Amplified dihydrofolate reductase genes are localized to a homogeneously staining region of a single chromosome in a methotrexate-resistant Chinese hamster ovary cell line

J. H. Nunberg, R. J. Kaufman, R. T. Schimke, G. Urlaub, L. A. Chasin

Research output: Contribution to journalArticlepeer-review

Abstract

Methotrexate resistant Chinese hamster ovary cells selected for high resistance by progressive increments of methotrexate in the culture medium have levels of dihydrofolate reductase (tetrahydrofolate dehydrogenase, 7,8-dihydrofolate: NADP+ oxidoreductase, EC 1.5.1.3) 200 times that of sensitive cells and a corresponding increase in the number of copies of the dihydrofolate reductase gene. The resistant cells contain an expanded region on the second chromosome (homogeneously staining region) that is not present in sensitive cells. In situ hybridization of DNA complementary to dihydrofolate reductase mRNA shows that the dihydrofolate reductase genes are specifically localized to the homogeneously staining region of this chromosome in the resistant cells.

Original languageEnglish
Pages (from-to)5553-5556
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Volume75
Issue number11
DOIs
StatePublished - 1978

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