Fine Localization of the Nijmegen Breakage Syndrome Gene to 8q21: Evidence for a Common Founder Haplotype

Cerosaletti, Karen; Lange, Ethan M.; Stringham, Heather M.; Weemaes, C.M.R.; Smeets, Dominique; Sölder, B; Belohradsky, Bernd H.; Taylor, Alexander M.; Karnes, Pamela S.; Elliott, Alison M.; Komatsu, Kenshi; Gatti, Richard A.; Boehnke, Michael; Concannon, Patrick

doi:10.1086/301927

Cited by 47 publications

(25 citation statements)

References 18 publications

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“…The overlapping cellular abnormalities between AT and NBS prompted us to determine the impact of Nbs1 deficiency on Chk2 regulation. The NBS-derived LCL 1548 and GM07078A, homozygous for truncation mutations of the NBS1 gene (835de14 and 657de15, respectively) (7,47,49) were, unlike normal and AT cells, negative for Nbs1 protein ( Fig. 2A).…”

Section: Atm-dependent Chk2 Phosphorylation In Normal Cell Linesmentioning

confidence: 99%

Chk2 Activation Dependence on Nbs1 after DNA Damage

Buscemi

Savio

Zannini

et al. 2001

Molecular and Cellular Biology

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The checkpoint kinase Chk2 has a key role in delaying cell cycle progression in response to DNA damage. Upon activation by low-dose ionizing radiation (IR), which occurs in an ataxia telangiectasia mutated (ATM)-dependent manner, Chk2 can phosphorylate the mitosis-inducing phosphatase Cdc25C on an inhibitory site, blocking entry into mitosis, and p53 on a regulatory site, causing G 1 arrest. Here we show that the ATMdependent activation of Chk2 by ␥-radiation requires Nbs1, the gene product involved in the Nijmegen breakage syndrome (NBS), a disorder that shares with AT a variety of phenotypic defects including chromosome fragility, radiosensitivity, and radioresistant DNA synthesis. Thus, whereas in normal cells Chk2 undergoes a time-dependent increased phosphorylation and induction of catalytic activity against Cdc25C, in NBS cells null for Nbs1 protein, Chk2 phosphorylation and activation are both defective. Importantly, these defects in NBS cells can be complemented by reintroduction of wild-type Nbs1, but neither by a carboxyterminal deletion mutant of Nbs1 at amino acid 590, unable to form a complex with and to transport Mre11 and Rad50 in the nucleus, nor by an Nbs1 mutated at Ser343 (S343A), the ATM phosphorylation site. Chk2 nuclear expression is unaffected in NBS cells, hence excluding a mislocalization as the cause of failed Chk2 activation in Nbs1-null cells. Interestingly, the impaired Chk2 function in NBS cells correlates with the inability, unlike normal cells, to stop entry into mitosis immediately after irradiation, a checkpoint abnormality that can be corrected by introduction of the wild-type but not the S343A mutant form of Nbs1. Altogether, these findings underscore the crucial role of a functional Nbs1 complex in Chk2 activation and suggest that checkpoint defects in NBS cells may result from the inability to activate Chk2.The integrity of genetic information is essential for the life and survival of cells. Genomic lesions arising spontaneously during DNA replication or in response to oxidative metabolism or exposure to radiation or chemical mutagens need to be recognized and repaired. Delay of cell cycle progression at specific checkpoints provides the time necessary to prevent replication and segregation of damaged DNA and to process lesions (reviewed in references 52 and 57). A defective or incorrect activation of the surveillance and repair systems can lead to increased mutagenesis, genomic instability, and ultimately cancer (for a review, see reference 13).The Nijmegen breakage syndrome (NBS) and ataxia telangiectasia (AT) are rare human autosomal recessive diseases (22, 51) exhibiting hypersensitivity to ionizing radiation (IR), immunodeficiency, and increased predisposition to develop cancer. NBS patients, however, do not manifest the hallmarks of AT, i.e., cerebellar ataxia and oculocutaneous telangiectasia. At the cellular level, NBS and AT patients show chromosome instability, hypersensitivity to genotoxic agents, and cell cycle checkpoints defects (1,29,30). These similarities su...

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Section: Atm-dependent Chk2 Phosphorylation In Normal Cell Linesmentioning

confidence: 99%

Chk2 Activation Dependence on Nbs1 after DNA Damage

Buscemi

Savio

Zannini

et al. 2001

Molecular and Cellular Biology

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193

150

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“…The NBS1 gene was mapped to 8q21-24 by functional complementation assays using microcellmediated chromosome transfer (Komatsu et al, 1996;Matsuura et al, 1997). The gene was independently mapped to a 1.1-cM interval surrounding marker D8S1811 (Saar et al, 1997;Cerosaletty et al, 1998) and from this candidate region the NBS1 gene was identified (Matsuura et al, 1998a;Carney et al, 1998;Varon et al, 1998). A protein-truncating 5-bp NBS1 deletion, 657del5, has been found in most NBS families (more than 80%) with Slavic origins, demonstrating the presence of a common founder effect.…”

