维甲酸诱导基因G抑制肿瘤细胞增殖的分子机制研究

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

目的探讨维甲酸诱导基因G（RIG—G）抑制肿瘤细胞增殖的分子机制。方法应用转染实验、Western印迹法、免疫共沉淀和免疫荧光共定位等技术验证RIG—G蛋白与JAB1蛋白之间的相互作用，并研究RIG—G蛋白对JAB1蛋白功能的影响。结果RIG—G蛋白可以与JAB1蛋白发生相互作用，并影响JAB1蛋白在细胞内的定位和分布。实验发现，在NIH3T3细胞中单独转染JAB1时，JAB1蛋白在细胞核和细胞质内呈弥散分布，而当与RIG—G共同转染后，JAB1蛋白在细胞核内的含量明显减少，而改变为主要在胞质内分布，并与RIG—G蛋白发生部分共定位。此外，RIG—G蛋白还具有抑制JAB1对细胞周期抑制因子p27的辅助降解功能。结论RIG—G可以通过和JAB1的相互作用，使后者部分滞留在细胞质内，从而影响JAB1发挥正常功能，干扰其对p27的辅助降解，维持细胞内p27的稳定性，促进细胞退出增殖周期，抑制细胞增殖。

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 JABl-mediated p27 degradation, maintaining p27 protein stability so as to prevent cells from entering the cycle and inhibiting cell proliferation.