Characterization of Epstein-Barr virus recombinants with deletions of the BamHI C promoter.

Epstein-Barr virus (EBV) recombinants with the BamHI C promoter (Cp) deleted were compared with wild-type Cp recombinants derived in parallel for their ability to initiate and maintain latent infection and growth transformation in primary human B lymphocytes. Cp-deleted recombinants infected, transformed, and immortalized B lymphocytes in vitro as efficiently as wild-type Cp recombinant EBV. Lymphoblastoid cell lines (LCLs) infected with the Cp-deleted recombinant were indistinguishable from wild-type recombinant-infected LCLs in latent gene expression, growth rate, morphology, and surface phenotype. Deletion of Cp did not affect episomal maintenance or spontaneous entry of the virus into lytic cycle. The effect of steroid hormones on latent and lytic gene expression on Cp-deleted recombinants was analyzed and shown to be independent of the glucocorticoid response element located 5' to Cp. The BamHI W promoter, Wp, is used to transcribe EBNA genes in Cp-deleted EBV-infected cells. Wp is sufficient for growth transformation and maintenance of the lymphoblastoid phenotype of EBV-infected lymphocytes in vitro.