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

J Virol. 2012 Oct;86(20):11287-300. doi: 10.1128/JVI.01468-12. Epub 2012 Aug 8.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Nucleus / genetics
  • Cell Nucleus / metabolism
  • Chlorocebus aethiops
  • Chromatin / genetics
  • Chromatin / metabolism
  • DNA Replication*
  • DNA, Viral / biosynthesis
  • DNA, Viral / genetics*
  • DNA, Viral / metabolism
  • Herpesvirus 1, Human / genetics*
  • Herpesvirus 1, Human / metabolism
  • Nucleoproteins / genetics
  • Nucleosomes / genetics*
  • Vero Cells
  • Virus Replication / genetics*

Substances

  • Chromatin
  • DNA, Viral
  • Nucleoproteins
  • Nucleosomes