We tested whether transcription activator-like effectors (TALES) could mediate repression and activation of endogenous enhancers in the Drosophila genome. TALE repressors (TALERS) targeting each of the five even-skipped (eve) stripe enhancers generated repression specifically of the focal stripes. TALE activators (TALEAs) targeting the eve promoter or enhancers caused increased expression primarily in cells normally activated by the promoter or targeted enhancer, respectively. This effect supports the view that repression acts in a dominant fashion on transcriptional activators and that the activity state of an enhancer influences TALE binding or the ability of the VP16 domain to enhance transcription. In these assays, the Hairy repression domain did not exhibit previously described long-range transcriptional repression activity. The phenotypic effects of TALER and TALEA expression in larvae and adults are consistent with the observed modulations of eve expresion. TALEs thus provide a novel tool for the detection and functional modulation of transcriptional enhancers in their native genomic context.
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