Expression of the Epstein‐Barr virus encoded EBNA‐I gene in stably transfected human and murine cell lines

Five murine and 3 human tumor cell lines were transfected with a retroviral vector that carries the EBV encoded EBNA-1 gene. All cell lines expressed intranuclear EBNA-1 as detected by anticomplement immunofluorescence and Western blot assays. The cell lines differed in the level of EBNA-1 expression and the size of the protein. The internal major late promoter of adenovirus was efficient in directing the transcription of EBNA-1 in the human lymphoma line BJAB, the murine T-cell lymphoma Tikaut, RBL-5, EL-4 and in the mouse sarcoma line MSWBS but was less efficient in Ramos, an EBV negative Burkitt lymphoma line, the human T-cell leukemia line 1301TK and the P815-X2 mouse mastocytoma line. All transfected lines except MSWBS contained EBNA-1 in a truncated form. The truncated EBNA-1 polypeptide reacted with the conventional human antibody reagents in an EBNA specific fashion but failed to bind rabbit or human antibody directed against the glycine-alanine repeat sequence. MSWBS contained a truncated as well as a full size EBNA-1 polypeptide. It also reacted with antibody directed against the glycine-alanine repeat. This indicates that the repeat sequence is regularly affected by the truncation.