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Expression and amplification of cloned rat liver tyrosine aminotransferase in nonhepatic cells
Author(s) -
Kohli Kulwant K.,
Stellwagen Robert H.
Publication year - 1990
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041420124
Subject(s) - tyrosine aminotransferase , chinese hamster ovary cell , microbiology and biotechnology , biology , transfection , cell culture , rous sarcoma virus , tyrosine , complementary dna , hamster , enzyme , virus , gene , virology , biochemistry , enzyme inducer , genetics
A full‐length cDNA for the rat liver enzyme tyrosine aminotransferase has been used to construct mammalian expression vectors by recombinant DNA techniques. These vectors, which have employed either a simian virus 40 or a Rous sarcoma virus promoter, were transfected into a variety of nonhepatic mammalian cell lines in culture. Transient expression of tyrosine aminotransferase was readily observed after transfection into monkey COS cells and mouse L cells. Stable clones that express cloned tyrosine aminotransferase have been isolated from mouse L cells, hamster Wgla fibroblasts, and Chinese hamster ovary (CHO) cells. A vector capable of expressing both tyrosine aminotransferase and dihy‐drofolate reductase was stimulated to undergo amplification by treatment with methotrexate in a CHO cell line deficient in the latter enzyme. Levels of tyrosine aminotransferase as much as 50‐fold higher than typically seen in glucocorticoid‐induced hepatoma cells were achieved in some CHO clones by this technique. The tyrosine aminotransferase produced at these highly amplified levels appeared structurally normal and had no major harmful effects on the cells.