人衰变加速因子DAF基因真核表达系统的构建

Establishment of a eukaryotic expressing system for human decay accelerating factor

目的:构建含人补体调节蛋白衰变加速因子DAF分子的cDNA编码区的真核重组表达载体pcDNA3-DAF,转染NIH3T3细胞,建立稳定表达人DAF的NIH3T3细胞模型。方法:将人DAF分子的cDNA编码区克隆到真核表达载体pcDNA3,经酶切和测序鉴定后用磷酸钙沉淀法转染NIH3T3细胞,通过G418筛选,建立稳定转染的NIH3T3细胞株。用PCR检测人DAF基因在NIH3T3细胞基因组中的整合;用RT-PCR、Westernblot实验和间接免疫荧光技术分别从RNA水平和蛋白质水平检测人补体调节蛋白分子DAF在细胞株中的表达。结果:成功构建了pcDNA3-DAF重组真核表达载体,并建立了稳定转染的NIH3T3细胞株,成功地表达了目的基因。PCR检测连续传代30次的NIH3T3pcDNA3-DAF细胞,结果显示人DAF基因仍稳定整合在异源细胞的染色体上,并未随着传代而丢失,为稳定的转染细胞株。结论:真核表达载体构建和稳定转染NIH3T3细胞株的建立为进一步研究人DAF功能和多种补体调节蛋白的协同作用奠定基础。

Objective：To construct recombinant expressing vector pcDNA3-DAF and to develop the NIH3T3 cell model expess human complement regulatory protein decay accelerating factor（DAF,CD55）stably after transfected.Methods：Human membrane complement regulatory protein（hCRP） DAF cDNA containing the full-length of encoding region was cloned into expressing vector pcDNA3.After identification by restriction enzyme digestion,PCR and sequencing,the recombinant plasmid was transfected into NIH3T3 cells with calcium phosphate-DNA precipitate method.A stably-transfected cell line was established by G418 selection.Extraneous gene integration was identified by PCR.Expression of DAF at both mRNA and protein levels was analyzed by RT-PCR,Western blot and indirect immunofluorescence microscopy.Results：The eukaryotic expression vector pcDNA3-DAF was successfully constructed and the DAF gene was transfected stably into NIH3T3 cells,a stably-transfected cell line was established and DAF was efficiently expressed on the surface of transfected NIH3T3 cells.Human DAF cDNA was integrated into NIH3T3 pcDNA3-DAF genomic DNA after continuous 30 times passages,indicating that NIH3T3 pcDNA3-DAF was stable cell line.Conclusion：The establishment of the stably-transfected cell line and the expression of the target gene provide a base for further studies on the function of the DAF and the cooperative fashion among different human complement regulatory proteins in alleviating the complement-mediated cytolysis.