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Query: UNIPROT:P16104 (H2AX)
 3,930 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We previously reported that protein kinase A activity is an important determinant of thyroid cell survival. Given the important role of cAMP response element binding protein (CREB) in mediating the transcriptional effects of protein kinase A, we explored whether interference with CREB family members impaired thyroid cell survival. Expression of A-CREB, a dominant-negative CREB mutant that inhibits CREB DNA binding activity, induced apoptosis in rat thyroid cells. A-CREB inhibited CRE-regulated gene expression but failed to alter the expression of bcl-2 family members or of well-characterized inhibitors of apoptosis. To elucidate the mechanism through which impaired CREB function triggered apoptosis, its effects on cell proliferation were examined. Expression of A-CREB inhibited cell number increases, in part due to delayed cell cycle transit. Protracted S-phase progression in A-CREB-expressing cells was sufficient to activate a checkpoint response characterized by Chk-1, histone H2A.X, and p53 phosphorylation. To determine whether cell cycle progression was required for apoptosis, the effects of p27 overexpression were investigated. Overexpression of p27 prevented cell cycle progression, checkpoint activation, and apoptosis in A-CREB-expressing cells. These data reveal a novel mechanism through which interference with CREB abrogates cell survival, through checkpoint activation secondary to cell cycle delay. This study may explain how interference with CREB induces apoptosis in cells where alterations in the expression of pro- and anti-survival genes are not detected.
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PMID:Interference with 3',5'-cyclic adenosine monophosphate response element binding protein stimulates apoptosis through aberrant cell cycle progression and checkpoint activation. 1641 Mar 15

In this study, we investigated the formation of radiation-induced foci in normal human fibroblasts exposed to X rays or 130 keV/mum nitrogen ions using antibodies to phosphorylated protein kinase ataxia telangiectasia mutated (ATMp) and histone H2AX (gamma-H2AX). High-content automatic image analysis was used to quantify the immunofluorescence of radiation-induced foci. The size of radiation-induced foci increased for both proteins over a 2-h period after nitrogen-ion irradiation, while the size of radiation-induced foci did not change after exposure to low-LET radiation. The number of radiation-induced ATMp foci showed a more rapid rise and greater frequency after X-ray exposure and was resolved more rapidly such that the frequency of radiation-induced foci decreased by 90% compared to 60% after exposure to high-LET radiation 2 h after 30 cGy. In contrast, the kinetics of radiation-induced gamma-H2AX focus formation was similar for high- and low-LET radiation in that it reached a plateau early and remained constant for up to 2 h. High-resolution 3D images of radiation-induced gamma-H2AX foci and dosimetry computation suggest that multiple double-strand breaks from nitrogen ions are encompassed within large nuclear domains of 4.4 Mbp. Our work shows that the size and frequency of radiation-induced foci vary as a function of radiation quality, dose, time and protein target. Thus, even though double-strand breaks and radiation-induced foci are correlated, the dynamic nature of both contradicts their accepted equivalence for low doses of different radiation qualities.
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PMID:Imaging features that discriminate between foci induced by high- and low-LET radiation in human fibroblasts. 1666 4

The cyclin-dependent kinase (CDK) inhibitor roscovitine is under evaluation in clinical trials for its antiproliferative properties. Roscovitine arrests cell cycle progression in G(1) and in G(2) phase by inhibiting CDK2 and CDK1, and possibly CDK7 and CDK9. However, the effects of CDK2 inhibition in S-phase cells have been not fully investigated. Here, we show that a short-term treatment with roscovitine is sufficient to inhibit DNA synthesis, and to activate a DNA damage checkpoint response, as indicated by phosphorylation of p53-Ser15, replication protein A, and histone H2AX. Analysis of DNA replication proteins loaded onto DNA during S phase showed that the amount of proliferating cell nuclear antigen (PCNA), a cofactor of DNA replication enzymes, was significantly reduced by roscovitine. In contrast, chromatin-bound levels of DNA polymerase delta, DNA ligase I and CDK2, were stabilized. Checkpoint inhibition with caffeine could rescue PCNA disassembly only partially, pointing to additional effects due to CDK2 inhibition and the presence of replication stress. These results suggest that in S-phase cells, roscovitine induces checkpoint-dependent and -independent effects, leading to stabilization of replication forks and an uncoupling between PCNA and PCNA-interacting proteins.
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PMID:Replication-dependent DNA damage response triggered by roscovitine induces an uncoupling of DNA replication proteins. 1696 15

