Publications by authors named "Marta Barrientos-Moreno"

5 Publications

  • Page 1 of 1

Chromatin modifiers and recombination factors promote a telomere fold-back structure, that is lost during replicative senescence.

PLoS Genet 2020 12 28;16(12):e1008603. Epub 2020 Dec 28.

Institute of Developmental Biology and Neurobiology (IDN), Johannes Gutenberg-Universität, Mainz, Germany.

Telomeres have the ability to adopt a lariat conformation and hence, engage in long and short distance intra-chromosome interactions. Budding yeast telomeres were proposed to fold back into subtelomeric regions, but a robust assay to quantitatively characterize this structure has been lacking. Therefore, it is not well understood how the interactions between telomeres and non-telomeric regions are established and regulated. We employ a telomere chromosome conformation capture (Telo-3C) approach to directly analyze telomere folding and its maintenance in S. cerevisiae. We identify the histone modifiers Sir2, Sin3 and Set2 as critical regulators for telomere folding, which suggests that a distinct telomeric chromatin environment is a major requirement for the folding of yeast telomeres. We demonstrate that telomeres are not folded when cells enter replicative senescence, which occurs independently of short telomere length. Indeed, Sir2, Sin3 and Set2 protein levels are decreased during senescence and their absence may thereby prevent telomere folding. Additionally, we show that the homologous recombination machinery, including the Rad51 and Rad52 proteins, as well as the checkpoint component Rad53 are essential for establishing the telomere fold-back structure. This study outlines a method to interrogate telomere-subtelomere interactions at a single unmodified yeast telomere. Using this method, we provide insights into how the spatial arrangement of the chromosome end structure is established and demonstrate that telomere folding is compromised throughout replicative senescence.
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http://dx.doi.org/10.1371/journal.pgen.1008603DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7793543PMC
December 2020

Non-recombinogenic roles for Rad52 in translesion synthesis during DNA damage tolerance.

EMBO Rep 2021 01 2;22(1):e50410. Epub 2020 Dec 2.

Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), CSIC-University of Seville-University Pablo de Olavide, Seville, Spain.

DNA damage tolerance relies on homologous recombination (HR) and translesion synthesis (TLS) mechanisms to fill in the ssDNA gaps generated during passing of the replication fork over DNA lesions in the template. Whereas TLS requires specialized polymerases able to incorporate a dNTP opposite the lesion and is error-prone, HR uses the sister chromatid and is mostly error-free. We report that the HR protein Rad52-but not Rad51 and Rad57-acts in concert with the TLS machinery (Rad6/Rad18-mediated PCNA ubiquitylation and polymerases Rev1/Pol ζ) to repair MMS and UV light-induced ssDNA gaps through a non-recombinogenic mechanism, as inferred from the different phenotypes displayed in the absence of Rad52 and Rad54 (essential for MMS- and UV-induced HR); accordingly, Rad52 is required for efficient DNA damage-induced mutagenesis. In addition, Rad52, Rad51, and Rad57, but not Rad54, facilitate Rad6/Rad18 binding to chromatin and subsequent DNA damage-induced PCNA ubiquitylation. Therefore, Rad52 facilitates the tolerance process not only by HR but also by TLS through Rad51/Rad57-dependent and -independent processes, providing a novel role for the recombination proteins in maintaining genome integrity.
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http://dx.doi.org/10.15252/embr.202050410DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7788459PMC
January 2021

Actin and Nuclear Envelope Components Influence Ectopic Recombination in the Absence of Swr1.

Genetics 2019 11 18;213(3):819-834. Epub 2019 Sep 18.

Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Consejo Superior de Investigaciones Científicas-University of Seville-University Pablo de Olavide, Spain

The accuracy of most DNA processes depends on chromatin integrity and dynamics. Our analyses in the yeast show that an absence of Swr1 (the catalytic and scaffold subunit of the chromatin-remodeling complex SWR) leads to the formation of long-duration Rad52, but not RPA, foci and to an increase in intramolecular recombination. These phenotypes are further increased by MMS, zeocin, and ionizing radiation, but not by double-strand breaks, HU, or transcription/replication collisions, suggesting that they are associated with specific DNA lesions. Importantly, these phenotypes can be specifically suppressed by mutations in: (1) chromatin-anchorage internal nuclear membrane components (∆ and ∆); (2) actin and actin regulators ( , , ∆, and ); or (3) the SWR subunit Swc5 and the SWR substrate Htz1 However, they are not suppressed by global disruption of actin filaments or by the absence of Csm4 (a component of the external nuclear membrane that forms a bridging complex with Mps3, thus connecting the actin cytoskeleton with chromatin). Moreover, ∆-induced Rad52 foci and intramolecular recombination are not associated with tethering recombinogenic DNA lesions to the nuclear periphery. In conclusion, the absence of Swr1 impairs efficient recombinational repair of specific DNA lesions by mechanisms that are influenced by SWR subunits, including actin, and nuclear envelope components. We suggest that these recombinational phenotypes might be associated with a pathological effect on homologous recombination of actin-containing complexes.
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http://dx.doi.org/10.1534/genetics.119.302580DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6827384PMC
November 2019

