CDK4/cyclin D complex

Function

• CDK4 is the major catalytic subunit of mammalian cyclin D
• assembly & accumulation of functional CDK4/cyclin-D complexes is rate limiting for progression through G1
• once formed, the CDK4/cyclin-D complex must be activated by phosphorylation of Thr172 on CDK4, a reaction catalyzed by CAK
• complex formation & phosphorylation are independently regulated events
• phosphorylation of CDK4 of the CDK4/cyclin-D complex is subject to regulation by both stimulatory & inhibitory cytokine signals thus allowing CDK4 to function in a mid G1 checkpoint.
• CDK4 is also regulated by the binding of p16INK4A/MTS1 while in complex with cyclin D independent of phosphorylation status

Expression

• CDK4 protein is constitutively expressed throughout the cell cycle
• cyclin D accumulates in G1 phase of the cell cycle

More general terms

• CDK/cyclin complex
• serine/threonine kinase

More specific terms

• CDK4/cyclin D1 complex