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Pomatto LCD, Tower J, Davies KJA. Sexual Dimorphism and Aging Differentially Regulate Adaptive Homeostasis. J Gerontol A Biol Sci Med Sci 2018; 73:141-149. [PMID: 28525535 PMCID: PMC5861879 DOI: 10.1093/gerona/glx083] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 04/26/2017] [Indexed: 11/13/2022] Open
Abstract
External and internal stimuli cause modifications to gene and biochemical pathways. In turn, demonstrating that biological systems continuously make short-term adaptations both to set-points, and to the range of "normal" capacity, due to mild conditional changes, or to subtoxic, nondamaging levels of chemical agents. This is termed as "Adaptive Homeostasis," defined with the following: "The transient expansion or contraction of the homeostatic range in response to exposure to sub-toxic, nondamaging, signaling molecules or events, or the removal or cessation of such molecules or events." Research from several laboratories, including our own, found that adaptive homeostasis declines with age in organisms as diverse as worms, flies, and mammals, and decreases with senescence in mammalian cell cultures. We suggest that diminishing adaptive homeostasis may play a causal role as a factor responsible for the aging phenotype. Furthermore, although studies of humans, animals, and model organisms are often limited to a single sex, and cell culture studies may even be conducted with lines whose donor's sex was unknown, studies reveal distinct sexual dimorphism in adaptive homeostasis. Interestingly, although young males and females may exhibit dramatic differences in adaptive capacities and/or preferences, these distinctions are lost with age as adaptive homeostasis patterns converge.
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Affiliation(s)
- Laura C D Pomatto
- Leonard Davis School of Gerontology of the Ethel Percy Andrus Gerontology Center
| | - John Tower
- Leonard Davis School of Gerontology of the Ethel Percy Andrus Gerontology Center
- Molecular and Computational Biology Program, Department of Biological Sciences, Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California
| | - Kelvin J A Davies
- Leonard Davis School of Gerontology of the Ethel Percy Andrus Gerontology Center
- Molecular and Computational Biology Program, Department of Biological Sciences, Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California
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2
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Abstract
The heat-shock response is a key factor in diverse stress scenarios, ranging from hyperthermia to protein folding diseases. However, the complex dynamics of this physiological response have eluded mathematical modeling efforts. Although several computational models have attempted to characterize the heat-shock response, they were unable to model its dynamics across diverse experimental datasets. To address this limitation, we mined the literature to obtain a compendium of in vitro hyperthermia experiments investigating the heat-shock response in HeLa cells. We identified mechanisms previously discussed in the experimental literature, such as temperature-dependent transcription, translation, and heat-shock factor (HSF) oligomerization, as well as the role of heat-shock protein mRNA, and constructed an expanded mathematical model to explain the temperature-varying DNA-binding dynamics, the presence of free HSF during homeostasis and the initial phase of the heat-shock response, and heat-shock protein dynamics in the long-term heat-shock response. In addition, our model was able to consistently predict the extent of damage produced by different combinations of exposure temperatures and durations, which were validated against known cellular-response patterns. Our model was also in agreement with experiments showing that the number of HSF molecules in a HeLa cell is roughly 100 times greater than the number of stress-activated heat-shock element sites, further confirming the model’s ability to reproduce experimental results not used in model calibration. Finally, a sensitivity analysis revealed that altering the homeostatic concentration of HSF can lead to large changes in the stress response without significantly impacting the homeostatic levels of other model components, making it an attractive target for intervention. Overall, this model represents a step forward in the quantitative understanding of the dynamics of the heat-shock response.
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3
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Yang N, Caratti G, Ince LM, Poolman TM, Trebble PJ, Holt CM, Ray DW, Matthews LC. Serum cholesterol selectively regulates glucocorticoid sensitivity through activation of JNK. J Endocrinol 2014; 223:155-66. [PMID: 25161081 PMCID: PMC4191185 DOI: 10.1530/joe-14-0456] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Glucocorticoids (Gc) are potent anti-inflammatory agents with wide clinical application. We have previously shown that increased serum concentration significantly attenuates regulation of a simple Gc-responsive reporter. We now find that glucocorticoid receptor (GR) regulation of some endogenous transactivated but not transrepressed genes is impaired, suggesting template specificity. Serum did not directly affect GR expression, activity or trafficking, implicating GR crosstalk with other signalling pathways. Indeed, a JNK inhibitor completely abolished the serum effect. We identified the Gc modulating serum component as cholesterol. Cholesterol loading mimicked the serum effect, which was readily reversed by JNK inhibition. Chelation of serum cholesterol with methyl-β-cyclodextrin or inhibition of cellular cholesterol synthesis with simvastatin potentiated the Gc response. To explore the effect in vivo we used ApoE(-/-) mice, a model of hypercholesterolaemia. Consistent with our in vitro studies, we find no impact of elevated cholesterol on the expression of GR, or on the hypothalamic-pituitary-adrenal axis, measured by dexamethasone suppression test. Instead we find selective Gc resistance on some hepatic target genes in ApoE(-/-) mice. Therefore, we have discovered an unexpected role for cholesterol as a selective modulator of Gc action in vivo. Taken together these findings reveal a new environmental constraint on Gc action with relevance to both inflammation and cancer.
