title: Enzyme regulation. IRBIT is a novel regulator of ribonucleotide reductase in higher eukaryotes.
abstract: Ribonucleotide reductase (RNR) supplies the balanced pools of deoxynucleotide triphosphates (dNTPs) necessary for DNA replication and maintenance of genomic integrity. RNR is subject to allosteric regulatory mechanisms in all eukaryotes, as well as to control by small protein inhibitors Sml1p and Spd1p in budding and fission yeast, respectively. Here, we show that the metazoan protein IRBIT forms a deoxyadenosine triphosphate (dATP)-dependent complex with RNR, which stabilizes dATP in the activity site of RNR and thus inhibits the enzyme. Formation of the RNR-IRBIT complex is regulated through phosphorylation of IRBIT, and ablation of IRBIT expression in HeLa cells causes imbalanced dNTP pools and altered cell cycle progression. We demonstrate a mechanism for RNR regulation in higher eukaryotes that acts by enhancing allosteric RNR inhibition by dATP.
authors.affiliation: Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA. arnaouta@mail.nih.gov.
authors.forename: Alexei
authors.initials: A
authors.lastname: Arnaoutov
authors.affiliation: Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Mary
authors.initials: M
authors.lastname: Dasso
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D003838:Deoxyadenine Nucleotides / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D037181:Lectins, C-Type / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D012264:Ribonucleotide Reductases / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: C470184:CLECL1 protein, human; D003838:Deoxyadenine Nucleotides; D037181:Lectins, C-Type; D008565:Membrane Proteins; D012264:Ribonucleotide Reductases; C026600:2'-deoxyadenosine triphosphate