〔Abstract〕 Objective To investigate the effects of p100Rband p80Rbtruncated forms of retinoblastoma protein(Rb) on HEK 293T cell cycle and apoptosis.Methods The eukaryotic expression plasmid pcDNA3. 1-p100Rb-FLAG and pcDNA3. 1-p80Rb-FLAG were constructed,plasmid was transfected into U2OS cells and immunofluorescence was performed to define the localization of p100Rband p80Rbin cells. Plasmid was also transfected into HEK 293T cells,and the total protein was extracted for Western blotting to detect the protein expression level. After overexpression of Rb,p100Rband p80Rbin HEK 293T cells,cell cycle and apoptosis were measured by flow cytometry.Results The eukaryotic expression plasmid pcDNA3. 1-p100Rb-FLAG and pcDNA3. 1-p80Rb-FLAG were constructed successfully. p100Rbwas mainly located in the nucleus while p80Rbwas mainly located in the cytoplasm,in U2OS cells. Rb,p100Rband p80Rbcould be overexpressed in HEK 293T cells. Following overexpression of Rb,p100Rbin HEK 293T cells,the percentage of G1phase of cell cycle significantly increased compared with the control group,and p100Rband p80Rbinhibited apoptosis compared with control group(P<0. 05).Conclusion Overexpression of p100rb can inhibit the apoptosis of HEK 293T cells and block the cell cycle. Overexpression of p80rb can inhibit the apoptosis of HEK 293T cells,but has no effect on cell cycle.