[Construction of miRNA sponge targeting miR-20a and stable expression in Jurkat leukemia cell line]

This study was aimed to construct miRNA sponge targeting miR-20a and to establish a stable cell line Jurkat-S, paving the way for further research on function of miR-20a and application of RNAi in gene therapy. One pair of two-repeated oligonucleotide sequences containing bulged sites that are mispaired opposite miR-20a positions 9-12 was designed and synthesized with enzyme cutting sites. The annealed oligonucleotide fragments were subcloned into pCDNA3.0-L expressing vector. After double-enzyme cutting, the vector was ligated to the annealed oligonucleotide fragments again. Enzyme cutting and luciferase activity assay were performed for identification after four repeats. Then the ligated fragment was subcloned to lentivirus expressing vector. Virus particles were collected after the control or sponge vectors were co-transfected with the psPAX2 packaging plasmid and the envelope plasmid pMD2.G into HEK-293T cells using Lipofectamine 2000. The Jurkat cells were transfused with recombinant lentivirus-transfusing units plus 6 µg/ml of Polybrene. Real-time PCR and Western blot were used to detect the mRNA and protein expression of P21 and E2F1 after lentivirus transfusion respectively. As a result, luciferase activity assay demonstrated that the sponge targeting miR-20a was constructed successfully and the virus was packaged in 293T. The titer of virus was 5×10(7) TU/ml. Stable transfected Jurkat-S cell line was established. As was expected, the mRNA and protein level of P21 and E2F1 was upregulated significantly in Jurkat-S cells. It is concluded that the miR-20a sponge is constructed successfully, and Jurkat-S stable cell line is established, in which the expression of miR-20a is inhibited stably.