1
|
Chun Y, Park B, Koh W, Lee S, Cheon Y, Kim R, Che L, Lee S. New centromeric component CENP-W is an RNA-associated nuclear matrix protein that interacts with nucleophosmin/B23 protein. J Biol Chem 2011; 286:42758-42769. [PMID: 22002061 DOI: 10.1074/jbc.m111.228411] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CENP-W was originally identified as a putative oncogene, cancer-upregulated gene 2 (CUG2) that was commonly up-regulated in many cancer tissues. Recently, CENP-W has also been identified as a new centromeric component that interacts with CENP-T. As a complex with CENP-T, CENP-W plays crucial roles in assembly of the functional kinetochore complex. In this study, the subnuclear localization of CENP-W was extensively analyzed using various approaches. We found that ectopically expressed CENP-W primarily accumulated in the nucleolus and remained substantially associated with the nucleolus in stable cells. The following fractionation study also showed that CENP-W is associated with RNA as well as DNA. Moreover, a considerable amount of CENP-W was found in the nuclear mesh-like structure, nuclear matrix, possibly indicating that CENP-W participates in diverse subnuclear activities. Finally, biochemical affinity binding analysis revealed that CENP-W specifically interacts with the nucleolar phosphoprotein, nucleophosmin (B23). Depletion of cellular B23 by siRNA treatment induced a dramatic decrease of CENP-W stability and severe mislocalization during prophase. Our data proposed that B23 may function in the assembly of the kinetochore complex by interacting with CENP-W during interphase.
Collapse
Affiliation(s)
- Younghwa Chun
- Department of Microbiology and Molecular Biology, Chungnam National University, 305-764, Daejeon, Republic of Korea
| | - Byoungwoo Park
- Department of Microbiology and Molecular Biology, Chungnam National University, 305-764, Daejeon, Republic of Korea
| | - Wansoo Koh
- Department of Microbiology and Molecular Biology, Chungnam National University, 305-764, Daejeon, Republic of Korea
| | - Sunhee Lee
- Department of Microbiology and Molecular Biology, Chungnam National University, 305-764, Daejeon, Republic of Korea
| | - Yeongmi Cheon
- Department of Microbiology and Molecular Biology, Chungnam National University, 305-764, Daejeon, Republic of Korea
| | - Raehyung Kim
- Department of Microbiology and Molecular Biology, Chungnam National University, 305-764, Daejeon, Republic of Korea
| | - Lihua Che
- Department of Microbiology and Molecular Biology, Chungnam National University, 305-764, Daejeon, Republic of Korea
| | - Soojin Lee
- Department of Microbiology and Molecular Biology, Chungnam National University, 305-764, Daejeon, Republic of Korea.
| |
Collapse
|
2
|
Rajendra T, Praveen K, Matera AG. Genetic analysis of nuclear bodies: from nondeterministic chaos to deterministic order. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 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] [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.
Collapse
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
| |
Collapse
|
3
|
Conti C, Saccà B, Herrick J, Lalou C, Pommier Y, Bensimon A. Replication fork velocities at adjacent replication origins are coordinately modified during DNA replication in human cells. Mol Biol Cell 2007; 18:3059-67. [PMID: 17522385 PMCID: PMC1949372 DOI: 10.1091/mbc.e06-08-0689] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The spatial organization of replicons into clusters is believed to be of critical importance for genome duplication in higher eukaryotes, but its functional organization still remains to be fully clarified. The coordinated activation of origins is insufficient on its own to account for a timely completion of genome duplication when interorigin distances vary significantly and fork velocities are constant. Mechanisms coordinating origin distribution with fork progression are still poorly elucidated, because of technical difficulties of visualizing the process. Taking advantage of a single molecule approach, we delineated and compared the DNA replication kinetics at the genome level in human normal primary and malignant cells. Our results show that replication forks moving from one origin, as well as from neighboring origins, tend to exhibit the same velocity, although the plasticity of the replication program allows for their adaptation to variable interorigin distances. We also found that forks that emanated from closely spaced origins tended to move slower than those associated with long replicons. Taken together, our results indicate a functional role for origin clustering in the dynamic regulation of genome duplication.
