Multiple functions of p27 in cell cycle, apoptosis, epigenetic modification and transcriptional regulation for the control of cell growth: A double-edged sword protein.

The cell cycle is controlled by precise mechanisms to prevent malignancies such as cancer, and the cell needs these tight and advanced controls. Cyclin dependent kinase inhibitor p27 (also known as KIP1) is a factor that inhibits the progression of the cell cycle by using specific molecular mechanisms. The inhibitory effect of p27 on the cell cycle is mediated by CDKs inhibition. Other important functions of p27 include cell proliferation, cell differentiation and apoptosis. Post- translational modification of p27 by phosphorylation and ubiquitination respectively regulates interaction between p27 and cyclin/CDK complex and degradation of p27. In this review, we focus on the multiple function of p27 in cell cycle regulation, apoptosis, epigenetic modifications and post- translational modification, and briefly discuss the mechanisms and factors that have important roles in p27 functions.