scholarly journals Suppressors of Cdc25p Overexpression Identify Two Pathways That Influence the G2/M Checkpoint in Fission Yeast

Genetics ◽  
1998 ◽  
Vol 150 (4) ◽  
pp. 1361-1375
Author(s):  
Kristi Chrispell Forbes ◽  
Timothy Humphrey ◽  
Tamar Enoch
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Gene Encoding ◽  
Replication Checkpoint ◽  
Checkpoint Response ◽  
Dead Box ◽  
New Genes ◽  
Checkpoint Pathway ◽  
Dna Replication Checkpoint ◽  
New Gene

Abstract Checkpoints maintain the order of cell-cycle events. At G2/M, a checkpoint blocks mitosis in response to damaged or unreplicated DNA. There are significant differences in the checkpoint responses to damaged DNA and unreplicated DNA, although many of the same genes are involved in both responses. To identify new genes that function specifically in the DNA replication checkpoint pathway, we searched for high-copy suppressors of overproducer of Cdc25p (OPcdc25+), which lacks a DNA replication checkpoint. Two classes of suppressors were isolated. One class includes a new gene encoding a putative DEAD box helicase, suppressor of uncontrolled mitosis (sum3+). This gene negatively regulates the cell-cycle response to stress when overexpressed and restores the checkpoint response by a mechanism that is independent of Cdc2p tyrosine phosphorylation. The second class includes chk1+ and the two Schizosaccharomyces pombe 14-3-3 genes, rad24+ and rad25+, which appear to suppress the checkpoint defect by inhibiting Cdc25p. We show that rad24Δ mutants are defective in the checkpoint response to the DNA replication inhibitor hydroxyurea at 37° and that cds1Δ rad24Δ mutants, like cds1Δ chk1Δ mutants, are entirely checkpoint deficient at 29°. These results suggest that chk1+ and rad24+ may function redundantly with cds1+ in the checkpoint response to unreplicated DNA.

scholarly journals The yeast Sgs1p helicase acts upstream of Rad53p in the DNA replication checkpoint and colocalizes with Rad53p in S-phase-specific foci

2000 ◽  
Vol 14 (1) ◽  
pp. 81-96 ◽  
Author(s):  
Christian Frei ◽  
Susan M. Gasser
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Replication Fork ◽  
Dna Helicase ◽  
S Phase ◽  
Replication Checkpoint ◽  
Checkpoint Response ◽  
Replication Fork Progression ◽  
Cycle Arrest ◽  
Dna Replication Checkpoint

We have examined the cellular function of Sgs1p, a nonessential yeast DNA helicase, homologs of which are implicated in two highly debilitating hereditary human diseases (Werner's and Bloom's syndromes). We show that Sgs1p is an integral component of the S-phase checkpoint response in yeast, which arrests cells due to DNA damage or blocked fork progression during DNA replication. DNA polε and Sgs1p are found in the same epistasis group and act upstream of Rad53p to signal cell cycle arrest when DNA replication is perturbed. Sgs1p is tightly regulated through the cell cycle, accumulates in S phase and colocalizes with Rad53p in S-phase-specific foci, even in the absence of fork arrest. The association of Rad53p with a chromatin subfraction is Sgs1p dependent, suggesting an important role for the helicase in the signal-transducing pathway that monitors replication fork progression.

The Spd1p S phase inhibitor can activate the DNA replication checkpoint pathway in fission yeast

2000 ◽  
Vol 113 (23) ◽  
pp. 4341-4350 ◽  
Author(s):  
A. Borgne ◽  
P. Nurse
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Checkpoint Control ◽  
Replication Checkpoint ◽  
Checkpoint Pathway ◽  
Dna Replication Checkpoint ◽  
A Cell ◽  
Checkpoint Genes

Spd1p (for S phase delayed) is a cell cycle inhibitor in Schizosaccharomyces pombe. Spd1p overexpression blocks the onset of both S phase and mitosis. In this study, we have investigated the mechanisms by which Spd1p overexpression blocks cell cycle progression, focussing on the block over mitotic onset. High levels of Spd1p lead to an increase in Y15 phosphorylation of Cdc2p and we show that the block over G(2) requires the Wee1p kinase and is dependent on the rad and chk1/cds1 checkpoint genes. We propose that high levels of Spd1p in G(2) cells activate the DNA replication checkpoint control, which leads to a Wee1p-dependent increase of Cdc2p Y15 phosphorylation blocking onset of mitosis. The Spd1p block at S phase onset may act by interfering directly with DNA replication, and also activates the G(2)rad/hus checkpoint pathway to block mitosis.

