On the Control of Immediate Early ( ) mRNA Survival in Cells Infected with Herpes Simplex Virus

Abstract

SI~IMMARYThe ~ or immediate early mRNA of herpes simplex virus strain HSV-2(G) had a half-life of about 15 min if made in the absence of viral protein synthesis but was relatively stable if viral protein synthesis occurred, either freely or restricted by the presence of the proline analogue azetidine. In contrast, the ~ mRNA of other strains of the virus is stable, even in the absence of protein synthesis. Studies with recombinant viruses showed that the region of the viral DNA between 0.58 and 0.65 map units [which includes the gene (vhs, UL41) that controls virion-mediated shutoff of host protein synthesis] is important in determining the survival of ~ mRNA. In mixed infection experiments HSV-2(G) inhibited ~ as well as host protein synthesis but the shutoff activity appeared to be short-lived. Within 3 h after infection, as a result of protein synthesis, cells became completely resistant to shutoff by superinfecting virus.

Transfer of UL41, the gene controlling virion-associated host cell shutoff, between different strains of herpes simplex virus

“…This suggestion was based on the observation that after mixed infection, HSV-I(F), which expresses stable IE mRNAs, stabilized the normally unstable IE mRNA of HSV-2(G) (Fenwick & Clark, 1982. It was observed later that the stability ofIE mRNA was determined by a gene or genes between 0.58 and 0-65 map units and that if the dominance of mRNA stability over strong shutoff seen in mixed infection also determined the phenotypes of intertypic recombinant viruses, then the specific hypothetical mRNA-stabilizing factor mapped in this region (Fenwick & Owen, 1988). However the present results show that the opposite is true: in recombinants 17G41 and 17(41-)G41 the strong shutoff of HSV-2(G) is dominant.…”

“…It is known that the half-lives of all mRNAs of HSV-I(KOS) (1 to 2 h) were considerably increased by a mutation in the vhs gene, UL41 (Read & Frenkel, 1983;Kwong & Frenkel, 1987;Oroskar & Read, 1987 and the exceptional instability of the IE mRNA of HSV-2(G) in the presence of CX (half-life of about 15 min) may reflect the action of a strong shutoff protein on mRNA unprotected by ribosomes. The RNA accumulated in stable form after removal of CX or during normal infection (Fenwick & Owen, 1988). The apparent discrimination of the shutoff mechanism between host and viral protein synthesis may be explained by the hypothesis that the shutoff activity is short-lived (Fenwick & Owen, 1988) and degradation of mRNA induced by UL41 is more than counterbalanced by the increasing rate of transcription of viral mRNA while that of cellular mRNA is steady or declining.…”

“…The RNA accumulated in stable form after removal of CX or during normal infection (Fenwick & Owen, 1988). The apparent discrimination of the shutoff mechanism between host and viral protein synthesis may be explained by the hypothesis that the shutoff activity is short-lived (Fenwick & Owen, 1988) and degradation of mRNA induced by UL41 is more than counterbalanced by the increasing rate of transcription of viral mRNA while that of cellular mRNA is steady or declining.…”

“…HSV-I(17 +) causes only slight inhibition, and its IE mRNA accumulates in the presence of cycloheximide (CX) added at the time of infection and is translated on removal of the inhibitor. In contrast, HSV-2(G) shuts off host synthesis strongly; also its IE mRNA is very unstable and does not accumulate unless protein synthesis is allowed (Fenwick & Clark, 1983;Fenwick & Owen, 1988). To investigate the functions of gene UL41 and in particular the question of whether it alone determines both phenotypes, we have isolated the analogous gene from HSV-2(G) and inserted it into the non-essential thymidine kinase (TK) gene of HSV-I(17+).…”

A Single Amino Acid Substitution in Herpes Simplex Virus Type 1 VP16 Inhibits Binding to the Virion Host Shutoff Protein and Is Incompatible with Virus Growth

“…vhs, a 489-amino-acid phosphoprotein that, like VP16, exists as a preformed viral structural component, disables host protein synthesis and triggers mRNA degradation following infection (13,24,25,35,40,43,47,52). vhs is not required for HSV-1 propagation in tissue culture, although in its absence, the expression of viral proteins is altered during an infection and there is a significant reduction in virus yield (39,40).…”