Collapse
Affiliation(s)
- Chiara Conti
- *Department of Genome Stability, Pasteur Institute, Paris F-75724, France
| | - Barbara Saccà
- *Department of Genome Stability, Pasteur Institute, Paris F-75724, France
| | - John Herrick
- *Department of Genome Stability, Pasteur Institute, Paris F-75724, France
| | - Claude Lalou
- Institut National de la Santé et de la Recherche Médicale U532, Hôpital Saint-Louis, Paris 75010, France; and
| | - Yves Pommier
- Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20817
| | - Aaron Bensimon
- *Department of Genome Stability, Pasteur Institute, Paris F-75724, France
| |
Collapse
|
4
|
Abstract
Eukaryotic genomes are distributed on linear chromosomes that are grouped together in the nucleus, an organelle separated from the cytoplasm by a characteristic double membrane studded with large proteinaceous pores. The chromatin within chromosomes has an as yet poorly characterized higher-order structure, but in addition to this, chromosomes and specific subchromosomal domains are nonrandomly positioned in nuclei. This review examines functional implications of the long-range organization of the genome in interphase nuclei. A rigorous test of the physiological importance of nuclear architecture is achieved by introducing mutations that compromise both structure and function. Focussing on such genetic approaches, we address general concepts of interphase nuclear order, the role of the nuclear envelope (NE) and lamins, and finally the importance of spatial organization for DNA replication and heritable gene expression.
Collapse
Affiliation(s)
- Angela Taddei
- University of Geneva, Department of Molecular Biology, CH-1211 Geneva 4, Switzerland
| | | | | | | |
Collapse
|
5
|
Yin X, Landay MF, Han W, Levitan ES, Watkins SC, Levenson RM, Farkas DL, Prochownik EV. Dynamic in vivo interactions among Myc network members. Oncogene 2001; 20:4650-64. [PMID: 11498788 DOI: 10.1038/sj.onc.1204606] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2001] [Revised: 05/03/2001] [Accepted: 05/09/2001] [Indexed: 11/09/2022]
Abstract
Members of the Myc oncoprotein network (c-Myc, Max, and Mad) play important roles in proliferation, differentiation, and apoptosis. We expressed chimeric green fluorescent protein (GFP) fusions of c-Myc, Max, and three Mad proteins in fibroblasts. Individually, c-Myc and Mad proteins localized in subnuclear speckles, whereas Max assumed a homogeneous nuclear pattern. These distributions were co-dominant and dynamic, however, as each protein assumed the pattern of its heterodimeric partner when the latter was co-expressed at a higher level. Deletion mapping of two Mad members, Mad1 and Mxi1, demonstrated that the domains responsible for nuclear localization and speckling are separable. A non-speckling Mxi1 mutant was also less effective as a transcriptional repressor than wild-type Mxi1. c-Myc nuclear speckles were distinct from SC-35 domains involved in mRNA processing. However, in the presence of co-expressed Max, c-Myc, but not Mad, co-localized to a subset of SC-35 loci. These results show that Myc network proteins comprise dynamic subnuclear structures and behave co-dominantly when co-expressed with their normal heterodimerization partners. In addition, c-Myc-Max heterodimers, but not Max-Mad heterodimers, localize to foci actively engaged in pre-mRNA transcription/processing. These findings suggest novel means by which Myc network members promote transcriptional activation or repression.
