title: Lineage A Betacoronavirus NS2 Proteins and the Homologous Torovirus Berne pp1a Carboxy-Terminal Domain Are Phosphodiesterases That Antagonize Activation of RNase L.
abstract: Viruses in the familyCoronaviridae, within the orderNidovirales, are etiologic agents of a range of human and animal diseases, including both mild and severe respiratory diseases in humans. These viruses encode conserved replicase and structural proteins as well as more diverse accessory proteins, encoded in the 3' ends of their genomes, that often act as host cell antagonists. We previously showed that 2',5'-phosphodiesterases (2',5'-PDEs) encoded by the prototypicalBetacoronavirus, mouse hepatitis virus (MHV), and by Middle East respiratory syndrome-associated coronavirus antagonize the oligoadenylate-RNase L (OAS-RNase L) pathway. Here we report that additional coronavirus superfamily members, including lineage A betacoronaviruses and toroviruses infecting both humans and animals, encode 2',5'-PDEs capable of antagonizing RNase L. We used a chimeric MHV system (MHVMut) in which exogenous PDEs were expressed from an MHV backbone lacking the gene for a functional NS2 protein, the endogenous RNase L antagonist. With this system, we found that 2',5'-PDEs encoded by the human coronavirus HCoV-OC43 (OC43; an agent of the common cold), human enteric coronavirus (HECoV), equine coronavirus (ECoV), and equine torovirus Berne (BEV) are enzymatically active, rescue replication of MHVMutin bone marrow-derived macrophages, and inhibit RNase L-mediated rRNA degradation in these cells. Additionally, PDEs encoded by OC43 and BEV rescue MHVMutreplication and restore pathogenesis in wild-type (WT) B6 mice. This finding expands the range of viruses known to encode antagonists of the potent OAS-RNase L antiviral pathway, highlighting its importance in a range of species as well as the selective pressures exerted on viruses to antagonize it.IMPORTANCEViruses in the familyCoronaviridaeinclude important human and animal pathogens, including the recently emerged viruses severe acute respiratory syndrome-associated coronavirus (SARS-CoV) and Middle East respiratory syndrome-associated coronavirus (MERS-CoV). We showed previously that two viruses within the genusBetacoronavirus, mouse hepatitis virus (MHV) and MERS-CoV, encode 2',5'-phosphodiesterases (2',5'-PDEs) that antagonize the OAS-RNase L pathway, and we report here that these proteins are furthermore conserved among additional coronavirus superfamily members, including lineage A betacoronaviruses and toroviruses, suggesting that they may play critical roles in pathogenesis. As there are no licensed vaccines or effective antivirals against human coronaviruses and few against those infecting animals, identifying viral proteins contributing to virulence can inform therapeutic development. Thus, this work demonstrates that a potent antagonist of host antiviral defenses is encoded by multiple and diverse viruses within the familyCoronaviridae, presenting a possible broad-spectrum therapeutic target.
authors.affiliation: Department of Microbiology, Perlman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Goldstein
authors.affiliation: Department of Microbiology, Perlman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Thornbrough
authors.affiliation: Department of Microbiology, Perlman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA.
authors.forename: Babal K
authors.identifier: http://orcid.org/0000-0002-7660-5255
authors.initials: BK
authors.lastname: Jha
authors.affiliation: Department of Microbiology, Perlman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Yize
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Microbiology, Perlman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Ruth
authors.initials: R
authors.lastname: Elliott
authors.affiliation: Department of Microbiology, Perlman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Katherine
authors.initials: K
authors.lastname: Quiroz-Figueroa
authors.affiliation: Department of Microbiology, Perlman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Annie I
authors.initials: AI
authors.lastname: Chen
authors.affiliation: Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Silverman
authors.affiliation: Department of Microbiology, Perlman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA weisssr@upenn.edu.
authors.forename: Susan R
authors.identifier: http://orcid.org/0000-0002-8155-4528
authors.initials: SR
authors.lastname: Weiss
mesh_terms: D000227:Adenine Nucleotides / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D002460:Cell Line; D017124:Conserved Sequence; D006224:Cricetinae; D004722:Endoribonucleases / Q000378:metabolism*; D004789:Enzyme Activation; D008264:Macrophages / Q000821:virology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D065207:Middle East Respiratory Syndrome Coronavirus / Q000201:enzymology*; D006517:Murine hepatitis virus / Q000201:enzymology*; D009843:Oligoribonucleotides / Q000737:chemistry; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry / Q000502:physiology*; D017003:Torovirus / Q000201:enzymology*; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000502:physiology*; D014779:Virus Replication
chemical_list: D000227:Adenine Nucleotides; D009843:Oligoribonucleotides; D017361:Viral Nonstructural Proteins; C023505:2',5'-oligoadenylate; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease; D010727:Phosphoric Diester Hydrolases
keywords: RNase L; interferon antagonist; lineage A coronavirus; oligoadenylate synthetase; phosphodiesterase; torovirus