Abstract
The invention relates to a system for over-expressing target protein. The system for over-expressing target protein includes a DHFR-deficient CHO cell, an antifolate analogue, a target protein expression plasmid and a CRISPRi plasmid, wherein the target protein expression plasmid includes a target protein expression cassette and a DHFR expression cassette, and the CRISPRi plasmid includes a gRNA cassette and a dCas9 expression cassette. The system for over-expression target protein can significantly enhance target protein production and shorten time for gene amplification.