Study The Function Of P55PIK In Cell Cycle Regulation And DNA Synthesis And The Rb Independent Mechanism

Object: The 24-amino N-terminal of p55PIK (short for N24 subsequently described) can block cell cycle at G0/G1 phase and dependent on a Rb dependent mechanism and a probalely Rb independent mechanism. In this study we over-expressed p55PIK through Ad-p55PIK-GFP to obverse the influence on cell cycle process and the DNA synthesis and find the Rb independent mechanism.Methods: Over-expressing p55PIK in FTC236 cell line through Ad-p55PIK-GFP (Thyroid cancer cell line that is lack of Rb naturally) and then detect the DNA synthesis by BrdU and H3 Thyrmidine incorporation and the cell cycle process by PI assay. Then we proved that p55PIK can bind on PCNA by co-immunoprecipitation (IP), and can promote PCNA bind to DNA polymeraseδby quantity co-immunoprecipitation(QIP), demonstrating the Rb independent mechanism in DNA synthesis.Results: Over-expression of p55PIK can promote DNA synthesis and increase the percent of S phase in FTC236 cell. P55PIK can bind on PCNA and over-expression of it can promote PCNA bind on DNA polymerase, whereas N24 the specific inhibitor of p55PIK can block these functions in FTC236 cell.Conclusion: p55PIK can promote DNA synthesis through binding on PCNA and promoting PCNA to combine with DNA polymeraseδand regulate cell cycle process in FTC236 cell.