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posted to atm kap-1
by DNAReplication
on 2008-03-01 23:32:47
Abstract
The cellular DNA-damage response is a signaling network that is vigorously activated by cytotoxic DNA lesions, such as double-strand breaks (DSBs)1. The DSB response is mobilized by the nuclear protein kinase ATM, which modulates this process by phosphorylating key players in these pathways2. A long-standing question in this field is whether DSB formation affects chromatin condensation. Here, we show that DSB formation is followed by ATM-dependent chromatin relaxation. ATM's effector in this pathway is the protein KRAB-associated protein (KAP-1, also known ...
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Abstract
SR proteins constitute a family of pre-mRNA splicing factors now thought to play several roles in mRNA metabolism in metazoan cells. Here we provide evidence that a prototypical SR protein, ASF/SF2, is unexpectedly required for maintenance of genomic stability. We first show that in vivo depletion of ASF/SF2 results in a hypermutation phenotype likely due to DNA rearrangements, reflected in the rapid appearance of DNA double-strand breaks and high-molecular-weight DNA fragments. Analysis of DNA from ASF/SF2-depleted cells revealed that the nontemplate ...
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Abstract
Cellular DNA damage triggers the DNA damage response pathway and leads to enforcement of cell cycle checkpoints, which are essential for the maintenance of genomic integrity and are activated in early stages of tumorigenesis. A special feature of prostate cancer is its high incidence and multifocality. To address the functionality of DNA damage checkpoints in the prostate, we analyzed the responses of human primary prostate epithelial cells (HPECs) and freshly isolated human prostate tissues to gamma-irradiation. We find that gamma-irradiation activates ...
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Abstract
The ataxia-telangiectasia mutated (Atm) protein kinase is a central regulator of the cellular response to DNA damage. Although Atm can regulate p53, it is not known if this Atm function varies between tissues. Previous studies showed that the induction of p53 and apoptosis by whole-body ionizing radiation varies greatly between tissue and tumor types, so here we asked if Atm also had a tissue-specific role in the ionizing radiation response. Irradiated Atm-null mice showed impaired p53 induction and apoptosis in thymus, ...
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Abstract
Abstract 10.1002/aja.1002030302.abs We describe a series of stages for development of the embryo of the zebrafish, Danio (Brachydanio) rerio. We define seven broad periods of embryogenesis—the zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and hatching periods. These divisions highlight the changing spectrum of major developmental processes that occur during the first 3 days after fertilization, and we review some of what is known about morphogenesis and other significant events that occur during each of the periods. Stages subdivide the periods. Stages are ...
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Mol Cell Biol, Vol. 23, No. 12. (June 2003), pp. 4247-4256
posted to pml topbp1
by DNAReplication ✚
on 2008-02-10 03:09:28
Abstract
The PML tumor suppressor gene is consistently disrupted by t(15;17) in patients with acute promyelocytic leukemia. Promyelocytic leukemia protein (PML) is a multifunctional protein that plays essential roles in cell growth regulation, apoptosis, transcriptional regulation, and genome stability. Our study here shows that PML colocalizes and associates in vivo with the DNA damage response protein TopBP1 in response to ionizing radiation (IR). Both PML and TopBP1 colocalized with the IR-induced bromodeoxyuridine single-stranded DNA foci. PML and TopBP1 also colocalized with Rad50, ...
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Mol Cell Biol, Vol. 22, No. 2. (January 2002), pp. 555-566
posted to irif topbp1
by DNAReplication ✚
on 2008-02-09 13:05:39
Abstract
BRCA1 carboxyl-terminal (BRCT) motifs are present in a number of proteins involved in DNA repair and/or DNA damage-signaling pathways. Human DNA topoisomerase II binding protein 1 (TopBP1) contains eight BRCT motifs and shares sequence similarity with the fission yeast Rad4/Cut5 protein and the budding yeast DPB11 protein, both of which are required for DNA damage and/or replication checkpoint controls. We report here that TopBP1 is phosphorylated in response to DNA double-strand breaks and replication blocks. TopBP1 forms nuclear foci and localizes ...
