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Alanazi AFR, Parkinson GN, Haider S. Structural Motifs at the Telomeres and Their Role in Regulatory Pathways. Biochemistry 2024; 63:827-842. [PMID: 38481135 PMCID: PMC10993422 DOI: 10.1021/acs.biochem.4c00023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Telomeres are specialized structures, found at the ends of linear chromosomes in eukaryotic cells, that play a crucial role in maintaining the stability and integrity of genomes. They are composed of repetitive DNA sequences, ssDNA overhangs, and several associated proteins. The length of telomeres is linked to cellular aging in humans, and deficiencies in their maintenance are associated with various diseases. Key structural motifs at the telomeres serve to protect vulnerable chromosomal ends. Telomeric DNA also has the ability to form diverse complex DNA higher-order structures, including T-loops, D-loops, R-loops, G-loops, G-quadruplexes, and i-motifs, in the complementary C-rich strand. While many essential proteins at telomeres have been identified, the intricacies of their interactions and structural details are still not fully understood. This Perspective highlights recent advancements in comprehending the structures associated with human telomeres. It emphasizes the significance of telomeres, explores various telomeric structural motifs, and delves into the structural biology surrounding telomeres and telomerase. Furthermore, telomeric loops, their topologies, and the associated proteins that contribute to the safeguarding of telomeres are discussed.
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Affiliation(s)
- Abeer F R Alanazi
- UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Gary N Parkinson
- UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Shozeb Haider
- UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
- UCL Centre for Advanced Research Computing, University College London, London WC1H 9RN, United Kingdom
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2
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Misino S, Busch A, Wagner CB, Bento F, Luke B. TERRA increases at short telomeres in yeast survivors and regulates survivor associated senescence (SAS). Nucleic Acids Res 2022; 50:12829-12843. [PMID: 36513120 PMCID: PMC9825167 DOI: 10.1093/nar/gkac1125] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 10/25/2022] [Accepted: 11/08/2022] [Indexed: 12/15/2022] Open
Abstract
Cancer cells achieve immortality by employing either homology-directed repair (HDR) or the telomerase enzyme to maintain telomeres. ALT (alternative lengthening of telomeres) refers to the subset of cancer cells that employ HDR. Many ALT features are conserved from yeast to human cells, with the yeast equivalent being referred to as survivors. The non-coding RNA TERRA, and its ability to form RNA-DNA hybrids, has been implicated in ALT/survivor maintenance by promoting HDR. It is not understood which telomeres in ALT/survivors engage in HDR, nor is it clear which telomeres upregulate TERRA. Using yeast survivors as a model for ALT, we demonstrate that HDR only occurs at telomeres when they become critically short. Moreover, TERRA levels steadily increase as telomeres shorten and decrease again following HDR-mediated recombination. We observe that survivors undergo cycles of senescence, in a similar manner to non-survivors following telomerase loss, which we refer to as survivor associated senescence (SAS). Similar to 'normal' senescence, we report that RNA-DNA hybrids slow the rate of SAS, likely through the elongation of critically short telomeres, however decreasing the rate of telomere shortening may contribute to this effect. In summary, TERRA RNA-DNA hybrids regulate telomere dysfunction-induced senescence before and after survivor formation.
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Affiliation(s)
| | - Anke Busch
- Institute of Molecular Biology (IMB), Mainz, Germany
| | | | - Fabio Bento
- Institute of Developmental Biology and Neurobiology (IDN), Johannes Gutenberg-Universität, Mainz, Germany
| | - Brian Luke
- Institute of Molecular Biology (IMB), Mainz, Germany.,Institute of Developmental Biology and Neurobiology (IDN), Johannes Gutenberg-Universität, Mainz, Germany
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3
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Pérez-Martínez L, Wagner T, Luke B. Telomere Interacting Proteins and TERRA Regulation. Front Genet 2022; 13:872636. [PMID: 35464834 PMCID: PMC9024143 DOI: 10.3389/fgene.2022.872636] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 03/17/2022] [Indexed: 01/10/2023] Open
Abstract
Telomere shortening rates inversely correlate with life expectancy and hence it is critical to understand how telomere shortening is regulated. Recently, the telomeric non-coding RNA, TERRA has been implicated in the regulation of replicative senescence. To better understand how TERRA is regulated we employed a proteomics approach to look for potential RNA regulators that associate with telomeric sequences. Based on the results, we have identified proteins that may regulate TERRA in both a positive and negative manner, depending on the state of the telomere. In this mini-review, we discuss and speculate about these data to expand our understanding of TERRA and telomere interactors with respect to telomere shortening dynamics.
