1
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Nageshan RK, Ortega R, Krogan N, Cooper JP. Fate of telomere entanglements is dictated by the timing of anaphase midregion nuclear envelope breakdown. Nat Commun 2024; 15:4707. [PMID: 38830842 PMCID: PMC11148042 DOI: 10.1038/s41467-024-48382-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Accepted: 04/29/2024] [Indexed: 06/05/2024] Open
Abstract
Persisting replication intermediates can confer mitotic catastrophe. Loss of the fission yeast telomere protein Taz1 (ortholog of mammalian TRF1/TRF2) causes telomeric replication fork (RF) stalling and consequently, telomere entanglements that stretch between segregating mitotic chromosomes. At ≤20 °C, these entanglements fail to resolve, resulting in lethality. Rif1, a conserved DNA replication/repair protein, hinders the resolution of telomere entanglements without affecting their formation. At mitosis, local nuclear envelope (NE) breakdown occurs in the cell's midregion. Here we demonstrate that entanglement resolution occurs in the cytoplasm following this NE breakdown. However, in response to taz1Δ telomeric entanglements, Rif1 delays midregion NE breakdown at ≤20 °C, in turn disfavoring entanglement resolution. Moreover, Rif1 overexpression in an otherwise wild-type setting causes cold-specific NE defects and lethality, which are rescued by membrane fluidization. Hence, NE properties confer the cold-specificity of taz1Δ lethality, which stems from postponement of NE breakdown. We propose that such postponement promotes clearance of simple stalled RFs, but resolution of complex entanglements (involving strand invasion between nonsister telomeres) requires rapid exposure to the cytoplasm.
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Affiliation(s)
- Rishi Kumar Nageshan
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA.
| | - Raquel Ortega
- Department of Molecular Cellular and Developmental Biology, University of Colorado, Boulder, CO, USA
| | - Nevan Krogan
- Quantitative Biosciences Institute (QBI), University of California, San Francisco, CA, 94158, USA
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, 94158, USA
- Gladstone Institute of Data Science and Biotechnology, J. David Gladstone Institutes, San Francisco, CA, 94158, USA
| | - Julia Promisel Cooper
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA.
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2
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Feng HW, Zhao Y, Gao YL, Liu DT, Huo LJ. Caseinolytic mitochondrial matrix peptidase X is essential for homologous chromosome synapsis and recombination during meiosis of male mouse germ cells. Asian J Androl 2024; 26:165-174. [PMID: 37856231 PMCID: PMC10919424 DOI: 10.4103/aja202343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Accepted: 08/16/2023] [Indexed: 10/21/2023] Open
Abstract
Meiosis is the process of producing haploid gametes through a series of complex chromosomal events and the coordinated action of various proteins. The mitochondrial protease complex (ClpXP), which consists of caseinolytic mitochondrial matrix peptidase X (ClpX) and caseinolytic protease P (ClpP) and mediates the degradation of misfolded, damaged, and oxidized proteins, is essential for maintaining mitochondrial homeostasis. ClpXP has been implicated in meiosis regulation, but its precise role is currently unknown. In this study, we engineered an inducible male germ cell-specific knockout caseinolytic mitochondrial matrix peptidase X ( ClpxcKO ) mouse model to investigate the function of ClpX in meiosis. We found that disrupting Clpx in male mice induced germ cell apoptosis and led to an absence of sperm in the epididymis. Specifically, it caused asynapsis of homologous chromosomes and impaired meiotic recombination, resulting in meiotic arrest in the zygotene-to-pachytene transition phase. The loss of ClpX compromised the double-strand break (DSB) repair machinery by markedly reducing the recruitment of DNA repair protein RAD51 homolog 1 (RAD51) to DSB sites. This dysfunction may be due to an insufficient supply of energy from the aberrant mitochondria in ClpxcKO spermatocytes, as discerned by electron microscopy. Furthermore, ubiquitination signals on chromosomes and the expression of oxidative phosphorylation subunits were both significantly attenuated in ClpxcKO spermatocytes. Taken together, we propose that ClpX is essential for maintaining mitochondrial protein homeostasis and ensuring homologous chromosome pairing, synapsis, and recombination in spermatocytes during meiotic prophase I.
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Affiliation(s)
- Hai-Wei Feng
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Education Ministry of China, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
- Shenzhen Key Laboratory of Fertility Regulation, Reproductive Medicine Center, The University of Hong Kong-Shenzhen Hospital, Shenzhen 518053, China
| | - Yu Zhao
- Shenzhen Key Laboratory of Fertility Regulation, Reproductive Medicine Center, The University of Hong Kong-Shenzhen Hospital, Shenzhen 518053, China
| | - Yan-Ling Gao
- Maternal-Fetal Medicine Institute, Department of Obstetrics and Gynaecology, Shenzhen Baoan Women’s and Children’s Hospital, Jinan University, Shenzhen 518100, China
| | - Dong-Teng Liu
- Shenzhen Key Laboratory of Fertility Regulation, Reproductive Medicine Center, The University of Hong Kong-Shenzhen Hospital, Shenzhen 518053, China
- Department of Obstetrics and Gynaecology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Li-Jun Huo
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Education Ministry of China, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
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3
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Muhammad A, Sarkadi Z, van Emden T, Mazumder A, Capella M, Fekete G, Sreechakram VNS, Al-Sady B, Papp B, Barrales RR, Braun S. A systematic quantitative approach comprehensively defines domain-specific functional pathways linked to Schizosaccharomyces pombe heterochromatin regulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.13.579970. [PMID: 38405799 PMCID: PMC10888830 DOI: 10.1101/2024.02.13.579970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Heterochromatin plays a critical role in regulating gene expression and maintaining genome integrity. While structural and enzymatic components have been linked to heterochromatin establishment, a comprehensive view of the underlying pathways at diverse heterochromatin domains remains elusive. Here, we developed a systematic approach to identify factors involved in heterochromatin silencing at pericentromeres, subtelomeres, and the silent mating type locus in Schizosaccharomyces pombe. Using quantitative measures, iterative genetic screening, and domain-specific heterochromatin reporters, we identified 369 mutants with different degrees of reduced or enhanced silencing. As expected, mutations in the core heterochromatin machinery globally decreased silencing. However, most other mutants exhibited distinct qualitative and quantitative profiles that indicate domain-specific functions. For example, decreased mating type silencing was linked to mutations in heterochromatin maintenance genes, while compromised subtelomere silencing was associated with metabolic pathways. Furthermore, similar phenotypic profiles revealed shared functions for subunits within complexes. We also discovered that the uncharacterized protein Dhm2 plays a crucial role in maintaining constitutive and facultative heterochromatin, while its absence caused phenotypes akin to DNA replication-deficient mutants. Collectively, our systematic approach unveiled a landscape of domain-specific heterochromatin regulators controlling distinct states and identified Dhm2 as a previously unknown factor linked to heterochromatin inheritance and replication fidelity.
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Affiliation(s)
- Abubakar Muhammad
- Institute for Genetics, Justus-Liebig-University Giessen, Giessen, Germany
- BioMedical Center (BMC), Division of Physiological Chemistry, Faculty of Medicine, LMU Munich, Planegg-Martinsried, Germany
- International Max Planck Research School for Molecular and Cellular Life Sciences, Planegg-Martinsried, Germany
| | - Zsuzsa Sarkadi
- BioMedical Center (BMC), Division of Physiological Chemistry, Faculty of Medicine, LMU Munich, Planegg-Martinsried, Germany
- Synthetic and Systems Biology Unit, Institute of Biochemistry, HUN-REN Biological Research Centre, Szeged, Hungary
- HCEMM-BRC Metabolic Systems Biology Lab, Szeged, Hungary
| | - Thomas van Emden
- BioMedical Center (BMC), Division of Physiological Chemistry, Faculty of Medicine, LMU Munich, Planegg-Martinsried, Germany
- International Max Planck Research School for Molecular and Cellular Life Sciences, Planegg-Martinsried, Germany
| | - Agnisrota Mazumder
- Institute for Genetics, Justus-Liebig-University Giessen, Giessen, Germany
- BioMedical Center (BMC), Division of Physiological Chemistry, Faculty of Medicine, LMU Munich, Planegg-Martinsried, Germany
| | - Matias Capella
- BioMedical Center (BMC), Division of Physiological Chemistry, Faculty of Medicine, LMU Munich, Planegg-Martinsried, Germany
- Present address: Instituto de Agrobiotecnología del Litoral, CONICET, Universidad Nacional del Litoral, Santa Fe, Argentina
| | - Gergely Fekete
- Synthetic and Systems Biology Unit, Institute of Biochemistry, HUN-REN Biological Research Centre, Szeged, Hungary
- HCEMM-BRC Metabolic Systems Biology Lab, Szeged, Hungary
| | - Vishnu N Suma Sreechakram
- Institute for Genetics, Justus-Liebig-University Giessen, Giessen, Germany
- BioMedical Center (BMC), Division of Physiological Chemistry, Faculty of Medicine, LMU Munich, Planegg-Martinsried, Germany
| | - Bassem Al-Sady
- Department of Microbiology & Immunology, George Williams Hooper Foundation, University of California San Francisco, San Francisco, California, United States of America
| | - Balázs Papp
- Synthetic and Systems Biology Unit, Institute of Biochemistry, HUN-REN Biological Research Centre, Szeged, Hungary
- HCEMM-BRC Metabolic Systems Biology Lab, Szeged, Hungary
| | - Ramón Ramos Barrales
- BioMedical Center (BMC), Division of Physiological Chemistry, Faculty of Medicine, LMU Munich, Planegg-Martinsried, Germany
- Present address: Centro Andaluz de Biología del Desarrollo (CABD), Universidad Pablo de Olavide-Consejo Superior de Investigaciones Científicas-Junta de Andalucía, Seville, Spain
| | - Sigurd Braun
- Institute for Genetics, Justus-Liebig-University Giessen, Giessen, Germany
- BioMedical Center (BMC), Division of Physiological Chemistry, Faculty of Medicine, LMU Munich, Planegg-Martinsried, Germany
- International Max Planck Research School for Molecular and Cellular Life Sciences, Planegg-Martinsried, Germany
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4
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Solé M, Pascual Á, Anton E, Blanco J, Sarrate Z. The courtship choreography of homologous chromosomes: timing and mechanisms of DSB-independent pairing. Front Cell Dev Biol 2023; 11:1191156. [PMID: 37377734 PMCID: PMC10291267 DOI: 10.3389/fcell.2023.1191156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 06/01/2023] [Indexed: 06/29/2023] Open
Abstract
Meiosis involves deep changes in the spatial organisation and interactions of chromosomes enabling the two primary functions of this process: increasing genetic diversity and reducing ploidy level. These two functions are ensured by crucial events such as homologous chromosomal pairing, synapsis, recombination and segregation. In most sexually reproducing eukaryotes, homologous chromosome pairing depends on a set of mechanisms, some of them associated with the repair of DNA double-strand breaks (DSBs) induced at the onset of prophase I, and others that operate before DSBs formation. In this article, we will review various strategies utilised by model organisms for DSB-independent pairing. Specifically, we will focus on mechanisms such as chromosome clustering, nuclear and chromosome movements, as well as the involvement of specific proteins, non-coding RNA, and DNA sequences.
