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

Hui-Min Tang 1, Wei Ding 2, Yi-Han Ding 1, Jing-Jing Wu 1, Yu-Feng Li 3

Objective: Look around the the results of ubiquitin-proteasome system (UPS) on BCL6 protein level¡ê?proliferation and apoptosis of cell imatinib¡ê¡§IM¡ê?-resistant K562/G01 cells.

Methods: Western blot was utilized to identify the expression of BCL6 in K562/G01 cells pre and post treatment with protease inhibitor MG-132.The RT-PCR and Western blot correspondingly were utilised to identify the mRNA and protein expression amounts of BCL6 and USP2 in K562/G01 cells treated without or with ML364 (a ubiquitin-specific protease USP2 inhibitor). The results of IM alone or in conjunction with ML364 on proliferation and apoptosis of K562/G01 were analysed by CCK-8 method and flow cytometry.

Results: After treatment with protease inhibitor MG132, the BCL6 protein degree of K562/G01 considerably elevated (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 (Pa?<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).

Conclusion: 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.