A polycistronic transcript in transformed cells encodes the dihydrofolate reductase of herpesvirus saimiri

Scott Whitaker, Peter Geck, Maria M. Medveczky, Jolan Cus, Szu Hao Kung, Troy Lund, Peter G. Medveczky

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Herpesvirus saimiri, an oncogenic gamma herpesvirus of primates, is the only eukaryotic virus that carries the entire metabolic gene set for a complex biochemical synthesis. Every element of the thymidine synthesis gene cascade is present in the virus, and their function is probably related to the uniquely high A + T content of the genome. Although one member of the gene set, dihydrofolate reductase (DHFR), is mapped in a region required for oncogenesis, very little is known of the expression and function of this gene in transformed cells. We report the expression of the DHFR sequence on a novel, unique tricistronic transcript in virally transformed tumor cells. The DHFR sequence is the first open reading frame on a 5.3 kb minor transcript. Alpha-amanitine sensitivity indicates that it is an RNA polymerase II transcript, and since it is also polyadenylated it appears to be a functional, relatively unstable (half-life 3 hr) mRNA. Initiation of transcription uniquely overlaps with the HSUR3 small RNA gene. Expression of the small transcript appears to be alpha-amanitine resistant, implicating polymerase III transcription. Together with the remarkably low-level expression of HSUR3 in tumor cells, the data may indicate transcription interference between two different RNA polymerases, with unusual overlapping regulation and initiation.

Original languageEnglish (US)
Pages (from-to)163-172
Number of pages10
JournalVirus Genes
Issue number2
StatePublished - Jun 1995


  • DHFR
  • Herpesvirus saimiri
  • T cells
  • U-RNA
  • oncogene
  • tri-cistronic mRNA


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