scholarly journals The CCCTC Binding Factor, CTRL2, Modulates Heterochromatin Deposition and the Establishment of Herpes Simplex Virus 1 Latency In Vivo

2019 ◽  
Vol 93 (13) ◽  
Author(s):  
Shannan D. Washington ◽  
Pankaj Singh ◽  
Richard N. Johns ◽  
Terri G. Edwards ◽  
Michael Mariani ◽  
...  
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Transcriptional Control ◽  
Neuronal Cell ◽  
Ocular Infection ◽  
Herpes Simplex Virus 1 ◽  
Lytic Gene ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACT The cellular insulator protein CTCF plays a role in herpes simplex virus 1 (HSV-1) latency through the establishment and regulation of chromatin boundaries. We previously found that the CTRL2 regulatory element downstream from the latency-associated transcript (LAT) enhancer was bound by CTCF during latency and underwent CTCF eviction at early times postreactivation in mice latently infected with 17syn+ virus. We also showed that CTRL2 was a functional enhancer-blocking insulator in both epithelial and neuronal cell lines. We hypothesized that CTRL2 played a direct role in silencing lytic gene expression during the establishment of HSV-1 latency. To test this hypothesis, we used a recombinant virus with a 135-bp deletion spanning only the core CTRL2 insulator domain (ΔCTRL2) in the 17syn+ background. Deletion of CTRL2 resulted in restricted viral replication in epithelial cells but not neuronal cells. Following ocular infection, mouse survival decreased in the ΔCTRL2-infected cohort, and we found a significant decrease in the number of viral genomes in mouse trigeminal ganglia (TG) infected with ΔCTRL2, indicating that the CTRL2 insulator was required for the efficient establishment of latency. Immediate early (IE) gene expression significantly increased in the number of ganglia infected with ΔCTRL2 by 31 days postinfection relative to the level with 17syn+ infection, indicating that deletion of the CTRL2 insulator disrupted the organization of chromatin domains during HSV-1 latency. Finally, chromatin immunoprecipitation with high-throughput sequencing (ChIP-seq) analyses of TG from ΔCTRL2-infected mice confirmed that the distribution of the repressive H3K27me3 (histone H3 trimethylated at K27) mark on the ΔCTRL2 recombinant genomes was altered compared to that of the wild type, indicating that the CTRL2 site modulates the repression of IE genes during latency. IMPORTANCE It is becoming increasingly clear that chromatin insulators play a key role in the transcriptional control of DNA viruses. The gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi’s sarcoma-associated herpesvirus (KSHV) utilize chromatin insulators to order protein recruitment and dictate the formation of three-dimensional DNA loops that spatially control transcription and latency. The contribution of chromatin insulators in alphaherpesvirus transcriptional control is less well understood. The work presented here begins to bridge that gap in knowledge by showing how one insulator site in HSV-1 modulates lytic gene transcription and heterochromatin deposition as the HSV-1 genome establishes latency.

scholarly journals Mutations Inactivating Herpes Simplex Virus 1 MicroRNA miR-H2 Do Not Detectably Increase ICP0 Gene Expression in Infected Cultured Cells or Mouse Trigeminal Ganglia

