[Construction and application of lentivirus overexpression vector with two labeling genes fused with CopGFP and Puro^R]

Objective: To construct the lentivirus overexpression vector with two label genes fused with CopGFP and Puro^R and to detect the emission of green fluorescence as well as resistance to puromycin in liver cancer cells infected with lentivirus packaged with the above vector. Methods: Firstly, two fragments containing copGFP and Puro^R coding sequences were amplified from pCDH-CMV-MCS-copGFP and pLKO.1 respectively; secondly, the two amplified regions were fused with each other by recombinant PCR; thirdly, the fusion DNA fragment was cut and inserted into pCDH-CMV-MCS-copGFP vector, which was linearized with the same restriction endonuclease as used to digest fusion DNA fragment: BamH Ⅰ and Sal Ⅰ. The fusion region in the constructed vector was confirmed by DNA sequencing. The checked vector was co-transfected with package assistant plasmids, namely PLP1, PLP2 and VSVG into in 293T cells and the culture supernatant was subjected to centrifuge and infect liver cancer MHCC97H cells, which were then used to detect their resistance to puromycin (infected cells were treated with 1 mg/ml puromycin for 7 days after infection) and to observe green fluorescence emission in microscope. To determine its efficiency in expressing foreign target protein, the Sp1 coding region was inserted into the MCS sites of the vector, and Sp1 mRNA and protein expression levels were compared with the vehicle vector by RT-qPCR and Western blot. Results: The lentivirus overexpression vector with two label genes fused with CopGFP and Puro^R was successfully constructed, and the liver cancer cells infected with lentivirus packaged with the vector expressing two labeling genes fused with CopGFP and Puro^Rshowed both emission of green fluorescence and resistance to puromycin simultaneously, while cells containing with the vector inserted with Sp1 coding region improved Sp1 mRNA level with 3.3 fold and protein level with 2.2 fold higher in comparison with cells containing the vehicle vector (P＜0.01). Conclusion: The fused label genes consisting of copGFP and Puro^R are correctly cloned into the lentivirus vector and confer cells with the ability to emission of green fluorescence and resistance to puromycin, besides, the vector may promote the expression of the target gene with long coding sequence.