HPV-16 E4原核表达系统的建立和表达特性研究

目的克隆人乳头瘤病毒-16型(HPV-16) E4 基因( E4 ),构建E4蛋白表达重组工程菌,探索表达条件和鉴定表达产物特性.方法以临床HPV-16阳性宫颈炎患者上皮细胞提取物为模板,PCR扩增 E4 完整基因,并定向克隆到pET32a(+)原核表达质粒中,经双酶切和测序鉴定后转入大肠杆菌BL-21(DE3),获得工程菌(BL-21/E4).经IPTG诱导,表达蛋白用SDS-PAGE和Western blot鉴定.结果克隆到完整 E4 基因为342 bp,与HPV-16东亚型的同源性为99%,与其他HPV16型的同源性高于97%.在28 ℃和37 ℃,0.1 mmol/L的IPTG诱导18 h时,重组蛋白(rE4)表达量分别占菌体总蛋白的12.2%和12.8%;SDS-PAGE和Western blot证明rE4蛋白与表达载体的标签蛋白形成相对分子质量约34×103的可溶性融合蛋白(rE4/His).结论成功构建了表达带标签的融合重组蛋白(rE4/His)的重组大肠杆菌BL-21/E4表达系统,这为高纯度HPV-16 E4蛋白的制备和相关研究奠定了基础.

Analysis of Protein Expression Feature and Construction of Procaryotic Expression System for Human Papillomavirus Type 16 (HPV-16) E4 Gene

OBJECTIVE: To clone the E4 gene (E4) from human papillomavirus type 16(HPV-16), construct the engineering bacteria of prokaryotic expression, and explore the expression conditions and the characters of expression product. METHODS: The complete E4 gene was cloned by PCR from the sample cell extract of clinical cervical disease that was the positive HPV-16 confirmed by Real-PCR. The E4 DNA fragment was inserted into the pET32a(+) to construct a prokaryotic expression plasmid, called as pET32/E4. Then the expression plasmids were transferred into competent E. coli BL21 (DE3). Recombinant DNA was identified by Bgl II and Hind III digestion, and then sequencing. The recombine bacterium, BL21/E4, was induced with different IPTG concentrations at different temperatures. The expressed proteins were checked and analyzed by SDS-PAGE and Gel-Pro Analyzer 4. His-tag of BL21/E4 expression protein was hybridized to McAb. RESULTS: The E4 gene cloned by PCR was about 342 bp. The blasted result showed that the E4 gene had 99% homology of HVP-16 DNA sequence, the cloned E4 gene expression frame was the same as HVP-16 East Asia strain's. Compared with other HPV-16 strains in GenBank, the homology of E4 gene was above 97%. pET32/E4 could express recombinant E4 (rE4) in BL21. The highest expression, which was 12.2% or 12.8% of total bacterial proteins respectively, was gotten when BL21/E4 was induced by 0.1 mmol/L IPTG at 28 degrees C or 37 degrees C for 18 hours. The results of SDS-PAGE and Western blot showed the rE4 was expressed mainly to form the inclusion body, and to fuse with his-tag (rE4/His), that was soluble and had a molecular weight as about 34 KDa. CONCLUSION: We cloned successfully the E4 gene from HPV-16 and constructed the prokaryotic expression E. coli BL21/E4, which could expression rE4 protein fused with his-tag (rE4/His), effectively. The fused protein could react to McAb recognizing His-tag, which was convenience purified by affinity chromatography. The above research results built a good foundation for preparing the high grade of purity E4 protein and developing the relative study.