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Duits LA, Nibbering PH, van Strijen E, Vos JB, Mannesse-Lazeroms SPG, van Sterkenburg MAJA, Hiemstra PS. Rhinovirus increases human beta-defensin-2 and -3 mRNA expression in cultured bronchial epithelial cells. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 2003; 38:59-64. [PMID: 12900056 DOI: 10.1016/s0928-8244(03)00106-8] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human beta-defensins (hBDs) are antimicrobial peptides that play important roles in host defense against infection, inflammation and immunity. Previous studies showed that micro-organisms and proinflammatory mediators regulate the expression of these peptides in airway epithelial cells. The aim of the present study was to investigate the modulation of expression of hBDs in cultured primary bronchial epithelial cells (PBEC) by rhinovirus-16 (RV16), a respiratory virus responsible for the common cold and associated with asthma exacerbations. RV16 was found to induce expression of hBD-2 and -3 mRNA in PBEC, but did not affect hBD-1 mRNA. Viral replication appeared essential for rhinovirus-induced beta-defensin mRNA expression, since UV-inactivated rhinovirus did not increase expression of hBD-2 and hBD-3 mRNA. Exposure to synthetic double-stranded RNA (dsRNA) molecule polyinosinic:polycytidylic acid had a similar effect as RV16 on mRNA expression of these peptides in PBEC. In line with this, PBEC were found to express TLR3, a Toll-like receptor involved in recognition of dsRNA. This study shows that rhinovirus infection of PBEC leads to increased hBD-2 and hBD-3 mRNA expression, which may play a role in both the uncomplicated common cold and in virus-associated exacerbations of asthma.
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Affiliation(s)
- Louise A Duits
- Department of Infectious Diseases, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
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2
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Kim CD, Choe Y, Shim C, Kim K. Interferon Beta secreted from human hair dermal papilla cells inhibits the growth of outer root sheath cells cultured in vitro. Biochem Biophys Res Commun 2002; 290:1133-8. [PMID: 11798194 DOI: 10.1006/bbrc.2001.6324] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hair growth is tightly regulated by the epithelial-mesenchymal interaction of hair follicle cells. To investigate the molecular interaction between epithelial and mesenchymal cells of the hair follicle, the outer root sheath (ORS) cells were cultured with the dermal papilla (DP)-conditioned medium. Using the techniques of differential display reverse transcription-polymerase chain reaction (DD RT-PCR) and Northern blot analysis, we identified that an interferon-inducible gene 6-16 is regulated in the ORS cells when cultured with the DP-conditioned medium. We further studied the effect of the DP-conditioned medium and found that interferon beta, a predominant interferon secreted by the fibroblasts, is expressed by the DP cells. Moreover, the anti-interferon beta neutralized DP-conditioned medium dramatically inhibited the 6-16 mRNA expression. Interferon beta or DP-conditioned medium suppressed the growth of the in vitro cultured ORS cells, suggesting that interferon beta secreted from the DP cells negatively regulates the growth of ORS cells. Together these results reveal the potential importance of the interferon beta as a negative regulator of hair growth.
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Affiliation(s)
- Chang Deok Kim
- School of Biological Sciences, Seoul National University, Seoul, 151-742, Korea
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3
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Dodd DA, Giddings TH, Kirkegaard K. Poliovirus 3A protein limits interleukin-6 (IL-6), IL-8, and beta interferon secretion during viral infection. J Virol 2001; 75:8158-65. [PMID: 11483761 PMCID: PMC115060 DOI: 10.1128/jvi.75.17.8158-8165.2001] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
During viral infections, the host secretory pathway is crucial for both innate and acquired immune responses. For example, the export of most proinflammatory and antiviral cytokines, which recruit lymphocytes and initiate antiviral defenses, requires traffic through the host secretory pathway. To investigate potential effects of the known inhibition of cellular protein secretion during poliovirus infection on pathogenesis, cytokine secretion from cells infected with wild-type virus and with 3A-2, a mutant virus carrying an insertion in viral protein 3A which renders the virus defective in the inhibition of protein secretion, was tested. We show here that cells infected with 3A-2 mutant virus secrete greater amounts of cytokines interleukin-6 (IL-6), IL-8, and beta interferon than cells infected with wild-type poliovirus. Increased cytokine secretion from the mutant-infected cells can be attributed to the reduced inhibition of host protein secretion, because no significant differences between 3A-2- and wild-type-infected cells were observed in the inhibition of viral growth, host cell translation, or the ability of wild-type- or 3A-2-infected cells to support the transcriptional induction of beta interferon mRNA. We surmise that the wild-type function of 3A in inhibiting ER-to-Golgi traffic is not required for viral replication in tissue culture but, by altering the amount of secreted cytokines, could have substantial effects on pathogenesis within an infected host. The global inhibition of protein secretion by poliovirus may reflect a general mechanism by which pathogens that do not require a functional protein secretory apparatus can reduce the native immune response and inflammation associated with infection.
