Fig. 6. PRE silencing is destabilized by TRX or GAL4. GAL-TRX (A-D) and GAL4 (E-F) counteract silencing when targeted to the BHL4G4PRE reporter gene. When GAL-TRX is induced at the blastoderm stage, it interferes with the formation of the repressive complex in old embryos as well as in larvae (A). When GAL-TRX is induced after 5-6 hours (B) or during larval development (C), repression is not affected. When the TRX level is reduced, targeting GAL-TRX (D) at blastoderm to the BHL4G4PRE leads to a partial derepression in embryos and larvae. However, the residual repression is well maintained throughout development. Targeting GAL4 to the BHL4G4PRE gave similar results (E), with a partial derepression in a trx mutant background (F).