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Affiliation(s)
| | | | | | - Joan Blanco
- *Correspondence: Joan Blanco, ; Zaida Sarrate,
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5
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Sun H, Wu Z, Zhou Y, Lu Y, Lu H, Chen H, Shi S, Zeng Z, Wu J, Lei M. Structural insights into Pot1-ssDNA, Pot1-Tpz1 and Tpz1-Ccq1 Interactions within fission yeast shelterin complex. PLoS Genet 2022; 18:e1010308. [PMID: 35849625 PMCID: PMC9333443 DOI: 10.1371/journal.pgen.1010308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 07/28/2022] [Accepted: 06/22/2022] [Indexed: 11/30/2022] Open
Abstract
The conserved shelterin complex caps chromosome ends to protect telomeres and regulate telomere replication. In fission yeast Schizosaccharomyces pombe, shelterin consists of telomeric single- and double-stranded DNA-binding modules Pot1-Tpz1 and Taz1-Rap1 connected by Poz1, and a specific component Ccq1. While individual structures of the two DNA-binding OB folds of Pot1 (Pot1OB1-GGTTAC and Pot1OB2-GGTTACGGT) are available, structural insight into recognition of telomeric repeats with spacers by the complete DNA-binding domain (Pot1DBD) remains an open question. Moreover, structural information about the Tpz1-Ccq1 interaction requires to be revealed for understanding how the specific component Ccq1 of S. pombe shelterin is recruited to telomeres to function as an interacting hub. Here, we report the crystal structures of Pot1DBD-single-stranded-DNA, Pot1372-555-Tpz1185-212 and Tpz1425-470-Ccq1123-439 complexes and propose an integrated model depicting the assembly mechanism of the shelterin complex at telomeres. The structure of Pot1DBD-DNA unveils how Pot1 recognizes S. pombe degenerate telomeric sequences. Our analyses of Tpz1-Ccq1 reveal structural basis for the essential role of the Tpz1-Ccq1 interaction in telomere recruitment of Ccq1 that is required for telomere maintenance and telomeric heterochromatin formation. Overall, our findings provide valuable structural information regarding interactions within fission yeast shelterin complex at 3’ ss telomeric overhang. Telomeres, composed of repetitive DNA sequences and specialized proteins, are protective structures at the ends of linear chromosomes. The telomere structure is essential for the maintenance of genome integrity and stability, and telomere dysfunction has been linked to human development, aging, cancer and a variety of degenerative diseases. An evolutionarily conserved multiple-protein complex called shelterin plays versatile roles in telomere homeostasis regulation, end protection and heterochromatin establishment. However, the highly flexible nature of shelterin complex has greatly impeded our structural and functional understanding for this important complex. In fission yeast, structures of the shelterin dsDNA-binding protein subcomplex Taz1-Rap1 and the bridge subcomplex Tpz1-Poz1-Rap1 are available. Although individual OB-fold subdomains structures have been characterized, structural information about the complete Pot1DBD bound to telomeric repeats with spacers remains to be revealed. Here, by determining the crystal structures of the telomeric overhang binding Pot1DBD-ssDNA, Pot1372-555-Tpz1185-212 and Tpz1425-470-Ccq1123-439 subcomplexes, we provide structural basis not only for the recognition of S. pombe degenerate telomeric sequences by Pot1, but also for the essential function of the Tpz1-Ccq1 interaction in Ccq1 recruitment to telomeres for telomere maintenance and telomeric heterochromatin formation. These findings provide an integrated model depicting the assembly mechanism of the shelterin complex at telomeres and its multiple roles in telomere biology.
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Affiliation(s)
- Hong Sun
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
| | - Zhenfang Wu
- Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Institute of Precision Medicine, Shanghai, China
- * E-mail: (ZW); (ZZ); (JW); (ML)
| | - Yuanze Zhou
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China
| | - Yanjia Lu
- Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Institute of Precision Medicine, Shanghai, China
| | - Huaisheng Lu
- Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Institute of Precision Medicine, Shanghai, China
| | - Hongwen Chen
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
| | - Shaohua Shi
- Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Institute of Precision Medicine, Shanghai, China
| | - Zhixiong Zeng
- Shandong Provincial Key Laboratory of Microbial Engineering, College of Bioengineering, Qilu University of Technology, Shandong, China
- * E-mail: (ZW); (ZZ); (JW); (ML)
| | - Jian Wu
- Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Institute of Precision Medicine, Shanghai, China
- * E-mail: (ZW); (ZZ); (JW); (ML)
| | - Ming Lei
- Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Institute of Precision Medicine, Shanghai, China
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- * E-mail: (ZW); (ZZ); (JW); (ML)
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6
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Xia Q, Dang J, Wang P, Liang S, Wei X, Li X, Xiang S, Sun H, Wu D, Jing D, Wang S, Xia Y, He Q, Guo Q, Liang G. Low Female Gametophyte Fertility Contributes to the Low Seed Formation of the Diploid Loquat [ Eriobotrya Japonica (Thunb.) Lindl.] Line H30-6. FRONTIERS IN PLANT SCIENCE 2022; 13:882965. [PMID: 35677248 PMCID: PMC9168767 DOI: 10.3389/fpls.2022.882965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 04/19/2022] [Indexed: 06/15/2023]
Abstract
Loquat is a widely grown subtropic fruit because of its unique ripening season, nutrient content, and smooth texture of its fruits. However, loquat is not well-received because the fruits contain many large seeds. Therefore, the development of seedless or few-seed loquat varieties is the main objective of loquat breeding. Polyploidization is an effective approach for few-seed loquat breeding, but the resource is rare. The few-seed loquat line H30-6 was derived from a seedy variety. Additionally, H30-6 was systematically studied for its fruit characteristics, gamete fertility, pollen mother cell (PMC) meiosis, stigma receptivity, in situ pollen germination, fruit set, and karyotype. The results were as follows. (1) H30-6 produced only 1.54 seeds per fruit and the fruit edible rate was 70.77%. The fruit setting rate was 14.44% under open pollination, and the other qualities were equivalent to those of two other seedy varieties. (2) The in vitro pollen germination rate was only 4.04 and 77.46% of the H30-6 embryo sacs were abnormal. Stigma receptivity and self-compatibility in H30-6 were verified by in situ pollen germination and artificial pollination. Furthermore, the seed numbers in the fruits of H30-6 did not significantly differ among any of the pollination treatments (from 1.59 ±0.14 to 2 ± 0.17). (3) The chromosome configuration at meiotic diakinesis of H30-6 was 6.87I + 9.99II + 1.07III +0.69IV +0.24V (H30-6), and a total of 89.55% of H30-6 PMCs presented univalent chromosomes. Furthermore, chromosome lagging was the main abnormal phenomenon. Karyotype analysis showed that chromosomes of H30-6 had no recognizable karyotype abnormalities leading to unusual synapsis on the large scale above. (4) The abnormal embryo sacs of H30-6 could be divided into three main types: those remaining in the tetrad stage (13.38%), those remaining in the binucleate embryo sac stage (1.41%), and those without embryo sacs (52.82%). Therefore, we conclude that the loquat line H30-6 is a potential few-seed loquat resource. The diploid loquat line H30-6 was with low gametophyte fertility, which may be driven by abnormal meiotic synapses. The low female gamete fertility was the main reason for the few seeds. This diploid loquat line provides a new possibility for breeding a few-seed loquat at the diploid level.
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Affiliation(s)
- Qingqing Xia
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Jiangbo Dang
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Peng Wang
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Senlin Liang
- Economic Crops of Ziyang City, Ziyang City, China
| | - Xu Wei
- America Citrus Research and Education Center, University of Florida, Gainesville, FL, United States
| | - Xiaolin Li
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Suqiong Xiang
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Haiyan Sun
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Di Wu
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Danlong Jing
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Shumin Wang
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Yan Xia
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Qiao He
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Qigao Guo
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
| | - Guolu Liang
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Academy of Agricultural Sciences, Southwest University, Chongqing, China
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7
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Shi S, Zhou Y, Lu Y, Sun H, Xue J, Wu Z, Lei M. Ccq1-Raf2 interaction mediates CLRC recruitment to establish heterochromatin at telomeres. Life Sci Alliance 2021; 4:4/11/e202101106. [PMID: 34493579 PMCID: PMC8424379 DOI: 10.26508/lsa.202101106] [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: 04/23/2021] [Revised: 08/25/2021] [Accepted: 08/25/2021] [Indexed: 12/01/2022] Open
Abstract
This study unveils a role of Ccq1–Raf2 interaction in CLRC recruitment to establish heterochromatin at telomeres, providing a positive feedback mechanism between shelterin and CLRC for subtelomeric heterochromatin assembly. Telomeres, highly ordered DNA-protein complexes at eukaryotic linear chromosome ends, are specialized heterochromatin loci conserved among eukaryotes. In Schizosaccharomyces pombe, the shelterin complex is important for subtelomeric heterochromatin establishment. Despite shelterin has been demonstrated to mediate the recruitment of the Snf2/histone deacetylase–containing repressor complex (SHREC) and the Clr4 methyltransferase complex (CLRC) to telomeres, the mechanism involved in telomeric heterochromatin assembly remains elusive due to the multiple functions of the shelterin complex. Here, we found that CLRC plays a dominant role in heterochromatin establishment at telomeres. In addition, we identified a series of amino acids in the shelterin subunit Ccq1 that are important for the specific interaction between Ccq1 and the CLRC subunit Raf2. Finally, we demonstrated that the Ccq1–Raf2 interaction is essential for the recruitment of CLRC to telomeres, that contributes to histone H3 lysine 9 methylation, nucleosome stability and the shelterin-chromatin association, promoting a positive feedback mechanism for the nucleation and spreading of heterochromatin at subtelomeres. Together, our findings provide a mechanistic understanding of subtelomeric heterochromatin assembly by shelterin-dependent CLRC recruitment to chromosomal ends.
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Affiliation(s)
- Shaohua Shi
- State Key Laboratory of Oncogenes and Related Genes, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Institute of Precision Medicine, Shanghai, China
| | - Yuanze Zhou
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China
| | - Yanjia Lu
- State Key Laboratory of Oncogenes and Related Genes, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Institute of Precision Medicine, Shanghai, China
| | - Hong Sun
- State Key Laboratory of Molecular Biology, Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China.,School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Jing Xue
- State Key Laboratory of Molecular Biology, Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Zhenfang Wu
- State Key Laboratory of Oncogenes and Related Genes, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China .,Shanghai Institute of Precision Medicine, Shanghai, China
| | - Ming Lei
- State Key Laboratory of Oncogenes and Related Genes, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China .,Shanghai Institute of Precision Medicine, Shanghai, China.,Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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8
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Hou H, Kyriacou E, Thadani R, Klutstein M, Chapman JH, Cooper JP. Centromeres are dismantled by foundational meiotic proteins Spo11 and Rec8. Nature 2021; 591:671-676. [PMID: 33658710 PMCID: PMC8843027 DOI: 10.1038/s41586-021-03279-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 01/22/2021] [Indexed: 01/31/2023]
Abstract
Meiotic processes are potentially dangerous to genome stability and could be disastrous if activated in proliferative cells. Here we show that two key meiosis-defining proteins, the topoisomerase Spo11 (which forms double-strand breaks) and the meiotic cohesin Rec8, can dismantle centromeres. This dismantlement is normally observable only in mutant cells that lack the telomere bouquet, which provides a nuclear microdomain conducive to centromere reassembly1; however, overexpression of Spo11 or Rec8 leads to levels of centromere dismantlement that cannot be countered by the bouquet. Specific nucleosome remodelling factors mediate centromere dismantlement by Spo11 and Rec8. Ectopic expression of either protein in proliferating cells leads to the loss of mitotic kinetochores in both fission yeast and human cells. Hence, while centromeric chromatin has been characterized as extraordinarily stable, Spo11 and Rec8 challenge this stability and may jeopardize kinetochores in cancers that express meiotic proteins.
