The gene for the nucleocapsid (N) protein of canine distemper virus was cloned into the pMD-18T vector, and positive recombinant plasmids were obtained by enzyme digestion and sequencing. After digestion by both EcoRI and KpnI, the plasmid was directionally cloned into the eukaryotic expression vector pcDNA; the positive clone pcDNA-N was screened by electrophoresis and then transfected into COS-7 cells. Immunofluorescence analysis results showed that the canine distemper virus N protein was expressed in the cytoplasm of transfected COS-7 cells.
We constructed the human dickkopf 1 (DKK1) eukaryotic expression plasmid and expressed, purified, and identified its expression product. We extracted cancer cells from cervical cancer tissue, followed by extraction of mRNA. Reverse transcription-polymerase chain reaction was conducted to obtain DKK1 gene fragments. Using these fragments, we prepared the recombinant plasmid pCMV-HA2/DKK1. The recombinant plasmid was restriction enzyme-digested and sequenced, and using liposome vectors, was transiently transfected into Free-Style 293-F cells (serum-free medium).