Prohibitin 2调节肌细胞增强因子2转录因子活性的分子机制

Molecular mechanism of regulation of Prohibitin 2 on transcriptional activity of myocyte enhancer factor 2

目的:探讨Prohibitin 2(PHB2)抑制肌细胞增强因子2(myocyte enhancer factor,MEF2)转录因子活性的分子机制,为进一步研究PHB2在其他MEF2阳性表达细胞中的调控作用提供依据。方法:利用脂质体转染方法将表达PHB2和MEF2的真核表达载体与荧光素酶报告基因载体共转染入体外培养的Hela细胞中,转染36 h后,裂解细胞获取细胞裂解上清,Western blotting检测上清中重组蛋白的表达及利用发光检测仪检测上清中荧光素酶的生物发光活性。结果:转染PHB2细胞组与未转染PHB2细胞组中,MEF2调控的荧光素酶生物发光活性比分别为0.28±0.02和1.00±0.02,两组比较差异具有显著性(P<0.01),且降低程度与PHB2的表达量呈正比;在未转染PHB2细胞组,MEF2转录激活区调控的荧光素酶生物发光活性比为9.53±1.06,而在转染PHB2细胞组其为2.24±0.21,两组比较差异具有显著性(P<0.01);组蛋白去乙酰化酶(HDAC)抑制剂TSA处理组与未处理组,共转染PHB2细胞中MEF2调控的荧光素酶生物发光活性比分别为0.98±0.12和0.38±0.04,两组比较差异具有显著性(P<0.01),提示TSA解除了PHB2对MEF2的抑制作用。结论:PHB2抑制MEF2转录活性的分子机制是通过作用于MEF2的转录激活区由HDAC介导完成的,该抑制作用非依赖于成肌调节因子MyoD,且与MEF2的DNA结合功能无关。

Objective To explore the mechanism underlying Prohibitin 2（PHB2）-mediated repression on myocyte enhancer factor 2（MEF2） and facilitate the study of the role of PHB2 in other MEF2 positive cells.Methods Using lipofectamin transfection method,Hela cells were co-transfected with plasmid expressing PHB2 and MEF2 and luciferase reporter plasmid.36 h after transfection,the recombinant proteins were tested with Western blotting and the activity of luciferase was measured with luminator in the supernatant of cell lysis.Results Compared with the cells without PHB2 transfection,the inhibitory fold of co-transfected PHB2 on MEF2-dependent expression of luciferase was 0.28（P〈0.01） and proportional to the amount of PHB2 expression.The activation fold of MEF2 transactivation domain on the expression of luciferase was 2.24±0.21 when co-transfected with PHB2,while it was 9.53±1.06 without PHB2（P〈0.01）.Upon the treatment of TSA,the inhibitor for histone deacetylase（HDAC）,the inhibitory fold of co-transfected PHB2 on MEF2 was changed from 0.38 to 0.98（P〈0.01）.Conclusion PHB2 represses the transcriptional activity of MEF2 by specifically acting on its transctivation domain and through HDAC to mediate the repression,but independently on MyoD and DNA binding activity of MEF2.