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

The WRN protein is mutated in the chromosomally unstable Werner syndrome (WS) and the Nbs1 protein is mutated in Nijmegen breakage syndrome (NBS). The Nbs1 protein is an integral component of the M/R/N complex. Although WRN is known to interact with this complex in response to gamma-irradiation, the mechanism of action is unclear. Here, we show that WRN co-localizes and associates with gamma H2AX, a marker protein of DNA double strand breaks (DSBs), after cellular exposure to gamma-irradiation. While the DNA damage-inducible Nbs1 foci formation is normal in WS cells, WRN focus formation is defective in NBS cells. Consistent with this, gamma H2AX colocalizes with Nbs1 in WS cells but not with WRN in NBS cells. The defective WRN-gamma H2AX association in NBS cells can be complemented with wild-type Nbs1, but not with an Nbs1 S343A point mutant that lacks an ATM phosphorylation site. WRN associates with H2AX in a manner dependent upon the M/R/N complex. Our results suggest a novel pathway in which Nbs1 may recruit WRN to the site of DNA DSBs in an ATM-dependent manner.
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PMID:Werner syndrome protein associates with gamma H2AX in a manner that depends upon Nbs1. 1573 40

Werner syndrome is an autosomal recessive accelerated-aging disorder caused by a defect in the WRN gene, which encodes a member of the RecQ family of DNA helicases with an exonuclease activity. In vitro experiments have suggested that WRN functions in several DNA repair processes, but the actual functions of WRN in living cells remain unknown. Here, we analyzed the kinetics of the intranuclear mobilization of WRN protein in response to a variety of types of DNA damage produced locally in the nucleus of human cells. A striking accumulation of WRN was observed at laser-induced double-strand breaks, but not at single-strand breaks or oxidative base damage. The accumulation of WRN at double-strand breaks was rapid, persisted for many hours, and occurred in the absence of several known interacting proteins including polymerase beta, poly(ADP-ribose) polymerase 1 (PARP1), Ku80, DNA-dependent protein kinase (DNA-PKcs), NBS1 and histone H2AX. Abolition of helicase activity or deletion of the exonuclease domain had no effect on accumulation, whereas the presence of the HRDC (helicase and RNaseD C-terminal) domain was necessary and sufficient for the accumulation. Our data suggest that WRN functions mainly at DNA double-strand breaks and structures resembling double-strand breaks in living cells, and that an autonomous accumulation through the HRDC domain is the initial response of WRN to the double-strand breaks.
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PMID:Accumulation of Werner protein at DNA double-strand breaks in human cells. 1614 Dec 34

Werner syndrome (WS) is an autosomal recessive disease characterized by multiple progeroid features. The gene responsible for WS, WRN, is a member of the human RecQ helicase family. WRN is unique among this family, associated with an exonuclease activity. In the present study, we established the human 293-derived cell lines, which expressed exogenously truncated WRN protein, lacking the N-terminal exonuclease domain but having normal helicase activity, and found that they were slightly, but nonetheless significantly, radiosensitive than control cell lines, into which the empty vector had been introduced. The truncated WRN-expressing cells also exhibited increased numbers of micronuclei, chromosome aberrations, and the foci of phosphorylated histone H2AX with X-rays. These results suggested a function of WRN exonuclease activity that is separable from helicase activity and is essential for the repair of radiation-induced DNA damages.
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PMID:Exogenous expression of exonuclease domain-deleted WRN interferes with the repair of radiation-induced DNA damages. 1639 31

Telomeres cap the ends of eukaryotic chromosomes and prevent them from being recognized as DNA breaks. We have shown that certain DNA damage responses induced during senescence and, at times of telomere uncapping, also can be induced by treatment of cells with small DNA oligonucleotides homologous to the telomere 3' single-strand overhang (T-oligos), implicating this overhang in generation of these telomere-based damage responses. Here, we show that T-oligo-treated fibroblasts contain gammaH2AX foci and that these foci colocalize with telomeres. T-oligos with nuclease-resistant 3' ends are inactive, suggesting that a nuclease initiates T-oligo responses. We therefore examined WRN, a 3'-->5' exonuclease and helicase mutated in Werner syndrome, a disorder characterized by aberrant telomere maintenance, premature aging, chromosomal rearrangements, and predisposition to malignancy. Normal fibroblasts and U20S osteosarcoma cells rendered deficient in WRN showed reduced phosphorylation of p53 and histone H2AX in response to T-oligo treatment. Together, these data demonstrate a role for WRN in processing of telomeric DNA and subsequent activation of DNA damage responses. The T-oligo model helps define the role of WRN in telomere maintenance and initiation of DNA damage responses after telomere disruption.
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PMID:A role for WRN in telomere-based DNA damage responses. 1701 33