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by R. Rai, H. Dai, A. S. Multani, et al.K. Li, K. Chin, J. Gray, J. P. Lahad, J. Liang, G. B. Mills, F. Meric-Bernstam, S. Y. Lin
posted to mcph1
by DNAReplication
on 2008-02-09 12:34:30
Abstract
BRIT1, initially identified as an hTERT repressor, has additional functions at DNA damage checkpoints. Here, we demonstrate that BRIT1 formed nuclear foci minutes after irradiation. The foci of BRIT1 colocalized with 53BP1, MDC1, NBS1, ATM, RPA, and ATR. BRIT1 was required for activation of these elements, indicating that BRIT1 is a proximal factor in the DNA damage response pathway. Depletion of BRIT1 increased the accumulation of chromosomal aberrations. In addition, decreased levels of BRIT1 were detected in several types of human ...
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EMBO J, Vol. 18, No. 23. (1 December 1999), pp. 6845-6854
posted to p38 p53
by DNAReplication
on 2008-02-08 16:11:26
Abstract
Components of the ras signaling pathway contribute to activation of cellular p53. In MCF-7 cells, p38 kinase activated p53 more effectively than other members of the ras pathway. p53 and p38 kinase exist in the same physical complex, and co-expression of p38 stabilized p53 protein. In vitro, p38 kinase phosphorylated p53 at Ser33 and Ser46, a newly identified site. Mutation of these sites decreased p53-mediated and UV-induced apoptosis, and the reduction correlated with total abrogation of UV-induced phosphorylation on Ser37 and ...
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Cancer Res, Vol. 62, No. 9. (1 May 2002), pp. 2483-2487
posted to chk1
by DNAReplication ✚
on 2008-02-07 20:48:01
Abstract
Camptothecin (CPT) that targets DNA topoisomerase I is one of the most promising broad-spectrum anticancer drugs in development today. The cytotoxicity of CPT is S phase (S)-specific because the collision of advancing replication forks with CPT-topoisomerase I-DNA complexes results in DNA damage. After DNA damage, proliferating cells could actively slow down the DNA replication through an S checkpoint to provide time for repair. We report now that there is an activated S checkpoint response in CPT-treated mammalian cells. This response is ...
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posted to chk1 xenopus
by DNAReplication ✚
on 2008-02-07 20:11:02
Abstract
We have identified Claspin, a novel protein that binds to Xenopus Chk1 (Xchk1). Binding of Claspin to Xchk1 is highly elevated in the presence of DNA templates that trigger a checkpoint arrest of the cell cycle in Xenopus egg extracts. Xchk1 becomes phosphorylated during a checkpoint response, and we demonstrate directly that this phosphorylation results in the activation of Xchk1. Immunodepletion of Claspin from egg extracts abolishes both the phosphorylation and activation of Xchk1. Furthermore, Claspin-depleted extracts are unable to arrest ...
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Abstract
The checkpoint kinases ATM (ataxia telangiectasia mutated) and ATR (ATM and Rad3 related) transduce genomic stress signals to halt cell cycle progression and promote DNA repair. We report the identification of an ATR-interacting protein (ATRIP) that is phosphorylated by ATR, regulates ATR expression, and is an essential component of the DNA damage checkpoint pathway. ATR and ATRIP both localize to intranuclear foci after DNA damage or inhibition of replication. Deletion of ATR mediated by the Cre recombinase caused the loss of ...
