Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P16104 (H2AX)
 3,930 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cellular activity of Yondelis (trabectedin, Ecteinascidin 743, Et743) is known to depend on transcription-coupled nucleotide excision repair (TCR). However, the subsequent cellular effects of Et743 are not fully understood. Here we show that Et743 induces both transcription- and replication-coupled DNA double-strand breaks (DSBs) that are detectible by neutral COMET assay and as gamma-H2AX foci that colocalize with 53BP1, Mre11, Ser(1981)-pATM, and Thr(68)-pChk2. The transcription coupled-DSBs (TC-DSBs) induced by Et743 depended both on TCR and Mre11-Rad50-Nbs1 (MRN) and were associated with DNA-PK-dependent gamma-H2AX foci. In contrast to DNA-PK, ATM phosphorylated H2AX both in NER-proficient and -deficient cells, but its full activation was dependent on H2AX as well as DNA-PK, suggesting a positive feedback loop: DNA-PK-gamma-H2AX-ATM. Knocking-out H2AX or inactivating DNA-PK reduced Et743's antiproliferative activity, whereas ATM and MRN tended to act as survival factors. Our results highlight the interplays between ATM and DNA-PK and their impacts on H2AX phosphorylation and cell survival. They also suggest that gamma-H2AX may serve as a biomarker in patients treated with Et743 and that molecular profiling of tumors for TCR, MRN, ATM, and DNA-PK might be useful to anticipate tumor response to Et743 treatment.
 ...
PMID:Transcription-coupled DNA double-strand breaks are mediated via the nucleotide excision repair and the Mre11-Rad50-Nbs1 complex. 1863 84

We have built an ion-microbeam for studies of the nuclear topography and kinetics of double-strand break repair at the single cell level. Here, we show that a first and a second, delayed single ion exposure at different nuclear sites led to comparable accumulations of phospho-ATM, gamma-H2AX and Mdc1 at both earlier (e) and later (l) microirradiated sites. In contrast, accumulations of 53BP1 and the recombination protein Rad51 were strongly reduced at l-sites. This apparent competition effect is accompanied by a reduced amount of 53BP1 in undamaged areas of the irradiated nuclei. We suggest that a critically limited pool size combined with strong binding at irradiated sites leads to the exhaustion of unbound factors freely roaming the nuclear space. The undersupply of these factors at l-sites requires in addition a long-lasting binding at e-sites or a weaker binding at l-sites. The observed effects suggest that DNA damage response at individual nuclear sites depends on the time course of damage load. This may have implications for therapeutic radiation treatments.
 ...
PMID:Competition effect in DNA damage response. 1864 39

Ataxia telangiectasia and Rad3-related (ATR) is a phosphoinositol-3-kinase like kinase (PIKK) that initiates a signal transduction response to replication fork stalling. Defects in ATR signalling have been reported in several disorders characterized by microcephaly and growth delay. Here, we gain insight into factors influencing the ATR signalling pathway and consider how they can be exploited for diagnostic purposes. Activation of ATR at stalled replication forks leads to intra-S and G2/M phase checkpoint arrest. ATR also phosphorylates gamma-H2AX at single-stranded (ss) DNA regions generated during nucleotide excision repair (NER) in non-replicating cells, but the critical analysis of any functional consequence has not been reported. Here, we show that UV irradiation of G2 phase cells causes ATR-dependent but replication-independent G2/M checkpoint arrest. This process requires the Nbs1 N-terminus encompassing the FHA and BRCT domains but not the Nbs1 C-terminus in contrast to ATM-dependent activation of G2/M arrest in response to ionizing radiation. Thus, Nbs1 has a function in ATR signalling in a manner distinct to any role at stalled replication forks. Replication-independent ATR signalling also requires the mediator proteins, 53BP1 and MDC1, providing direct evidence for their role in ATR signalling, but not H2AX. Finally, the process is activated in Cockayne's syndrome but not Xeroderma pigmentosum group A cells providing evidence that ssDNA regions generated during NER are the ATR-pathway-specific activating lesion. Replication-independent G2/M checkpoint arrest represents a suitable assay to specifically identify patients with defective ATR signalling, including Seckel syndrome, Nijmegen breakage syndrome and MCPH-1-dependent primary microcephaly.
 ...
PMID:Replication independent ATR signalling leads to G2/M arrest requiring Nbs1, 53BP1 and MDC1. 1866 57

