The herpes simplex virus vhs protein induces endoribonucleolytic cleavage of target RNAs in cell extracts

The herpes simplex virus virion host shutoff (vhs) protein (UL41 gene produ ct) is a component of the HSV virion tegument that triggers shutoff of host protein synthesis and accelerated mRNA degradation during the early stages of Hm infection. Previous studies have demonstrated that extracts from HSV -infected cells and partially purified HSV virions display vhs-dependent RN ase activity and that vhs is sufficient to trigger accelerated RNA degradat ion when expressed as the only HSV protein in an in vitro translation syste m derived from rabbit reticulocytes. We have used the rabbit reticulocyte t ranslation system to characterize the mode of vhs-induced RNA decay in more detail. We report here that vhs-dependent RNA decay proceeds through endor ibonucleolytic cleavage, is not affected by the presence of a 5' cap or a 3 ' poly(A) tail in the RNA substrate, requires Mg2+, and occurs in the absen ce of ribosomes. Intriguingly, sites of preferential initial cleavage were clustered over the 5' quadrant of one RNA substrate that was characterized in detail. The vhs homologue of pseudorabies virus also induced accelerated RNA decay in this in vitro system.