scholarly journals The Nuclear DNA Sensor IFI16 Acts as a Restriction Factor for Human Papillomavirus Replication through Epigenetic Modifications of the Viral Promoters

2015 ◽  
Vol 89 (15) ◽  
pp. 7506-7520 ◽  
Author(s):  
Irene Lo Cigno ◽  
Marco De Andrea ◽  
Cinzia Borgogna ◽  
Silvia Albertini ◽  
Manuela M. Landini ◽  
...  
Keyword(s):  
Gene Expression ◽  
Herpes Simplex ◽  
Viral Gene Expression ◽  
Restriction Factor ◽  
Viral Gene ◽  
Viral Dna ◽  
Herpes Simplex Virus 1 ◽  
Hpv Dna ◽  
U2os Cells ◽  
Simplex Virus

ABSTRACTThe human interferon-inducible IFI16 protein, an innate immune sensor of intracellular DNA, was recently demonstrated to act as a restriction factor for human cytomegalovirus (HCMV) and herpes simplex virus 1 (HSV-1) infection by inhibiting both viral-DNA replication and transcription. Through the use of two distinct cellular models, this study provides strong evidence in support of the notion that IFI16 can also restrict human papillomavirus 18 (HPV18) replication. In the first model, an immortalized keratinocyte cell line (NIKS) was used, in which the IFI16 protein was knocked down through the use of small interfering RNA (siRNA) technology and overexpressed following transduction with the adenovirus IFI16 (AdVIFI16) vector. The second model consisted of U2OS cells transfected by electroporation with HPV18 minicircles. In differentiated IFI16-silenced NIKS-HPV18 cells, viral-load values were significantly increased compared with differentiated control cells. Consistent with this, IFI16 overexpression severely impaired HPV18 replication in both NIKS and U2OS cells, thus confirming its antiviral restriction activity. In addition to the inhibition of viral replication, IFI16 was also able to reduce viral transcription, as demonstrated by viral-gene expression analysis in U2OS cells carrying episomal HPV18 minicircles and HeLa cells. We also provide evidence that IFI16 promotes the addition of heterochromatin marks and the reduction of euchromatin marks on viral chromatin at both early and late promoters, thus reducing both viral replication and transcription. Altogether, these results argue that IFI16 restricts chromatinized HPV DNA through epigenetic modifications and plays a broad surveillance role against viral DNA in the nucleus that is not restricted to herpesviruses.IMPORTANCEIntrinsic immunity is mediated by cellular restriction factors that are constitutively expressed and active even before a pathogen enters the cell. The host nuclear factor IFI16 acts as a sensor of foreign DNA and an antiviral restriction factor, as recently demonstrated by our group for human cytomegalovirus (HCMV) and herpes simplex virus 1 (HSV-1). Here, we provide the first evidence that IFI16 inhibits HPV18 replication by repressing viral-gene expression and replication. This antiviral restriction activity was observed in immortalized keratinocytes transfected with the religated genomes and in U2OS cells transfected with HPV18 minicircles, suggesting that it is not cell type specific. We also show that IFI16 promotes the assembly of heterochromatin on HPV DNA. These changes in viral chromatin structure lead to the generation of a repressive state at both early and late HPV18 promoters, thus implicating the protein in the epigenetic regulation of HPV gene expression and replication.

scholarly journals Viral DNA Sensors IFI16 and Cyclic GMP-AMP Synthase Possess Distinct Functions in Regulating Viral Gene Expression, Immune Defenses, and Apoptotic Responses during Herpesvirus Infection