Collapse
Affiliation(s)
- X Yin
- Section of Hematology/Oncology, Department of Pediatrics, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, PA 15213, USA
| | | | | | | | | | | | | | | |
Collapse
|
6
|
Somanathan S, Suchyna TM, Siegel AJ, Berezney R. Targeting of PCNA to sites of DNA replication in the mammalian cell nucleus. J Cell Biochem 2001; 81:56-67. [PMID: 11180397 DOI: 10.1002/1097-4644(20010401)81:1<56::aid-jcb1023>3.0.co;2-#] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We have examined the targeting of proliferating cell nuclear antigen (PCNA), an integral component of the mammalian replicative enzyme DNA polymerase delta, with sites of DNA replication by using confocal microscopy and computer image analysis. Labeling (5 min pulse) of DNA replication sites in normal human diploid fibroblast cells (NHF1) with BrdU was followed by immunostaining with PCNA antibodies. A striking degree of colocalization was seen between PCNA and the characteristic patterns of DNA replication sites of early, middle and late S-phase (Nakayasu and Berezney [1989] J. Cell. Biol. 108:1-11). These observations were confirmed by quantitative computer image analysis which revealed that approximately 90% of the PCNA-stained area overlapped with DNA replication sites in early S-phase. Pulse-chase experiments, involving in vivo labeling for replication followed by PCNA staining at later time points, suggested that PCNA disassembles from previously replicated sites and targets to newly active sites of DNA replication. To further study this phenomenon in living cells, stable GFP-PCNA transfectants under the control of a tetracycline-inducible promoter were created in mouse 3T6 cells. Like the endogenous PCNA, GFP-PCNA targeted to sites of replication (approximately 80% colocalization) and demonstrated similar dynamic changes following pulse-chase experiments in fixed cells. Studies of living cells revealed progressive changes in the GFP-PCNA distribution that mimic the replication patterns observed in fixed cells. We conclude that GFP-PCNA targets to DNA replication sites in living cells and is an effective marker for tracking the spatio-temporal dynamics of DNA replication as cells transverse the S-phase.
Collapse
Affiliation(s)
- S Somanathan
- Department of Biological Sciences, State University of New York at Buffalo, Buffalo, New York 14260, USA
| | | | | | | |
Collapse
|
7
|
Stichel CC, Augustin M, Kuhn K, Zhu XR, Engels P, Ullmer C, Lubbert H. Parkin expression in the adult mouse brain. Eur J Neurosci 2000. [DOI: 10.1046/j.1460-9568.2000.01314.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
8
|
Enkemann SA, Ward RD, Berger SL. Mobility within the nucleus and neighboring cytosol is a key feature of prothymosin-alpha. J Histochem Cytochem 2000; 48:1341-55. [PMID: 10990488 DOI: 10.1177/002215540004801005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Prothymosin alpha is a small, unfolded, negatively charged, poorly antigenic mammalian protein with a potent nuclear localization signal. Although it is apparently essential for growth, its precise function is unknown. We examined the location and behavior of the protein bearing different epitope tags using in situ immunolocalization in COS-1 and NIH3T3 cells. Tagged prothymosin alpha appeared to be punctate and widely dispersed throughout the nucleus, with the exception of the nucleolus. A tiny cytoplasmic component, which persisted in the presence of cycloheximide and actinomycin D during interphase, became pronounced immediately before, during, and after mitosis. When nuclear uptake was abrogated, small tagged prothymosin alpha molecules, but not prothymosin alpha fused to beta-galactosidase, accumulated significantly in the cytoplasm. Tagged prothymosin alpha shared domains with mobile proteins such as Ran, transportin, and karyopherin beta, which also traverse the nuclear membrane, and co-localized with active RNA polymerase II. Mild digitonin treatment resulted in nuclei devoid of prothymosin alpha. The data do not support tight binding to any nuclear component. Therefore, we propose that prothymosin alpha is a highly diffusible bolus of salt and infer that it facilitates movement of charged molecules in highly charged environments within and near the nucleus.
Collapse
Affiliation(s)
- S A Enkemann
- Section on Genes and Gene Products, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | | | | |
Collapse
|
9
|
Leonhardt H, Rahn HP, Weinzierl P, Sporbert A, Cremer T, Zink D, Cardoso MC. Dynamics of DNA replication factories in living cells. J Cell Biol 2000; 149:271-80. [PMID: 10769021 PMCID: PMC2175147 DOI: 10.1083/jcb.149.2.271] [Citation(s) in RCA: 430] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
DNA replication occurs in microscopically visible complexes at discrete sites (replication foci) in the nucleus. These foci consist of DNA associated with replication machineries, i.e., large protein complexes involved in DNA replication. To study the dynamics of these nuclear replication foci in living cells, we fused proliferating cell nuclear antigen (PCNA), a central component of the replication machinery, with the green fluorescent protein (GFP). Imaging of stable cell lines expressing low levels of GFP-PCNA showed that replication foci are heterogeneous in size and lifetime. Time-lapse studies revealed that replication foci clearly differ from nuclear speckles and coiled bodies as they neither show directional movements, nor do they seem to merge or divide. These four dimensional analyses suggested that replication factories are stably anchored in the nucleus and that changes in the pattern occur through gradual, coordinated, but asynchronous, assembly and disassembly throughout S phase.
