scholarly journals RNase L Antiviral Activity Is Not a Critical Component of the Oas1b-Mediated Flavivirus Resistance Phenotype

2019 ◽  
Vol 93 (22) ◽  
Author(s):  
J. C. Madden ◽  
Dan Cui ◽  
M. A. Brinton
Keyword(s):  
Antiviral Activity ◽  
Full Length ◽  
Viral Rna ◽  
Type I ◽  
Mrna Levels ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Resistant Mouse ◽  
Resistance Phenotype

ABSTRACT In mice, resistance to central nervous system (CNS) disease induced by members of the genus Flavivirus is conferred by an allele of the 2′-5′ oligoadenylate synthetase 1b gene that encodes the inactive full-length protein (Oas1b-FL). The susceptibility allele encodes a C-terminally truncated protein (Oas1b-tr). We show that the efficiency of neuron infection in the brains of resistant and susceptible mice is similar after an intracranial inoculation of two flaviviruses, but amplification of viral proteins and double-stranded RNA (dsRNA) is inhibited in infected neurons in resistant mouse brains at later times. Active OAS proteins detect cytoplasmic dsRNA and synthesize short 2′-5′-linked oligoadenylates (2′-5′A) that interact with the latent endonuclease RNase L, causing it to dimerize and cleave single-stranded RNAs. To evaluate the contribution of RNase L to the resistance phenotype in vivo, we created a line of resistant RNase L−/− mice. Evidence of RNase L activation in infected RNase L+/+ mice was indicated by higher levels of viral RNA in the brains of infected RNase L−/− mice. Activation of type I interferon (IFN) signaling was detected in both resistant and susceptible brains, but Oas1a and Oas1b mRNA levels were lower in RNase L+/+ mice of both types, suggesting that activated RNase L also has a proflaviviral effect. Inhibition of virus replication was robust in resistant RNase L−/− mice, indicating that activated RNase L is not a critical factor in mediating this phenotype. IMPORTANCE The mouse genome encodes a family of Oas proteins that synthesize 2′-5′A in response to dsRNA. 2′-5′A activates the endonuclease RNase L to cleave single-stranded viral and cellular RNAs. The inactive, full-length Oas1b protein confers flavivirus-specific disease resistance. Although similar numbers of neurons were infected in resistant and susceptible brains after an intracranial virus infection, viral components amplified only in susceptible brains at later times. A line of resistant RNase L−/− mice was used to evaluate the contribution of RNase L to the resistance phenotype in vivo. Activation of RNase L antiviral activity by flavivirus infection was indicated by increased viral RNA levels in the brains of RNase L−/− mice. Oas1a and Oas1b mRNA levels were higher in infected RNase L−/− mice, indicating that activated RNase L also have a proflaviviral affect. However, the resistance phenotype was equally robust in RNase L−/− and RNase L+/+ mice.

scholarly journals Zika Virus Production Is Resistant to RNase L Antiviral Activity

2019 ◽  
Vol 93 (16) ◽  
Author(s):  
Jillian N. Whelan ◽  
Yize Li ◽  
Robert H. Silverman ◽  
Susan R. Weiss
Keyword(s):  
Antiviral Activity ◽  
Zika Virus ◽  
Viral Genome ◽  
Molecular Mechanisms ◽  
Virus Production ◽  
Type I ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Zikv Infection ◽  
Initial Report

SUMMARYThere is currently no knowledge of how the emerging human pathogen Zika virus (ZIKV) interacts with the antiviral endoribonuclease L (RNase L) pathway during infection. Since activation of RNase L during infection typically limits virus production dramatically, we used CRISPR-Cas9 gene editing technology to knockout (KO) targeted host genes involved in the RNase L pathway to evaluate the effects of RNase L on ZIKV infection in human A549 cells. RNase L was activated in response to ZIKV infection, which degraded ZIKV genomic RNA. Surprisingly, despite viral genome reduction, RNase L activity did not reduce ZIKV infectious titers. In contrast, both the flavivirus dengue virus and the alphavirus Sindbis virus replicated to significantly higher titers in RNase L KO cells compared to wild-type (WT) cells. Using MAVS/RNase L double KO cells, we demonstrated that the absence of increased ZIKV production in RNase L KO cells was not due to compensation by enhanced type I interferon transcripts to thus inhibit virus production. Finally, when synthetic double-stranded RNA was detected by OAS3 to induce RNase L antiviral activity prior to ZIKV infection, we observed reduced ZIKV replication factory formation, as well as a 42-fold reduction in virus yield in WT but not RNase L KO cells. This study proposes that ZIKV evades RNase L antiviral activity by generating a viral genome reservoir protected from RNase L cleavage during early infection, allowing for sufficient virus production before RNase L activation is detectable.IMPORTANCEWith the onset of the 2015 ZIKV outbreak, ZIKV pathogenesis has been of extreme global public health interest, and a better understanding of interactions with the host would provide insight into molecular mechanisms driving the severe neurological outcomes of ZIKV disease. Here is the initial report on the relationship between ZIKV and the host oligoadenylate synthetase-RNase L (OAS-RNase L) system, a potent antiviral pathway effective at restricting replication of diverse viruses. Our study elucidated a unique mechanism whereby ZIKV production is impervious to antiviral RNase L activity, through a mechanism of viral RNA protection that is not mimicked during infection with numerous other RNase L-activating viruses, thus identifying a distinct replication strategy potentially important for ZIKV pathogenesis.

