Cell cycle-coupled CK1δ turnover, autoinhibition, and activity.

CK1δ activity and abundance are coordinated in a cell cycle–dependent manner: assembled CK1δ is stable in G1, while free active CK1δ is degraded.

• Why it matters: The physiological relevance of CK1δ (auto)phosphorylation, autoinhibition, and regulated turnover has been unclear despite its attenuation by inhibitory phosphorylation and apparent stability under APC/C-CDH1 targeting.
• What they did: The study examined CK1δ stability and activity across cell cycle phases, comparing assembled versus free kinase and tracking degradation changes from G1 through S phase and mitotic entry.
• The result: In S phase, unassembled CK1δ seems no longer degraded, likely supporting DNA damage signaling, while mitotic entry downregulates phosphatases to promote autoinhibition and preserve kinase for rapid post-mitotic recovery.