乙型肝炎病毒复制对肝细胞Id家族表达的影响

Effect of hepatitis B virus replication on the expression of inhibitor of differentiation family in hepatocytes

摘要:

目的：研究肝细胞中乙型肝炎病毒（hepatitis B virus，HBV）复制对分化抑制因子（inhibitor of differentiation，Id）家族表达的影响。方法：利用qRT-PCR、Western blot检测分析Id家族在HBV瞬时或稳定复制的肝癌细胞中表达水平的变化，并在HBV复制质粒PCH9-HBV1.1转染的正常肝细胞和HBV转基因小鼠肝组织细胞模型中进一步验证。将乙型肝炎病毒S蛋白（hepatitis B virus S protein，HBs）、乙型肝炎病毒核心蛋白（hepatitis B virus core protein，HBc）、乙型肝炎病毒DNA聚合酶（hep－atitis B virus DNA polymerase，HBp）、乙型肝炎病毒X蛋白（hepatitis B virus X protein，HBx）的过表达质粒转染HepG2细胞，检测各组与载体对照组细胞中Id家族表达水平的变化，分析比较乙肝病毒编码的4种蛋白对Id家族的调控作用。利用荧光素酶报告基因检测病毒各组分蛋白对Id蛋白启动子活性的影响。结果：瞬时转染HBV表达质粒的HepG2细胞较对照组细胞，Id1、Id3的mRNA和蛋白表达水平均降低（mRNA：t=3.952、3.189，P=0.017、0.033；蛋白：t=10.532、4.155，P=0.000、0.014）；HepG2.2.15中Id1、Id3 mRNA和蛋白的表达水平较HepG2对照组均下降（mRNA：t=5.553、7.211，P=0.005、0.002；蛋白：t=4.193、3.849，P=0.014、0.018）；HepAD38（Tet-）中Id1、Id3蛋白的表达量较 HepAD38（Tet+）组均降低（t=3.052、3.712，P=0.038、0.021）。同时，HBV的复制可以抑制LO2细胞及小鼠肝组织中Id1、Id3的表达（mRNA：t=14.564、3.281、3.489、3.495，P=0.000、0.030、0.025、0.025；蛋白：t=5.651、5.336、4.948、5.149，P=0.005、0.006、0.008、0.007）。转染HBV病毒各编码蛋白质粒的HepG2细胞中，HBc组Id1、Id3较载体对照组的mRNA表达水平降低最明显（77.7%、76.2%，F=9.945、37.528，t=6.481、10.915，P=0.000、0.000），Western blot结果显示HBx组Id1、Id3蛋白表达量下降最明显（86.2%、68.4%，F=38.225、7.159，t=12.550、5.295，P=0.000、0.001）。双荧光素酶报告基因检测结果表明，HBc组Id1、Id3启动子活性较对照组降幅最大（62.2%、56.3%，F=16.530、5.210，t=5.442、3.222，P=0.000、0.019）。结论：乙型肝炎病毒可以抑制肝组织、细胞中Id1及Id3的表达，其中HBc对Id1、Id3 mRNA的下调最明显，HBx则对Id1、Id3 蛋白水平上的抑制作用最明显。

Abstract:

Objective：To investigate the effect of hepatitis B virus（HBV） replication on the expression of inhibitor of differentiation （Id） family in hepatocytes. Methods：The methods of qRT-PCR and Western blot were used to measure the expression of Id family in hepatoma cells with transient or stable HBV replication，and the results were further validated in normal liver cells transfected with PCH9-HBV1.1 HBV replicating plasmid and HBV transgenic mouse liver tissue cells. HepG2 cells were transfected with plasmids with overexpression of hepatitis B virus S protein（HBs），hepatitis B virus core protein（HBc），hepatitis B virus DNA polymerase（HBp），or hepatitis B virus X protein（HBx），the change in the expression of Id family was measured in these groups and the vector control group，and the regulatory effect of four HBV-en－coded proteins on Id family was analyzed and compared. Lu－ciferase reporter gene assay was used to analyze the effect of virus component proteins on the activity of Id promoter. Results：Com－pared with the control group，the group of HepG2 cells with transient transfection of HBV plasmids had significant reductions in the mRNA and protein expression of Id1 and Id3（mRNA：t=3.952 and 3.189，P=0.017 and 0.033；protein：t=10.532 and 4.155，P=0.000 and 0.014）；compared with the HepG2 control group，the HepG2.2.15 group had significantly lower mRNA and protein expression of Id1 and Id3（mRNA：t=5.553 and 7.211，P=0.005 and 0.002；protein：t=4.193 and 3.849，P=0.014 and 0.018）；compared with the HepAD38（Tet+） group，the HepAD38（Tet-） group had significantly lower protein expression of Id1 and Id3（t=3.052 and 3.712，P=0.038 and 0.021）. In addition，HBV replication significantly inhibited the mRNA and protein expression of Id1 and Id3 in LO2 cells and mouse liver tissue（mRNA：t=14.564，3.281，3.489，and 3.495，P=0.000，0.030，0.025，and 0.025；protein：t=5.651，5.336，4.948，and 5.149，P=0.005，0.006，0.008，and 0.007）. Among the HepG2 cells transfected with HBV-encoded protein plasmids，the HBc group had the greatest reductions in the mRNA expression of Id1 and Id3 compared with the vector control group（77.7% and 76.2%，F=9.945 and 37.528，t=6.481 and 10.915，P=0.000 and 0.000），and Western blot showed that the HBx group had the greatest reductions in the protein expression of Id1 and Id3（86.2% and 68.4%，F=38.225 and 7.159，t=12.550 and 5.295，P=0.000 and 0.001）. The dual-luciferase reporter gene assay showed that the HBc group had the greatest reduction in the promoter activity of Id1 and Id3（62.2% and 56.3%，F=16.530 and 5.210，t=5.442 and 3.222，P=0.000 and 0.019）. Conclusion：HBV can inhibit the expression of Id1 and Id3 in liver tissue and hepatocytes. HBc has the most significant effect in downregulating the mRNA expression of Id1 and Id3，while HBx has the most significant inhibitory effect on the protein expression of Id1 and Id3.