title: A Single Amino Acid Dictates Protein Kinase R Susceptibility to Unrelated Viral Antagonists.
abstract: During millions of years of coevolution with their hosts, cytomegaloviruses (CMVs) have succeeded in adapting to overcome host-specific immune defenses, including the protein kinase R (PKR) pathway. Consequently, these adaptations may also contribute to the inability of CMVs to cross species barriers. Here, we provide evidence that the evolutionary arms race between the antiviral factor PKR and its CMV antagonist TRS1 has led to extensive differences in the species-specificity of primate CMV TRS1 proteins. Moreover, we identify a single residue in human PKR that when mutated to the amino acid present in African green monkey (Agm) PKR (F489S) is sufficient to confer resistance to HCMVTRS1. Notably, this precise molecular determinant of PKR resistance has evolved under strong positive selection among primate PKR alleles and is positioned within the αG helix, which mediates the direct interaction of PKR with its substrate eIF2α. Remarkably, this same residue also impacts sensitivity to K3L, a poxvirus-encoded pseudosubstrate that structurally mimics eIF2α. Unlike K3L, TRS1 has no homology to eIF2α, suggesting that unrelated viral genes have convergently evolved to target this critical region of PKR. Despite its functional importance, the αG helix exhibits extraordinary plasticity, enabling adaptations that allow PKR to evade diverse viral antagonists while still maintaining its critical interaction with eIF2α.
authors: Departments of Microbiology and Medicine, University of Washington, Seattle Washington, and Divisions of Human Biology and Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors: Kathryn S
authors: http://orcid.org/0000-0003-0829-4544
authors: KS
authors: Carpentier
authors: Departments of Microbiology and Medicine, University of Washington, Seattle Washington, and Divisions of Human Biology and Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors: Nicolle M
authors: NM
authors: Esparo
authors: Departments of Microbiology and Medicine, University of Washington, Seattle Washington, and Divisions of Human Biology and Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors: Stephanie J
authors: SJ
authors: Child
authors: Departments of Microbiology and Medicine, University of Washington, Seattle Washington, and Divisions of Human Biology and Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors: Adam P
authors: AP
authors: Geballe
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003587:Cytomegalovirus / Q000378:metabolism / Q000472:pathogenicity; D003586:Cytomegalovirus Infections / Q000235:genetics; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006801:Humans; D015151:Immunoblotting; D009154:Mutation; D014764:Viral Proteins / Q000378:metabolism*; D014779:Virus Replication / Q000235:genetics; D019892:eIF-2 Kinase / Q000235:genetics*
chemical_list: D015852:Eukaryotic Initiation Factor-2; C072216:TRS1 protein, Human herpesvirus 5; D014764:Viral Proteins; D019892:eIF-2 Kinase