Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have isolated and characterized an isoform of protein kinase Chk1 gene from rat liver and a rat liver cDNA library by 5'-rapid amplification of cDNA ends. The gene (Cil) contains the C-terminal region of the Chk1 gene, but the 5'-end is derived from a sequence in the intron of Chk1 preceding the C-terminal domain by differential RNA splicing. The kinase domain of Chk1 gene is absent in this isoform. Tissue RNA and protein blot analyses indicated that Cil was specifically expressed only in rat liver, and its expression increased with liver development. Expression of Cil was found to be reduced in three rat hepatoma cell lines examined. A promoter trap experiment suggested that a promoter was located in the intron preceding the C-terminal domain of Chk1, and transcription from this novel promoter generated the new 5' noncoding exon of Cil. Thus Cil was generated by both alternate promoter usage and differential RNA splicing. UV irradiation induced caffeine-sensitive phosphorylation of both Chk1 and Cil at Ser-345 in Chk1 and its equivalent site in Cil, implying a role for ATR kinase in the phosphorylation of both proteins. We demonstrated the interaction between the kinase domain of Chk1 and Cil using a yeast two-hybrid assay and pull-down technique. In contrast to the effect of Chk1, Cil was found to decrease the transactivating function of p53, and the S63A mutation of Cil abolished this effect. These results suggest that Cil may serve as a dominant negative competitor of Chk1 as suggested previously.
...
PMID:Cloning and characterization of liver-specific isoform of Chk1 gene from rat. 1168 78

The CHK2 gene encodes a protein kinase that is important for the regulation of cell cycle arrest after DNA damage. CHK2 acts downstream of ataxia teleangiecstasia mutated (ATM), modulates the function of p53 and may help mediate cell cycle arrest at G2/M by phosphorylation of Cdc25C. Recently, the human homolog of the checkpoint kinase Cds1 (CHK2) has been suggested to be a tumor suppressor gene. Heterozygous germline mutations have been reported in Li-Fraumeni syndrome (LFS), a highly penetrant familial cancer phenotype, and in sporadic colon cancer. LFS is associated with the development of lymphoid malignancies, especially childhood ALL. Therefore, we analyzed the DNA from 143 lymphoid malignancies to determine whether they had mutations of the CHK2 gene. The 14 exons of CHK2 were studied by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) and sequencing of aberrantly migrating bands. One missense mutation changing serine to phenylalanine (codon 428) in an evolutionarily highly conserved domain was found in a non-Hodgkin's aggressive lymphoma. Another point mutation in the non-coding region was identified in one of adult T-cell leukemias (ATL) samples. This result suggests that mutation of the CHK2 gene may rarely be involved in the development of selected lymphomas.
...
PMID:Analysis of the CHK2 gene in lymphoid malignancies. 1169 18

Cell cycle checkpoints are surveillance mechanisms that monitor and coordinate the order and fidelity of cell cycle events. When defects in the division program of a cell are detected, checkpoints prevent the pursuant cell cycle transition through regulation of the relevant cyclin-cdk complex(es). Checkpoints that respond to DNA damage have been described for the G1, S and G2 phases of the cell cycle. The p53 tumour suppressor is a key regulator of G1/S checkpoints, and can promote cell cycle delay or apoptosis in response to DNA damage. The importance of these events to cellular physiology is highlighted by the fact that tumours, in which p53 is frequently mutated, have widespread defects in the G1/S DNA damage checkpoints and a heightened level of genomic instability. G2/M DNA damage checkpoints have been defined by yeast genetics, though the genes in this response are conserved in mammals. We show here using biochemical and physiological assays that p53 is dispensable for a DNA damage checkpoint activated in the G2 phase of the cell cycle. Moreover, upregulation of p53 through serine 20 phosphorylation, does not occur in G2. Conversely, we show that the Chk1 protein kinase is essential for the human G2 DNA damage checkpoint. Importantly, inhibition of Chk1 in p53 deficient cells greatly sensitizes them to radiation, validating the hypothesis of targeting Chk1 in rational drug design and development for anti-cancer therapies.
...
PMID:Inhibition of Chk1-dependent G2 DNA damage checkpoint radiosensitizes p53 mutant human cells. 1170 16

