The Effect And Mechanismof 4E-BP1 In DNA Damageresponse

Objective To explore the effect and mechanism of 4E-BP1(e IF4E-binding protein 1)in celluar response to DNA damage causing by ionizing radiation.Methods Hep G2 cells were irradiated with 4Gy 60Coγ-ray, then detected the protein expressions of 4E-BP1 and phosphorylation of 4E-BP1 at Thr-37/46 by Western blot assay.Hep G2 cells and He La cells were transfected with p Sico R-Pruo-4E-BP1 sh RNA to knockdown 4E-BP1.Cell count method was used to study the cell growth curve. Phosphorylated histone3 at Ser10,which is known as a molecular markers of mitotic cells,was combined with flow cytometric to analyze the cell cycle G2/M checkpoint.Results The phosphorylation level of 4E-BP1 at Thr-37/46 was significantly induced by ionizing radiation in Hep G2 cells, and which was associated with the G2/M arrest.Depression of 4E-BP1 resultedin slowingdown on cells growth,and increased the sensitivity of cells to 0.5~1Gy of lower dose irradiation.The detection of p H3/Ser10 positive cells(mitotic cell population) demonstrated cells and control cells by 4Gy 60Coγ-ray irradiation, but the time of released from G2 phase arrest was different. At 12h post irradiation,the ratio of the mitotic cells in He La-sh4E-BP1 cells has reached to 4.26%, while that of He La-shvector cells was only 2.24%.The stability of 4E-BP1 protein was decreased by PI3 K kinase inhibitors.Conclusions The phosphorylation of 4E-BP1 at Thr-37/46 was upregulated by 4Gy 60Coγ-ray. Depression of 4E-BP1 results in the decrease of cell growth activity and sensitizes cells to 1Gy and less lower doses irradiation.Loss of 4E-BP1 does not affect the activation of G2/M checkpoint,but speeds up the releasing of cells from G2 phase arrest. The stability of 4E-BP1 protein is regulated by PI3 K family members.