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posted to atr drosophila
by DNAReplication
on 2008-02-06 23:59:44
Abstract
Background: Drosophila embryogenesis is initiated by 13 rapid syncytial mitotic divisions that do not require zygotic gene activity. This maternally directed cleavage phase of development terminates at the midblastula transition (MBT), at which point the cell cycle slows dramatically, membranes surround the cortical nuclei to form a cellular blastoderm, and zygotic gene expression is first required. Results: We show that embryos lacking Mei-41, a Drosophila homologue of the ATM tumor suppressor, proceed through unusually short syncytial mitoses, fail to terminate syncytial ...
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posted to atm drosophila
by DNAReplication
on 2008-02-06 23:49:46
Abstract
Cells of metazoan organisms respond to DNA damage by arresting their cell cycle to repair DNA, or they undergo apoptosis. Two protein kinases, ataxia-telangiectasia mutated (ATM) and ATM and Rad-3 related (ATR), are sensors for DNA damage. In humans, ATM is mutated in patients with ataxia-telangiectasia (A-T), resulting in hypersensitivity to ionizing radiation (IR) and increased cancer susceptibility. Cells from A-T patients exhibit chromosome aberrations and excessive spontaneous apoptosis. We used Drosophila as a model system to study ATM function. Previous ...
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posted to drosophila
by DNAReplication
on 2008-02-06 23:48:39
Abstract
ATM is a large, multifunctional protein kinase that regulates responses required for surviving DNA damage: including DNA repair, apoptosis, and cell cycle checkpoints. Here, we show that Drosophila ATM function is essential for normal adult development. Extensive, inappropriate apoptosis occurs in proliferating atm mutant tissues, and in clonally derived atm mutant embryos, frequent mitotic defects were seen. At a cellular level, spontaneous telomere fusions and other chromosomal abnormalities are common in atm larval neuroblasts, suggesting a conserved and essential role for ...
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posted to atm drosophila
by DNAReplication ✚
on 2008-02-06 23:18:12
Abstract
Others have suggested recently that the conserved ATM checkpoint kinase is minimally involved in controlling the G(2)/M checkpoint in Drosophila that serves to prevent mitotic entry in the presence of DNA damage. Our data indicate that both ATM and its regulator Mre11 are important for the checkpoint and that their roles become essential when animals are challenged with a low dose of X rays or when they have compromised checkpoint function of the ATM-related ATR kinase. ...
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Genetics, Vol. 132, No. 2. (October 1992), pp. 337-350
Abstract
We report the isolation and characterization of a synoptic set of site-directed mutations distributed throughout the single actin gene of Saccharomyces cerevisiae. Mutations were systematically targeted to the surface of the protein by identifying clusters of 2 or more charged residues in the primary sequence; every charged residue in a cluster was replaced with alanine. Mutations were recovered in high yield (34 of 36 constructed) as heterozygous diploids. Mutant phenotypes were examined in haploid segregants: 11 were recessive lethal, 16 conditional-lethal ...
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posted to tol2
by DNAReplication
on 2008-02-05 22:56:22
Abstract
The medaka fish Tol2 element is an autonomous transposon that encodes a fully functional transposase. The transposase protein can catalyze transposition of a transposon construct that has 200 and 150 base pairs of DNA from the left and right ends of the Tol2 sequence, respectively. These sequences contain essential terminal inverted repeats and subterminal sequences. DNA inserts of fairly large sizes (as large as 11 kilobases) can be cloned between these sequences without reducing transpositional activity. The Tol2 transposon system has ...
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posted to tol2
by DNAReplication ✚
on 2008-02-05 22:50:49
Abstract
Transgenesis is an important tool for assessing gene function. In zebrafish, transgenesis has suffered from three problems: the labor of building complex expression constructs using conventional subcloning; low transgenesis efficiency, leading to mosaicism in transient transgenics and infrequent germline incorporation; and difficulty in identifying germline integrations unless using a fluorescent marker transgene. The Tol2kit system uses site-specific recombination-based cloning (multisite Gateway technology) to allow quick, modular assembly of [promoter]-[coding sequence]-[3' tag] constructs in a Tol2 transposon backbone. It includes a destination ...
