KDM5C not only represses transcription via demethylation of H3K4me2/3 at gene promoters but also promotes gene expression in mouse embryonic stem cells (10, 15) and ERα-positive breast cancer cells (22) by converting H3K4me2/3 modifications into H3K4me1 or recruiting transcription factors on specific transcriptional enhancers. Here, KDM5C is linked to breast cancer.