Fig. 1. REPO is a transcriptional activator. (A) REPO activates transcription through a homeodomain-binding site. The effector constructs express REPO (pACT-repo) or REPO lacking its homeodomain (REPObox, pACT-repobox), driven by the Drosophila Act5C promoter. The luciferase reporter contains two copies of CAATTA (CAATTA-luc) or CAGTTA (CAGTTA-luc) motifs placed upstream of the hsp70 minimal promoter. The CaSpeR-luc reporter has a luciferase gene with the hsp70 minimal promoter alone. Three luciferase reporter plasmids were each transfected into S2 cells with pACT-repo (black column), pACT-repobox (white column) or vector (pACT) alone (gray column). The amount of luciferase activity generated by the co-transfection of CaSpeR-luc and pACT was defined as 1. (B) REPO contains multiple transcriptional activation domains. Various regions of REPO were fused to the GAL4 DNA-binding domain (DBD) and tagged with three copies of the Myc epitope at their C terminus. The reporter was the luciferase gene placed downstream of the hsp70 TATA and five copies of UAS (GAL4-binding sites). The luciferase activity obtained with each effector is presented as the relative value compared with the value obtained with GAL4-DBD alone. The expression of the GAL4 fusion proteins was confirmed by western blot analysis of whole-cell extracts using a monoclonal antibody directed against the Myc-tag. H, homeodomain; M, Myc tag.