Olf-1, a Neuron-specific Transcription Factor, Can Activate the Herpes Simplex Virus Type 1-Infected Cell Protein 0 Promoter

Herpesviruses are characterized by the ability to establish lifelong latent infections and to reactivate periodically, leading to recurrent disease. The herpes simplex virus type 1 (HSV-1) genome is maintained in a quiescent state in sensory neurons during latency, which is characterized by the absence of detectable viral protein synthesis. Cellular factors induced by stress may act directly on promoters within the latent viral genome to induce the transcription of viral genes and trigger reactivation. In order to identify which viral promoters are induced by stress and elucidate the cellular mechanism responsible for the induction, we generated a panel of HSV-1 promoter-luciferase constructs and measured their response to heat shock. Of the promoters tested, those of ICP0 and ICP22 were the most strongly upregulated after heat shock. Herpes simplex virus type 1 (HSV-1) latency is characterized by the absence of viral replication, the absence of detectable viral proteins, and the presence of abundant nuclear latencyassociated transcripts (LATs) and limited amounts of ICP4 and thymidine kinase (TK) transcripts (14,25). Periodically, the virus is induced to reenter the lytic replication cycle, or reactivate, by a poorly characterized reactivation-inducing stimulus, such as physical or emotional stress, fever, or UV irradiation, among other stresses (47).The molecular mechanism of HSV-1 reactivation from latency remains one of the most clinically relevant, yet least well-characterized aspects of HSV-1 infection. We hypothesize that in the absence of detectable viral proteins in latently infected neurons, the reactivation-inducing stimulus likely acts on viral promoters to increase viral gene expression and, subsequently, viral replication. There is some evidence to suggest that the well-characterized temporal cascade of viral gene expression during lytic infection of immediate-early, early, delayed-early, and late (IE, E, DE, and L, respectively) may be altered during the initial events of reactivation in neurons (44). The results of reverse transcription-PCR (RT-PCR) of RNA from latently infected mouse TG induced to reactivate by explant demonstrated that E genes are transcribed before IE genes (44). This suggests that the gene expression cascade may be altered in reactivating TG compared to lytic replication in cell culture.ICP0 has been shown to play an important role in reactivation from latency. Studies have demonstrated that infection of quiescently infected cultures with adenoviruses expressing ICP0, but not ICP0, with a mutation in its RING finger domain led to the reactivation of both HSV-1 and HSV-2, suggesting that ICP0 activity is important for inducing reactivation (16,18). In addition, ICP0-null viruses were unable to reactivate in vivo after heat shock (46) and reactivated with reduced efficiency compared to wild-type virus from latently infected cultures in vitro (5, 17), indicating that ICP0 is a key player in reactivation. Taken together, these studies present considerable evidence of an important...

Section: Resultsmentioning

confidence: 63%

Role of Nuclear Factor Y in Stress-Induced Activation of the Herpes Simplex Virus Type 1 ICP0 Promoter

Kushnir

Davido

Schaffer

2010

“…The absence of labeling of these nonneuronal cells in any of the other transgenic mouse lines suggests that these two exceptions were anomalies. Some expression of the ICP0 promoter has been previously observed in nonneuronal cells in vitro (13,36,49). However, it is likely that transcriptional regulation of the ICP0 promoter in nonneuronal cells which have undergone multiplication and passage in vitro is different from regulation in the same cells in vivo.…”

Section: Discussionmentioning

confidence: 98%

Neurons Differentially Activate the Herpes Simplex Virus Type 1 Immediate-Early Gene ICP0 and ICP27 Promoters in Transgenic Mice

