MOLECULAR-GENETIC ANALYSIS OF EPSTEIN-BARR-VIRUS CP PROMOTER FUNCTION

The Cp promoter of Epstein-Barr virus (EBV) directs most transcription of the EBNA genes in lymphoblastoid cell lines. The functions of two control regions in the Cp promoter have been studied by construction o f recombinant EBV strains containing specific mutations in these eleme nts. Mutation of the RBP-Jk (CBF1) binding site reduced but did not co mpletely abolish EBNA-2-dependent Cp activity in transient transfectio n assays. The same mutation in recombinant virus gave only a modest av erage reduction in Cp function, ranging from full activity to almost n o activity in different isolates. Separate deletion of a 262-bp region containing glucocorticoid response elements had little effect in a tr ansient assay but caused a fivefold increase in the steady-state level of Cp RNA in recombinant virus. The results indicate that other eleme nts in addition to the intensively studied RBP Jk site are important i n determining Cp activity in the whole virus. Clonal EBV-infected cell lines expressed RNA from both the Cp and Wp promoters, but the level of Wp RNA did not simply compensate for changes in the level of Cp RNA . The levels of EBNA proteins varied much less than the levels of Cp a nd Wp RNA, suggesting other types of control in addition to initiation of transcription. A survey of RNAs derived from the internal repeat r egion of the virus indicated that gene expression from this region of EBV in lymphoblastoid cell lines is accounted for by the known transcr ipts.