The ribonucleotide reductase inhibitor Sml1 is a new target of the Mec1/Rad53 kinase cascade during growth and in response to DNA damage

• Published in: The EMBO journal 2001-07, Vol.20 (13), p.3544-3553
• Main Authors: Zhao, Xiaolan, Chabes, Andrei, Domkin, Vladimir, Thelander, Lars, Rothstein, Rodney
• Format: Article
• Language: English
• Subjects: Cell Cycle Proteins; checkpoint; Checkpoint Kinase 2; DNA Damage; DNA Repair - drug effects; DNA Repair - radiation effects; DNA Replication - drug effects; DNA Replication - radiation effects; DNA, Fungal - drug effects; DNA, Fungal - genetics; DNA, Fungal - radiation effects; Enzyme Inhibitors; Fungal Proteins - metabolism; Gamma Rays; Genotype; Hydroxyurea - pharmacology; Intracellular Signaling Peptides and Proteins; Mec1; MEC1 gene; Mec1 protein; Mitochondrial DNA; Protein Kinases - metabolism; protein phosphorylation; Protein Serine-Threonine Kinases; Rad53; RAD53 gene; Rad53 kinase; ribonucleotide reductase; Ribonucleotide Reductases - antagonists & inhibitors; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - growth & development; Saccharomyces cerevisiae - physiology; Saccharomyces cerevisiae Proteins; Sml1 protein; Ultraviolet Rays
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1093/emboj/20.13.3544

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.