THE ORF YBL042 OF SACCHAROMYCES-CEREVISIAE ENCODES A URIDINE PERMEASE

The purpose of this work was to identify the function of an open readi ng frame called YBL042, found during the systematic sequencing of Sacc haromyces cerevisiae's chromosome II. The YBL042 gene product shows 70 % similarity with the uracil permease and the allantoin permease encod ed by FUR4 and DAL4, respectively. The mutation constructed by disrupt ion of this ORF is allelic to the FUI1 gene previously described as en coding the uridine permease but not cloned yet. A strain carrying the disrupted allele and a fui1 mutant exhibit the same phenotype as they do not grow on a medium containing uridine as the sole source of pyrim idines and as they are resistant to 10(-3) M 5-fluorouridine (5FUI), a toxic analog of uridine. Even though the FUI1 gene has a multicopy su ppressor effect on uracil transport, its product does not seem to be i nvolved in this transport, in contrast to the FUR4 gene product which is involved in uridine transport. Moreover, the FUI1 gene product does not play any role in allantoin transport. (C) 1998 Federation of Euro pean Microbiological Societies. Published by Elsevier Science B.V.