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Affiliation(s)
- Nan Yang
- Manchester Centre for Nuclear Hormone Research in Disease and Institute of Human DevelopmentFaculty of Medical and Human Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester, M13 9PT, UKInstitute of Cardiovascular SciencesFaculty of Medical and Human Sciences, University of Manchester, CTF Building, Grafton Street, Manchester, M13 9PT, UK
| | - Giorgio Caratti
- Manchester Centre for Nuclear Hormone Research in Disease and Institute of Human DevelopmentFaculty of Medical and Human Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester, M13 9PT, UKInstitute of Cardiovascular SciencesFaculty of Medical and Human Sciences, University of Manchester, CTF Building, Grafton Street, Manchester, M13 9PT, UK
| | - Louise M Ince
- Manchester Centre for Nuclear Hormone Research in Disease and Institute of Human DevelopmentFaculty of Medical and Human Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester, M13 9PT, UKInstitute of Cardiovascular SciencesFaculty of Medical and Human Sciences, University of Manchester, CTF Building, Grafton Street, Manchester, M13 9PT, UK
| | - Toryn M Poolman
- Manchester Centre for Nuclear Hormone Research in Disease and Institute of Human DevelopmentFaculty of Medical and Human Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester, M13 9PT, UKInstitute of Cardiovascular SciencesFaculty of Medical and Human Sciences, University of Manchester, CTF Building, Grafton Street, Manchester, M13 9PT, UK
| | - Peter J Trebble
- Manchester Centre for Nuclear Hormone Research in Disease and Institute of Human DevelopmentFaculty of Medical and Human Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester, M13 9PT, UKInstitute of Cardiovascular SciencesFaculty of Medical and Human Sciences, University of Manchester, CTF Building, Grafton Street, Manchester, M13 9PT, UK
| | - Cathy M Holt
- Manchester Centre for Nuclear Hormone Research in Disease and Institute of Human DevelopmentFaculty of Medical and Human Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester, M13 9PT, UKInstitute of Cardiovascular SciencesFaculty of Medical and Human Sciences, University of Manchester, CTF Building, Grafton Street, Manchester, M13 9PT, UK
| | - David W Ray
- Manchester Centre for Nuclear Hormone Research in Disease and Institute of Human DevelopmentFaculty of Medical and Human Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester, M13 9PT, UKInstitute of Cardiovascular SciencesFaculty of Medical and Human Sciences, University of Manchester, CTF Building, Grafton Street, Manchester, M13 9PT, UK
| | - Laura C Matthews
- Manchester Centre for Nuclear Hormone Research in Disease and Institute of Human DevelopmentFaculty of Medical and Human Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester, M13 9PT, UKInstitute of Cardiovascular SciencesFaculty of Medical and Human Sciences, University of Manchester, CTF Building, Grafton Street, Manchester, M13 9PT, UK
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4
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Di Giammartino DC, Shi Y, Manley JL. PARP1 represses PAP and inhibits polyadenylation during heat shock. Mol Cell 2012; 49:7-17. [PMID: 23219533 DOI: 10.1016/j.molcel.2012.11.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 09/21/2012] [Accepted: 11/01/2012] [Indexed: 11/16/2022]
Abstract
The 3' ends of most eukaryotic mRNAs are produced by an endonucleolytic cleavage followed by synthesis of a poly(A) tail. Poly(A) polymerase (PAP), the enzyme that catalyzes the formation of the tail, is subject to tight regulation involving several posttranslational modifications. Here we show that the enzyme poly(ADP-ribose) polymerase 1 (PARP1) modifies PAP and regulates its activity both in vitro and in vivo. PARP1 binds to and modifies PAP by poly(ADP-ribosyl)ation (PARylation) in vitro, which inhibits PAP activity. In vivo we show that PAP is PARylated during heat shock, leading to inhibition of polyadenylation in a PARP1-dependent manner. The observed inhibition reflects reduced RNA binding affinity of PARylated PAP in vitro and decreased PAP association with non-heat shock protein-encoding genes in vivo. Our results provide direct evidence that PARylation can control processing of mRNA precursors, and also identify PARP1 as a regulator of polyadenylation during thermal stress.
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5
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Sakharov DA, Maltseva DV, Riabenko EA, Shkurnikov MU, Northoff H, Tonevitsky AG, Grigoriev AI. Passing the anaerobic threshold is associated with substantial changes in the gene expression profile in white blood cells. Eur J Appl Physiol 2011; 112:963-72. [PMID: 21717121 DOI: 10.1007/s00421-011-2048-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Accepted: 06/09/2011] [Indexed: 12/16/2022]
Abstract
High and moderate intensity endurance exercise alters gene expression in human white blood cells (WBCs), but the understanding of how this effect occurs is limited. To increase our knowledge of the nature of this process, we investigated the effects of passing the anaerobic threshold (AnT) on the gene expression profile in WBCs of athletes. Nineteen highly trained skiers participated in a treadmill test with an incremental step protocol until exhaustion (ramp test to exhaustion, RTE). The average total time to exhaustion was 14:40 min and time after AnT was 4:50 min. Two weeks later, seven of these skiers participated in a moderate treadmill test (MT) at 80% peak O(2) uptake for 30 min, which was slightly below their AnTs. Blood samples were obtained before and immediately after both tests. RTE was associated with substantially greater leukocytosis and acidosis than MT. Gene expression in WBCs was measured using whole genome microarray expression analysis before and immediately after each test. A total of 310 upregulated genes were found after RTE, and 69 genes after MT of which 64 were identical to RTE. Both tests influenced a variety of known gene pathways related to inflammation, stress response, signal transduction and apoptosis. A large group of differentially expressed previously unknown small nucleolar RNA and small Cajal body RNA was found. In conclusion, a 15-min test to exhaustion was associated with substantially greater changes of gene expression than a 30-min test just below the AnT.
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Affiliation(s)
- Dmitry A Sakharov
- Department of Molecular Physiology, Russian Research Institute of Physical Education and Sport, Elizavetinsky lane 10, Moscow, Russia.
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6
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Mazroui R, Di Marco S, Kaufman RJ, Gallouzi IE. Inhibition of the ubiquitin-proteasome system induces stress granule formation. Mol Biol Cell 2007; 18:2603-18. [PMID: 17475769 PMCID: PMC1924830 DOI: 10.1091/mbc.e06-12-1079] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The inhibition of the ubiquitin-dependent proteasome system (UPS) via specific drugs is one type of approach used to combat cancer. Although it has been suggested that UPS inhibition prevents the rapid decay of AU-rich element (ARE)-containing messages, very little is known about the cellular mechanisms leading to this effect. Here we establish a link between the inhibition of UPS activity, the formation of cytoplasmic stress granules (SGs), and mRNA metabolism. The assembly of the SGs requires the phosphorylation of the translation initiation factor eIF2alpha by a mechanism involving the stress kinase GCN2. On prolonged UPS inhibition and despite the maintenance of eIF2alpha phosphorylation, SGs disassemble and translation recovers in an Hsp72 protein-dependent manner. The formation of these SGs coincides with the disassembly of processing bodies (PBs), known as mRNA decay entities. As soon as the SGs assemble, they recruit ARE-containing messages such as p21(cip1) mRNA, which are stabilized under these conditions. Hence, our findings suggest that SGs could be considered as one of the players that mediate the early response of the cell to proteasome inhibitors by interfering temporarily with mRNA decay pathways.
