Identification of the Epstein-Barr virus terminal protein gene products in latently infected lymphocytes.

The terminal protein (TP) gene produces two overlapping mRNAs in latently infected lymphocytes that are predicted to encode the similar polypeptides TP1 (497 amino acids) and TP2 (378 amino acids), with TP1 exon 1 providing 119 extra unique residues at the N terminus. Rabbit antisera were raised to procaryotic fusion proteins and used to detect expression of a predicted 53-kilodalton (kDa) TP product in transfected 293 cells and latently infected lymphocytes. Fractionation of transfected 293 cells showed this protein to be localized to an integral membrane preparation. The same fraction of latently infected lymphocytes contained proteins of 53 and 27 to 39 kDa as determined by Western immunoblotting with the TP-specific rabbit antisera. Immunoprecipitation of TP products from 35S-labeled human lymphoblastoid cells (CR/B95-8) was used in pulse-chase experiments and showed that TP1 was a labile protein with a half-life of approximately 2 to 4 h. The anti-fusion protein serum detected a 53-kDa TP1 and degradation products in the range of 25 to 35 kDa. A panel of Burkitt's lymphoma cell lines and cell lines established with virus recovered from the BL cells were analyzed by Western immunoblotting and found to contain the 53-kDa TP1 product, its degradation products, or both. Only two EBV-positive BL cell lines (BL72 and Wewak II) were negative in this assay. The results suggest that a labile TP1 protein may be expressed by most, if not all, EBV-infected cell lines.