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Affiliation(s)
- Lara Pérez-Martínez
- Institute of Molecular Biology (IMB), Mainz, Germany
- IMDEA Food Institute, Madrid, Spain
| | - Tina Wagner
- Institute of Molecular Biology (IMB), Mainz, Germany
- Institute of Developmental Biology and Neurobiology (IDN), Johannes Gutenberg Universität, Mainz, Germany
| | - Brian Luke
- Institute of Molecular Biology (IMB), Mainz, Germany
- Institute of Developmental Biology and Neurobiology (IDN), Johannes Gutenberg Universität, Mainz, Germany
- *Correspondence: Brian Luke,
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4
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Aguilera P, Dubarry M, Hardy J, Lisby M, Simon MN, Géli V. Telomeric C-circles localize at nuclear pore complexes in Saccharomyces cerevisiae. EMBO J 2022; 41:e108736. [PMID: 35147992 PMCID: PMC8922269 DOI: 10.15252/embj.2021108736] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 01/17/2022] [Accepted: 01/21/2022] [Indexed: 11/09/2022] Open
Abstract
As in human cells, yeast telomeres can be maintained in cells lacking telomerase activity by recombination-based mechanisms known as ALT (Alternative Lengthening of Telomeres). A hallmark of ALT human cancer cells are extrachromosomal telomeric DNA elements called C-circles, whose origin and function have remained unclear. Here, we show that extrachromosomal telomeric C-circles in yeast can be detected shortly after senescence crisis and concomitantly with the production of survivors arising from "type II" recombination events. We uncover that C-circles bind to the nuclear pore complex (NPC) and to the SAGA-TREX2 complex, similar to other non-centromeric episomal DNA. Disrupting the integrity of the SAGA/TREX2 complex affects both C-circle binding to NPCs and type II telomere recombination, suggesting that NPC tethering of C-circles facilitates formation and/or propagation of the long telomere repeats characteristic of type II survivors. Furthermore, we find that disruption of the nuclear diffusion barrier impairs type II recombination. These results support a model in which concentration of C-circles at NPCs benefits type II telomere recombination, highlighting the importance of spatial coordination in ALT-type mechanisms of telomere maintenance.
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Affiliation(s)
- Paula Aguilera
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Institut Paoli-Calmettes, Equipe labellisée Ligue, Aix Marseille University, Marseille, France
| | - Marion Dubarry
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Institut Paoli-Calmettes, Equipe labellisée Ligue, Aix Marseille University, Marseille, France
| | - Julien Hardy
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Institut Paoli-Calmettes, Equipe labellisée Ligue, Aix Marseille University, Marseille, France
| | - Michael Lisby
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Marie-Noëlle Simon
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Institut Paoli-Calmettes, Equipe labellisée Ligue, Aix Marseille University, Marseille, France
| | - Vincent Géli
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Institut Paoli-Calmettes, Equipe labellisée Ligue, Aix Marseille University, Marseille, France
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5
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Mehmetbeyoglu E, Kianmehr L, Borlu M, Yilmaz Z, Basar Kılıc S, Rajabi-Maham H, Taheri S, Rassoulzadegan M. Decrease in RNase HII and Accumulation of lncRNAs/DNA Hybrids: A Causal Implication in Psoriasis? Biomolecules 2022; 12:biom12030368. [PMID: 35327560 PMCID: PMC8945458 DOI: 10.3390/biom12030368] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 02/14/2022] [Accepted: 02/21/2022] [Indexed: 02/05/2023] Open
Abstract
Functional long non-coding RNAs (lncRNAs) have been in the limelight in aging research because short telomeres are associated with higher levels of TERRA (Telomeric Repeat containing RNA). The genomic instability, which leads to short telomeres, is a mechanism observed in cell aging and in a class of cancer cells. Psoriasis, a skin disease, is a disorder of epidermal keratinocytes, with altered telomerase activity. Research on the fraction of nascent RNAs in hybrid with DNA offers avenues for new strategies. Skin and blood samples from patients were fractionated to obtain the RNA associated with DNA as a R-loop structure. The higher amount of TERRA levels attached with each chromosome end was found with psoriasis patients in blood and skin. In addition to telomeric TERRA, we evidenced accumulation of others non-coding RNA, such as non-telomeric TERRA and centromeric transcripts. Increased levels of non-coding RNAs attached to DNA correlates with a decreased in Ribonuclease HII (RNase-HII) transcript which means that overall unresolved DNA–RNA hybrids can ultimately weaken DNA and cause skin lesions. Since the genome is actively transcribed, cellular RNase-HII is essential for removing RNA from the DNA–RNA hybrid in controls of genome stability and epigenome shaping and can be used as a causal prognostic marker in patients with psoriasis.