mBio ◽  
2016 ◽  
Vol 7 (6) ◽  
Author(s):  
Benjamin A. Diner ◽  
Krystal K. Lum ◽  
Jared E. Toettcher ◽  
Ileana M. Cristea
Keyword(s):  
Gene Expression ◽  
Live Cell Imaging ◽  
Nuclear Periphery ◽  
Viral Gene Expression ◽  
Live Cell ◽  
Viral Gene ◽  
Viral Dna ◽  
Herpes Simplex Virus 1 ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACTThe human interferon-inducible protein IFI16 is an important antiviral factor that binds nuclear viral DNA and promotes antiviral responses. Here, we define IFI16 dynamics in space and time and its distinct functions from the DNA sensor cyclic dinucleotide GMP-AMP synthase (cGAS). Live-cell imaging reveals a multiphasic IFI16 redistribution, first to viral entry sites at the nuclear periphery and then to nucleoplasmic puncta upon herpes simplex virus 1 (HSV-1) and human cytomegalovirus (HCMV) infections. Optogenetics and live-cell microscopy establish the IFI16 pyrin domain as required for nuclear periphery localization and oligomerization. Furthermore, using proteomics, we define the signature protein interactions of the IFI16 pyrin and HIN200 domains and demonstrate the necessity of pyrin for IFI16 interactions with antiviral proteins PML and cGAS. We probe signaling pathways engaged by IFI16, cGAS, and PML using clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9-mediated knockouts in primary fibroblasts. While IFI16 induces cytokines, only cGAS activates STING/TBK-1/IRF3 and apoptotic responses upon HSV-1 and HCMV infections. cGAS-dependent apoptosis upon DNA stimulation requires both the enzymatic production of cyclic dinucleotides and STING. We show that IFI16, not cGAS or PML, represses HSV-1 gene expression, reducing virus titers. This indicates that regulation of viral gene expression may function as a greater barrier to viral replication than the induction of antiviral cytokines. Altogether, our findings establish coordinated and distinct antiviral functions for IFI16 and cGAS against herpesviruses.IMPORTANCEHow mammalian cells detect and respond to DNA viruses that replicate in the nucleus is poorly understood. Here, we decipher the distinct functions of two viral DNA sensors, IFI16 and cGAS, during active immune signaling upon infection with two herpesviruses, herpes simplex virus 1 (HSV-1) and human cytomegalovirus (HCMV). We show that IFI16 rapidly oligomerizes at incoming herpesvirus genomes at the nuclear periphery to transcriptionally repress viral gene expression and limit viral replicative capacity. We further demonstrate that IFI16 does not initiate upstream activation of the canonical STING/TBK-1/IRF3 signaling pathway but is required for downstream antiviral cytokine expression. In contrast, we find that, upon DNA sensing during herpesvirus infection, cGAS triggers apoptosis in a STING-dependent manner. Our live-cell imaging, mass spectrometry-based proteomics, CRISPR-based cellular assays, and optogenetics underscore the value of integrative approaches to uncover complex cellular responses against pathogens.

scholarly journals Regulation of viral gene expression by the herpes simplex virus 1 UL24 protein (HSV-1 UL24 inhibits accumulation of viral transcripts)

Virology ◽  
2016 ◽  
Vol 495 ◽  
pp. 148-160 ◽  
Author(s):  
Carolina Sanabria-Solano ◽  
Carmen Elena Gonzalez ◽  
Nicolas Richerioux ◽  
Luc Bertrand ◽  
Slimane Dridi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Viral Gene Expression ◽  
Viral Gene ◽  
Herpes Simplex Virus 1 ◽  
Simplex Virus ◽  
Hsv 1

scholarly journals Herpes Simplex Virus VP16, but Not ICP0, Is Required To Reduce Histone Occupancy and Enhance Histone Acetylation on Viral Genomes in U2OS Osteosarcoma Cells

2009 ◽  
Vol 84 (3) ◽  
pp. 1366-1375 ◽  
Author(s):  
Meaghan H. Hancock ◽  
Anna R. Cliffe ◽  
David M. Knipe ◽  
James R. Smiley
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Chromatin Structure ◽  
Viral Genome ◽  
Viral Gene Expression ◽  
Viral Gene ◽  
Osteosarcoma Cell ◽  
U2os Cells ◽  
Simplex Virus

