Figure 8.

Putative pathway underlying cell cycle elongation in the Ts65Dn mouse. Scheme of complexes cyclins/cyclin dependent kinases that regulate critical steps of the cell cycle. Skp2 may regulate both G₁/S and G₂/M transition by promoting p27^Kip1 degradation by ubiquitylation. The complex CcnB/Cdk1 specifically regulates the G₂/M transition. Skp2 and the CcnB (black circles) are down‐ regulated in Ts65Dm mice. Accordingly, an elongation of G₁ and G₂ is expected. Abbreviations: Ccn, cyclin; Cdk, cyclin dependent kinase.