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Mol. Cell. Biol., Nov 1996, 6295-6302, Vol 16, No. 11
DR Taylor, SB Lee, PR Romano, DR Marshak, AG Hinnebusch, M Esteban and MB Mathews
The interferon-induced RNA-dependent protein kinase PKR is found in cells
in a latent state. In response to the binding of double-stranded RNA, the
enzyme becomes activated and autophosphorylated on several serine and
threonine residues. Consequently, it has been postulated that
autophosphorylation is a prerequisite for activation of the kinase. We
report the identification of PKR sites that are autophosphorylated in vitro
concomitantly with activation and examine their roles in the activation of
PKR. Mutation of one site, threonine 258, results in a kinase that is less
efficient in autophosphorylation and in phosphorylating its substrate, the
initiation factor eIF2, in vitro. The mutant kinase is also impaired in
vivo, displaying reduced ability to inhibit protein synthesis in yeast and
mammalian cells and to induce a slow-growth phenotype in Saccharomyces
cerevisiae. Mutations at two neighboring sites, serine 242 and threonine
255, exacerbated the effect. Taken together with earlier results (S. B.
Lee, S. R. Green, M. B. Mathews, and M. Esteban, Proc. Natl. Acad. Sci. USA
91:10551-10555, 1994), these data suggest that the central part of the PKR
molecule, lying between its RNA-binding and catalytic domains, regulates
kinase activity via autophosphorylation.
Copyright © 1996, American Society for Microbiology
Autophosphorylation sites participate in the activation of the double- stranded-RNA-activated protein kinase PKR
Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
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