Parvovirus B19 DNA CpG Dinucleotide Methylation and Epigenetic Regulation of Viral Expression

Francesca Bonvicini,Luisa De Falco,Elisabetta Manaresi,Giorgio Gallinella,Francesca Di Furio,Alison J Sinclair

doi:10.1371/journal.pone.0033316

Abstract

CpG DNA methylation is one of the main epigenetic modifications playing a role in the control of gene expression. For DNA viruses whose genome has the ability to integrate in the host genome or to maintain as a latent episome, a correlation has been found between the extent of DNA methylation and viral quiescence. No information is available for Parvovirus B19, a human pathogenic virus, which is capable of both lytic and persistent infections. Within Parvovirus B19 genome, the inverted terminal regions display all the characteristic signatures of a genomic CpG island; therefore we hypothesised a role of CpG dinucleotide methylation in the regulation of viral genome expression.The analysis of CpG dinucleotide methylation of Parvovirus B19 DNA was carried out by an aptly designed quantitative real-time PCR assay on bisulfite-modified DNA. The effects of CpG methylation on the regulation of viral genome expression were first investigated by transfection of either unmethylated or in vitro methylated viral DNA in a model cell line, showing that methylation of viral DNA was correlated to lower expression levels of the viral genome. Then, in the course of in vitro infections in different cellular environments, it was observed that absence of viral expression and genome replication were both correlated to increasing levels of CpG methylation of viral DNA. Finally, the presence of CpG methylation was documented in viral DNA present in bioptic samples, indicating the occurrence and a possible role of this epigenetic modification in the course of natural infections.The presence of an epigenetic level of regulation of viral genome expression, possibly correlated to the silencing of the viral genome and contributing to the maintenance of the virus in tissues, can be relevant to the balance and outcome of the different types of infection associated to Parvovirus B19.

Highlights

Parvovirus B19 (B19V) is a human pathogenic virus, member of the Erythrovirus genus in the Parvoviridae family [1]
Parvovirus B19 genome and CpG islands As a basis for investigation, Parvovirus B19 genome sequence was inspected for the presence and distribution of CpG dinucleotides by means of EMBOSS CpGPlot, a web-based program available at EMBL-EBI
The role of epigenetic modifications, in particular CpG methylation, in the genome of DNA viruses has been the subject of studies concerning large DNA viruses, whose genome has the ability to integrate in the host genome or to maintain itself as a latent episome, and can directly or indirectly be associated with the establishment of tumorigenic processes [35]

Summary

Introduction

Parvovirus B19 (B19V) is a human pathogenic virus, member of the Erythrovirus genus in the Parvoviridae family [1]. The virus shows a selective tropism for erythroid progenitor cells in the bone marrow, exerting a cytotoxic effect and causing a block in erythropoiesis that can manifest as transient or persistent erythroid aplasia [4]. The virus can be transmitted to the fetus, where infection of erythroid progenitors, fetal cardiac myocytes and placental endothelial cells can lead to hydrops fetalis and/or fetal death [5]. Common manifestations of B19V infection are erythema infectiosum in children or post-infection arthropathies mainly in adults, infection has been implicated in a growing spectrum of other different pathologies affecting diverse tissues and organs, including a possible involvement in autoimmune diseases [6]. A characteristic of the virus is its ability to persist in tissues of different origins, mainly bone marrow, liver, heart, synovia and skin, and constituting the so-called bioportfolio [7]

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