Crosstalk between chromatin structure, cohesin activity and transcription.

Epigenetics Chromatin 2019 07 22;12(1):47. Epub 2019 Jul 22.

Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine (CABIMER), CSIC-University of Seville-University Pablo de Olavide, Seville, Spain.

Background: A complex interplay between chromatin and topological machineries is critical for genome architecture and function. However, little is known about these reciprocal interactions, even for cohesin, despite its multiple roles in DNA metabolism.

Results: We have used genome-wide analyses to address how cohesins and chromatin structure impact each other in yeast. Cohesin inactivation in scc1-73 mutants during the S and G2 phases causes specific changes in chromatin structure that preferentially take place at promoters; these changes include a significant increase in the occupancy of the - 1 and + 1 nucleosomes. In addition, cohesins play a major role in transcription regulation that is associated with specific promoter chromatin architecture. In scc1-73 cells, downregulated genes are enriched in promoters with short or no nucleosome-free region (NFR) and a fragile "nucleosome - 1/RSC complex" particle. These results, together with a preferential increase in the occupancy of nucleosome - 1 of these genes, suggest that cohesins promote transcription activation by helping RSC to form the NFR. In sharp contrast, the scc1-73 upregulated genes are enriched in promoters with an "open" chromatin structure and are mostly at cohesin-enriched regions, suggesting that a local accumulation of cohesins might help to inhibit transcription. On the other hand, a dramatic loss of chromatin integrity by histone depletion during DNA replication has a moderate effect on the accumulation and distribution of cohesin peaks along the genome.

Conclusions: Our analyses of the interplay between chromatin integrity and cohesin activity suggest that cohesins play a major role in transcription regulation, which is associated with specific chromatin architecture and cohesin-mediated nucleosome alterations of the regulated promoters. In contrast, chromatin integrity plays only a minor role in the binding and distribution of cohesins.
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http://dx.doi.org/10.1186/s13072-019-0293-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6647288PMC
July 2019

Histone depletion prevents telomere fusions in pre-senescent cells.

PLoS Genet 2018 06 7;14(6):e1007407. Epub 2018 Jun 7.

Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), CSIC-University of Seville-University Pablo de Olavide, Seville, Spain.

Upon telomerase inactivation, telomeres gradually shorten with each cell division until cells enter replicative senescence. In Saccharomyces cerevisiae, the kinases Mec1/ATR and Tel1/ATM protect the genome during pre-senescence by preventing telomere-telomere fusions (T-TFs) and the subsequent genetic instability associated with fusion-bridge-breakage cycles. Here we report that T-TFs in mec1Δ tel1Δ cells can be suppressed by reducing the pool of available histones. This protection associates neither with changes in bulk telomere length nor with major changes in the structure of subtelomeric chromatin. We show that the absence of Mec1 and Tel1 strongly augments double-strand break (DSB) repair by non-homologous end joining (NHEJ), which might contribute to the high frequency of T-TFs in mec1Δ tel1Δ cells. However, histone depletion does not prevent telomere fusions by inhibiting NHEJ, which is actually increased in histone-depleted cells. Rather, histone depletion protects telomeres from fusions by homologous recombination (HR), even though HR is proficient in maintaining the proliferative state of pre-senescent mec1Δ tel1Δ cells. Therefore, HR during pre-senescence not only helps stalled replication forks but also prevents T-TFs by a mechanism that, in contrast to the previous one, is promoted by a reduction in the histone pool and can occur in the absence of Rad51. Our results further suggest that the Mec1-dependent depletion of histones that occurs during pre-senescence in cells without telomerase (tlc1Δ) prevents T-TFs by favoring the processing of unprotected telomeres by Rad51-independent HR.
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http://dx.doi.org/10.1371/journal.pgen.1007407DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5991667PMC
June 2018
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