scholarly journals Extracellular 2′-5′ Oligoadenylate Synthetase Stimulates RNase L-Independent Antiviral Activity: a Novel Mechanism of Virus-Induced Innate Immunity

2010 ◽  
Vol 84 (22) ◽  
pp. 11898-11904 ◽  
Author(s):  
Helle Kristiansen ◽  
Christina A. Scherer ◽  
Maralee McVean ◽  
Shawn P. Iadonato ◽  
Susanne Vends ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Antiviral Agent ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Antiviral Compound ◽  
Clinical Prognosis ◽  
Strong Antiviral Activity ◽  
Infected Cells

ABSTRACT The 2′-5′ oligoadenylate synthetase (OAS) proteins are traditionally considered intracellular antiviral proteins. However, several studies demonstrate a correlation between the concentration of freely circulating OAS protein in sera from hepatitis C patients and their clinical prognosis. Here we demonstrate that extracellular OAS1 enters into cells and possesses a strong antiviral activity, both in vitro and in vivo, which is independent of RNase L. The OAS protein directly inhibits viral proliferation and does not require the activation of known antiviral signaling pathways. We propose that OAS produced by cells infected with viruses is released to the extracellular space, where it acts as a paracrine antiviral agent. Thus, the OAS protein represents the first direct antiviral compound released by virus-infected cells.

scholarly journals Murine AKAP7 Has a 2′,5′-Phosphodiesterase Domain That Can Complement an Inactive Murine Coronavirus ns2 Gene

mBio ◽  
2014 ◽  
Vol 5 (4) ◽  
Author(s):  
Elona Gusho ◽  
Rong Zhang ◽  
Babal K. Jha ◽  
Joshua M. Thornbrough ◽  
Beihua Dong ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Rna Viruses ◽  
Hepatitis Virus ◽  
Cellular Protein ◽  
Full Length ◽  
Type I ◽  
Rnase L ◽  
Regulatory Subunits ◽  
Host Interactions ◽  
Murine Coronavirus

ABSTRACTViral 2′,5′-phosphodiesterases (2′,5′-PDEs) help disparate RNA viruses evade the antiviral activity of interferon (IFN) by degrading 2′,5′-oligoadenylate (2-5A) activators of RNase L. A kinase anchoring proteins (AKAPs) bind the regulatory subunits of protein kinase A (PKA) to localize and organize cyclic AMP (cAMP) signaling during diverse physiological processes. Among more than 43 AKAP isoforms, AKAP7 appears to be unique in its homology to viral 2′,5′-PDEs. Here we show that mouse AKAP7 rapidly degrades 2-5A with kinetics similar to that of murine coronavirus (mouse hepatitis virus [MHV]) strain A59 ns2 and human rotavirus strain WA VP3 proteins. To determine whether AKAP7 could substitute for a viral 2′,5′-PDE, we inserted AKAP7 cDNA into an MHV genome with an inactivated ns2 gene. The AKAP7 PDE domain or N-terminally truncated AKAP7 (both lacking a nuclear localization motif), but not full-length AKAP7 or a mutant, AKAP7H185R, PDE domain restored the infectivity of ns2 mutant MHV in bone marrow macrophages and in livers of infected mice. Interestingly, the AKAP7 PDE domain and N-terminally deleted AKAP7 were present in the cytoplasm (the site of MHV replication), whereas full-length AKAP7 was observed only in nuclei. We suggest the possibility that viral acquisition of the host AKAP7 PDE domain might have occurred during evolution, allowing diverse RNA viruses to antagonize the RNase L pathway.IMPORTANCEEarly virus-host interactions determine whether an infection is established, highlighting the need to understand fundamental mechanisms regulating viral pathogenesis. Recently, our laboratories reported a novel mode of regulation of the IFN antiviral response. We showed that the coronavirus MHV accessory protein ns2 antagonizes the type I IFN response, promoting viral replication and hepatitis. ns2 confers virulence by cleaving 2′,5′-oligoadenylate (2-5A) activators of RNase L in macrophages. We also reported that the rotavirus VP3 C-terminal domain (VP3-CTD) cleaves 2-5A and that it may rescue ns2 mutant MHV. Here we report that a cellular protein, AKAP7, has an analogous 2′,5′-phosphodiesterase (2′,5′-PDE) domain that is able to restore the growth of chimeric MHV expressing inactive ns2. The proviral effect requires cytoplasmic localization of the AKAP7 PDE domain. We speculate that AKAP7 is the ancestral precursor of viral proteins, such as ns2 and VP3, that degrade 2-5A to evade the antiviral activity of RNase L.