scholarly journals A tel2 Mutation That Destabilizes the Tel2-Tti1-Tti2 Complex Eliminates Rad3ATR Kinase Signaling in the DNA Replication Checkpoint and Leads to Telomere Shortening in Fission Yeast

2019 ◽  
Vol 39 (20) ◽  
Author(s):  
Yong-jie Xu ◽  
Saman Khan ◽  
Adam C. Didier ◽  
Michal Wozniak ◽  
Yufeng Liu ◽  
...  
Keyword(s):  
Dna Replication ◽  
Fission Yeast ◽  
Large Scale ◽  
Gene Encoding ◽  
Telomere Shortening ◽  
Signaling Mechanism ◽  
Replication Checkpoint ◽  
Checkpoint Signaling ◽  
Enhanced Sensitivity ◽  
Dna Replication Checkpoint

ABSTRACT In response to perturbed DNA replication, ATR (ataxia telangiectasia and Rad3-related) kinase is activated to initiate the checkpoint signaling necessary for maintaining genome integrity and cell survival. To better understand the signaling mechanism, we carried out a large-scale genetic screen in fission yeast looking for mutants with enhanced sensitivity to hydroxyurea. From a collection of ∼370 primary mutants, we found a few mutants in which Rad3 (ATR ortholog)-mediated phospho-signaling was significantly compromised. One such mutant carried an uncharacterized mutation in tel2, a gene encoding an essential and highly conserved eukaryotic protein. Previous studies in various biological models have shown that Tel2 mainly functions in Tel2-Tti1-Tti2 (TTT) complex that regulates the steady-state levels of all phosphatidylinositol 3-kinase-like protein kinases, including ATR. We show here that although the levels of Rad3 and Rad3-mediated phospho-signaling in DNA damage checkpoint were moderately reduced in the tel2 mutant, the phospho-signaling in the DNA replication checkpoint was almost completely eliminated. In addition, the tel2 mutation caused telomere shortening. Since the interactions of Tel2 with Tti1 and Tti2 were significantly weakened by the mutation, destabilization of the TTT complex likely contributes to the observed checkpoint and telomere defects.

The DNA replication checkpoint response stabilizes stalled replication forks

Nature ◽  
2001 ◽  
Vol 412 (6846) ◽  
pp. 557-561 ◽  
Author(s):  
Massimo Lopes ◽  
Cecilia Cotta-Ramusino ◽  
Achille Pellicioli ◽  
Giordano Liberi ◽  
Paolo Plevani ◽  
...  
Keyword(s):  
Dna Replication ◽  
Replication Forks ◽  
Replication Checkpoint ◽  
Checkpoint Response ◽  
Dna Replication Checkpoint ◽  
Stalled Replication Forks

Dpb11/TopBP1 plays distinct roles in DNA replication, checkpoint response and homologous recombination

DNA Repair ◽  
2011 ◽  
Vol 10 (2) ◽  
pp. 210-224 ◽  
Author(s):  
Susanne M. Germann ◽  
Vibe H. Oestergaard ◽  
Caroline Haas ◽  
Pauline Salis ◽  
Akira Motegi ◽  
...  
Keyword(s):  
Dna Replication ◽  
Homologous Recombination ◽  
Replication Checkpoint ◽  
Checkpoint Response ◽  
Dna Replication Checkpoint

scholarly journals Chl12 (Ctf18) Forms a Novel Replication Factor C-Related Complex and Functions Redundantly with Rad24 in the DNA Replication Checkpoint Pathway

2001 ◽  
Vol 21 (17) ◽  
pp. 5838-5845 ◽  
Author(s):  
Takahiro Naiki ◽  
Tae Kondo ◽  
Daisuke Nakada ◽  
Kunihiro Matsumoto ◽  
Katsunori Sugimoto
Keyword(s):  
Dna Replication ◽  
Dna Damage Checkpoint ◽  
Replication Factor C ◽  
Replication Checkpoint ◽  
Replication Factor ◽  
Checkpoint Pathway ◽  
Dna Replication Checkpoint ◽  
Replication Block ◽  
Factor C ◽  
Related Complex

