Correlation Does Not Imply Causation: Histone Methyltransferases, but Not Histone Methylation, SET the Stage for Enhancer Activation

Although H3K4me1 is a pervasive mark'' of enhancers, its functional requirement for enhancer activity remains unclear. In this issue of Molecular Cell, Dorighi et al. (2017) show that in some contexts, the methyltransferase complex, rather than the H3K4me1 mark, is required for gene expression.