Accumulation of DNA damage may play an essential role in both cellular senescence and organismal aging. The ability of cells to sense and repair DNA damage declines with age. However, the underlying molecular mechanism for this age-dependent decline is still elusive. To understand quantitative and qualitative changes in the DNA damage response during human aging, DNA damage-induced foci of phosphorylated histone H2AX (gamma-H2AX), which occurs specifically at sites of DNA double-strand breaks (DSBs) and eroded telomeres, were examined in human young and senescing fibroblasts, and in lymphocytes of peripheral blood. Here, we show that the incidence of endogenous gamma-H2AX foci increases with age. Fibroblasts taken from patients with Werner syndrome, a disorder associated with premature aging, genomic instability and increased incidence of cancer, exhibited considerably higher incidence of gamma-H2AX foci than those taken from normal donors of comparable age. Further increases in gamma-H2AX focal incidence occurred in culture as both normal and Werner syndrome fibroblasts progressed toward senescence. The rates of recruitment of DSB repair proteins to gamma-H2AX foci correlated inversely with age for both normal and Werner syndrome donors, perhaps due in part to the slower growth of gamma-H2AX foci in older donors. Because genomic stability may depend on the efficient processing of DSBs, and hence the rapid formation of gamma-H2AX foci and the rapid accumulation of DSB repair proteins on these foci at sites of nascent DSBs, our findings suggest that decreasing efficiency in these processes may contribute to genome instability associated with normal and pathological aging.
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PMID:Delayed kinetics of DNA double-strand break processing in normal and pathological aging. 1800 50

Five members of the RecQ subfamily of DEx-H-containing DNA helicases have been identified in both human and mouse, and mutations in BLM, WRN, and RECQ4 are associated with human diseases of premature aging, cancer, and chromosomal instability. Although a genetic disease has not been linked to RECQ1 mutations, RECQ1 helicase is the most highly expressed of the human RecQ helicases, suggesting an important role in cellular DNA metabolism. Recent advances have elucidated a unique role of RECQ1 to suppress genomic instability. Embryonic fibroblasts from RECQ1-deficient mice displayed aneuploidy, chromosomal instability, and increased load of DNA damage.(1) Acute depletion of human RECQ1 renders cells sensitive to DNA damage and results in spontaneous gamma-H2AX foci and elevated sister chromatid exchanges, indicating aberrant repair of DNA breaks.(2) Consistent with a role in DNA repair, RECQ1 relocalizes to irradiation-induced nuclear foci and associates with chromatin.(2) RECQ1 catalytic activities(3) and interactions with DNA repair proteins(2,4,5) are likely to be important for its molecular functions in genome homeostasis. Collectively, these studies provide the first evidence for an important role of RECQ1 to confer chromosomal stability that is unique from that of other RecQ helicases and suggest its potential involvement in tumorigenesis.
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PMID:Unique and important consequences of RECQ1 deficiency in mammalian cells. 1841 32

Werner syndrome (WS) is a human genetic disorder characterized by extensive clinical features of premature aging. Ataxia-telengiectasia (A-T) is a multisystem human genomic instability syndrome that includes premature aging in some of the patients. WRN and ATM, the proteins defective in WS and A-T, respectively, play significant roles in the maintenance of genomic stability and are involved in several DNA metabolic pathways. A role for WRN in DNA repair has been proposed; however, this study provides evidence that WRN is also involved in ATM pathway activation and in a S-phase checkpoint in cells exposed to DNA interstrand cross-link-induced double-strand breaks. Depletion of WRN in such cells by RNA interference results in an intra-S checkpoint defect, and interferes with activation of ATM as well as downstream phosphorylation of ATM target proteins. Treatment of cells under replication stress with the ATM kinase inhibitor KU 55933 results in a S-phase checkpoint defect similar to that observed in WRN shRNA cells. Moreover, gamma H2AX levels are higher in WRN shRNA cells than in control cells 6 and 16 h after exposure to psoralen DNA cross-links. These results suggest that WRN and ATM participate in a replication checkpoint response, in which WRN facilitates ATM activation in cells with psoralen DNA cross-link-induced collapsed replication forks.
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PMID:WRN is required for ATM activation and the S-phase checkpoint in response to interstrand cross-link-induced DNA double-strand breaks. 1859 39

