title: Regulation of a eukaryotic gene by GTP-dependent start site selection and transcription attenuation.
abstract: Guanine nucleotide negatively regulates yeast inosine monophosphate dehydrogenase (IMPDH) mRNA synthesis by an unknown mechanism. IMPDH catalyzes the first dedicated step of GTP biosynthesis, and feedback control of its expression maintains the proper balance of purine nucleotides. Here we show that RNA polymerase II (Pol II) responds to GTP concentration. When GTP is sufficient, Pol II initiates transcription of the IMPDH gene (IMD2) at TATA box-proximal "G" sites, producing attenuated transcripts. When GTP is deficient, Pol II initiates at an "A" further downstream, circumventing the regulatory terminator to produce IMPDH mRNA. A major determinant for GTP concentration-dependent initiation at the upstream sites is the presence of guanine at the first and second positions of the transcript. Mutations in the Rpb1 subunit of Pol II and in TFIIB disrupt IMD2 regulation by altering start site selection. Thus, Pol II initiation can be regulated by the concentration of initiating nucleotide.
authors.affiliation: Cellular and Molecular Biology Graduate Program, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA.
authors.forename: Jason N
authors.initials: JN
authors.lastname: Kuehner
authors.forename: David A
authors.initials: DA
authors.lastname: Brow
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics; D001483:Base Sequence; D018387:Codon, Initiator / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects*; D005800:Genes, Fungal; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D007168:IMP Dehydrogenase / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009713:Nucleotidyltransferases / Q000235:genetics; D012319:RNA Polymerase II / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D024363:Transcription Initiation Site; D014158:Transcription, Genetic / Q000187:drug effects*
chemical_list: D020121:5' Untranslated Regions; D018387:Codon, Initiator; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D006160:Guanosine Triphosphate; C477283:IMD2 protein, S cerevisiae; D007168:IMP Dehydrogenase; D009713:Nucleotidyltransferases; D012319:RNA Polymerase II; C511736:RPB1 protein, S cerevisiae; C026917:mannose 1-phosphate guanylyltransferase