A cancer-associated Epstein-Barr virus BZLF1 promoter variant enhances lytic infection
Fig 2
Residue -141 in the Zp-V3 promoter is critical for response to BCR crosslinking.
(A) The Z promoter sequences in the B95.8 (top) and M81 (bottom) EBV strains are shown. B95.8 is the prototype (Zp-P) while M81 has the 3 polymorphisms at -100, -106, and -141 that define Variant 3 (Zp-V3). There are 4 additional basepair differences between the two Zp sequences, located at -274, -365, -460, and -525 (relative to the transcriptional start site), highlighted in gray. (B) EBV-negative BJAB cells were transfected with wildtype or mutant Zp-V3 luciferase constructs (named to reflect the promoter basepair altered in Zp-V3 relative to the Zp start site) and treated with or without anti-IgM. The luciferase activity for each construct is shown and results were normalized to that of each promoter’s untreated condition (set as 1). (C) BJAB cells were transfected with either the wildtype Zp-P luciferase construct or a mutant Zp-P construct in which the A nucleotide located at -141 is switched to the G nucleotide found in the Zp-V3 sequence. Cells were treated with or without anti-IgM 24 hours after transfection. Luciferase activity was measured at 48 hours after transfection and results were normalized to that of each promoter’s untreated condition (set as 1). The fold increase in luciferase activity is shown for each condition (average and SD).