A signaling axis involving CNOT3, Aurora B and ERK promotes mesendodermal differentiation of ES cells in response to FGF2 and BMP4

Mesendodermal cells are key intermediate progenitors that form the early primitive streak (PrS) and give rise to mesoderm and endoderm in the gastrulating embryo. We have identified an interaction between the CCR4-NOT complex member CNOT3 and the cell cycle kinase Aurora B that regulates MAPK/ERK signalling during mesendodermal differentiation. Aurora B phosphorylates CNOT3 at two sites that are located close to a nuclear localization signal and promotes localisation of CNOT3 to the nucleus in mouse ES cells (ESCs). Mutation of these sites in ESCs gives reduced numbers of embryoid bodies that are largely composed of ectoderm and interferes with differentiation of ESCs into mesendoderm in response to FGF2, BMP4, Wnt3 and Activin. The double mutation affects interaction of CNOT3 with Aurora B and ERK leading to reduced phosphorylation of ERK in response to FGF2. Our results identify a signalling axis involving CNOT3 that regulates a key pathway during embryogenesis.