2016 ◽  
Vol 91 (2) ◽  
Author(s):  
Dongli Pan ◽  
Jean M. Pesola ◽  
Gang Li ◽  
Seamus McCarron ◽  
Donald M. Coen
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Trigeminal Ganglia ◽  
Herpes Simplex Virus 1 ◽  
Lytic Gene ◽  
Lytic Gene Expression ◽  
Latently Infected ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACT Herpes simplex virus 1 (HSV-1) latency entails the repression of productive (“lytic”) gene expression. An attractive hypothesis to explain some of this repression involves inhibition of the expression of ICP0, a lytic gene activator, by a viral microRNA, miR-H2, which is completely complementary to ICP0 mRNA. To test this hypothesis, we engineered mutations that disrupt miR-H2 without affecting ICP0 in HSV-1. The mutant virus exhibited drastically reduced expression of miR-H2 but showed wild-type levels of infectious virus production and no increase in ICP0 expression in lytically infected cells, which is consistent with the weak expression of miR-H2 relative to the level of ICP0 mRNA in that setting. Following corneal inoculation of mice, the mutant was not significantly different from wild-type virus in terms of infectious virus production in the trigeminal ganglia during acute infection, mouse mortality, or the rate of reactivation from explanted latently infected ganglia. Critically, the mutant was indistinguishable from wild-type virus for the expression of ICP0 and other lytic genes in acutely and latently infected mouse trigeminal ganglia. The latter result may be related to miR-H2 being less effective in inhibiting ICP0 expression in transfection assays than a host microRNA, miR-138, which has previously been shown to inhibit lytic gene expression in infected ganglia by targeting ICP0 mRNA. Additionally, transfected miR-138 reduced lytic gene expression in infected cells more effectively than miR-H2. While this study provides little support for the hypothesis that miR-H2 promotes latency by inhibiting ICP0 expression, the possibility remains that miR-H2 might target other genes during latency. IMPORTANCE Herpes simplex virus 1 (HSV-1), which causes a variety of diseases, can establish lifelong latent infections from which virus can reactivate to cause recurrent disease. Latency is the most biologically interesting and clinically vexing feature of the virus. Ever since miR-H2's discovery as a viral microRNA bearing complete sequence complementarity to the mRNA for the important viral gene activator ICP0, inhibition of ICP0 expression by miR-H2 has been a major hypothesis to help explain the repression of lytic gene expression during latency. However, this hypothesis remained untested in latently infected animals. Using a miR-H2-deficient mutant virus, we found no evidence that miR-H2 represses the expression of ICP0 or other lytic genes in cells or mice infected with HSV-1. Although miR-H2 can repress ICP0 expression in transfection assays, such repression is weak. The results suggest that other mechanisms for miR-H2 activity and for the repression of lytic gene expression during latency deserve investigation.

scholarly journals Cohesin subunit Rad21 binds to the HSV-1 genome near CTCF insulator sites during latency in vivo

2021 ◽  
Author(s):  
Pankaj Singh ◽  
Donna M. Neumann
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Transcriptional Control ◽  
Spatial Proximity ◽  
Viral Transcription ◽  
Cohesin Complex ◽  
Herpes Simplex Virus 1 ◽  
Cohesin Subunit ◽  
Simplex Virus ◽  
Hsv 1

Herpes Simplex Virus 1 (HSV-1) is a human pathogen that has the ability to establish a lifelong infection in the host. During latency, HSV-1 genomes are chromatinized and are abundantly associated with histones in sensory neurons, yet the mechanisms that govern the latent-lytic transition remain unclear. We hypothesize that the latent-lytic switch is controlled by CTCF insulators, positioned within the HSV-1 latent genome. CTCF insulators, together with the cohesin complex, have the ability to establish and maintain chromtin loops that allow distance separated gene regions to be spatially oriented for transcriptional control. In this current study, we demonstrated that the cohesin subunit Rad21 was recruited to latent HSV-1 genomes near four of the CTCF insulators during latency. We showed that the CTCF insulator known as CTRS1/2, positioned downstream from the essential transactivating IE region of ICP4 was only enriched in Rad21 prior to but not during latency, suggesting that the CTRS1/2 insulator is not required for the maintenance of latency. Further, deletion of the CTRL2 insulator, positioned downstream from the LAT enhancer, resulted in a loss of Rad21 enrichment at insulators flanking the ICP4 region at early times post-infection in mice ganglia, suggesting that these insulators are interdependent. Finally, deletion of the CTRL2 insulator resulted in a loss of Rad21 enrichment at the CTRL2 insulator in a cell-type specific manner, and this loss of Rad21 enrichment was correlated to decreased LAT expression, suggesting that Rad21 recruitment to viral genomes is important for efficient gene expression. Importance CTCF insulators are important for transcriptional control and increasing evidence suggests that that CTCF insulators, together with the cohesin complex, regulate viral transcription in DNA viruses. The CTCF-cohesin interaction is important for the formation of chromatin loops, structures that orient distance separated elements in close spatial proximity for transcriptional control. Herpes Simplex Virus 1 (HSV-1) has seven putative CTCF insulators that flank the LAT and the IE, indicating that CTCF insulators play a role in the transition from latency to reactivation. Contributions from the work presented here include the finding that CTCF insulators in HSV-1 genomes are differentially enriched in the cohesin subunit Rad21, suggesting that CTCF-cohesin interactions could be establishing and anchoring chromatin loop structures to control viral transcription.

scholarly journals Herpes Simplex Virus 1 Strains 17syn+ and KOS(M) Differ Greatly in Their Ability To Reactivate from Human Neurons In Vitro

