The double-stranded (ds) RNA-activated protein kinase, PKR, is one of several proteins induced by interferon and plays a pivotal role in the cellular antiviral response. PKR has also been implicated in cellular signaling involved in transformation, differentiation and apoptosis. PKR is synthesized in a latent state. Binding to dsRNA induces autophosphorylation reactions that activate the kinase. The most well characterized substrate of PKR is the eukaryotic initiation factor elF2alpha; phosphorylation of this protein blocks protein synthesis in virally infected cells. The broad objective of this research program is to define the molecular basis of PKR activation. The critical protein-protein and protein- RNA interactions that modulate the activity of PKR are not well understood. Thus, we propose to define the stoichiometries, affinities and free energy couplings for the formation of macromolecular complexes involved in PKR activation using quantitative solution biophysical methods. Specifically, equilibrium and velocity analytical ultracentrifugation will define the association states and hydrodynamic properties of full-length PKR and domain constructs. These measurements will test the hypothesis that PKR exists in a monomer-dimer equilibrium modulated by phosphorylation state and will probe conformational changes and domain interactions associated with activation. The affinity and orientation of PKR binding to activating and nonactivating synthetic RNAs of variable lengths will be characterized using our novel sedimentation equilibrium method along with CD, fluorescence and affinity cleavage measurements. These studies will test our overlapping ligand model for PKR binding to dsRNA and will correlate RNA binding mode with enzymatic activation. We have designed RNA sequences containing base pair mismatches, bulges and internal loops to systematically probe the structural features that distinguish RNA activators from those that fail to activate. These experiments will be extended to include natural viral RNA activators and inhibitors with complex secondary structures. A detailed mechanistic understanding of PKR activation will provide a foundation for the design of therapeutic agents that target PKR for the treatment of viral infections and cancer.
| 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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