Hsu S L, Lin Y F, Chou C K
Graduate Institute of Microbiology and Immunology, National Yang-Ming Medical College, Taipei, Taiwan, Republic of China.
J Biol Chem. 1993 Nov 5;268(31):23093-7.
We used human hepatoma Hep3B/C16 cells as a model to examine the effect of all-trans retinoic acid on the gene expression of hepatitis B surface antigen (HBsAg). Hep3B/C16 is a clonal derivative of human hepatoma Hep3B cell which was stably transfected with HBsAg DNA sequences and can produce hepatitis B virus surface antigen. We analyzed the HBsAg product and mRNA in Hep3B/C16 cells which were exposed to retinoic acid for different periods of time. The level of HBsAg started to increase after 24 h and reached maximum at 48 h of retinoic acid treatment. However, the level of HBsAg expression was severely suppressed compared to the control cells after long term (120 h) retinoic acid treatment. Such biphasic regulation of HBsAg production by retinoic acid was paralleled by the changes of HBsAg mRNA. Nuclear run-on assays also demonstrated that the retinoic acid-mediated regulation was determined at least in part at the transcriptional level. Furthermore, an exposure of the cells to retinoic acid for only 8 h was sufficient to show that up- and down-regulation of HBsAg gene occurred 2 and 5 days later. Using a transient expression system, we demonstrated that the retinoic acid response element is located within the 5'-flanking region of the HBsAg gene.
我们使用人肝癌Hep3B/C16细胞作为模型，来研究全反式维甲酸对乙型肝炎表面抗原（HBsAg）基因表达的影响。Hep3B/C16是人肝癌Hep3B细胞的克隆衍生物，其被稳定转染了HBsAg DNA序列，能够产生乙型肝炎病毒表面抗原。我们分析了在不同时间段暴露于维甲酸的Hep3B/C16细胞中的HBsAg产物和mRNA。维甲酸处理24小时后，HBsAg水平开始升高，并在48小时达到最大值。然而，长期（120小时）维甲酸处理后，与对照细胞相比，HBsAg表达水平受到严重抑制。维甲酸对HBsAg产生的这种双相调节与HBsAg mRNA的变化平行。核转录分析也表明，维甲酸介导的调节至少部分是在转录水平上确定的。此外，细胞仅暴露于维甲酸8小时就足以表明，在2天和5天后发生了HBsAg基因的上调和下调。使用瞬时表达系统，我们证明维甲酸反应元件位于HBsAg基因的5'侧翼区域内。
