (Arthropoda, Myriapoda). Folia Histochem Cytobiol 2002; 40:43-6. [PMID: 11885808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023] Open
Abstract
Tube-shaped ovaries of symphylans house numerous developing oocytes that are accompanied by somatic follicular cells. Oocyte nuclei (germinal vesicles) are relatively large and ovoid. During early previtellogenesis they contain compact spherical bodies and lampbrush chromosomes immersed in a translucent karyoplasm. Fluorescent labeling with DAPI and propidium iodide has revealed the presence of both DNA and RNA in the spherical bodies. As previtellogenesis advances, small RNA- and AgNOR-positive nucleoli bud off from these bodies. Full-grown nucleoli consist of coarse-granular material and comprise electron-transparent vacuoles. Our results suggest that in symphylan germinal vesicles amplification of rDNA genes takes place, and that the spherical bodies represent accumulations of extrachromosomal rDNA (rDNA bodies) after commencement of transcriptional activity.
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Affiliation(s)
- A Jabłońska
- Department of Systematic Zoology, Institute of Zoology, Jagiellonian University, Cracow, Poland
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40
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Abstract
Cells often express only one gene from a set of two or more. African trypanosomes appear to accomplish this monoallelic expression by segregating the selected gene into a specific nuclear body. The possibility that such a structure might explain monoallelic expression in other multigene systems is discussed here.
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Affiliation(s)
- Piet Borst
- The Netherlands Cancer Institute, Division of Molecular Biology and Center for Biomedical Genetics, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands.
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41
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Affiliation(s)
- D L Spector
- Cold Spring Harbor Laboratory, NY 11724, USA.
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42
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Medina FJ, Cerdido A, de Cárcer G. The functional organization of the nucleolus in proliferating plant cells. Eur J Histochem 2001; 44:117-31. [PMID: 10968360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023] Open
Abstract
The nucleolus is a prominent nuclear organelle which morphologically expresses all functional steps necessary for the synthesis of ribosomes, from transcription of rRNA genes to the assembly and maturation of preribosomal particles and their transport to the cytoplasm. Structurally, the nucleolus contains some basic components common to practically all cell types, namely fibrillar centers (FCs), the dense fibrillar component (DFC), and the granular component (GC); however, the organization and distribution of these components is highly variable, depending on cell identity and functional status. The different steps of ribosome biogenesis are not strictly correlated with the structural components of the nucleolus. Thus, FCs are most likely the anchoring sites for the accumulation of rDNA, and the sites where the assembly of transcription complexes takes place, but transcription of rRNA genes actually occurs at discrete points in the transition zone between FCs and the DFC. The DFC is a structurally homogeneous, but functionally heterogeneous component in which transcription and some early and advanced steps of pre-rRNA processing develop successively in a gradual fashion, from transition with FCs to transition with the GC. Finally, the GC is the site of the later steps of preribosomal processing, including the final assembly of ribosomal proteins for the export of mature particles to the cytoplasm. The rate of ribosome biogenesis, as well as the structure of the nucleolus, are highly influenced by the proliferation status of the cell, and by factors regulating cell cycle progression. These factors are nucleolar proteins, such as nucleolin, which are targets of signal transduction mechanisms, being at the same time regulators of key steps in preribosome synthesis and processing. Thus, many features of the nucleolus, such as the structural organization of its components, the level and distribution of certain nucleolar proteins and, in general, the rate of ribosome biogenesis, show profound variations throughout cell cycle periods. Particularly interesting is the behavior of the nucleolus during mitosis, in which its structure is disorganized and its activity is stopped, even though the individual transcription and processing complexes are not disassembled, but carried from one cell generation to the next one in such a way that the daughter-cell nucleoli are built with materials coming from the parent-cell nucleolus. Transcription complexes remain assembled at the chromosomal nucleolar organizer in which the rRNA genes are clustered, and processing complexes are carried at the chromosome periphery, and then they are organized into discrete entities called prenucleolar bodies, whose fusion, together with the resumption of transcription and processing, originates the new nucleolus.
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Affiliation(s)
- F J Medina
- Centro de Investigaciones Biológicas (CSIC), Madrid, Spain.