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Affiliation(s)
- D A Dodd
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94309, USA
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4
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Kumar M, Carmichael GG. Antisense RNA: function and fate of duplex RNA in cells of higher eukaryotes. Microbiol Mol Biol Rev 1998; 62:1415-34. [PMID: 9841677 PMCID: PMC98951 DOI: 10.1128/mmbr.62.4.1415-1434.1998] [Citation(s) in RCA: 222] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
There is ample evidence that cells of higher eukaryotes express double-stranded RNA molecules (dsRNAs) either naturally or as the result of viral infection or aberrant, bidirectional transcriptional readthrough. These duplex molecules can exist in either the cytoplasmic or nuclear compartments. Cells have evolved distinct ways of responding to dsRNAs, depending on the nature and location of the duplexes. Since dsRNA molecules are not thought to exist naturally within the cytoplasm, dsRNA in this compartment is most often associated with viral infections. Cells have evolved defensive strategies against such molecules, primarily involving the interferon response pathway. Nuclear dsRNA, however, does not induce interferons and may play an important posttranscriptional regulatory role. Nuclear dsRNA appears to be the substrate for enzymes which deaminate adenosine residues to inosine residues within the polynucleotide structure, resulting in partial or full unwinding. Extensively modified RNAs are either rapidly degraded or retained within the nucleus, whereas transcripts with few modifications may be transported to the cytoplasm, where they serve to produce altered proteins. This review summarizes our current knowledge about the function and fate of dsRNA in cells of higher eukaryotes and its potential manipulation as a research and therapeutic tool.
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Affiliation(s)
- M Kumar
- Department of Microbiology, University of Connecticut Health Center, Farmington, Connecticut 06030-3205, USA.
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5
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Kondo H, Yonezawa Y, Ito H. Interferon-beta, an autocrine cytokine, suppresses human fetal skin fibroblast migration into a denuded area in a cell monolayer but is not involved in the age-related decline of cell migration. Mech Ageing Dev 1996; 87:141-53. [PMID: 8794443 DOI: 10.1016/0047-6374(95)01699-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The migration of human skin fibroblasts into a denuded area in a cell monolayer declined during in vitro and in vivo aging. We carried out a study to determine whether this age-related decline in cell migration was mediated by the autocrine cytokine interferon-beta (IFN-beta), which has been reported to suppress the proliferation, chemotaxis and collagen synthesis of human fibroblasts. Actually, IFN-beta specifically suppressed the migration of TIG-3S human fetal skin fibroblasts into a denuded area in a cell monolayer, as shown by the dose response experiments of IFN-beta and neutralizing anti-IFN-beta antibody. IFN-beta also inhibited their collagen synthesis but the addition of type I collagen could not reverse IFN-beta-induced inhibition of cell migration. Double strand RNA, which has been generally known to induce IFN-beta in human skin fibroblasts, suppressed the migration of TIG-3S cells. Next, a study was done to determine whether IFN-beta and double strand RNA suppressed the migration of TIG-3S cells in late passages as well as early passages, or whether neutralizing anti-IFN-beta antibody stimulated the migration of TIG-3S cells in late and middle passages. IFN-beta and double strand RNA suppressed the migration of TIG-3S cells in middle (PD45) and late (PD55) passages as well as in early passages (PD23-28). Neutralizing anti-IFN-beta antibodies could not reverse the low migratory activity of middle and late passage cells to the high migratory activity of early passage cells. These results indicated that the autocrine cytokine IFN-beta did not seem to be involved in the age-dependent decline of fibroblast migration.
