Weakening resistance marker for establishing a process of screening high-producing CHO cell lines / 中国药科大学学报

ABSTRACT

To optimize Chinese hamster ovary (CHO)expression system and establish a process of screening CHO cell lines with high productivity;neomycin-phosphotransferase (NPT)expressed by the resistance marker gene on the expression vector was mutated with amino acid D at 261 changed to G.After selection by culturing with G418;the survival rate of CHO cells bearing mutant-NPT was significantly lower than that of the cells bear-ing wide type NPT.An enhanced green fluorescent protein (EGFP)was genetically linked to the N terminus of the IgG1 Fc fragment part to generate an EGFP-Fc fusion protein regarded as a report gene;which verified that the resistance of mutant-NPT to G418 was weakened.By comparing fluorescence assay of EGFP intensity in stable transfections after selection with the same concentration of G418 for 3 weeks;mutant-selected pools expressed more exogenous protein than the WT-selected pools.Therefore;the ratio of high producers in a transfected cell population greatly increased.