泛素连接酶β-TrCP降解BCR-ABL 融合蛋白对白血病K562 细胞增殖的抑制*

目的:t（9；22）（q34；q11）突变导致的BCR-ABL融合基因及其编码的融合蛋白在慢性粒细胞白血病（chronic myeloid leukemia，CML ）发病中发挥重要作用。本研究观察可与BCR-ABL融合蛋白N 端寡聚化区域（Oligomerization domain，OD）特异性结合的嵌合泛素连接酶E3 β-TrCP 的β-TrCP-OD-HA 的重组腺病毒载体，经泛素- 蛋白酶体途径降解BCR-ABL融合蛋白对白血病K562 细胞增殖的影响。方法:HEK293 细胞扩增野生型Ad5β-TrCP-OD-HA、突变型Ad5 Δ F-TrCP-OD-HA 及空载Ad5GFP 重组腺病毒载体，感染K562 细胞。以未感染K562细胞作空白对照，流式细胞术检测重组腺病毒载体感染效率，Western blot检测外源性重组蛋白和BCR-ABL融合蛋白的表达，通过细胞增殖曲线、甲基纤维素集落形成试验、细胞周期检测β-TrCP-OD-HA 对K562 细胞增殖的影响。结果:成功建立携β-TrCP-OD-HA 重组腺病毒载体的K562 细胞株，重组腺病毒载体感染效率达66.4% 以上，β-TrCP-OD-HA、Δ F-TrCP-OD-HA 可在K562 细胞中表达。三组重组腺病毒载体感染K562 细胞后，Ad5β-TrCP-OD-HA 组Western blot检测BCR-ABL融合蛋白含量下降；K562 细胞生长和集落形成能力均受抑制；细胞周期显示S 期细胞数下降至10.88%±2.42% 、G0/G1 期升高至85.6%±5.61% ，与Ad5 β-TrCP-OD-HA 组、Ad5GFP 组及对照组相比，差异具有统计学意义（P 均<0.05）。 结论:重组腺病毒介导的β-TrCP-OD-HA、Δ F-TrCP-OD-HA 能够在白血病K562 细胞中表达；β-TrCP-OD-HA 可以抑制K562 细胞的生长增殖，其机制可能与其降解BCR-ABL融合蛋白、阻滞细胞周期而实现。 

Antiproliferation Effect of Beta-TrCP Ubiquitin Ligase Mediated BCR-ABL Protein Degradation in Leukemia K562 Cells

Objective: The BCR-ABL fusion gene induced by reciprocal translocation of t (9; 22) (q34; q11) plays an important role in the pathogenesis of chronic myeloid leukemia (CML). Using recombinant ade-noviruses carrying the N-terminal oligomerizaton domain (OD) of the BCR/ABL and chimeric ubiquitin ligase β-TrCP, this study was to investigate the effect of the targeted degradation of oncoprotein BCR-ABL by Ubiqui- tin-Proteasome System on the proliferation of leukemia call line K562. Methods: The recombinant adenovirus-es carrying wild-type β-TrCP gene (Ad5β-TrCP-OD-HA), mutational β-TrCP gene (Ad5 A F-TrCP-OD-HA)and green fluorescent protein gene (Ad5GFP)were amplified in 293 calls and co-infected into K562 cells respec- tively. The rates of infection were analyzed by flow cytometry (FCM). Recombinant protein and BCR-ABL ex-pression was detected by Western blot. Cell proliferation was determined by cell counting and methylcellu- cose clonal cell culture. Cell cycle was observed through FCM. Untreated K562 cells were used as blank con-trols. Result: The leukemia K562 cell lines with exogenous recombinant β-TrCP-OD-HA and F-TrCP-OD-HA gene were established. The infection rates in the three groups were over 66.4% and recombinant protein sus-tained to be expressed. Ad5β-TrCP-OD-HA down-regulated the expression of BCR-ABL and inhibited prolifer-ation of K562 cells. FCM showed that the percentage of cells at S phase was decreased to 10.88%±2.42%, while that of cells at G_0/G_1 was increased to 85.6%±5.61%, with a significant difference (P<0.05). No changes were found in the cell cycle in groups of Ad5 △ F-TrCP-OD-HA and Ad5GFP. Conclusion: There is sustained ex-pression of recombinant β-TrCP-OD-HA protein in K562 cells infected by recombinant adenovirus.β-TrCP-OD-HA could inhibit the proliferation and clonogenicity of K562 cells through targeted degradation of oncoprotein BCR-ABL and arresting the progression of call cycle.