Abstract
The present disclosure relates to a system for over-expressing a target protein. The system for over-expressing the target protein includes a dihydrofolate reductase (DHFR)-deficient CHO cell, an antifolate analog, a target protein expression plasmid and a CRISPRi expression plasmid. The target protein expression plasmid includes a target protein expression cassette and a DHFR expression cassette. The CRISPRi expression plasmid includes a gRNA cassette and a dCas9 expression cassette. The present disclosure also relates to a method for over-expressing the target protein. The method for over-expressing the target protein includes constructing the target protein expression plasmid, constructing the CRISPRi expression plasmid, establishing a first stable cell line, establishing a second stable cell line and performing a gene amplification.