During lytic infections, the herpes simplex virus (HSV) virion host shutoff (Vhs) endoribonuclease degrades many host and viral mRNAs. Within infected cells it cuts mRNAs at preferred sites, including some in regions of translation initiation. Vhs binds the translation initiation factors eIF4H, eIF4AI, and eIF4AII, suggesting that its mRNA degradative function is somehow linked to translation. To explore how Vhs is targeted to preferred sites, we examined the in vitro degradation of a target mRNA in rabbit reticulocyte lysates containing in vitro-translated Vhs. Vhs caused rapid degradation of mRNAs beginning with cleavages at sites in the first 250 nucleotides, including a number near the start codon and in the 5= untranslated region. Ligation of the ends to form a circular mRNA inhibited Vhs cleavage at the same sites at which it cuts capped linear molecules. This was not due to an inability to cut any circular RNA, since Vhs cuts circular mRNAs containing an encephalomyocarditis virus (EMCV) internal ribosome entry site (IRES) at the same sites as linear molecules with the IRES. Cutting linear mRNAs at preferred sites was augmented by the presence of a 5= cap. Moreover, mutations that altered the 5= proximal AUG abolished Vhs cleavage at nearby sites, while mutations that changed sequences surrounding the AUG to improve their match to the Kozak consensus sequence enhanced Vhs cutting near the start codon. The results indicate that mutations in an mRNA that affect its translation affect the sites at which it is cut by Vhs and suggest that Vhs is directed to its preferred cut sites during translation initiation. During lytic herpes simplex virus (HSV) infections, viral and cellular gene expressions are regulated at multiple steps of mRNA metabolism (1, 2), including transcription (2-8), splicing (2, 9-12), transport from the nucleus to the cytoplasm (2, 13-20), translation (21-32), and stabilization of mRNAs in the cytoplasm (33-43). Among the posttranscriptional controls are the regulation of mRNA half-lives (36-42) and translation (23,29) by the HSV virion host shutoff (Vhs) protein (UL41). Vhs is an endoribonuclease (33,(44)(45)(46)(47) that is a minor component of virions (48)(49)(50). At early times, copies of Vhs from infecting virions accelerate the degradation of many housekeeping and constitutively expressed cellular mRNAs (40,42,48,(51)(52)(53)(54)(55), with a concomitant downturn in the levels of those mRNAs and in the synthesis of the proteins that they encode (52,56,57). Following the onset of viral transcription, Vhs ensures the rapid turnover of most, if not all, viral mRNAs (36, 37, 57-60). In so doing, it helps determine viral mRNA levels and facilitates the sequential expression of different classes of viral mRNAs (38). Significantly, during animal infections, Vhs impedes the establishment of an interferon-induced antiviral state (61-67). It blocks the activation of dendritic cells (68-70) and inhibits other components of the innate and adaptive immune responses (41,(71)(72)(73)(74)(75). As su...

The mTOR pathway integrates both extracellular and intracellular signals and serves as a central regulator of cell metabolism, growth, survival, and stress responses. Neurotropic viruses, such as herpes simplex virus-1 (HSV-1), also rely on cellular AKT-mTORC1 signaling to achieve viral latency. Here, we define a novel genotoxic response whereby spatially separated signals initiated by extracellular neurotrophic factors and nuclear DNA damage are integrated by the AKT-mTORC1 pathway. We demonstrate that endogenous DNA double-strand breaks (DSBs) mediated by Topoisomerase 2b-DNA cleavage complex (TOP2bcc) intermediates are required to achieve AKT-mTORC1 signaling and maintain HSV-1 latency in neurons. Suppression of host DNA-repair pathways that remove TOP2bcc trigger HSV-1 reactivation. Moreover, perturbation of AKT phosphorylation dynamics by downregulating the PHLPP1 phosphatase led to AKT mis-localization and disruption of DSB-induced HSV-1 reactivation. Thus, the cellular genome integrity and environmental inputs are consolidated and co-opted by a latent virus to balance lifelong infection with transmission.

Recent studies have shown that many bone cell-targeted Cre models are not as specific as originally thought. To ensure accurate data interpretation, it is important for investigators to test for unexpected recombination events due to transient expression of Cre recombinase during development or in precursor cells and to be aware of the potential for germ line recombination of targeted genes as well as the potential for unexpected phenotypes due to the Cre transgene. Although many of the bone-targeted Cre-deleter strains are imperfect and each model has its own limitations, their careful use will continue to provide key advances in our understanding of bone cell function in health and disease.

SUMMARY Unlike many viruses that suppress cellular protein synthesis, host mRNA translation and polyribosome formation are stimulated by human cytomegalovirus (HCMV). How HCMV impacts the translationally-regulated cellular mRNA repertoire and its contribution to virus biology remains unknown. We show using polysome profiling that HCMV presides over the cellular translational landscape, selectively accessing the host genome to extend its own coding capacity and regulate virus replication. Expression of the HCMV UL38 mTORC1-activator partially recapitulates these translational alterations in uninfected cells. The signature of cellular mRNAs translationally-stimulated by HCMV resembles pathophysiological states where translation initiation factor levels or activity increase such as cancer. In contrast, cellular mRNAs repressed by HCMV include those involved in differentiation and the immune response. Surprisingly, interfering with the virus-induced activation of cellular mRNA translation can either limit or enhance HCMV growth. The unanticipated extent to which HCMV specifically manipulates host mRNA translation may aid in understanding its association with complex inflammatory disorders and cancer.

The herpes simplex virus (HSV) virion host shutoff (Vhs) protein is an endoribonuclease that accelerates decay of many host and viral mRNAs. Purified Vhs does not distinguish mRNAs from nonmessenger RNAs and cuts target RNAs at many sites, yet within infected cells it is targeted to mRNAs and cleaves those mRNAs at preferred sites including, for some, regions of translation initiation. This targeting may result in part from Vhs binding to the translation initiation factor eIF4H; in particular, several mutations in Vhs that abrogate its binding to eIF4H also abolish its mRNA-degradative activity, even though the mutant proteins retain endonuclease activity. To further investigate the role of eIF4H in Vhs activity, HeLa cells were depleted of eIF4H or other proteins by transfection with small interfering RNAs (siRNAs) 48 h prior to infection or mock infection in the presence of actinomycin D. Cellular mRNA levels were then assayed 5 h after infection. In cells transfected with an siRNA for the housekeeping enzyme glyceraldehyde-3-phosphate dehydrogenase, wild-type HSV infection reduced ␤-actin mRNA levels to between 20 and 30% of those in mock-infected cells, indicative of a normal Vhs activity. In contrast, in cells transfected with any of three eIF4H siRNAs, ␤-actin mRNA levels were indistinguishable in infected and mock-infected cells, suggesting that eIF4H depletion impeded Vhsmediated degradation. Depletion of the related factor eIF4B did not affect Vhs activity. The data suggest that eIF4H binding is required for Vhs-induced degradation of many mRNAs, perhaps by targeting Vhs to mRNAs and to preferred sites within mRNAs.The herpes simplex virus (HSV) virion host shutoff (Vhs) protein (UL41) is an endoribonuclease (9,14,83,84,87) that is a minor structural component of virions (57,58,67) and affects the half-lives of many host and viral mRNAs