Global expression analysis in the yeast Lachancea (Saccharomyces) kluyveri revealed new URC genes involved in pyrimidine catabolism.

摘要

Pyrimidines are important nucleic acid precursors which are constantly synthesized, degraded and rebuilt in the cell. Four degradation pathways, two of which are found in eukaryotes, have been described. One of them, the URC pathway, has been initially discovered in our laboratory in the yeast Lachancea kluyveri.Here we present the global changes in gene expression in L. kluyveri, in response to different nitrogen sources, including uracil, uridine, dihydrouracil and ammonia. The expression pattern of the known URC genes, URC1-6, helped to identify nine putative novel URC genes with a similar expression pattern. The microarray analysis provided evidence that both the URC and PYD genes, are under nitrogen catabolite repression in L. kluyveri, and induced by uracil or dihydrouracil, respectively. We determined the function of URC8, which was found to catalyze the reduction of malonate semialdehyde to 3-hydroxypropionate, the final degradation product of the pathway. The other eight genes studied were all putative permeases. Our analysis of double deletion strains showed that the Lk Fui1p transported uridine, just like its homolog in Saccharomyces cerevisiae, but we demonstrated that is was not the only uridine transporter in L. kluyveri. We also showed that the L. kluyveri homologs of DUR3 and FUR4 do not have the same function as in S. cerevisiae, where they transport urea and uracil, respectively. In L. kluyveri, both these deletion strains grew normally on uracil and urea.