Amplification of plasmid (L factor) DNA and increased production of a plasmid gene product (gamma-interferon) in mouse L cells.
It has previously been reported that composite DNAs derived from L factor, a polyoma-related mammalian plasmid, can be established in several mouse cell lines after transfection. Here, we report that the copy number of a plasmid composite DNA consisting of L factor, pBR DNA, dihydrofolate reductase (dhfr) gene, and gamma-interferon (gamma-IFN) gene was increased more than 10-fold after two successive adaptations of the plasmid-bearing mouse L cells to increasing concentrations of methotrexate (MTX), an inhibitor of dhfr. The structure of the amplified L factor plasmid remained intact during prolonged cell culture, but the copy number remained to be amplified only when the selective pressure (presence of MTX in the medium) has been exerted during the culture. Cells bearing the amplified plasmid produced a higher level of gamma-IFN compared with the original clone, which was likely to be derived from the plasmid gamma-IFN gene amplified along with L factor and the dhfr gene.
Yoshimura
H
H
Taisho Pharmaceutical Company, Ltd., Saitama, Japan.
Ikeda
Y
Y
Fujiwara
J
J
Nishimori
K
K
Kotoji
K
K
Tamaki
S
S
Hanada
K
K
Oishi
M
M
D000818:Animals; D004274:DNA, Recombinant / Q000235:genetics; D005784:Gene Amplification; D005822:Genetic Vectors; D007371:Interferon-gamma / Q000096:biosynthesis*; D007739:L Cells / Q000187:drug effects / Q000378:metabolism; D008727:Methotrexate / Q000494:pharmacology; D051379:Mice; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis*; D012641:Selection, Genetic; D013762:Tetrahydrofolate Dehydrogenase / Q000096:biosynthesis / Q000235:genetics
D004274:DNA, Recombinant; D011993:Recombinant Fusion Proteins; D007371:Interferon-gamma; D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate