Expression of murine dihydrofolate reductase complementary DNA in oocytes of Xenopus laevis.

1. Murine dihydrofolate reductase was produced efficiently in a Xenopus laevis oocyte that received microinjection of the dihydrofolate reductase mRNA. 2. Murine dihydrofolate reductase was produced under the direction of the plasmid pAdD26SVpA, which contains adenovirus major late promoter and the simian virus 40 T antigen gene for transcription initiation and murine dehydrofolate reductase complementary DNA fragment. 3. Injection of the plasmid pDHFR26, which contains murine dihydrofolate reductase complementary DNA and normal transcription initiation site segment in the 5' untranslational region, failed to produce proper translational products due to improper transcription.