SPECIFIC BINDING OF HUMAN DIHYDROFOLATE-REDUCTASE PROTEIN TO DIHYDROFOLATE-REDUCTASE MESSENGER-RNA INVITRO

Dihydrofolate reductase (DHFR) is a critical enzyme in de novo purine and thymidylate biosynthesis. An RNA gel mobility shift assay was used to demonstrate a specific interaction between human recombinant DHFR protein and its corresponding DHFR mRNA. Incubation of DHFR protein wi th either its substrates, dihydrofolate or NADPH, or with an inhibitor , methotrexate, repressed its ability to interact with DHFR mRNA. An i n vitro rabbit reticulocyte lysate translation system was used to show that the addition of exogenous human recombinant DH FR protein to in vitro translation reactions specifically inhibited DHFR mRNA translati on. These studies suggest that the direct interaction between DHFR pro tein and its mRNA may be a mechanism for regulation of DHFR synthesis.