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Mutant viruses that lack the HSV-1 g34.5 gene fail to grow on many human malignant neuronal cells, as eIF2 is phosphorylated and protein synthesis is blocked. PKR, a cellular kinase involved in PDGF and interferon signaling, is activated by viral infection and phosphorylates eIF2a. We have isolated variant viruses that lack the g34.5 gene, yet grow on neuronal cells. These variants are second-site suppressors as they lack the g34.5 gene and contain additional mutations that affect a distinct viral genetic element, the SUP locus. Remarkably, specific removal of 583 base-pairs of DNA from the SUP locus completely precludes the accumulation of phosphorylated eIF2. Consequently, suppressor g34.5 variants can synthesize proteins and multiply on cells that fail to support replication of the parental g34.5 mutants. A major focus of the laboratory is to understand how alterations of the SUP locus allow the virus to overcome the actions of the activated PKR kinase. Understanding the nature of the SUP locus will thus elucidate events that occur prior to eIF2 phosphorylation and define a new effector involved in the control of protein synthesis. Additionally, the viral g34.5 gene contains a region homologous to a cellular gene (GADD34) induced in response to agents that promote growth arrest, DNA damage, and differentiation. Protein synthesis checkpoints controlled by PKR may function in all of these processes. Understanding how the HSV- 1 SUP locus effects PKR signaling may aid in identifying cellular molecules with similar functions. Viral genetics can thus provide a powerful inroad into key cellular signaling pathways.
A second area of interest involves the design and use of attenuated, replication competent viruses that can discriminate between normal and malignant cells. HSV-1 g34.5 mutant viruses are non-neurovirulent in animals, and appear to be sufficiently attenuated for intracranial administration. However, these mutant viruses grow poorly in neuronal tumors, imposing a major limitation on their effectiveness in destroying tumor tissue. The suppressor mutants described above have regained the ability to grow in neoplastic cells, but have retained the attenuated phenotype of the g34.5 parent virus. They are thus potentially ideal prototypes for a 3tumorcidal2 virus that could destroy malignant cells in the CNS.
Cellular 5'-3' mRNA exonuclease xrn1 controls double-stranded RNA accumulation and anti-viral responses
Burgess, Hannah M; Mohr, Ian. Cellular 5'-3' mRNA exonuclease xrn1 controls double-stranded RNA accumulation and anti-viral responses. Cell host & microbe. 2015 Mar;17(3):332-344 (1506952)
An investigation of herpes simplex virus type 1 latency in a novel mouse dorsal root ganglion model suggests a role for ICP34.5 in reactivation
Mattila, Riikka Katriina; Harila, Kirsi; Kangas, Salla Maria; Paavilainen, Henrik; Heape, Anthony Martin; Mohr, Ian J; Hukkanen, Veijo. An investigation of herpes simplex virus type 1 latency in a novel mouse dorsal root ganglion model suggests a role for ICP34.5 in reactivation. Journal of general virology. 2015 Apr;:2304-2313 (1532592)
Co-opting the Fanconi Anemia Genomic Stability Pathway Enables Herpesvirus DNA Synthesis and Productive Growth
Karttunen, Heidi; Savas, Jeffrey N; McKinney, Caleb; Chen, Yu-Hung; Yates, John R 3rd; Hukkanen, Veijo; Huang, Tony T; Mohr, Ian. Co-opting the Fanconi Anemia Genomic Stability Pathway Enables Herpesvirus DNA Synthesis and Productive Growth. Molecular cell. 2014 Jun;55(1):111-122 (1055622)
Using homogeneous primary neuron cultures to study fundamental aspects of HSV-1 latency and reactivation
Kim, Ju Youn; Shiflett, Lora A; Linderman, Jessica A; Mohr, Ian; Wilson, Angus C. Using homogeneous primary neuron cultures to study fundamental aspects of HSV-1 latency and reactivation. Methods in molecular biology. 2014 ;1144:167-179 (970092)
Global reprogramming of the cellular translational landscape facilitates cytomegalovirus replication
McKinney, Caleb; Zavadil, Jiri; Bianco, Christopher; Shiflett, Lora; Brown, Stuart; Mohr, Ian. Global reprogramming of the cellular translational landscape facilitates cytomegalovirus replication. Cell reports. 2014 Jan;6(1):9-17 (759792)