scholarly journals Activation of RNase L by Murine Coronavirus in Myeloid Cells Is Dependent on BasalOasGene Expression and Independent of Virus-Induced Interferon

2016 ◽  
Vol 90 (6) ◽  
pp. 3160-3172 ◽  
Author(s):  
L. Dillon Birdwell ◽  
Zachary B. Zalinger ◽  
Yize Li ◽  
Patrick W. Wright ◽  
Ruth Elliott ◽  
...  
Keyword(s):  
Gene Expression ◽  
Antiviral Activity ◽  
Hepatitis Virus ◽  
Mouse Hepatitis Virus ◽  
Myeloid Cells ◽  
Type I ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Double Stranded Rna ◽  
Murine Coronavirus

ABSTRACTThe oligoadenylate synthetase (OAS)-RNase L pathway is a potent interferon (IFN)-induced antiviral activity. Upon sensing double-stranded RNA, OAS produces 2′,5′-oligoadenylates (2-5A), which activate RNase L. Murine coronavirus (mouse hepatitis virus [MHV]) nonstructural protein 2 (ns2) is a 2′,5′-phosphodiesterase (PDE) that cleaves 2-5A, thereby antagonizing RNase L activation. PDE activity is required for robust replication in myeloid cells, as a mutant of MHV (ns2H126R) encoding an inactive PDE fails to antagonize RNase L activation and replicates poorly in bone marrow-derived macrophages (BMM), while ns2H126Rreplicates to high titer in several types of nonmyeloid cells, as well as in IFN receptor-deficient (Ifnar1−/−) BMM. We reported previously that myeloid cells express significantly higher basal levels of OAS transcripts than nonmyeloid cells. Here, we investigated the contributions ofOasgene expression, basal IFN signaling, and virus-induced IFN to RNase L activation. Infection with ns2H126Ractivated RNase L inIfih1−/−BMM to a similar extent as in wild-type (WT) BMM, despite the lack of IFN induction in the absence of MDA5 expression. However, ns2H126Rfailed to induce RNase L activation in BMM treated with IFNAR1-blocking antibody, as well as inIfnar1−/−BMM, both expressing low basal levels ofOasgenes. Thus, activation of RNase L does not require virus-induced IFN but rather correlates with adequate levels of basalOasgene expression, maintained by basal IFN signaling. Finally, overexpression of RNase L is not sufficient to compensate for inadequate basal OAS levels.IMPORTANCEThe oligoadenylate synthetase (OAS)-RNase L pathway is a potent antiviral activity. Activation of RNase L during murine coronavirus (mouse hepatitis virus [MHV]) infection of myeloid cells correlates with high basalOasgene expression and is independent of virus-induced interferon secretion. Thus, our data suggest that cells with high basalOasgene expression levels can activate RNase L and thereby inhibit virus replication early in infection upon exposure to viral double-stranded RNA (dsRNA) before the induction of interferon and prior to transcription of interferon-stimulated antiviral genes. These findings challenge the notion that activation of the OAS-RNase L pathway requires virus to induce type I IFN, which in turn upregulates OAS gene expression, as well as to provide dsRNA to activate OAS. Our data further suggest that myeloid cells may serve as sentinels to restrict viral replication, thus protecting other cell types from infection.

scholarly journals Heterozygous OAS1 gain-of-function variants cause an autoinflammatory immunodeficiency