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Affiliation(s)
- Rachid Mazroui
- *McGill University, Department of Biochemistry, Montreal, Quebec, H3G 1Y6, Canada; and
| | - Sergio Di Marco
- *McGill University, Department of Biochemistry, Montreal, Quebec, H3G 1Y6, Canada; and
| | - Randal J. Kaufman
- Howard Hughes Medical Institute, University of Michigan Medical Center, Ann Arbor, MI 48109
| | - Imed-Eddine Gallouzi
- *McGill University, Department of Biochemistry, Montreal, Quebec, H3G 1Y6, Canada; and
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Jeyaraj S, Dakhlallah D, Hill SR, Lee BS. HuR stabilizes vacuolar H+-translocating ATPase mRNA during cellular energy depletion. J Biol Chem 2005; 280:37957-64. [PMID: 16155006 PMCID: PMC1351387 DOI: 10.1074/jbc.m502883200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
V-ATPases are multisubunit membrane proteins that use ATP binding and hydrolysis to transport protons across membranes against a concentration gradient. Although some cell types express plasma membrane forms of these transporters, all eukaryotes require V-ATPases to maintain an acidic pH in membrane-bound compartments of endocytic and secretory networks to facilitate protein trafficking and processing. Mammalian cells that completely lack V-ATPases are not viable; yet, the abundance of V-ATPases can differ among cell types by an order of magnitude or more, requiring precise control of their expression. We previously showed that mRNA stability appears to play a major role in regulating overall abundance of V-ATPases. In this report, we demonstrate that the stability of V-ATPase mRNA is regulated through AU-rich elements in 3'-untranslated regions. Unlike some mRNAs that are short-lived due to the presence of these elements, V-ATPase mRNAs have half-lives of hours to days. However, during stress induced by ATP depletion, AU-rich elements are necessary to maintain stability of these transcripts and their presence in the cytoplasm. HuR, an RNA-binding protein that interacts with and stabilizes AU-rich mRNAs, shows increased binding to some V-ATPase mRNAs during ATP depletion. siRNA-mediated knockdown of HuR results in diminished V-ATPase expression. These results indicate that AU-rich elements and associated proteins can play a role in regulation of even very stable mRNAs by protecting against loss during cellular stress.
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Affiliation(s)
- Selvi Jeyaraj
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, 43210, USA
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8
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Temme C, Zaessinger S, Meyer S, Simonelig M, Wahle E. A complex containing the CCR4 and CAF1 proteins is involved in mRNA deadenylation in Drosophila. EMBO J 2004; 23:2862-71. [PMID: 15215893 PMCID: PMC514940 DOI: 10.1038/sj.emboj.7600273] [Citation(s) in RCA: 177] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2004] [Accepted: 05/24/2004] [Indexed: 11/08/2022] Open
Abstract
The CCR4-NOT complex is the major enzyme catalyzing mRNA deadenylation in Saccharomyces cerevisiae. We have identified homologs for almost all subunits of this complex in the Drosophila genome. Biochemical fractionation showed that the two likely catalytic subunits, CCR4 and CAF1, were associated with each other and with a poly(A)-specific 3' exonuclease activity. In Drosophila, the CCR4 and CAF1 proteins were ubiquitously expressed and present in cytoplasmic foci. Individual knock-down of several potential subunits of the Drosophila CCR4-NOT complex by RNAi in tissue culture cells led to a lengthening of bulk mRNA poly(A) tails. Knock-down of two individual subunits also interfered with the rapid deadenylation of Hsp70 mRNA during recovery from heat shock. Similarly, ccr4 mutant flies had elongated bulk poly(A) and a defect in Hsp70 mRNA deadenylation. A minor increase in bulk poly(A) tail length was also observed in Rga mutant flies, which are affected in the NOT2 subunit. The data show that the CCR4-NOT complex is conserved in Drosophila melanogaster and plays a role in general and regulated mRNA deadenylation.
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Affiliation(s)
- Claudia Temme
- Institut für Biochemie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
| | - Sophie Zaessinger
- Génétique du Développement de la Drosophile, Institut de Génétique Humaine, Montpellier, France
| | - Sylke Meyer
- Institut für Biochemie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
| | - Martine Simonelig
- Génétique du Développement de la Drosophile, Institut de Génétique Humaine, Montpellier, France
| | - Elmar Wahle
- Institut für Biochemie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
- Institut für Biochemie, Martin-Luther-Universität, Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120 Halle, Germany. Tel.: +49 345 552 4920; Fax: +49 345 552 7014; E-mail:
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9
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Tran H, Maurer F, Nagamine Y. Stabilization of urokinase and urokinase receptor mRNAs by HuR is linked to its cytoplasmic accumulation induced by activated mitogen-activated protein kinase-activated protein kinase 2. Mol Cell Biol 2003; 23:7177-88. [PMID: 14517288 PMCID: PMC230330 DOI: 10.1128/mcb.23.20.7177-7188.2003] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mRNAs of urokinase plasminogen activator (uPA) and its receptor, uPAR, contain instability-determining AU-rich elements (AREs) in their 3' untranslated regions. The cellular proteins binding to these RNA sequences (ARE(uPA/uPAR)) are not known. We show here that the mRNA-stabilizing factor HuR functionally interacts with these sequences. HuR stabilized an ARE(uPA)-containing RNA substrate in vitro and stabilized in HeLa Tet-off cells both endogenous uPA and uPAR mRNAs and a beta-globin reporter mRNA containing the ARE(uPA). RNAi-mediated depletion of HuR in BT-549 and MDA-MB-231 cells significantly reduced the steady-state levels of endogenous uPA and uPAR mRNAs. Furthermore, we show that a constitutively active form of mitogen-activated protein kinase-activated protein kinase 2 (MK2), MK2-EE, has an ARE-mRNA-stabilizing effect that correlates with its ability to enhance the cytoplasmic accumulation of endogenous HuR, but not in cells cotransfected with a dominant negative version of MK2, MK2-K76R. These effects were mimicked by hydrogen peroxide treatment (oxidative stress), which resulted in the phosphorylation of endogenous MK2. In addition, hydrogen peroxide treatment enhanced the cytoplasmic binding of HuR to the ARE(uPA), which was abrogated in cells transfected with MK2-K76R. These results indicate a role for HuR and MK2 in regulating the expression of uPA and uPAR genes at the posttranscriptional level.
