ORCID Profile
0000-0001-5588-9116
Current Organisation
Université Clermont Auvergne
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Publisher: Wiley
Date: 09-09-2010
Publisher: Springer Science and Business Media LLC
Date: 06-11-2015
DOI: 10.1038/SREP16255
Abstract: Telomeres are nucleoprotein structures at the end of chromosomes which stabilize and protect them from nucleotidic degradation and end-to-end fusions. The G-rich telomeric single-stranded DNA overhang can adopt a four-stranded G-quadruplex DNA structure (G4). Stabilization of the G4 structure by binding of small molecule ligands enhances radiosensitivity of tumor cells and this combined treatment represents a novel anticancer approach. We studied the effect of the platinum-derived G4-ligand, Pt-ctpy, in association with radiation on human glioblastoma (SF763 and SF767) and non-small cell lung cancer (A549 and H1299) cells in vitro and in vivo . Treatments with submicromolar concentrations of Pt-ctpy inhibited tumor proliferation in vitro with cell cycle alterations and induction of apoptosis. Non-toxic concentrations of the ligand were then combined with ionizing radiation. Pt-ctpy radiosensitized all cell lines with dose-enhancement factors between 1.32 and 1.77. The combined treatment led to increased DNA breaks. Furthermore, a significant radiosensitizing effect of Pt-ctpy in mice xenografted with glioblastoma SF763 cells was shown by delayed tumor growth and improved survival. Pt-ctpy can act in synergy with radiation for efficient killing of cancer cells at concentrations at which it has no obvious toxicity per se , opening perspectives for future therapeutic applications.
Publisher: Springer Science and Business Media LLC
Date: 29-08-2015
DOI: 10.1007/S11103-006-9061-7
Abstract: Telomeres, the nucleoprotein complexes at the ends of eukaryotic chromosomes, are maintained at a species-specific equilibrium length. Arabidopsis thaliana is a self-fertilizing plant and different geographical isolates or ecotypes show differing telomere-lengths. We have exploited this telomere-length polymorphism between Arabidopsis ecotypes to investigate the genetic regulation of telomere length by analysing telomere lengths in 16 different inter-ecotype crosses between plants with differing telomere sizes. With two exceptions, the inter-ecotype hybrid plants present a new telomere-length set point, intermediate between that of the two parents. A regulation mechanism thus shortens the longer and lengthens the shorter telomeres.
Publisher: Springer Science and Business Media LLC
Date: 1999
Abstract: We have analysed the application of positive-negative selection for the selection of homologous recombination interactions between the chromosome and a T-DNA molecule after transformation of plant cells. Two different genomic loci in a cell suspension of Arabidopsis thaliana were chosen to study gene targeting events. One was the chalcone synthase (CHS) gene present as a single copy and the second an hemizygous chromosomally inserted T-DNA containing the hpt gene, conferring resistance to hygromycin, flanked by CHS sequences. The target lines were transformed with replacement-type T-DNA vectors which contained a positive selectable marker flanked by the regions of the CHS gene and a negative selectable marker to counter-select random insertions. As negative marker we used the Escherichia coli codA gene encoding cytosine deaminase, conferring upon the cells sensitivity to 5-flourocytosine (5-FC). Doubly selected transformants represent 1-4% of the primary transformed cells. Targeting events were not found at the chalcone synthase locus nor at the artificial hpt locus in a total of 4379 doubly selected calli, corresponding to at least 109,475 in idual primary transformants. We show by PCR and Southern analysis that the 5-FC resistance in the majority of these cells is associated with substantial deletions of the T-DNA molecule from the right-border end.
