Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Swi1 is required for programmed pausing of replication forks near the mat1 locus in the fission yeast Schizosaccharomyces pombe. This fork pausing is required to initiate a recombination event that switches mating type. Swi1 is also needed for the replication checkpoint that arrests division in response to fork arrest. How Swi1 accomplishes these tasks is unknown. Here we report that Swi1 copurifies with a 181-amino-acid protein encoded by swi3(+). The Swi1-Swi3 complex is required for survival of fork arrest and for activation of the replication checkpoint kinase Cds1. Association of Swi1 and Swi3 with chromatin during DNA replication correlated with movement of the replication fork. swi1Delta and swi3Delta mutants accumulated Rad22 (Rad52 homolog) DNA repair foci during replication. These foci correlated with the Rad22-dependent appearance of Holliday junction (HJ)-like structures in cells lacking Mus81-Eme1 HJ resolvase. Rhp51 and Rhp54 homologous recombination proteins were not required for viability in swi1Delta or swi3Delta cells, indicating that the HJ-like structures arise from single-strand DNA gaps or rearranged forks instead of broken forks. We propose that Swi1 and Swi3 define a fork protection complex that coordinates leading- and lagging-strand synthesis and stabilizes stalled replication forks.
Mol Cell Biol 2004 Oct
PMID:Swi1 and Swi3 are components of a replication fork protection complex in fission yeast. 1536 56

Mutations in Artemis in both humans and mice result in severe combined immunodeficiency due to a defect in V(D)J recombination. In addition, Artemis mutants are radiosensitive and chromosomally unstable, which has been attributed to a defect in nonhomologous end joining (NHEJ). We show here, however, that Artemis-depleted cell extracts are not defective in NHEJ and that Artemis-deficient cells have normal repair kinetics of double-strand breaks after exposure to ionizing radiation (IR). Artemis is shown, however, to interact with known cell cycle checkpoint proteins and to be a phosphorylation target of the checkpoint kinase ATM or ATR after exposure of cells to IR or UV irradiation, respectively. Consistent with these findings, our results also show that Artemis is required for the maintenance of a normal DNA damage-induced G2/M cell cycle arrest. Artemis does not appear, however, to act either upstream or downstream of checkpoint kinase Chk1 or Chk2. These results define Artemis as having a checkpoint function and suggest that the radiosensitivity and chromosomal instability of Artemis-deficient cells may be due to defects in cell cycle responses after DNA damage.
Mol Cell Biol 2004 Oct
PMID:Artemis is a phosphorylation target of ATM and ATR and is involved in the G2/M DNA damage checkpoint response. 1545 91

Genetically distinct checkpoints, activated as a consequence of either DNA replication arrest or ionizing radiation-induced DNA damage, integrate DNA repair responses into the cell cycle programme. The ataxia-telangiectasia mutated (ATM) protein kinase blocks cell cycle progression in response to DNA double strand breaks, whereas the related ATR is important in maintaining the integrity of the DNA replication apparatus. Here, we show that thymidine, which slows the progression of replication forks by depleting cellular pools of dCTP, induces a novel DNA damage response that, uniquely, depends on both ATM and ATR. Thymidine induces ATM-mediated phosphorylation of Chk2 and NBS1 and an ATM-independent phosphorylation of Chk1 and SMC1. AT cells exposed to thymidine showed decreased viability and failed to induce homologous recombination repair (HRR). Taken together, our results implicate ATM in the HRR-mediated rescue of replication forks impaired by thymidine treatment.
Hum Mol Genet 2004 Dec 01
PMID:ATM is required for the cellular response to thymidine induced replication fork stress. 1545 81

The BRCA1 C-terminal (BRCT) domain has recently been implicated as a phospho-protein binding domain. We demonstrate here that a CTBP-interacting protein CtIP interacts with BRCA1 BRCT domains in a phosphorylation-dependent manner. The CtIP/BRCA1 complex only exists in G(2) phase and is required for DNA damage-induced Chk1 phosphorylation and the G(2)/M transition checkpoint. However, the CtIP/BRCA1 complex is not required for the damage-induced G(2) accumulation checkpoint, which is controlled by a separate BRCA1/BACH1 complex. Taken together, these data not only implicate CtIP as a critical player in cell cycle checkpoint control but also provide molecular mechanisms by which BRCA1 controls multiple cell cycle transitions after DNA damage.
Mol Cell Biol 2004 Nov
PMID:DNA damage-induced cell cycle checkpoint control requires CtIP, a phosphorylation-dependent binding partner of BRCA1 C-terminal domains. 1548 15

