Molecular basis of PKR activation by Interferon-gamma (IFNγ) mRNA 5'-UTR

Abstract

PKR is an interferon (IFN)-induced protein kinase that is activated by double-stranded RNA in a mechanism involving binding of the N-terminal domain of PKR, protein dimerization and autophosphorylation. PKR is a key component of the cellular antiviral response and plays critical roles in a variety of other cellular processes including signal transduction, growth and apoptosis. Once activated, PKR phosphorylates its substrate, translation initiation factor (eIF2) on its alpha subunit at Ser51, thereby leading to an inhibition of protein synthesis. The IFN-gamma mRNA 5'-UTR, an H-type pesudoknot structure, is also a PKR activator. Activation through this structure thus and inhibition of translation thus autoregulates of overexpression of the IFN-gamma mRNA.Herein, I present a biochemical and biophysical characterization of the interaction between PKR and IFN-gamma mRNA 5'-UTR. In vitro PKR autophosphorylation assays defined that the minimal requirement of IFN-gamma mRNA 5'-UTR domain for PKR autophosphorylation is a 120 nt fragment that also exhibits the pseudoknot conformation. Additionally, mutations to disrupt IFN-gamma mRNA pseudoknot base pairing and stability decreased the ability to induce PKR autophosphorylation. Interaction of IFN-gamma 120 RNA and PKR appears to exhibit a ~1:2 binding stoichiometry. These results show that IFN-gamma mRNA binding to PKR is in agreement with other PKR activators; binding of dsRNA to PKR promotes dimerization and autophosphorylation.

Date of Award	31 Dec 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Ewan Blanch (Supervisor)