The insulator protein CTCF binding sites in the orf73/LANA promoter region of herpesvirus saimiri are involved in conferring episomal stability in latently infected human T cells

J Virol. 2012 Feb;86(3):1862-73. doi: 10.1128/JVI.06295-11. Epub 2011 Nov 30.

Abstract

Herpesviruses establish latency in suitable cells of the host organism after a primary lytic infection. Subgroup C strains of herpesvirus saimiri (HVS), a primate gamma-2 herpesvirus, are able to transform human and other primate T lymphocytes to stable growth in vitro. The viral genomes persist as nonintegrated, circular, and histone-associated episomes in the nuclei of those latently infected T cells. Epigenetic modifications of episomes are essential to restrict the transcription during latency to selected viral genes, such as the viral oncogenes stpC/tip and the orf73/LANA. In this study, we describe a genome-wide chromatin immunoprecipitation-on-chip (ChIP-on-chip) analysis to profile the occupancy of CTCF on the latent HVS genome. We then focused on two distinct, conserved CTCF binding sites (CBS) within the orf73/LANA promoter region. Analysis of recombinant viruses harboring deletions or mutations within the CBS indicated that the lytic replication of such viruses is not substantially influenced by CTCF. However, T cells latently infected with CBS mutants were impaired in their proliferation abilities and showed a significantly reduced episomal maintenance. We detected a reduced transcription of the orf73/LANA gene in the T cells, corresponding to the reduced viral genomes; this might contribute to the loss of HVS episomes, as LANA is central in the maintenance of viral episomes in the dividing T cell populations. These data demonstrate that the episomal stability of HVS genomes in latently infected human T cells is dependent on CTCF.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Binding Sites
  • CCCTC-Binding Factor
  • Cell Line
  • Chromatin Immunoprecipitation
  • Chromosomes, Artificial, Bacterial
  • DNA Primers
  • Herpesvirus 2, Saimiriine / genetics*
  • Herpesvirus 2, Saimiriine / physiology
  • Humans
  • Open Reading Frames
  • Plasmids / metabolism*
  • Polymerase Chain Reaction
  • Promoter Regions, Genetic*
  • Repressor Proteins / metabolism*
  • T-Lymphocytes / virology*
  • Viral Proteins / genetics*
  • Viral Proteins / metabolism
  • Virus Latency*

Substances

  • CCCTC-Binding Factor
  • CTCF protein, human
  • DNA Primers
  • Repressor Proteins
  • Viral Proteins