Progression of the cells through the S phase of the cell cycle is connected with accumulation of stalled and collapsed replication forks that are repaired by homologous recombination. To investigate the temporal order of homologous recombination events during the S phase, HeLa cells synchronized at the G1/S phase boundary with mimosine were released to progress into the S phase and the phosphorylation of the histone variant H2AX, the appearance of Rad51 nuclear foci and the subcellular redistribution of Rad51 were followed. The results showed that there was gradual accumulation of double-strand breaks as judged by the increase in the phosphorylation of H2AX during the S phase. Rad51 nuclear foci did not appear until middle S phase, and this was accompanied by an increase in the chromatin- and nuclear matrix-bound Rad51 in the middle to late S phase. To determine the role of the intra S phase checkpoint in the S phase-dependent redistribution of Rad51 the cells were released in the S phase in the presence of the protein kinase inhibitors caffeine and wortmannin. The results suggest that the association of Rad51 with the nuclear matrix is regulated by activation of the intra S phase ATR-dependent checkpoint pathway.
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PMID:Cell cycle-dependent association of Rad51 with the nuclear matrix. 1726 95

Poly(ADP-ribosyl)ation is a post-translational modification that is instantly stimulated by DNA strand breaks creating a unique signal for the modulation of protein functions in DNA repair and cell cycle checkpoint pathways. Here we report that lack of poly(ADP-ribose) synthesis leads to a compromised response to DNA damage. Deficiency in poly(ADP-ribosyl)ation metabolism induces profound cellular sensitivity to DNA-damaging agents, particularly in cells deficient for the protein kinase ataxia telangiectasia mutated (ATM). At the biochemical level, we examined the significance of poly(ADP-ribose) synthesis on the regulation of early DNA damage-induced signaling cascade initiated by ATM. Using potent PARP inhibitors and PARP-1 knock-out cells, we demonstrate a functional interplay between ATM and poly(ADP-ribose) that is important for the phosphorylation of p53, SMC1, and H2AX. For the first time, we demonstrate a functional and physical interaction between the major DSB signaling kinase, ATM and poly(ADP-ribosyl)ation by PARP-1, a key enzyme of chromatin remodeling. This study suggests that poly(ADP-ribose) might serve as a DNA damage sensory molecule that is critical for early DNA damage signaling.
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PMID:Ataxia telangiectasia mutated (ATM) signaling network is modulated by a novel poly(ADP-ribose)-dependent pathway in the early response to DNA-damaging agents. 1742 92

DNA double-strand breaks (DSBs) are caused by various environmental stresses, such as ionizing radiation and DNA-damaging agents. When DSBs occur, cell cycle checkpoint mechanisms function to stop the cell cycle until all DSBs are repaired; the phosphorylation of H2AX plays an important role in this process. Mouse preimplantation-stage embryos are hypersensitive to ionizing radiation, and X-irradiated mouse zygotes are arrested at the G2 phase of the first cell cycle. To investigate the mechanisms responding to DNA damage at G2 in mouse preimplantation embryos, we examined G2/M checkpoint and DNA repair mechanisms in these embryos. Most of the one- and two-cell embryos in which DSBs had been induced by gamma-irradiation underwent a delay in cleavage and ceased development before the blastocyst stage. In these embryos, phosphorylated H2AX (gamma-H2AX) was not detected in the one- or two-cell stages by immunocytochemistry, although it was detected after the two-cell stage during preimplantation development. These results suggest that the G2/M checkpoint and DNA repair mechanisms have insufficient function in one- and two-cell embryos, causing hypersensitivity to gamma-irradiation. In addition, phosphorylated ataxia telangiectasia mutated protein and DNA protein kinase catalytic subunits, which phosphorylate H2AX, were detected in the embryos at one- and two-cell stages, as well as at other preimplantation stages, suggesting that the absence of gamma-H2AX in one- and two-cell embryos depends on some factor(s) other than these kinases.
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PMID:Deficiency in the response to DNA double-strand breaks in mouse early preimplantation embryos. 1749 56

In this study, we examine the potential role of receptor-associated protein 80 (RAP80), a nuclear protein containing two ubiquitin-interacting motifs (UIM), in DNA damage response and double-strand break (DSB) repair. We show that following ionizing radiation and treatment with DNA-damaging agents, RAP80 translocates to discrete nuclear foci that colocalize with those of gamma-H2AX. The UIMs and the region of amino acids 204 to 304 are critical for the relocalization of RAP80 to ionizing radiation-induced foci (IRIF). These observations suggest that RAP80 becomes part of a DNA repair complex at the sites of IRIF. We also show that RAP80 forms a complex with the tumor repressor BRCA1 and that this interaction is mediated through the BRCA1 COOH-terminal repeats of BRCA1. The UIMs are not required for the interaction of RAP80 with BRCA1. Knockdown of RAP80 in HEK293 cells significantly reduced DSB-induced homology-directed recombination (HDR). Moreover, inhibition of RAP80 expression by small interfering RNA increased radiosensitivity, whereas increased radioresistance was observed in human breast cancer MCF-7 cells with overexpression of RAP80. Taken together, our data suggest that RAP80 plays an important role in DNA damage response signaling and HDR-mediated DSB repair. We further show that RAP80 can function as a substrate of the ataxia-telangiectasia mutated protein kinase in vitro, which phosphorylates RAP80 at Ser(205) and Ser(402). We show that this phosphorylation is not required for the migration of RAP80 to IRIF.
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PMID:The ubiquitin-interacting motif containing protein RAP80 interacts with BRCA1 and functions in DNA damage repair response. 1762 10

