P21 - Cell cycle inhibition

The cyclin-dependent kinase inhibitor 1 (p21 or CDKN1A) is a protein capable of inhibiting all cyclin/CDK complexes, thus blocking cell cycle progression. Cell cycle inhibition is one of the most frequent effects of chemotherapy and several natural compounds are able to promote this effect.

To analyze cell cycle inhibition we measure the p21 promoter activity, by using it to control a fluorescent protein gene expression. Thus, the fluorescence intensity is directly proportional to the promoter activity in a given cell.