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MESH Headings
- Antigens, Surface
- Blotting, Northern
- Blotting, Western
- Cell Line
- Cell Line, Tumor
- Cytoplasm/metabolism
- Doxycycline/pharmacology
- ELAV Proteins
- ELAV-Like Protein 1
- Enzyme Activation
- Gene Expression Regulation, Enzymologic
- Genes, Dominant
- Genetic Vectors
- Glutathione Transferase/metabolism
- HeLa Cells
- Humans
- Hydrogen Peroxide/pharmacology
- Intracellular Signaling Peptides and Proteins
- Microscopy, Fluorescence
- Mitogen-Activated Protein Kinases/metabolism
- Models, Genetic
- Oxidative Stress
- Precipitin Tests
- Protein Binding
- Protein Kinases
- Protein Serine-Threonine Kinases
- RNA/metabolism
- RNA, Messenger/metabolism
- RNA-Binding Proteins/metabolism
- Receptors, Cell Surface/metabolism
- Receptors, Urokinase Plasminogen Activator
- Recombinant Proteins/metabolism
- Signal Transduction
- Time Factors
- Transcription, Genetic
- Transfection
- Ultraviolet Rays
- Urokinase-Type Plasminogen Activator/metabolism
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Affiliation(s)
- Hoanh Tran
- Friedrich Miescher Institute for Biomedical Research, Novartis Research Foundation, CH-4058 Basel, Switzerland
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10
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Brennan CM, Gallouzi IE, Steitz JA. Protein ligands to HuR modulate its interaction with target mRNAs in vivo. J Cell Biol 2000; 151:1-14. [PMID: 11018049 PMCID: PMC2189805 DOI: 10.1083/jcb.151.1.1] [Citation(s) in RCA: 300] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2000] [Accepted: 08/15/2000] [Indexed: 02/08/2023] Open
Abstract
AU-rich elements (AREs) present in the 3' untranslated regions of many protooncogene, cytokine, and lymphokine messages target them for rapid degradation. HuR, a ubiquitously expressed member of the ELAV (embryonic lethal abnormal vision) family of RNA binding proteins, selectively binds AREs and stabilizes ARE-containing mRNAs in transiently transfected cells. Here, we identify four mammalian proteins that bind regions of HuR known to be essential for its ability to shuttle between the nucleus and the cytoplasm and to stabilize mRNA: SETalpha, SETbeta, pp32, and acidic protein rich in leucine (APRIL). Three have been reported to be protein phosphatase 2A inhibitors. All four ligands contain long, acidic COOH-terminal tails, while pp32 and APRIL share a second motif: rev-like leucine-rich repeats in their NH(2)-terminal regions. We show that pp32 and APRIL are nucleocytoplasmic shuttling proteins that interact with the nuclear export factor CRM1 (chromosomal region maintenance protein 1). The inhibition of CRM1 by leptomycin B leads to the nuclear retention of pp32 and APRIL, their increased association with HuR, and an increase in HuR's association with nuclear poly(A)+ RNA. Furthermore, transcripts from the ARE-containing c-fos gene are selectively retained in the nucleus, while the cytoplasmic distribution of total poly(A)+ RNA is not altered. These data provide evidence that interaction of its ligands with HuR modulate HuR's ability to bind its target mRNAs in vivo and suggest that CRM1 is instrumental in the export of at least some cellular mRNAs under certain conditions. We discuss the possible role of these ligands upstream of HuR in pathways that govern the stability of ARE-containing mRNAs.
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Affiliation(s)
- C M Brennan
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536, USA
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11
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Gallouzi IE, Brennan CM, Stenberg MG, Swanson MS, Eversole A, Maizels N, Steitz JA. HuR binding to cytoplasmic mRNA is perturbed by heat shock. Proc Natl Acad Sci U S A 2000; 97:3073-8. [PMID: 10737787 PMCID: PMC16194 DOI: 10.1073/pnas.97.7.3073] [Citation(s) in RCA: 265] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
AU-rich elements (AREs) located in the 3' untranslated region target the mRNAs encoding many protooncoproteins, cytokines, and lymphokines for rapid degradation. HuR, a ubiquitously expressed member of the embryonic lethal abnormal vision (ELAV) family of RNA-binding proteins, binds ARE sequences and selectively stabilizes ARE-containing reporter mRNAs when overexpressed in transiently transfected cells. HuR appears predominantly nucleoplasmic but has been shown to shuttle between the nucleus and cytoplasm via a novel shuttling sequence HNS. We report generation of a mouse monoclonal antibody 3A2 that both immunoblots and immunoprecipitates HuR protein; it recognizes an epitope located in the first of HuR's three RNA recognition motifs. This antibody was used to probe HuR interactions with mRNA before and after heat shock, a condition that has been reported to stabilize ARE-containing mRNAs. At 37 degrees C, approximately one-third of the cytoplasmic HuR appears polysome associated, and in vivo UV crosslinking reveals that HuR interactions with poly(A)(+) RNA are predominantly cytoplasmic rather than nuclear. This comprises evidence that HuR directly interacts with mRNA in vivo. After heat shock, 12-15% of HuR accumulates in discrete foci in the cytoplasm, but surprisingly the majority of HuR crosslinks instead to nuclear poly(A)(+) RNA, whose levels are dramatically increased in the stressed cells. This behavior of HuR differs from that of another ARE-binding protein, hnRNP D, which has been implicated as an effector of mRNA decay rather than mRNA stabilization and of the general pre-RNA-binding protein hnRNP A1. We interpret these differences to mean that the temporal association of HuR with ARE-containing mRNAs is different from that of these other two proteins.