Collapse
Affiliation(s)
| | - Hans-Peter Rahn
- Max Delbrück Center for Molecular Medicine, D-13125 Berlin, Germany
| | - Peter Weinzierl
- Institute for Anthropology and Human Genetics, LMU, D-80336 Munich, Germany
| | - Anje Sporbert
- Max Delbrück Center for Molecular Medicine, D-13125 Berlin, Germany
| | - Thomas Cremer
- Institute for Anthropology and Human Genetics, LMU, D-80336 Munich, Germany
| | - Daniele Zink
- Institute for Anthropology and Human Genetics, LMU, D-80336 Munich, Germany
| | | |
Collapse
|
10
|
Sadoni N, Langer S, Fauth C, Bernardi G, Cremer T, Turner BM, Zink D. Nuclear organization of mammalian genomes. Polar chromosome territories build up functionally distinct higher order compartments. J Cell Biol 1999; 146:1211-26. [PMID: 10491386 PMCID: PMC2156120 DOI: 10.1083/jcb.146.6.1211] [Citation(s) in RCA: 207] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We investigated the nuclear higher order compartmentalization of chromatin according to its replication timing (Ferreira et al. 1997) and the relations of this compartmentalization to chromosome structure and the spatial organization of transcription. Our aim was to provide a comprehensive and integrated view on the relations between chromosome structure and functional nuclear architecture. Using different mammalian cell types, we show that distinct higher order compartments whose DNA displays a specific replication timing are stably maintained during all interphase stages. The organizational principle is clonally inherited. We directly demonstrate the presence of polar chromosome territories that align to build up higher order compartments, as previously suggested (Ferreira et al. 1997). Polar chromosome territories display a specific orientation of early and late replicating subregions that correspond to R- or G/C-bands of mitotic chromosomes. Higher order compartments containing G/C-bands replicating during the second half of the S phase display no transcriptional activity detectable by BrUTP pulse labeling and show no evidence of transcriptional competence. Transcriptionally competent and active chromatin is confined to a coherent compartment within the nuclear interior that comprises early replicating R-band sequences. As a whole, the data provide an integrated view on chromosome structure, nuclear higher order compartmentalization, and their relation to the spatial organization of functional nuclear processes.
Collapse
Affiliation(s)
- Nicolas Sadoni
- Institut für Anthropologie und Humangenetik, LMU München, 80336 München, Germany
| | - Sabine Langer
- Institut für Anthropologie und Humangenetik, LMU München, 80336 München, Germany
| | - Christine Fauth
- Institut für Anthropologie und Humangenetik, LMU München, 80336 München, Germany
| | | | - Thomas Cremer
- Institut für Anthropologie und Humangenetik, LMU München, 80333 München, Germany
| | - Bryan M. Turner
- Chromatin and Gene Expression Group, Department of Anatomy, University of Birmingham Medical School, Birmingham B15 2TT, United Kingdom
| | - Daniele Zink
- Institut für Anthropologie und Humangenetik, LMU München, 80336 München, Germany
| |
Collapse
|
11
|
Engel FB, Hauck L, Cardoso MC, Leonhardt H, Dietz R, von Harsdorf R. A mammalian myocardial cell-free system to study cell cycle reentry in terminally differentiated cardiomyocytes. Circ Res 1999; 85:294-301. [PMID: 10436173 DOI: 10.1161/01.res.85.3.294] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cardiomyocytes withdraw from the cell cycle in the early neonatal period, rendering the adult heart incapable to regenerate after injury. In the present study, we report the establishment of a cell-free system to investigate the control of cell cycle reentry in mammalian ventricular cardiomyocyte nuclei and to specifically address the question of whether nuclei from terminally differentiated cardiomyocytes can be stimulated to reenter S phase when incubated with extracts from S-phase cells. Immobilized cardiomyocyte nuclei were incubated with nuclei and cytoplasmic extract of synchronized H9c2 muscle cells or cardiac nonmyocytes. Ongoing DNA synthesis was monitored by biotin-16-dUTP incorporation as well as proliferating cell nuclear antigen expression and localization. Nuclei and cytoplasmic extract from S-phase H9c2 cells but not from H9c2 myotubes induced DNA synthesis in 92% of neonatal cardiomyocyte nuclei. Coincubation in the presence of cycloheximide indicated that de novo translation is required for the reinduction of S phase. Similar results were obtained with adult cardiomyocyte nuclei. When coincubated with both cytoplasmic extract and nuclei or nuclear extracts of S-phase cells, >70% of adult cardiomyocyte nuclei underwent DNA synthesis. In conclusion, these results demonstrate that postmitotic ventricular myocyte nuclei are responsive to stimuli derived from S-phase cells and can thus bypass the cell cycle block. This cell-free system now makes it feasible to analyze the molecular requirements for the release of the cell cycle block and will help to engineer strategies for regenerative growth in cardiac muscle.