ABSTRACT The herpes simplex virus (HSV) genome rapidly becomes associated with histones after injection into the host cell nucleus. The viral proteins ICP0 and VP16 are required for efficient viral gene expression and have been implicated in reducing the levels of underacetylated histones on the viral genome, raising the possibility that high levels of underacetylated histones inhibit viral gene expression. The U2OS osteosarcoma cell line is permissive for replication of ICP0 and VP16 mutants and appears to lack an innate antiviral repression mechanism present in other cell types. We therefore used chromatin immunoprecipitation to determine whether U2OS cells are competent to load histones onto HSV DNA and, if so, whether ICP0 and/or VP16 are required to reduce histone occupancy and enhance acetylation in this cell type. High levels of underacetylated histone H3 accumulated at several locations on the viral genome in the absence of VP16 activation function; in contrast, an ICP0 mutant displayed markedly reduced histone levels and enhanced acetylation, similar to wild-type HSV. These results demonstrate that U2OS cells are competent to load underacetylated histones onto HSV DNA and uncover an unexpected role for VP16 in modulating chromatin structure at viral early and late loci. One interpretation of these findings is that ICP0 and VP16 affect viral chromatin structure through separate pathways, and the pathway targeted by ICP0 is defective in U2OS cells. We also show that HSV infection results in decreased histone levels on some actively transcribed genes within the cellular genome, demonstrating that viral infection alters cellular chromatin structure.

scholarly journals Promoting Simultaneous Onset of Viral Gene Expression Among Cells Infected with Herpes Simplex Virus-1

2017 ◽  
Vol 8 ◽  
Author(s):  
Maya Ralph ◽  
Marina Bednarchik ◽  
Enosh Tomer ◽  
Dor Rafael ◽  
Sefi Zargarian ◽  
...  
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Viral Gene Expression ◽  
Viral Gene ◽  
Herpes Simplex Virus 1 ◽  
Simplex Virus

scholarly journals Herpes Simplex Virus 1 Immediate-Early and Early Gene Expression during Reactivation from Latency under Conditions That Prevent Infectious Virus Production

2005 ◽  
Vol 79 (23) ◽  
pp. 14516-14525 ◽  
Author(s):  
Jean M. Pesola ◽  
Jia Zhu ◽  
David M. Knipe ◽  
Donald M. Coen
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Infectious Virus ◽  
Cultured Cells ◽  
Viral Gene Expression ◽  
Immediate Early ◽  
Viral Gene ◽  
Viral Dna ◽  
Simplex Virus

ABSTRACT The program of gene expression exhibited by herpes simplex virus during productive infection of cultured cells is well established; however, less is known about the regulatory controls governing reactivation from latency in neurons. One difficulty in examining gene regulation during reactivation lies in distinguishing between events occurring in initial reactivating cells versus events occurring in secondarily infected cells. Thus, two inhibitors were employed to block production of infectious virus: acyclovir, which inhibits viral DNA synthesis, and WAY-150138, which permits viral DNA synthesis but inhibits viral DNA encapsidation. Latently infected murine ganglia were explanted in the presence of either inhibitor, and then amounts of RNA, DNA, or infectious virus were quantified. In ganglia explanted for 48 h, the levels of five immediate-early and early RNAs did not exhibit meaningful differences between acyclovir and WAY-150138 treatments when analyzed by in situ hybridization or quantitative reverse transcription-PCR. However, comparative increases in viral DNA and RNA content in untreated ganglia suggested that virus was produced before 48 h postexplant. This was confirmed by the detection of infectious virus as early as 14 h postexplant. Together, these results suggest that high levels of viral gene expression at 48 h postexplant are due largely to the production of infectious virus and subsequent spread through the tissue. These results lead to a reinterpretation of previous results indicating a role for DNA replication in immediate-early and early viral gene expression; however, it remains possible that viral gene expression is regulated differently in neurons than in cultured cells.

scholarly journals Herpes Simplex Virus Latency Is Noisier the Closer We Look

2019 ◽  
Vol 94 (4) ◽  
Author(s):  
Navneet Singh ◽  
David C. Tscharke
Keyword(s):  
Gene Expression ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Viral Genome ◽  
Infectious Virus ◽  
Viral Gene Expression ◽  
Viral Gene ◽  
Peripheral Neurons ◽  
Virus Latency ◽  
Simplex Virus

ABSTRACT During herpes simplex virus (HSV) latency, the viral genome is harbored in peripheral neurons in the absence of infectious virus but with the potential to restart infection. Advances in epigenetics have helped explain how viral gene expression is largely inhibited during latency. Paradoxically, at the same time, the view that latency is entirely silent has been eroding. This low-level noise has implications for our understanding of HSV latency and should not be ignored.

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