| Cyclin dependent kinases (Cdks) are critical regulators of cell cycle progression that are constitutively expressed throughout the cell cycle. Family members include Cdc2 p34, Cdk2-9, PITSLRE, PCTAIRE-1-3, KKIAMRE, KKIALRE and NKIAMRE. Prototype members of this family include Cdc2 p34 and Cdk2, which function late in the cell cycle, whereas other members, Cdk4, Cdk6 and a related protein Cdc7, are critically involved in the G1 and S phase transitions. Cdks comprise the catalytic subunit of the cell cycle kinases and they associate with specific regulatory subunits to form an active complex. Cyclin H is one such regulatory subunit that preferentially binds to Cdk7 and forms the cyclin H/Cdk7 complex, which then phosphorylates Cdc2, Cdk2 and Cdk4 to regulate cell cycle progression. Cdk5/p25 is reported to be responsible for the mitotic-like phosphoepitopes present in neurofibrillary tangles and Cdk5 has a critical role in neurodegenerative mechanisms. |
