One thousand and one ways of making functionally similar transcriptional enhancers

Expression of most genes is regulated by the interaction of multiple transcription factors with cis-regulatory sequences. Many studies have focused on how changes in promoters and enhancers alter gene expression and phenotype. Recently, Hare et al., using elegant wet and computational approaches uncovered a series of enhancers driving the expression of the even-skipped gene in scavenger flies (Sepsidae). Despite the strong sequence divergence between the enhancers in sepsids and drosophilids, they lead to remarkably similar patterns of gene expression in transgenic Drosophila embryos. This can be explained by the existence of intra-enhancer compensatory mutations and the presence of overlapping/near binding sites for activators and repressors.