Inhibition of host translation by virus infection in vivo

Abstract

Infection of cultured cells with lytic animal viruses often results in the selective inhibition of host protein synthesis, whereas viral mRNA is efficiently translated under these circumstances. This phenomenon, known as "shut off," has been well described at the molecular level for some viruses, but there is not yet any direct or indirect evidence supporting the idea that it also should operate in animals infected with viruses. To address this issue, we constructed recombinant Sindbis virus (SV)-expressing reporter mRNA, the translation of which is sensitive or resistant to virus-induced shut off. As found in cultured cells, replication of SV in mouse brain was associated with a strong phosphorylation of eukaryotic initiation factor (eIF2) that prevented translation of reporter mRNA (luciferase and EGFP). Translation of these reporters was restored in vitro, in vivo, and ex vivo when a viral RNA structure, termed downstream hairpin loop, present in viral 26S mRNA, was placed at the 5′ end of reporter mRNAs. By comparing the expression of shut off-sensitive and -resistant reporters, we unequivocally concluded that replication of SV in animal tissues is associated with a profound inhibition of nonviral mRNA translation. A strategy as simple as that followed here might be applicable to other viruses to evaluate their interference on host translation in infected animals.eukaryotic initiation factor-2 phosphorylation | dsRNA-dependent protein kinase | Sindbis

The IRF-3/Bax-Mediated Apoptotic Pathway, Activated by Viral Cytoplasmic RNA and DNA, Inhibits Virus Replication

“…This distinction is further supported by the fact that TLR3 signaling, which activates IRF-3 to transcribe similarly induced genes, is incapable of inducing an apoptotic effect, as the apoptotic pathway is not activated by TLR3. Because cellular protein synthesis is often shut off by virus infection (32,33), the existence of a transcription-independent apoptotic mechanism ensures that the cell death-mediated antiviral response is still operative in the absence of the host protein synthesis machinery.…”

Adaptive Changes in Alphavirus mRNA Translation Allowed Colonization of Vertebrate Hosts

“…Contrary to what has been observed for most viruses, infection of murine cells with SINV or Semliki Forest virus (SFV) resulted in a strong activation of PKR, which leads a complete phosphorylation (and inactivation) of eIF2␣ (14,54). Viral 26S mRNAs that encode the structural proteins of SINV are efficiently translated under these conditions by means of a prominent cis-acting secondary structure in this mRNA that allows location of 40S ribosome on initiator AUG in the absence of eIF2 (50,54). This structure, called the downstream loop (DLP), is located 28 nucleotides (nt) downstream from the AUG in SINV 26S mRNA and in other members of the Alphavirus group (see below).…”

“…For mouse infections, 10 7 PFU of virus was used to inoculate animals by the intranasal route under isoflurane anesthesia. At the times indicated, animals were sacrificed and brains were extracted for virus yield determination or immunofluorescence analysis using the anti-SINV capsid antisera as described previously (50).…”

“…In previous reports, we found that a stable DLP structure of RNA located downstream from the initiation codon was necessary and sufficient to support eIF2-independent translation initiation of subgenomic (26S) mRNAs in SINV-infected 3T3 cells (50,54). To test the importance of DLP structure in virus replication, I used a SINV mutant in which the structure of DLP has been destroyed by 7 point mutations as described previously (54).…”

“…C6/36 cells were grown in M3 medium supplemented with 10% fetal calf serum, gentamicin, antibiotics, and antimycotic. SINV (AR339 strain) and SFV were amplified in BHK21 cells and purified through a sucrose cushion as described previously (50). The Aura virus (AURAV; strain BeAR 10315) was purchased from ATCC (catalog no.…”