Embryonic stem cell differentiation is regulated by SET through interactions with p53 and β‐catenin

The multifunctional histone chaperone, SET, is essential for embryonic development in mouse. Previously, we identified SET as a factor that is rapidly downregulated during embryonic stem cell (ESC) differentiation, suggesting a possible role in the maintenance of pluripotency. Here, we set out to explore SET’s function and its mechanism in early differentiation. Using liquid chromatography tandem mass spectrometry (LC‐MS/MS), we uncover the factors and complexes, including P53 and β-catenin, by which SET regulates lineage-specification. SET knockout (KO) and shRNA-knockdown experiments for both P53 and β-catenin in SET-KO ESCs reveal that P53 knockdown partially rescues lineage-marker misregulation during differentiation. β-catenin depletion, on the other hand, rescues the elevated Wnt gene expression observed in SET-KO ESCs. Integration of multiple ChIP-seq and RNA-seq datasets reveals a predominantly activating function of SET in gene regulation. Moreover, further analysis reveals a co-regulatory relationship between SET and TCF3, a downstream effector of Wnt-signalling. Overall, we discover a role for both P53 and β-catenin in SET-regulated early differentiation and uncover a potential mechanism for SET function at the β-catenin-TCF regulatory axis.