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Abstract
Timing of DNA replication initiation is dependent on S-phase-promoting kinase (SPK) activity at discrete origins and the simultaneous function of many replicons. DNA damage prevents origin firing through the ATM- and ATR-dependent inhibition of Cdk2 and Cdc7 SPKs. Here, we establish that modulation of ATM- and ATR-signalling pathways controls origin firing in the absence of DNA damage. Inhibition of ATM and ATR with caffeine or specific neutralizing antibodies, or upregulation of Cdk2 or Cdc7, promoted rapid and synchronous origin firing; conversely, ...
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Abstract
NLSdb is a database of nuclear localization signals (NLSs) and of nuclear proteins. NLSs are short stretches of residues mediating transport of nuclear proteins into the nucleus. The database contains 114 experimentally determined NLSs that were obtained through an extensive literature search. Using ‘in silico mutagenesis’ this set was extended to 308 experimental and potential NLSs. This final set matched over 43% of all known nuclear proteins and matches no currently known non-nuclear protein. NLSdb contains over 6000 predicted nuclear proteins ...
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Methods Mol Biol, Vol. 396 (2007), pp. 59-70
Abstract
Protein sequence classification and comparison has become increasingly important in the current "omics" revolution, where scientists are working on functional genomics and proteomics technologies for large-scale protein function prediction. However, functional classification is also important for the bench scientist wanting to analyze single or small sets of proteins, or even a single genome. A number of tools are available for sequence classification, such as sequence similarity searches, motif- or pattern-finding software, and protein signatures for identifying protein families and domains. One ...
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Mol Cell, Vol. 6, No. 4. (October 2000), pp. 839-849
Abstract
We have identified Claspin, a novel protein that binds to Xenopus Chk1 (Xchk1). Binding of Claspin to Xchk1 is highly elevated in the presence of DNA templates that trigger a checkpoint arrest of the cell cycle in Xenopus egg extracts. Xchk1 becomes phosphorylated during a checkpoint response, and we demonstrate directly that this phosphorylation results in the activation of Xchk1. Immunodepletion of Claspin from egg extracts abolishes both the phosphorylation and activation of Xchk1. Furthermore, Claspin-depleted extracts are unable to arrest ...
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EMBO J, Vol. 17, No. 1. (2 January 1998), pp. 159-169
posted to atr s-m-checkpoint
by DNAReplication ✚
on 2008-02-04 17:11:06
Abstract
ATR, a phosphatidylinositol kinase-related protein homologous to ataxia telangiectasia mutated (ATM), is important for the survival of human cells following many forms of DNA damage. Expression of a kinase-inactive allele of ATR (ATRkd) in human fibroblasts causes increased sensitivity to ionizing radiation (IR), cis-platinum and methyl methanesulfonate, but only slight UV radiation sensitivity. ATRkd overexpression abrogates the G2/M arrest after exposure to IR, and overexpression of wild-type ATR complements the radioresistant DNA synthesis phenotype of cells lacking ATM, suggesting a potential ...
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Abstract
Claspin is essential for the ATR-dependent activation of Chk1 in Xenopus egg extracts containing incompletely replicated DNA. Claspin associates with replication forks upon origin unwinding. We show that Claspin contains a replication fork-interacting domain (RFID, residues 265-605) that associates with Cdc45, DNA polymerase epsilon, replication protein A, and two replication factor C complexes on chromatin. The RFID contains two basic patches (BP1 and BP2) at amino acids 265-331 and 470-600, respectively. Deletion of either BP1 or BP2 compromises optimal binding of ...
