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The intracellular DNA sensor IFI16 gene acts as restriction factor for human cytomegalovirus replication
- Source :
- PLoS Pathogens, Vol 8, Iss 1, p e1002498 (2012), PLoS Pathogens
- Publication Year :
- 2012
- Publisher :
- Public Library of Science (PLoS), 2012.
-
Abstract
- Human interferon (IFN)-inducible IFI16 protein, an innate immune sensor of intracellular DNA, modulates various cell functions, however, its role in regulating virus growth remains unresolved. Here, we adopt two approaches to investigate whether IFI16 exerts pro- and/or anti-viral actions. First, the IFI16 gene was silenced using specific small interfering RNAs (siRNA) in human embryo lung fibroblasts (HELF) and replication of DNA and RNA viruses evaluated. IFI16-knockdown resulted in enhanced replication of Herpesviruses, in particular, Human Cytomegalovirus (HCMV). Consistent with this, HELF transduction with a dominant negative form of IFI16 lacking the PYRIN domain (PYD) enhanced the replication of HCMV. Second, HCMV replication was compared between HELFs overexpressing either the IFI16 gene or the LacZ gene. IFI16 overexpression decreased both virus yield and viral DNA copy number. Early and late, but not immediate-early, mRNAs and proteins were strongly down-regulated, thus IFI16 may exert its antiviral effect by impairing viral DNA synthesis. Constructs with the luciferase reporter gene driven by deleted or site-specific mutated forms of the HCMV DNA polymerase (UL54) promoter demonstrated that the inverted repeat element 1 (IR-1), located between −54 and −43 relative to the transcription start site, is the target of IFI16 suppression. Indeed, electrophoretic mobility shift assays and chromatin immunoprecipitation demonstrated that suppression of the UL54 promoter is mediated by IFI16-induced blocking of Sp1-like factors. Consistent with these results, deletion of the putative Sp1 responsive element from the HCMV UL44 promoter also relieved IFI16 suppression. Together, these data implicate IFI16 as a novel restriction factor against HCMV replication and provide new insight into the physiological functions of the IFN-inducible gene IFI16 as a viral restriction factor.<br />Author Summary Only recently, intrinsic cellular-based defense mechanisms which give cells the capacity to resist pathogens have been discovered as an essential component of immunity. However, unlike the innate and adaptive branches of the immune system, intrinsic immune defenses are mediated by cellular restriction factors that are constitutively expressed and active even before a pathogen enters the cell. The protein family HIN-200 may act as sensors of foreign DNA and modulate various functions such as growth, apoptosis, and senescence. Here we show that, in the absence of functional IFI16, the replication of some Herpesviruses and in particular of Human Cytomegalovirus (HCMV) is significantly enhanced. Accordingly, IFI16 overexpression strongly inhibited HCMV replication. Accumulation of viral DNA copies was down-regulated along with expression of early and late viral gene expression suggesting that IFI16 inhibits viral DNA synthesis. Using transient transfection, luciferase, gel shift assay, and chromatin immunoprecipitation, we demonstrate that IFI16 suppresses the transcriptional activity of the viral DNA polymerase gene (UL54) and the UL44 gene, also required for viral DNA synthesis. The finding that the nuclear DNA sensor IFI16 controls virus growth represents an important step forward in understanding the intrinsic mechanisms that drive viral infections sustained by DNA viruses such as Herpesviruses.
- Subjects :
- Human cytomegalovirus
lcsh:Immunologic diseases. Allergy
Sp1 Transcription Factor
viruses
Immunology
Cytomegalovirus
DNA-Directed DNA Polymerase
Biology
Response Elements
Virus Replication
Microbiology
DNA replication factor CDT1
Mice
Viral Proteins
Replication factor C
Control of chromosome duplication
Virology
Chlorocebus aethiops
Molecular Cell Biology
Genetics
medicine
Animals
Humans
Vero Cells
Molecular Biology
Gene
lcsh:QH301-705.5
DNA replication
Nuclear Proteins
Fibroblasts
Embryo, Mammalian
Phosphoproteins
medicine.disease
Molecular biology
Immunity, Innate
HEK293 Cells
Infectious Diseases
Viral replication
lcsh:Biology (General)
Cytomegalovirus Infections
DNA, Viral
biology.protein
Medicine
Origin recognition complex
Parasitology
lcsh:RC581-607
Research Article
Subjects
Details
- Language :
- English
- ISSN :
- 15537374 and 15537366
- Volume :
- 8
- Issue :
- 1
- Database :
- OpenAIRE
- Journal :
- PLoS Pathogens
- Accession number :
- edsair.doi.dedup.....cac30508bb28191a4e779a4428f0faeb