What role do cylins play in the cell cycle?
1 Answer
Cyclins are a family of proteins that control the progression of cells through the cell cycle by activating Cyclin dependent kinase (cdk) enzymes.
Explanation:
When cyclins are synthesised, they act as an activating protein and bind to cdk's to form a Cyclin - cdk complex. This complex then acts as a signal to the cell to pass to the next cell cycle phase. Eventually the cyclin degrades, deactivating the cdk, thus signalling exit from a particular phase.
Cyclins are structurally related proteins whose levels, fluctuate through out the cell cycle. Cyclin levels in the cell are dynamically regulated through tight control over both their rate of synthesis and degradation via ubiquitin - mediated proteolysis. These cdk activators also impart distinct substrate specificity to cdk's for the temporal regulation of cell division
As well as controlling normal cell cycle progression, cyclins function also in the exiting of the cell cycle e.g. G-0 in terminally differentiated cells and the onset of senescence caused by DNA damage.