Publisher: Public Library of Science (PLoS)
Date: 26-09-2013
Publisher: Springer Science and Business Media LLC
Date: 07-2005
DOI: 10.1007/S10577-005-0995-4
Abstract: In this review, we discuss recent advances in the knowledge of plant telomere maintenance, focusing on the model plant Arabidopsis thaliana and, in particular, on the roles of proteins involved in DNA repair and recombination. The question of the interrelationships between DNA repair and recombination pathways and proteins with telomere function and maintenance is of increasing interest and has been the subject of a number of recent reviews (Cech 2004, d'Adda di Fagagna et al. 2004, Hande 2004, Harrington 2004, Maser and DePinho 2004). Understanding of telomere biology, DNA repair and recombination in plants has rapidly progressed over the last decade, substantially due to genetic approaches in Arabidopsis, and we feel that this is an appropriate time to review current knowledge in this field. A number of recent reviews have dealt more generally with the subject of plant telomere structure and evolution (Riha et al. 2001, McKnight et al. 2002, Riha and Shippen 2003b, McKnight and Shippen 2004, Fajkus et al. 2005) and we thus focus specifically on plant telomere biology in the context of DNA repair and recombination in Arabidopsis.
Publisher: Cold Spring Harbor Laboratory
Date: 09-0009
DOI: 10.1101/2020.06.09.142000
Abstract: An essential component of the homologous recombination machinery in eukaryotes, the RAD54 protein is a member of the SWI2/SNF2 family of helicases with dsDNA-dependent ATPase, DNA translocase, DNA supercoiling and chromatin remodelling activities. It is a motor protein that translocates along dsDNA and performs multiple functions in homologous recombination. In particular, RAD54 is an essential cofactor for regulating RAD51 activity. It stabilizes the RAD51 nucleofilament, remodels nucleosomes, and stimulates homology search and strand invasion activity of RAD51. Accordingly, deletion of RAD54 has dramatic consequences on DNA damage repair in mitotic cells. In contrast, its role in meiotic recombination is less clear. RAD54 is essential for meiotic recombination in Drosophila and C. elegans , but plays minor roles in yeast and mammals. We present here characterization of the roles of RAD54 in meiotic recombination in the model plant Arabidopsis thaliana . Absence of RAD54 has no detectable effect on meiotic recombination in otherwise wild-type plants but RAD54 becomes essential for meiotic DSB repair in absence of DMC1. In Arabidopsis, dmc1 mutants have an achiasmate meiosis, in which RAD51 repairs meiotic DSBs. Absence of RAD54 in dmc1 mutants leads to meiotic chromosomal fragmentation. The action of RAD54 in meiotic RAD51 activity is thus downstream of the role of RAD51 in supporting the activity of DMC1. Equivalent analyses show no effect on meiosis of combining dmc1 with the mutants of the RAD51-mediators RAD51B, RAD51D and XRCC2. RAD54 is thus required for repair of meiotic DSBs by RAD51 and the absence of meiotic phenotype in rad54 plants is a consequence of RAD51 playing a RAD54-independent supporting role to DMC1 in meiotic recombination. Homologous recombination is a universal pathway which repairs broken DNA molecules through the use of homologous DNA templates. It is both essential for maintenance of genome stability and for the generation of genetic ersity through sexual reproduction. A central step of the homologous recombination process is the search for and invasion of a homologous intact DNA sequence that will be used as template. This key step is catalysed by the RAD51 recombinase in somatic cells and RAD51 and DMC1 in meiotic cells, assisted by a number of associated factors. Among these, the chromatin-remodelling protein RAD54 is a required cofactor for RAD51 in mitotic cells. Understanding of its role during meiotic recombination however remains elusive. We show here that RAD54 is required for repair of meiotic double strand breaks by RAD51 in the plant Arabidopsis thaliana , and this function is downstream of the meiotic role of RAD51 in supporting the activity of DMC1. These results provide new insights into the regulation of the central step of homologous recombination in plants and very probably also other multicellular eukaryotes.