Loiacono

Myers

Mitchell

2002

Herpes simplex virus type 1 (HSV-1) immediate-early (IE) proteins are required for the expression of viral early and late proteins. It has been hypothesized that host neuronal proteins regulate expression of HSV-1 IE genes that in turn control viral latency and reactivation. We investigated the ability of neuronal proteins in vivo to activate HSV-1 IE gene promoters (ICP0 and ICP27) and a late gene promoter (gC). Transgenic mice containing IE (ICP0 and ICP27) and late (gC) gene promoters of HSV-1 fused to the Escherichia coli ␤-galactosidase coding sequence were generated. Expression of the ICP0 and ICP27 reporter transgenes was present in anatomically distinct subsets of neurons in the absence of viral proteins. The anatomic locations of ␤-galactosidase-positive neurons in the brains of ICP0 and ICP27 reporter transgenic mice were similar and included cerebral cortex, lateral septal nucleus, cingulum, hippocampus, thalamus, amygdala, and vestibular nucleus. Trigeminal ganglion neurons were positive for ␤-galactosidase in adult ICP0 and ICP27 reporter transgenic mice. The ICP0 reporter transgene was differentially regulated in trigeminal ganglion neurons depending upon age. ␤-Galactosidase-labeled cells in trigeminal ganglia and cerebral cortex of ICP0 and ICP27 reporter transgenic mice were confirmed as neurons by double labeling with antineurofilament antibody. Nearly all nonneuronal cells in ICP0 and ICP27 reporter transgenic mice and all neuronal and nonneuronal cells in gC reporter transgenic mice were negative for ␤-galactosidase labeling in the absence of HSV-1. We conclude that factors in neurons are able to differentially regulate the HSV-1 IE gene promoters (ICP0 and ICP27) in transgenic mice in the absence of viral proteins. These findings are important for understanding the regulation of the latent and reactivated stages of HSV-1 infection in neurons.Herpes simplex virus (HSV) causes significant disease in humans, including keratitis, conjunctivitis, encephalitis, and disseminated infections of the newborn (65). Lytic infection occurs initially at peripheral sites and is followed by axonal transport of HSV to sensory ganglion neurons. Neurons undergo either lytic or latent viral infection (59, 60). HSV type 1 (HSV-1) immediate-early (IE) genes are thought to be important in determining the outcome of infection (54). The level of IE gene expression may play a role in cell tropism, establishment of and reactivation from latency (19,21), and the extent of viral replication and disease. The HSV-1 IE ICP0 protein stimulates expression of early and late viral genes (6,16,17,18,22,23,39,48,67). ICP0 has been shown to initiate viral gene expression from a quiescent HSV-1 genome in cultured cells (25,26,29,66,68), and it appears to play a role in reactivation of the latent HSV-1 genome from sensory ganglion neurons in vivo (7,35).Many studies of the mechanism of IE gene regulation have been performed with cultured cells; however, little information exists about activation of the viral IE genes ICP0 and ICP27 ...

“…Transcription of ICP0 (as an IE gene) during lytic infection is induced by the interaction of viral and host proteins with a cis-acting promoter sequence known as a TAATGA RAT sequence (reviewed in reference 73). Several additional host cell-encoded transcription factors have been shown to affect basal IE gene promoter activity in transient transfection assays of cultures of various cell lines (13,32,34,40,46) (Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

Analysis of Herpes Simplex Virus ICP0 Promoter Function in Sensory Neurons during Acute Infection, Establishment of Latency, and Reactivation In Vivo

Thompson

Shieh

Sawtell

2003

Despite the extensive repression of herpes simplex virus type 1 (HSV-1) gene transcription during latency, a variety of stressful stimuli can result in the reactivation of the latent genome and reentry into lytic-phase transcription (71). How the quiescent genome exits latency is not yet known. It has been suggested that ICP0 is uniquely important for the initiation of viral reactivation (reviewed in reference 19). ICP0 is a major viral transcriptional activator important for the expression of viral genes of diverse kinetic classes (8-10, 12, 60). In addition, this protein functions to promote viral mRNA translation and regulates levels of cellular proteins through interaction with the ubiquitin-proteosome pathway (18,20,45,49). These properties suggest that ICP0 can regulate both viral and host protein levels through transcriptional, translational, and posttranslational mechanisms. In a tissue culture model of latent infection, ICP0 was implicated in the efficient establishment of latency (74). ICP0-expressing adenovirus vectors that lack all other HSV genes have been shown to induce viral replication in quiescently infected tissue cultures (28,75). Further, a viral mutant lacking functional ICP0 but containing all other viral genes did not induce viral replication in similar cultures, suggesting a specific role for ICP0 (28). However, adenovirus vectors expressing ICP4 and VP16 can also induce viral replication in primary cultures derived from latently infected ganglia (26).In animal models ICP0 mutant strains can establish latent infections and can reactivate in cocultivation assays, but the levels of efficiency for both of these processes are greatly reduced compared to that seen with the wild-type strain (7,10,27,33,37). One problem with these studies is that ICP0 null mutants establish latency inefficiently, and it is therefore difficult to distinguish between the importance of this gene for establishing latency and its importance for initiating reactivation. Recently, Halford and Schaffer infected immunosuppressed mice with ICP0 null mutants in an effort to increase the establishment of latency by the null mutants. Those authors concluded (on the basis of the total amount of HSV DNA detected in ganglia by PCR and the number of explant cultures * Corresponding author. Mailing address for Richard