Araf kinase antagonizes Nodal-Smad2 activity in mesendoderm development by directly phosphorylating the Smad2 linker region

TGF-β signalling through SMAD transcription factors has been implicated in embryonic mesendoderm development. Liu and colleagues reveal that the Ras-regulated kinase Raf prevents excessive mesendoderm formation by phosphorylating and promoting the degradation of SMAD2.