Ions of high atomic number and energy (HZE particles) pose a significant cancer risk to astronauts on prolonged space missions. On Earth, similar ions are being used for targeted cancer therapy. The properties of these particles can be drastically altered during passage through spacecraft shielding, therapy beam modulators, or the human body. Here, we have used pertinent responses to DNA double-strand breaks (DSBs) to understand the consequences of energy loss versus nuclear fragmentation of Fe ions during passage through shielding or tissue-equivalent materials. Phosphorylation of histone H2AX and recruitment of 53BP1 were used to generate 3D reconstructions of DNA damage in human cells and to follow its repair. Human cells are unable to repair a significant portion of DNA damage induced by Fe ions. DNA-PK and ATM are required, to different extents, for the partial repair of Fe-induced DNA damage. Aluminum shielding has little effect on DNA damage or its repair, confirming that the hulls of the Space Shuttle and the International Space Station afford scant protection against these particles. Lead shielding, on the other hand, exacerbates the effects of Fe ions due to energy loss during particle traversal. In sharp contrast, polyethylene (PE), a favored hydrogenous shield, results in DNA damage that is more amenable to repair presumably due to Fe-ion fragmentation. Human cells are indeed able to efficiently repair DSBs induced by chlorine ions and protons that represent fragmentation products of Fe. Interestingly, activation of the tumor suppressor p53 in Fe-irradiated cells is uniquely biphasic and culminates in the induction of high levels of p21 (Waf1/Cip1), p16 (INK4a) and senescence-associated beta-galactosidase activity. Surprisingly, these events occur even in the absence of ATM kinase implying that ATR may be a major responder to the complex DNA damage inflicted by Fe ions. Significantly, fragmentation of the Fe beam through PE attenuates these responses and this, in turn, results in better long-term survival in a colony-forming assay. Our results help us to understand the biological consequences of ion fragmentation through materials, whether in space or in the clinic, and provide us with a biological basis for the use of hydrogenous materials like PE as effective space shields.
 ...
PMID:Modulation of the DNA-damage response to HZE particles by shielding. 1867 98

53BP1 plays important roles in checkpoint signaling and repair for DNA double-strand breaks. We found that a colon cancer cell line, SW48, expressed a splicing variant form of 53BP1, which lacks the residues corresponding to exons 10 and 11. Activation of ATM and phosphorylation of ATM and ATR targets occurred in SW48 cells in response to X-irradiation, and these X-ray-induced responses were not enhanced by expression of full-length 53BP1 in SW48 cells, indicating that this splicing variant fully activates the major checkpoint signaling in SW48 cells. In contrast, the expression of full-length 53BP1 in SW48 cells promoted the repair of X-ray-induced DNA damage, evidenced by faster disappearance of X-ray-induced gamma-H2AX foci, a marker for DNA damage, and less residual chromosomal aberrations after X-irradiation. We conclude that the two major roles of 53BP1, the checkpoint signaling and repair for DNA damage, can be functionally separated.
 ...
PMID:Characterization of a cancer cell line that expresses a splicing variant form of 53BP1: separation of checkpoint and repair functions in 53BP1. 1880 90

We have recently described frequency-dependent effects of mobile phone microwaves (MWs) of global system for mobile communication (GSM) on human lymphocytes from persons reporting hypersensitivity to electromagnetic fields and healthy persons. Contrary to GSM, universal global telecommunications system (UMTS) mobile phones emit wide-band MW signals. Hypothetically, UMTS MWs may result in higher biological effects compared to GSM signal because of eventual "effective" frequencies within the wideband. Here, we report for the first time that UMTS MWs affect chromatin and inhibit formation of DNA double-strand breaks co-localizing 53BP1/gamma-H2AX DNA repair foci in human lymphocytes from hypersensitive and healthy persons and confirm that effects of GSM MWs depend on carrier frequency. Remarkably, the effects of MWs on 53BP1/gamma-H2AX foci persisted up to 72 h following exposure of cells, even longer than the stress response following heat shock. The data are in line with the hypothesis that the type of signal, UMTS MWs, may have higher biological efficiency and possibly larger health risk effects compared to GSM radiation emissions. No significant differences in effects between groups of healthy and hypersensitive subjects were observed, except for the effects of UMTS MWs and GSM-915 MHz MWs on the formation of the DNA repair foci, which were different for hypersensitive (P < 0.02[53BP1]//0.01[gamma-H2AX]) but not for control subjects (P > 0.05). The non-parametric statistics used here did not indicate specificity of the differences revealed between the effects of GSM and UMTS MWs on cells from hypersensitive subjects and more data are needed to study the nature of these differences.
 ...
PMID:Microwaves from UMTS/GSM mobile phones induce long-lasting inhibition of 53BP1/gamma-H2AX DNA repair foci in human lymphocytes. 1883 14

