scholarly journals Mechanism of Caffeine-Induced Checkpoint Override in Fission Yeast

2000 ◽  
Vol 20 (12) ◽  
pp. 4288-4294 ◽  
Author(s):  
Bettina A. Moser ◽  
Jean-Marc Brondello ◽  
Beth Baber-Furnari ◽  
Paul Russell
Keyword(s):  
Dna Damage ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Protein Kinases ◽  
Molecular Target ◽  
S Phase ◽  
Dna Damage Checkpoint ◽  
Mitotic Checkpoints ◽  
Direct Activation

ABSTRACT Mitotic checkpoints restrain the onset of mitosis (M) when DNA is incompletely replicated or damaged. These checkpoints are conserved between the fission yeast Schizosaccharomyces pombe and mammals. In both types of organisms, the methylxanthine caffeine overrides the synthesis (S)-M checkpoint that couples mitosis to completion of DNA S phase. The molecular target of caffeine was sought in fission yeast. Caffeine prevented activation of Cds1 and phosphorylation of Chk1, two protein kinases that enforce the S-M checkpoint triggered by hydroxyurea. Caffeine did not inhibit these kinases in vitro but did inhibit Rad3, a kinase that regulates Cds1 and Chk1. In accordance with this finding, caffeine also overrode the G2-M DNA damage checkpoint that requires Rad3 function. Rad3 coprecipitated with Cds1 expressed at endogenous amounts, a finding that supports the hypothesis that Rad3 is involved in direct activation of Cds1.

scholarly journals The Fission Yeast Rad32 (Mre11)-Rad50-Nbs1 Complex Is Required for the S-Phase DNA Damage Checkpoint

2003 ◽  
Vol 23 (18) ◽  
pp. 6564-6573 ◽  
Author(s):  
Charly Chahwan ◽  
Toru M. Nakamura ◽  
Sasirekha Sivakumar ◽  
Paul Russell ◽  
Nicholas Rhind
Keyword(s):  
Dna Damage ◽  
Fission Yeast ◽  
Chromosome Instability ◽  
S Phase ◽  
Comparative Genomic ◽  
Dna Damage Checkpoint ◽  
Checkpoint Signaling ◽  
Damage Repair ◽  
Genomic Approach ◽  
Telomere Regulation

ABSTRACT Mre11, Rad50, and Nbs1 form a conserved heterotrimeric complex that is involved in recombination and DNA damage checkpoints. Mutations in this complex disrupt the S-phase DNA damage checkpoint, the checkpoint which slows replication in response to DNA damage, and cause chromosome instability and cancer in humans. However, how these proteins function and specifically where they act in the checkpoint signaling pathway remain crucial questions. We identified fission yeast Nbs1 by using a comparative genomic approach and showed that the genes for human Nbs1 and fission yeast Nbs1 and that for their budding yeast counterpart, Xrs2, are members of an evolutionarily related but rapidly diverging gene family. Fission yeast Nbs1, Rad32 (the homolog of Mre11), and Rad50 are involved in DNA damage repair, telomere regulation, and the S-phase DNA damage checkpoint. However, they are not required for G2 DNA damage checkpoint. Our results suggest that a complex of Rad32, Rad50, and Nbs1 acts specifically in the S-phase branch of the DNA damage checkpoint and is not involved in general DNA damage recognition or signaling.

scholarly journals The Schizosaccharomyces pombe S-Phase Checkpoint Differentiates Between Different Types of DNA Damage

Genetics ◽  
1998 ◽  
Vol 149 (4) ◽  
pp. 1729-1737 ◽  
Author(s):  
Nicholas Rhind ◽  
Paul Russell
Keyword(s):  
Dna Damage ◽  
Schizosaccharomyces Pombe ◽  
S Phase ◽  
Dna Damage Checkpoint ◽  
Haploid Cell ◽  
Γ Irradiation ◽  
Replication Checkpoint ◽  
Checkpoint Proteins ◽  
Base Modification ◽  
Different Types