Inhibitors of the G(2) DNA damage checkpoint can selectively sensitize cancer cells with mutated p53 to killing by DNA-damaging agents. Isogranulatimide is a G(2) checkpoint inhibitor containing a unique indole/maleimide/imidazole skeleton identified in a phenotypic cell-based screen; however, the mechanism of action of isogranulatimide is unknown. Using natural and synthetic isogranulatimide analogues, we show that the imide nitrogen and a basic nitrogen at position 14 or 15 in the imidazole ring are important for checkpoint inhibition. Isogranulatimide shows structural resemblance to the aglycon of UCN-01, a potent bisindolemaleimide inhibitor of protein kinase C beta (IC(50), 0.001 micromol/L) and of the checkpoint kinase Chk1 (IC(50), 0.007 micromol/L). In vitro kinase assays show that isogranulatimide inhibits Chk1 (IC(50), 0.1 micromol/L) but not protein kinase C beta. Of 13 additional protein kinases tested, isogranulatimide significantly inhibits only glycogen synthase kinase-3beta (IC(50), 0.5 micromol/L). We determined the crystal structure of the Chk1 catalytic domain complexed with isogranulatimide. Like UCN-01, isogranulatimide binds in the ATP-binding pocket of Chk1 and hydrogen bonds with the backbone carbonyl oxygen of Glu(85) and the amide nitrogen of Cys(87). Unlike UCN-01, the basic N15 of isogranulatimide interacts with Glu(17), causing a conformation change in the kinase glycine-rich loop that may contribute importantly to inhibition. The mechanism by which isogranulatimide inhibits Chk1 and its favorable kinase selectivity profile make it a promising candidate for modulating checkpoint responses in tumors for therapeutic benefit.
Mol Cancer Ther 2004 Oct
PMID:Inhibition of Chk1 by the G2 DNA damage checkpoint inhibitor isogranulatimide. 1548 89

The checkpoint kinase Cds1 (Chk2) plays a key role in cell cycle checkpoint responses with functions in cell cycle arrest, DNA repair, and induction of apoptosis. Proper regulation of Cds1 is essential for appropriate cellular responses to checkpoint-inducing insults. While the kinase ATM has been shown to be important in the regulation of human Cds1 (hCds1), here we report that the kinases ATR and DNA-dependent protein kinase (DNA-PK) play more significant roles in the regulation of Xenopus Cds1 (XCds1). Under normal cell cycle conditions, nonactivated XCds1 constitutively associates with a Xenopus ATR complex. The association of XCds1 with this complex does not require a functional forkhead activation domain but does require a putative SH3 binding region that is found in XCds1. In response to double-stranded DNA ends, the amino terminus of XCds1 is rapidly phosphorylated in a sequential pattern. First DNA-PK phosphorylates serine 39, a site not previously recognized as important in Cds1 regulation. Xenopus ATM, ATR, and/or DNA-PK then phosphorylate three consensus serine/glutamine sites. Together, these phosphorylations have the dual function of inducing dissociation from the ATR complex and independently promoting the full activation of XCds1. Thus, the checkpoint-mediated activation of XCds1 requires phosphorylation by multiple phosphoinositide 3-kinase-related kinases, protein-protein dissociation, and autophosphorylation.
Mol Cell Biol 2004 Nov
PMID:Xenopus Cds1 is regulated by DNA-dependent protein kinase and ATR during the cell cycle checkpoint response to double-stranded DNA ends. 1550 99

