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Nickens DG, Feng Z, Shen J, Gray SJ, Simmons R, Niu H, Bochman M. Cdc13 exhibits dynamic DNA strand exchange in the presence of telomeric DNA. Nucleic Acids Res 2024; 52:6317-6332. [PMID: 38613387 PMCID: PMC11194072 DOI: 10.1093/nar/gkae265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 03/22/2024] [Accepted: 04/01/2024] [Indexed: 04/14/2024] Open
Abstract
Telomerase is the enzyme that lengthens telomeres and is tightly regulated by a variety of means to maintain genome integrity. Several DNA helicases function at telomeres, and we previously found that the Saccharomyces cerevisiae helicases Hrq1 and Pif1 directly regulate telomerase. To extend these findings, we are investigating the interplay between helicases, single-stranded DNA (ssDNA) binding proteins (ssBPs), and telomerase. The yeast ssBPs Cdc13 and RPA differentially affect Hrq1 and Pif1 helicase activity, and experiments to measure helicase disruption of Cdc13/ssDNA complexes instead revealed that Cdc13 can exchange between substrates. Although other ssBPs display dynamic binding, this was unexpected with Cdc13 due to the reported in vitro stability of the Cdc13/telomeric ssDNA complex. We found that the DNA exchange by Cdc13 occurs rapidly at physiological temperatures, requires telomeric repeat sequence DNA, and is affected by ssDNA length. Cdc13 truncations revealed that the low-affinity binding site (OB1), which is distal from the high-affinity binding site (OB3), is required for this intermolecular dynamic DNA exchange (DDE). We hypothesize that DDE by Cdc13 is the basis for how Cdc13 'moves' at telomeres to alternate between modes where it regulates telomerase activity and assists in telomere replication.
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Affiliation(s)
- David G Nickens
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA
| | - Zhitong Feng
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA
| | - Jiangchuan Shen
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA
| | - Spencer J Gray
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA
| | - Robert H Simmons
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA
| | - Hengyao Niu
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA
| | - Matthew L Bochman
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA
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2
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Nickens DG, Feng Z, Shen J, Gray SJ, Simmons RH, Niu H, Bochman ML. Cdc13 exhibits dynamic DNA strand exchange in the presence of telomeric DNA. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.04.569902. [PMID: 38105973 PMCID: PMC10723391 DOI: 10.1101/2023.12.04.569902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Telomerase is the enzyme that lengthens telomeres and is tightly regulated by a variety of means to maintain genome integrity. Several DNA helicases function at telomeres, and we previously found that the Saccharomyces cerevisiae helicases Hrq1 and Pif1 directly regulate telomerase. To extend these findings, we are investigating the interplay between helicases, single-stranded DNA (ssDNA) binding proteins (ssBPs), and telomerase. The yeast ssBPs Cdc13 and RPA differentially affect Hrq1 and Pif1 helicase activity, and experiments to measure helicase disruption of Cdc13/ssDNA complexes instead revealed that Cdc13 can exchange between substrates. Although other ssBPs display dynamic binding, this was unexpected with Cdc13 due to the reported in vitro stability of the Cdc13/telomeric ssDNA complex. We found that the DNA exchange by Cdc13 occurs rapidly at physiological temperatures, requires telomeric repeat sequence DNA, and is affected by ssDNA length. Cdc13 truncations revealed that the low-affinity binding site (OB1), which is distal from the high-affinity binding site (OB3), is required for this intermolecular dynamic DNA exchange (DDE). We hypothesize that DDE by Cdc13 is the basis for how Cdc13 'moves' at telomeres to alternate between modes where it regulates telomerase activity and assists in telomere replication.
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3
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Pires VB, Lohner N, Wagner T, Wagner CB, Wilkens M, Hajikazemi M, Paeschke K, Butter F, Luke B. RNA-DNA hybrids prevent resection at dysfunctional telomeres. Cell Rep 2023; 42:112077. [PMID: 36729832 DOI: 10.1016/j.celrep.2023.112077] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 12/19/2022] [Accepted: 01/23/2023] [Indexed: 02/03/2023] Open
Abstract
At critically short telomeres, stabilized TERRA RNA-DNA hybrids drive homology-directed repair (HDR) to delay replicative senescence. However, even at long- and intermediate-length telomeres, not subject to HDR, transient TERRA RNA-DNA hybrids form, suggestive of additional roles. We report that telomeric RNA-DNA hybrids prevent Exo1-mediated resection when telomeres become non-functional. We used the well-characterized cdc13-1 allele, where telomere resection can be induced in a temperature-dependent manner, to demonstrate that ssDNA generation at telomeres is either prevented or augmented when RNA-DNA hybrids are stabilized or destabilized, respectively. The viability of cdc13-1 cells is affected by the presence or absence of hybrids accordingly. Telomeric hybrids do not affect the shortening rate of bulk telomeres. We suggest that TERRA hybrids require dynamic regulation to drive HDR at short telomeres; hybrid presence may initiate HDR through replication stress, whereby their removal allows strand resection.
