Regulation of FoxO activity by CBP/p300-mediated acetylation

Forkhead box, class O (FoxO) transcription factors are inhibited by insulin-induced FoxO phosphorylation. Recently, acetylation of FoxO factors by calcium response element-binding (CREB)-binding protein (CBP) and/or p300 has been identified as a novel regulatory pathway, although the exact consequences of acetylation remain unclear. We propose that binding of CBP/p300 to FoxO factors is essential for FoxO-mediated transcription. CBP and p300 act as FoxO cofactors by weakening histone–DNA interactions. Acetylation of FoxO factors, however, attenuates FoxO-mediated transcriptional activity by disrupting the interaction between FoxO factors and target DNA. Therefore, acetylation shifts the function of FoxO from cell-cycle arrest and protection against oxidative stress towards cell death.