Publisher: Public Library of Science (PLoS)
Date: 18-05-2021
DOI: 10.1371/JOURNAL.PGEN.1008919
Abstract: An essential component of the homologous recombination machinery in eukaryotes, the RAD54 protein is a member of the SWI2/SNF2 family of helicases with dsDNA-dependent ATPase, DNA translocase, DNA supercoiling and chromatin remodelling activities. It is a motor protein that translocates along dsDNA and performs multiple functions in homologous recombination. In particular, RAD54 is an essential cofactor for regulating RAD51 activity. It stabilizes the RAD51 nucleofilament, remodels nucleosomes, and stimulates homology search and strand invasion activity of RAD51. Accordingly, deletion of RAD54 has dramatic consequences on DNA damage repair in mitotic cells. In contrast, its role in meiotic recombination is less clear. RAD54 is essential for meiotic recombination in Drosophila and C . elegans , but plays minor roles in yeast and mammals. We present here characterization of the roles of RAD54 in meiotic recombination in the model plant Arabidopsis thaliana . Absence of RAD54 has no detectable effect on meiotic recombination in otherwise wild-type plants but RAD54 becomes essential for meiotic DSB repair in absence of DMC1. In Arabidopsis, dmc1 mutants have an achiasmate meiosis, in which RAD51 repairs meiotic DSBs. Lack of RAD54 leads to meiotic chromosomal fragmentation in absence of DMC1. The action of RAD54 in meiotic RAD51 activity is thus mainly downstream of the role of RAD51 in supporting the activity of DMC1. Equivalent analyses show no effect on meiosis of combining dmc1 with the mutants of the RAD51-mediators RAD51B, RAD51D and XRCC2. RAD54 is thus required for repair of meiotic DSBs by RAD51 and the absence of meiotic phenotype in rad54 plants is a consequence of RAD51 playing a RAD54-independent supporting role to DMC1 in meiotic recombination.
Publisher: Wiley
Date: 25-03-2017
DOI: 10.1111/TPJ.13499
Abstract: Plants have various defense mechanisms against environmental stresses that induce DNA damage. Genetic and biochemical analyses have revealed the sensing and signaling of DNA damage, but little is known about subnuclear dynamics in response to DNA damage in living plant cells. Here, we observed that the chromatin remodeling factor RAD54, which is involved in DNA repair via the homologous recombination pathway, formed subnuclear foci (termed RAD54 foci) in Arabidopsis thaliana after induction of DNA double-strand breaks. The appearance of RAD54 foci was dependent on the ATAXIA-TELANGIECTASIA MUTATED-SUPPRESSOR OF GAMMA RESPONSE 1 pathway, and RAD54 foci were co-localized with γH2AX signals. Laser irradiation of a subnuclear area demonstrated that in living cells RAD54 was specifically accumulated at the damaged site. In addition, the formation of RAD54 foci showed specificity for cell type and region. We conclude that RAD54 foci correspond to DNA repair foci in A. thaliana.
Publisher: Springer Science and Business Media LLC
Date: 10-08-2004
DOI: 10.1007/S00412-004-0309-1
Abstract: The Rad50, Mre11 and Xrs2/Nbs1 proteins, which form the highly conserved MRX complex, perform a wide range of functions concerning the maintenance and function of DNA in eukaryotes. These include recombination, DNA repair, replication, telomere homeostasis and meiosis. Notwithstanding the attention paid to this complex, the inviability of vertebrate rad50 and mre11 mutants has led to a relative lack of information concerning the role of these proteins in meiosis in higher eukaryotes. We have previously reported that Arabidopsis atrad50 mutant plants are viable and that atrad50 mutant plants are sterile. The present study reports an analysis of the causes of this sterility and the implication of the AtRad50 protein in meiosis. Both male and female gametogenesis are defective in the Arabidopsis atrad50 mutant and cytological observation of male meiosis indicates that in the absence of the AtRad50 protein, homologous chromosomes are unable to synapse. Finally, the atrad50 mutation leads to the destruction of chromosomes during meiosis. These phenotypes support a role for the Arabidopsis MRX complex in early stages of meiotic recombination.