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Affiliation(s)
- Haitong Hou
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, 12801 E. 17th Ave, Aurora, CO 80045, Phone 303-724-3203,Former address: Telomere Biology Laboratory, Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892,Co-corresponding authors: ;
| | - Eftychia Kyriacou
- Former address: Telomere Biology Laboratory, Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892,Current address: Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Rahul Thadani
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, 12801 E. 17th Ave, Aurora, CO 80045, Phone 303-724-3203,Former address: Telomere Biology Laboratory, Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892
| | - Michael Klutstein
- Chromatin and Aging Research Laboratory, Institute of Dental Science, Hebrew University of Jerusalem PO 12272, Israel 91120
| | - Joseph H. Chapman
- Former address: Telomere Biology Laboratory, Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892,Current address: Single Molecular Biophysics Laboratory, NHLBI, NIH
| | - Julia Promisel Cooper
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, 12801 E. 17th Ave, Aurora, CO 80045, Phone 303-724-3203,Former address: Telomere Biology Laboratory, Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892,Co-corresponding authors: ;
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9
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Sun L, Liu XM, Li WZ, Yi YY, He X, Wang Y, Jin QW. The molecular chaperone Hsp90 regulates heterochromatin assembly through stabilizing multiple complexes in fission yeast. J Cell Sci 2020; 133:jcs244863. [PMID: 32499408 DOI: 10.1242/jcs.244863] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 05/18/2020] [Indexed: 12/18/2022] Open
Abstract
In the fission yeast Schizosaccharomyces pombe, both RNAi machinery and RNAi-independent factors mediate transcriptional and posttranscriptional silencing and heterochromatin formation. Here, we show that the silencing of reporter genes at major native heterochromatic loci (centromeres, telomeres, mating-type locus and rDNA regions) and an artificially induced heterochromatin locus is alleviated in a fission yeast hsp90 mutant, hsp90-G84C Also, H3K9me2 enrichment at heterochromatin regions, especially at the mating-type locus and subtelomeres, is compromised, suggesting heterochromatin assembly defects. We further discovered that Hsp90 is required for stabilization or assembly of the RNA-induced transcriptional silencing (RITS) and Argonaute siRNA chaperone (ARC) RNAi effector complexes, the RNAi-independent factor Fft3, the shelterin complex subunit Poz1 and the Snf2/HDAC-containing repressor complex (SHREC). Our ChIP data suggest that Hsp90 regulates the efficient recruitment of the methyltransferase/ubiquitin ligase complex CLRC by shelterin to chromosome ends and targeting of the SHREC and Fft3 to mating type locus and/or rDNA region. Finally, our genetic analyses demonstrated that increased heterochromatin spreading restores silencing at subtelomeres in the hsp90-G84C mutant. Thus, this work uncovers a conserved factor critical for promoting RNAi-dependent and -independent heterochromatin assembly and gene silencing through stabilizing multiple effectors and effector complexes.
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Affiliation(s)
- Li Sun
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen 361102, Fujian, China
| | - Xiao-Min Liu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen 361102, Fujian, China
| | - Wen-Zhu Li
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | - Yuan-Yuan Yi
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen 361102, Fujian, China
| | - Xiangwei He
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | - Yamei Wang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen 361102, Fujian, China
| | - Quan-Wen Jin
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen 361102, Fujian, China
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10
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Hua R, Wei H, Liu C, Zhang Y, Liu S, Guo Y, Cui Y, Zhang X, Guo X, Li W, Liu M. FBXO47 regulates telomere-inner nuclear envelope integration by stabilizing TRF2 during meiosis. Nucleic Acids Res 2020; 47:11755-11770. [PMID: 31724724 PMCID: PMC7145685 DOI: 10.1093/nar/gkz992] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 10/11/2019] [Accepted: 10/15/2019] [Indexed: 02/06/2023] Open
Abstract
During meiosis, telomere attachment to the inner nuclear envelope is required for proper pairing of homologous chromosomes and recombination. Here, we identified F-box protein 47 (FBXO47) as a regulator of the telomeric shelterin complex that is specifically expressed during meiotic prophase I. Knockout of Fbxo47 in mice leads to infertility in males. We found that the Fbxo47 deficient spermatocytes are unable to form a complete synaptonemal complex. FBXO47 interacts with TRF1/2, and the disruption of Fbxo47 destabilizes TRF2, leading to unstable telomere attachment and slow traversing through the bouquet stage. Our findings uncover a novel mechanism of FBXO47 in telomeric shelterin subunit stabilization during meiosis.
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Affiliation(s)
- Rong Hua
- State Key Laboratory of Reproductive Medicine, Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu, 211166, P.R. China
| | - Huafang Wei
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China.,University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Chao Liu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China.,University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Yue Zhang
- State Key Laboratory of Reproductive Medicine, Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu, 211166, P.R. China
| | - Siyu Liu
- State Key Laboratory of Reproductive Medicine, Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu, 211166, P.R. China
| | - Yueshuai Guo
- State Key Laboratory of Reproductive Medicine, Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu, 211166, P.R. China
| | - Yiqiang Cui
- State Key Laboratory of Reproductive Medicine, Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu, 211166, P.R. China
| | - Xin Zhang
- State Key Laboratory of Reproductive Medicine, Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu, 211166, P.R. China
| | - Xuejiang Guo
- State Key Laboratory of Reproductive Medicine, Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu, 211166, P.R. China
| | - Wei Li
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China.,University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Mingxi Liu
- State Key Laboratory of Reproductive Medicine, Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu, 211166, P.R. China
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11
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Lodens S, Roelants SLKW, Luyten G, Geys R, Coussement P, De Maeseneire SL, Soetaert W. Unraveling the regulation of sophorolipid biosynthesis in Starmerella bombicola. FEMS Yeast Res 2020; 20:5824630. [DOI: 10.1093/femsyr/foaa021] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 04/22/2020] [Indexed: 01/18/2023] Open
Abstract
ABSTRACTStarmerella bombicola very efficiently produces the secondary metabolites sophorolipids (SLs). Their biosynthesis is not-growth associated and highly upregulated in the stationary phase. Despite high industrial and academic interest, the underlying regulation of SL biosynthesis remains unknown. In this paper, potential regulation of SL biosynthesis through the telomere positioning effect (TPE) was investigated, as the SL gene cluster is located adjacent to a telomere. An additional copy of this gene cluster was introduced elsewhere in the genome to investigate if this results in a decoy of regulation. Indeed, for the new strain, the onset of SL production was shifted to the exponential phase. This result was confirmed by RT-qPCR analysis. The TPE effect was further investigated by developing and applying a suitable reporter system for this non-conventional yeast, enabling non-biased comparison of gene expression between the subtelomeric CYP52M1- and the URA3 locus. This was done with a constitutive endogenous promotor (pGAPD) and one of the endogenous promotors of the SL biosynthetic gene cluster (pCYP52M1). A clear positioning effect was observed for both promotors with significantly higher GFP expression levels at the URA3 locus. No clear GFP upregulation was observed in the stationary phase for any of the new strains.
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Affiliation(s)
- Sofie Lodens
- Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Sophie L K W Roelants
- Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Goedele Luyten
- Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Robin Geys
- Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Pieter Coussement
- Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Sofie L De Maeseneire
- Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Wim Soetaert
- Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
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12
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Hiraoka Y. Phase separation drives pairing of homologous chromosomes. Curr Genet 2020; 66:881-887. [PMID: 32285141 DOI: 10.1007/s00294-020-01077-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 04/04/2020] [Accepted: 04/06/2020] [Indexed: 01/06/2023]
Abstract
Pairing of homologous chromosomes is crucial for ensuring accurate segregation of chromosomes during meiosis. Molecular mechanisms of homologous chromosome pairing in meiosis have been extensively studied in the fission yeast Schizosaccharomyces pombe. In this organism, meiosis-specific noncoding RNA transcribed from specific genes accumulates at the respective gene loci, and chromosome-associated RNA-protein complexes mediate meiotic pairing of homologous loci through phase separation. Pairing of homologous chromosomes also occurs in somatic diploid cells in certain situations. For example, somatic pairing of homologous chromosomes occurs during the early embryogenesis in diptera, and relies on the transcription-associated chromatin architecture. Earlier models also suggest that transcription factories along the chromosome mediate pairing of homologous chromosomes in plants. These studies suggest that RNA bodies formed on chromosomes mediate the pairing of homologous chromosomes. This review summarizes lessons from S. pombe to provide general insights into mechanisms of homologous chromosome pairing mediated by phase separation of chromosome-associated RNA-protein complexes.
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Affiliation(s)
- Yasushi Hiraoka
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, 565-0871, Japan.
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13
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Armstrong CA, Moiseeva V, Collopy LC, Pearson SR, Ullah TR, Xi ST, Martin J, Subramaniam S, Marelli S, Amelina H, Tomita K. Fission yeast Ccq1 is a modulator of telomerase activity. Nucleic Acids Res 2019; 46:704-716. [PMID: 29216371 PMCID: PMC5778466 DOI: 10.1093/nar/gkx1223] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 11/27/2017] [Indexed: 01/05/2023] Open
Abstract
Shelterin, the telomeric protein complex, plays a crucial role in telomere homeostasis. In fission yeast, telomerase is recruited to chromosome ends by the shelterin component Tpz1 and its binding partner Ccq1, where telomerase binds to the 3' overhang to add telomeric repeats. Recruitment is initiated by the interaction of Ccq1 with the telomerase subunit Est1. However, how telomerase is released following elongation remains to be established. Here, we show that Ccq1 also has a role in the suppression of telomere elongation, when coupled with the Clr4 histone H3 methyl-transferase complex and the Clr3 histone deacetylase and nucleosome remodelling complex, SHREC. We have dissected the functions of Ccq1 by establishing a Ccq1-Est1 fusion system, which bypasses the telomerase recruitment step. We demonstrate that Ccq1 forms two distinct complexes for positive and negative telomerase regulation, with Est1 and Clr3 respectively. The negative form of Ccq1 promotes dissociation of Ccq1-telomerase from Tpz1, thereby restricting local telomerase activity. The Clr4 complex also has a negative regulation activity with Ccq1, independently of SHREC. Thus, we propose a model in which Ccq1-Est1 recruits telomerase to mediate telomere extension, whilst elongated telomeric DNA recruits Ccq1 with the chromatin-remodelling complexes, which in turn releases telomerase from the telomere.
