中文摘要：

目的探讨DNA甲基化转移酶3b（DNMT3b）对人肝癌细胞株SMMC-7721中DLC-1基因的表达及其启动子区甲基化状况的影响。方法将sMMC-7721细胞株分为两组，试验组应用siRNA技术沉默DNMTab的表达，对照组仅转染对照siRNA；应用Western Blot技术分别检测两组细胞中DNMT3b和DLC-1的表达，并应用甲基化特异性PCR（MSP）技术分别检测两组细胞中DLC-1基因启动子区的甲基化状况。结果试验组中DNMT3b的表达明显低于对照组，而DLC-1的表达明显高于对照组；两组中DLC1启动子区甲基化状态无差异，均发生甲基化。结论siRNA技术抑制DNMT3b的表达可使DLC-1基因表达水平增高，但DLC-1启动子区甲基化状态无变化。此过程中DNMT3b并非作为甲基转移酶，而可能是作为转录调控因子影响DLC-1的表达。

英文摘要：

Objective To explore the effects of DNMT3b on the expression and methylation status of the promoter region of DLC-1 in human hepatocellular carcinoma cell line. Methods The SMMC-7721 cell line was divided into 2 groups. The cell line in the experimental group was transfect ed with DNMT3b siRNA, while that in the control group was transfected with control siRNA. West- ern blot was used to detect the expression of DNMT3b and DLC 1 and MSP was employed to examine the methylation status of the promoter region of DLC-1. Results The expression of DNMT3b was significantly higher in the experimental group than in the control group, while the expression of DLC- 1 was just opposite. There was no significant difference in the methylation status of the promoter region of DLC-1 between the 2 groups and both were methylated. Conclusion The inhibition of expression of DNMT3b by siRNA method can enhance the expression level of DLC-1, and the methylation status of the promoter region of DLC 1 does not change at the same time. When affecting the expression of DLC-1, DN- MT3b might not play the role of methyltransferase, but can act as a transcriptional regulatory factor.