The RNA-activated protein kinase, PKR, is induced by interferon and plays a pivotal role in the innate immunity response to viral infection. PKR is synthesized in a latent state, but upon binding activating RNAs it undergoes autophosphorylation reactions that activate the kinase. Phosphorylation of the eukaryotic initiation factor eIF2a by PKR inhibits viral protein synthesis. PKR is also activated by cytokines, growth factor withdrawal and stress signals and participates in pathways regulating stress response, cellular growth and proliferation, nutrient signaling and metabolism. The broad objective of our research program is to define the molecular mechanisms that regulate the activity of PKR using quantitative biophysical and structural methods.
In Aim I we will define the interactions of PKR with complex RNA inhibitors and activators. Specifically, we will identify the structural features within the Adenovirus VAI RNA that mediate high-affinity PKR binding without activating the kinase, determine the mechanism of activation of PKR by novel single stranded-double stranded RNAs and correlate PKR dimerization and activation with the length and flexibility of a linker region in model RNAs. PKR represents an attractive target for development of novel antiviral therapies to enhance the innate immune response and in Aim 2 we will use a nonradioactive assay to screen libraries of drug-like compounds for novel PKR activators.
In Aim 3, small angle scattering methods will be used to determine the conformation of ordered forms of PKR and to develop structural model of complexes of PKR with RNA inhibitors and activators. These studies will provide the foundation for the design of therapeutic agents that target PKR for the treatment of viral infections and cancer.

Public Health Relevance

PKR plays a central role in the biological activity of interferons, which are widely employed in the treatment of viral, neoplastic and immunological diseases. However, the therapeutic effectiveness of interferons is compromised by severe side effects as well as viral resistance mechanisms that inhibit the PKR pathway. A detailed understanding of the molecular mechanism of PKR activation will help us to design new drugs that will selectively activate PKR to avoid side effects and to evade viral resistance.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Macromolecular Structure and Function B Study Section (MSFB)
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Dempsey, Walla L
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University of Connecticut
Schools of Arts and Sciences
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Mayo, Christopher B; Cole, James L (2017) Interaction of PKR with single-stranded RNA. Sci Rep 7:3335
Husain, Bushra; Mayo, Christopher; Cole, James L (2016) Role of the Interdomain Linker in RNA-Activated Protein Kinase Activation. Biochemistry 55:253-61
Mayo, Christopher B; Wong, C Jason; Lopez, Prisma E et al. (2016) Activation of PKR by short stem-loop RNAs containing single-stranded arms. RNA 22:1065-75
Husain, Bushra; Hesler, Stephen; Cole, James L (2015) Regulation of PKR by RNA: formation of active and inactive dimers. Biochemistry 54:6663-72
Launer-Felty, Katherine; Wong, C Jason; Cole, James L (2015) Structural analysis of adenovirus VAI RNA defines the mechanism of inhibition of PKR. Biophys J 108:748-57
Launer-Felty, Katherine; Cole, James L (2014) Domain interactions in adenovirus VAI RNA mediate high-affinity PKR binding. J Mol Biol 426:1285-95
Lyons, Daniel F; Lary, Jeffrey W; Husain, Bushra et al. (2013) Are fluorescence-detected sedimentation velocity data reliable? Anal Biochem 437:133-7
Husain, Bushra; Mukerji, Ishita; Cole, James L (2012) Analysis of high-affinity binding of protein kinase R to double-stranded RNA. Biochemistry 51:8764-70
Anderson, Eric; Pierre-Louis, Willythssa S; Wong, C Jason et al. (2011) Heparin activates PKR by inducing dimerization. J Mol Biol 413:973-84
Wong, C Jason; Launer-Felty, Katherine; Cole, James L (2011) Analysis of PKR-RNA interactions by sedimentation velocity. Methods Enzymol 488:59-79

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