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Affiliation(s)
- Christine A Armstrong
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK
| | - Vera Moiseeva
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK
| | - Laura C Collopy
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK
| | - Siân R Pearson
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK
| | - Tomalika R Ullah
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK.,MSc Human Molecular Genetics, Faculty of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Shidong T Xi
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK.,Faculty of Life Sciences, University College London, London WC1E 6BT, UK
| | - Jennifer Martin
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK.,MSc Human Molecular Genetics, Faculty of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Shaan Subramaniam
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK.,Faculty of Life Sciences, University College London, London WC1E 6BT, UK
| | - Sara Marelli
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK
| | - Hanna Amelina
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK
| | - Kazunori Tomita
- Chromosome Maintenance Group, UCL Cancer Institute, University College London, London WC1E 6DD, UK
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14
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Turner K, Lynch C, Rouse H, Vasu V, Griffin DK. Direct Single-Cell Analysis of Human Polar Bodies and Cleavage-Stage Embryos Reveals No Evidence of the Telomere Theory of Reproductive Ageing in Relation to Aneuploidy Generation. Cells 2019; 8:E163. [PMID: 30781491 PMCID: PMC6406255 DOI: 10.3390/cells8020163] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 01/28/2019] [Accepted: 02/13/2019] [Indexed: 01/18/2023] Open
Abstract
Reproductive ageing in women, particularly after the age of 35, is associated with an exponential increase in the proportion of chromosomally abnormal oocytes produced. Several hypotheses have attempted to explain this observation, including the 'limited oocyte pool' hypothesis and the 'two-hit' hypothesis, the latter explaining that a depletion in oocyte quality with age results from the multiple opportune stages for errors to occur in meiosis. Recently however, the telomere theory of reproductive ageing in women has been proposed. This suggests that shortened telomeres in oocytes of women of advanced maternal age render oocytes unable to support fertilization and embryogenesis. Despite a credible rationale for the telomere theory of reproductive ageing in women, very few studies have assessed telomere length directly in human oocytes or preimplantation embryos. Therefore, we directly assessed relative telomere length in first polar bodies and blastomeres from cleavage stage (day 3) embryos. In both cell types we tested the hypothesis that (1) older women have shorter telomeres and (2) chromosomally abnormal (aneuploid) gametes/embryos have shorter telomeres. In all cases, we found no evidence of altered telomere length associated with age-related aneuploidy.
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Affiliation(s)
- Kara Turner
- School of Biosciences, University of Kent, Giles Lane, Canterbury CT2 7NJ, UK.
| | - Colleen Lynch
- Cooper Genomics Nottingham, Medicity, D6 Building, Thane Road, Nottingham NG90 6BH, UK.
| | - Hannah Rouse
- Cooper Genomics Nottingham, Medicity, D6 Building, Thane Road, Nottingham NG90 6BH, UK.
| | - Vimal Vasu
- School of Biosciences, University of Kent, Giles Lane, Canterbury CT2 7NJ, UK.
- Department of Child Health, East Kent Hospitals University Foundation NHS Trust, William Harvey Hospital, Ashford TN24 0LZ, UK.
| | - Darren K Griffin
- School of Biosciences, University of Kent, Giles Lane, Canterbury CT2 7NJ, UK.
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15
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van Emden TS, Forn M, Forné I, Sarkadi Z, Capella M, Martín Caballero L, Fischer-Burkart S, Brönner C, Simonetta M, Toczyski D, Halic M, Imhof A, Braun S. Shelterin and subtelomeric DNA sequences control nucleosome maintenance and genome stability. EMBO Rep 2018; 20:embr.201847181. [PMID: 30420521 DOI: 10.15252/embr.201847181] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 10/03/2018] [Accepted: 10/12/2018] [Indexed: 11/09/2022] Open
Abstract
Telomeres and the shelterin complex cap and protect the ends of chromosomes. Telomeres are flanked by the subtelomeric sequences that have also been implicated in telomere regulation, although their role is not well defined. Here, we show that, in Schizosaccharomyces pombe, the telomere-associated sequences (TAS) present on most subtelomeres are hyper-recombinogenic, have metastable nucleosomes, and unusual low levels of H3K9 methylation. Ccq1, a subunit of shelterin, protects TAS from nucleosome loss by recruiting the heterochromatic repressor complexes CLRC and SHREC, thereby linking nucleosome stability to gene silencing. Nucleosome instability at TAS is independent of telomeric repeats and can be transmitted to an intrachromosomal locus containing an ectopic TAS fragment, indicating that this is an intrinsic property of the underlying DNA sequence. When telomerase recruitment is compromised in cells lacking Ccq1, DNA sequences present in the TAS promote recombination between chromosomal ends, independent of nucleosome abundance, implying an active function of these sequences in telomere maintenance. We propose that Ccq1 and fragile subtelomeres co-evolved to regulate telomere plasticity by controlling nucleosome occupancy and genome stability.
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Affiliation(s)
- Thomas S van Emden
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig Maximilians University of Munich, Martinsried, Germany.,International Max Planck Research School for Molecular and Cellular Life Sciences, Martinsried, Germany
| | - Marta Forn
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig Maximilians University of Munich, Martinsried, Germany
| | - Ignasi Forné
- Protein Analysis Unit (ZfP), BioMedical Center (BMC), Ludwig Maximilians University of Munich, Martinsried, Germany
| | - Zsuzsa Sarkadi
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig Maximilians University of Munich, Martinsried, Germany
| | - Matías Capella
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig Maximilians University of Munich, Martinsried, Germany
| | - Lucía Martín Caballero
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig Maximilians University of Munich, Martinsried, Germany.,International Max Planck Research School for Molecular and Cellular Life Sciences, Martinsried, Germany
| | - Sabine Fischer-Burkart
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig Maximilians University of Munich, Martinsried, Germany
| | - Cornelia Brönner
- Department of Biochemistry, Gene Center, Ludwig Maximilians University of Munich, Munich, Germany
| | - Marco Simonetta
- Department of Biophysics and Biochemistry, University of California San Francisco (UCSF), San Francisco, CA, USA
| | - David Toczyski
- Department of Biophysics and Biochemistry, University of California San Francisco (UCSF), San Francisco, CA, USA
| | - Mario Halic
- Department of Biochemistry, Gene Center, Ludwig Maximilians University of Munich, Munich, Germany
| | - Axel Imhof
- Protein Analysis Unit (ZfP), BioMedical Center (BMC), Ludwig Maximilians University of Munich, Martinsried, Germany
| | - Sigurd Braun
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig Maximilians University of Munich, Martinsried, Germany .,International Max Planck Research School for Molecular and Cellular Life Sciences, Martinsried, Germany
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16
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Greenstein RA, Al-Sady B. Epigenetic fates of gene silencing established by heterochromatin spreading in cell identity and genome stability. Curr Genet 2018; 65:423-428. [PMID: 30390097 DOI: 10.1007/s00294-018-0901-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 10/24/2018] [Accepted: 10/27/2018] [Indexed: 01/20/2023]
Abstract
Heterochromatin spreading, the propagation of repressive chromatin along the chromosome, is a reaction critical to genome stability and defense, as well as maintenance of unique cell fates. Here, we discuss the intrinsic properties of the spreading reaction and circumstances under which its products, formed distal to DNA-encoded nucleation sites, can be epigenetically maintained. Finally, we speculate that the epigenetic properties of heterochromatin evolved together with the need to stabilize cellular identity.
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Affiliation(s)
- R A Greenstein
- Department of Microbiology and Immunology, George Williams Hooper Foundation, University of California San Francisco, San Francisco, CA, 94143, USA.,TETRAD Graduate Program, University of California San Francisco, San Francisco, CA, 94143, USA
| | - Bassem Al-Sady
- Department of Microbiology and Immunology, George Williams Hooper Foundation, University of California San Francisco, San Francisco, CA, 94143, USA.
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17
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Ebrahimi H, Masuda H, Jain D, Cooper JP. Distinct 'safe zones' at the nuclear envelope ensure robust replication of heterochromatic chromosome regions. eLife 2018; 7:32911. [PMID: 29722648 PMCID: PMC5933923 DOI: 10.7554/elife.32911] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 03/30/2018] [Indexed: 12/24/2022] Open
Abstract
Chromosome replication and transcription occur within a complex nuclear milieu whose functional subdomains are beginning to be mapped out. Here we delineate distinct domains of the fission yeast nuclear envelope (NE), focusing on regions enriched for the inner NE protein, Bqt4, or the lamin interacting domain protein, Lem2. Bqt4 is relatively mobile around the NE and acts in two capacities. First, Bqt4 tethers chromosome termini and the mat locus to the NE specifically while these regions are replicating. This positioning is required for accurate heterochromatin replication. Second, Bqt4 mobilizes a subset of Lem2 molecules around the NE to promote pericentric heterochromatin maintenance. Opposing Bqt4-dependent Lem2 mobility are factors that stabilize Lem2 beneath the centrosome, where Lem2 plays a crucial role in kinetochore maintenance. Our data prompt a model in which Bqt4-rich nuclear subdomains are 'safe zones' in which collisions between transcription and replication are averted and heterochromatin is reassembled faithfully.
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Affiliation(s)
- Hani Ebrahimi
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, United States
| | - Hirohisa Masuda
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, United States
| | - Devanshi Jain
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, United States
| | - Julia Promisel Cooper
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, United States
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18
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Abstract
Meiosis halves diploid chromosome numbers to haploid levels that are essential for sexual reproduction in most eukaryotes. Meiotic recombination ensures the formation of bivalents between homologous chromosomes (homologs) and their subsequent proper segregation. It also results in genetic diversity among progeny that influences evolutionary responses to selection. Moreover, crop breeding depends upon the action of meiotic recombination to rearrange elite traits between parental chromosomes. An understanding of the molecular mechanisms that drive meiotic recombination is important for both fundamental research and practical applications. This review emphasizes advances made during the past 5 years, primarily in Arabidopsis and rice, by summarizing newly characterized genes and proteins and examining the regulatory mechanisms that modulate their action.
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Affiliation(s)
- Yingxiang Wang
- State Key Laboratory of Genetic Engineering and Collaborative Innovation Center of Genetics and Development, Ministry of Education Key Laboratory of Biodiversity Sciences and Ecological Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, China;
| | - Gregory P Copenhaver
- Department of Biology and the Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280, USA;
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-3280, USA
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19
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LARP7-like protein Pof8 regulates telomerase assembly and poly(A)+TERRA expression in fission yeast. Nat Commun 2018; 9:586. [PMID: 29422503 PMCID: PMC5805695 DOI: 10.1038/s41467-018-02874-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 01/05/2018] [Indexed: 02/06/2023] Open
Abstract
Telomerase is a reverse transcriptase complex that ensures stable maintenance of linear eukaryotic chromosome ends by overcoming the end replication problem, posed by the inability of replicative DNA polymerases to fully replicate linear DNA. The catalytic subunit TERT must be assembled properly with its telomerase RNA for telomerase to function, and studies in Tetrahymena have established that p65, a La-related protein 7 (LARP7) family protein, utilizes its C-terminal xRRM domain to promote assembly of the telomerase ribonucleoprotein (RNP) complex. However, LARP7-dependent telomerase complex assembly has been considered as unique to ciliates that utilize RNA polymerase III to transcribe telomerase RNA. Here we show evidence that fission yeast Schizosaccharomyces pombe utilizes the p65-related protein Pof8 and its xRRM domain to promote assembly of RNA polymerase II-encoded telomerase RNA with TERT. Furthermore, we show that Pof8 contributes to repression of the transcription of noncoding RNAs at telomeres. A functional telomerase complex requires that the catalytic TERT subunit be assembled with the template RNA TER1. Here the authors show that Pof8, a possible LARP7 family protein, is required for assembly of the telomerase complex, and repression of lncRNA transcripts at telomeres in S. pombe.