2020 ◽  
Vol 94 (15) ◽  
Author(s):  
Tristan R. Grams ◽  
Terri G. Edwards ◽  
David C. Bloom
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Latent Infection ◽  
Neuronal Cell ◽  
Herpes Simplex Virus 1 ◽  
Viral Genomes ◽  
Human Neuronal Cell ◽  
Cell Line Model ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACT Herpes simplex virus 1 (HSV-1) establishes a lifelong latent infection in peripheral nerve ganglia. Periodically, the virus reactivates from this latent reservoir and is transported to the original site of infection. Strains of HSV-1 have been noted to vary greatly in their virulence and reactivation efficiencies in animal models. While HSV-1 strain 17syn+ can be readily reactivated, strain KOS(M) shows little to no reactivation in the mouse and rabbit models of induced reactivation. Additionally, 17syn+ is markedly more virulent in vivo than KOS. This has raised questions regarding potential strain-specific differences in neuroinvasion and neurovirulence and their contribution to differences in the establishment of latency (or ability to spread back to the periphery) and to the reactivation phenotype. To determine if any difference in the ability to reactivate between strains 17syn+ and KOS(M) is manifest at the level of neurons, we utilized a recently characterized human neuronal cell line model of HSV latency and reactivation (LUHMES). We found that KOS(M) established latency with a higher number of viral genomes than strain 17syn+. Strikingly, we show that the KOS(M) viral genomes have a higher burden of heterochromatin marks than strain 17syn+. The increased heterochromatin profile for KOS(M) correlates with the reduced expression of viral lytic transcripts during latency and impaired induced reactivation compared to that of 17syn+. These results suggest that genomes entering neurons from HSV-1 infections with strain KOS(M) are more prone to rapid heterochromatinization than those of 17syn+ and that this results in a reduced ability to reactivate from latency. IMPORTANCE Herpes simplex virus 1 (HSV-1) establishes a lifelong infection in neuronal cells. The virus periodically reactivates and causes recurrent disease. Strains of HSV-1 vary greatly in their virulence and potential to reactivate in animal models. Although these differences are phenotypically well defined, factors contributing to the strains’ abilities to reactivate are largely unknown. We utilized a human neuronal cell line model of HSV latency and reactivation (LUHMES) to characterize the latent infection of two HSV-1 wild-type strains. We find that strain-specific differences in reactivation are recapitulated in LUHMES. Additionally, these differences correlate with the degree of heterochromatinization of the latent genomes. Our data suggest that the epigenetic state of the viral genome is an important determinant of reactivation that varies in a strain-specific manner. This work also shows the first evidence of strain-specific differences in reactivation outside the context of the whole animal at a human neuronal cell level.

scholarly journals A Herpes Simplex Virus 1 (McKrae) Mutant Lacking the Glycoprotein K Gene Is Unable To Infect via Neuronal Axons and Egress from Neuronal Cell Bodies

mBio ◽  
2012 ◽  
Vol 3 (4) ◽  
Author(s):  
Andrew T. David ◽  
Ahmad Saied ◽  
Anu Charles ◽  
Ramesh Subramanian ◽  
Vladimir N. Chouljenko ◽  
...  
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Recombinant Virus ◽  
Neuronal Cell ◽  
Viral Envelope ◽  
Viral Glycoprotein ◽  
Herpes Simplex Virus 1 ◽  
Neuronal Cell Bodies ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACTWe have shown that the herpes simplex virus 1 (HSV-1) gK gene is essential for efficient replication and spread in the corneal epithelium and trigeminal ganglion neuroinvasion in mice (A. T. David, A. Baghian, T. P. Foster, V. N. Chouljenko, and K. G. Kousoulas, Curr. Eye Res. 33:455–467, 2008). To further investigate the role of gK in neuronal infection, we utilized a microfluidic chamber system separating neuronal cell bodies and axonal termini. HSV-1 (McKrae) engineered virus constitutively expressing enhanced green fluorescence protein (GFP) was efficiently transmitted in both a retrograde and an anterograde manner. These results were corroborated by expression of virion structural proteins in either chamber, as well as detection of viral genomes and infectious viruses. In contrast, efficient infection of either chamber with a gK-null virus did not result in infection of the apposed chamber. These results show that gK is an important determinant in virion axonal infection. Moreover, the inability of the gK-null virus to be transmitted in an anterograde manner suggests that virions acquire cytoplasmic envelopes prior to entering axons.IMPORTANCEHerpes simplex virus 1 (HSV-1) enters mucosal epithelial cells and neurons via fusion of the viral envelope with cellular membranes, mediated by viral glycoprotein B (gB) in cooperation with other viral glycoproteins. Retrograde transport of virions to neuronal cell bodies (somata) establishes lifelong latent infection in ganglionic neurons. We have previously reported that gK binds gB and is required for gB-mediated membrane fusion (Jambunatathan et al., J. Virol. 85:12910–12918, 2011; V. N. Chouljenko, A. V. Iyer, S. Chowdhury, J. Kim, and K. G. Kousoulas, J. Virol. 84:8596–8606, 2010). In the current study, we constructed a recombinant virus with the gK gene deleted in the highly virulent ocular HSV-1 strain McKrae. This recombinant virus failed to infect rat ganglionic neuronal axons alone or cocultured with Vero cells in microfluidic chambers. In addition, lack of gK expression prevented anterograde transmission of virions. These results suggest that gK is a critical determinant for neuronal infection and transmission.

