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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mammalian ATR and ATM checkpoint kinases modulate chromatin structures near DNA breaks by phosphorylating a serine residue in the carboxy-terminal tail SQE motif of histone H2AX. Histone H2A is similarly regulated in Saccharomyces cerevisiae. The phosphorylated forms of H2AX and H2A, known as gamma-H2AX and gamma-H2A, are thought to be important for DNA repair, although their evolutionarily conserved roles are unknown. Here, we investigate gamma-H2A in the fission yeast Schizosaccharomyces pombe. We show that formation of gamma-H2A redundantly requires the ATR/ATM-related kinases Rad3 and Tel1. Mutation of the SQE motif to AQE (H2A-AQE) in the two histone H2A genes caused sensitivity to a wide range of genotoxic agents, increased spontaneous DNA damage, and impaired checkpoint maintenance. The H2A-AQE mutations displayed a striking synergistic interaction with rad22Delta (Rad52 homolog) in ionizing radiation (IR) survival. These phenotypes correlated with defective phosphorylation of the checkpoint proteins Crb2 and Chk1 and a failure to recruit large amounts of Crb2 to damaged DNA. Surprisingly, the H2A-AQE mutations substantially suppressed the IR hypersensitivity of crb2Delta cells by a mechanism that required the RecQ-like DNA helicase Rqh1. We propose that gamma-H2A modulates checkpoint and DNA repair through large-scale recruitment of Crb2 to damaged DNA. This function correlates with evidence that gamma-H2AX regulates recruitment of several BRCA1 carboxyl terminus domain-containing proteins (NBS1, 53BP1, MDC1/NFBD1, and BRCA1) in mammals.
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PMID:Histone H2A phosphorylation controls Crb2 recruitment at DNA breaks, maintains checkpoint arrest, and influences DNA repair in fission yeast. 1522 25

The cellular responses to double-stranded breaks (DSBs) typically involve the extensive accumulation of checkpoint proteins in chromatin surrounding the damaged DNA. One well-characterized example involves the checkpoint protein Crb2 in the fission yeast Schizosaccharomyces pombe. The accumulation of Crb2 at DSBs requires the C-terminal phosphorylation of histone H2A (known as gamma-H2A) by ATM family kinases in chromatin surrounding the break. It also requires the constitutive methylation of histone H4 on lysine-20 (K20). Interestingly, neither type of histone modification is essential for the Crb2-dependent checkpoint response. However, H4-K20 methylation is essential in a crb2-T215A strain that lacks a cyclin-dependent kinase phosphorylation site in Crb2. Here we explain this genetic interaction by describing a previously overlooked effect of the crb2-T215A mutation. We show that crb2-T215A cells are able to initiate but not sustain a checkpoint response. We also report that gamma-H2A is essential for the DNA damage checkpoint in crb2-T215A cells. Importantly, we show that inactivation of Cdc2 in gamma-H2A-defective cells impairs Crb2-dependent signaling to the checkpoint kinase Chk1. These findings demonstrate that full Crb2 activity requires phosphorylation of threonine-215 by Cdc2. This regulation of Crb2 is independent of the histone modifications that are required for the hyperaccumulation of Crb2 at DSBs.
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PMID:Cooperative control of Crb2 by ATM family and Cdc2 kinases is essential for the DNA damage checkpoint in fission yeast. 1631 98

Chromatin changes within the context of DNA repair remain largely obscure. Here we show that DNA damage induces monoubiquitylation of histone H2A in the vicinity of DNA lesions. Ultraviolet (UV)-induced monoubiquitylation of H2A is dependent on functional nucleotide excision repair and occurs after incision of the damaged strand. The ubiquitin ligase Ring2 is required for the DNA damage-induced H2A ubiquitylation. UV-induced ubiquitylation of H2A is dependent on the DNA damage signaling kinase ATR (ATM- and Rad3-related) but not the related kinase ATM (ataxia telangiectasia-mutated). Although the response coincides with phosphorylation of variant histone H2AX, H2AX was not required for H2A ubiquitylation. Together our data show that monoubiquitylation of H2A forms part of the cellular response to UV damage and suggest a role of this modification in DNA repair-induced chromatin remodeling.
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PMID:DNA damage triggers nucleotide excision repair-dependent monoubiquitylation of histone H2A. 1670 7

