title: Herpes simplex virus 1 DNA is in unstable nucleosomes throughout the lytic infection cycle, and the instability of the nucleosomes is independent of DNA replication.
abstract: Herpes simplex virus 1 (HSV-1) DNA is chromatinized during latency and consequently regularly digested by micrococcal nuclease (MCN) to nucleosome-size fragments. In contrast, MCN digests HSV-1 DNA in lytically infected cells to mostly heterogeneous sizes. Yet HSV-1 DNA coimmunoprecipitates with histones during lytic infections. We have shown that at 5 h postinfection, most nuclear HSV-1 DNA is in particularly unstable nucleoprotein complexes and consequently is more accessible to MCN than DNA in cellular chromatin. HSV-1 DNA was quantitatively recovered at this time in complexes with the biophysical properties of mono- to polynucleosomes following a modified MCN digestion developed to detect potential unstable intermediates. We proposed that most HSV-1 DNA is in unstable nucleosome-like complexes during lytic infections. Physiologically, nucleosome assembly typically associates with DNA replication, although DNA replication transiently disrupts nucleosomes. It therefore remained unclear whether the instability of the HSV-1 nucleoprotein complexes was related to the ongoing viral DNA replication. Here we tested whether HSV-1 DNA is in unstable nucleosome-like complexes before, during, or after the peak of viral DNA replication or when HSV-1 DNA replication is inhibited. HSV-1 DNA was quantitatively recovered in complexes fractionating as mono- to polynucleosomes from nuclei harvested at 2, 5, 7, or 9 h after infection, even if viral DNA replication was inhibited. Therefore, most HSV-1 DNA is in unstable nucleosome-like complexes throughout the lytic replication cycle, and the instability of these complexes is surprisingly independent of HSV-1 DNA replication. The specific accessibility of nuclear HSV-1 DNA, however, varied at different times after infection.
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Canada.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Lacasse
authors.forename: Luis M
authors.initials: LM
authors.lastname: Schang
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002522:Chlorocebus aethiops; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D018259:Herpesvirus 1, Human / Q000235:genetics* / Q000378:metabolism; D009698:Nucleoproteins / Q000235:genetics; D009707:Nucleosomes / Q000235:genetics*; D014709:Vero Cells; D014779:Virus Replication / Q000235:genetics*
chemical_list: D002843:Chromatin; D004279:DNA, Viral; D009698:Nucleoproteins; D009707:Nucleosomes