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Affiliation(s)
- H Kondo
- Department of Experimental Biology, Tokyo Metropolitan Institute of Gerontology, Japan
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6
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Roger PP, Reuse S, Maenhaut C, Dumont JE. Multiple facets of the modulation of growth by cAMP. VITAMINS AND HORMONES 1995; 51:59-191. [PMID: 7483330 DOI: 10.1016/s0083-6729(08)61038-9] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- P P Roger
- Institute of Interdisciplinary Research, Free University of Brussels, Belgium
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7
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Goodman L, Stein G. Basal and induced amounts of interleukin-6 mRNA decline progressively with age in human fibroblasts. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32160-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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8
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Garfinkel S, Haines D, Brown S, Wessendorf J, Gillespie D, Maciag T. Interleukin-1 alpha mediates an alternative pathway for the antiproliferative action of poly(I.C) on human endothelial cells. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)35776-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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9
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Perricone MA, Giri SN, Hyde DM. Double-stranded RNA regulation of DNA synthesis in fibroblasts. Exp Cell Res 1992; 198:101-6. [PMID: 1727043 DOI: 10.1016/0014-4827(92)90154-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The double-stranded RNA molecule polyinosinic-polycytidylic acid (poly IC) has been found in some studies to have a mitogenic effect on fibroblast proliferation while other studies found poly IC to have an inhibitory effect on proliferation. In this study, we investigated whether a stabilized form of poly IC complexed with poly-L-lysine and carboxymethylcellulose (poly ICLC) had a bidirectional effect on DNA synthesis in fibroblasts from four different cell lines and determined factors that potentially influence this bidirectional effect. In medium containing fetal bovine serum, poly ICLC slightly increased the levels of [3H]thymidine incorporation in growing fibroblasts in three of the four fibroblast cell lines tested, while poly ICLC increased [3H]thymidine incorporation in confluent, quiescent fibroblasts in two of four cell lines. Poly ICLC did not induce DNA synthesis in subconfluent, quiescent or in confluent, quiescent fibroblasts under serum-free conditions. Poly ICLC significantly suppressed serum-induced [3H]thymidine incorporation by quiescent fibroblasts in all cell lines. We conclude that the stimulatory and inhibitory effects of poly ICLC on DNA synthesis are influenced by both the cell line and the presence of serum components in the culture medium but not by population density.
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Affiliation(s)
- M A Perricone
- Department of Anatomy, School of Veterinary Medicine, University of California, Davis 95616
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10
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BALB/c-3T3 fibroblasts resistant to growth inhibition by beta interferon exhibit aberrant platelet-derived growth factor, epidermal growth factor, and fibroblast growth factor signal transduction. Mol Cell Biol 1991. [PMID: 1645446 DOI: 10.1128/mcb.11.6.3148] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several lines of evidence now exist to suggest an interaction between the platelet-derived growth factor (PDGF) growth-stimulatory signal transduction pathway and the beta interferon (IFN-beta) growth-inhibitory signal transduction pathway. The most direct examples are inhibition of PDGF-mediated gene induction and mitogenesis by IFN-beta and the effects of activators and inhibitors of the IFN-inducible double-stranded RNA-dependent eIF2 kinase on expression of PDGF-inducible genes. To further investigate the nature of this PDGF/IFN-beta interaction, we selected BALB/c-3T3 cells for resistance to growth inhibition by IFN-beta and analyzed the phenotypes of resulting clonal lines (called IRB cells) with respect to PDGF signal transduction. Although selected only for IFN resistance, the IRB cells were found to be defective for induction of growth-related genes c-fos, c-myc and JE in response to PDGF. This block to signal transduction was not due to loss or inactivation of PDGF receptors, as immunoprecipitation of PDGF receptors with antiphosphotyrosine antibodies showed them to be present at equal levels in the BALB/c-3T3 and IRB cells and to be autophosphorylated normally in response to PDGF. Furthermore, treatment with other peptide growth factors (PDGF-AA, fibroblast growth factor, and epidermal growth factor) also failed to induce c-fos, c-myc, or JE expression in IRB cells. All of these growth factors, however, were able to induce another early growth-related gene, Egr-1. The block to signaling was not due to a defect in inositol phosphate metabolism, as PDGF treatment induced normal calcium mobilization and phosphotidylinositol-3-kinase activation in these cells. Activation of protein kinase C by phorbol esters did induce c-fos, c-myc, and JE in IRB cells, indicating that signalling pathways distal to this enzyme remained intact. We have previously shown that IFN-inducible enzyme activities, including double-stranded RNA-dependent eIF2 kinase and 2',5'-oligoadenylate synthetase, are normal in IRB cells. The finding that the induction of multiple growth-related genes by several independent growth factors is inhibited in these IFN-resistant cells suggests that there is a second messenger common to both growth factor and IFN signaling pathways and that this messenger is defective in these cells.