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Affiliation(s)
- Vanessa Borges Pires
- Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, 4050-313 Porto, Portugal; Institute of Molecular Biology gGmbH, Ackermannweg 4, 55128 Mainz, Germany
| | - Nina Lohner
- Institute of Molecular Biology gGmbH, Ackermannweg 4, 55128 Mainz, Germany; Faculty of Biology, Institute of Developmental Biology and Neurobiology, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - Tina Wagner
- Institute of Molecular Biology gGmbH, Ackermannweg 4, 55128 Mainz, Germany
| | - Carolin B Wagner
- Institute of Molecular Biology gGmbH, Ackermannweg 4, 55128 Mainz, Germany
| | - Maya Wilkens
- Institute of Molecular Biology gGmbH, Ackermannweg 4, 55128 Mainz, Germany
| | - Mona Hajikazemi
- Clinic of Internal Medicine III, Oncology, Haematology, Rheumatology and Clinical Immunology, University Hospital Bonn, 53127 Bonn, Germany
| | - Katrin Paeschke
- Clinic of Internal Medicine III, Oncology, Haematology, Rheumatology and Clinical Immunology, University Hospital Bonn, 53127 Bonn, Germany
| | - Falk Butter
- Institute of Molecular Biology gGmbH, Ackermannweg 4, 55128 Mainz, Germany
| | - Brian Luke
- Institute of Molecular Biology gGmbH, Ackermannweg 4, 55128 Mainz, Germany; Faculty of Biology, Institute of Developmental Biology and Neurobiology, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany.
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Coloma J, Gonzalez-Rodriguez N, Balaguer FA, Gmurczyk K, Aicart-Ramos C, Nuero ÓM, Luque-Ortega JR, Calugaru K, Lue NF, Moreno-Herrero F, Llorca O. Molecular architecture and oligomerization of Candida glabrata Cdc13 underpin its telomeric DNA-binding and unfolding activity. Nucleic Acids Res 2023; 51:668-686. [PMID: 36629261 PMCID: PMC9881146 DOI: 10.1093/nar/gkac1261] [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: 05/27/2022] [Revised: 12/14/2022] [Accepted: 12/19/2022] [Indexed: 01/12/2023] Open
Abstract
The CST complex is a key player in telomere replication and stability, which in yeast comprises Cdc13, Stn1 and Ten1. While Stn1 and Ten1 are very well conserved across species, Cdc13 does not resemble its mammalian counterpart CTC1 either in sequence or domain organization, and Cdc13 but not CTC1 displays functions independently of the rest of CST. Whereas the structures of human CTC1 and CST have been determined, the molecular organization of Cdc13 remains poorly understood. Here, we dissect the molecular architecture of Candida glabrata Cdc13 and show how it regulates binding to telomeric sequences. Cdc13 forms dimers through the interaction between OB-fold 2 (OB2) domains. Dimerization stimulates binding of OB3 to telomeric sequences, resulting in the unfolding of ssDNA secondary structure. Once bound to DNA, Cdc13 prevents the refolding of ssDNA by mechanisms involving all domains. OB1 also oligomerizes, inducing higher-order complexes of Cdc13 in vitro. OB1 truncation disrupts these complexes, affects ssDNA unfolding and reduces telomere length in C. glabrata. Together, our results reveal the molecular organization of C. glabrata Cdc13 and how this regulates the binding and the structure of DNA, and suggest that yeast species evolved distinct architectures of Cdc13 that share some common principles.