Publisher: Public Library of Science (PLoS)
Date: 21-01-2014
Publisher: Oxford University Press (OUP)
Date: 21-02-2003
DOI: 10.1105/TPC.008623
Abstract: We have identified a ku80 mutant of Arabidopsis and show that telomerase is needed to generate the longer telomeres observed in this mutant. Telomeres are specialized nucleoprotein structures at the ends of chromosomes that permit cells to distinguish chromosome ends from double-strand breaks, thus preventing chromosome fusion events. Ku80 deficiency results in the lengthening of telomeres, a phenotype also seen in an Arabidopsis ku70 mutant. Furthermore, homogeneous populations of ku80 mutant cells show a steady increase in the length of telomere tracts, which reach an equilibrium length and then stabilize. In contrast to that in mammals, Ku80 deficiency in Arabidopsis cells does not cause end-to-end fusion of chromosomes. This telomere lengthening is dependent on the presence of telomerase, although it is not attributable to a significant increase in telomerase activity per se. These results demonstrate the essential role of the Ku80 protein as a negative regulator of telomerase function in plant cells.
Publisher: Public Library of Science (PLoS)
Date: 21-11-2013
Publisher: Wiley
Date: 16-04-2013
DOI: 10.1111/TPJ.12182
Abstract: Homologous recombination is key to the maintenance of genome integrity and the creation of genetic ersity. At the mechanistic level, recombination involves the invasion of a homologous DNA template by broken DNA ends, repair of the break and exchange of genetic information between the two DNA molecules. Invasion of the template in eukaryotic cells is catalysed by the RAD51 and DMC1 recombinases, assisted by a number of accessory proteins, including the RAD51 paralogues. Eukaryotic genomes encode a variable number of RAD51 paralogues, ranging from two in yeast to five in animals and plants. The RAD51 paralogues form at least two distinct protein complexes, believed to play roles in the assembly and stabilization of the RAD51-DNA nucleofilament. Somatic recombination assays and immunocytology confirm that the three 'non-meiotic' paralogues of Arabidopsis, RAD51B, RAD51D and XRCC2, are involved in somatic homologous recombination, and that they are not required for the formation of radioinduced RAD51 foci. Given the presence of all five proteins in meiotic cells, the apparent absence of a meiotic role for RAD51B, RAD51D and XRCC2 is surprising, and perhaps simply the result of a more subtle meiotic phenotype in the mutants. Analysis of meiotic recombination confirms this, showing that the absence of XRCC2, and to a lesser extent RAD51B, but not RAD51D, increases rates of meiotic crossing over. The roles of RAD51B and XRCC2 in recombination are thus not limited to mitotic cells.
Publisher: Oxford University Press (OUP)
Date: 09-2010
Publisher: Wiley
Date: 13-03-2002
DOI: 10.1016/S0014-5793(02)02536-X
Abstract: The Rad50-Mre11-Xrs2/Nbs1 protein complex plays critical roles in cellular processes involving DNA ends. This complex is implicated in DNA recombination and replication, meiosis, telomere maintenance and cellular DNA damage responses. The Rad50 and Mre11 proteins are essential for viability in animals, although not in yeast. We have prepared antibodies to the Rad50 protein of the model plant Arabidopsis thaliana which recognize a 175 kDa protein in wild-type Arabidopsis protein extracts. Furthermore, we report here demonstration of the existence of the Rad50-Mre11 complex by co-immunoprecipitation of the Rad50 and Mre11 proteins from the plant cell extracts.
