Abstract: The present invention relates to a recombinant expression vector for an animal cell containing a dihydrofolate reductase (DHFR) coding nucleotide sequence operatively linked to a DHFR promoter, to an animal cell line transformed by the vector, and to a method for preparing a target protein using the same. As compared with existing animal cell expression vectors, the vector of the present invention enables an effective screening of a cell line clone in which foreign genes are amplified together with DHFR genes even at a much lower methotrexate concentration. The present invention exhibits excellent effects in cell line preparation as high-productivity cell lines can be ensured in a short time through the use of a lower concentration of methotrexate in the process of protein production cell line establishment.

Abstract: The present invention relates to a recombinant expression vector for an animal cell containing a dihydrofolate reductase (DHFR) coding nucleotide sequence operatively linked to a DHFR promoter, to an animal cell line transformed by the vector, and to a method for preparing a target protein using the same. As compared with existing animal cell expression vectors, the vector of the present invention enables an effective screening of a cell line clone in which foreign genes are amplified together with DHFR genes even at a much lower methotrexate concentration. The present invention exhibits excellent effects in cell line preparation as high-productivity cell lines can be ensured in a short time through the use of a lower concentration of methotrexate in the process of protein production cell line establishment.

Abstract: A switchover device switches over a double module between first and second modules manually or automatically, in which the control signals and switchover signals are generated with of the logic combination circuits and relays, to simplify signal processing of the system.