KDM6A is enzymatically active at the Golgi apparatus where it is necessary for maintenance of Golgi apparatus morphology

KDM6A and KDM6B, lysine demethylases, play a central role in regulation of transcription through their demethylation activity towards H3K27me3 and have also been shown to be dynamically regulated upon epithelial-mesenchymal transition (EMT). In particular, KDM6A has been implicated in a variety of malignancies and is frequently mutated in cancers including those in kidney, bladder, colorectal, and breast. KDM6A and KDM6B function as part of the COMPASS-like protein complex (CLC) which includes methyltransferases KMT2C/KMT2D and the regulatory WRAD-subcomplex. KDM6A total protein is known to be suppressed by TGF-β in MCF10A breast cells; however, our examination of protein localization by immunofluorescence and LC-MS/MS reveals that KDM6A expression is lost in the nucleus but retained in the Golgi apparatus, independent of other CLC complex members. Importantly, KDM6A isolated from a biochemically-separated subcellular membranous fraction possesses the catalytic JmjC domain and is enzymatically active, indicating that KDM6A may have non-nuclear substrates. Further, knockdown of KDM6A and treatment with TGF-β similarly alter Golgi apparatus morphology, in a cell type specific manner, suggesting context-dependent regulatory functions. These findings support a model in which KDM6A is necessary to maintain Golgi apparatus morphology and is enzymatically active outside of the nucleus.