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Nuclear interferon-inducible protein 16 promotes silencing of herpesviral and transfected DNA.

ABSTRACT: Mammalian cells have evolved mechanisms to silence foreign DNA introduced by viruses or by transfection. Upon herpesviral infection of cells, the viral genome is chromatinized in an attempt by the host cell to restrict expression of the viral genome. HSV ICP0 acts to counter host-intrinsic and innate responses to viral infection. We have found that nuclear interferon (IFN)-inducible protein 16 (IFI16) acts as a restriction factor against ICP0-null herpes simplex virus 1 (HSV-1) to limit viral replication and immediate-early gene expression. IFI16 promoted the addition of heterochromatin marks and the reduction of euchromatin marks on viral chromatin. IFI16 also restricted the expression of plasmid DNAs introduced by transfection but did not restrict SV40 DNA introduced into the cellular nucleus in the form of nucleosomal chromatin by viral infection. These results argue that IFI16 restricts unchromatinized DNA when it enters the cell nucleus by promoting the loading of nucleosomes and the addition of heterochromatin marks. Furthermore, these results indicate that IFI16 provides a broad surveillance role against viral and transfected DNA by promoting restriction of gene expression from the exogenous DNA and inducing innate immune responses.

SUBMITTER: Orzalli MH

PROVIDER: S-EPMC3839728 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Nuclear interferon-inducible protein 16 promotes silencing of herpesviral and transfected DNA.

Orzalli Megan H MH Conwell Sara E SE Berrios Christian C DeCaprio James A JA Knipe David M DM

Proceedings of the National Academy of Sciences of the United States of America 20131106 47

Mammalian cells have evolved mechanisms to silence foreign DNA introduced by viruses or by transfection. Upon herpesviral infection of cells, the viral genome is chromatinized in an attempt by the host cell to restrict expression of the viral genome. HSV ICP0 acts to counter host-intrinsic and innate responses to viral infection. We have found that nuclear interferon (IFN)-inducible protein 16 (IFI16) acts as a restriction factor against ICP0-null herpes simplex virus 1 (HSV-1) to limit viral re ...[more]

PMID: 24198334

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Project description:IFI16 (gamma-interferon-inducible protein 16), a predominantly nuclear protein involved in transcriptional regulation, also functions as an innate immune response DNA sensor and induces the IL-1? and antiviral type-1 interferon-? (IFN-?) cytokines. We have shown that IFI16, in association with BRCA1, functions as a sequence independent nuclear sensor of episomal dsDNA genomes of KSHV, EBV and HSV-1. Recognition of these herpesvirus genomes resulted in IFI16 acetylation, BRCA1-IFI16-ASC-procaspase-1 inflammasome formation, cytoplasmic translocation, and IL-1? generation. Acetylated IFI16 also interacted with cytoplasmic STING and induced IFN-?. However, the identity of IFI16 associated nuclear proteins involved in STING activation and the mechanism is not known. Mass spectrometry of proteins precipitated by anti-IFI16 antibodies from uninfected endothelial cell nuclear lysate revealed that histone H2B interacts with IFI16. Single and double proximity ligation microscopy, immunoprecipitation, EdU-genome labeled virus infection, and chromatin immunoprecipitation studies demonstrated that H2B is associated with IFI16 and BRCA1 in the nucleus in physiological conditions. De novo KSHV and HSV-1 infection as well as latent KSHV and EBV infection induces the cytoplasmic distribution of H2B-IFI16, H2B-BRCA1 and IFI16-ASC complexes. Vaccinia virus (dsDNA) cytoplasmic replication didn't induce the redistribution of nuclear H2B-IFI16 or H2B into the cytoplasm. H2B is critical in KSHV and HSV-1 genome recognition by IFI16 during de novo infection. Viral genome sensing by IFI16-H2B-BRCA1 leads to BRCA1 dependent recruitment of p300, and acetylation of H2B and IFI16. BRCA1 knockdown or inhibition of p300 abrogated the acetylation of H2B-IFI16 or H2B. Ran-GTP protein mediated the translocation of acetylated H2B and IFI16 to the cytoplasm along with BRCA1 that is independent of IFI16-ASC inflammasome. ASC knockdown didn't affect the acetylation of H2B, its cytoplasmic transportation, and the association of STING with IFI16 and H2B during KSHV infection. Absence of H2B didn't affect IFI16-ASC association and cytoplasmic distribution and thus demonstrating that IFI16-H2B complex is independent of IFI16-ASC-procaspase-1-inflammasome complex formed during infection. The H2B-IFI16-BRCA1 complex interacted with cGAS and STING in the cytoplasm leading to TBK1 and IRF3 phosphorylation, nuclear translocation of pIRF3 and IFN-? production. Silencing of H2B, cGAS and STING inhibited IFN-? induction but not IL-1? secretion, and cGAMP activity is significantly reduced by H2B and IFI16 knockdown during infection. Silencing of ASC inhibited IL-1? secretion but not IFN-? secretion during de novo KSHV and HSV-1 infection. These studies identify H2B as an innate nuclear sensor mediating a novel extra chromosomal function, and reveal that two IFI16 complexes mediate KSHV and HSV-1 genome recognition responses, with recognition by the IFI16-BRCA1-H2B complex resulting in IFN-? responses and recognition by IFI16-BRCA1 resulting in inflammasome responses.

