title: Control of ribonucleotide reductase localization through an anchoring mechanism involving Wtm1.
abstract: The control of deoxyribonucleotide levels is essential for DNA synthesis and repair. This control is exerted through regulation of ribonucleotide reductase (RNR). One mode of RNR regulation is differential localization of its subunits. In Saccharomyces cerevisiae, the catalytic subunit hererodimer, Rnr2/Rnr4, is localized to the nucleus while its regulatory subunit, Rnr1, is cytoplasmic. During S phase and in response to DNA damage, Rnr2-Rnr4 enters the cytoplasm, where it presumably combines with Rnr1 to form an active complex. The mechanism of its nuclear localization is not understood. Here, we report the isolation of the WTM (WD40-containing transcriptional modulator) proteins as regulators of Rnr2/Rnr4 localization. Overproduction of Wtm2 increased Rnr2/Rnr4. Deletion of WTM1, a homolog of WTM2, leads to the cytoplasmic localization of Rnr2/Rnr4, and increased hydroxyurea (HU)-resistance in mec1 mutants. Wtm1 binds Rnr2/4 complexes and release them to the cytoplasm in response to DNA damage. Forced localization of Wtm1 to the nucleolus causes Rnr2/Rnr4 complexes to relocalize to the nucleolus. Thus, Wtm1 acts as a nuclear anchor to maintain nuclear localization of Rnr2/4 complexes outside of S phase. In the presence of DNA damage this association is disrupted and Rnr2/Rnr4 become cytoplasmic, where they join with Rnr1 to form an intact complex.
authors.affiliation: Harvard University Medical School, Department of Genetics, Brigham and Women's Hospital, Center for Genetics and Genomics, Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA.
authors.forename: Yang David
authors.initials: YD
authors.lastname: Lee
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Elledge
mesh_terms: D002453:Cell Cycle; D002466:Cell Nucleolus / Q000378:metabolism; D004249:DNA Damage; D005455:Fluorescent Antibody Technique; D006918:Hydroxyurea / Q000378:metabolism / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D012264:Ribonucleotide Reductases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D013489:Suppression, Genetic; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D021122:Protein Subunits; D012097:Repressor Proteins; C115052:SML1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C107277:Wtm1 protein, S cerevisiae; C107278:Wtm2 protein, S cerevisiae; D012264:Ribonucleotide Reductases; C088937:MEC1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D006918:Hydroxyurea