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.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 J+Virol
2015 ; 89
(5
): 2575-89
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The stress granule protein G3BP1 recruits protein kinase R to promote multiple
innate immune antiviral responses
#MMPMID25520508
Reineke LC
; Lloyd RE
J Virol
2015[Mar]; 89
(5
): 2575-89
PMID25520508
show ga
Stress granules (SGs) are cytoplasmic storage sites containing translationally
silenced mRNPs that can be released to resume translation after stress subsides.
We previously showed that poliovirus 3C proteinase cleaves the SG-nucleating
protein G3BP1, blocking the ability of cells to form SGs late in infection. Many
other viruses also target G3BP1 and inhibit SG formation, but the reasons why
these functions evolved are unclear. Previously, we also showed a link between
G3BP1-induced SGs and protein kinase R (PKR)-mediated translational control, but
the mechanism of PKR interplay with SG and the antiviral consequences are
unknown. Here, we show that G3BP1 exhibits antiviral activity against several
enteroviruses, whereas truncated G3BP1 that cannot form SGs does not.
G3BP1-induced SGs are linked to activation of innate immune transcriptional
responses through NF-?B and JNK. The G3BP1-induced SGs also recruit PKR and other
antiviral proteins. We show that the PXXP domain within G3BP1 is essential for
the recruitment of PKR to SGs, for eIF2? phosphorylation driven by PKR, and for
nucleating SGs of normal composition. We also show that deletion of the PXXP
domain in G3BP1 compromises its antiviral activity. These findings tie PKR
activation to its recruitment to SGs by G3BP1 and indicate that G3BP1 promotes
innate immune responses at both the transcriptional and translational levels and
integrates cellular stress responses and innate immunity. IMPORTANCE: Stress
granules appear during virus infection, and their importance is not well
understood. Previously, it was assumed that they were nonfunctional artifacts
associated with cellular stress. PKR is a well-known antiviral protein; however,
its regulation in cells is not well understood. Our work links cellular stress
granules with activation of PKR and other innate immune pathways through the
activity of G3BP1, a critical stress granule component. The ability of stress
granules and G3BP1 to activate PKR and other innate immune transcriptional
responses indicates that G3BP1 is an antiviral protein. This work helps to refine
a longstanding paradigm indicating stress granules are inert structures and
explains why G3BP1 is subverted by many viruses to promote a productive
infection.