This review covers the topic of cytometric assessment of activation of Ataxia telangiectasia mutated (ATM) protein kinase and histone H2AX phosphorylation on Ser139 in response to DNA damage, particularly the damage that involves formation of DNA double-strand breaks. Briefly described are molecular mechanisms associated with activation of ATM and the downstream events that lead to recruitment of DNA repair machinery, engagement of cell cycle checkpoints, and activation of apoptotic pathway. Examples of multiparameter analysis of ATM activation and H2AX phosphorylation vis-a-vis cell cycle phase position and induction of apoptosis that employ flow- and laser scanning-cytometry are provided. They include cells treated with a variety of exogenous genotoxic agents, such as ionizing and UV radiation, DNA topoisomerase I (topotecan) and II (mitoxantrone, etoposide) inhibitors, nitric oxide-releasing aspirin, DNA replication inhibitors (aphidicolin, hydroxyurea, thymidine), and complex environmental carcinogens such as present in tobacco smoke. Also presented is an approach to identify DNA replicating (BrdU incorporating) cells based on selective photolysis of DNA that triggers H2AX phosphorylation. Listed are strategies to distinguish ATM activation and H2AX phosphorylation induced by primary DNA damage by genotoxic agents from those effects triggered by DNA fragmentation that takes place during apoptosis. While we review most published data, recent new findings also are included. Examples of multivariate analysis of ATM activation and H2AX phosphorylation presented in this review illustrate the advantages of cytometric flow- and image-analysis of these events in terms of offering a sensitive and valuable tool in studies of factors that induce DNA damage and/or affect DNA repair and allow one to explore the linkage between DNA damage, cell cycle checkpoints and initiation of apoptosis.
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PMID:Cytometry of ATM activation and histone H2AX phosphorylation to estimate extent of DNA damage induced by exogenous agents. 1762 68

Chromatin condensation and degradation of DNA into internucleosomal DNA fragments are key hallmarks of apoptosis. The phosphorylation of protein kinase ataxia telangiectasia mutated (ATM) and histone H2A.X was recently shown to occur concurrently with apoptotic DNA fragmentation. We have used immunofluorescence microscopy, Western blot analysis and alkali comet assays to show that phosphorylation of ATM in NIH3T3 fibroblasts occurs prior to apoptotic DNA fragmentation, nuclease degradation and phosphorylation of histone H2A.X in cells treated with low levels of either staurosporine (STS) or tumor necrosis factor-alpha mixed with cycloheximide (TNF-alpha/CHX). In extension to previous findings, ATM phosphorylation was associated with chromatin decondensation, i.e., by loss of dense foci of constitutive heterochromatin. These results suggest that chromatin is decondensed and that ATM is activated independently of DNA damage signaling pathways during the very early stages of apoptosis.
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PMID:Early-stage apoptosis is associated with DNA-damage-independent ATM phosphorylation and chromatin decondensation in NIH3T3 fibroblasts. 1794 18

The expressed sequence tags (ESTs) of normal mouse testis were obtained from online EST database ZooDDD. Their highly homologous EST sequences were found through the dbEST database to construct contigs, and spliced by the biomedical software Biolign. The corresponding exons and introns within genome sequences were predicted by software GeneScan. According to the open reading frame, the primers were designed. RT-PCR was applied in the cloning of novel gene from mouse testis and analyzing its expression pattern in various mouse tissues. The bioinformatics analysis on the sequencing results of TSEG-1 was conducted. Results indicated that a novel gene TSEG-1 was cloned from 1 668-2 011 kb of mouse X chromosome, with full-length sequence of 510 bp. The open reading frame (ORF) is 336 bp in length and en-codes a deduced amino acid sequence of 111 residues. The molecular weight of TSEG-1 protein is 12.84258 kDa, and its pI is 11.4000. RT-PCR demonstrated the correctness of its ORF. TSEG-1 was distinctively expressed in testis, but not in other tissues of mouse. No obvious homology with other mouse cDNA was found for TSEG-1. The GenBank accession number EU079024 was achieved. It was predicted that TSEG-1 is a kind of transmembrane protein, and the transmembrane domain is from 41 amino acid residue to 61 amino acid residue. Blastn analysis revealed its high homology to human testis-specific gene H2AX. Computational prediction of the 5'-untranslated region of TSEG-1 gene revealed a 680 bp-length promoter region. There are four antigen binding sites and two phosphorylation sites of specific protein kinase in TSEG-1 protein, with subcellular localization in mitochondria. The cloning of mouse testis specific gene TSEG-1 laid a foundation for subsequent research of its biological function and expression regulation.
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PMID:[Cloning and sequence analysis of TSEG-1, a novel gene specifically expressed in mouse testis]. 1833 6


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