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Affiliation(s)
- Ecmel Mehmetbeyoglu
- Betul Ziya Eren Genome and Stem Cell Center, Erciyes University, 38280 Kayseri, Turkey; (E.M.); (Z.Y.)
- Department of Medical Biology, Medical Faculty, Erciyes University, 38280 Kayseri, Turkey
| | - Leila Kianmehr
- Animal Sciences and Marine Biology Department, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran 1983963411, Iran; (H.R.-M.); (L.K.)
| | - Murat Borlu
- Dermatology and Venereology Department, Medical School, Erciyes University, 38280 Kayseri, Turkey;
| | - Zeynep Yilmaz
- Betul Ziya Eren Genome and Stem Cell Center, Erciyes University, 38280 Kayseri, Turkey; (E.M.); (Z.Y.)
- Department of Medical Biology, Medical Faculty, Erciyes University, 38280 Kayseri, Turkey
| | - Seyma Basar Kılıc
- Dermatology and Venereology Department, Training and Research Hospital, Aksaray University, 68000 Aksaray, Turkey;
| | - Hassan Rajabi-Maham
- Animal Sciences and Marine Biology Department, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran 1983963411, Iran; (H.R.-M.); (L.K.)
| | - Serpil Taheri
- Betul Ziya Eren Genome and Stem Cell Center, Erciyes University, 38280 Kayseri, Turkey; (E.M.); (Z.Y.)
- Department of Medical Biology, Medical Faculty, Erciyes University, 38280 Kayseri, Turkey
- Correspondence: (S.T.); (M.R.)
| | - Minoo Rassoulzadegan
- Betul Ziya Eren Genome and Stem Cell Center, Erciyes University, 38280 Kayseri, Turkey; (E.M.); (Z.Y.)
- INSERM-CNRS, Université de Nice, 06000 Nice, France
- Correspondence: (S.T.); (M.R.)
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6
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Rosas Bringas FR, Stinus S, de Zoeten P, Cohn M, Chang M. Rif2 protects Rap1-depleted telomeres from MRX-mediated degradation in Saccharomyces cerevisiae. eLife 2022; 11:74090. [PMID: 35044907 PMCID: PMC8791636 DOI: 10.7554/elife.74090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 01/17/2022] [Indexed: 12/01/2022] Open
Abstract
Rap1 is the main protein that binds double-stranded telomeric DNA in Saccharomyces cerevisiae. Examination of the telomere functions of Rap1 is complicated by the fact that it also acts as a transcriptional regulator of hundreds of genes and is encoded by an essential gene. In this study, we disrupt Rap1 telomere association by expressing a mutant telomerase RNA subunit (tlc1-tm) that introduces mutant telomeric repeats. tlc1-tm cells grow similar to wild-type cells, although depletion of Rap1 at telomeres causes defects in telomere length regulation and telomere capping. Rif2 is a protein normally recruited to telomeres by Rap1, but we show that Rif2 can still associate with Rap1-depleted tlc1-tm telomeres, and that this association is required to inhibit telomere degradation by the MRX complex. Rif2 and the Ku complex work in parallel to prevent tlc1-tm telomere degradation; tlc1-tm cells lacking Rif2 and the Ku complex are inviable. The partially redundant mechanisms may explain the rapid evolution of telomere components in budding yeast species.