Publisher: Oxford University Press (OUP)
Date: 24-12-2018
DOI: 10.1105/TPC.15.00898
Publisher: Elsevier BV
Date: 12-2020
Publisher: Public Library of Science (PLoS)
Date: 13-02-2009
Publisher: Wiley
Date: 22-12-2004
Publisher: Oxford University Press (OUP)
Date: 13-01-2018
DOI: 10.1093/NAR/GKX1322
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.DNAREP.2011.04.002
Abstract: Double-strand breaks in genomic DNA (DSB) are potentially lethal lesions which separate parts of chromosome arms from their centromeres. Repair of DSB by recombination can generate mutations and further chromosomal rearrangements, making the regulation of recombination and the choice of recombination pathways of the highest importance. Although knowledge of recombination mechanisms has considerably advanced, the complex interrelationships and regulation of pathways are far from being fully understood. We analyse the different pathways of DSB repair acting in G2/M phase nuclei of irradiated plants, through quantitation of the kinetics of appearance and loss of γ-H2AX foci in Arabidopsis mutants. These analyses show the roles for the four major recombination pathways in post-S-phase DSB repair and that non-homologous recombination pathways constitute the major response. The data suggest a hierarchical organisation of DSB repair in these cells: C-NHEJ acts prior to B-NHEJ which can also inhibit MMEJ. Surprisingly the quadruple ku80 xrcc1 xrcc2 xpf mutant can repair DSB, although with severely altered kinetics. This repair leads to massive genetic instability with more than 50% of mitoses showing anaphase bridges following irradiation. This study thus clarifies the relationships between the different pathways of DSB repair in the living plant and points to the existence of novel DSB repair processes.
Publisher: Wiley
Date: 03-12-2014
DOI: 10.1111/TPJ.12718
Publisher: EMBO
Date: 11-2002
Publisher: EMBO
Date: 04-2001
Publisher: Oxford University Press (OUP)
Date: 12-2011
Abstract: The ends of linear eukaryotic chromosomes are hidden in nucleoprotein structures called telomeres, and loss of the telomere structure causes inappropriate repair, leading to severe karyotypic and genomic instability. Although it has been shown that DNA damaging agents activate a DNA damage response (DDR), little is known about the signaling of dysfunctional plant telomeres. We show that absence of telomerase in Arabidopsis thaliana elicits an ATAXIA-TELANGIECTASIA MUTATED (ATM) and ATM AND RAD3-RELATED (ATR)-dependent DDR at telomeres, principally through ATM. By contrast, telomere dysfunction induces an ATR-dependent response in telomeric Conserved telomere maintenance component1 (Ctc1)-Suppressor of cdc thirteen (Stn1)-Telomeric pathways in association with Stn1 (CST)–complex mutants. These results uncover a new role for the CST complex in repressing the ATR-dependent DDR pathway in plant cells and show that plant cells use two different DNA damage surveillance pathways to signal telomere dysfunction. The absence of either ATM or ATR in ctc1 and stn1 mutants significantly enhances developmental and genome instability while reducing stem cell death. These data thus give a clear illustration of the action of ATM/ATR-dependent programmed cell death in maintaining genomic integrity through elimination of genetically unstable cells.
Publisher: Springer Science and Business Media LLC
Date: 09-2004
DOI: 10.1007/S11103-004-2812-4
Abstract: Homologous recombination events occurring during meiotic prophase I ensure the proper segregation of homologous chromosomes at the first meiotic ision. These events are initiated by programmed double-strand breaks produced by the Spo11 protein and repair of such breaks by homologous recombination requires a strand exchange activity provided by the Rad51 protein. We have recently reported that the absence of AtXrcc3, an Arabidopsis Rad51 paralogue, leads to extensive chromosome fragmentation during meiosis, first visible in diplotene of meiotic prophase I. The present study clearly shows that this fragmentation results from un- or mis-repaired AtSpo11-1 induced double-strand breaks and is thus due to a specific defect in the meiotic recombination process.
Publisher: Elsevier BV
Date: 03-2014
DOI: 10.1093/MP/SST172
Abstract: Meiosis is the specialized eukaryotic cell ision that permits the halving of ploidy necessary for gametogenesis in sexually reproducing organisms. This involves a single round of DNA replication followed by two successive isions. To ensure balanced segregation, homologous chromosome pairs must migrate to opposite poles at the first meiotic ision and this means that they must recognize and pair with each other beforehand. Although understanding of the mechanisms by which meiotic chromosomes find and pair with their homologs has greatly advanced, it remains far from being fully understood. With some notable exceptions such as male Drosophila, the recognition and physical linkage of homologs at the first meiotic ision involves homologous recombination. However, in addition to this, it is clear that many organisms, including plants, have also evolved a series of recombination-independent mechanisms to facilitate homolog recognition and pairing. These implicate chromosome structure and dynamics, telomeres, centromeres, and, most recently, small RNAs. With a particular focus on plants, we present here an overview of understanding of these early, recombination-independent events that act in the pairing of homologous chromosomes during the first meiotic ision.