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Cell, Vol. 105, No. 2. (20 April 2001), pp. 177-186
by D. Moshous, I. Callebaut, R. de Chasseval, et al.B. Corneo, M. Cavazzana-Calvo, F. Le Deist, I. Tezcan, O. Sanal, Y. Bertrand, N. Philippe, A. Fischer, J. P. de Villartay
posted to artemis
by DNAReplication
on 2008-02-04 06:14:53
Abstract
The V(D)J recombination process insures the somatic diversification of immunoglobulin and antigen T cell receptor encoding genes. This reaction is initiated by a DNA double-strand break (dsb), which is resolved by the ubiquitously expressed DNA repair machinery. Human T-B-severe combined immunodeficiency associated with increased cellular radiosensitivity (RS-SCID) is characterized by a defect in the V(D)J recombination leading to an early arrest of both B and T cell maturation. We previously mapped the disease-related locus to the short arm of chromosome 10. ...
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by H. Date, O. Onodera, H. Tanaka, et al.K. Iwabuchi, K. Uekawa, S. Igarashi, R. Koike, T. Hiroi, T. Yuasa, Y. Awaya, T. Sakai, T. Takahashi, H. Nagatomo, Y. Sekijima, I. Kawachi, Y. Takiyama, M. Nishizawa, N. Fukuhara, K. Saito, S. Sugano, S. Tsuji
posted to aptx
by DNAReplication
on 2008-02-04 06:09:53
Abstract
Friedreich ataxia (FRDA), the most common autosomal recessive neurodegenerative disease among Europeans and people of European descent, is characterized by an early onset (usually before the age of 25), progressive ataxia, sensory loss, absence of tendon reflexes and pyramidal weakness of the legs. We have recently identified a unique group of patients whose clinical presentations are characterized by autosomal recessive inheritance, early age of onset, FRDA-like clinical presentations and hypoalbuminemia. Linkage to the FRDA locus, however, was excluded. Given the similarities ...
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posted to scan-1
by DNAReplication ✚
on 2008-02-04 06:06:39
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by Dietke Buck, Laurent Malivert, Régina de Chasseval, et al.Anne Barraud, Marie-Claude Fondanèche, Ozden Sanal, Alessandro Plebani, Jean-Louis Stéphan, Markus Hufnagel, Françoise le Deist, Alain Fischer, Anne Durandy, Jean-Pierre de Villartay, Patrick Revy
Abstract
DNA double-strand breaks (DSBs) occur at random upon genotoxic stresses and represent obligatory intermediates during physiological DNA rearrangement events such as the V(D)J recombination in the immune system. DSBs, which are among the most toxic DNA lesions, are preferentially repaired by the nonhomologous end-joining (NHEJ) pathway in higher eukaryotes. Failure to properly repair DSBs results in genetic instability, developmental delay, and various forms of immunodeficiency. Here we describe five patients with growth retardation, microcephaly, and immunodeficiency characterized by a profound T+B ...
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Molecular cell, Vol. 8, No. 6. (December 2001), pp. 1175-1185
by M. O'Driscoll, K. M. Cerosaletti, P. M. Girard, et al.Y. Dai, M. Stumm, B. Kysela, B. Hirsch, A. Gennery, S. E. Palmer, J. Seidel, R. A. Gatti, R. Varon, M. A. Oettinger, H. Neitzel, P. A. Jeggo, P. Concannon
posted to lig4
by DNAReplication
on 2008-02-04 06:01:02
Abstract
DNA ligase IV functions in DNA nonhomologous end-joining and V(D)J recombination. Four patients with features including immunodeficiency and developmental and growth delay were found to have mutations in the gene encoding DNA ligase IV (LIG4). Their clinical phenotype closely resembles the DNA damage response disorder, Nijmegen breakage syndrome (NBS). Some of the mutations identified in the patients directly disrupt the ligase domain while others impair ...