We have shown previously that SNM1A colocalizes with 53BP1 at sites of double-strand breaks (DSBs) induced by IR, and that these proteins interact with or without DNA damage. However, the role of SNM1A in the DNA damage response has not been elucidated. Here, we show that SNM1A is required for an efficient G1 checkpoint arrest after IR exposure. Interestingly, the localization of SNM1A to sites of DSBs does not require either 53BP1 or H2AX, nor does the localization of 53BP1 require SNM1A. However, the localization of SNM1A does require ATM. Furthermore, SNM1A is shown to be a phosphorylation substrate of ATM in vitro, and to interact with ATM in vivo particularly after exposure of cells to IR. In addition, in the absence of SNM1A the activation of the downstream ATM target p53 is reduced. These findings suggest that SNM1A acts with ATM to promote the G1 cell cycle checkpoint.
 ...
PMID:SNM1A acts downstream of ATM to promote the G1 cell cycle checkpoint. 1884 20

Simian virus 40 (SV40) large T antigen (LT) is a multifunctional protein that is important for viral replication and oncogenic transformation. Previously, infection of monkey or human cells with SV40 was shown to lead to the induction of DNA damage response signaling, which is required for efficient viral replication. However, it was not clear if LT is sufficient to induce the damage response and, if so, what the genetic requirements and functional consequences might be. Here, we show that the expression of LT alone, without a replication origin, can induce key DNA damage response markers including the accumulation of gamma-H2AX and 53BP1 in nuclear foci. Other DNA damage-signaling components downstream of ATM/ATR kinases were induced, including chk1 and chk2. LT also bound the Claspin mediator protein, which normally facilitates the ATR activation of chk1 and monitors cellular replication origins. Stimulation of the damage response by LT depends mainly on binding to Bub1 rather than to the retinoblastoma protein. LT has long been known to stabilize p53 despite functionally inactivating it. We show that the activation of a DNA damage response by LT via Bub1 appears to play a major role in p53 stabilization by promoting the phosphorylation of p53 at Ser15. Accompanying the DNA damage response, LT induces tetraploidy, which is also dependent on Bub1 binding. Taken together, our data suggest that LT, via Bub1 binding, breaches genome integrity mechanisms, leading to DNA damage responses, p53 stabilization, and tetraploidy.
 ...
PMID:Simian virus 40 large T antigen disrupts genome integrity and activates a DNA damage response via Bub1 binding. 1892 73

Variable, diversity and joining (V(D)J) recombination and class-switch recombination use overlapping but distinct non-homologous end joining pathways to repair DNA double-strand-break intermediates. 53BP1 is a DNA-damage-response protein that is rapidly recruited to sites of chromosomal double-strand breaks, where it seems to function in a subset of ataxia telangiectasia mutated (ATM) kinase-, H2A histone family member X (H2AX, also known as H2AFX)- and mediator of DNA damage checkpoint 1 (MDC1)-dependent events. A 53BP1-dependent end-joining pathway has been described that is dispensable for V(D)J recombination but essential for class-switch recombination. Here we report a previously unrecognized defect in the joining phase of V(D)J recombination in 53BP1-deficient lymphocytes that is distinct from that found in classical non-homologous-end-joining-, H2ax-, Mdc1- and Atm-deficient mice. Absence of 53BP1 leads to impairment of distal V-DJ joining with extensive degradation of unrepaired coding ends and episomal signal joint reintegration at V(D)J junctions. This results in apoptosis, loss of T-cell receptor alpha locus integrity and lymphopenia. Further impairment of the apoptotic checkpoint causes propagation of lymphocytes that have antigen receptor breaks. These data suggest a more general role for 53BP1 in maintaining genomic stability during long-range joining of DNA breaks.
 ...
PMID:53BP1 facilitates long-range DNA end-joining during V(D)J recombination. 1893 58

The DNA damage response mediators, 53BP1 and MDC1, play a central role in checkpoint activation and DNA repair. Here we establish that human 53BP1 and MDC1 interact directly through the tandem BRCT domain of MDC1 and residues 1288-1409 of 53BP1. Following induction of DNA double strand breaks the interaction is reduced, probably due to competition between gamma-H2AX and 53BP1 for the binding of the tandem BRCT domain of MDC1. Furthermore, the MDC1 binding region of 53BP1 is required for focus formation by 53BP1. During mitosis the interaction between 53BP1 and MDC1 is enhanced. The interaction is augmented in a phospho-dependent manner, and the MDC1 binding region of 53BP1 is phosphorylated in vivo in mitotic cells; therefore, it is probably modulated by cell cycle-regulated kinases. Our results demonstrate that the 53BP1-MDC1 interaction per se is required for the recruitment of 53BP1 to sites of DNA breaks, which is known to be crucial for an efficient activation of the DNA damage response. Moreover, the results presented here suggest that the interaction between 53BP1 and MDC1 plays a role in the regulation of mitosis.
 ...
PMID:The direct interaction between 53BP1 and MDC1 is required for the recruitment of 53BP1 to sites of damage. 1898 80


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