2021 ◽  
Vol 6 (60) ◽  
pp. eabf9564
Author(s):  
Thomas Magg ◽  
Tsubasa Okano ◽  
Lars M. Koenig ◽  
Daniel F.R. Boehmer ◽  
Samantha L. Schwartz ◽  
...  
Keyword(s):  
B Cells ◽  
Hematopoietic Cell Transplantation ◽  
De Novo ◽  
Dynamics Simulation ◽  
Recurrent Fever ◽  
Type I ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Gain Of Function ◽  
Translational Arrest

Analysis of autoinflammatory and immunodeficiency disorders elucidates human immunity and fosters the development of targeted therapies. Oligoadenylate synthetase 1 is a type I interferon–induced, intracellular double-stranded RNA (dsRNA) sensor that generates 2′-5′-oligoadenylate to activate ribonuclease L (RNase L) as a means of antiviral defense. We identified four de novo heterozygous OAS1 gain-of-function variants in six patients with a polymorphic autoinflammatory immunodeficiency characterized by recurrent fever, dermatitis, inflammatory bowel disease, pulmonary alveolar proteinosis, and hypogammaglobulinemia. To establish causality, we applied genetic, molecular dynamics simulation, biochemical, and cellular functional analyses in heterologous, autologous, and inducible pluripotent stem cell–derived macrophages and/or monocytes and B cells. We found that upon interferon-induced expression, OAS1 variant proteins displayed dsRNA-independent activity, which resulted in RNase L–mediated RNA cleavage, transcriptomic alteration, translational arrest, and dysfunction and apoptosis of monocytes, macrophages, and B cells. RNase L inhibition with curcumin modulated and allogeneic hematopoietic cell transplantation cured the disorder. Together, these data suggest that human OAS1 is a regulator of interferon-induced hyperinflammatory monocyte, macrophage, and B cell pathophysiology.

Establishment of Full-length cDNA Clones and an Efficient Oral Infection Model for Feline Coronavirus in Cats

2021 ◽  
Author(s):  
Gang Wang ◽  
Guangli Hu ◽  
Rui Liang ◽  
Jiale Shi ◽  
Xiuxiu Qiu ◽  
...  
Keyword(s):  
Neutralizing Antibodies ◽  
Full Length ◽  
Infection Model ◽  
Type I ◽  
Feline Infectious Peritonitis ◽  
Spike Gene ◽  
Full Length Cdna ◽  
Adult Cats

Feline infectious peritonitis virus (FIPV) is the etiologic agent of feline infectious peritonitis (FIP) and causes fatal disease in cats of almost all ages. Currently, there are no clinically approved drugs or effective vaccines for FIP. Furthermore, the pathogenesis of FIP is still not fully understood. There is an urgent need for an effective infection model of feline infectious peritonitis induced by FIPV. Here, we constructed a field type I FIPV full-length cDNA clone, pBAC-QS, corresponding to the isolated FIPV QS. By replacing the FIPV QS spike gene with the commercially available type II FIPV 79-1146 (79-1146_CA) spike gene, we established and rescued a recombinant virus, designated rQS-79. Moreover, we constructed 79-1146_CA infectious full-length cDNA pBAC-79-1146_CA, corresponding to recombinant FCoV 79-1146_CA (r79-1146_CA). In animal experiments with one- to two-year-old adult cats orally infected with the recombinant virus, rQS-79 induced typical FIP signs and 100% mortality. In contrast to cats infected with rQS-79, cats infected with 79-1146_CA did not show obvious signs. Furthermore, by rechallenging rQS-79 in surviving cats previously infected with 79-1146_CA, we found that there was no protection against rQS-79 with different titers of neutralizing antibodies. However, high titers of neutralizing antibodies may help prolong the cat survival time. Overall, we report the first reverse genetics of virulent recombinant FCoV (causing 100% mortality in adult cats) and attenuated FCoV (causing no mortality in adult cats), which will be powerful tools to study the pathogenesis, antiviral drugs and vaccines for FCoV. Importance Tissue- or cell culture-adapted feline infectious peritonitis virus (FIPV) usually loses pathogenicity. To develop a highly virulent FIPV, we constructed a field isolate type I FIPV full-length clone with the spike gene replaced by the 79-1146 spike gene, corresponding to a virus named rQS-79, which induces high mortality in adult cats. rQS-79 represents the first described reverse genetics system for highly pathogenic FCoV. By further constructing the cell culture-adapted FCoV 79-1146_CA, we obtained infectious clones of virulent and attenuated FCoV. By in vitro and in vivo experiments, we established a model that can serve to study the pathogenic mechanisms of FIPV. Importantly, the wild-type FIPV replicase skeleton of serotype I will greatly facilitate the screening of antiviral drugs, both in vivo and in vitro.