scholarly journals Herpes Simplex Virus 1 Reactivates from Autonomic Ciliary Ganglia Independently from Sensory Trigeminal Ganglia To Cause Recurrent Ocular Disease

2015 ◽  
Vol 89 (16) ◽  
pp. 8383-8391 ◽  
Author(s):  
Sungseok Lee ◽  
Angela M. Ives ◽  
Andrea S. Bertke
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Recurrent Disease ◽  
Clinical Disease ◽  
Ocular Infection ◽  
Sensory Ganglia ◽  
Autonomic Ganglia ◽  
Herpes Simplex Virus 1 ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACTHerpes simplex virus 1 (HSV-1) and HSV-2 establish latency in sensory and autonomic neurons after ocular or genital infection, but their recurrence patterns differ. HSV-1 reactivates from latency to cause recurrent orofacial disease, and while HSV-1 also causes genital lesions, HSV-2 recurs more efficiently in the genital region and rarely causes ocular disease. The mechanisms regulating these anatomical preferences are unclear. To determine whether differences in latent infection and reactivation in autonomic ganglia contribute to differences in HSV-1 and HSV-2 anatomical preferences for recurrent disease, we compared HSV-1 and HSV-2 clinical disease, acute and latent viral loads, and viral gene expression in sensory trigeminal and autonomic superior cervical and ciliary ganglia in a guinea pig ocular infection model. HSV-2 produced more severe acute disease, correlating with higher viral DNA loads in sensory and autonomic ganglia, as well as higher levels of thymidine kinase expression, a marker of productive infection, in autonomic ganglia. HSV-1 reactivated in ciliary ganglia, independently from trigeminal ganglia, to cause more frequent recurrent symptoms, while HSV-2 replicated simultaneously in autonomic and sensory ganglia to cause more persistent disease. While both HSV-1 and HSV-2 expressed the latency-associated transcript (LAT) in the trigeminal and superior cervical ganglia, only HSV-1 expressed LAT in ciliary ganglia, suggesting that HSV-2 is not reactivation competent or does not fully establish latency in ciliary ganglia. Thus, differences in replication and viral gene expression in autonomic ganglia may contribute to differences in HSV-1 and HSV-2 acute and recurrent clinical disease.IMPORTANCEHerpes simplex virus 1 (HSV-1) and HSV-2 establish latent infections, from which the viruses reactivate to cause recurrent disease throughout the life of the host. However, the viruses exhibit different manifestations and frequencies of recurrent disease. HSV-1 and HSV-2 establish latency in both sensory and autonomic ganglia. Autonomic ganglia are more responsive than sensory ganglia to stimuli associated with recurrent disease in humans, such as stress and hormone fluctuations, suggesting that autonomic ganglia may play an important role in recurrent disease. We show that HSV-1 can reactivate from autonomic ganglia, independently from sensory ganglia, to cause recurrent ocular disease. We found no evidence that HSV-2 could reactivate from autonomic ganglia independently from sensory ganglia after ocular infection, but HSV-2 did replicate in both ganglia simultaneously to cause persistent disease. Thus, viral replication and reactivation in autonomic ganglia contribute to different clinical disease manifestations of HSV-1 and HSV-2 after ocular infection.

scholarly journals Herpes Simplex Virus 1 and 2 Infections during Differentiation of Human Cortical Neurons

Viruses ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 2072
Author(s):  
Petra Bergström ◽  
Edward Trybala ◽  
Charlotta E. Eriksson ◽  
Maria Johansson ◽  
Tugce Munise Satir ◽  
...  
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Rna Polymerase Ii ◽  
Cortical Neurons ◽  
Fold Increase ◽  
Synaptic Activity ◽  
Herpes Simplex Virus 1 ◽  
Simplex Virus ◽  
Hsv 1

