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D.M. Neumann, D.T. Stark, V. Kodi, A.M. Azcuy, H.W. Thompson, D.C. Bloom, J.M. Hill; Assessment of the Association of Acetyl–Histone 3 to the HSV–1 Genes During Latency and Induced Ocular Reactivation . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2800.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To determine the status of acetyl H3 binding to viral and host genes using the trigeminal ganglia (TG) of mice latent with HSV–1. Histones can be modified post–transcriptionally by numerous mechanisms, and histone acetylation can be a marker for transcriptional permissiveness. These experiments will serve as standards for our comparison of the status of acetyl H3 binding to viral and host genes prior to and during induced HSV–1 reactivation. Methods: Female BALB/c mice were inoculated with HSV–1 onto scarified corneas. After viral latency was established (post inoculation day 28), mice were either sacrificed for ChIP assays of latent TGs or injected i.p. with 1.2 g/kg of sodium butyrate (a known histone deacetylase inhibitor). ChIP assays and quantitative PCR were performed to assess relative acetyl H3 enrichment of the LAT promoter and lytic viral genes, such as DNA polymerase. Validation of the ChIP assay was done utilizing real time PCR to quantitate the fold enrichment of acetyl H3 of mouse host genes. Results: Through validation of the ChIP assay, we have shown that enrichment of acetyl H3 in the mouse host gene Xist (euchromatic) is 200–fold greater than that of the host gene beta globin (heterochromatic). There was 10–fold greater enrichment of acetyl H3 in the LAT promoter region of HSV–1 during latency compared to HSV–1 DNA polymerase. We also found increased acetyl H3 enrichment of HSV–1 DNA polymerase compared to that of the LAT promoter region during butyrate–induced ocular reactivation. Butyrate treatment resulted in ocular shedding of infectious virus in the tear film of 95% of the eyes tested and the detection of infectious virus in 100% of the TGs evaluated in the HSV–1 latent mice. Conclusions: Sodium butyrate induced ocular HSV–1 reactivation in mice. We found a 10:1 ratio of acetyl H3 associated with the LAT promoter vs. acetyl H3 associated with HSV–1 DNA polymerase in mice latent with HSV–1. During reactivation, this ratio approached 1:1. These findings will be the basis for future studies of the epigenetic mechanisms involved in viral latency and neuronal reactivation.
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