Generation of EBV negative derivatives of MutuI cells. a) Schematic representation of wild type and dominant negative forms of EBNA1. b) Scheme for infection and selection of retrovirally infected MutuI cells. c) Analysis of infected clones for the presence of EBV. Top panel shows Western blot analysis of EBNA1, actin and EBNA1dn. Antibodies used are described in materials and methods section. Lower panels show PCR results analyzing the presence of EBV DNA in clones. Primers were generated which amplify regions within the indicated BamHI EBV genomic fragments.