Ribavirin-induced intracellular GTP depletion activates transcription elongation in coagulation Factor VII gene expression
Ribavirin-induced intracellular GTP depletion activates transcription elongation in coagulation Factor VII gene expression
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利巴韦林诱导的细胞内 GTP 耗竭激活凝血因子 VII 基因表达中的转录延伸
DOI：
10.1042/bj20121286
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发表时间：
2013
影响因子：
4.1
通讯作者：
et al.
中科院分区：
文献类型：
--
作者：
Atsuo Suzuki;et al.
凝血FVII（凝血因子VII）是一种在肝细胞中合成的维生素K依赖性糖蛋白。既往有报道，利巴韦林治疗可上调丙型肝炎病毒感染的血友病患者FVII基因（F7）表达，但其确切机制尚不清楚。在本研究中，我们研究了利巴韦林诱导HepG 2（人肝癌细胞系）F7表达上调的分子机制。我们发现，细胞内GTP耗竭利巴韦林以及其他IMPDH（肌苷-5 ′-单磷酸脱氢酶）抑制剂，如霉酚酸和6-巯基嘌呤，上调F7的表达。FVII mRNA转录主要通过加速转录延伸而增强，这是由P-TEF B（正转录延伸因子B）复合物介导的，而不是通过启动子激活。利巴韦林在F7上调前未调节ELL（11 - 19型富赖氨酸白血病）3 mRNA表达。我们观察到利巴韦林增强了ELL 3向F7的募集，而ELL 3的敲低减少了利巴韦林诱导的FVII mRNA上调。利巴韦林还增强了CDK 9（细胞周期蛋白依赖性激酶9）和AFF 4向F7的募集。这些数据表明，利巴韦林诱导的细胞内GTP耗竭招募了一个含有P-TEFb，AFF 4和ELL 3的超延伸复合物，到F7，并调节FVII mRNA转录延伸。总的来说，我们已经阐明了利巴韦林诱导的FVII mRNA上调的转录延长，这可能是至关重要的，在体内了解其多效性功能的加速的基本机制。
Coagulation FVII (Factor VII) is a vitamin K-dependent glycoprotein synthesized in hepatocytes. It was reported previously that FVII gene (F7) expression was up-regulated by ribavirin treatment in hepatitis C virus-infected haemophilia patients; however, its precise mechanism is still unknown. In the present study, we investigated the molecular mechanism of ribavirin-induced up-regulation ofF7expression in HepG2 (human hepatoma cell line). We found that intracellular GTP depletion by ribavirin as well as other IMPDH (inosine-5′-monophosphate dehydrogenase) inhibitors, such as mycophenolic acid and 6-mercaptopurine, up-regulatedF7expression. FVII mRNA transcription was mainly enhanced by accelerated transcription elongation, which was mediated by the P-TEFb (positive-transcription elongation factor b) complex, rather than by promoter activation. Ribavirin unregulated ELL (eleven-nineteen lysine-rich leukaemia) 3 mRNA expression beforeF7up-regulation. We observed that ribavirin enhanced ELL3 recruitment toF7, whereas knockdown of ELL3 diminished ribavirin-induced FVII mRNA up-regulation. Ribavirin also enhanced recruitment of CDK9 (cyclin-dependent kinase 9) and AFF4 toF7. These data suggest that ribavirin-induced intracellular GTP depletion recruits a super elongation complex containing P-TEFb, AFF4 and ELL3, toF7, and modulates FVII mRNA transcription elongation. Collectively, we have elucidated a basal mechanism for ribavirin-induced FVII mRNA up-regulation by acceleration of transcription elongation, which may be crucial in understanding its pleiotropic functionsin vivo.