title: Overexpression of SNG1 causes 6-azauracil resistance in Saccharomyces cerevisiae.
abstract: The mechanism of action of 6AU, a growth inhibitor for many microorganisms causing depletion of intracellular nucleotide pools of GTP and UTP, is not well understood. To gain insight into the mechanisms leading to 6AU resistance, and in an attempt to uncover novel genes required for this resistance, we undertook a high-copy-number suppressor screening to identify genes whose overexpression could repair the 6AU(S) growth defect caused by rpb1 mutations in Saccharomyces cerevisiae. We have identified SNG1 as a multicopy suppressor of the 6AU(S) growth defect caused by the S. cerevisiae rpb1 mutant. The mechanism by which Sng1 causes 6AU resistance is independent of the transcriptional elongation and of the nucleotide-pool regulation through Imd2 and Ura2, as well as of the Ssm1-mediated 6AU detoxification. This resistance to 6AU is not extended to other uracil analogues, such as 5-fluorouracil, 5FU. In addition, our results suggest that 6AU enters S. cerevisiae cells through the uracil permease Fur4. Our results demonstrate that Sng1 is localised in the plasma membrane and evidence SNG1 and FUR4 genes as determinants of resistance and susceptibility to this inhibitory compound, respectively. Taken together, these results show new mechanisms involved in the resistance and susceptibility to 6AU.
authors.affiliation: Departamento de Biología Experimental, Universidad de Jaén, Spain.
authors.forename: Ma Carmen
authors.initials: MC
authors.lastname: García-López
authors.forename: Ma Carmen
authors.initials: MC
authors.lastname: Mirón-García
authors.forename: Ana I
authors.initials: AI
authors.lastname: Garrido-Godino
authors.forename: Carlos
authors.initials: C
authors.lastname: Mingorance
authors.forename: Francisco
authors.initials: F
authors.lastname: Navarro
mesh_terms: D000963:Antimetabolites / Q000494:pharmacology*; D025141:Drug Resistance, Fungal; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014498:Uracil / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000963:Antimetabolites; D008565:Membrane Proteins; D012333:RNA, Messenger; C093629:SNG1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014498:Uracil; C100248:azauracil