FIG. 4.

Rta forms a ternary complex with RBP-Jk and the EBV Cp and LMP1 promoter DNAs. (A) EMSA was performed by incubating [³⁵S]methionine (³⁵S-Met)-labeled RBP-Jk alone or together with LMP-1 promoter DNA, MBP-Rta protein, and/or anti-MBP serum, as indicated. (B) EMSA was performed by incubating ³⁵S-Met-labeled RBP-Jk alone or together with Cp promoter DNA and MBP-Rta or MBP proteins, as indicated. (C) ³⁵S-Met-labeled RBP-Jk as visualized by SDS-PAGE/autoradiogram. The position of migration of molecular mass standards are indicated at left in kilodaltons. Rta stimulates DNA binding of RBP-Jk to the EBV Cp RBP-Jk element (D) and the LMP-1 promoter (E). BL-41 cells were electroporated with the indicated plasmids, as in Fig. 3 and reference 11, and the reporter plasmid 2× EBV RBP-hsp-luc (D) and pLMP-1-GL3basic (E). In panel E, RtaΔSTAD weakly repressed the LMP-1 promoter alone, so the values for RBP-Jk/VP16+RtaΔSTAD were normalized to RtaΔSTAD alone, which was set to 1-fold. *, P = 0.0011 (compared to the RBP-Jk/VP16, alone, column).