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Affiliation(s)
| | - Sonia Stinus
- European Research Institute for the Biology of Ageing, University Medical Center Groningen
| | - Pien de Zoeten
- European Research Institute for the Biology of Ageing, University Medical Center Groningen
| | | | - Michael Chang
- European Research Institute for the Biology of Ageing, University Medical Center Groningen
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7
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Fekete-Szücs E, Rosas Bringas FR, Stinus S, Chang M. Suppression of cdc13-2-associated senescence by pif1-m2 requires Ku-mediated telomerase recruitment. G3-GENES GENOMES GENETICS 2021; 12:6395364. [PMID: 34751785 PMCID: PMC8728030 DOI: 10.1093/g3journal/jkab360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 10/08/2021] [Indexed: 11/17/2022]
Abstract
In Saccharomyces cerevisiae, recruitment of telomerase to telomeres requires an interaction between Cdc13, which binds single-stranded telomeric DNA, and the Est1 subunit of telomerase. A second pathway involving an interaction between the yKu complex and telomerase RNA (TLC1) contributes to telomerase recruitment but cannot sufficiently recruit telomerase on its own to prevent replicative senescence when the primary Cdc13-Est1 pathway is abolished—for example, in the cdc13-2 mutant. In this study, we find that mutation of PIF1, which encodes a helicase that inhibits telomerase, suppresses the replicative senescence of cdc13-2 by increasing reliance on the yKu-TLC1 pathway for telomerase recruitment. Our findings reveal new insight into telomerase-mediated telomere maintenance.
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Affiliation(s)
- Enikő Fekete-Szücs
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen 9713 AV, The Netherlands
| | - Fernando R Rosas Bringas
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen 9713 AV, The Netherlands
| | - Sonia Stinus
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen 9713 AV, The Netherlands
| | - Michael Chang
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen 9713 AV, The Netherlands
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8
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Galli M, Frigerio C, Longhese MP, Clerici M. The regulation of the DNA damage response at telomeres: focus on kinases. Biochem Soc Trans 2021; 49:933-943. [PMID: 33769480 DOI: 10.1042/bst20200856] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 03/01/2021] [Accepted: 03/02/2021] [Indexed: 11/17/2022]
Abstract
The natural ends of linear chromosomes resemble those of accidental double-strand breaks (DSBs). DSBs induce a multifaceted cellular response that promotes the repair of lesions and slows down cell cycle progression. This response is not elicited at chromosome ends, which are organized in nucleoprotein structures called telomeres. Besides counteracting DSB response through specialized telomere-binding proteins, telomeres also prevent chromosome shortening. Despite of the different fate of telomeres and DSBs, many proteins involved in the DSB response also localize at telomeres and participate in telomere homeostasis. In particular, the DSB master regulators Tel1/ATM and Mec1/ATR contribute to telomere length maintenance and arrest cell cycle progression when chromosome ends shorten, thus promoting a tumor-suppressive process known as replicative senescence. During senescence, the actions of both these apical kinases and telomere-binding proteins allow checkpoint activation while bulk DNA repair activities at telomeres are still inhibited. Checkpoint-mediated cell cycle arrest also prevents further telomere erosion and deprotection that would favor chromosome rearrangements, which are known to increase cancer-associated genome instability. This review summarizes recent insights into functions and regulation of Tel1/ATM and Mec1/ATR at telomeres both in the presence and in the absence of telomerase, focusing mainly on discoveries in budding yeast.
