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组蛋白乙酰化激活人脑胶质瘤中胶质细胞源性神经营养因子转录的机制研究

The Mechanism Study on Histone Acetylation Activating Glioblastoma-derived Neurotrophic Factor Transcription

  • 摘要:
      目的  研究组蛋白乙酰化对人脑胶质瘤中胶质细胞源性神经营养因子基因(GDNF)的表达调控和具体机制。
      方法  取正常人脑组织、低级别胶质瘤脑组织(LG-glioma)、高级别胶质瘤脑组织(HG-glioma)各6例。用组蛋白乙酰化酶抑制剂和组蛋白去乙酰化酶抑制处理人脑神经胶质瘤U251细胞。实时荧光定量PCR检测脑组织及细胞中的GDNF mRNA水平,染色质免疫共沉淀(ChIP)-PCR检测GDNF启动子区转录因子cAMP应答元件结合蛋白(CREB)结合位点的H3K9乙酰化水平,以及转录因子CREB与GDNF启动子区的结合能力,同时检测组蛋白乙酰化酶和脱乙酰化酶抑制剂对转录因子CREB结合能力和GDNF表达的影响。
      结果  与正常脑组织和低级别脑胶质瘤组织比较,高级别胶质瘤组织的GDNF mRNA水平高(P < 0.01),GDNF启动子区的H3K9乙酰化水平增加(P < 0.01),且GDNF启动子上CREB结合区的乙酰化水平高于非CREB结合区的乙酰化水平(P < 0.01)。高级别胶质瘤组织中CREB与GDNF启动子区的结合能力高于正常脑组织和低级别脑胶质瘤组织(P < 0.05)。组蛋白乙酰化酶抑制剂处理U251细胞后,GDNF启动子上CREB结合区的乙酰化水平下降,CREB与GDNF启动子结合活性下调,并下调GDNF mRNA和蛋白水平,而组蛋白去乙酰化酶抑制剂具有相反作用(P < 0.01)。
      结论  组蛋白乙酰化通过促进转录因子CREB与GDNF基因启动子区的结合,从而促进胶质瘤中GDNF的高转录。

     

    Abstract:
      Objective  To study the regulation role and mechanism of protein acetylation on the expression of glioblastoma-derived neurotrophic factor (GDNF) in human glioma.
      Methods  Six normal brain tissue samples, six low-grade glioma brain tissue (LG-glioma), and six high-grade glioma brain tissue (HG-glioma) were collected for study. Human glioma U251 cells were treated with histone acetylase inhibitor and histone deacetylase inhibition. The mRNA level of GDNF in glioma and normal controls was detected by Real-time PCR. H3K9 acetylation level of cAMP-response element binding protein (CREB) binding region on GDNF promoter and the ability of CREB combining to GDNF promoter were detected by ChIP-PCR. The effects of histone acetylase and deacetylase inhibitors on transcription factor binding ability and GDNF expression were detected.
      Results  The mRNA level of GDNF in HG-glioma was significantly higher than those in normal brain tissue and LG-glioma (P < 0.01). The H3K9 acetylation level of GDNF promoter region in the glioma was increased compared to that in the normal brain tissue (P < 0.01), and the acetylation level in CREB-binding region on the GDNF promoter was higher than that in the non-CREB-binding region (P < 0.01). The binding activity of CREB and GDNF promoter in HG-glioma was higher than those in normal brain tissue and LG-glioma (P < 0.05). After treatment of U251 cells with histone acetyltransferase inhibition, the level of acetylation in CREB-binding region on GDNF promoter, the binding activity of CREB and GDNF promoter was decreased, and GDNF transcription and expression were down-regulated, while histone deacetylase inhibitors had the opposite effect (P < 0.01).
      Conclusion  Histone acetylation promotes the transcription expression of GDNF in glioma by promoting the binding of transcription factor CREB to the promoter region of GDNF gene.

     

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