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20
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Hou H, Cooper JP. Stretching, scrambling, piercing and entangling: Challenges for telomeres in mitotic and meiotic chromosome segregation. Differentiation 2018; 100:12-20. [PMID: 29413748 DOI: 10.1016/j.diff.2018.01.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 01/21/2018] [Accepted: 01/23/2018] [Indexed: 12/24/2022]
Abstract
The consequences of telomere loss or dysfunction become most prominent when cells enter the nuclear division stage of the cell cycle. At this climactic stage when chromosome segregation occurs, telomere fusions or entanglements can lead to chromosome breakage, wreaking havoc on genome stability. Here we review recent progress in understanding the mechanisms of detangling and breaking telomere associations at mitosis, as well as the unique ways in which telomeres are processed to allow regulated sister telomere separation. Moreover, we discuss unexpected roles for telomeres in orchestrating nuclear envelope breakdown and spindle formation, crucial processes for nuclear division. Finally, we discuss the discovery that telomeres create microdomains in the nucleus that are conducive to centromere assembly, cementing the unexpectedly influential role of telomeres in mitosis.
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Affiliation(s)
- Haitong Hou
- Telomere Biology Section, LBMB, NCI, NIH, Building 37, Room 6050, Bethesda MD 20892, USA
| | - Julia Promisel Cooper
- Telomere Biology Section, LBMB, NCI, NIH, Building 37, Room 6050, Bethesda MD 20892, USA.
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21
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Structure of the fission yeast S. pombe telomeric Tpz1-Poz1-Rap1 complex. Cell Res 2017; 27:1503-1520. [PMID: 29160296 DOI: 10.1038/cr.2017.145] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 09/29/2017] [Accepted: 10/19/2017] [Indexed: 01/01/2023] Open
Abstract
Telomeric shelterin complex caps chromosome ends and plays a crucial role in telomere maintenance and protection. In the fission yeast Schizosaccharomyces pombe, shelterin is composed of telomeric single- and double-stranded DNA-binding protein subcomplexes Pot1-Tpz1 and Taz1-Rap1, which are bridged by their interacting protein Poz1. However, the structure of Poz1 and how Poz1 functions as an interaction hub in the shelterin complex remain unclear. Here we report the crystal structure of Poz1 in complex with Poz1-binding motifs of Tpz1 and Rap1. The crystal structure shows that Poz1 employs two different binding surfaces to interact with Tpz1 and Rap1. Unexpectedly, the structure also reveals that Poz1 adopts a dimeric conformation. Mutational analyses suggest that proper interactions between Tpz1, Poz1, and Rap1 in the shelterin core complex are required for telomere length homeostasis and heterochromatin structure maintenance at telomeres. Structural resemblance between Poz1 and the TRFH domains of other shelterin proteins in fission yeast and humans suggests a model for the evolution of shelterin proteins.
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22
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Tashiro S, Nishihara Y, Kugou K, Ohta K, Kanoh J. Subtelomeres constitute a safeguard for gene expression and chromosome homeostasis. Nucleic Acids Res 2017; 45:10333-10349. [PMID: 28981863 PMCID: PMC5737222 DOI: 10.1093/nar/gkx780] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Accepted: 08/28/2017] [Indexed: 12/19/2022] Open
Abstract
The subtelomere, a telomere-adjacent chromosomal domain, contains species-specific homologous DNA sequences, in addition to various genes. However, the functions of subtelomeres, particularly subtelomeric homologous (SH) sequences, remain elusive. Here, we report the first comprehensive analyses of the cellular functions of SH sequences in the fission yeast, Schizosaccharomyces pombe. Complete removal of SH sequences from the genome revealed that they are dispensable for mitosis, meiosis and telomere length control. However, when telomeres are lost, SH sequences prevent deleterious inter-chromosomal end fusion by facilitating intra-chromosomal circularization. Surprisingly, SH-deleted cells sometimes survive telomere loss through inter-chromosomal end fusions via homologous loci such as LTRs, accompanied by centromere inactivation of either chromosome. Moreover, SH sequences function as a buffer region against the spreading of subtelomeric heterochromatin into the neighboring gene-rich regions. Furthermore, we found a nucleosome-free region at the subtelomeric border, which may be a second barrier that blocks heterochromatin spreading into the subtelomere-adjacent euchromatin. Thus, our results demonstrate multiple defense functions of subtelomeres in chromosome homeostasis and gene expression.
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Affiliation(s)
- Sanki Tashiro
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Yuki Nishihara
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Kazuto Kugou
- Department of Life Sciences, University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
| | - Kunihiro Ohta
- Department of Life Sciences, University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
| | - Junko Kanoh
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
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23
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Alleva B, Smolikove S. Moving and stopping: Regulation of chromosome movement to promote meiotic chromosome pairing and synapsis. Nucleus 2017; 8:613-624. [PMID: 28892406 DOI: 10.1080/19491034.2017.1358329] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Meiosis is a specialized cellular division occurring in organisms capable of sexual reproduction that leads to the formation of gametes containing half of the original chromosome number. During the earliest stage of meiosis, prophase I, pairing of homologous chromosomes is achieved in preparation for their proper distribution in the coming divisions. An important question is how do homologous chromosomes find each other and establish pairing interactions. Early studies demonstrated that chromosomes are dynamic in nature and move during this early stage of meiosis. More recently, there have been several studies across different models showing the conserved nature and importance of this chromosome movement, as well as the key components involved in chromosome movement. This review will cover these major findings and also introduce unexamined areas of regulation in meiotic prophase I chromosome movement.
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Affiliation(s)
- Benjamin Alleva
- a Department of Biology , The University of Iowa , Iowa City, IA , USA
| | - Sarit Smolikove
- a Department of Biology , The University of Iowa , Iowa City, IA , USA
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24
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Katsumata K, Nishi E, Afrin S, Narusawa K, Yamamoto A. Position matters: multiple functions of LINC-dependent chromosome positioning during meiosis. Curr Genet 2017; 63:1037-1052. [PMID: 28493118 DOI: 10.1007/s00294-017-0699-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 04/14/2017] [Accepted: 04/29/2017] [Indexed: 10/19/2022]
Abstract
Chromosome positioning is crucial for multiple chromosomal events, including DNA replication, repair, and recombination. The linker of nucleoskeleton and cytoskeleton (LINC) complexes, which consist of conserved nuclear membrane proteins, were shown to control chromosome positioning and facilitate various biological processes by interacting with the cytoskeleton. However, the precise functions and regulation of LINC-dependent chromosome positioning are not fully understood. During meiosis, the LINC complexes induce clustering of telomeres, forming the bouquet chromosome arrangement, which promotes homologous chromosome pairing. In fission yeast, the bouquet forms through LINC-dependent clustering of telomeres at the spindle pole body (SPB, the centrosome equivalent in fungi) and detachment of centromeres from the SPB-localized LINC. It was recently found that, in fission yeast, the bouquet contributes to formation of the spindle and meiotic centromeres, in addition to homologous chromosome pairing, and that centromere detachment is linked to telomere clustering, which is crucial for proper spindle formation. Here, we summarize these findings and show that the bouquet chromosome arrangement also contributes to nuclear fusion during karyogamy. The available evidence suggests that these functions are universal among eukaryotes. The findings demonstrate that LINC-dependent chromosome positioning performs multiple functions and controls non-chromosomal as well as chromosomal events, and that the chromosome positioning is stringently regulated for its functions. Thus, chromosome positioning plays a much broader role and is more strictly regulated than previously thought.
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Affiliation(s)
- Kazuhiro Katsumata
- Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8529, Japan
| | - Eriko Nishi
- Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8529, Japan
| | - Sadia Afrin
- Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8529, Japan
| | - Kaoru Narusawa
- Department of Chemistry, Faculty of Science, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8529, Japan
| | - Ayumu Yamamoto
- Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8529, Japan.
- Department of Chemistry, Faculty of Science, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8529, Japan.
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25
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Abstract
Acquisition of oocyte polarity involves complex translocation and aggregation of intracellular organelles, RNAs, and proteins, along with strict posttranscriptional regulation. While much is still unknown regarding the formation of the animal-vegetal axis, an early marker of polarity, animal models have contributed to our understanding of these early processes controlling normal oogenesis and embryo development. In recent years, it has become clear that proteins with self-assembling properties are involved in assembling discrete subcellular compartments or domains underlying subcellular asymmetries in the early mitotic and meiotic cells of the female germline. These include asymmetries in duplication of the centrioles and formation of centrosomes and assembly of the organelle and RNA-rich Balbiani body, which plays a critical role in oocyte polarity. Notably, at specific stages of germline development, these transient structures in oocytes are temporally coincident and align with asymmetries in the position and arrangement of nuclear components, such as the nuclear pore and the chromosomal bouquet and the centrioles and cytoskeleton in the cytoplasm. Formation of these critical, transient structures and arrangements involves microtubule pathways, intrinsically disordered proteins (proteins with domains that tend to be fluid or lack a rigid ordered three-dimensional structure ranging from random coils, globular domains, to completely unstructured proteins), and translational repressors and activators. This review aims to examine recent literature and key players in oocyte polarity.
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Affiliation(s)
- Mara Clapp
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine of Yeshiva University, Bronx, NY, USA
| | - Florence L Marlow
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine of Yeshiva University, Bronx, NY, USA.
- Department of Neuroscience, Albert Einstein College of Medicine of Yeshiva University, Bronx, NY, USA.
- Department of Cell, Developmental and Regenerative Medicine, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1020, New York, NY, 10029-6574, USA.
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Koyama M, Nagakura W, Tanaka H, Kujirai T, Chikashige Y, Haraguchi T, Hiraoka Y, Kurumizaka H. In vitro reconstitution and biochemical analyses of the Schizosaccharomyces pombe nucleosome. Biochem Biophys Res Commun 2016; 482:896-901. [PMID: 27890612 DOI: 10.1016/j.bbrc.2016.11.130] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Accepted: 11/23/2016] [Indexed: 10/20/2022]
Abstract
Schizosaccharomyces pombe, which has a small genome but shares many physiological functions with higher eukaryotes, is a useful single-cell, model eukaryotic organism. In particular, many features concerning chromatin structure and dynamics, including heterochromatin, centromeres, telomeres, and DNA replication origins, are well conserved between S. pombe and higher eukaryotes. However, the S. pombe nucleosome, the fundamental structural unit of chromatin, has not been reconstituted in vitro. In the present study, we established the method to purify S. pombe histones H2A, H2B, H3, and H4, and successfully reconstituted the S. pombe nucleosome in vitro. Our thermal stability assay and micrococcal nuclease treatment assay revealed that the S. pombe nucleosome is markedly unstable and its DNA ends are quite accessible, as compared to the canonical human nucleosome. These findings are important to understand the mechanisms of epigenetic genomic DNA regulation in fission yeast.
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Affiliation(s)
- Masako Koyama
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Wataru Nagakura
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Hiroki Tanaka
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Tomoya Kujirai
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Yuji Chikashige
- Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe 651-2492, Japan
| | - Tokuko Haraguchi
- Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe 651-2492, Japan; Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yasushi Hiraoka
- Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe 651-2492, Japan; Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Hitoshi Kurumizaka
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan; Research Institute for Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan; Institute for Medical-oriented Structural Biology, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
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27
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Cam HP, Whitehall S. Analysis of Heterochromatin in Schizosaccharomyces pombe. Cold Spring Harb Protoc 2016; 2016:2016/11/pdb.top079889. [PMID: 27803258 DOI: 10.1101/pdb.top079889] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This introduction briefly describes the biology of heterochromatin in the fission yeast Schizosaccharomyces pombe We highlight some of the salient features of fission yeast that render it an excellent unicellular eukaryote for studying heterochromatin. We then discuss key aspects of heterochromatin that are of interest to those in the field, and last we introduce experimental approaches often used to investigate heterochromatin.
