Distinct transcriptional and functional properties of the R transactivator gene orf50 of the transforming herpesvirus saimiri strain C488

Virology. 2000 Mar 1;268(1):167-77. doi: 10.1006/viro.1999.0167.


The transformation-associated region of herpesvirus saimiri strains is variable, whereas other parts of the virus genome are highly conserved. However, we observed considerable interstrain sequence divergence of the early viral regulatory orf50 gene, which encodes the R transactivator, a homolog of Epstein-Barr virus BRLF1. The orf50 gene of strain C488 was transcribed at low abundance during lytic infection, whereas antisense transcripts were simultaneously expressed at high levels. A spliced variant, orf50a, was detectable by RT-PCR and RNase protection assays in stimulated C488-transformed, nonpermissive human T cells. In contrast to strain A11, the short, unspliced orf50b form of C488 displayed complete transactivation capability on the orf6 and orf57 promoters. In summary, there are unexpected structural and functional differences between the orf50 genes of herpesvirus saimiri strains, which differ in their capability to transform human T lymphocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Line, Transformed
  • Cell Transformation, Viral*
  • Gene Expression Regulation, Viral
  • Genes, Viral
  • Herpesvirus 2, Saimiriine / genetics*
  • Herpesvirus 2, Saimiriine / physiology*
  • Humans
  • Molecular Sequence Data
  • Open Reading Frames / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • T-Lymphocytes / virology*
  • Trans-Activators / chemistry
  • Trans-Activators / genetics*
  • Transcriptional Activation*
  • Virus Replication


  • ORF 50 transactivator
  • Trans-Activators

Associated data

  • GENBANK/AJ131935
  • GENBANK/AJ131936
  • GENBANK/AJ131937
  • GENBANK/AJ131938
  • GENBANK/AJ131939