Collapse
Affiliation(s)
- F B Engel
- Department of Cardiology, Franz Volhard Clinic, Humboldt University, Berlin, Germany
| | | | | | | | | | | |
Collapse
|
12
|
Kontrogianni-Konstantopoulos A, Leahy PS, Flytzanis CN. Embryonic and post-embryonic utilization and subcellular localization of the nuclear receptor SpSHR2 in the sea urchin. J Cell Sci 1998; 111 ( Pt 15):2159-69. [PMID: 9664037 DOI: 10.1242/jcs.111.15.2159] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
SpSHR2 (Strongylocentrotus purpuratus steroid hormone receptor 2) is a nuclear receptor, encoded by a maternal RNA in the sea urchin embryo. These maternal SpSHR2 transcripts, which are present in all cells, persist until the blastula stage and then are rapidly turned over. A small fraction of the embryonic SpSHR2 protein is maternal, but the majority of this nuclear receptor in the embryo is the product of new synthesis, presumably from the maternal RNA after fertilization. In agreement with the mRNA distribution, the SpSHR2 protein is also detected in all embryonic cells. Contrary to the RNA though, the SpSHR2 protein persists throughout embryonic development to the pluteus stage, long after the mRNA is depleted. Following fertilization and as soon as the 2-cell stage, the cytoplasmic SpSHR2 protein enters rapidly into the embryonic nuclei where it appears in the form of speckles. During subsequent stages (from fourth cleavage onward), SpSHR2 resides in speckled form in both the nucleus and the cytoplasm of the embryonic cells. The cytoplasmic localization of SpSHR2 differs between polarized and non-polarized cells, maintaining an apical position in the ectoderm and endoderm versus a uniform distribution in mesenchyme cells. Following the end of embryonic development (pluteus stage), the SpSHR2 protein is depleted from all tissues. During the ensuing four weeks of larval development, the SpSHR2 is not detected in either the larval or the rudiment cells which will give rise to the adult. Just prior to metamorphosis, at about 35 days post-fertilization, the protein is detected again but in contrast to the uniform distribution in the early embryo, the larval SpSHR2 is specifically expressed in cells of the mouth epithelium and the epaulettes. In adult ovaries and testes, SpSHR2 is specifically detected in the myoepithelial cells surrounding the ovarioles and the testicular acini. Nuclear SpSHR2 in blastula extracts binds to the C1R hormone response element in the upstream promoter region of the CyIIIb actin gene indicating that the latter may be a target of this nuclear receptor in the sea urchin embryo.
