CDK1 and CDK2 regulate phosphorylation-dependent NICD1 turnover and the periodicity of the segmentation clock

All vertebrates share a segmented body axis. Segments form periodically from the rostral end of the presomitic mesoderm (PSM) and this periodicity is regulated by the segmentation clock, a molecular oscillator that drives dynamic clock gene expression across the PSM with a periodicity that matches somite formation. Notch signalling is crucial to this process. Altering Notch intracellular domain (NICD) stability affects both the clock period and somite size. However, the mechanistic details of how NICD stability is regulated are unclear. We identified a highly conserved site crucial for NICD recognition by the SCF E3 ligase, which targets NICD for degradation. We demonstrate both CDK1 and CDK2 can phosphorylate NICD in the domain where this crucial residue lies and that NICD levels vary in a cell cycle-dependent manner. Inhibiting CDK1 or CDK2 activity increases NICD levels both in vitro and in vivo , leading to a delay of clock gene oscillations.