[Effects of Ubiquitination on the Expression of BCL6 Protein，Cell Proliferation and Apoptosis in K562/G01 Cells].

To explore the the effects of ubiquitin-proteasome system (UPS) on BCL6 protein level，proliferation and apoptosis of cell imatinib（IM）-resistant K562/G01 cells.Western blot was used to detect the expression of BCL6 in K562/G01 cells before and after treatment with protease inhibitor MG-132.The RT-PCR and Western blot respectively were used to detect the mRNA and protein expression levels of BCL6 and USP2 in K562/G01 cells treated with or without ML364 (a ubiquitin-specific protease USP2 inhibitor). The effects of IM alone or in combination with ML364 on proliferation and apoptosis of K562/G01 were analysed by CCK-8 method and flow cytometry.After treatment with protease inhibitor MG132, the BCL6 protein level of K562/G01 significantly increased (P<0.05). The mRNA and protein expression level of ubiquitin-specific protease USP2 in K562/G01 cell line was higher than that in K562 cell line (P<0.05). After treatment of K562/G01 with USP2 protease inhibitor ML364, the expression levels of USP2 and BCL6 proteins were down-regulated simultaneously (P<0.05) . After combination of ML364 and IM, both the proliferation inhibitory rate and the apoptosis rate of K562/G01 cells significantly increased(P<0.05).ML364 decreases the BCL6 protein stability in K562/G01 by inhibiting the USP2-mediated deubiquitination, and down-regulate the BCL6 protein experssion, thereby increases the sensitivity of drug-resistant cells to IM.泛素化修饰对K562/G01细胞BCL6蛋白表达水平的调节及对细胞增殖、凋亡的影响.探讨泛素蛋白酶系统（UPS）对伊马替尼（IM）耐药细胞株K562/G01中BCL6蛋白水平及耐药细胞增殖和凋亡的影响.应用Western blot技术检测蛋白酶抑制剂MG-132处理CML细胞前后BCL6蛋白水平差异；用RT-PCR及Western blot方法分别检测ML364(泛素特异性蛋白酶USP2抑制剂)处理前后K562/G01细胞株中BCL6及USP2 mRNA和蛋白的表达水平；应用CCK-8法及流式细胞术分别检测ML364和IM单用及联用对K562/G01细胞增殖及凋亡的影响.蛋白酶抑制剂MG132处理后，K562/G01的BCL6蛋白水平显著上升(P<0.05);K562/G01细胞株的去泛素化酶USP2 mRNA 和蛋白表达水平均高于K562细胞株(P<0.05)；ML364处理K562/G01后，USP2和BCL6蛋白表达水平同步下调（P<0.05）；与IM单药组相比，ML364与IM联合用药组K562/G01细胞增殖抑制率及细胞凋亡率均明显升高(P<0.05).ML364通过抑制USP2介导的BCL6蛋白去泛素化水平降低K562/G01细胞株BCL6 蛋白稳定性，使K562/G01细胞株中BCL6蛋白表达下调，从而增加耐药细胞对IM的敏感性.