Project description:To examine the association between anti-interferon-inducible protein 16 (anti-IFI-16) antibodies and clinical features of scleroderma.Sera from a discovery sample of 94 patients with scleroderma and 47 healthy controls were assayed for anti-IFI-16 antibodies by enzyme-linked immunosorbent assay, and associations were examined using regression analyses. Since anti-IFI-16 autoantibodies were found to be strongly associated with digital gangrene in the discovery sample, a subsequent case-control study (with subjects matched 1:1 on disease duration) was designed for further exploration. Cases were patients with scleroderma and digital gangrene, while controls were patients with scleroderma and Raynaud's phenomenon alone (n?=?39 matched pairs). Nonparametric, unadjusted matched pairs analysis as well as univariate and multivariable conditional logistic regression analyses were performed.In the discovery sample, anti-IFI-16 antibodies were more prevalent in patients with scleroderma than in healthy controls (18% versus 2%; P?=?0.01). Patients with anti-IFI-16 antibodies, compared to anti-IFI-16 antibody-negative patients, were more likely to have limited scleroderma (77% versus 46%; P?=?0.03), a longer disease duration (median 15.2 years [interquartile range 10.6-18.3] versus 6.0 years [interquartile range 3.4-13.8]; P < 0.01), digital gangrene (24% versus 4%; P?=?0.02), and a low diffusing capacity for carbon monoxide (DLco) (P < 0.01). In the case-control study, 35 (45%) of 78 patients were anti-IFI-16 antibody positive. Anti-IFI-16 antibody levels were significantly higher in cases with digital gangrene than in matched controls (P?=?0.02). In analyses adjusted for age, cutaneous scleroderma subtype, smoking, and DLco, high anti-IFI-16 antibody levels were associated with the presence of digital gangrene (adjusted odds ratio 2.3, 95% confidence interval 1.0-5.6, P?=?0.05). The odds of having digital gangrene increased with higher anti-IFI-16 antibody titers, in a dose-dependent manner.Anti-IFI-16 antibodies are associated with digital gangrene in patients with scleroderma. Longitudinal prospective studies exploring anti-IFI-16 antibodies as a disease biomarker, and biologic studies investigating the pathogenicity of these antibodies, are warranted.

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Nuclear interferon-inducible protein 16 promotes silencing of herpesviral and transfected DNA.

Publications

Nuclear interferon-inducible protein 16 promotes silencing of herpesviral and transfected DNA.

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