mTORC1 Phosphorylates Acetyltransferase p300 to Regulate Autophagy and Lipogenesis

Acetylation is increasingly recognized as one of the major post-translational mechanisms for the regulation of multiple cellular functions in mammalian cells. Acetyltransferase p300, which acetylates histone and non-histone proteins, has been intensively studied in its role in cell growth and metabolism. However, the mechanism underlying the activation of p300 in cells remains largely unknown. Here, we identify the homeostatic sensor mTORC1 as a direct activator of p300. Activated mTORC1 interacts with p300 and phosphorylates p300 at 4 serine residues in the C-terminal domain. Mechanistically, phosphorylation of p300 by mTORC1 prevents the catalytic HAT domain from binding to the RING domain, thereby eliminating intra-molecular inhibition. Functionally, mTORC1-dependent phosphorylation of p300 suppresses cell-starvation-induced autophagy and activates cell lipogenesis. These results uncover p300 as a direct target of mTORC1 and suggest that the mTORC1-p300 pathway plays a pivotal role in cell metabolism by coordinately controlling cell anabolism and catabolism.