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Affiliation(s)
- Michela Galli
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Piazza della Scienza 2, Milano 20126, Italy
| | - Chiara Frigerio
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Piazza della Scienza 2, Milano 20126, Italy
| | - Maria Pia Longhese
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Piazza della Scienza 2, Milano 20126, Italy
| | - Michela Clerici
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Piazza della Scienza 2, Milano 20126, Italy
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TERRA G-quadruplex RNA interaction with TRF2 GAR domain is required for telomere integrity. Sci Rep 2021; 11:3509. [PMID: 33568696 PMCID: PMC7876106 DOI: 10.1038/s41598-021-82406-x] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Accepted: 01/13/2021] [Indexed: 12/15/2022] Open
Abstract
Telomere dysfunction causes chromosomal instability which is associated with many cancers and age-related diseases. The non-coding telomeric repeat-containing RNA (TERRA) forms a structural and regulatory component of the telomere that is implicated in telomere maintenance and chromosomal end protection. The basic N-terminal Gly/Arg-rich (GAR) domain of telomeric repeat-binding factor 2 (TRF2) can bind TERRA but the structural basis and significance of this interaction remains poorly understood. Here, we show that TRF2 GAR recognizes G-quadruplex features of TERRA. We show that small molecules that disrupt the TERRA-TRF2 GAR complex, such as N-methyl mesoporphyrin IX (NMM) or genetic deletion of TRF2 GAR domain, result in the loss of TERRA, and the induction of γH2AX-associated telomeric DNA damage associated with decreased telomere length, and increased telomere aberrations, including telomere fragility. Taken together, our data indicates that the G-quadruplex structure of TERRA is an important recognition element for TRF2 GAR domain and this interaction between TRF2 GAR and TERRA is essential to maintain telomere stability.
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Lee JW, Ong EBB. Genomic Instability and Cellular Senescence: Lessons From the Budding Yeast. Front Cell Dev Biol 2021; 8:619126. [PMID: 33511130 PMCID: PMC7835410 DOI: 10.3389/fcell.2020.619126] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 12/15/2020] [Indexed: 01/14/2023] Open
Abstract
Aging is a complex biological process that occurs in all living organisms. Aging is initiated by the gradual accumulation of biomolecular damage in cells leading to the loss of cellular function and ultimately death. Cellular senescence is one such pathway that leads to aging. The accumulation of nucleic acid damage and genetic alterations that activate permanent cell-cycle arrest triggers the process of senescence. Cellular senescence can result from telomere erosion and ribosomal DNA instability. In this review, we summarize the molecular mechanisms of telomere length homeostasis and ribosomal DNA stability, and describe how these mechanisms are linked to cellular senescence and longevity through lessons learned from budding yeast.
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Affiliation(s)
- Jee Whu Lee
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Penang, Malaysia.,USM-RIKEN International Centre for Aging Science (URICAS), Universiti Sains Malaysia, Penang, Malaysia
| | - Eugene Boon Beng Ong
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Penang, Malaysia.,USM-RIKEN International Centre for Aging Science (URICAS), Universiti Sains Malaysia, Penang, Malaysia
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11
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Grandin N, Gallego ME, White CI, Charbonneau M. Inhibition of the alternative lengthening of telomeres pathway by subtelomeric sequences in Saccharomyces cerevisiae. DNA Repair (Amst) 2020; 96:102996. [PMID: 33126043 DOI: 10.1016/j.dnarep.2020.102996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 09/24/2020] [Accepted: 10/04/2020] [Indexed: 10/23/2022]
Abstract
In the budding yeast Saccharomyces cerevisiae, telomerase is constitutively active and is essential for chromosome end protection and illimited proliferation of cell populations. However, upon inactivation of telomerase, alternative mechanims of telomere maintenance allow proliferation of only extremely rare survivors. S. cerevisiae type I and type II survivors differ by the nature of the donor sequences used for repair by homologous recombination of the uncapped terminal TG1-3 telomeric sequences. Type I amplifies the subtelomeric Y' sequences and is more efficient than type II, which amplifies the terminal TG1-3 repeats. However, type II survivors grow faster than type I survivors and can easily outgrow them in liquid cultures. The mechanistic interest of studying S. cerevisiae telomeric recombination is reinforced by the fact that type II recombination is the equivalent of the alternative lengthening of telomeres (ALT) pathway that is used by 5-15 % of cancer types as an alternative to telomerase reactivation. In budding yeast, only around half of the 32 telomeres harbor Y' subtelomeric elements. We report here that in strains harboring Y' elements on all telomeres, type II survivors are not observed, most likely due to an increase in the efficiency of type I recombination. However, in a temperature-sensitive cdc13-1 mutant grown at semi-permissive temperature, the increased amount of telomeric TG1-3 repeats could overcome type II inhibition by the subtelomeric Y' sequences. Strikingly, in the 100 % Y' strain the replicative senescence crisis normally provoked by inactivation of telomerase completely disappeared and the severity of the crisis was proportional to the percentage of chromosome-ends lacking Y' subtelomeric sequences. The present study highlights the fact that the nature of subtelomeric elements can influence the selection of the pathway of telomere maintenance by recombination, as well as the response of the cell to telomeric damage caused by telomerase inactivation.
