Cyclin

Cyclin is a family of proteins that control the progression of cells through the cell cycle by activating Cyclin-dependent kinase (CDK) enzymes. The name 'cyclin' originates from the protein's cyclical production and degradation during the cell cycle.

Function

Cyclins are involved in the regulation of the cell cycle. They bind to enzymes called Cyclin-dependent kinases, which start the different stages of the cell cycle. Without cyclins, CDKs remain inactive, and the cell cycle is halted.

Structure

Cyclins are characterized by a conserved sequence called the 'cyclin box.' The amino acid sequence of the cyclin box is approximately 100 residues long, and it is located in the N-terminal region of the protein.

Types

There are several types of cyclins that are active in different parts of the cell cycle and that cause the cell to create different enzymes for certain tasks during the cell cycle. These include G1 cyclins, G1/S cyclins, S cyclins, and M cyclins.

Role in Cancer

Cyclins play a key role in driving the cell cycle, and thus, their malfunction can lead to the uncontrolled cell growth seen in cancer. Overexpression of cyclins, due to gene amplification or other mechanisms, is frequently observed in cancer cells.

See Also

• Cell cycle
• Cyclin-dependent kinase
• Cancer

Cyclin Resources
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References

External Links

• Cyclin D1 at the US National Library of Medicine Medical Subject Headings (MeSH)
• Cyclin E1 at the US National Library of Medicine Medical Subject Headings (MeSH)