Collapse
|
13
|
Zeng C, McNeil S, Pockwinse S, Nickerson J, Shopland L, Lawrence JB, Penman S, Hiebert S, Lian JB, van Wijnen AJ, Stein JL, Stein GS. Intranuclear targeting of AML/CBFalpha regulatory factors to nuclear matrix-associated transcriptional domains. Proc Natl Acad Sci U S A 1998; 95:1585-9. [PMID: 9465059 PMCID: PMC19104 DOI: 10.1073/pnas.95.4.1585] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The AML/CBFalpha runt transcription factors are key regulators of hematopoietic and bone tissue-specific gene expression. These factors contain a 31-amino acid nuclear matrix targeting signal that supports association with the nuclear matrix. We determined that the AML/CBFalpha factors must bind to the nuclear matrix to exert control of transcription. Fusing the nuclear matrix targeting signal to the GAL4 DNA binding domain transactivates a genomically integrated GAL4 responsive reporter gene. These data suggest that AML/CBFalpha must associate with the nuclear matrix to effect transcription. We used fluorescence labeling of epitope-tagged AML-1B (CBFA2) to show it colocalizes with a subset of hyperphosphorylated RNA polymerase II molecules concentrated in foci and linked to the nuclear matrix. This association of AML-1B with RNA polymerase II requires active transcription and a functional DNA binding domain. The nuclear matrix domains that contain AML-1B are distinct from SC35 RNA processing domains. Our results suggest two of the requirements for AML-dependent transcription initiation by RNA polymerase II are association of AML-1B with the nuclear matrix together with specific binding of AML to gene promoters.
Collapse
Affiliation(s)
- C Zeng
- Department of Cell Biology and Cancer Center, University of Massachusetts Medical Center, 55 Lake Avenue North, Worcester, MA 01655, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Cardoso MC, Joseph C, Rahn HP, Reusch R, Nadal-Ginard B, Leonhardt H. Mapping and use of a sequence that targets DNA ligase I to sites of DNA replication in vivo. J Cell Biol 1997; 139:579-87. [PMID: 9348276 PMCID: PMC2141708 DOI: 10.1083/jcb.139.3.579] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The mammalian nucleus is highly organized, and nuclear processes such as DNA replication occur in discrete nuclear foci, a phenomenon often termed "functional organization" of the nucleus. We describe the identification and characterization of a bipartite targeting sequence (amino acids 1-28 and 111-179) that is necessary and sufficient to direct DNA ligase I to nuclear replication foci during S phase. This targeting sequence is located within the regulatory, NH2-terminal domain of the protein and is dispensable for enzyme activity in vitro but is required in vivo. The targeting domain functions position independently at either the NH2 or the COOH termini of heterologous proteins. We used the targeting sequence of DNA ligase I to visualize replication foci in vivo. Chimeric proteins with DNA ligase I and the green fluorescent protein localized at replication foci in living mammalian cells and thus show that these subnuclear functional domains, previously observed in fixed cells, exist in vivo. The characteristic redistribution of these chimeric proteins makes them unique markers for cell cycle studies to directly monitor entry into S phase in living cells.
Collapse
Affiliation(s)
- M C Cardoso
- Department of Nephrology, Hypertension, and Genetics, Franz Volhard Clinic, Max Delbrück Center for Molecular Medicine, Humboldt University, 13125 Berlin, Germany
| | | | | | | | | | | |
Collapse
|
15
|
Wold MS. Replication protein A: a heterotrimeric, single-stranded DNA-binding protein required for eukaryotic DNA metabolism. Annu Rev Biochem 1997; 66:61-92. [PMID: 9242902 DOI: 10.1146/annurev.biochem.66.1.61] [Citation(s) in RCA: 1098] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Replication protein A [RPA; also known as replication factor A (RFA) and human single-stranded DNA-binding protein] is a single-stranded DNA-binding protein that is required for multiple processes in eukaryotic DNA metabolism, including DNA replication, DNA repair, and recombination. RPA homologues have been identified in all eukaryotic organisms examined and are all abundant heterotrimeric proteins composed of subunits of approximately 70, 30, and 14 kDa. Members of this family bind nonspecifically to single-stranded DNA and interact with and/or modify the activities of multiple proteins. In cells, RPA is phosphorylated by DNA-dependent protein kinase when RPA is bound to single-stranded DNA (during S phase and after DNA damage). Phosphorylation of RPA may play a role in coordinating DNA metabolism in the cell. RPA may also have a role in modulating gene expression.
Collapse
Affiliation(s)
- M S Wold
- Department of Biochemistry, University of Iowa College of Medicine, Iowa City 52242, USA.
| |
Collapse
|