Fig. 3.

Virion synthesis is a function of the epigenetic state of EBV DNA. (A) RT-PCR analysis of RNA prepared from HEK293 cells that had been transiently transfected for 3 days with EBV DNA (p2089) prepared from E. coli (unmeth.) or treated in vitro with the methyltransferase M.SssI (meth.). As indicated, p2089 DNA was cotransfected with a BZLF1 expression plasmid. Transcripts of essential viral lytic genes (BRLF1, BMRF1, and BLLF1) are detectable only when p2089 DNA is CpG-methylated before transfection. The genes are indicated on the right; the gene classes are given on the left. E, early; IE, immediate-early L, late; TR^–, HEK293 cells stably transfected with EBV, which served as a positive control for the induction of the lytic phase. (B) Immunostaining of transiently transfected HEK293 cells with antibodies detecting Zta, Rta, EA-D, VcAgp125, and gp350/220 encoded by the viral genes BZLF1, BRLF1, BMRF1, BALF4, and BLLF1, respectively. Controls are found in Fig. S5.