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by Daphne W. Bell, Jennifer M. Varley, Tara E. Szydlo, et al.Deborah H. Kang, Doke C. R. Wahrer, Kristen E. Shannon, Marcie Lubratovich, Sigitas J. Verselis, Kurt J. Isselbacher, Joseph F. Fraumeni, Jillian M. Birch, Frederick P. Li, Judy E. Garber, Daniel A. Haber
posted to chk2
by DNAReplication ✚
on 2008-02-04 05:53:55
Abstract
The hCHK2 gene encodes the human homolog of the yeast Cds1 and Rad53 G2 checkpoint kinases, whose activation in response to DNA damage prevents cellular entry into mitosis. Here, it is shown that heterozygous germ line mutations in hCHK2occur in Li-Fraumeni syndrome, a highly penetrant familial cancer phenotype usually associated with inherited mutations in theTP53 gene. These observations suggest that hCHK2is a tumor suppressor gene conferring predisposition to sarcoma, breast cancer, and brain tumors, and they also provide a link between ...
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Am J Hum Genet, Vol. 56, No. 3. (March 1995), pp. 608-615
posted to p53
by DNAReplication ✚
on 2008-02-04 05:51:44
Abstract
Germ-line mutations of the tumor-suppressor gene p53 have been observed in some families with the Li-Fraumeni syndrome (LFS), a familial cancer syndrome in which affected relatives develop a diverse set of early-onset malignancies including breast carcinoma, sarcomas, and brain tumors. The analysis of the p53 gene in LFS families has been limited, in most studies to date, to the region between exon 5 and exon 9. In order to determine the frequency and distribution of germ-line p53 mutations in LFS, we ...
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Abstract
A strong candidate for the 17q-linked BRCA1 gene, which influences susceptibility to breast and ovarian cancer, has been identified by positional cloning methods. Probable predisposing mutations have been detected in five of eight kindreds presumed to segregate BRCA1 susceptibility alleles. The mutations include an 11-base pair deletion, a 1-base pair insertion, a stop codon, a missense substitution, and an inferred regulatory mutation. The BRCA1 gene ...
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Am J Hum Genet, Vol. 71, No. 1. (July 2002), pp. 136-142
by A. P. Jackson, H. Eastwood, S. M. Bell, et al.J. Adu, C. Toomes, I. M. Carr, E. Roberts, D. J. Hampshire, Y. J. Crow, A. J. Mighell, G. Karbani, H. Jafri, Y. Rashid, R. F. Mueller, A. F. Markham, C. G. Woods
Abstract
Primary microcephaly (MIM 251200) is an autosomal recessive neurodevelopmental condition in which there is a global reduction in cerebral cortex volume, to a size comparable with that of early hominids. We previously mapped the MCPH1 locus, for primary microcephaly, to chromosome 8p23, and here we report that a gene within this interval, encoding a BRCA1 C-terminal domain-containing protein, is mutated in MCPH1 families sharing an ancestral 8p23 haplotype. This gene, microcephalin, is expressed in the developing cerebral cortex of the fetal ...
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posted to ataxia-telangiectasia atm
by DNAReplication ✚
on 2008-02-04 05:33:06
Abstract
Ataxia-telangiectasia (A-T) is a progressive neurodegenerative disorder, with onset in early childhood and a frequency of approximately 1 in 40,000 births in the United States. A-T is seen among all races and is most prominent among ethnic groups with a high frequency of consanguinity. The syndrome includes: progressive cerebellar ataxia, dysarthric speech, oculomotor apraxia, choreoathetosis and, later, oculocutaneous telangiectasia. Immunodeficiency with sinopulmonary infections, cancer susceptibility (usually lymphoid), and sensitivity to ionizing radiation are also characteristic. Laboratory findings include: (1) elevated alphafetoprotein ...
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posted to atld mre11
by DNAReplication ✚
on 2008-02-04 05:27:38
Abstract
Comparison of the clinical and cellular phenotypes of different genomic instability syndromes provides new insights into functional links in the complex network of the DNA damage response. A prominent example of this principle is provided by examination of three such disorders: ataxia-telangiectasia (A-T) caused by lack or inactivation of the ATM protein kinase, which mobilises the cellular response to double strand breaks in the DNA; ataxia-telangiectasia-like disease (ATLD), a result of deficiency of the human Mre11 protein; and the Nijmegen breakage ...
