THE EPSTEIN-BARR-VIRUS GENOME ENCODES DEOXYTHYMIDINE KINASE-ACTIVITY IN A NESTED INTERNAL OPEN READING FRAME

The Epstein-Barr virus (EBV) BXLF1 fragment open reading frame (LORF), thought to encode deoxythymidine kinase (dTK) activity, and a shorter frame (SORF), starting at an internal in-frame AUG, were isolated by polymerase chain reaction from a plasmid containing the EcoR1 fragment of EBV strain FF-41. These were transfected into dTK- Escherichia col i, producing multiple SORF- or LORF-containing colonies, which express ed dTK. The 243 NH2-terminal residues of the LORF-encoded polypeptide thus are not essential for dTK activity. SORF, with 1,092 bp, is predi cted to encode a 36- to 37-kD polypeptide, in the size range of other herpesviral dTKs.