Figure 1.

This is a schematic diagram of 4 single, bicistronic adenovirus (Ad) vectors and confirms deletion of the E2F-1 transactivation domain. (A) The cytomegalovirus (CMV) promoter drives expression of the tetracycline (Tet)-controlled transactivator (tTA). The vector that expresses the reporter-enhanced green fluorescent protein (EGFP) or the truncated form of the E2F-1 gene (E2Ftr) is under the control of a synthetic minimal promoter composed of a Tet-responsive element (TRE) and a CMV mini-promoter (phcmv), which is silent unless activated by tTA. In the absence of Tet or doxycycline, tTA binds to phcmv and triggers the expression of EGFP or E2Ftr. When Tet is added to the medium, tTA is bound by Tet and is unable to bind to phcmv and activate the expression of EGFP or E2Ftr. The left and right inverted terminal repeat sequences (LITR and RITR, respectively), encapsidation signal (ES), and E1/E3-deleted genes are shown in the Ad structure. polyA indicates RNA with the addition of multiple adenosine monophosphates. (B) SK-MEL-2 cells were uninfected (Mock) or were infected with AdTet-EGFP, Ad-E2F-1, or AdTet-E2Ftr3 at a multiplicity of infection of 100; and, 36 hours postinfection, monoclonal antibody antihuman E2F-1 was used to detect both E2F-1 and E2Ftr expression. α-Actin was used to demonstrate equal loading for each lane.