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J Med Genet, Vol. 33, No. 2. (February 1996), pp. 153-156
posted to nbs1
by DNAReplication ✚
on 2008-02-04 05:23:19
Abstract
Nijmegen breakage syndrome (NBS), a rare autosomal recessive condition also known as ataxia telangiectasia (AT) variants V1 and V2, is characterised by microcephaly, typical facies, short stature, immunodeficiency, and chromosomal instability. We report the clinical, immunological, chromosomal, and cell biological findings in 42 patients who are included in the NBS Registry in Nijmegen. The immunological, chromosomal, and cell biological findings resemble those in AT, but the clinical findings are quite different. NBS appears to be a separate entity not allelic with ...
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Abstract
The breast cancer tumor-suppressor gene, BRCA1, encodes a protein with a BRCT domain-a motif that is found in many proteins that are implicated in DNA damage response and in genome stability. Phosphorylation of BRCA1 by the DNA damage-response proteins ATM, ATR and hCds1/Chk2 changes in response to DNA damage and at replication-block checkpoints. Although cells that lack BRCA1 have an abnormal response to DNA damage, the exact role of BRCA1 in this process has remained unclear. Here we show that BRCA1 ...
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posted to chk1 claspin
by DNAReplication ✚
on 2008-02-04 01:41:07
Abstract
Claspin is essential for the ATR-dependent activation of Chk1 in Xenopus egg extracts containing incompletely replicated or UV-damaged DNA. The activated form of Claspin contains two repeated phosphopeptide motifs that mediate its binding to Chk1. We show that these phosphopeptide motifs bind to Chk1 by means of its N-terminal kinase domain. The binding site on Chk1 involves a positively charged cluster of amino acids that contains lysine 54, arginine 129, threonine 153, and arginine 162. Mutagenesis of these residues strongly compromises ...
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Abstract
Tipin is a mammalian protein that interacts with Timeless, which plays a role in DNA damage checkpoint responses. Here, we show that Tipin is a nuclear protein that associates with the replicative helicase and protects cells against genotoxic agents. Tipin is required for efficient cell cycle arrest in response to DNA damage, and depletion of Tipin renders cells sensitive to ionizing radiation as well as replication stress. Loss of Tipin results in spontaneous gamma-H2AX foci, a marker for DNA double-strand breaks. ...
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posted to atr chk1 claspin
by DNAReplication ✚
on 2008-02-04 00:32:54
Abstract
Claspin is a homolog of Mrc1, a checkpoint protein required for the DNA replication checkpoint in yeast. In Xenopus, phosphorylated Claspin binds to xChk1 and regulates xChk1 activation in response to replication stress. In this study, we have shown that the human homolog of Claspin is required for resistance to multiple forms of genotoxic stress including UV, IR, and hydroxyurea. Phosphorylation of Claspin was found to depend on the ataxia telangiectasia mutated-Rad3 related (ATR) pathway. DNA damage induces the formation of ...
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posted to chk2
by DNAReplication ✚
on 2008-02-03 21:51:43
Abstract
hCds1 (Chk2) is an evolutionarily conserved kinase that functions in DNA damage response and cell cycle checkpoint. The Cds1 family of kinases are activated by a family of large phosphatidylinositol 3-kinase-like kinases. In humans, ataxia telangiectasia-mutated (ATM) and ataxia-telangiectasia and Rad3-related kinases activate hCds1 by phosphorylating Thr(68) . hCds1 and Cds1-related kinases contain the FHA (forkhead-associated) domain, which appears to be important for integrating the DNA damage signal. It is not known how ATM phosphorylation activates hCds1 function and whether the ...
