The ribonucleotide reductase inhibitor Sml1 is a new target of the Mec1/Rad53 kinase cascade during growth and in response to DNA damage.
The evolutionarily conserved protein kinases Mec1 and Rad53 are required for checkpoint response and growth. Here we show that their role in growth is to remove the ribonucleotide reductase inhibitor Sml1 to ensure DNA replication. Sml1 protein levels fluctuate during the cell cycle, being lowest during S phase. The disappearance of Sml1 protein in S phase is due to post-transcriptional regulation and is associated with protein phosphorylation. Both phosphorylation and diminution of Sml1 require MEC1 and RAD53. More over, failure to remove Sml1 in mec1 and rad53 mutants results in incomplete DNA replication, defective mitochondrial DNA propagation, decreased dNTP levels and cell death. Interestingly, similar regulation of Sml1 also occurs after DNA damage. In this case, the regulation requires MEC1 and RAD53, as well as other checkpoint genes. Therefore, Sml1 is a new target of the DNA damage checkpoint and its removal is a conserved function of Mec1 and Rad53 during growth and after damage.
Zhao
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Department of Genetics and Development, Columbia University, College of Physicians and Surgeons, 701 West 168th Street, New York, NY 10032, USA.
Chabes
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A
Domkin
V
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Thelander
L
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Rothstein
R
R
D018797:Cell Cycle Proteins; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects / Q000528:radiation effects; D004261:DNA Replication / Q000187:drug effects / Q000528:radiation effects; D004271:DNA, Fungal / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D004791:Enzyme Inhibitors; D005656:Fungal Proteins / Q000378:metabolism*; D005720:Gamma Rays; D005838:Genotype; D006918:Hydroxyurea / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D012264:Ribonucleotide Reductases / Q000037:antagonists & inhibitors*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D014466:Ultraviolet Rays
D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; C115052:SML1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D012264:Ribonucleotide Reductases; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C088937:MEC1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; C067022:RAD53 protein, S cerevisiae; D006918:Hydroxyurea