Publisher: Public Library of Science (PLoS)
Date: 10-08-2017
Publisher: Oxford University Press (OUP)
Date: 10-2014
DOI: 10.1093/NAR/GKU897
Publisher: Frontiers Media SA
Date: 2013
Publisher: Wiley
Date: 17-01-2014
DOI: 10.1111/TPJ.12398
Abstract: Using floral-dip, tumorigenesis and root callus transformation assays of both germline and somatic cells, we present here results implicating the four major non-homologous and homologous recombination pathways in Agrobacterium-mediated transformation of Arabidopsis thaliana. All four single mutant lines showed similar mild reductions in transformability, but knocking out three of four pathways severely compromised Agrobacterium-mediated transformation. Although integration of T-DNA into the plant genome is severely compromised in the absence of known DNA double-strand break repair pathways, it does still occur, suggesting the existence of other pathways involved in T-DNA integration. Our results highlight the functional redundancy of the four major plant recombination pathways in transformation, and provide an explanation for the lack of strong effects observed in previous studies on the roles of plant recombination functions in transformation.
Publisher: Wiley
Date: 29-07-2003
DOI: 10.1046/J.1365-313X.2003.01827.X
Abstract: Chromosomal breaks are repaired by homologous recombination (HR) or non-homologous end joining (NHEJ) mechanisms. The Ku70/Ku80 heterodimer binds DNA ends and plays roles in NHEJ and telomere maintenance in organisms ranging from yeast to humans. We have previously identified a ku80 mutant of the model plant Arabidopsis thaliana and shown the role of Ku80 in telomere homeostasis in plant cells. We show here that this mutant is hypersensitive to the DNA-damaging agent methyl methane sulphonate and has a reduced capacity to carry out NHEJ recombination. To understand the interplay between HR and NHEJ in plants, we measured HR in the absence of Ku80. We find that the frequency of intrachromosomal HR is not affected by the absence of Ku80. Previous work has clearly implicated the Ku heterodimer in Agrobacterium-mediated T-DNA transformation of yeast. Surprisingly, ku80 mutant plants show no defect in the efficiency of T-DNA transformation of plants with Agrobacterium, showing that an alternative pathway must exist in plants.
Publisher: Wiley
Date: 24-10-2012
DOI: 10.1111/PBI.12014
Abstract: Low transformation efficiency and high background of non-targeted events are major constraints to gene targeting in plants. We demonstrate here applicability in maize of a system that reduces the constraint from transformation efficiency. The system requires regenerable transformants in which all of the following elements are stably integrated in the genome: (i) donor DNA with the gene of interest adjacent to sequence for repair of a defective selectable marker, (ii) sequence encoding a rare-cutting endonuclease such as I-SceI, (iii) a target locus (TL) comprising the defective selectable marker and I-SceI cleavage site. Typically, this requires additional markers for the integration of the donor and target sequences, which may be assembled through cross-pollination of separate transformants. Inducible expression of I-SceI then cleaves the TL and facilitates homologous recombination, which is assayed by selection for the repaired marker. We used bar and gfp markers to identify assembled transformants, a dexamethasone-inducible I-SceI::GR protein, and selection for recombination events that restored an intact nptII. Applying this strategy to callus permitted the selection of recombination into the TL at a frequency of 0.085% per extracted immature embryo (29% of recombinants). Our results also indicate that excision of the donor locus (DL) through the use of flanking I-SceI cleavage sites may be unnecessary, and a source of unwanted repair events at the DL. The system allows production, from each assembled transformant, of many cells that subsequently can be treated to induce gene targeting. This may facilitate gene targeting in plant species for which transformation efficiencies are otherwise limiting.