Ded1 is a fission yeast DEAD box protein involved in translation. We isolated Ded1 in a screen for multi-copy suppressors of a cold-sensitive, loss-of-function mutant of the cyclin-dependent kinase Cdc2. The checkpoint protein kinase Chk1, required for cell cycle arrest in response to DNA damage, was also isolated in this screen. Ded1 interacts with Chk1 in a two-hybrid screen, and this physical interaction can be recapitulated in Schizosaccharomyces pombe. The Ded1 polypeptide is modified in response to heat shock and depletion of carbon source. These two stressors appear to cause different modifications. Thus, the Ded1 protein appears to respond to particular types of cellular stress and may influence the activity of Cdc2 as a result.
...
PMID:The Ded1 DEAD box helicase interacts with Chk1 and Cdc2. 1171 40

We have investigated the mechanism of S-phase arrest elicited by the carcinogen benzo(a)pyrene dihydrodiol epoxide (BPDE) in p53-deficient cells. Inhibition of DNA synthesis after BPDE treatment was rapid and dose dependent (approximately 50% inhibition after 2 h with 50 nM BPDE). Cells treated with low doses (50-100 nM) of BPDE resumed DNA synthesis after a delay of approximately 4-8 h, whereas cells that received high doses of BPDE (600 nM) failed to recover from S-phase arrest. The checkpoint kinase Chk1 (but not Chk2) was phosphorylated after treatment with low doses of BPDE. High concentrations of BPDE elicited phosphorylation of both Chk1 and Chk2. Adenovirus-mediated expression of "dominant-negative" Chk1 (but not dominant-negative Chk2) and the Chk1 inhibitor UCN-01 abrogated the S-phase delay elicited by low doses of BPDE. Consistent with a role for the caffeine-sensitive ATM or ATR protein kinase in low-dose BPDE-induced S-phase arrest, both Chk1 phosphorylation and S-phase arrest were abrogated by caffeine. However, low doses of BPDE elicited Chk1 phosphorylation and S-phase arrest in AT cells (from ataxia telangiectasia patients), demonstrating that ATM is dispensable for S-phase checkpoint responses to this genotoxin. BPDE-induced Chk1 phosphorylation and S-phase arrest were abrogated by caffeine treatment in AT cells, suggesting that a caffeine-sensitive kinase other than ATM is an important mediator of responses to BPDE-adducted DNA. Overall, our data demonstrate the existence of a caffeine-sensitive, Chk1-mediated, S-phase checkpoint that is operational in response to BPDE.
...
PMID:Carcinogen-induced S-phase arrest is Chk1 mediated and caffeine sensitive. 1186 11

After exposure to genotoxic stress, proliferating cells actively slow down the DNA replication through a S-phase checkpoint to provide time for repair. We report that in addition to the ataxia-telangiectasia mutated (ATM)-dependent pathway that controls the fast response, there is an ATM-independent pathway that controls the slow response to regulate the S-phase checkpoint after ionizing radiation in mammalian cells. The slow response of S-phase checkpoint, which is resistant to wortmannin, sensitive to caffeine and UCN-01, and related to cyclin-dependent kinase phosphorylation, is much stronger in CHK1 overexpressed cells, and it could be abolished by Chk1 antisense oligonucleotides. These results provide evidence that the ATM-independent slow response of S-phase checkpoint involves CHK1 pathway.
...
PMID:An ATM-independent S-phase checkpoint response involves CHK1 pathway. 1191 27

The Cdc25 family of dual specific phosphatases are critical components of cell cycle progression and checkpoint control. Certain stresses such as ultraviolet light stimulate the rapid and selective destruction of Cdc25A protein through a Chk1 protein kinase-dependent pathway. We demonstrate that in contrast to cellular stresses previously examined, hydrogen peroxide exposure affects Cdc25C but not Cdc25A levels. Pharmacological inhibition of Chk1 activity or a mutant of Cdc25C that lacks the Chk1 phosphorylation site still undergoes degradation in response to oxidants. We also demonstrate that in vitro hydrogen peroxide stimulates an intramolecular disulfide bond between the active site cysteine at position 377 and another invariant cysteine at position 330. The in vivo stability of Cdc25C is substantially reduced by the mutation of either of these two cysteine residues. In contrast, a double (C2) mutant of both cysteine 330 and cysteine 377 results in a protein that is more stable than wild type Cdc25C and is resistant to oxidative stress-induced degradation. In addition, the C2 mutant, which is unable to form an intramolecular disulfide bond, has reduced binding to 14-3-3 in vitro and in vivo. These results suggest that oxidative stress may induce cell cycle arrest in part through the degradation of Cdc25C.
...
PMID:Redox regulation of Cdc25C. 1192 43