Section: Introductionmentioning

confidence: 99%

Nijmegen breakage syndrome gene, NBS1, and molecular links to factors for genome stability

et al. 2002

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DNA double-strand breaks represent the most potentially serious damage to a genome and hence, at least two pathways of DNA repair have evolved; namely, homologous recombination repair and non-homologous end joining. Defects in both rejoining processes result in genomic instability including chromosome rearrangements, LOH and gene mutations, which may lead to development of malignancies. Nijmegen breakage syndrome is a recessive genetic disorder, characterized by elevated sensitivity to ionizing radiation that induces double-strand breaks, and high frequency of malignancies. NBS1, the product of the gene underlying the disease, forms a multimeric complex with hMRE11/ hRAD50 nuclease and recruits them to the vicinity of sites of DNA damage by direct binding to phosphorylated histone H2AX. The combination of the highlyconserved NBS1 forkhead associated domain and BRCA1 C-terminus domain has a crucial role for recognition of damaged sites. Thereafter, the NBS1-complex proceeds to rejoin double-strand breaks predominantly by homologous recombination repair in vertebrates. This process collaborates with cell-cycle checkpoints at S and G2 phase to facilitate DNA repair. NBS1 is also associated with telomere maintenance and DNA replication. Based on recent knowledge regarding NBS1, we propose here a two-step binding mechanism for damage recognition by repair proteins, and describe the molecular links to factors for genome stability.

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“…The NBS1 gene is located on human chromosome 8q21 (6,20,22,26) and encodes a ubiquitously expressed protein of 754 amino acids (aa) termed nibrin or p95. All known NBS1 mutations are clustered between nucleotides 657 and 1142 of the gene, and all are predicted to truncate the nibrin protein.…”

mentioning

confidence: 99%

Distinct Functional Domains of Nibrin Mediate Mre11 Binding, Focus Formation, and Nuclear Localization

Desai-Mehta

Cerosaletti

Concannon

2001

Molecular and Cellular Biology

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The inherited chromosomal instability disorder Nijmegen breakage syndrome (NBS) results from truncating mutations in the NBS1 gene, which encodes the protein nibrin. Nibrin is part of a nuclear multiprotein complex that also contains the DNA repair proteins Mre11 and Rad50. Upon irradiation, this complex redistributes within the nucleus, forming distinct foci that have been implicated as sites of DNA repair. In NBS cells, nibrin is absent and Mre11 and Rad50 are cytoplasmic. In this study, the interacting domains on nibrin and Mre11 were mapped using the yeast two-hybrid system and expression of epitope-tagged constructs in NBS fibroblasts. Deletion of the carboxy-terminal 101 amino acids of nibrin eliminated its ability to interact with Mre11 and to complement the radiation sensitivity of NBS cells. However, this truncated form of nibrin could localize to the nucleus and form radiation-inducible foci. Expression of a carboxy-terminal 354-amino-acid fragment of nibrin was sufficient to direct the nuclear localization of nibrin, as well as that of Mre11 and Rad50. Despite providing some partial complementation of the radiation-sensitive phenotype, the nibrin-Mre11-Rad50 complexes in these cells were unable to form foci. These results indicate that nibrin directs not only the nuclear localization of the nibrin-Mre11-Rad50 complexes but also radiation-induced focus formation. However, direct interaction between nibrin and Mre11 is required for normal cellular survival postirradiation. Distinct domains of nibrin are required for each of these functions, focus formation, nuclear localization, and Mre11 interaction.The autosomal recessive disorder Nijmegen breakage syndrome (NBS) is characterized by microcephaly, growth retardation, borderline mental retardation, humoral and cellular immunodeficiency, chromosomal instability, radiation sensitivity, and an increased incidence of malignancies, particularly those of lymphoid origin (25). NBS cells cultured in vitro are deficient in the response to treatment with DNA double-strand break (DSB)-inducing agents such as ionizing radiation and radiomimetic compounds. These defective responses include reduction in colony-forming ability postirradiation, a failure to inhibit DNA synthesis in response to acute doses of radiation (radioresistant DNA synthesis), and an increased frequency of chromosomal aberrations (14,24). Positional cloning studies in NBS families and functional complementation studies identified a single gene, NBS1, that is mutated in most patients with NBS (19,26).The NBS1 gene is located on human chromosome 8q21 (6, 20, 22, 26) and encodes a ubiquitously expressed protein of 754 amino acids (aa) termed nibrin or p95. All known NBS1 mutations are clustered between nucleotides 657 and 1142 of the gene, and all are predicted to truncate the nibrin protein. Most (90 to 95%) of reported NBS patients are homozygous for one mutation (657del5); no other mutation has been observed in more than one family. Nibrin is not detectable by Western blotting in NBS cell lines, ...

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Fine Localization of the Nijmegen Breakage Syndrome Gene to 8q21: Evidence for a Common Founder Haplotype

Cited by 47 publications

References 18 publications

Chk2 Activation Dependence on Nbs1 after DNA Damage

Chk2 Activation Dependence on Nbs1 after DNA Damage

Nijmegen breakage syndrome gene, NBS1, and molecular links to factors for genome stability

Distinct Functional Domains of Nibrin Mediate Mre11 Binding, Focus Formation, and Nuclear Localization

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