Recent studies of yeast G1 DNA damage response have identified characteristic changes in chromatin adjacent to double-strand breaks (DSBs). Histone H2A (yeast H2AX) is rapidly phosphorylated on S129 by the kinase Tel1 (ATM) over a domain extending kilobases from the DSB. The adaptor protein Rad9 (53BP1) is recruited to this chromatin domain through binding of its tudor domains to histone H3 diMe-K79. Multisite phosphorylation of Rad9 by Mec1 (ATR) then activates the signaling kinase Rad53 (CHK2) to induce a delay in G1. Here, we report a previously undescribed role for Tel1 in G1 checkpoint response and show that H2A is the likely phosphorylation target, in a much as S129 mutation to Ala confers defects in G1 checkpoint arrest, Rad9 phosphorylation, and Rad53 activation. Importantly, Rad9 fails to bind chromatin adjacent to DSBs in H2A-S129A mutants. Previous work showed that H2A phosphorylation allows binding of NuA4, SWR, and INO80 chromatin remodeling complexes, perhaps exposing H3 diMe-K79. Yet, mutants lacking SWR or INO80 remain checkpoint competent, whereas loss of NuA4-dependent histone acetylation leads to G1 checkpoint persistence, suggesting that H2A phosphorylation promotes two independent events, rapid Rad9 recruitment to DSBs and subsequent remodeling by NuA4, SWR, and INO80.
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PMID:Yeast G1 DNA damage checkpoint regulation by H2A phosphorylation is independent of chromatin remodeling. 1694 Mar 59

The detection of a DNA double-strand break (DSB) is necessary to initiate DSB repair. Several proteins, including the MRX/N complex, Tel1/ATM (ataxia telangiectasia mutated), and Mec1/ATR (ATM and Rad3 related), have been proposed as sensors of DNA damage, yet how they recognize the breaks is poorly understood. DSBs occur in the context of chromatin, implicating factors capable of altering local and/or global chromatin structure in the cellular response to DNA damage, including DSB sensing. Emerging evidence indicates that ATP-dependent chromatin-remodeling complexes function in DNA repair. Here we describe an important and novel early role for the RSC ATP-dependent chromatin remodeler linked to DSB sensing in the cell's DNA-damage response. RSC is required for full levels of H2A phosphorylation because it facilitates the recruitment of Tel1/ATM and Mec1/ATR to the break site. Consistent with these results, we also show that Rsc2 is needed for efficient activation of the Rad53-dependent checkpoint, as well as for Cohesin's association with the break site. Finally, Rsc2 is needed for the DNA-damage-induced changes in nucleosome structure surrounding the DSB site. Together, these new findings functionally link RSC to DSB sensing, highlighting the importance of ATP-dependent chromatin-remodeling factors in the cell's early response to DNA damage.
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PMID:RSC functions as an early double-strand-break sensor in the cell's response to DNA damage. 1768 60

Chromosomal double-strand breaks (DSBs) in eukaryotes provoke a rapid, extensive modification in chromatin flanking the breaks. The DNA damage response (DDR) coordinates activation of cell cycle checkpoints, apoptosis, and DNA repair networks, to ensure accurate repair and genomic integrity. The checkpoint kinase ATM plays a critical role in the initiation of DDR in response to DSBs. The early ATM-mediated phosphorylation of the histone variant H2AX proteins near DSBs leads to the subsequent binding of MDC1, which functions as a scaffold for the recruitment and assembly of many DDR mediators and effectors, including BRCA1. Recent studies have provided new insights into the mechanism by which BRCA1 and associated proteins are recruited to DNA damage foci and revealed key roles for the receptor-associated protein 80 (RAP80) and the E3 ligase RNF8 in this process. RAP80 is an ubiquitin-interaction motif (UIM) containing protein that is associated with a BRCA1/BARD1 complex through its interaction with CCDC98 (Abraxas). The UIMs of RAP80 are critical for targeting this protein complex to DSB sites. Additional studies revealed that after binding gamma-H2AX, ATM-phosphorylated MDC1 is recognized by the FHA domain of RNF8, which subsequently binds the E2 conjugating enzyme UBC13. This complex catalyzes K63-linked polyubiquitination of histones H2A and gamma-H2AX, which are then recognized by the UIMs of RAP80, thereby facilitating the recruitment of the BRCA1/BARD1/CCDC98/RAP80 protein complex to DSB sites. Depletion of RAP80 or RNF8 impairs the translocation of BRCA1 to DNA damage sites and results in defective cell cycle checkpoint control and DSB repair. In this review, we discuss this cascade of protein phosphorylation and ubiquitination and the role it plays in the control of cellular responses to genotoxic stress by regulating the interactions, localization, and function of DDR proteins.
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PMID:RAP80 and RNF8, key players in the recruitment of repair proteins to DNA damage sites. 1855 Feb 71