Resveratrol decreases cancer risk and improves health of laboratory animals. However, it can also promote genomic instability. Part of the beneficial activity of resveratrol may result from the activation of SIRT1 deacetylase. We examined how resveratrol influenced the growth of human cancer cell lines of different origin: osteosarcoma (U-2 OS) and lung adenocarcinoma (A549) and how it modulated the expression as well as the localization of key proteins, involved in DNA repair and cell cycle regulation. Resveratrol-induced growth arrest was associated with signs of stress-induced senescence. Differential expression of BRCA1, cyclin B1, pRb and p21 in U-2 OS and A549 cells indicates that resveratrol can engage various molecular mechanisms to arrest cell cycle progression. In subset of U-2 OS cells, the upregulated BRCA1 formed foci closely associated with WRN and the telomeric protein (TRF1). Moreover, resveratrol induced telomeric instability in U-2 OS cells and the activation of DNA damage signaling in both cell lines, manifested as the phosphorylation of histone H2AX at serine 139 and of p53 at serines 15 and 37. Our data are consistent with the hypothesis that resveratrol inhibits cell growth and induces senescence by altering DNA metabolism.
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PMID:Resveratrol induces senescence-like growth inhibition of U-2 OS cells associated with the instability of telomeric DNA and upregulation of BRCA1. 1955 22

Recent studies in yeast have found that processing of DNA double-strand breaks (DSB) for recombination repair involves Sgs1 helicase. Human cells have five Sgs1 homologues with unknown selectivity and significance for repair of different DSB types. Here we examined the importance of WRN helicase in repair of G(2)-specific DSB caused by abnormal mismatch repair (MMR) of ternary Cr-DNA adducts. We found that Cr(VI) induced a rapid dispersal of WRN from the nucleolus resulting in its prolonged retention in the nucleoplasm. The loss of MSH2 or MLH1 MMR proteins abolished the long-term but not the initial WRN relocalization. WRN-deficient fibroblasts were hypersensitive to Cr(VI)-induced clonogenic death and contained high levels of persistent DSB detected by gamma-H2AX/53BP1 foci and pulsed-field gel electrophoresis. WRN was involved in recombination repair of Cr-induced DNA damage, as evidenced by WRN-RAD51 colocalization and defective formation of RAD51 foci in the absence of WRN. The accumulation of unrepaired DSB in WRN-depleted cells was rescued by the inactivation of MMR, indicating that MMR-generated DSB were a key substrate for WRN action in Cr(VI)-treated cells. Competition for the limited amounts of WRN in primary cells between G(2) processes of telomere rebuilding and recombinational repair is expected to increase persistence of Cr-induced DSB and may cause telomeric abnormalities in tissues of chronically chromate-exposed workers. Our work provides the first demonstration of the major importance of WRN in repair of a specific class of DSB in human cells.
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PMID:WRN helicase promotes repair of DNA double-strand breaks caused by aberrant mismatch repair of chromium-DNA adducts. 1965 51

Loss-of-function mutations in the human RecQ helicase genes WRN and BLM respectively cause the genetic instability/cancer predisposition syndromes Werner syndrome and Bloom syndrome. To identify common and unique functions of WRN and BLM, we systematically analyzed cell proliferation, cell survival, and genomic damage in isogenic cell lines depleted of WRN, BLM, or both proteins. Cell proliferation and survival were assessed before and after treatment with camptothecin, cis-diamminedichloroplatinum(II), hydroxyurea, or 5-fluorouracil. Genomic damage was assessed, before and after replication arrest, by gamma-H2AX staining, which was quantified at the single-cell level by flow cytometry. Cell proliferation was affected strongly by the extent of WRN and/or BLM depletion, and more strongly by BLM than by WRN depletion (P = 0.005). The proliferation of WRN/BLM-codepleted cells, in contrast, did not differ from BLM-depleted cells (P = 0.34). BLM-depleted and WRN/BLM-codepleted cells had comparably impaired survival after DNA damage, whereas WRN-depleted cells displayed a distinct pattern of sensitivity to DNA damage. BLM-depleted and WRN/BLM-codepleted cells had similar, significantly higher gamma-H2AX induction levels than did WRN-depleted cells. Our results provide new information on the role of WRN and BLM in determining cell proliferation, cell survival, and genomic damage after chemotherapeutic DNA damage or replication arrest. We also provide new information on functional redundancy between WRN and BLM. These results provide a strong rationale for further developing WRN and BLM as biomarkers of tumor chemotherapeutic responsiveness.
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PMID:The human WRN and BLM RecQ helicases differentially regulate cell proliferation and survival after chemotherapeutic DNA damage. 2066 5


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