Abstract We have identified an S-phase DNA damage checkpoint in Schizosaccharomyces pombe. This checkpoint is dependent on Rad3, the S. pombe homolog of the mammalian ATM/ATR checkpoint proteins, and Cds1. Cds1 had previously been believed to be involved only in the replication checkpoint. The requirement of Cds1 in the DNA damage checkpoint suggests that Cds1 may be a general target of S-phase checkpoints. Unlike other checkpoints, the S. pombe S-phase DNA damage checkpoint discriminates between different types of damage. UV-irradiation, which causes base modification that can be repaired during G1 and S-phase, invokes the checkpoint, while γ-irradiation, which causes double-stranded breaks that cannot be repaired by a haploid cell if induced before replication, does not invoke the checkpoint. Because the same genes are required to respond to UV- and γ-irradiation during G2, this discrimination may represent an active suppression of the γ response during S-phase.

scholarly journals p21 Inhibits Cdk1 in the Absence of Cdk2 to Maintain the G1/S Phase DNA Damage Checkpoint

2008 ◽  
Vol 19 (1) ◽  
pp. 65-77 ◽  
Author(s):  
Ande Satyanarayana ◽  
Mary Beth Hilton ◽  
Philipp Kaldis
Keyword(s):  
Dna Damage ◽  
Liver Cells ◽  
S Phase ◽  
Dna Damage Checkpoint ◽  
Regenerating Liver ◽  
Γ Irradiation ◽  
Embryonic Fibroblasts ◽  
Repair Activity ◽  
Lethal Irradiation

Cdk1 was proposed to compensate for the loss of Cdk2. Here we present evidence that this is possible due to premature translocation of Cdk1 from the cytoplasm to the nucleus in the absence of Cdk2. We also investigated the consequence of loss of Cdk2 on the maintenance of the G1/S DNA damage checkpoint. Cdk2−/− mouse embryonic fibroblasts in vitro as well as regenerating liver cells after partial hepatectomy (PH) in Cdk2−/− mice, arrest promptly at the G1/S checkpoint in response to γ-irradiation due to activation of p53 and p21 inhibiting Cdk1. Furthermore re-entry into S phase after irradiation was delayed in Cdk2−/− cells due to prolonged and impaired DNA repair activity. In addition, Cdk2−/− mice were more sensitive to lethal irradiation compared to wild-type and displayed delayed resumption of DNA replication in regenerating liver cells. Our results suggest that the G1/S DNA damage checkpoint is intact in the absence of Cdk2, but Cdk2 is important for proper repair of the damaged DNA.

scholarly journals Monitoring Schizosaccharomyces pombe genome stress by visualizing end-binding protein Ku

Biology Open ◽  
2021 ◽  
Vol 10 (2) ◽  
Author(s):  
Chance E. Jones ◽  
Susan L. Forsburg
Keyword(s):  
Dna Damage ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Protein Complex ◽  
Genome Stability ◽  
Binding Protein ◽  
Dna Lesions ◽  
Live Cells ◽  
Dna Damage Checkpoint ◽  
Ku Protein

ABSTRACT Studies of genome stability have exploited visualization of fluorescently tagged proteins in live cells to characterize DNA damage, checkpoint, and repair responses. In this report, we describe a new tool for fission yeast, a tagged version of the end-binding protein Pku70 which is part of the KU protein complex. We compare Pku70 localization to other markers upon treatment to various genotoxins, and identify a unique pattern of distribution. Pku70 provides a new tool to define and characterize DNA lesions and the repair response.

scholarly journals Roles of the Mitotic Inhibitors Wee1 and Mik1 in the G2 DNA Damage and Replication Checkpoints

2001 ◽  
Vol 21 (5) ◽  
pp. 1499-1508 ◽  
Author(s):  
Nicholas Rhind ◽  
Paul Russell
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Dna Damage Checkpoint ◽  
Mitotic Inhibitors

ABSTRACT The G2 DNA damage and DNA replication checkpoints in many organisms act through the inhibitory phosphorylation of Cdc2 on tyrosine-15. This phosphorylation is catalyzed by the Wee1/Mik1 family of kinases. However, the in vivo role of these kinases in checkpoint regulation has been unclear. We show that, in the fission yeastSchizosaccharomyces pombe, Mik1 is a target of both checkpoints and that the regulation of Mik1 is, on its own, sufficient to delay mitosis in response to the checkpoints. Mik1 appears to have two roles in the DNA damage checkpoint; one in the establishment of the checkpoint and another in its maintenance. In contrast, Wee1 does not appear to be involved in the establishment of either checkpoint.

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