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43
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Melcák I, Melcáková S, Kopský V, Vecerová J, Raska I. Prespliceosomal assembly on microinjected precursor mRNA takes place in nuclear speckles. Mol Biol Cell 2001; 12:393-406. [PMID: 11179423 PMCID: PMC30951 DOI: 10.1091/mbc.12.2.393] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2000] [Revised: 11/03/2000] [Accepted: 12/19/2000] [Indexed: 11/11/2022] Open
Abstract
Nuclear speckles (speckles) represent a distinct nuclear compartment within the interchromatin space and are enriched in splicing factors. They have been shown to serve neighboring active genes as a reservoir of these factors. In this study, we show that, in HeLa cells, the (pre)spliceosomal assembly on precursor mRNA (pre-mRNA) is associated with the speckles. For this purpose, we used microinjection of splicing competent and mutant adenovirus pre-mRNAs with differential splicing factor binding, which form different (pre)spliceosomal complexes and followed their sites of accumulation. Splicing competent pre-mRNAs are rapidly targeted into the speckles, but the targeting is temperature-dependent. The polypyrimidine tract sequence is required for targeting, but, in itself, is not sufficient. The downstream flanking sequences are particularly important for the targeting of the mutant pre-mRNAs into the speckles. In supportive experiments, the behavior of the speckles was followed after the microinjection of antisense deoxyoligoribonucleotides complementary to the specific domains of snRNAs. Under these latter conditions prespliceosomal complexes are formed on endogenous pre-mRNAs. We conclude that the (pre)spliceosomal complexes on microinjected pre-mRNA are formed inside the speckles. Their targeting into and accumulation in the speckles is a result of the cumulative loading of splicing factors to the pre-mRNA and the complexes formed give rise to the speckled pattern observed.
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Affiliation(s)
- I Melcák
- Department of Cell Biology, Institute of Experimental Medicine, Academy of Sciences of Czech Republic, Prague
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44
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Abstract
DNA is highly organized spatially, both within domains of chromatin along each chromosome and within the nucleus as a whole. Recent studies suggest that chromatin localization can affect transcriptional and replicational activity. The similarity between the movements of chromatin nuclear bodies suggests a common mechanism that regulates nuclear dynamics.
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Affiliation(s)
- J R Swedlow
- Division of Gene Regulation and Expression, Wellcome Trust Biocentre, University of Dundee, Dow Street, Dundee, DD1 5EH, UK.
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45
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Abstract
The number and complexity of genes encoding nuclear lamina proteins has increased during metazoan evolution. Emerging evidence reveals that transcriptional repressors such as the retinoblastoma protein, and apoptotic regulators such as CED-4, have functional and dynamic interactions with the lamina. The discovery that mutations in nuclear lamina proteins cause heritable tissue-specific diseases, including Emery-Dreifuss muscular dystrophy, is prompting a fresh look at the nuclear lamina to devise models that can account for its diverse functions and dynamics, and to understand its enigmatic structure.
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Affiliation(s)
- M Cohen
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of Jerusalem, 91904, Jerusalem, Israel
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46
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Tashiro S. [Cold Spring Harbor meeting--Dynamic organization of nuclear function]. Tanpakushitsu Kakusan Koso 2000; 45:2652-4. [PMID: 11185919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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47
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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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Deane JA, Fraunholz M, Su V, Martin W, Durnford DG, McFadden GI. Evidence for nucleomorph to host nucleus gene transfer: light-harvesting complex proteins from cryptomonads and chlorarachniophytes. Protist 2000; 151:239-52. [PMID: 11079769 DOI: 10.1078/1434-4610-00022] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Cryptomonads and chlorarachniophytes acquired photosynthesis independently by engulfing and retaining eukaryotic algal cells. The nucleus of the engulfed cells (known as a nucleomorph) is much reduced and encodes only a handful of the numerous essential plastid proteins normally encoded by the nucleus of chloroplast-containing organisms. In cryptomonads and chlorarachniophytes these proteins are thought to be encoded by genes in the secondary host nucleus. Genes for these proteins were potentially transferred from the nucleomorph (symbiont nucleus) to the secondary host nucleus; nucleus to nucleus intracellular gene transfers. We isolated complementary DNA clones (cDNAs) for chlorophyll-binding proteins from a cryptomonad and a chlorarachniophyte. In each organism these genes reside in the secondary host nuclei, but phylogenetic evidence, and analysis of the targeting mechanisms, suggest the genes were initially in the respective nucleomorphs (symbiont nuclei). Implications for origins of secondary endosymbiotic algae are discussed.
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Affiliation(s)
- J A Deane
- Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Parkville VIC, Australia
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