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posted to atm chk2
by DNAReplication ✚
on 2008-02-03 21:44:21
Abstract
In response to DNA damage, eukaryotic cells use a system of checkpoint controls to delay cell-cycle progression. Checkpoint delays provide time for repair of damaged DNA before its replication in S phase and before segregation of chromatids in M phase. The Cds1 (Chk2) tumour-suppressor protein has been implicated in certain checkpoint responses in mammalian cells. It directly phosphorylates and inactivates the mitosis-inducing phosphatase Cdc25 in vitro and is required to maintain the G2 arrest that is observed in response to gamma-irradiation. ...
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Proceedings of the National Academy of Sciences, Vol. 97, No. 19. (12 September 2000), pp. 10389-10394, doi:10.1073/pnas.190030497
Abstract
10.1073/pnas.190030497 ...
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Proc Natl Acad Sci U S A, Vol. 96, No. 24. (23 November 1999), pp. 13777-13782
Abstract
Stabilization of p53 in response to DNA damage is caused by its dissociation from Mdm2, a protein that targets p53 for degradation in the proteasome. Dissociation of p53 from Mdm2 could be caused by DNA damage-induced p53 posttranslational modifications. The ATM and ATR kinases, whose activation in response to ionizing radiation (IR) and UV light, respectively, is required for p53 stabilization, directly phosphorylate p53 on Ser-15. However, phosphorylation of Ser-15 is critical for the apoptotic activity of p53 and not for ...
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Genes Dev, Vol. 11, No. 24. (15 December 1997), pp. 3471-3481
Abstract
Data are presented demonstrating that DNA damage leads to specific post-translational modifications of p53 protein. Using two-dimensional peptide mapping of in vivo radiolabeled p53 tryptic phosphopeptides, recombinant truncated p53 protein, and synthetic p53 tryptic peptides, a unique p53 phosphopeptide was identified after exposure of ML-1 cells to ionizing irradiation. This peptide represents the first 24 amino acids of p53 and contains three phosphorylated serine residues. A specific p53 phosphopeptide antibody identified serine-15 as one of the two serines in p53 that ...
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Abstract
Chk2 is a protein kinase that is activated in response to DNA damage and may regulate cell cycle arrest. We generated Chk2-deficient mouse cells by gene targeting. Chk2-/- embryonic stem cells failed to maintain gamma-irradiation-induced arrest in the G2 phase of the cell cycle. Chk2-/- thymocytes were resistant to DNA damage-induced apoptosis. Chk2-/- cells were defective for p53 stabilization and for induction of p53-dependent transcripts ...
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Genes Dev, Vol. 14, No. 3. (1 February 2000), pp. 289-300
Abstract
Upon DNA damage, the amino terminus of p53 is phosphorylated at a number of serine residues including S20, a site that is particularly important in regulating stability and function of the protein. Because no known kinase has been identified that can modify this site, HeLa nuclear extracts were fractionated and S20 phosphorylation was followed. We discovered that a S20 kinase activity copurifies with the human homolog of the Schizosaccharomyces pombe checkpoint kinase, Chk1 (hCHK1). We confirmed that recombinant hCHK1, but not ...
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by Magtouf Gatei, Katie Sloper, Claus Sorensen, et al.Randi Syljuasen, Jacob Falck, Karen Hobson, Kienan Savage, Jiri Lukas, Bin-Bing Zhou, Jiri Bartek, Kum K. Khanna
posted to atm chk1
by DNAReplication ✚
on 2008-02-03 18:55:18
Abstract
In mammals, the ATM (ataxia-telangiectasia-mutated) and ATR (ATM and Rad3-related) protein kinases function as critical regulators of the cellular DNA damage response. The checkpoint functions of ATR and ATM are mediated, in part, by a pair of checkpoint effector kinases termed Chk1 and Chk2. In mammalian cells, evidence has been presented that Chk1 is devoted to the ATR signaling pathway and is modified by ATR in response to replication inhibition and UV-induced damage, whereas Chk2 functions primarily through ATM in response ...
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