Most viruses express during
infection products that prevent or neutralize the effect of the host dsRNA activated
protein kinase (PKR). Translation of Sindbis virus (SINV)
mRNA escapes to PKR activation and
eIF2 phosphorylation in infected cells by a mechanism that requires a stem loop structure in viral 26S
mRNA termed DLP to initiate translation in the absence of functional
eIF2. Unlike the rest of viruses tested, we found that
Alphavirus infection allowed a strong PKR activation and eIF2α phosphorylation in vitro and in infected animals so that the presence of DLP structure in
mRNA was critical for translation and replication of SINV. Interestingly,
infection of MEFs with some viruses that express PKR inhibitors prevented eIF2α phosphorylation after
superinfection with SINV, suggesting that viral anti-PKR mechanisms could be exchangeable. Thus, translation of SINV mutant lacking the DLP structure (ΔDLP) in 26S
mRNA was partially rescued in cells expressing vaccinia virus (VV) E3
protein, a known inhibitor of PKR. This case of heterotypic complementation among evolutionary distant viruses confirmed experimentally a remarkable case of convergent evolution in viral anti-PKR mechanisms. Our data reinforce the critical role of PKR in regulating virus-host interaction and reveal the versatility of viruses to find different solutions to solve the same conflict.