miR-31 is well known as an anti-metastatic microRNA (miRNA) in the context of breast cancer. However, to date the mechanism of regulation of this miRNA has yet to be elucidated. The recent publication by Viré et al. in Molecular Cell demonstrates for the first time that one mechanism of regulation of miR-31 is through the putative oncogene EMSY, whose amplification in breast cancer patients correlates with reduced expression of the miRNA. This regulation is dependent on the DNA-binding transcription factor ETS-1 which recruits EMSY and the histone demethylase KDM5B to the miR-31 promoter, thus repressing its transcription.