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Affiliation(s)
- I E Gallouzi
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
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12
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Le YJ, Corry PM. Hypoxia-induced bFGF gene expression is mediated through the JNK signal transduction pathway. Mol Cell Biochem 1999; 202:1-8. [PMID: 10705989 DOI: 10.1023/a:1007059806016] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Although the synthesis of angiogenic factors in hypoxic regions of solid tumors is recognized as one of the critical steps in tumor growth and metastasis, the signal transduction pathway involved in hypoxic induction of basic fibroblast growth factor (bFGF) gene expression is still obscure. In the study described here, we investigated the intracellular responses to hypoxia and the mechanisms triggering the initiation of angiogenic activity in drug-resistant human breast carcinoma MCF-7/ADR cells. Northern blots showed an increase in the level of c-jun, c-fos, and bFGF mRNA during hypoxia. Gel mobility-shift analysis of nuclear extracts from hypoxia-exposed cells showed an increase in AP-1 binding activity. In addition, hypoxic treatment strongly activated c-Jun N-terminal kinase 1 (JNK1), leading to phosphorylation and activation of c-Jun. Expression of a dominant negative mutant of JNK1 suppressed hypoxia-induced JNK1 activation as well as bFGF gene expression. Taken together, hypoxia-induced bFGF gene expression is mediated through the stress-activated protein kinase (SAPK) signal transduction pathway.
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Affiliation(s)
- Y J Le
- Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan 48073, USA
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13
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Gupta AK, Lee YJ, Galoforo SS, Berns CM, Martinez AA, Corry PM, Wu X, Guan KL. Differential effect of glucose deprivation on MAPK activation in drug sensitive human breast carcinoma MCF-7 and multidrug resistant MCF-7/ADR cells. Mol Cell Biochem 1997; 170:23-30. [PMID: 9144315 DOI: 10.1023/a:1006890316102] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have investigated the effect of glucose deprivation treatment on the activation of mitogen activated protein kinases (MAPKs) in the drug-sensitive human breast carcinoma cells (MCF-7) and its drug resistant variant (MCF-7/ADR) cells. Western blots and in-gel kinase assays showed that glucose free medium was a strong stimulus for the activation of MAPK in MCF-7/ADR cells. No activation was seen in MCF-7 cells. MAPK was activated within 3 min of being in glucose free medium and it remained activated for over 1 h in MCF-7/ADR cells. After being returned to complete medium, 1 h was required for the MAPK to become deactivated. To investigate whether alternative sources of ATP could inhibit glucose deprivation induced MAPK activation, we added glutamine and glutamate to glucose deprived medium. The addition of glutamine did not reverse glucose deprivation induced MAPK activation in MCF-7/ADR cells. The addition of glutamate, however, decreased the MAPK activation and the length of time of activation. We observed an increase greater than three fold in MEK, Raf, Ras, and PKC activity with glucose deprivation in MCF-7/ADR cells. This suggests that glucose deprivation-induced MAPK activation is mediated through this signal transduction pathway.
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Affiliation(s)
- A K Gupta
- Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan 48073, USA
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Goswami PC, Roti Roti JL, Hunt CR. The cell cycle-coupled expression of topoisomerase IIalpha during S phase is regulated by mRNA stability and is disrupted by heat shock or ionizing radiation. Mol Cell Biol 1996; 16:1500-8. [PMID: 8657123 PMCID: PMC231134 DOI: 10.1128/mcb.16.4.1500] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Topoisomerase II is a multifunctional protein required during DNA replication, chromosome disjunction at mitosis, and other DNA-related activities by virtue of its ability to alter DNA supercoiling. The enzyme is encoded by two similar but nonidentical genes: the topoisomerase IIalpha and IIbeta genes. In HeLa cells synchronized by mitotic shake-off, topoisomeraseII alpha mRNA levels were found to vary as a function of cell cycle position, being 15-fold higher in late S phase (14 to 18 h postmitosis) than during G1 phase. Also detected was a corresponding increase in topoisomerase IIalpha protein synthesis at 14 to 18 h postmitosis which resulted in significantly higher accumulation of the protein during S and G2 phases. Topoisomerase IIalpha expression was not dependent on DNA synthesis during S phase, which could be inhibited without effect on the timing or level of mRNA expression. Mechanistically, topoisomerase IIalpha expression appears to be coupled to cell cycle position mainly through associated changes in mRNA stability. When cells are in S phase and mRNA levels are maximal, the half-life of topoisomerase IIalpha mRNA was determined to be approximately 30 min. A similar decrease in mRNA stability was also induced by two external factors known to delay cell cycle progression. Treatment of S-phase cells, at the time of maximum topoisomerase IIalpha mRNA stability, with either ionizing radiation (5 Gy) or heat shock (45 degrees C for 15 min) caused the accumulated topoisomerase IIalpha mRNA to decay. This finding suggests a potential relationship between stress-induced decreases in topoisomerase IIalpha expression and cell cycle progression delays in late S/G2.
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Affiliation(s)
- P C Goswami
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63108, USA
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15
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Galoforo SS, Berns CM, Erdos G, Corry PM, Lee YJ. Hypoglycemia-induced AP-1 transcription factor and basic fibroblast growth factor gene expression in multidrug resistant human breast carcinoma MCF-7/ADR cells. Mol Cell Biochem 1996; 155:163-71. [PMID: 8700161 DOI: 10.1007/bf00229313] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We investigated the effect of hypoglycemic treatment on the activation of the AP-1 transcription factors and the regulation of basic fibroblast growth factor (bFGF) gene expression in multidrug resistant human breast carcinoma MCF-7/ADR cells. Northern blot and gel mobility shift assays showed that hypoglycemic treatment induced c-jun and c-fos gene expression, AP-1 binding activity, as well as bFGF gene expression. Moreover, transfected cells expressing high levels of abnormal c-Jun protein exhibited a reduction in the bFGF protein levels compared to parental cells. A potent protein kinase C (PKC) inhibitor, H-7 (60 micrograms/ml) suppressed the stress-induced bFGF gene expression. Our study also demonstrated that H-7 did not facilitate the decay of bFGF mRNA. Thus, the suppression of bFGF gene expression by treatment with H-7 was due to the effect of the drug on the synthesis of bFGF mRNA rather than the stability of bFGF mRNA. Our data suggest that hypoglycemia-induced bFGF gene expression is mediated through the activation of PKC and the AP-1 transcription factors.