ABSTRACT RAD24 has been identified as a gene essential for the DNA damage checkpoint in budding yeast. Rad24 is structurally related to subunits of the replication factor C (RFC) complex, and forms an RFC-related complex with Rfc2, Rfc3, Rfc4, and Rfc5. Therad24Δ mutation enhances the defect ofrfc5-1 in the DNA replication block checkpoint, implicating RAD24 in this checkpoint.CHL12 (also called CTF18) encodes a protein that is structurally related to the Rad24 and RFC proteins. We show here that although neither chl12Δ norrad24Δ single mutants are defective, chl12Δ rad24Δ double mutants become defective in the replication block checkpoint. We also show that Chl12 interacts physically with Rfc2, Rfc3, Rfc4, and Rfc5 and forms an RFC-related complex which is distinct from the RFC and RAD24 complexes. Our results suggest that Chl12 forms a novel RFC-related complex and functions redundantly with Rad24 in the DNA replication block checkpoint.

scholarly journals Drosophila dCBP Is Involved in Establishing the DNA Replication Checkpoint

2006 ◽  
Vol 27 (1) ◽  
pp. 135-146 ◽  
Author(s):  
Sarah Smolik ◽  
Kristen Jones
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cell Cycle Arrest ◽  
Chromatin Structure ◽  
Genetic Interaction ◽  
Structure And Function ◽  
Replication Checkpoint ◽  
Cycle Arrest ◽  
Dna Replication Checkpoint ◽  
And Function

ABSTRACT The CBP/p300 family of proteins comprises related acetyltransferases that coactivate signal-responsive transcription. Recent evidence suggests that p300/CBP may also interact directly with complexes that mediate different aspects of DNA metabolism such as replication and repair. In this report, we show that loss of dCBP in Drosophila cells and eye discs results in a defect in the cell cycle arrest induced by stalled DNA replication. We show that dCBP and the checkpoint kinase Mei-41 can be found together in a complex and, furthermore, that dCBP has a genetic interaction with mei-41 in the response to stalled DNA replication. These observations suggest a broader role for the p300/CBP acetyltransferases in the modulation of chromatin structure and function during DNA metabolic events as well as for transcription.

scholarly journals Positive Regulation of Wee1 by Chk1 and 14-3-3 Proteins

2001 ◽  
Vol 12 (3) ◽  
pp. 551-563 ◽  
Author(s):  
Joon Lee ◽  
Akiko Kumagai ◽  
William G. Dunphy
Keyword(s):  
Cell Cycle ◽  
Active Form ◽  
Wild Type ◽  
Common Pathway ◽  
Replication Checkpoint ◽  
Checkpoint Response ◽  
M Phase ◽  
Dna Replication Checkpoint ◽  
Egg Extracts ◽  
Positive Regulators

Wee1 inactivates the Cdc2–cyclin B complex during interphase by phosphorylating Cdc2 on Tyr-15. The activity of Wee1 is highly regulated during the cell cycle. In frog egg extracts, it has been established previously that Xenopus Wee1 (Xwee1) is present in a hypophosphorylated, active form during interphase and undergoes down-regulation by extensive phosphorylation at M-phase. We report that Xwee1 is also regulated by association with 14-3-3 proteins. Binding of 14-3-3 to Xwee1 occurs during interphase, but not M-phase, and requires phosphorylation of Xwee1 on Ser-549. A mutant of Xwee1 (S549A) that cannot bind 14-3-3 is substantially less active than wild-type Xwee1 in its ability to phosphorylate Cdc2. This mutation also affects the intranuclear distribution of Xwee1. In cell-free kinase assays, Xchk1 phosphorylates Xwee1 on Ser-549. The results of experiments in which Xwee1, Xchk1, or both were immunodepleted fromXenopus egg extracts suggested that these two enzymes are involved in a common pathway in the DNA replication checkpoint response. Replacement of endogenous Xwee1 with recombinant Xwee1-S549A in egg extracts attenuated the cell cycle delay induced by addition of excess recombinant Xchk1. Taken together, these results suggest that Xchk1 and 14-3-3 proteins act together as positive regulators of Xwee1.

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