Receptor tyrosine kinase (RTK) signalling pathways regulate many developmental decisions, but how RTK signalling controls the expression of its target genes in different contexts is poorly understood. Here, Gerardo Jiménez and co-workers reveal that octameric DNA-binding sites for the transcriptional repressor Capicua (Cic) are critically involved in RTK signalling in Drosophila (see p. ). They show that the regulation of terminal gap gene expression by the Drosophila RTK Torso in early embryos depends on octameric Cic-binding sites in the enhancer region of the gap gene huckebein. Moreover, these Cic-binding motifs are essential for recruitment of the Groucho co-repressor to the huckebein enhancer in vivo. Cic-binding sites also respond to EGFR RTK pathway activation in the embryonic neuroectoderm and in the developing wing. Finally, using synthetic enhancer constructs, the researchers show that Cic-binding motifs provide the regulatory information necessary to translate RTK signalling inputs into precise transcriptional responses in different tissues. Thus, they conclude, octameric Cic-binding motifs are general response elements for RTK signalling in Drosophila.