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Affiliation(s)
- S S Galoforo
- Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI 48073, USA
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16
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Preferential deadenylation of Hsp70 mRNA plays a key role in regulating Hsp70 expression in Drosophila melanogaster. Mol Cell Biol 1994. [PMID: 7515148 DOI: 10.1128/mcb.14.6.3646] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Following a standard heat shock, approximately 40% of Hsp70 transcripts in Drosophila melanogaster lack a poly(A) tail. Since heat shock disrupts other aspects of RNA processing, this observation suggested that heat might disrupt polyadenylation as well. We find, however, that as the temperature is increased a larger fraction of Hsp70 RNA is polyadenylated. Poly(A)-deficient Hsp70 RNAs arise not from a failure in polyadenylation but from the rapid and selective removal of poly(A) from previously adenylated transcripts. Poly(A) removal is highly regulated: poly(A) is (i) removed much more rapidly from Hsp70 RNAs than from Hsp23 RNAs, (ii) removed more rapidly after mild heat shocks than after severe heat shocks, and (iii) removed more rapidly after a severe heat shock if cells have first been conditioned by a mild heat treatment. Poly(A) seems to be removed by simple deadenylation rather than by endonucleolytic cleavage 5' of the adenylation site. During recovery from heat shock, deadenylation is rapidly followed by degradation. In cells maintained at high temperatures, however, the two processes are uncoupled and Hsp70 RNAs are deadenylated without being degraded. These deadenylated mRNAs are translated with low efficiency. Deadenylation therefore allows Hsp70 synthesis to be repressed even when degradation of the mRNA is blocked. Poly(A) tail shortening appears to play a key role in regulating Hsp70 expression.
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17
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Dellavalle RP, Petersen R, Lindquist S. Preferential deadenylation of Hsp70 mRNA plays a key role in regulating Hsp70 expression in Drosophila melanogaster. Mol Cell Biol 1994; 14:3646-59. [PMID: 7515148 PMCID: PMC358732 DOI: 10.1128/mcb.14.6.3646-3659.1994] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Following a standard heat shock, approximately 40% of Hsp70 transcripts in Drosophila melanogaster lack a poly(A) tail. Since heat shock disrupts other aspects of RNA processing, this observation suggested that heat might disrupt polyadenylation as well. We find, however, that as the temperature is increased a larger fraction of Hsp70 RNA is polyadenylated. Poly(A)-deficient Hsp70 RNAs arise not from a failure in polyadenylation but from the rapid and selective removal of poly(A) from previously adenylated transcripts. Poly(A) removal is highly regulated: poly(A) is (i) removed much more rapidly from Hsp70 RNAs than from Hsp23 RNAs, (ii) removed more rapidly after mild heat shocks than after severe heat shocks, and (iii) removed more rapidly after a severe heat shock if cells have first been conditioned by a mild heat treatment. Poly(A) seems to be removed by simple deadenylation rather than by endonucleolytic cleavage 5' of the adenylation site. During recovery from heat shock, deadenylation is rapidly followed by degradation. In cells maintained at high temperatures, however, the two processes are uncoupled and Hsp70 RNAs are deadenylated without being degraded. These deadenylated mRNAs are translated with low efficiency. Deadenylation therefore allows Hsp70 synthesis to be repressed even when degradation of the mRNA is blocked. Poly(A) tail shortening appears to play a key role in regulating Hsp70 expression.
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Affiliation(s)
- R P Dellavalle
- Department of Molecular Genetics and Cell Biology, Howard Hughes Medical Institute, University of Chicago, Illinois 60637
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18
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Härtig E, Loncarević IF, Büscher M, Herrlich P, Rahmsdorf HJ. A new cAMP response element in the transcribed region of the human c-fos gene. Nucleic Acids Res 1991; 19:4153-9. [PMID: 1651478 PMCID: PMC328555 DOI: 10.1093/nar/19.15.4153] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In NIH 3T3 cells the c-fos gene is induced rapidly and transiently by cAMP. As shown by the analysis of 3T3 cells stably transfected with promoter mutants of the human c-fos gene this induction does not depend on the dyad symmetry element (position -320 to -300), but involves at least two other non-related sites: an element located around position -60 resembling the cAMP response element of the fibronectin and somatostatin genes (which has been described before), and an element located between positions +18 and +38. Destruction of one or the other element in the c-fos gene reduces cAMP inducibility. The cAMP response of c-fos promoter CAT gene constructs also depends on these elements in transient transfection assays. When cloned in front of the albumin TATA box, both elements independently mediate cAMP inducibility. These elements do not bind the same protein as shown in gel retardation analyses, suggesting that two different cAMP inducible factors mediate the activation of the c-fos gene by cAMP.