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Affiliation(s)
- Hugh P Cam
- Biology Department, Boston College, Chestnut Hill, Massachusetts 02467
| | - Simon Whitehall
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle NE2 4HH, United Kingdom
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28
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Braun S, Barrales RR. Beyond Tethering and the LEM domain: MSCellaneous functions of the inner nuclear membrane Lem2. Nucleus 2016; 7:523-531. [PMID: 27797637 DOI: 10.1080/19491034.2016.1252892] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The nuclear envelope plays a pivotal role in the functional organization of chromatin. Various inner nuclear membrane (INM) proteins associate with transcriptionally repressed chromatin, which is often found at the nuclear periphery. A prominent example is the conserved family of LEM (LAP2-Emerin-MAN1) domain proteins that interact with DNA-binding proteins and have been proposed to mediate tethering of chromatin to the nuclear membrane. We recently reported that the fission yeast protein Lem2, a homolog of metazoan LEM proteins, contributes to perinuclear localization and silencing of heterochromatin. 1 We demonstrate that binding and tethering of centromeric chromatin depends on the LEM domain of Lem2. Unexpectedly, this domain is dispensable for heterochromatin silencing, which is instead mediated by a different structural domain of Lem2, the MSC (MAN1-Src1 C-terminal) domain. Hence, silencing and tethering by Lem2 can be mechanistically separated. Notably, the MSC domain has multiple functions beyond heterochromatic silencing. Here we discuss the implications of these novel findings for the understanding of this conserved INM protein.
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Affiliation(s)
- Sigurd Braun
- a Department of Physiological Chemistry , Biomedical Center (BMC), Ludwig-Maximilians-University of Munich , Martinsried , Germany
| | - Ramón Ramos Barrales
- a Department of Physiological Chemistry , Biomedical Center (BMC), Ludwig-Maximilians-University of Munich , Martinsried , Germany.,b Present address: Centro Andaluz de Biología del Desarrollo. Universidad Pablo de Olavide, Sevilla-CSIC-Junta de Andalucía , Sevilla , Spain
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29
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A Taz1- and Microtubule-Dependent Regulatory Relationship between Telomere and Centromere Positions in Bouquet Formation Secures Proper Meiotic Divisions. PLoS Genet 2016; 12:e1006304. [PMID: 27611693 PMCID: PMC5017736 DOI: 10.1371/journal.pgen.1006304] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 08/17/2016] [Indexed: 01/01/2023] Open
Abstract
During meiotic prophase, telomeres cluster, forming the bouquet chromosome arrangement, and facilitate homologous chromosome pairing. In fission yeast, bouquet formation requires switching of telomere and centromere positions. Centromeres are located at the spindle pole body (SPB) during mitotic interphase, and upon entering meiosis, telomeres cluster at the SPB, followed by centromere detachment from the SPB. Telomere clustering depends on the formation of the microtubule-organizing center at telomeres by the linker of nucleoskeleton and cytoskeleton complex (LINC), while centromere detachment depends on disassembly of kinetochores, which induces meiotic centromere formation. However, how the switching of telomere and centromere positions occurs during bouquet formation is not fully understood. Here, we show that, when impaired telomere interaction with the LINC or microtubule disruption inhibited telomere clustering, kinetochore disassembly-dependent centromere detachment and accompanying meiotic centromere formation were also inhibited. Efficient centromere detachment required telomere clustering-dependent SPB recruitment of a conserved telomere component, Taz1, and microtubules. Furthermore, when artificial SPB recruitment of Taz1 induced centromere detachment in telomere clustering-defective cells, spindle formation was impaired. Thus, detachment of centromeres from the SPB without telomere clustering causes spindle impairment. These findings establish novel regulatory mechanisms, which prevent concurrent detachment of telomeres and centromeres from the SPB during bouquet formation and secure proper meiotic divisions. Meiosis is a type of cell division, that generates haploid gametes and is essential for sexual reproduction. During meiosis, telomeres cluster on a small region of the nuclear periphery, forming a conserved chromosome arrangement referred to as the “bouquet”. Because the bouquet arrangement facilitates homologous chromosome pairing, which is essential for proper meiotic chromosome segregation, it is of great importance to understand how the bouquet arrangement is formed. In fission yeast, the bouquet arrangement requires switching of telomere and centromere positions. During mitosis, centromeres are located at the fungal centrosome called the spindle pole body (SPB). Upon entering meiosis, telomeres cluster at the SPB, and centromeres become detached from the SPB, forming the bouquet arrangement. In this study, we show that centromere detachment is linked with telomere clustering. When telomere clustering was inhibited, centromere detachment was also inhibited. This regulatory relationship depended on a conserved telomere component, Taz1, and microtubules. Furthermore, we show that the regulatory relationship is crucial for proper meiotic divisions when telomere clustering is defective. Our findings reveal a hitherto unknown regulatory relationship between meiotic telomere and centromere positions in bouquet formation, which secures proper meiotic divisions.
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30
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Sepsiova R, Necasova I, Willcox S, Prochazkova K, Gorilak P, Nosek J, Hofr C, Griffith JD, Tomaska L. Evolution of Telomeres in Schizosaccharomyces pombe and Its Possible Relationship to the Diversification of Telomere Binding Proteins. PLoS One 2016; 11:e0154225. [PMID: 27101289 PMCID: PMC4839565 DOI: 10.1371/journal.pone.0154225] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 04/11/2016] [Indexed: 11/30/2022] Open
Abstract
Telomeres of nuclear chromosomes are usually composed of an array of tandemly repeated sequences that are recognized by specific Myb domain containing DNA-binding proteins (telomere-binding proteins, TBPs). Whereas in many eukaryotes the length and sequence of the telomeric repeat is relatively conserved, telomeric sequences in various yeasts are highly variable. Schizosaccharomyces pombe provides an excellent model for investigation of co-evolution of telomeres and TBPs. First, telomeric repeats of S. pombe differ from the canonical mammalian type TTAGGG sequence. Second, S. pombe telomeres exhibit a high degree of intratelomeric heterogeneity. Third, S. pombe contains all types of known TBPs (Rap1p [a version unable to bind DNA], Tay1p/Teb1p, and Taz1p) that are employed by various yeast species to protect their telomeres. With the aim of reconstructing evolutionary paths leading to a separation of roles between Teb1p and Taz1p, we performed a comparative analysis of the DNA-binding properties of both proteins using combined qualitative and quantitative biochemical approaches. Visualization of DNA-protein complexes by electron microscopy revealed qualitative differences of binding of Teb1p and Taz1p to mammalian type and fission yeast telomeres. Fluorescence anisotropy analysis quantified the binding affinity of Teb1p and Taz1p to three different DNA substrates. Additionally, we carried out electrophoretic mobility shift assays using mammalian type telomeres and native substrates (telomeric repeats, histone-box sequences) as well as their mutated versions. We observed relative DNA sequence binding flexibility of Taz1p and higher binding stringency of Teb1p when both proteins were compared directly to each other. These properties may have driven replacement of Teb1p by Taz1p as the TBP in fission yeast.
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Affiliation(s)
- Regina Sepsiova
- Department of Genetics, Comenius University in Bratislava, Faculty of Natural Sciences, Ilkovicova 6, 842 15, Bratislava, Slovak Republic
| | - Ivona Necasova
- Chromatin Molecular Complexes, Central European Institute of Technology, Masaryk University, Brno, CZ-62500, Czech Republic
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, CZ-62500, Czech Republic
| | - Smaranda Willcox
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, United States of America
| | - Katarina Prochazkova
- Department of Genetics, Comenius University in Bratislava, Faculty of Natural Sciences, Ilkovicova 6, 842 15, Bratislava, Slovak Republic
| | - Peter Gorilak
- Department of Genetics, Comenius University in Bratislava, Faculty of Natural Sciences, Ilkovicova 6, 842 15, Bratislava, Slovak Republic
| | - Jozef Nosek
- Department of Biochemistry, Comenius University in Bratislava, Faculty of Natural Sciences, Ilkovicova 6, 842 15, Bratislava, Slovak Republic
| | - Ctirad Hofr
- Chromatin Molecular Complexes, Central European Institute of Technology, Masaryk University, Brno, CZ-62500, Czech Republic
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, CZ-62500, Czech Republic
| | - Jack D. Griffith
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, United States of America
| | - Lubomir Tomaska
- Department of Genetics, Comenius University in Bratislava, Faculty of Natural Sciences, Ilkovicova 6, 842 15, Bratislava, Slovak Republic
- * E-mail:
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31
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Wang J, Cohen AL, Letian A, Tadeo X, Moresco JJ, Liu J, Yates JR, Qiao F, Jia S. The proper connection between shelterin components is required for telomeric heterochromatin assembly. Genes Dev 2016; 30:827-39. [PMID: 26988418 PMCID: PMC4826398 DOI: 10.1101/gad.266718.115] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 02/24/2016] [Indexed: 12/31/2022]
Abstract
Telomeric regions contain prominent sites of heterochromatin, which is associated with unique histone modification profiles such as the methylation of histone H3 at Lys9 (H3K9me). In fission yeast, the conserved telomeric shelterin complex recruits the histone H3K9 methyltransferase complex CLRC to establish subtelomeric heterochromatin. Although many shelterin mutations affect subtelomeric heterochromatin assembly, the mechanism remains elusive due to the diverse functions of shelterin. Through affinity purification, we found that shelterin directly associates with CLRC through the Ccq1 subunit. Surprisingly, mutations that disrupt interactions between shelterin subunits compromise subtelomeric heterochromatin without affecting CLRC interaction with shelterin component Pot1, located at chromosome ends. We further discovered that telomeric repeats are refractory to heterochromatin spreading and that artificial restoration of shelterin connections or increased heterochromatin spreading rescued heterochromatin defects in these shelterin mutants. Thus, subtelomeric heterochromatin assembly requires both the recruitment of CLRC by shelterin to chromosome ends and the proper connection of shelterin components, which allows CLRC to skip telomeric repeats to internal regions.
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Affiliation(s)
- Jiyong Wang
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Allison L Cohen
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Anudari Letian
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Xavier Tadeo
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - James J Moresco
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Jinqiang Liu
- Department of Biological Chemistry, University of California at Irvine, Irvine, California 92697, USA
| | - John R Yates
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Feng Qiao
- Department of Biological Chemistry, University of California at Irvine, Irvine, California 92697, USA
| | - Songtao Jia
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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32
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Meiotic cohesin-based chromosome structure is essential for homologous chromosome pairing in Schizosaccharomyces pombe. Chromosoma 2015; 125:205-14. [PMID: 26511279 PMCID: PMC4830870 DOI: 10.1007/s00412-015-0551-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 10/07/2015] [Accepted: 10/09/2015] [Indexed: 11/30/2022]
Abstract
Chromosome structure is dramatically altered upon entering meiosis to establish chromosomal architectures necessary for the successful progression of meiosis-specific events. An early meiotic event involves the replacement of the non-SMC mitotic cohesins with their meiotic equivalents in most part of the chromosome, forming an axis on meiotic chromosomes. We previously demonstrated that the meiotic cohesin complex is required for chromosome compaction during meiotic prophase in the fission yeast Schizosaccharomyces pombe. These studies revealed that chromosomes are elongated in the absence of the meiotic cohesin subunit Rec8 and shortened in the absence of the cohesin-associated protein Pds5. In this study, using super-resolution structured illumination microscopy, we found that Rec8 forms a linear axis on chromosomes, which is required for the organized axial structure of chromatin during meiotic prophase. In the absence of Pds5, the Rec8 axis is shortened whereas chromosomes are widened. In rec8 or pds5 mutants, the frequency of homologous chromosome pairing is reduced. Thus, Rec8 and Pds5 play an essential role in building a platform to support the chromosome architecture necessary for the spatial alignment of homologous chromosomes.
