Large-scale screening of yeast mutants for sensitivity to the IMP dehydrogenase inhibitor 6-azauracil

• Type of Material: Article
• Authors: Linda Riles, Washington University; Randal J. Shaw, Emory University; Mark Johnston, Washington University; Daniel Reines, Emory University
• Language: English
• Date: 2004-02
• Publisher: Wiley: 12 months
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2004 John Wiley & Sons, Ltd.
• Final Published Version (URL): http://onlinelibrary.wiley.com/doi/10.1002/yea.1068/abstract
• Title of Journal or Parent Work: Yeast
• ISSN: 0749-503X
• Volume: 21
• Issue: 3
• Start Page: 241
• End Page: 248
• Grant/Funding Information: This work was supported by NIH Grant GM46331 (to D.R.) and by funds awarded to M.J. by the James S. McDonnell Foundation.
• Keywords: azauracil; yeast deletants; mycophenolic acid; transcription elongation
• Research Categories: Biology, Genetics; Chemistry, Biochemistry

Abstract

Mutations in several genes encoding components of the RNA polymerase II elongation machinery render S. cerevisiae cells sensitive to the drug 6-azauracil (6AU), an inhibitor of IMP dehydrogenase and orotidylate decarboxylase. It is thought that a reduction in nucleotide levels following drug treatment causes transcriptional elongation to be more dependent on a fully functional RNA polymerase. To gain insight into the basis of the 6AU-sensitive phenotype and discern its specificity, we screened almost 3000 deletion mutants for growth in the presence of drug; 42 (1.5%) were reproducibly sensitive to the drug. The sensitive mutants included several missing known transcription elongation factors, but the majority were in genes involved in other cellular processes. Not all of the 6AU-sensitive strains displayed cross-sensitivity to mycophenolic acid (MPA), another drug that inhibits IMP dehydrogenase and has been employed as a screening agent for elongation mutants, showing that these two drugs are mechanistically distinct. Several of the mutants were tested for the ability to induce transcription of IMP dehydrogenase-encoding genes, in response to 6-AU and MPA treatment. As expected, mutants defective in transcriptional elongation factors were unable to fully induce IMPDH expression. However, most of the 6AU-sensitive strains had normal levels of IMPDH expression. Thus, although 6AU-sensitivity often results from defects in the elongation machinery, mutations that compromise processes other than transcription and induction of IMPDH also lead to sensitivity to this drug.