Saccharomyces cerevisiae transcription elongation mutants are defective in PUR5 induction in response to nucleotide depletion.
IMP dehydrogenase (IMPDH) is the rate-limiting enzyme in the de novo synthesis of guanine nucleotides. It is a target of therapeutically useful drugs and is implicated in the regulation of cell growth rate. In the yeast Saccharomyces cerevisiae, mutations in components of the RNA polymerase II (Pol II) transcription elongation machinery confer increased sensitivity to a drug that inhibits IMPDH, 6-azauracil (6AU), by a mechanism that is poorly understood. This phenotype is thought to reflect the need for an optimally functioning transcription machinery under conditions of lowered intracellular GTP levels. Here we show that in response to the application of IMPDH inhibitors such as 6AU, wild-type yeast strains induce transcription of PUR5, one of four genes encoding IMPDH-related enzymes. Yeast elongation mutants sensitive to 6AU, such as those with a disrupted gene encoding elongation factor SII or those containing amino acid substitutions in Pol II subunits, are defective in PUR5 induction. The inability to fully induce PUR5 correlates with mutations that effect transcription elongation since 6AU-sensitive strains deleted for genes not related to transcription elongation are competent to induce PUR5. DNA encompassing the PUR5 promoter and 5' untranslated region supports 6AU induction of a luciferase reporter gene in wild-type cells. Thus, yeast sense and respond to nucleotide depletion via a mechanism of transcriptional induction that restores nucleotides to levels required for normal growth. An optimally functioning elongation machinery is critical for this response.
Shaw
R J
RJ
Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Reines
D
D
D004790:Enzyme Induction / Q000187:drug effects; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects*; D005800:Genes, Fungal / Q000235:genetics; D017930:Genes, Reporter; D006147:Guanine / Q000494:pharmacology; D007168:IMP Dehydrogenase / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D009154:Mutation; D009173:Mycophenolic Acid / Q000494:pharmacology; D009711:Nucleotides / Q000096:biosynthesis / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000235:genetics; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D035165:Transcription Factors, General; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics*; D035602:Transcriptional Elongation Factors; D014498:Uracil / Q000031:analogs & derivatives / Q000494:pharmacology
D009711:Nucleotides; D012331:RNA, Fungal; D012333:RNA, Messenger; D014157:Transcription Factors; D035165:Transcription Factors, General; D035602:Transcriptional Elongation Factors; C018648:transcription factor S-II; D014498:Uracil; D006147:Guanine; D007168:IMP Dehydrogenase; D012319:RNA Polymerase II; D009173:Mycophenolic Acid; C100248:azauracil