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33
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Mizuguchi T, Barrowman J, Grewal SIS. Chromosome domain architecture and dynamic organization of the fission yeast genome. FEBS Lett 2015; 589:2975-86. [PMID: 26096785 PMCID: PMC4598268 DOI: 10.1016/j.febslet.2015.06.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 06/08/2015] [Accepted: 06/09/2015] [Indexed: 12/20/2022]
Abstract
Advanced techniques including the chromosome conformation capture (3C) methodology and its derivatives are complementing microscopy approaches to study genome organization, and are revealing new details of three-dimensional (3D) genome architecture at increasing resolution. The fission yeast Schizosaccharomyces pombe (S. pombe) comprises a small genome featuring organizational elements of more complex eukaryotic systems, including conserved heterochromatin assembly machinery. Here we review key insights into genome organization revealed in this model system through a variety of techniques. We discuss the predominant role of Rabl-like configuration for interphase chromosome organization and the dynamic changes that occur during mitosis and meiosis. High resolution Hi-C studies have also revealed the presence of locally crumpled chromatin regions called "globules" along chromosome arms, and implicated a critical role for pericentromeric heterochromatin in imposing fundamental constraints on the genome to maintain chromosome territoriality and stability. These findings have shed new light on the connections between genome organization and function. It is likely that insights gained from the S. pombe system will also broadly apply to higher eukaryotes.
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Affiliation(s)
- Takeshi Mizuguchi
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Jemima Barrowman
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Shiv I S Grewal
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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Hoffman CS, Wood V, Fantes PA. An Ancient Yeast for Young Geneticists: A Primer on the Schizosaccharomyces pombe Model System. Genetics 2015; 201:403-23. [PMID: 26447128 PMCID: PMC4596657 DOI: 10.1534/genetics.115.181503] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The fission yeast Schizosaccharomyces pombe is an important model organism for the study of eukaryotic molecular and cellular biology. Studies of S. pombe, together with studies of its distant cousin, Saccharomyces cerevisiae, have led to the discovery of genes involved in fundamental mechanisms of transcription, translation, DNA replication, cell cycle control, and signal transduction, to name but a few processes. However, since the divergence of the two species approximately 350 million years ago, S. pombe appears to have evolved less rapidly than S. cerevisiae so that it retains more characteristics of the common ancient yeast ancestor, causing it to share more features with metazoan cells. This Primer introduces S. pombe by describing the yeast itself, providing a brief description of the origins of fission yeast research, and illustrating some genetic and bioinformatics tools used to study protein function in fission yeast. In addition, a section on some key differences between S. pombe and S. cerevisiae is included for readers with some familiarity with budding yeast research but who may have an interest in developing research projects using S. pombe.
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Affiliation(s)
- Charles S Hoffman
- Biology Department, Boston College, Chestnut Hill, Massachusetts 02467
| | - Valerie Wood
- Cambridge Systems Biology Centre and Department of Biochemistry, University of Cambridge, CB2 1GA Cambridge, United Kingdom
| | - Peter A Fantes
- School of Biological Sciences, College of Science and Engineering, University of Edinburgh EH9 3JR Edinburgh, United Kingdom
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35
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Moser BA, Raguimova ON, Nakamura TM. Ccq1-Tpz1TPP1 interaction facilitates telomerase and SHREC association with telomeres in fission yeast. Mol Biol Cell 2015; 26:3857-66. [PMID: 26354422 PMCID: PMC4626069 DOI: 10.1091/mbc.e15-07-0481] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/04/2015] [Indexed: 01/31/2023] Open
Abstract
Through characterization of ccq1 mutants that disrupt Ccq1-Tpz1TPP1 interaction, the authors establish that Ccq1-Tpz1TPP1 interaction contributes to optimal binding of the Ccq1-SHREC complex and is required for Ccq1 Thr93 phosphorylation and telomerase recruitment. Evolutionarily conserved shelterin complex is essential for telomere maintenance in the fission yeast Schizosaccharomyces pombe. Elimination of the fission yeast shelterin subunit Ccq1 causes progressive loss of telomeres due to the inability to recruit telomerase, activates the DNA damage checkpoint, and loses heterochromatin at telomere/subtelomere regions due to reduced recruitment of the heterochromatin regulator complex Snf2/histone deacetylase–containing repressor complex (SHREC). The shelterin subunit Tpz1TPP1 directly interacts with Ccq1 through conserved C-terminal residues in Tpz1TPP1, and tpz1 mutants that fail to interact with Ccq1 show telomere shortening, checkpoint activation, and loss of heterochromatin. While we have previously concluded that Ccq1-Tpz1TPP1 interaction contributes to Ccq1 accumulation and telomerase recruitment based on analysis of tpz1 mutants that fail to interact with Ccq1, another study reported that loss of Ccq1-Tpz1TPP1 interaction does not affect accumulation of Ccq1 or telomerase. Furthermore, it remained unclear whether loss of Ccq1-Tpz1TPP1 interaction affects SHREC accumulation at telomeres. To resolve these issues, we identified and characterized a series of ccq1 mutations that disrupt Ccq1-Tpz1TPP1 interaction. Characterization of these ccq1 mutants established that Ccq1-Tpz1TPP1 interaction contributes to optimal binding of the Ccq1-SHREC complex, and is critical for Rad3ATR/Tel1ATM-dependent Ccq1 Thr93 phosphorylation and telomerase recruitment.
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Affiliation(s)
- Bettina A Moser
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607
| | - Olga N Raguimova
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607
| | - Toru M Nakamura
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607
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36
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Abstract
The conserved shelterin complex is critical for chromosome capping and maintaining telomere length homeostasis. Using a combination of deletions, fusions and tethers, Pan et al. define key elements of shelterin important for telomere length regulation. The conserved shelterin complex is critical for chromosome capping and maintaining telomere length homeostasis. In fission yeast, shelterin is comprised of five proteins. Taz1, Rap1, and Poz1 function as negative regulators of telomere elongation, whereas Pot1 and Tpz1 are critical for end capping and telomerase recruitment. How the five proteins work together to safeguard chromosome ends and promote telomere length homeostasis is a matter of great interest. Using a combination of deletions, fusions, and tethers, we define key elements of shelterin important for telomere length regulation. Surprisingly, deletion of the entire Rap1 and Poz1 proteins does not impair telomere length regulation as long as a static bridge is provided between Taz1 and Tpz1. Cells harboring minishelterin display wild-type telomere length and intact subtelomeric silencing. However, protection against end fusions in G1 is compromised in the absence of Rap1. Our data reveal a remarkable plasticity in shelterin architecture and separate functions in length regulation and end protection.
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37
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Allshire RC, Ekwall K. Epigenetic Regulation of Chromatin States in Schizosaccharomyces pombe. Cold Spring Harb Perspect Biol 2015; 7:a018770. [PMID: 26134317 DOI: 10.1101/cshperspect.a018770] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This article discusses the advances made in epigenetic research using the model organism fission yeast Schizosaccharomyces pombe. S. pombe has been used for epigenetic research since the discovery of position effect variegation (PEV). This is a phenomenon in which a transgene inserted within heterochromatin is variably expressed, but can be stably inherited in subsequent cell generations. PEV occurs at centromeres, telomeres, ribosomal DNA (rDNA) loci, and mating-type regions of S. pombe chromosomes. Heterochromatin assembly in these regions requires enzymes that modify histones and the RNA interference (RNAi) machinery. One of the key histone-modifying enzymes is the lysine methyltransferase Clr4, which methylates histone H3 on lysine 9 (H3K9), a classic hallmark of heterochromatin. The kinetochore is assembled on specialized chromatin in which histone H3 is replaced by the variant CENP-A. Studies in fission yeast have contributed to our understanding of the establishment and maintenance of CENP-A chromatin and the epigenetic activation and inactivation of centromeres.
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Affiliation(s)
- Robin C Allshire
- Wellcome Trust Centre for Cell Biology, The University of Edinburgh, Edinburgh EH9 3JR, Scotland, United Kingdom
| | - Karl Ekwall
- Department of Biosciences and Nutrition, Karolinska Institutet, Center for Biosciences, NOVUM, S-141 83, Huddinge, Sweden
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Klutstein M, Fennell A, Fernández-Álvarez A, Cooper JP. The telomere bouquet regulates meiotic centromere assembly. Nat Cell Biol 2015; 17:458-69. [PMID: 25774833 DOI: 10.1038/ncb3132] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2014] [Accepted: 02/10/2015] [Indexed: 12/12/2022]
Abstract
The role of the conserved meiotic telomere bouquet has been enigmatic for over a century. We showed previously that disruption of the fission yeast bouquet impairs spindle formation in approximately half of meiotic cells. Surprisingly, bouquet-deficient meiocytes with functional spindles harbour chromosomes that fail to achieve spindle attachment. Kinetochore proteins and the centromeric histone H3 variant Cnp1 fail to localize to those centromeres that exhibit spindle attachment defects in the bouquet's absence. The HP1 orthologue Swi6 also fails to bind these centromeres, suggesting that compromised pericentromeric heterochromatin underlies the kinetochore defects. We find that centromeres are prone to disassembly during meiosis, but this is reversed by localization of centromeres to the telomere-proximal microenvironment, which is conducive to heterochromatin formation and centromere reassembly. Accordingly, artificially tethering a centromere to a telomere rescues the tethered centromere but not other centromeres. These results reveal an unanticipated level of control of centromeres by telomeres.
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Affiliation(s)
- Michael Klutstein
- 1] National Cancer Institute, NIH, Bethesda, Maryland 20892, USA [2] Cancer Research UK, London Research Institute, London WC2A 3LY, UK
| | - Alex Fennell
- 1] National Cancer Institute, NIH, Bethesda, Maryland 20892, USA [2] Cancer Research UK, London Research Institute, London WC2A 3LY, UK
| | - Alfonso Fernández-Álvarez
- 1] National Cancer Institute, NIH, Bethesda, Maryland 20892, USA [2] Cancer Research UK, London Research Institute, London WC2A 3LY, UK
| | - Julia Promisel Cooper
- 1] National Cancer Institute, NIH, Bethesda, Maryland 20892, USA [2] Cancer Research UK, London Research Institute, London WC2A 3LY, UK
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Lorenzi LE, Bah A, Wischnewski H, Shchepachev V, Soneson C, Santagostino M, Azzalin CM. Fission yeast Cactin restricts telomere transcription and elongation by controlling Rap1 levels. EMBO J 2014; 34:115-29. [PMID: 25398909 DOI: 10.15252/embj.201489559] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The telomeric transcriptome comprises multiple long non-coding RNAs generated by transcription of linear chromosome ends. In a screening performed in Schizosaccharomyces pombe, we identified factors modulating the cellular levels of the telomeric transcriptome. Among these factors, Cay1 is the fission yeast member of the conserved family of Cactins, uncharacterized proteins crucial for cell growth and survival. In cay1∆ mutants, the cellular levels of the telomeric factor Rap1 are drastically diminished due to defects in rap1+ pre-mRNA splicing and Rap1 protein stability. cay1∆ cells accumulate histone H3 acetylated at lysine 9 at telomeres, which become transcriptionally desilenced, are over-elongated by telomerase and cause chromosomal aberrations in the cold. Overexpressing Rap1 in cay1+ deleted cells significantly reverts all telomeric defects. Additionally, cay1∆ mutants accumulate unprocessed Tf2 retrotransposon RNA through Rap1-independent mechanisms. Thus, Cay1 plays crucial roles in cells by ultimately harmonizing expression of transcripts originating from seemingly unrelated genomic loci.
