title: Isolation of the thymidylate synthetase gene (TMP1) by complementation in Saccharomyces cerevisiae.
abstract: The structural gene (TMP1) for yeast thymidylate synthetase (thymidylate synthase; EC 2.1.1.45) was isolated from a chimeric plasmid bank by genetic complementation in Saccharomyces cerevisiae. Retransformation of the dTMP auxotroph GY712 and a temperature-sensitive mutant (cdc21) with purified plasmid (pTL1) yielded Tmp+ transformants at high frequency. In addition, the plasmid was tested for the ability to complement a bacterial thyA mutant that lacks functional thymidylate synthetase. Although it was not possible to select Thy+ transformants directly, it was found that all pTL1 transformants were phenotypically Thy+ after several generations of growth in nonselective conditions. Thus, yeast thymidylate synthetase is biologically active in Escherichia coli. Thymidylate synthetase was assayed in yeast cell lysates by high-pressure liquid chromatography to monitor the conversion of [6-3H]dUMP to [6-3H]dTMP. In protein extracts from the thymidylate auxotroph (tmp1-6) enzymatic conversion of dUMP to dTMP was barely detectable. Lysates of pTL1 transformants of this strain, however, had thymidylate synthetase activity that was comparable to that of the wild-type strain.
mesh_terms: D004262:DNA Restriction Enzymes; D004274:DNA, Recombinant; D004926:Escherichia coli / Q000235:genetics; D005796:Genes; D005816:Genetic Complementation Test; D008780:Methyltransferases / Q000235:genetics*; D010641:Phenotype; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D013940:Thymidylate Synthase / Q000235:genetics* / Q000378:metabolism; D014170:Transformation, Genetic
chemical_list: D004274:DNA, Recombinant; D008780:Methyltransferases; D013940:Thymidylate Synthase; D004262:DNA Restriction Enzymes