title: Isolation of the amplified dihydrofolate reductase domain from methotrexate-resistant Chinese hamster ovary cells.
abstract: We isolated overlapping recombinant cosmids that represent the equivalent of two complete dihydrofolate reductase amplicon types from the methotrexate-resistant CHO cell line CHOC400. The type I amplicons are 260 kilobases long, are arranged in head-to-tail fashion, and represent 10 to 15% of the amplicons in the CHOC400 genome. The type II amplicons are 220 kilobases long, are arranged in head-to-head and tail-to-tail configurations, and constituted the majority of the remaining amplicons in CHOC400 cells. The type II amplicon sequences are represented entirely within the type I unit. These are the first complete amplicons to be cloned from a mammalian cell line.
mesh_terms: D000818:Animals; D002460:Cell Line; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D006224:Cricetinae; D004351:Drug Resistance; D005784:Gene Amplification; D005796:Genes; D008727:Methotrexate / Q000494:pharmacology*; D012093:Replicon; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*
chemical_list: D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate