The herpes simplex virus host shutoff (vhs) RNase limits accumulation of double stranded RNA in infected cells: Evidence for accelerated decay of duplex RNA

Abstract

The herpes simplex virus virion host shutoff (vhs) RNase destabilizes cellular and viral mRNAs and blunts host innate antiviral responses. Previous work demonstrated that cells infected with vhs mutants display enhanced activation of the host double-stranded RNA (dsRNA)-activated protein kinase R (PKR), implying that vhs limits dsRNA accumulation in infected cells. Confirming this hypothesis, we show that partially complementary transcripts of the UL23/UL24 and UL30/31 regions of the viral genome increase in abundance when vhs is inactivated, giving rise to greatly increased levels of intracellular dsRNA formed by annealing of the overlapping portions of these RNAs. Thus, vhs limits accumulation of dsRNA at least in part by reducing the levels of complementary viral transcripts. We then asked if vhs also destabilizes dsRNA after its initial formation. Here, we used a reporter system employing two mCherry expression plasmids bearing complementary 3’ UTRs to produce defined dsRNA species in uninfected cells. The dsRNAs are unstable, but are markedly stabilized by co-expressing the HSV dsRNA-binding protein US11. Strikingly, vhs delivered by super-infecting HSV virions accelerates the decay of these pre-formed dsRNAs in both the presence and absence of US11, a novel and unanticipated activity of vhs. Vhs binds the host RNA helicase eIF4A, and we find that vhs-induced dsRNA decay is attenuated by the eIF4A inhibitor hippuristanol, providing evidence that eIF4A participates in the process. Our results show that a herpesvirus host shutoff RNase destabilizes dsRNA in addition to targeting partially complementary viral mRNAs, raising the possibility that the mRNA destabilizing proteins of other viral pathogens dampen the host response to dsRNA through similar mechanisms.

Time-course profiling of bovine alphaherpesvirus 1.1 transcriptome using multiplatform sequencing

“…These overlaps may give rise to double-stranded RNAs (dsRNAs), which are targeted by the dsRNA-activated protein kinase R 59 or type I interferon system 60 of the host, thereby effectively reducing viral translation. In a recent publication Dauber and co-workers reported the mechanism of how HSV-1 virion host shut-off (VHS) protein limits the accumulation of viral dsRNAs 61 . In light of these findings, it is possible that the frequency of RNA polymerase II readthroughs are much higher than expected from the basis of ratio of read-thorough transcripts.…”

Herpes Simplex Virus Type 1 Interactions with the Interferon System

“…vhs also reduces the accumulation of viral dsRNA in host cells ( Figure 4 ). Human foreskin fibroblasts and HeLa cells infected with vhs null HSV-1 had higher levels of dsRNA accumulating in the cells compared to wild type virus [ 208 ]. vhs plays an important role in regulating the levels of dsRNA available for RNA sensors to detect, limiting the innate immune response.…”

HSV-1 Modulates IL-6 Receptor Expression on Human Dendritic Cells

“…The viral protein vhs does not only degrade cellular mRNA, in order to shut off the host protein synthesis, but also negatively affects viral mRNAs, which enables a rapid transition between the three gene expression phases of HSV-1 ( 70 ). Furthermore, vhs limits dsRNA accumulation in HSV-1-infected cells ( 71 ). The viral protein vhs is active immediately after tegument release and during early stages of infection.…”