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Affiliation(s)
- Javier Coloma
- Correspondence may also be addressed to Javier Coloma. Tel: +34 91 732 8000 (Ext 3033);
| | | | - Francisco A Balaguer
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Karolina Gmurczyk
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Clara Aicart-Ramos
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Óscar M Nuero
- Molecular Interactions Facility, Centro de Investigaciones Biológicas Margarita Salas (CSIC), Madrid, Spain
| | - Juan Román Luque-Ortega
- Molecular Interactions Facility, Centro de Investigaciones Biológicas Margarita Salas (CSIC), Madrid, Spain
| | - Kimberly Calugaru
- Department of Microbiology and Immunology, W. R. Hearst Microbiology Research Center, Weill Cornell Medicine, New York, NY, USA
| | - Neal F Lue
- Department of Microbiology and Immunology, W. R. Hearst Microbiology Research Center, Weill Cornell Medicine, New York, NY, USA
| | | | - Oscar Llorca
- To whom correspondence should be addressed. Tel: +34 91 732 8000 (Ext 3000);
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Spivakovsky-Gonzalez E, Polleys EJ, Masnovo C, Cebrian J, Molina-Vargas AM, Freudenreich CH, Mirkin SM. Rad9-mediated checkpoint activation is responsible for elevated expansions of GAA repeats in CST-deficient yeast. Genetics 2021; 219:6343461. [PMID: 34849883 DOI: 10.1093/genetics/iyab125] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 07/26/2021] [Indexed: 11/13/2022] Open
Abstract
Large-scale expansion of (GAA)n repeats in the first intron of the FXN gene is responsible for the severe neurodegenerative disease, Friedreich's ataxia in humans. We have previously conducted an unbiased genetic screen for GAA repeat instability in a yeast experimental system. The majority of genes that came from this screen encoded the components of DNA replication machinery, strongly implying that replication irregularities are at the heart of GAA repeat expansions. This screen, however, also produced two unexpected hits: members of the CST complex, CDC13 and TEN1 genes, which are required for telomere maintenance. To understand how the CST complex could affect intra-chromosomal GAA repeats, we studied the well-characterized temperature-sensitive cdc13-1 mutation and its effects on GAA repeat instability in yeast. We found that in-line with the screen results, this mutation leads to ∼10-fold increase in the rate of large-scale expansions of the (GAA)100 repeat at semi-permissive temperature. Unexpectedly, the hyper-expansion phenotype of the cdc13-1 mutant largely depends on activation of the G2/M checkpoint, as deletions of individual genes RAD9, MEC1, RAD53, and EXO1 belonging to this pathway rescued the increased GAA expansions. Furthermore, the hyper-expansion phenotype of the cdc13-1 mutant depended on the subunit of DNA polymerase δ, Pol32. We hypothesize, therefore, that increased repeat expansions in the cdc13-1 mutant happen during post-replicative repair of nicks or small gaps within repetitive tracts during the G2 phase of the cell cycle upon activation of the G2/M checkpoint.
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Affiliation(s)
| | - Erica J Polleys
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Chiara Masnovo
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Jorge Cebrian
- Department of Biology, Tufts University, Medford, MA 02155, USA.,Department of Pharmacology and Toxicology, School of Medicine, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, CIBERCV, Madrid 28040, Spain
| | - Adrian M Molina-Vargas
- Department of Biology, Tufts University, Medford, MA 02155, USA.,Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, NY 14642, USA
| | | | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, MA 02155, USA
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Hoerr RE, Ngo K, Friedman KL. When the Ends Justify the Means: Regulation of Telomere Addition at Double-Strand Breaks in Yeast. Front Cell Dev Biol 2021; 9:655377. [PMID: 33816507 PMCID: PMC8012806 DOI: 10.3389/fcell.2021.655377] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 02/15/2021] [Indexed: 11/23/2022] Open
Abstract
Telomeres, repetitive sequences located at the ends of most eukaryotic chromosomes, provide a mechanism to replenish terminal sequences lost during DNA replication, limit nucleolytic resection, and protect chromosome ends from engaging in double-strand break (DSB) repair. The ribonucleoprotein telomerase contains an RNA subunit that serves as the template for the synthesis of telomeric DNA. While telomere elongation is typically primed by a 3′ overhang at existing chromosome ends, telomerase can act upon internal non-telomeric sequences. Such de novo telomere addition can be programmed (for example, during chromosome fragmentation in ciliated protozoa) or can occur spontaneously in response to a chromosome break. Telomerase action at a DSB can interfere with conservative mechanisms of DNA repair and results in loss of distal sequences but may prevent additional nucleolytic resection and/or chromosome rearrangement through formation of a functional telomere (termed “chromosome healing”). Here, we review studies of spontaneous and induced DSBs in the yeast Saccharomyces cerevisiae that shed light on mechanisms that negatively regulate de novo telomere addition, in particular how the cell prevents telomerase action at DSBs while facilitating elongation of critically short telomeres. Much of our understanding comes from the use of perfect artificial telomeric tracts to “seed” de novo telomere addition. However, endogenous sequences that are enriched in thymine and guanine nucleotides on one strand (TG-rich) but do not perfectly match the telomere consensus sequence can also stimulate unusually high frequencies of telomere formation following a DSB. These observations suggest that some internal sites may fully or partially escape mechanisms that normally negatively regulate de novo telomere addition.
