DIFFERENT ACTIVATION OF EPSTEIN-BARR-VIRUS IMMEDIATE-EARLY AND EARLY GENES IN BURKITT-LYMPHOMA CELLS AND LYMPHOBLASTOID CELL-LINES

Specific expression of the Epstein-Barr virus (EBV) immediate-early an d early gene products Zta, Rta, I'ta, and MSta by a recombinant vaccin ia virus system allowed us to analyze the first steps in the induction of the lytic cycle in EBV-infected Burkitt lymphoma (BL) cells and ly mphoblastoid cell lines (LCLs). Significant differences in the inducti on of early genes were found between these cell types: whereas in BL c ells the trans activator Zta was found to induce key steps of the earl y lytic cycle, only minor activities of Zta mere noted in LCLs. Contra ry to Zta, the trans activator Rta was found to be highly effective in LCLs. These observations suggest that Rta may play an important role in the activation of the early lytic cycle in LCLs, although it cannot be activated by Zta. The latter may be a reason for the lower tendenc y of LCLs to switch into the lytic cycle compared with BL cells or dif ferentiated epithelial cells.