Transfection with a cDNA encoding a Ser31 or Ser35 mutant human dihydrofolate reductase into Chinese hamster ovary and mouse marrow progenitor cells confers methotrexate resistance

Debabrata Banerjee, Barry I. Schweitzer, Matthias Volkenandt, Ming Xia Li, Mark Waltham, Shin Mineishi, Shi Cheng Zhao, Joseph R. Bertino

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Chinese hamster ovary (CHO) DHFR- cells were converted into the DHFR+ phenotype when they were transfected with a mammalian expression vector carrying human dihydrofolate reductase-encoding cDNAs (DHFR) containing a Ser31 or a Ser34 mutation. Furthermore, transfection of these mutants into wild-type CHO cells resulted in resistance to high levels of methotrexate (MTX), indicating that these human variants can act as dominant selectable markers. Southern blot analysis and polymerase chain reaction amplifications confirmed that the transfected plasmids were integrated into the CHO DNA. Gene copy number analysis revealed that both the Ser31 and the Ser34 mutants are amplifiable when grown in increasing concentrations of MTX. Retrovirus-mediated gene transfer of the Ser31 mutant into mouse marrow progenitor cells also resulted in MTX-resistant CFU-GM (colony-forming unit-granulocyte macrophage) cells.

Original languageEnglish
Pages (from-to)269-274
Number of pages6
Issue number2
Publication statusPublished - 25 Feb 1994
Externally publishedYes


  • DNA amplification
  • Gene transfer
  • PCR
  • sequence analysis

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