P16 - Senescence

p16 (CDKN2a) is a protein that slows the progression of the cell cycle from the G1 phase to the S phase by inhibiting CDK2 and 4. p16 has been shown to be the most useful senescence marker in vitro and in vivo.

To analyze p16 activity, we measure the expression of a fluorescent protein controlled by the p16 promoter. Thus, the fluorescence intensity is directly proportional to the promoter activity in a given cell.