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Affiliation(s)
- E Härtig
- Kernforschungszentrum Karlsruhe, Institut für Genetik und Toxikologie, FRG
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19
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Lee BA, Donoghue DJ. Membrane-anchored form of v-sis/PDGF-B induces mitogenesis without detectable PDGF receptor autophosphorylation. J Cell Biol 1991; 113:361-70. [PMID: 1849139 PMCID: PMC2288947 DOI: 10.1083/jcb.113.2.361] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The v-sis protein is structurally and functionally related to PDGF. Forms of the v-sis protein which are anchored to the cell membrane via the transmembrane domain of the vesicular stomatitis virus G protein have been previously described (Hannink, M., and D.J. Donoghue. 1986. J. Cell Biol. 103:2311-2322). Several of these fusion proteins were shown to interact productively with the PDGF receptor (PDGFR) based on their ability to transform NIH 3T3 cells. In this report, we further characterized one of these membrane-anchored v-sis proteins, designated v-sis239-G. The gene encoding v-sis239-G was placed under control of the Drosophila melanogaster hsp70 promotor and synthesis of this protein was shown to induce a mitogenic response in NIH 3T3 cells. Unexpectedly, v-sis239-G did not induce detectable autophosphorylation of the PDGFR, in contrast to a similarly expressed secreted form of the v-sis protein. Thus, it appears that a PDGFR-mediated mitogenic response may be dissociated from detectable receptor autophosphorylation. Furthermore, induced synthesis of v-sis239-G was shown to lead to c-fos expression even in the absence of detectable receptor autophosphorylation. Interestingly, a nonmitogenic membrane-anchored form of the v-sis protein, designated v-sis239-G338, also induced c-fos without receptor autophosphorylation. These results raise interesting questions regarding the roles of autophosphorylation and c-fos induction in PDGFR-mediated signal transduction and suggest the possibility of an autophosphorylation-independent signal transduction pathway.
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Affiliation(s)
- B A Lee
- Department of Chemistry, University of California, San Diego, La Jolla 92093-0322
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20
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Hannan RD, West AK. Adrenergic agents, but not triiodo-L-thyronine induce c-fos and c-myc expression in the rat heart. Basic Res Cardiol 1991; 86:154-64. [PMID: 1908674 DOI: 10.1007/bf02190548] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have examined the expression of two nuclear-acting oncogenes, c-fos and c-myc in the rat heart following administration of hormones implicated in the development of cardiac hypertrophy. A single injection of norepinephrine (2.5 micrograms/kg to 2.5 mg/kg) led to transient increases in the levels of both c-fos and c-myc mRNA. The response was sequential: elevated levels of c-fos mRNA were first observed 15 min after treatment and peaked at 1 h whilst c-myc mRNA levels increased 30 min after treatment and peaked at 2 h. The response of both cellular oncogenes to norepinephrine was reduced significantly by alpha blockade but beta blockade was less effective. Administration of triiodo-L-thyronine (0.25 mg/kg), a level known to promote cardiac hypertrophy, did not produce elevated levels of c-fos or c-myc mRNA. In an initial study, it was possible to demonstrate induction of c-fos and c-myc in rat hearts perfused in vitro with medium containing 2 x 10(-7) M norepinephrine. These results provide support for the notion that c-fos and c-myc expression may play a transducing role in the development of adrenergic-mediated, but not thyroid hormone-mediated cardiac hypertrophy.
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Affiliation(s)
- R D Hannan
- Department of Biochemistry, University of Tasmania, Australia
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21
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Induction of a chicken small heat shock (stress) protein: evidence of multilevel posttranscriptional regulation. Mol Cell Biol 1990. [PMID: 2388629 DOI: 10.1128/mcb.10.9.4886] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A novel form of regulation of expression of a vertebrate heat shock gene is described. A cDNA clone encoding human Hsp27 was shown to specifically recognize chicken Hsp23 RNA by Northern (RNA) blot analysis and hybrid-select translation. This probe was then used to measure chicken hsp23 gene activity in control and heat-stressed cells. The hsp23 gene(s) was transcriptionally active in non-heat-stressed cells, and its rate of transcription did not increase significantly upon heat shock. Cytoplasmic Hsp23 mRNA, which was metabolically very stable in nonstressed cells, underwent a fourfold increase in amount after a 1-h heat shock, resulting in a twofold increase in Hsp23 mRNA in polysomes. Hsp23 mRNA was relatively abundant and translationally active even in non-heat-shocked cells. Taken together, these data implicated posttranscriptional nuclear events as an important control point for induction of Hsp23 RNA transcripts. The protein half-life of Hsp23 increased from approximately 2 h in control cultures to 13 h in heat-shocked cells, revealing a second major control point. Hsp23 which was synthesized prior to heat shock also increased in stability and contributed to the overall accumulation of Hsp23 in heat-shocked cells. Cycloheximide had no effect on this change in Hsp23 half-life, while dactinomycin blocked the stabilization of Hsp23, suggesting a need for newly synthesized RNA. These data indicated that stabilization of Hsp23 protein and posttranscriptional nuclear events resulting in increased production of Hsp23 mRNA were primarily responsible for a 13-fold increase in the accumulation of newly synthesized Hsp23 after 1 h of heat shock. The regulation of the hsp23 gene is discussed in comparison with several other posttranscriptionally regulated genes, including the proto-oncogene c-fos, the developmentally regulated chicken delta-crystallin gene, and regulation of cellular gene expression by the proto-oncogene c-myc.
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22
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Edington BV, Hightower LE. Induction of a chicken small heat shock (stress) protein: evidence of multilevel posttranscriptional regulation. Mol Cell Biol 1990; 10:4886-98. [PMID: 2388629 PMCID: PMC361103 DOI: 10.1128/mcb.10.9.4886-4898.1990] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A novel form of regulation of expression of a vertebrate heat shock gene is described. A cDNA clone encoding human Hsp27 was shown to specifically recognize chicken Hsp23 RNA by Northern (RNA) blot analysis and hybrid-select translation. This probe was then used to measure chicken hsp23 gene activity in control and heat-stressed cells. The hsp23 gene(s) was transcriptionally active in non-heat-stressed cells, and its rate of transcription did not increase significantly upon heat shock. Cytoplasmic Hsp23 mRNA, which was metabolically very stable in nonstressed cells, underwent a fourfold increase in amount after a 1-h heat shock, resulting in a twofold increase in Hsp23 mRNA in polysomes. Hsp23 mRNA was relatively abundant and translationally active even in non-heat-shocked cells. Taken together, these data implicated posttranscriptional nuclear events as an important control point for induction of Hsp23 RNA transcripts. The protein half-life of Hsp23 increased from approximately 2 h in control cultures to 13 h in heat-shocked cells, revealing a second major control point. Hsp23 which was synthesized prior to heat shock also increased in stability and contributed to the overall accumulation of Hsp23 in heat-shocked cells. Cycloheximide had no effect on this change in Hsp23 half-life, while dactinomycin blocked the stabilization of Hsp23, suggesting a need for newly synthesized RNA. These data indicated that stabilization of Hsp23 protein and posttranscriptional nuclear events resulting in increased production of Hsp23 mRNA were primarily responsible for a 13-fold increase in the accumulation of newly synthesized Hsp23 after 1 h of heat shock. The regulation of the hsp23 gene is discussed in comparison with several other posttranscriptionally regulated genes, including the proto-oncogene c-fos, the developmentally regulated chicken delta-crystallin gene, and regulation of cellular gene expression by the proto-oncogene c-myc.