Herpes simplex virus 1 (HSV-1) and 2 (HSV-2) can infect the central nervous system (CNS) with dire consequences; in children and adults, HSV-1 may cause focal encephalitis, while HSV-2 causes meningitis. In neonates, both viruses can cause severe, disseminated CNS infections with high mortality rates. Here, we differentiated human induced pluripotent stem cells (iPSCs) towards cortical neurons for infection with clinical CNS strains of HSV-1 or HSV-2. Progenies from both viruses were produced at equal quantities in iPSCs, neuroprogenitors and cortical neurons. HSV-1 and HSV-2 decreased viability of neuroprogenitors by 36.0% and 57.6% (p < 0.0001), respectively, 48 h post-infection, while cortical neurons were resilient to infection by both viruses. However, in these functional neurons, both HSV-1 and HSV-2 decreased gene expression of two markers of synaptic activity, CAMK2B and ARC, and affected synaptic activity negatively in multielectrode array experiments. However, unaltered secretion levels of the neurodegeneration markers tau and NfL suggested intact axonal integrity. Viral replication of both viruses was found after six days, coinciding with 6-fold and 22-fold increase in gene expression of cellular RNA polymerase II by HSV-1 and HSV-2, respectively. Our results suggest a resilience of human cortical neurons relative to the replication of HSV-1 and HSV-2.

scholarly journals CCCTC-Binding Factor Acts as a Heterochromatin Barrier on Herpes Simplex Viral Latent Chromatin and Contributes to Poised Latent Infection

mBio ◽  
2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Jennifer S. Lee ◽  
Priya Raja ◽  
Dongli Pan ◽  
Jean M. Pesola ◽  
Donald M. Coen ◽  
...  
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Binding Sites ◽  
Latent Infection ◽  
Ctcf Binding ◽  
Herpes Simplex Virus 1 ◽  
Binding Factor ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACTHerpes simplex virus 1 (HSV-1) establishes latent infection in neurons via a variety of epigenetic mechanisms that silence its genome. The cellular CCCTC-binding factor (CTCF) functions as a mediator of transcriptional control and chromatin organization and has binding sites in the HSV-1 genome. We constructed an HSV-1 deletion mutant that lacked a pair of CTCF-binding sites (CTRL2) within the latency-associated transcript (LAT) coding sequences and found that loss of these CTCF-binding sites did not alter lytic replication or levels of establishment of latent infection, but their deletion reduced the ability of the virus to reactivate from latent infection. We also observed increased heterochromatin modifications on viral chromatin over theLATpromoter and intron. We therefore propose that CTCF binding at theCTRL2sites acts as a chromatin insulator to keep viral chromatin in a form that is poised for reactivation, a state which we call poised latency.IMPORTANCEHerpes simplex virus 1 (HSV-1) is a human pathogen that persists for the lifetime of the host as a result of its ability to establish latent infection within sensory neurons. The mechanism by which HSV-1 transitions from the lytic to latent infection program is largely unknown; however, HSV-1 is able to coopt cellular silencing mechanisms to facilitate the suppression of lytic gene expression. Here, we demonstrate that the cellular CCCTC-binding factor (CTCF)-binding site within the latency associated transcript (LAT) region is critical for the maintenance of a specific local chromatin structure. Additionally, loss of CTCF binding has detrimental effects on the ability to reactivate from latent infection. These results argue that CTCF plays a critical role in epigenetic regulation of viral gene expression to establish and/or maintain a form of latent infection that can reactivate efficiently.

scholarly journals Gene expression profiling of monocytes displaying herpes simplex virus 1 induced dysregulation of antifungal defences

2009 ◽  
Vol 58 (10) ◽  
pp. 1283-1290 ◽  
Author(s):  
Claudio Cermelli ◽  
Carlotta Francesca Orsi ◽  
Alessandro Cuoghi ◽  
Andrea Ardizzoni ◽  
Enrico Tagliafico ◽  
...  
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Functional Data ◽  
Macrophage Activation ◽  
Molecular Mechanisms ◽  
Herpes Simplex Virus 1 ◽  
Fungal Adhesion ◽  
Simplex Virus ◽  
Hsv 1