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11
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Mundschau LJ, Faller DV. BALB/c-3T3 fibroblasts resistant to growth inhibition by beta interferon exhibit aberrant platelet-derived growth factor, epidermal growth factor, and fibroblast growth factor signal transduction. Mol Cell Biol 1991; 11:3148-54. [PMID: 1645446 PMCID: PMC360164 DOI: 10.1128/mcb.11.6.3148-3154.1991] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Several lines of evidence now exist to suggest an interaction between the platelet-derived growth factor (PDGF) growth-stimulatory signal transduction pathway and the beta interferon (IFN-beta) growth-inhibitory signal transduction pathway. The most direct examples are inhibition of PDGF-mediated gene induction and mitogenesis by IFN-beta and the effects of activators and inhibitors of the IFN-inducible double-stranded RNA-dependent eIF2 kinase on expression of PDGF-inducible genes. To further investigate the nature of this PDGF/IFN-beta interaction, we selected BALB/c-3T3 cells for resistance to growth inhibition by IFN-beta and analyzed the phenotypes of resulting clonal lines (called IRB cells) with respect to PDGF signal transduction. Although selected only for IFN resistance, the IRB cells were found to be defective for induction of growth-related genes c-fos, c-myc and JE in response to PDGF. This block to signal transduction was not due to loss or inactivation of PDGF receptors, as immunoprecipitation of PDGF receptors with antiphosphotyrosine antibodies showed them to be present at equal levels in the BALB/c-3T3 and IRB cells and to be autophosphorylated normally in response to PDGF. Furthermore, treatment with other peptide growth factors (PDGF-AA, fibroblast growth factor, and epidermal growth factor) also failed to induce c-fos, c-myc, or JE expression in IRB cells. All of these growth factors, however, were able to induce another early growth-related gene, Egr-1. The block to signaling was not due to a defect in inositol phosphate metabolism, as PDGF treatment induced normal calcium mobilization and phosphotidylinositol-3-kinase activation in these cells. Activation of protein kinase C by phorbol esters did induce c-fos, c-myc, and JE in IRB cells, indicating that signalling pathways distal to this enzyme remained intact. We have previously shown that IFN-inducible enzyme activities, including double-stranded RNA-dependent eIF2 kinase and 2',5'-oligoadenylate synthetase, are normal in IRB cells. The finding that the induction of multiple growth-related genes by several independent growth factors is inhibited in these IFN-resistant cells suggests that there is a second messenger common to both growth factor and IFN signaling pathways and that this messenger is defective in these cells.
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Affiliation(s)
- L J Mundschau
- Division of Pediatric Hematology and Oncology, Dana Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115
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12
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Abstract
The study of double-stranded RNA (dsRNA) encompasses a variety of fields. Basic research in this area has contributed to a greater mechanistic understanding of gene induction, tumor cell growth arrest, the establishment of antiviral states, and immunomodulation. Because of the possible clinical value of these molecules, physicians are now exploring the use of synthetic dsRNA to treat patients with cancer, HIV-1 disease, and immune dysfunction. Continued studies of the mechanisms of action of dsRNA are likely to suggest an even wider scope of clinical applications.
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Affiliation(s)
- D S Haines
- Department of Neoplastic Diseases, Hahnemann University, Philadelphia, Pennsylvania 19102
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13
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Böhmer RM, Forsberg K, Westermark B. Growth inhibition of mitogen-stimulated fibroblasts induced by double-stranded RNA depends on cell density. Exp Cell Res 1990; 191:115-20. [PMID: 2226642 DOI: 10.1016/0014-4827(90)90043-a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Polyinosinic-polycytidylic acid [poly(I:C)], a synthetic double-stranded RNA, is an inhibitor of mitogen-induced proliferation of normal fibroblasts. We show that this inhibition depends strongly on cell density. While cultures with densities at or above confluence are completely inhibited by poly(I:C) in their proliferative response to epidermal growth factor (EGF), the proliferation of sparse (subconfluent) cultures is only delayed. Conditioned medium from dense fibroblasts exposed to poly(I:C) inhibits EGF stimulation of sparse cells, indicating that the inhibition is, at least in part, mediated by a factor released from the cells. Preincubation of quiescent cultures with poly(I:C) renders the cells refractory to the inhibitory effects of poly(I:C). This desensitization correlates with a decreased production of the inhibitor. Since the inhibition of mitogenic stimulation by poly(I:C) is completely overcome by antisera recognizing interferon-beta (IFN-beta) and interleukin-6 (IL-6), we tested the effect of IL-6 and IFN-beta on EGF mitogenicity. None of the available IL-6 preparations had any effect on cell cycle entry. IFN-beta caused a dose-dependent delay of cell division but did not affect the density-dependent proportion of cells entering the cell cycle in response to EGF. Thus, IFN-beta cannot be the sole mediator of the poly(I:C)-induced inhibition. In the presence of dexamethasone, poly(I:C) did not inhibit EGF mitogenis. Indeed, the combined presence of poly(I:C) and dexamethasone did more than just restore the density-dependent control levels of EGF stimulation; most cells entered the cell cycle even at extremely high cell densities. Thus, poly(I:C) in combination with dexamethasone could deactivate the cell density-dependent negative control of proliferation.
