人白细胞介素-21 cDNA克隆及其在大肠杆菌系统的表达

目的：克隆人细胞因子IL-2l全长cDNA及其在大肠杆菌中表达，并进一步检测其表达产物的功能。方法：抽取外周血，分离淋巴细胞；抗CD3抗体刺激后，提取总RNA，通过RT-PCR获得两个部分重叠的IL-21 cDNA片段(分别为5′端242bp，3′端425bp)，重组PCR扩增出IL-21全长cDNA：DNA测序正确后，将成熟IL-21 cDNA的编码框序列构建到原核表达载体pET28a( )中。卡那霉素平板筛选及PCR鉴定，挑出阳性克隆进行扩增、转化大肠杆菌进行IPTG诱导表达：SDS—PAGE、Western blotting鉴定，亲和层析分离纯化得到M，为18600的带有组氨酸标签重组人IL-21融合蛋白。透析法重折叠复性，MTT法测定其对T细胞增殖活性。结果：成功获得人IL-21全长cDNA，并以包涵体形式表达于大肠杆菌中。重折叠后的rhIL-21融合蛋白具有与抗CD3抗体共刺激T细胞增殖作用。结论：获得具有生物学活性的rhIL-21细胞因子，为进一步研究其功能奠定基础。

Cloning and expression of human interleukin-21 cDNA in E.coli

AIM: To clone full length cDNA of human interleukin-21 (IL-21) and express it in E.coli. METHODS: Total RNA was isolated from peripheral lymphocyte stimulated with anti-CD3 antibody. 5' and 3' terminal fragments of IL-21 gene (242 bp and 425 bp fragments respectively) were amplified using RT-PCR. The full length IL-21 cDNA was amplified by recombination PCR from the products of RT-PCR.The expression plasmid pET28a(+)-IL21 was constructed by inserting IL-21 cDNA into pET28a(+)and then was transformed into BL21(DE3). Expression of hIL-21 was induced by IPTG at 37 degrees Celsius for 5 h. The target protein was purified through Ni(2+)-chelating Sepharose Fast Flow. Purified rhIL-21 was refolded by using dialysis method. And the bioactivity was detected by MTT on costimulating the T cell proliferation with anti-CD3. RESULTS: IL-21 was cloned and expressed in E.coli successfully. SDS-PAGE analysis showed the IL-21 was expressed in the form of insoluble inclusion body. The refolded rhIL-21 could stimulate the proliferation of mature human T-cells in the presence of anti-CD3. CONCLUSION: The rhIL-21 with bioactivity was obtained, which lays the foundation for study of its function.