Recently, we showed that herpes simplex virus 1 (HSV-1)-infected monocytes have altered antifungal defences, in particular they show augmented phagocytosis of Candida albicans followed by a failure of the intracellular killing of the ingested fungi. On the basis of these functional data, comparative studies were carried out on the gene expression profile of cells infected with HSV-1 and/or C. albicans in order to investigate the molecular mechanisms underlying such virus-induced dysfunction. Affymetrix GeneChip technology was used to evaluate the cell transcription pattern, focusing on genes involved in phagocytosis, fungal adhesion, antimicrobial activity and apoptosis. The results indicated there was: (a) prevalent inhibition of opsonin-mediated phagocytosis, (b) upregulation of several pathways of antibody- and complement-independent phagocytosis, (c) inhibition of macrophage activation, (d) marked dysregulation of oxidative burst, (e) induction of apoptosis.

scholarly journals The Polycomb Group Protein Bmi1 Binds to the Herpes Simplex Virus 1 Latent Genome and Maintains Repressive Histone Marks during Latency

2009 ◽  
Vol 83 (16) ◽  
pp. 8173-8181 ◽  
Author(s):  
Dacia L. Kwiatkowski ◽  
Hilary W. Thompson ◽  
David C. Bloom
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Transcriptional Control ◽  
Polycomb Group ◽  
Polycomb Group Protein ◽  
Herpes Simplex Virus 1 ◽  
Group Protein ◽  
Simplex Virus ◽  
Lytic Genes ◽  
Hsv 1

ABSTRACT The mechanism by which herpes simplex virus 1 (HSV-1) establishes latency in sensory neurons is largely unknown. Recent studies indicate that epigenetic modifications of the chromatin associated with the latent genome may play a key role in the transcriptional control of lytic genes during latency. In this study, we found both constitutive and facultative types of heterochromatin to be present on the latent HSV-1 genome. Deposition of the facultative marks trimethyl H3K27 and histone variant macroH2A varied at different sites on the genome, whereas the constitutive marker trimethyl H3K9 did not. In addition, we show that in the absence of the latency-associated transcript (LAT), the latent genome shows a dramatic increase in trimethyl H3K27, suggesting that expression of the LAT during latency may act to promote an appropriate heterochromatic state that represses lytic genes but is still poised for reactivation. Due to the presence of the mark trimethyl H3K27, we examined whether Polycomb group proteins, which methylate H3K27, were present on the HSV-1 genome during latency. Our data indicate that Bmi1, a member of the Polycomb repressive complex 1 (PRC1) maintenance complex, associates with specific sites in the genome, with the highest level of enrichment at the LAT enhancer. To our knowledge, these are the first data demonstrating that a virus can repress its gene transcription to enter latency by exploiting the mechanism of Polycomb-mediated repression.

scholarly journals Prediction and Identification of Herpes Simplex Virus 1-Encoded MicroRNAs

2006 ◽  
Vol 80 (11) ◽  
pp. 5499-5508 ◽  
Author(s):  
Can Cui ◽  
Anthony Griffiths ◽  
Guanglin Li ◽  
Lindsey M. Silva ◽  
Martha F. Kramer ◽  
...  
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Blot Hybridization ◽  
Computational Method ◽  
Northern Blot Hybridization ◽  
Mirna Candidate ◽  
Herpes Simplex Virus 1 ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACT MicroRNAs (miRNAs) are key regulators of gene expression in higher eukaryotes. Recently, miRNAs have been identified from viruses with double-stranded DNA genomes. To attempt to identify miRNAs encoded by herpes simplex virus 1 (HSV-1), we applied a computational method to screen the complete genome of HSV-1 for sequences that adopt an extended stem-loop structure and display a pattern of nucleotide divergence characteristic of known miRNAs. Using this method, we identified 11 HSV-1 genomic loci predicted to encode 13 miRNA precursors and 24 miRNA candidates. Eight of the HSV-1 miRNA candidates were predicted to be conserved in HSV-2. The precursor and the mature form of one HSV-1 miRNA candidate, which is encoded ∼450 bp upstream of the transcription start site of the latency-associated transcript (LAT), were detected during infection of Vero cells by Northern blot hybridization. These RNAs, which behave as late gene products, are not predicted to be conserved in HSV-2. Additionally, small RNAs, including some that are roughly the expected size of precursor miRNAs, were detected using probes for miRNA candidates derived from sequences encoding the 8.3-kilobase LAT, from sequences complementary to UL 15 mRNA, and from the region between ICP4 and US 1. However, no species the size of typical mature miRNAs were detected using these probes. Three of these latter miRNA candidates were predicted to be conserved in HSV-2. Thus, HSV-1 encodes at least one miRNA. We hypothesize that HSV-1 miRNAs regulate viral and host gene expression.

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