Insertion of an EYFP-pp71 (UL82) coding sequence into the human cytomegalovirus genome results in a recombinant virus with enhanced viral growth

J Virol. 2008 Nov;82(21):10543-55. doi: 10.1128/JVI.01006-08. Epub 2008 Aug 20.

Abstract

The human cytomegalovirus (HCMV) UL82-encoded tegument protein pp71 has recently been shown to activate viral immediate-early (IE) gene expression by neutralizing a cellular intrinsic immune defense instituted by the ND10 protein hDaxx. Pp71 localizes to ND10 upon infection and induces the degradation of hDaxx. Here, we report the successful generation of a recombinant HCMV expressing enhanced yellow fluorescent protein (EYFP) fused to the N terminus of pp71. Intriguingly, insertion of the EYFP-UL82 coding sequence into the HCMV AD169 genome gave rise to a recombinant virus, termed AD169/EYFP-pp71, that replicates to significantly higher titers than wild-type AD169. In particular, we noticed strongly increased protein levels of pp71 after AD169/EYFP-pp71 inoculation. Although the high abundance of pp71 resulted in augmented packaging of the tegument protein into viral particles, no increased hDaxx degradation was detectable upon AD169/EYFP-pp71 infection. In contrast, further investigation revealed a significantly enhanced viral DNA replication compared to wild-type AD169. Thus, we hypothesize that an as-yet-unidentified function of pp71 contributes to the enhanced infectivity of AD169/EYFP-pp71. This assumption is additionally supported by the observation that increased early and late gene expression after AD169/EYFP-pp71 infection occurs independent of elevated IE protein levels. Finally, immunofluorescence analyses confirmed that hDaxx determines the ND10-localization of pp71 upon infection, since pp71 exhibited a nucleolar distribution in the absence of hDaxx. Taken together, we generated a recombinant HCMV that constitutes a useful tool not only to dissect the in vivo dynamics of pp71 subnuclear localization more precisely but also to explore new features of this viral transactivator.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism
  • Bacterial Proteins / genetics*
  • Cells, Cultured
  • Co-Repressor Proteins
  • Cytomegalovirus / genetics*
  • Cytomegalovirus / growth & development*
  • DNA Replication
  • DNA, Viral / biosynthesis
  • Humans
  • Luminescent Proteins / genetics*
  • Molecular Chaperones
  • Mutagenesis, Insertional*
  • Nuclear Proteins / metabolism
  • Recombinant Fusion Proteins / genetics*
  • Viral Proteins / biosynthesis
  • Viral Proteins / genetics*
  • Virus Replication

Substances

  • Adaptor Proteins, Signal Transducing
  • Bacterial Proteins
  • Co-Repressor Proteins
  • DAXX protein, human
  • DNA, Viral
  • Luminescent Proteins
  • Molecular Chaperones
  • Nuclear Proteins
  • Recombinant Fusion Proteins
  • Viral Proteins
  • yellow fluorescent protein, Bacteria
  • cytomegalovirus phosphoprotein 71kDa