Characterization of the plant homolog of Nijmegen breakage syndrome 1: Involvement in DNA repair and recombination
ABSTRACT The Nbs1 gene is known to code for a protein involved in the hereditary cancer-prone disease, Nijmegen breakage syndrome. This gene is conserved in animals and fungi, but no plant homolog is known. The work reported here describes a homolog of Nbs1 isolated from higher plants. The Nbs1 proteins from both Arabidopsis thaliana and Oryza sativa are smaller in size than animal or yeast Nbs1, but both contain the conserved Nbs1 domains such as the FHA/BRCT domain, the Mre11-binding domain, and the Atm-interacting domain in orientations similar to what is seen in animal Nbs1. The OsNbs1 protein interacted not only with plant Mre11, but also with animal Mre11. In plants, OsNbs1 mRNA expression was found to be higher in the shoot apex and young flower, and AtNbs1 expression increased when plants were exposed to 100 Gy of X-rays. These results suggest that plant Nbs1 could participate in a Rad50/Mre11/Nbs1 complex, and could be essential for the regulation of DNA recombination and DNA damage responses.
- SourceAvailable from: Karel J Angelis
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- "Therefore, we treated plants with c-irradiation that induces oxidative stress causing DNA single and doublestrand breaks as well as damaged bases. We compared the transcriptional profiles of GMI1 and of two repair genes known to be induced by c-irradiation (Garcia et al., 2003; Akutsu et al., 2007 "
ABSTRACT: DNA double-strand breaks (DSBs) pose one of the most severe threats to genome integrity, potentially leading to cell death. After detection of a DSB, the DNA damage and repair response is initiated and the DSB is repaired by non-homologous end joining and/or homologous recombination. Many components of these processes are still unknown in Arabidopsis thaliana. In this work, we characterized γ-irradiation and mitomycin C induced 1 (GMI1), a member of the SMC-hinge domain-containing protein family. RT-PCR analysis and promoter-GUS fusion studies showed that γ-irradiation, the radio-mimetic drug bleocin, and the DNA cross-linking agent mitomycin C strongly enhance GMI1 expression particularly in meristematic tissues. The induction of GMI1 by γ-irradiation depends on the signalling kinase Ataxia telangiectasia-mutated (ATM) but not on ATM and Rad3-related (ATR). Epistasis analysis of single and double mutants demonstrated that ATM acts upstream of GMI1 while the atr gmi1-2 double mutant was more sensitive than the respective single mutants. Comet assay revealed a reduced rate of DNA double-strand break repair in gmi1 mutants during the early recovery phase after exposure to bleocin. Moreover, the rate of homologous recombination of a reporter construct was strongly reduced in gmi1 mutant plants upon exposure to bleocin or mitomycin C. GMI1 is the first member of its protein family known to be involved in DNA repair.The Plant Journal 04/2011; 67(3):420-33. DOI:10.1111/j.1365-313X.2011.04604.x · 6.82 Impact Factor
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- "Xrs2 ⁄ Nbs1, responsible for the localization and signal transduction activity of MRX ⁄ N, displays the greatest sequence divergence of all the complex members. Nevertheless , the Arabidopsis AtNBS1 protein shares several sequence motifs with orthologues in other species, including an N-terminal forkhead-associated (FHA) domain, a weak BRCA1 C-terminus (BRCT) domain, a consensus Ser-Gln ATM phosphorylation site and a C-terminal MRE11 interaction region containing a FKXFXK motif (Akutsu et al., 2007; Waterworth et al., 2007). Analysis of an Atnbs1-1 mutant revealed a role for AtNBS1 in DNA cross-link repair, but suggested that any meiotic role is non-essential, with the caveat that the Atnbs1-1 allele expresses a short 5¢ transcript comprising the FHA domain and half of the BRCT domain (Waterworth et al., 2007). "
ABSTRACT: Meiosis is a central feature of sexual reproduction. Studies in plants have made and continue to make an important contribution to fundamental research aimed at the understanding of this complex process. Moreover, homologous recombination during meiosis provides the basis for plant breeders to create new varieties of crops. The increasing global demand for food, combined with the challenges from climate change, will require sustained efforts in crop improvement. An understanding of the factors that control meiotic recombination has the potential to make an important contribution to this challenge by providing the breeder with the means to make fuller use of the genetic variability that is available within crop species. Cytogenetic studies in plants have provided considerable insights into chromosome organization and behaviour during meiosis. More recently, studies, predominantly in Arabidopsis thaliana, are providing important insights into the genes and proteins that are required for crossover formation during plant meiosis. As a result, substantial progress in the understanding of the molecular mechanisms that underpin meiosis in plants has begun to emerge. This article summarizes current progress in the understanding of meiotic recombination and its control in Arabidopsis. We also assess the relationship between meiotic recombination in Arabidopsis and other eukaryotes, highlighting areas of close similarity and apparent differences.New Phytologist 03/2011; 190(3):523-44. DOI:10.1111/j.1469-8137.2011.03665.x · 6.55 Impact Factor
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- "3K - like kinase activity for their reversal . Activation of ATM is normally associated with activation of the MRE11 / RAD50 / NBS1 ( M / R / N ) complex , in which NBS1 is required for the signal transduction activity of the complex ( D ' Amours and Jackson , 2002 ; Falck et al . , 2005 ) . The plant homolog of NBS1 has recently been identified ( Akutsu et al . , 2007 ) , and its biological significance , including a possible role in meiosis , has been investigated ( Waterworth et al . , 2007 ) . Waterworth et al . established that the Arabidopsis NBS1 homolog is essential for cross - link repair ( demon - strating its functionality ) , but is not required for meiosis . Interestingly , the atm nbs1 d"
ABSTRACT: The ATM and ATR protein kinases play central roles in the cellular response to double-strand breaks (DSBs) by regulating DNA repair, cell-cycle arrest and apoptosis. During meiosis, SPO11-dependent DSBs are generated, initiating recombination between homologous chromosomes. Previous studies in mice and plants have shown that defects in ATM result in the appearance of abnormally fragmented chromosomes. However, the role of ATR in promoting normal meiosis has not yet been elucidated. Employing null Arabidopsis mutants of ATR and ATM, we demonstrate here that although atr mutants display no obvious defects in any phase of meiotic progression, the combination of defects in atr and atm exacerbates the fragmentation observed in the atm single mutant, prevents complete synapsis of chromosomes, and results in extensive and persistent interactions between non-homologous DNAs. The observed non-homologous interactions require the induction of programmed breaks: the combination of either the atm single or the atr atm double mutant with a spo11 defect eliminates the ectopic interactions observed in the double mutant, as well as significantly reducing the fragmentation seen in atm or in atr atm. Our results suggest that ATM is required for the efficient processing of SPO11-dependent DSBs during meiosis. They also indicate that ATM and ATR act redundantly to inhibit sustained interactions between non-homologous chromatids, and that these ectopic interactions require SPO11 activity.The Plant Journal 07/2008; 55(4):629-38. DOI:10.1111/j.1365-313X.2008.03530.x · 6.82 Impact Factor