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Affiliation(s)
- Nathalie Grandin
- GReD Institute, CNRS UMR6293, INSERM U1103, Faculty of Medicine, University Clermont-Auvergne, 28 place Henri Dunant, BP 38, 63001 Clermont-Ferrand Cedex, France
| | - Maria Eugenia Gallego
- GReD Institute, CNRS UMR6293, INSERM U1103, Faculty of Medicine, University Clermont-Auvergne, 28 place Henri Dunant, BP 38, 63001 Clermont-Ferrand Cedex, France
| | - Charles I White
- GReD Institute, CNRS UMR6293, INSERM U1103, Faculty of Medicine, University Clermont-Auvergne, 28 place Henri Dunant, BP 38, 63001 Clermont-Ferrand Cedex, France
| | - Michel Charbonneau
- GReD Institute, CNRS UMR6293, INSERM U1103, Faculty of Medicine, University Clermont-Auvergne, 28 place Henri Dunant, BP 38, 63001 Clermont-Ferrand Cedex, France.
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12
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A Genome-Wide Screen for Genes Affecting Spontaneous Direct-Repeat Recombination in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2020; 10:1853-1867. [PMID: 32265288 PMCID: PMC7263696 DOI: 10.1534/g3.120.401137] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Homologous recombination is an important mechanism for genome integrity maintenance, and several homologous recombination genes are mutated in various cancers and cancer-prone syndromes. However, since in some cases homologous recombination can lead to mutagenic outcomes, this pathway must be tightly regulated, and mitotic hyper-recombination is a hallmark of genomic instability. We performed two screens in Saccharomyces cerevisiae for genes that, when deleted, cause hyper-recombination between direct repeats. One was performed with the classical patch and replica-plating method. The other was performed with a high-throughput replica-pinning technique that was designed to detect low-frequency events. This approach allowed us to validate the high-throughput replica-pinning methodology independently of the replicative aging context in which it was developed. Furthermore, by combining the two approaches, we were able to identify and validate 35 genes whose deletion causes elevated spontaneous direct-repeat recombination. Among these are mismatch repair genes, the Sgs1-Top3-Rmi1 complex, the RNase H2 complex, genes involved in the oxidative stress response, and a number of other DNA replication, repair and recombination genes. Since several of our hits are evolutionarily conserved, and repeated elements constitute a significant fraction of mammalian genomes, our work might be relevant for understanding genome integrity maintenance in humans.
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13
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Xu Z, Teixeira MT. The many types of heterogeneity in replicative senescence. Yeast 2019; 36:637-648. [PMID: 31306505 PMCID: PMC6900063 DOI: 10.1002/yea.3433] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 07/04/2019] [Accepted: 07/07/2019] [Indexed: 11/10/2022] Open
Abstract
Replicative senescence, which is induced by telomere shortening, underlies the loss of regeneration capacity of organs and is ultimately detrimental to the organism. At the same time, it is required to protect organisms from unlimited cell proliferation that may arise from numerous stimuli or deregulations. One important feature of replicative senescence is its high level of heterogeneity and asynchrony, which promote genome instability and senescence escape. Characterizing this heterogeneity and investigating its sources are thus critical to understanding the robustness of replicative senescence. Here we review the different aspects of senescence driven by telomere attrition that are subject to variation in Saccharomyces cerevisiae, the current understanding of the molecular processes at play, and the consequences of heterogeneity in replicative senescence.
