EBNA promoter usage in EBV-negative Burkitt lymphoma cell lines converted with a neomycin-resistant EBV strain

Latent Epstein-Barr virus (EBV) uses two alternative strategies to express the Epstein-Barr nuclear antigens (EBNAs). Resting normal B cells harboring latent virus and Burkitt's lymphoma (BL) cells use monocistronic messages generated from the Q promoter (restricted strategy). EBV-transformed immuno blasts express all EBNAs by using giant messages generated from the W/C pro moter (full program). Whether the virus establishes the restricted program on primary infection of a BL cell (or its progenitor) or, alternatively, wh ether such cells are generated by phenotypic downregulation from the immuno blast is unclear. We found previously that conversion of EBV-negative BL li nes to EBV-positive sublines required repeated exposure to large virus dose s. The converted sublines used the full program. However, the possibility t hat cells with a full program had a selective advantage during the long per iod of in vitro passage could not be excluded. We therefore infected EBV-ne gative BL lines with recombinant EBV carrying a neomycin resistance marker. Most convertants of the 12 lines tested were positive for YUK splicing, in dicative of the full program, but some were also positive for the restricte d QUK splice program. One convertant DG75 line showing both YUK and QUK was cloned and gave rise to stable QUK users. We conclude that EBV infection o f established BL lines can give rise to subclones with either the full or t he restricted program. The fact that all EBVs carrying BL lines use the res tricted program in vitro may be a consequence of immunoselection. (C) 2001 Wiley-Liss, Inc.