Regulation of c-fgr proto-oncogene expression in Epstein-Barr virus infected B-cell lines.

We and others have previously shown that in vitro conversion of Epstein-Barr virus (EBV)-negative Burkitt lymphoma (BL) cell lines with the immortalizing B95-8 strain of EBV results in a marked elevation in levels of c-fgr proto-oncogene mRNA. We now show, using a nuclear run-off assay, that this induction results from an increase in the rate of transcription of the c-fgr gene. We also show that BL cell lines freshly converted with the non-immortalizing HR-I strain of EBV do not accumulate higher levels of c-fgr mRNA, suggesting that EBNA-2 and/or LMP, the genes which are deleted in the HR-I strain, may be involved in the pathway which leads to changes in c-fgr gene expression. In order to assess the generality of a role for the c-fgr gene in the response of B-lymphocytes to EBV-infection, which is controversial, we have analysed c-fgr expression in 6 freshly immortalized cell lines established by EBV (B95-8) infection of B-lymphocytes from the peripheral blood of normal adults and of adults with rheumatoid arthritis, from cord blood, and from foetal liver. All 6 cell lines expressed c-fgr mRNA at elevated levels compared to EBV-negative BL cell lines.