The histone demethylase Ubiquitously Transcribed Tetratricopeptide Repeat Protein X-Linked (UTX/KDM6A) demethylates H3K27me2/3 at genes and enhancers and is often inactivated by mutations in urothelial carcinoma (UC). The consequences of its inactivation are however poorly understood. We have investigated the consequences of moderate UTX overexpression across a range of UC cell lines with or without mutations in KDM6A or its interaction partners and in a normal control cell line. Effects on cell proliferation, especially long-term, varied dramatically between the cell lines, ranging from deleterious to beneficial. Similarly, effects on global gene expression determined by RNA-Seq were variable with few overlapping up- or downregulated genes between the cell lines. Our data indicate that UTX does not act in a uniform fashion in UC. Rather, its effect depends on several contingencies including, prominently, the status of KMT2C and KMT2D which interact with UTX in the COMPASS complex. In particular, we provide evidence that these factors determine the amount of nuclear UTX.
Keywords: COMPASS complex; MLL; RNA-sequencing; UTX; bladder cancer; chromatin regulator; histone demethylase; histone methylation; nuclear localization.