In Saccharomyces cerevisiae, Mec1/ATR plays a primary role in sensing and transducing checkpoint signals in response to different types of DNA lesions, while the role of the Tel1/ATM kinase in DNA damage checkpoints is not as well defined. We found that UV irradiation in G(1) in the absence of Mec1 activates a Tel1/MRX-dependent checkpoint, which specifically inhibits the metaphase-to-anaphase transition. Activation of this checkpoint leads to phosphorylation of the downstream checkpoint kinases Rad53 and Chk1, which are required for Tel1-dependent cell cycle arrest, and their adaptor Rad9. The spindle assembly checkpoint protein Mad2 also partially contributes to the G(2)/M arrest of UV-irradiated mec1Delta cells independently of Rad53 phosphorylation and activation. The inability of UV-irradiated mec1Delta cells to undergo anaphase can be relieved by eliminating the anaphase inhibitor Pds1, whose phosphorylation and stabilization in these cells depend on Tel1, suggesting that Pds1 persistence may be responsible for the inability to undergo anaphase. Moreover, while UV irradiation can trigger Mec1-dependent Rad53 phosphorylation and activation in G(1)- and G(2)-arrested cells, Tel1-dependent checkpoint activation requires entry into S phase independently of the cell cycle phase at which cells are UV irradiated, and it is decreased when single-stranded DNA signaling is affected by the rfa1-t11 allele. This indicates that UV-damaged DNA molecules need to undergo structural changes in order to activate the Tel1-dependent checkpoint. Active Clb-cyclin-dependent kinase 1 (CDK1) complexes also participate in triggering this checkpoint and are required to maintain both Mec1- and Tel1-dependent Rad53 phosphorylation, suggesting that they may provide critical phosphorylation events in the DNA damage checkpoint cascade.
Mol Cell Biol 2004 Dec
PMID:A Tel1/MRX-dependent checkpoint inhibits the metaphase-to-anaphase transition after UV irradiation in the absence of Mec1. 1554 24

Eukaryotic cells regulate progression through the cell cycle in response to DNA damage. Cell cycle checkpoints are the signal transduction pathways that couple the detection of DNA damage to the proteins that control transitions in the cell cycle. The protein kinase Chk1, originally discovered in fission yeast, but conserved in humans, is essential for preventing mitotic entry in the presence of DNA damage or blocks to DNA replication that cannot be reconciled. Chk1 is phosphorylated in response to DNA damage. Phosphorylation depends on the activity of conserved components of the checkpoint pathway including Rad3, a member of the ATM/ATR family of kinases. Phosphorylation leads to activation of Chk1 kinase activity. In this chapter, we describe an assay for monitoring the activity of Chk1 isolated.
Methods Mol Biol 2005
PMID:Assaying cell cycle checkpoints: activity of the protein kinase Chk1. 1557 43

The cellular response to DNA damage is mediated by evolutionarily conserved Ser/Thr kinases, phosphorylation of Cdc25 protein phosphatases, binding to 14-3-3 proteins, and exit from the cell cycle. To investigate DNA damage responses mediated by the p38/stress-activated protein kinase (SAPK) axis of signaling, the optimal phosphorylation motifs of mammalian p38alpha SAPK and MAPKAP kinase-2 were determined. The optimal substrate motif for MAPKAP kinase-2, but not for p38 SAPK, closely matches the 14-3-3 binding site on Cdc25B/C. We show that MAPKAP kinase-2 is directly responsible for Cdc25B/C phosphorylation and 14-3-3 binding in vitro and in response to UV-induced DNA damage within mammalian cells. Downregulation of MAPKAP kinase-2 eliminates DNA damage-induced G2/M, G1, and intra S phase checkpoints. We propose that MAPKAP kinase-2 is a new member of the DNA damage checkpoint kinase family that functions in parallel with Chk1 and Chk2 to integrate DNA damage signaling responses and cell cycle arrest in mammalian cells.
Mol Cell 2005 Jan 07
PMID:MAPKAP kinase-2 is a cell cycle checkpoint kinase that regulates the G2/M transition and S phase progression in response to UV irradiation. 1566 83

The mechanisms by which environmental stress regulates cell cycle progression are poorly understood. In fission yeast, we show that Srk1 kinase, which associates with the stress-activated p38/Sty1 MAP kinase, regulates the onset of mitosis by inhibiting the Cdc25 phosphatase. Srk1 is periodically active in G2, and its overexpression causes cell cycle arrest in late G2 phase, whereas cells lacking srk1 enter mitosis prematurely. We find that Srk1 interacts with and phosphorylates Cdc25 at the same sites phosphorylated by the Chk1 and Cds1 (Chk2) kinases and that this phosphorylation is necessary for Srk1 to delay mitotic entry. Phosphorylation by Srk1 causes Cdc25 to bind to Rad24, a 14-3-3 protein family member, and accumulation of Cdc25 in the cytoplasm. However, Srk1 does not regulate Cdc25 in response to replication arrest or DNA damage but, rather, during a normal cell cycle and in response to nongenotoxic environmental stress.
Mol Cell 2005 Jan 07
PMID:Inactivation of the Cdc25 phosphatase by the stress-activated Srk1 kinase in fission yeast. 1566 83


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>