OBJECTIVETo construct a lentiviral vector of miR-335 gene and verify the target gene of miR-335.

METHODSThe precursor sequence of miR-335 gene was amplified from the genomic DNA by PCR and cloned into the lentiviral vector PLVTHM labeled with GFP. Real-time quantitative RT-PCR was used to detect miR-335 and RASA1 expression in different colorectal cancer cell lines. A recombinant vector psiCHECK-2-RASA1 containing RASA1 3'UTR was constructed followed by site-directed mutagenesis of RASA1 3'UTR to establish the vector psiCHECK-2-RASA1-Mut. Co-transfection of hsa-mir-335 or a NC with these recombined vectors in HEK293A and SW480 cells was performed, and dual-luciferase reporter assay was utilized to examine the changes in luciferase activities. The recombinant PLVTHM-miR335 plasmid was packaged into mature lentivirus by 293FT cells and used to infect SW620 cells. Flow cytometry was employed for sorting the GFP+ cells. The expression of miR-335 and RASA1 were determined by qRT-PCR, and Western blotting was used to detect the expression of RASA1 protein in SW620 cell lines.

RESULTSThe recombinant lentiviral vector PLVTHM-miR335, psiCHECK-2-RASA1 and the mutation expression vector psiCHECK-2-RASA1-Mut were successfully constructed. Dual-luciferase reporter assay showed that miR-335 decreased luciferase activity in cells co-transfected with psiCHECK-2-RASA1. The expression of miR-335 in SW620 cells infected with the lentivirus PLVTHM-miR335 was significantly increased, but the expression of RASA1 showed only slight changes. Overexpression of miR-335 suppressed the expression of RASA1 protein in SW620 cells.

CONCLUSIONWe have successfully constructed the lentiviral vector containing mir-335 gene and a SW620 cell line with miR-335 overexpression. MiR-335 can suppress RASA1 gene expression by targeting the specific sequence of RASA1 3'UTR.