Physical association of functionally antagonistic enzymes: KDM5A interacts with MLLs to regulate gene expression in a promoter specific manner facilitating EMT and pluripotency

Differential expression of genes involved in physiological processes are a collaborative outcome of interactions among signalling molecules, downstream effectors and epigenetic modifiers, which together dictate the regulation of genes in response to specific stimuli. MLLs and KDM5A are functionally antagonistic proteins as one acts as writer and the other as eraser of the active chromatin mark, i.e., H3K4me3. KDM5A promotes EMT by occupying promoters of both epithelial and mesenchymal markers. Through this work, it is illustrated that when bound to E-cadherin promoter, KDM5A acts as a classical repressor by demethylating H3K4me3, but on mesenchymal marker promoters, it acts as a transcriptional activator by inhibiting the activity of HDACs and increasing H3K18ac. Further it is demonstrated that KDM5A occupancy enhances either MLL1 or MLL2 by physically interacting with them and that signalling pathways regulate the enzymatic activity of KDM5A probably by phosphorylation. When not active, KDM5A signals for MLL occupancy, a mechanism that can be called epigenetic signalling.