CDKN2a

What is the CDKN2a gene?


Cyclin-dependent kinase inhibitor 2a, known as CDKN2a and sometimes referred to as p16 INK4A, is a tumor suppressor gene located on the short p-arm of chromosome 9, shown in the image above under the yellow arrow.

CDKN2a belongs to the larger group of CDK inhibitors, which acts to inhibit CDK complexes-- associations of cyclins and cyclin-dependent kinases. These CDK complex are usually involved in regulating the cell cycle at various phases as they work with other cellular proteins that control cell growth and proliferation. The image below shows the different types of CDK inhibitors and the respective CDKs they inhibit.

CDKN2a inhibits the complex of cyclin dependent kinases CDK4 and cyclin D (CDK4-D) and also inhibits the complex of CDK6 and cyclin D (CDK6-D), as illustrated on the left of the image above. Because CDK4-D and CDK6-D interact with pRb by allowing to become hypophosphorylated from its unphosphorylated state during G1, inhibition of these CDK complexes by CDKN2a prevents phosphorylation of pRb. In a way, CDKN2a places a check on whether the cell cycle continues past the R-point or not. The image below illustrates this concept by showing the normal function of CDK4/6-D.



For a reminder on the function of pRb, please refer to //What is the Rb1 gene?//

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