CKS proteins are evolutionarily conserved cyclin-dependent kinase (CDK) subunits whose functions are incompletely understood. Mammals have two CKS proteins. CKS1 acts as a cofactor to the ubiquitin ligase complex SCF SKP2 to promote degradation of CDK inhibitors, such as p27. Little is known about the role of the closely related CKS2. Using a Cks2 -/- knockout mouse model, we show that CKS2 counteracts CKS1 and stabilizes p27. Unopposed CKS1 activity in Cks2 -/- cells leads to loss of p27. The resulting unrestricted cyclin A/CDK2 activity is accompanied by shortening of the cell cycle, increased replication fork velocity, and DNA damage. In vivo, Cks2 -/- cortical progenitor cells are limited in their capacity to differentiate into mature neurons, a phenotype akin to animals lacking p27. We propose that the balance between CKS2 and CKS1 modulates p27 degradation, and with it cyclin A/CDK2 activity, to safeguard replicative fidelity and control neuronal differentiation.
Frontini, M., Kukalev, A., Leo, E., Ng, Y. M., Cervantes, M., Cheng, C. W., … Yu, V. (2012). The CDK Subunit CKS2 Counteracts CKS1 to Control Cyclin A/CDK2 Activity in Maintaining Replicative Fidelity and Neurodevelopment. Developmental Cell, 23(2), 356–370. https://doi.org/10.1016/j.devcel.2012.06.018