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Affiliation(s)
- B V Edington
- Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269
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23
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Sherman ML, Datta R, Hallahan DE, Weichselbaum RR, Kufe DW. Ionizing radiation regulates expression of the c-jun protooncogene. Proc Natl Acad Sci U S A 1990; 87:5663-6. [PMID: 2116003 PMCID: PMC54387 DOI: 10.1073/pnas.87.15.5663] [Citation(s) in RCA: 189] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
There is little known about the regulation of gene expression by ionizing radiation exposure. The present studies demonstrate transcriptional activation of a mammalian gene, the c-jun protooncogene, by x-rays. The c-jun gene encodes a component of the AP-1 protein complex and is important in early signaling events involved in various cellular functions. The increase in c-jun transcripts by ionizing radiation was time- and dose-dependent as determined by Northern blot analysis. Transcriptional run-on analysis demonstrated that ionizing radiation stimulates the rate of c-jun gene transcription. Furthermore, the half-life of c-jun RNA was prolonged in the absence of protein synthesis. These findings indicate that the increase in c-jun RNA observed after irradiation is regulated by transcriptional and posttranscriptional mechanisms. Moreover, the induction of c-jun by ionizing radiation was associated with an inverse dose rate effect in that decreasing the dose rate resulted in increased c-jun expression. The present results similarly demonstrate that ionizing radiation increases levels of c-fos transcripts as well as that of jun-B, another member of the jun family. Taken together, these results suggest a role for induction of early response genes in the pathophysiologic effects of ionizing radiation.
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Affiliation(s)
- M L Sherman
- Laboratory of Clinical Pharmacology, Dana-Farber Cancer Institute, Boston, MA
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24
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Petersen RB, Lindquist S. Regulation of HSP70 synthesis by messenger RNA degradation. CELL REGULATION 1989; 1:135-49. [PMID: 2519613 PMCID: PMC361432 DOI: 10.1091/mbc.1.1.135] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
When Drosophila cells are heat shocked, hsp70 messenger RNA (mRNA) is stable and is translated at high efficiencies. During recovery from heat shock, hsp70 synthesis is repressed and its messenger RNA (mRNA) is degraded in a highly regulated fashion. Dramatic differences in the timing of repression and degradation are observed after heat treatments of different severities. The 3' untranslated region (UTR) of the hsp70 mRNA was sufficient to transfer this regulated degradation to heterologous mRNAs. Altering the translational efficiency of the message or changing its natural translation-termination site did not alter its pattern of regulation, although in some cases it changed the absolute rate of degradation. We have previously shown that hsp70 mRNA is very unstable when it is expressed at normal growth temperatures (from a metallothionein promoter). We report here that the 3' untranslated region of the hsp70 mRNA is responsible for this instability as well. We postulate that a mechanism for degrading hsp70 mRNA pre-exists in Drosophila cells, that it is inactivated by heat shock and that it is the reactivation of this mechanism that is responsible for hsp70 repression during recovery. This degradation system may be the same as that used by other unstable mRNAs.
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Affiliation(s)
- R B Petersen
- Howard Hughes Medical Institute, Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637
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25
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Vance BA, Kowalski CG, Brinckerhoff CE. Heat shock of rabbit synovial fibroblasts increases expression of mRNAs for two metalloproteinases, collagenase and stromelysin. J Cell Biol 1989; 108:2037-43. [PMID: 2544599 PMCID: PMC2115583 DOI: 10.1083/jcb.108.6.2037] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Two metalloproteinases, collagenase and stromelysin, are produced in large quantities by synovial fibroblasts in individuals with rheumatoid arthritis. These enzymes play a major role in the extensive destruction of connective tissue seen in this disease. In this study, we show that heat shock of monolayer cultures of rabbit synovial fibroblasts increases expression of mRNA for heat shock protein 70 (HSP-70), and for collagenase and stromelysin. We found that after heat shock for 1 h at 45 degrees C, the mRNA expression for HSP-70 peaks at 1 h and returns to control levels by 3 h. Collagenase and stromelysin mRNA expression is coordinate, reaching peak levels at 3 h and returning to control levels by 10 h. The increase in mRNA is paralleled by an increase in the corresponding protein in the culture medium. 3 h of heat shock at a lower temperature (42 degrees C) is also effective in inducing collagenase and stromelysin mRNAs. Concomitant treatment with phorbol myristate acetate (PMA; 10(-8) or 10(-9) M) and heat shock is not additive or synergistic. In addition, all-trans-retinoic acid, added just before heat shock, prevents the increase in mRNAs for collagenase and stromelysin. Our data suggest that heat shock may be an additional mechanism whereby collagenase and stromelysin are increased during rheumatoid arthritis and perhaps in other chronic inflammatory stress conditions.
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Affiliation(s)
- B A Vance
- Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire 03756
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26
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Abstract
We examined the effect of heat shock on protein tyrosine phosphorylation in cultured animal cells using antiphosphotyrosine antibodies in immunoblotting and immunofluorescence microscopy experiments. Heat shock significantly elevated the level of phosphotyrosine in proteins in most of the cultured cells examined, including fibroblasts, epithelial cells, nerve cells, and muscle cells, but not in Rous sarcoma virus-transformed fibroblasts. The increase in protein tyrosine phosphorylation induced by heat shock occurred in proteins with a wide range of molecular masses and was dependent on the temperature and duration of the heat shock.
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Affiliation(s)
- P A Maher
- Biology Department, University of California, San Diego, La Jolla 92093
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