scholarly journals Activation and Antagonism of the OAS–RNase L Pathway

Proceedings ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 14
Author(s):  
Susan R. Weiss
Keyword(s):  
Cell Death ◽  
Antiviral Activity ◽  
Apoptotic Cell ◽  
Early Response ◽  
Apoptotic Cell Death ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Viral Genomes ◽  
L System ◽  
Infected Cells

The oligoadenylate synthetase–ribonuclease L (OAS–RNase L) system is a potent antiviral pathway that severely limits the pathogenesis of many viruses. Upon sensing dsRNA, OASs produce 2′,5′-oligoadenylates (2-5A) that activate RNase L to cleave both host and viral single-stranded RNA, thereby limiting protein production, virus replication and spread, leading to apoptotic cell death. Endogenous host dsRNA, which accumulates in the absence of adenosine deaminase acting on RNA (ADAR)1, can also activate RNase L and lead to apoptotic cell death. RNase L activation and antiviral activity during infections with several types of viruses in human and bat cells is dependent on OAS3 but independent of virus-induced interferon (IFN) and, thus, RNase L can be activated even in the presence of IFN antagonists. Differently from other human viruses examined, Zika virus is resistant to the antiviral activity of RNase L and instead utilizes RNase L to enhance its replication factories to produce more infectious virus. Some betacoronaviruses antagonize RNase L activation by expressing 2′,5′-phosphodiesterases (PDEs) that cleave 2-5A and thereby antagonize activation of RNase L. The best characterized of these PDEs is the murine coronavirus (MHV) NS2 accessory protein. Enzymatically active NS2 is required for replication in myeloid cells and in the liver. Interestingly, while wild type mice clear MHV from the liver by 7–10 days post-infection, RNase L knockout mice fail to effectively clear MHV, probably due to diminished apoptotic death of infected cells. We suggest that RNase L antiviral activity stems from direct cleavage of viral genomes and cessation of protein synthesis as well as through promoting death of infected cells, limiting the spread of virus. Importantly, OASs are pattern recognition receptors and the OAS–RNase L pathway is a primary innate response pathway to viruses, capable of early response, coming into play before IFN is induced or when the virus shuts down IFN signaling.

scholarly journals Keratin 18 is an integral part of the intermediate filament network in murine skeletal muscle

2020 ◽  
Vol 318 (1) ◽  
pp. C215-C224 ◽  
Author(s):  
Joaquin M. Muriel ◽  
Andrea O’Neill ◽  
Jaclyn P. Kerr ◽  
Emily Kleinhans-Welte ◽  
Richard M. Lovering ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Isometric Force ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Type I ◽  
Mrna Levels ◽  
Force Transmission ◽  
Keratin 18 ◽  
Murine Skeletal Muscle

Intermediate filaments (IFs) contribute to force transmission, cellular integrity, and signaling in skeletal muscle. We previously identified keratin 19 (Krt19) as a muscle IF protein. We now report the presence of a second type I muscle keratin, Krt18. Krt18 mRNA levels are about half those for Krt19 and only 1:1,000th those for desmin; the protein was nevertheless detectable in immunoblots. Muscle function, measured by maximal isometric force in vivo, was moderately compromised in Krt18-knockout ( Krt18-KO) or dominant-negative mutant mice ( Krt18 DN), but structure was unaltered. Exogenous Krt18, introduced by electroporation, was localized in a reticulum around the contractile apparatus in wild-type muscle and to a lesser extent in muscle lacking Krt19 or desmin or both proteins. Exogenous Krt19, which was either reticular or aggregated in controls, became reticular more frequently in Krt19-null than in Krt18-null, desmin-null, or double-null muscles. Desmin was assembled into the reticulum normally in all genotypes. Notably, all three IF proteins appeared in overlapping reticular structures. We assessed the effect of Krt18 on susceptibility to injury in vivo by electroporating siRNA into tibialis anterior (TA) muscles of control and Krt19-KO mice and testing 2 wk later. Results showed a 33% strength deficit (reduction in maximal torque after injury) compared with siRNA-treated controls. Conversely, electroporation of siRNA to Krt19 into Krt18-null TA yielded a strength deficit of 18% after injury compared with controls. Our results suggest that Krt18 plays a complementary role to Krt19 in skeletal muscle in both assembling keratin-based filaments and transducing contractile force.

