Fig. 5. Sens is recruited to the ac regulatory region via protein-protein interactions. (A) An S2 cell transcription assay using the ac-luc reporter with mutations in various combinations of E-boxes. wt, wild type; E1-3, mutant E-boxes 1-3 (see Fig. 1A). Blue bars represent the presence, and red bars represent the absence, of the S-box on the ac-luc reporter. The absence of the S-box does not affect the expression mediated by Ac and Da when no Sens protein is present. (B) Amplification of the expression induced by Ac and Da upon addition of Sens. The absence of the S-box significantly increases the ability of Sens to synergize with proneural proteins on the ac-luc reporter.