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Affiliation(s)
- Zhou Xu
- CNRS, UMR7238, Institut de Biologie Paris‐Seine, Laboratory of Computational and Quantitative BiologySorbonne UniversitéParisFrance
| | - Maria Teresa Teixeira
- CNRS, UMR8226, Institut de Biologie Physico‐Chimique, Laboratory of Molecular and Cell Biology of EukaryotesSorbonne Université, PSL Research UniversityParisFrance
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14
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Reilly NM, Novara L, Di Nicolantonio F, Bardelli A. Exploiting DNA repair defects in colorectal cancer. Mol Oncol 2019; 13:681-700. [PMID: 30714316 PMCID: PMC6441925 DOI: 10.1002/1878-0261.12467] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 01/11/2019] [Accepted: 01/19/2019] [Indexed: 02/06/2023] Open
Abstract
Colorectal cancer (CRC) is the third leading cause of cancer-related deaths worldwide. Therapies that take advantage of defects in DNA repair pathways have been explored in the context of breast, ovarian, and other tumor types, but not yet systematically in CRC. At present, only immune checkpoint blockade therapies have been FDA approved for use in mismatch repair-deficient colorectal tumors. Here, we discuss how systematic identification of alterations in DNA repair genes could provide new therapeutic opportunities for CRCs. Analysis of The Cancer Genome Atlas Colon Adenocarcinoma (TCGA-COAD) and Rectal Adenocarcinoma (TCGA-READ) PanCancer Atlas datasets identified 141 (out of 528) cases with putative driver mutations in 29 genes associated with DNA damage response and repair, including the mismatch repair and homologous recombination pathways. Genetic defects in these pathways might confer repair-deficient characteristics, such as genomic instability in the absence of homologous recombination, which can be exploited. For example, inhibitors of poly(ADP)-ribose polymerase are effectively used to treat cancers that carry mutations in BRCA1 and/or BRCA2 and have shown promising results in CRC preclinical studies. HR deficiency can also occur in cells with no detectable BRCA1/BRCA2 mutations but exhibiting BRCA-like phenotypes. DNA repair-targeting therapies, such as ATR and CHK1 inhibitors (which are most effective against cancers carrying ATM mutations), can be used in combination with current genotoxic chemotherapies in CRCs to further improve therapy response. Finally, therapies that target alternative DNA repair mechanisms, such as thiopurines, also have the potential to confer increased sensitivity to current chemotherapy regimens, thus expanding the spectrum of therapy options and potentially improving clinical outcomes for CRC patients.
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Affiliation(s)
- Nicole M. Reilly
- Fondazione Piemontese per la Ricerca sul Cancro ONLUSCandioloItaly
| | - Luca Novara
- Candiolo Cancer InstituteFPO‐IRCCSCandioloItaly
| | - Federica Di Nicolantonio
- Candiolo Cancer InstituteFPO‐IRCCSCandioloItaly
- Department of OncologyUniversity of TorinoCandioloItaly
| | - Alberto Bardelli
- Candiolo Cancer InstituteFPO‐IRCCSCandioloItaly
- Department of OncologyUniversity of TorinoCandioloItaly
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Misino S, Bonetti D, Luke-Glaser S, Luke B. Increased TERRA levels and RNase H sensitivity are conserved hallmarks of post-senescent survivors in budding yeast. Differentiation 2018; 100:37-45. [DOI: 10.1016/j.diff.2018.02.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 02/08/2018] [Accepted: 02/14/2018] [Indexed: 01/17/2023]
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16
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Multiple Rad52-Mediated Homology-Directed Repair Mechanisms Are Required to Prevent Telomere Attrition-Induced Senescence in Saccharomyces cerevisiae. PLoS Genet 2016; 12:e1006176. [PMID: 27428329 PMCID: PMC4948829 DOI: 10.1371/journal.pgen.1006176] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 06/15/2016] [Indexed: 12/15/2022] Open
Abstract
Most human somatic cells express insufficient levels of telomerase, which can result in telomere shortening and eventually senescence, both of which are hallmarks of ageing. Homology-directed repair (HDR) is important for maintaining proper telomere function in yeast and mammals. In Saccharomyces cerevisiae, Rad52 is required for almost all HDR mechanisms, and telomerase-null cells senesce faster in the absence of Rad52. However, its role in preventing accelerated senescence has been unclear. In this study, we make use of rad52 separation-of-function mutants to find that multiple Rad52-mediated HDR mechanisms are required to delay senescence, including break-induced replication and sister chromatid recombination. In addition, we show that misregulation