Role of M-CDK in Cell cycle and Importance of CKIs

Role of M-CDK M-CDK (Maturation/Mitosis-promoting Cyclin-Dependent Kinase) is a complex formed by CDK1 and Cyclin B. It controls the cell's entry into the M phase (mitosis). Functions of M-CDK: Triggers the transition from G₂ phase to M phase. Initiates chromosome condensation. Promotes breakdown of the nuclear envelope. Helps in the formation of the mitotic spindle. Ensures proper alignment and separation of chromosomes during mitosis. Is inactivated after mitosis through Cyclin B degradation, allowing the cell to exit mitosis. Role of CDK Inhibitor (CKI) Proteins CDK inhibitor (CKI) proteins regulate the cell cycle by binding to cyclin-CDK complexes and blocking their activity. Functions of CKI proteins: Prevent uncontrolled cell division. Pause the cell cycle when DNA is damaged or conditions are unfavorable. Allow time for DNA repair before cell division. Help maintain normal cell growth and prevent tumor formation. Examples include p21, p27, and p16. In summary: M-CDK promotes entry into mitosis, whereas CDK inhibitor proteins act as brakes on the cell cycle, ensuring division occurs only when conditions are appropriate.