FIG. 6.

BMRF1 enhances binding of ZBP-89 to the gastrin promoter. (a) DG75 cells were transfected with SG5 vector alone, SG5-BMRF1 expression vector, a Flag-tagged ZBP-89 expression vector, or the combination of the ZBP-89 vector and SG5-BMRF1. Extracts were prepared 2 days after transfection and used in EMSAs with a radioactively labeled probe containing gastrin promoter sequences from −47 to −74. Antibodies directed against SP1 and SP3 were added in some conditions to determine the positions of the SP1 and SP3 complexes. Binding of the transfected Flag-tagged ZBP-89 protein was visualized by using an anti-Flag antibody. (b) Immunoblot analysis of the transfected DG75 cell extracts used in the EMSA (a) was performed by using the anti-Flag antibody to compare the levels of ZBP-89 Flag protein in the presence and absence of cotransfected SG5-BMRF1.