Marine natural products provide a rich source of chemical diversity that can be used to design and develop new, potentially useful therapeutic agents. We report here that scytonemin, a pigment isolated from cyanobacteria, is the first described small molecule inhibitor of human polo-like kinase, a serine/threonine kinase that plays an integral role in regulating the G(2)/M transition in the cell cycle. Scytonemin inhibited polo-like kinase 1 activity in a concentration-dependent manner with an IC(50) of 2 microM against the recombinant enzyme. Biochemical analysis showed that scytonemin reduced GST-polo-like kinase 1 activity in a time-independent fashion, suggesting reversibility, and with a mixed-competition mechanism with respect to ATP. Although scytonemin was less potent against protein kinase A and Tie2, a tyrosine kinase, it did inhibit other cell cycle-regulatory kinases like Myt1, checkpoint kinase 1, cyclin-dependent kinase 1/cyclin B, and protein kinase Cbeta2 with IC(50) values similar to that seen for polo-like kinase 1. Consistent with these effects, scytonemin effectively attenuated, without chemical toxicity, the growth factor- or mitogen-induced proliferation of three cell types commonly implicated in inflammatory hyperproliferation. Similarly, scytonemin (up to 10 microM) was not cytotoxic to nonproliferating endotoxin-stimulated human monocytes. In addition, Jurkat T cells treated with scytonemin were induced to undergo apoptosis in a non-cell cycle-dependent manner consistent with its activities on multiple kinases. Here we propose that scytonemin's dimeric structure, unique among natural products, may be a valuable template for the development of more potent and selective kinase inhibitors used for the treatment of hyperproliferative disorders.
...
PMID:The identification and characterization of the marine natural product scytonemin as a novel antiproliferative pharmacophore. 1238 73

Checkpoint kinase (Chk)1 is an evolutionarily conserved protein kinase that was first identified in fission yeast as an essential component of the DNA damage checkpoint. In mice, Chk1 provides an essential function in the absence of environmentally imposed genotoxic stress. Here we show that human cells lacking Chk1 exhibit defects in both the ionizing radiation (IR)-induced S and G(2) checkpoints. In addition, loss of Chk1 resulted in the accumulation of a hypophosphorylated form of the Cdc25A protein phosphatase, and Chk1-deficient cells failed to degrade Cdc25A after IR. The IR-induced S and G(2) checkpoints were partially restored in Chk1-deficient cells when Cdc25A accumulation was interfered with. Finally, Cdc25A was phosphorylated by Chk1 in vitro on similar sites phosphorylated in vivo, including serine-123. These findings indicate that Chk1 directly phosphorylates Cdc25A during an unperturbed cell cycle, and that phosphorylation of Cdc25A by Chk1 is required for cells to delay cell cycle progression in response to double-strand DNA breaks.
...
PMID:Disruption of the checkpoint kinase 1/cell division cycle 25A pathway abrogates ionizing radiation-induced S and G2 checkpoints. 1239 44

In the fission yeast Schizosaccharomyces pombe, the protein kinase Chk1 has an essential role in transducing a delay signal to the cell cycle machinery in the presence of DNA damage. Fission yeast cells lacking the chk1 gene do not delay progression of the cell cycle in response to damage and are thus sensitive to DNA damaging agents. We have previously shown that Chk1 is phosphorylated following DNA damage induced by a variety of agents and that this is dependent on the integrity of the DNA damage checkpoint pathway, including Rad3, the ATR homolog. Through a combination of mutagenesis and phospho-specific antibodies, we have shown that serine at position 345 (S345) is phosphorylated in vivo in response to DNA damage, and that S345 phosphorylation is required for an intact checkpoint response. We have developed a kinase assay for Chk1, and have shown that basal Chk1 kinase activity is increased in response to DNA damage and that this increase, but not the basal activity, is dependent on S345. Furthermore, we show that S345 phosphorylation is required for Chk1 to associate with Rad24, a 14-3-3 protein, upon DNA damage. These results are consistent with a model whereby Chk1 phosphorylation results in increased Chk1 kinase activity that is necessary for both checkpoint delay and cellular survival following damage to the genome. These data are similar to observations made in mammalian cells and Xenopus oocyte extracts, suggesting that mechanisms leading to Chk1 activation have been conserved in evolution.
...
PMID:Phosphorylation activates Chk1 and is required for checkpoint-mediated cell cycle arrest. 1241


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

---