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Affiliation(s)
- R M Böhmer
- Melbourne Tumor Biology Branch, Ludwig Institute for Cancer Research, Victoria, Australia
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14
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Induction of c-Ha-ras gene expression by double-stranded RNA and interferon requirement. Mol Cell Biol 1990. [PMID: 2196455 DOI: 10.1128/mcb.10.8.4424] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The addition of double-stranded RNA (dsRNA) to NIH 3T3 cells led to an increase in the RNA levels of c-Ha-ras. The double-stranded configuration was required for the increase in c-Ha-ras mRNA levels, as heat-denatured dsRNA and single-stranded RNA did not have any effect. Nuclear run-on transcription experiments indicated that the increase in c-Ha-ras mRNA levels stimulated by dsRNA was due to transcriptional activation of the gene. The induction of c-Ha-ras gene expression by dsRNA was inhibited by anti-beta interferon antibodies, suggesting that interferon might mediate the induction.
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15
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Maran A, Goldberg ID, Steinberg BM. Induction of c-Ha-ras gene expression by double-stranded RNA and interferon requirement. Mol Cell Biol 1990; 10:4424-6. [PMID: 2196455 PMCID: PMC361008 DOI: 10.1128/mcb.10.8.4424-4426.1990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The addition of double-stranded RNA (dsRNA) to NIH 3T3 cells led to an increase in the RNA levels of c-Ha-ras. The double-stranded configuration was required for the increase in c-Ha-ras mRNA levels, as heat-denatured dsRNA and single-stranded RNA did not have any effect. Nuclear run-on transcription experiments indicated that the increase in c-Ha-ras mRNA levels stimulated by dsRNA was due to transcriptional activation of the gene. The induction of c-Ha-ras gene expression by dsRNA was inhibited by anti-beta interferon antibodies, suggesting that interferon might mediate the induction.
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Affiliation(s)
- A Maran
- Long Island Jewish Medical Center, New Hyde Park, New York 11042
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16
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LOHI JOUKO, PERTOVAARA LIISA, SISTONEN LEA, ALITALO KARI, KESKI-OJA JORMA. Regulation by TGF? of Genes Involved in Growth Control: Interleukin-6. Ann N Y Acad Sci 1990. [DOI: 10.1111/j.1749-6632.1990.tb16130.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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17
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Heldin NE, Paulsson Y, Forsberg K, Heldin CH, Westermark B. Induction of cyclic AMP synthesis by forskolin is followed by a reduction in the expression of c-myc messenger RNA and inhibition of 3H-thymidine incorporation in human fibroblasts. J Cell Physiol 1989; 138:17-23. [PMID: 2536035 DOI: 10.1002/jcp.1041380104] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have studied the effect of increased intracellular levels of cyclic AMP on the growth response to platelet-derived growth factor (PDGF) of human foreskin fibroblasts in culture. It was found that forskolin, a potent stimulator of adenylate cyclase activity, inhibits the stimulatory effect of PDGF on 3H-thymidine incorporation with a dose dependence similar to that observed with regard to cyclic AMP formation. A time-course study indicated that forskolin has no effect on ongoing DNA synthesis but affects events in the prereplicative phase. The cell-cycle block induced by forskolin was found to be reversible; after removal of the drug, DNA synthesis was initiated after a lag period, similar to that of the prereplicative phase of control cells. Forskolin had no effect on PDGF binding, receptor autophosphorylation, or c-fos mRNA expression. However, a reduction in PDGF-induced c-myc mRNA expression was observed in cultures given forskolin. Forskolin was also found to have a marked stimulatory effect on the expression of interferon-beta 2 mRNA expression. However, we were unable to demonstrate that the growth-inhibitory effect of forskolin is mediated by interferon-beta. In conclusion, an increase in cAMP levels leads to a reversible inhibition of PDGF-induced DNA synthesis in human fibroblasts, which may be related to an inhibition of c-myc mRNA expression.
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Affiliation(s)
- N E Heldin
- Department of Pathology, University Hospital, Uppsala, Sweden
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