of histone 3 lysine 56 acetylation, which is known to be defective in sister chromatid recombination, also causes accelerated senescence. We propose a model where Rad52 is needed to repair telomere attrition-induced replication stress. Telomeres are essential structures located at the ends of chromosomes. The canonical DNA replication machinery is unable to fully replicate DNA at chromosome ends, causing telomeres to shorten with every round of cell division. This shortening can be counteracted by an enzyme called telomerase, but in most human somatic cells, there is insufficient expression of telomerase to prevent telomere shortening. Cells with critically short telomeres can enter an arrested state known as senescence. Telomere attrition has been identified as a hallmark of human ageing. Homologous recombination proteins are important for proper telomere function in yeast and mammals. Yeast lacking both telomerase and Rad52, required for almost all recombination, exhibits accelerated senescence, yet no apparent increase in the rate of telomere shortening. In this study, we explore the role of Rad52 during senescence by taking advantage of rad52 separation-of-function mutants. We find that Rad52 acts in multiple ways to overcome DNA replication problems at telomeres. Impediments to telomere replication can be dealt with by post-replication repair mechanisms, which use a newly synthesized sister chromatid as a template to replicate past the impediment, while telomere truncations, likely caused by the collapse of replication forks, can be extended by break-induced replication.
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17
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van Mourik PM, de Jong J, Agpalo D, Claussin C, Rothstein R, Chang M. Recombination-Mediated Telomere Maintenance in Saccharomyces cerevisiae Is Not Dependent on the Shu Complex. PLoS One 2016; 11:e0151314. [PMID: 26974669 PMCID: PMC4790948 DOI: 10.1371/journal.pone.0151314] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 02/28/2016] [Indexed: 12/22/2022] Open
Abstract
In cells lacking telomerase, telomeres shorten progressively during each cell division due to incomplete end-replication. When the telomeres become very short, cells enter a state that blocks cell division, termed senescence. A subset of these cells can overcome senescence and maintain their telomeres using telomerase-independent mechanisms. In Saccharomyces cerevisiae, these cells are called ‘survivors’ and are dependent on Rad52-dependent homologous recombination and Pol32-dependent break-induced replication. There are two main types of survivors: type I and type II. The type I survivors require Rad51 and maintain telomeres by amplification of subtelomeric elements, while the type II survivors are Rad51-independent, but require the MRX complex and Sgs1 to amplify the C1–3A/TG1–3 telomeric sequences. Rad52, Pol32, Rad51, and Sgs1 are also important to prevent accelerated senescence, indicating that recombination processes are important at telomeres even before the formation of survivors. The Shu complex, which consists of Shu1, Shu2, Psy3, and Csm2, promotes Rad51-dependent homologous recombination and has been suggested to be important for break-induced replication. It also promotes the formation of recombination intermediates that are processed by the Sgs1-Top3-Rmi1 complex, as mutations in the SHU genes can suppress various sgs1, top3, and rmi1 mutant phenotypes. Given the importance of recombination processes during senescence and survivor formation, and the involvement of the Shu complex in many of the same processes during DNA repair, we hypothesized that the Shu complex may also have functions at telomeres. Surprisingly, we find that this is not the case: the Shu complex does not affect the rate of senescence, does not influence survivor formation, and deletion of SHU1 does not suppress the rapid senescence and type II survivor formation defect of a telomerase-negative sgs1 mutant. Altogether, our data suggest that the Shu complex is not important for recombination processes at telomeres.
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Affiliation(s)
- Paula M. van Mourik
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Jannie de Jong
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Danielle Agpalo
- Department of Genetics and Development, Columbia University Medical Center, New York, United States of America
| | - Clémence Claussin
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Rodney Rothstein
- Department of Genetics and Development, Columbia University Medical Center, New York, United States of America
| | - Michael Chang
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
- * E-mail:
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