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Affiliation(s)
- Remington E Hoerr
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, United States
| | - Katrina Ngo
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, United States
| | - Katherine L Friedman
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, United States
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7
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Structural insights into telomere protection and homeostasis regulation by yeast CST complex. Nat Struct Mol Biol 2020; 27:752-762. [PMID: 32661422 DOI: 10.1038/s41594-020-0459-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 05/22/2020] [Indexed: 01/29/2023]
Abstract
Budding yeast Cdc13-Stn1-Ten1 (CST) complex plays an essential role in telomere protection and maintenance. Despite extensive studies, only structural information of individual domains of CST is available; the architecture of CST still remains unclear. Here, we report crystal structures of Kluyveromyces lactis Cdc13-telomeric-DNA, Cdc13-Stn1 and Stn1-Ten1 complexes and propose an integrated model depicting how CST assembles and plays its roles at telomeres. Surprisingly, two oligonucleotide/oligosaccharide-binding (OB) folds of Cdc13 (OB2 and OB4), previously believed to mediate Cdc13 homodimerization, actually form a stable intramolecular interaction. This OB2-OB4 module of Cdc13 is required for the Cdc13-Stn1 interaction that assembles CST into an architecture with a central ring-like core and multiple peripheral modules in a 2:2:2 stoichiometry. Functional analyses indicate that this unique CST architecture is essential for both telomere capping and homeostasis regulation. Overall, our results provide fundamentally valuable structural information regarding the CST complex and its roles in telomere biology.
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8
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Abstract
Telomeres are special structures at the ends of chromosomes that play an
important role in the protection of the genetic material. Telomere composition
is very diverse; noticeable differences can often be observed even among
closely related species. Here, we identify the homolog of telomeric protein
Cdc13 in the thermotolerant yeast Hansenula polymorpha. We
show that it can specifically bind single-stranded telomeric DNA, as well as
interact with the Stn1 protein. In addition, we have uncovered an interaction
between Cdc13 and TERT (one of the core components of the telomerase complex),
which suggests that Cdc13 is potentially involved in telomerase recruitment to
telomeres in H. polymorpha.
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Affiliation(s)
- A. N. Malyavko
- Faculty of Chemistry and Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991 Russia
| | - O. A. Dontsova
- Faculty of Chemistry and Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991 Russia
- Skolkovo Institute of Science and Technology, Moscow, 121205 Russia
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow, 117997 Russia
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Mersaoui SY, Wellinger RJ. Fine tuning the level of the Cdc13 telomere-capping protein for maximal chromosome stability performance. Curr Genet 2018; 65:109-118. [PMID: 30066139 DOI: 10.1007/s00294-018-0871-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 07/24/2018] [Accepted: 07/25/2018] [Indexed: 10/28/2022]
Abstract
Chromosome stability relies on an adequate length and complete replication of telomeres, the physical ends of chromosomes. Telomeres are composed of short direct repeat DNA and the associated nucleoprotein complex is essential for providing end-stability. In addition, the so-called end-replication problem of the conventional replication requires that telomeres be elongated by a special mechanism which, in virtually all organisms, is based by a reverse transcriptase, called telomerase. Although, at the conceptual level, telomere functions are highly similar in most organisms, the telomeric nucleoprotein composition appears to diverge significantly, in particular if it is compared between mammalian and budding yeast cells. However, over the last years, the CST complex has emerged as a central hub for telomere replication in most systems. Composed of three proteins, it is related to the highly conserved replication protein A complex, and in all systems studied, it coordinates telomerase-based telomere elongation with lagging-strand DNA synthesis. In budding yeast, the Cdc13 protein of this complex also is essential for telomerase recruitment and this specialisation is accompanied by additional regulatory adaptations. Based on recent results obtained in yeast, here, we review these issues and present an updated telomere replication hypothesis. We speculate that the similarities between systems far outweigh the differences, once we detach ourselves from the historic descriptions of the mechanisms in the various organisms.
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Affiliation(s)
- Sofiane Y Mersaoui
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3201 Rue Jean Mignault, Sherbrooke, QC, J1E 4K8, Canada
| | - Raymund J Wellinger
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3201 Rue Jean Mignault, Sherbrooke, QC, J1E 4K8, Canada.
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