Effect of cyclosporin A treatment on the in vivo regulation of type I MHC gene expression

2004 ◽  
Vol 97 (2) ◽  
pp. 475-483 ◽  
Author(s):  
Julia M. Giger ◽  
Fadia Haddad ◽  
Anqi X. Qin ◽  
Kenneth M. Baldwin
Keyword(s):  
Cyclosporin A ◽  
Promoter Activity ◽  
Pcr Analysis ◽  
Type I ◽  
Mrna Levels ◽  
Activated T Cells ◽  
Obvious Effect ◽  
Enhancer Region ◽  
Muscle Gene

Rat soleus muscle consists predominantly of slow type I fibers. We have shown previously through deletion analysis that the highest level of reporter activity that we measure when injecting type I myosin heavy chain (MHC) promoter (MHC1)-linked luciferase plasmid into soleus muscles depends on the presence of a 550-bp upstream enhancer (3,450–2,900) region of the promoter. Because the calcineurin-nuclear factor of activated T cells (NFAT) pathway has been implicated in the regulation of the slow muscle gene program, particularly the MHC1 isoform, and the MHC1 promoter contains several putative NFAT sites, we examined via deletion and mutation analyses whether this pathway is involved in the regulation of promoter activity in soleus. Nine days of treatment with the calcineurin inhibitor cyclosporin A (CsA) caused a significant decrease in activity of the −3,500- and −3,450-bp promoters compared with vehicle-treated rats. Truncation of the promoter to −2,900 bp or smaller reduced the activity and also eliminated the CsA responsiveness, thus implying that the enhancer region is required for CsA responsiveness. Surprisingly, mutating the two NFAT elements within the enhancer region had no obvious effect on promoter activity. CsA treatment resulted in an increase in the mRNA levels of fast-type IIa and IIx MHC isoforms, but RT-PCR analysis of MHC1 pre-mRNA and mature mRNA expression in soleus muscles revealed no differences between vehicle- and CsA-treated rats. Although CsA affects the activity of the MHC1 promoter, it appears that its effect is not through direct binding of NFAT to sites on the promoter.

scholarly journals Activation of 2',5'-oligoadenylate synthetase activity on induction of HL-60 leukemia cell differentiation.

1989 ◽  
Vol 9 (9) ◽  
pp. 3897-3903 ◽  
Author(s):  
E L Schwartz ◽  
L A Nilson
Keyword(s):  
Leukemia Cell ◽  
Fold Increase ◽  
Polyclonal Antiserum ◽  
Synthetase Activity ◽  
Human Leukemia ◽  
Type I ◽  
Mrna Levels ◽  
Oligoadenylate Synthetase ◽  
Granulocytic Differentiation ◽  
Ifn Alpha

A 27-fold increase in 2',5'-oligoadenylate synthetase activity, an enzyme associated with the antiproliferative actions of interferon (IFN), was observed after treatment of HL-60 human leukemia cells with dimethyl sulfoxide (DMSO), an inducer of granulocytic differentiation of the cells. Enzyme activity was elevated after 24 h of exposure to DMSO, was maximal at 48 hours, and declined thereafter. A comparable increase was observed after treatment with 1 U of alpha interferon (IFN-alpha) per ml or 8 U of beta interferon (IFN-beta) per ml. Elevated levels of expression of other IFN-inducible genes, including type I histocompatibility antigen (HLA-B) mRNA and 2',5'-oligoadenylate phosphodiesterase activity, were also observed with DMSO treatment. DMSO-treated HL-60 cells had an increased amount of a 1.8-kilobase mRNA for oligoadenylate [oligo(A)] synthetase when compared with that of control cells; both DMSO- and IFN-treated HL-60 cells also expressed 1.6-, 3.4-, and 4.3-kilobase mRNA. The increase in both oligo(A) synthetase activity and mRNA levels was inhibited by polyclonal antiserum to human IFN-alpha; however, no IFN-alpha mRNA could be detected in the cells. Antiserum to IFN-beta or gamma interferon (IFN-gamma) had no effect on oligo(A) synthetase expression or activity nor was there any detectable IFN-beta 1 or IFN-beta 2 mRNA in the cells. The anti-IFN-alpha serum did not block the elevation of HLA-B mRNA in DMSO-treated cells. These observations suggest that the increased expression of oligo(A) synthetase in DMSO-treated cells may be mediated by the release of an IFN-alpha-like factor; however, the levels of any IFN-alpha mRNA produced in the cells were extremely low.

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