[Molecular mechanism of the inhibitory effect of retinoic acid-induced gene G protein on tumor cell proliferation].

Objective To investigate the molecular mechanisms of anti-proliferative effect of retinoic acid-induced gene G(RIG-G)protein on tumor cells.Methods HA-RIG-G expression plasmid and FLAG-Jun activating binding protein 1(JAB1)expression plasmid were construction and transfected into the African green monkey kidney cells of the line CDS-7 and mouse fibroblast cells of the line NIH3T3.Western blotting was used to detect the p27 expression in the cells.analysis,and Immunofluorescence staining was used to examine the distribution of JAB1 protein.Coimmunoprecipitation was used to analyze the interference of RIG-G on the function of JAB1 protein.Results Coimmunoprecipitation showed that when HA-RIG-G and FLAG-JAB1 were co-expressed,the RIG-G protein and JAB1 protein could be coprecipitated by the antibodies of the other side.RIG-G was able to interact with JAB1 and alter its intracellular localization and distribution.When JAB1 was transfected alone into the NIH3T3 cells,it dispersed in both nucleus and cytoplasm:however,when RIG-G and JAB1 were cotransfected,the nuclear JAB1 was markedly diminished and exhibited a partly co-localization with RIG-G in the cytoplasm.Western blotting showed that along with the increase of the dose of transfected JAB1 the amount of p27 in the cell;and along with the increase of co-transfected RIG-G gene expression plasmid the amount of p27 in the cells re-increased.Conclusion RIG-G interacts with JAB1,thus resulting in JAB1 sequestration in the cytoplasm,disturbing the JAB1 normal function,interfering the JAB1-mediated p27 degradation,maintaining p27 protein stability so as to prevent cells from entering the cycle and inhibiting cell proliferation. Key words: Tumor cell,cultured; Tretinoin; Retinoic acid-induced gene G; PrP27-30 protein JAB1