The conserved histone variant H2A.Z fulfills many functions by being an integral part of the nucleosomes placed at specific regions of the genome. Telomeres cap natural ends of chromosomes to prevent their recognition as double-strand breaks. At yeast telomeres, H2A.Z prevents the spreading of silent chromatin into proximal euchromatin. A role for H2A.Z in capping, however, has not been reported in any organism. Here, I uncover such a role for Drosophila H2A.Z. Loss of H2A.Z, through mutations in either its gene or the domino gene for the Swr1 chromatin-remodeling protein, suppressed the fusion of telomeres that lacked the protection of checkpoint proteins: ATM, ATR, and the Mre11-Rad50-NBS complex. Loss of H2A.Z partially restores the loading of the HOAP capping protein, possibly accounting for the partial restoration in capping. I propose that, in the absence of H2A.Z, checkpoint-defective telomeres adopt alternative structures, which are permissive for the loading of the capping machinery at Drosophila telomeres.
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PMID:Loss of the histone variant H2A.Z restores capping to checkpoint-defective telomeres in Drosophila. 1884 40

The biological response to DNA double-strand breaks acts to preserve genome integrity. Individuals bearing inactivating mutations in components of this response exhibit clinical symptoms that include cellular radiosensitivity, immunodeficiency, and cancer predisposition. The archetype for such disorders is Ataxia-Telangiectasia caused by biallelic mutation in ATM, a central component of the DNA damage response. Here, we report that the ubiquitin ligase RNF168 is mutated in the RIDDLE syndrome, a recently discovered immunodeficiency and radiosensitivity disorder. We show that RNF168 is recruited to sites of DNA damage by binding to ubiquitylated histone H2A. RNF168 acts with UBC13 to amplify the RNF8-dependent histone ubiquitylation by targeting H2A-type histones and by promoting the formation of lysine 63-linked ubiquitin conjugates. These RNF168-dependent chromatin modifications orchestrate the accumulation of 53BP1 and BRCA1 to DNA lesions, and their loss is the likely cause of the cellular and developmental phenotypes associated with RIDDLE syndrome.
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PMID:The RIDDLE syndrome protein mediates a ubiquitin-dependent signaling cascade at sites of DNA damage. 1920 78

Chromatin modifications are an important component of the of DNA damage response (DDR) network that safeguard genomic integrity. Recently, we demonstrated nucleotide excision repair (NER)-dependent histone H2A ubiquitination at sites of ultraviolet (UV)-induced DNA damage. In this study, we show a sustained H2A ubiquitination at damaged DNA, which requires dynamic ubiquitination by Ubc13 and RNF8. Depletion of these enzymes causes UV hypersensitivity without affecting NER, which is indicative of a function for Ubc13 and RNF8 in the downstream UV-DDR. RNF8 is targeted to damaged DNA through an interaction with the double-strand break (DSB)-DDR scaffold protein MDC1, establishing a novel function for MDC1. RNF8 is recruited to sites of UV damage in a cell cycle-independent fashion that requires NER-generated, single-stranded repair intermediates and ataxia telangiectasia-mutated and Rad3-related protein. Our results reveal a conserved pathway of DNA damage-induced H2A ubiquitination for both DSBs and UV lesions, including the recruitment of 53BP1 and Brca1. Although both lesions are processed by independent repair pathways and trigger signaling responses by distinct kinases, they eventually generate the same epigenetic mark, possibly functioning in DNA damage signal amplification.
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PMID:Nucleotide excision repair-induced H2A ubiquitination is dependent on MDC1 and RNF8 and reveals a universal DNA damage response. 1979 77

ATM(Tel1) and ATR(Rad3) checkpoint kinases phosphorylate the C-terminus of histone H2AX (H2A in yeasts) in chromatin flanking DNA damage, establishing a recruitment platform for checkpoint and repair proteins. Phospho-H2A/X (gammaH2A/X)-binding proteins at double-strand breaks (DSBs) have been characterized, but those required for replication stress responses are unknown. Here, we present genetic, biochemical, small angle X-ray scattering (SAXS), and X-ray structural studies of the Schizosaccharomyces pombe Brc1, a 6-BRCT-domain protein that is structurally related to Saccharomyces cerevisiae Rtt107 and mammalian PTIP. Brc1 binds gammaH2A to form spontaneous and DNA damage-induced nuclear foci. Spontaneous Brc1 foci colocalize with ribosomal DNA repeats, a region prone to fork pausing and genomic instability, whereas DNA damage-induced Brc1 foci colocalize with DSB response factors. gammaH2A binding is critical for Brc1 function. The 1.45 A resolution crystal structure of Brc1-gammaH2A complex shows how variable BRCT insertion loops sculpt tandem-BRCT phosphoprotein-binding pockets to facilitate unique phosphoprotein-interaction specificities, and unveils an acidic DNA-mimicking Brc1 surface. From these results, Brc1 docking to gammaH2A emerges as a critical chromatin-specific response to replication-associated DNA damage.
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PMID:gammaH2A binds Brc1 to maintain genome integrity during S-phase. 2009 29


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