MTOR modulation induces selective perturbations in histone methylation which influence the anti-proliferative effects of mTOR inhibitors
Emerging data suggest a significant cross-talk between metabolic and epigenetic programs. However, the relationship between the mechanistic target of rapamycin (mTOR) which is a pivotal regulator of cellular metabolism, and epigenetic modifications remains poorly understood. We thus explored the impact of modulating mTOR signaling on histone methylation, a well-known epigenetic modification. Our results show that constitutive mTORC1 activation caused by abrogation of TSC2 increases H3K27me3 but not H3K4me3 or H3K9me3, via 4E-BPs-mediated induction of EZH2 protein levels. Surprisingly, mTOR inhibition also induced H3K27me3 independently of TSC2. This coincided with reduced EZH2 and increased EZH1 protein levels. Notably, the ability of mTOR inhibitors to induce H3K27me3 levels was positively correlated with their anti-proliferative effects. Collectively, our findings demonstrate that both activation and inhibition of mTOR selectively increase H3K27me3 by distinct mechanisms, whereby the ability of mTOR inhibitors to induce H3K27me3 influences their anti-proliferative effects.