Publisher: Wiley
Date: 21-09-2006
Publisher: Elsevier BV
Date: 2006
DOI: 10.1016/J.DNAREP.2005.08.017
Abstract: Living cells suffer numerous and varied alterations of their genetic material. Of these, the DNA double-strand break (DSB) is both particularly threatening and common. Double-strand breaks arise from exposure to DNA damaging agents, but also from cell metabolism-in a fortuitous manner during DNA replication or repair of other kinds of lesions and in a programmed manner, for ex le during meiosis or V(D)J gene rearrangement. Cells possess several overlapping repair pathways to deal with these breaks, generally designated as genetic recombination. Genetic and biochemical studies have provided considerable amounts of data about the proteins involved in recombination processes and their functions within these processes. Although they have long played a key role in building understanding of genetics, relatively little is known at the molecular level of the genetic recombination processes in plants. The use of reverse genetic approaches and the public availability of sequence tagged mutants in Arabidopsis thaliana have led to increasingly rapid progress in this field over recent years. The rapid progress of studies of recombination in plants is obviously not limited to the DSB repair machinery as such and we ask readers to understand that in order to maintain the focus and to rest within a reasonable length, we present only limited discussion of the exciting advances in the of plant meiosis field, which require a full review in their own right . We thus present here an update on recent advances in understanding of the DSB repair machinery of plants, focussing on Arabidopsis and making a particular effort to place these in the context of more general of understanding of these processes.
Publisher: Oxford University Press (OUP)
Date: 31-07-2019
DOI: 10.1104/PP.19.00530
Publisher: Proceedings of the National Academy of Sciences
Date: 13-02-2001
Abstract: We have identified and characterized an Arabidopsis thaliana rad50 mutant plant containing a T-DNA insertion in the AtRAD50 gene and showing both meiotic and DNA repair defects. We report here that rad50/rad50 mutant cells show a progressive shortening of telomeric DNA relative to heterozygous rad50/RAD50 controls and that the mutant cell population rapidly enters a crisis, with the majority of the cells dying. Surviving rad50 mutant cells have longer telomeres than wild-type cells, indicating the existence in plants of an alternative RAD50 -independent mechanism for telomere maintenance. These results report the role of a protein essential for double-strand break repair in telomere maintenance in higher eukaryotes.
Publisher: Wiley
Date: 2001
DOI: 10.1046/J.1365-313X.2001.00928.X
Abstract: The Rad50 protein is involved in the cellular response to DNA-double strand breaks (DSBs), including the detection of damage, activation of cell-cycle checkpoints, and DSB repair via recombination. It is essential for meiosis in yeast, is involved in telomere maintenance, and is essential for cellular viability in mice. Here we present the isolation, sequence and characterization of the Arabidopsis thaliana RAD50 homologue (AtRAD50) and an Arabidopsis mutant of this gene. A single copy of this gene is present in the Arabidopsis genome, located on chromosome II. Northern analysis shows a single 4.3 Kb mRNA species in all plant tissues tested, which is strongly enriched in flowers and other tissues with many iding cells. The predicted protein presents strong conservation with the other known Rad50 homologues of the amino- and carboxy-terminal regions. Mutant plants present a sterility phenotype which co-segregates with the T-DNA insertion. Molecular analysis of the mutant plants shows that the sterility phenotype is present only in the plants homozygous for the T-DNA insertion. An in vitro mutant cell line, derived from the mutant plant, shows a clear hypersensitivity to the DNA-damaging agent methylmethane sulphonate, suggesting a role of RAD50 in double-strand break repair in plant cells. This is the first report of a plant mutated in a protein of the Rad50-Mre11-Xrs2 complex, as well as the first data suggesting the involvement of the Rad50 homologue protein in meiosis and DNA repair in plants.
Publisher: Wiley
Date: 15-06-2004
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Maria Eugenia Gallego.