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Affiliation(s)
- Luca E Lorenzi
- Institute of Biochemistry (IBC) Eidgenössische Technische Hochschule Zürich (ETHZ), Zürich, Switzerland
| | - Amadou Bah
- Institute of Biochemistry (IBC) Eidgenössische Technische Hochschule Zürich (ETHZ), Zürich, Switzerland
| | - Harry Wischnewski
- Institute of Biochemistry (IBC) Eidgenössische Technische Hochschule Zürich (ETHZ), Zürich, Switzerland
| | - Vadim Shchepachev
- Institute of Biochemistry (IBC) Eidgenössische Technische Hochschule Zürich (ETHZ), Zürich, Switzerland
| | - Charlotte Soneson
- Bioinformatics Core Facility, SIB Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Marco Santagostino
- Dipartimento di Biologia e Biotecnologie "L. Spallanzani", Università degli Studi di Pavia, Pavia, Italy
| | - Claus M Azzalin
- Institute of Biochemistry (IBC) Eidgenössische Technische Hochschule Zürich (ETHZ), Zürich, Switzerland
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40
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Harland JL, Chang YT, Moser BA, Nakamura TM. Tpz1-Ccq1 and Tpz1-Poz1 interactions within fission yeast shelterin modulate Ccq1 Thr93 phosphorylation and telomerase recruitment. PLoS Genet 2014; 10:e1004708. [PMID: 25330395 PMCID: PMC4199508 DOI: 10.1371/journal.pgen.1004708] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 08/26/2014] [Indexed: 11/22/2022] Open
Abstract
In both fission yeast and humans, the shelterin complex plays central roles in regulation of telomerase recruitment, protection of telomeres against DNA damage response factors, and formation of heterochromatin at telomeres. While shelterin is essential for limiting activation of the DNA damage checkpoint kinases ATR and ATM at telomeres, these kinases are required for stable maintenance of telomeres. In fission yeast, Rad3ATR and Tel1ATM kinases are redundantly required for telomerase recruitment, since Rad3ATR/Tel1ATM-dependent phosphorylation of the shelterin subunit Ccq1 at Thr93 promotes interaction between Ccq1 and the telomerase subunit Est1. However, it remained unclear how protein-protein interactions within the shelterin complex (consisting of Taz1, Rap1, Poz1, Tpz1, Pot1 and Ccq1) contribute to the regulation of Ccq1 Thr93 phosphorylation and telomerase recruitment. In this study, we identify domains and amino acid residues that are critical for mediating Tpz1-Ccq1 and Tpz1-Poz1 interaction within the fission yeast shelterin complex. Using separation of function Tpz1 mutants that maintain Tpz1-Pot1 interaction but specifically disrupt either Tpz1-Ccq1 or Tpz1-Poz1 interaction, we then establish that Tpz1-Ccq1 interaction promotes Ccq1 Thr93 phosphorylation, telomerase recruitment, checkpoint inhibition and telomeric heterochromatin formation. Furthermore, we demonstrate that Tpz1-Poz1 interaction promotes telomere association of Poz1, and loss of Poz1 from telomeres leads to increases in Ccq1 Thr93 phosphorylation and telomerase recruitment, and telomeric heterochromatin formation defect. In addition, our studies establish that Tpz1-Poz1 and Tpz1-Ccq1 interactions redundantly fulfill the essential telomere protection function of the shelterin complex, since simultaneous loss of both interactions caused immediate loss of cell viability for the majority of cells and generation of survivors with circular chromosomes. Based on these findings, we suggest that the negative regulatory function of Tpz1-Poz1 interaction works upstream of Rad3ATR kinase, while Tpz1-Ccq1 interaction works downstream of Rad3ATR kinase to facilitate Ccq1 Thr93 phosphorylation and telomerase recruitment. Proper maintenance of telomeres is essential for maintaining genomic stability, and genomic instability caused by dysfunctional telomeres could lead to accumulation of mutations that may drive tumor formation. Telomere dysfunction has also been linked to premature aging caused by depletion of stem cells. Therefore, it is important to understand how cells ensure proper maintenance of telomeres. Mammalian cells and fission yeast cells utilize an evolutionarily conserved multi-subunit telomere protection complex called shelterin to ensure protection against telomere fusions by DNA repair factors and cell cycle arrest by DNA damage checkpoint kinases. However, previous studies have not yet fully established how protein-protein interactions within the shelterin complex contribute to the regulation of DNA damage checkpoint signaling and telomerase recruitment. By utilizing separation of function mutations that specifically disrupt either Tpz1-Ccq1 or Tpz1-Poz1 interaction within the fission yeast shelterin, we establish that Tpz1-Ccq1 interaction is essential for phosphorylation of Ccq1 by the DNA damage checkpoint kinases Rad3ATR and Tel1ATM that is needed for telomerase recruitment to telomeres, while Tpz1-Poz1 interaction prevents Ccq1 phosphorylation by promoting Poz1 association with telomeres. These findings thus establish for the first time how protein-protein interactions within the shelterin complex modulate checkpoint kinase-dependent phosphorylation essential for telomerase recruitment.
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Affiliation(s)
- Jennifer L. Harland
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Ya-Ting Chang
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Bettina A. Moser
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Toru M. Nakamura
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
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41
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Wang J, Tadeo X, Hou H, Andrews S, Moresco JJ, Yates JR, Nagy PL, Jia S. Tls1 regulates splicing of shelterin components to control telomeric heterochromatin assembly and telomere length. Nucleic Acids Res 2014; 42:11419-32. [PMID: 25245948 PMCID: PMC4191416 DOI: 10.1093/nar/gku842] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Heterochromatin preferentially forms at repetitive DNA elements through RNAi-mediated targeting of histone-modifying enzymes. It was proposed that splicing factors interact with the RNAi machinery or regulate the splicing of repeat transcripts to directly participate in heterochromatin assembly. Here, by screening the fission yeast deletion library, we comprehensively identified factors required for telomeric heterochromatin assembly, including a novel gene tls1+. Purification of Tls1 and mass spectrometry analysis of its interacting proteins show that Tls1 associates with the spliceosome subunit Brr2. RNA sequencing analysis shows that the splicing of a subset of mRNAs are affected in tls1Δ cells, including mRNAs of shelterin components rap1+ and poz1+. Importantly, replacing rap1+ and poz1+ with their cDNAs significantly alleviated heterochromatin defects of tls1Δ cells, suggesting that the missplicing of shelterin components is the cause of such defects, and that splicing factors regulate telomeric heterochromatin through the proper splicing of heterochromatin factors. In addition to its role in telomeric heterochromatin assembly, Tls1-mediated splicing of shelterin mRNAs also regulates telomere length. Given that its human homologue C9ORF78 also associates with the spliceosome and is overexpressed in multiple cancer cell lines, our results suggest that C9ORF78 overexpression might alter the proper splicing of genes during cancer progression.
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Affiliation(s)
- Jiyong Wang
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Xavier Tadeo
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Haitong Hou
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Stuart Andrews
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - James J Moresco
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA, USA
| | - John R Yates
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA, USA
| | - Peter L Nagy
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - Songtao Jia
- Department of Biological Sciences, Columbia University, New York, NY, USA
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42
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Yamamoto A. Gathering up meiotic telomeres: a novel function of the microtubule-organizing center. Cell Mol Life Sci 2014; 71:2119-34. [PMID: 24413667 PMCID: PMC11113538 DOI: 10.1007/s00018-013-1548-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 12/12/2013] [Accepted: 12/19/2013] [Indexed: 11/26/2022]
Abstract
During meiosis, telomeres cluster and promote homologous chromosome pairing. Telomere clustering depends on conserved SUN and KASH domain nuclear membrane proteins, which form a complex called the linker of nucleoskeleton and cytoskeleton (LINC) and connect telomeres with the cytoskeleton. It has been thought that LINC-mediated cytoskeletal forces induce telomere clustering. However, how cytoskeletal forces induce telomere clustering is not fully understood. Recent study of fission yeast has shown that the LINC complex forms the microtubule-organizing center (MTOC) at the telomere, which has been designated as the "telocentrosome", and that microtubule motors gather telomeres via telocentrosome-nucleated microtubules. This MTOC-dependent telomere clustering might be conserved in other eukaryotes. Furthermore, the MTOC-dependent clustering mechanism appears to function in various other biological events. This review presents an overview of the current understanding of the mechanism of meiotic telomere clustering and discusses the universality of the MTOC-dependent clustering mechanism.
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Affiliation(s)
- Ayumu Yamamoto
- Department of Chemistry, Graduate School of Science, Shizuoka University, 836 Ohya, Suruga-ku, Sizuoka, 422-8529, Japan,
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43
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Kallgren SP, Andrews S, Tadeo X, Hou H, Moresco JJ, Tu PG, Yates JR, Nagy PL, Jia S. The proper splicing of RNAi factors is critical for pericentric heterochromatin assembly in fission yeast. PLoS Genet 2014; 10:e1004334. [PMID: 24874881 PMCID: PMC4038458 DOI: 10.1371/journal.pgen.1004334] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 03/06/2014] [Indexed: 11/19/2022] Open
Abstract
Heterochromatin preferentially assembles at repetitive DNA elements, playing roles in transcriptional silencing, recombination suppression, and chromosome segregation. The RNAi machinery is required for heterochromatin assembly in a diverse range of organisms. In fission yeast, RNA splicing factors are also required for pericentric heterochromatin assembly, and a prevailing model is that splicing factors provide a platform for siRNA generation independently of their splicing activity. Here, by screening the fission yeast deletion library, we discovered four novel splicing factors that are required for pericentric heterochromatin assembly. Sequencing total cellular RNAs from the strongest of these mutants, cwf14Δ, showed intron retention in mRNAs of several RNAi factors. Moreover, introducing cDNA versions of RNAi factors significantly restored pericentric heterochromatin in splicing mutants. We also found that mutations of splicing factors resulted in defective telomeric heterochromatin assembly and mis-splicing the mRNA of shelterin component Tpz1, and that replacement of tpz1+ with its cDNA partially rescued heterochromatin defects at telomeres in splicing mutants. Thus, proper splicing of RNAi and shelterin factors contributes to heterochromatin assembly at pericentric regions and telomeres.
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Affiliation(s)
- Scott P. Kallgren
- Department of Biological Sciences, Columbia University, New York, New York, United States of America
| | - Stuart Andrews
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Xavier Tadeo
- Department of Biological Sciences, Columbia University, New York, New York, United States of America
| | - Haitong Hou
- Department of Biological Sciences, Columbia University, New York, New York, United States of America
| | - James J. Moresco
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Patricia G. Tu
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, United States of America
| | - John R. Yates
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Peter L. Nagy
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Songtao Jia
- Department of Biological Sciences, Columbia University, New York, New York, United States of America
- * E-mail:
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44
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Klutstein M, Cooper JP. The Chromosomal Courtship Dance-homolog pairing in early meiosis. Curr Opin Cell Biol 2014; 26:123-31. [PMID: 24529254 DOI: 10.1016/j.ceb.2013.12.004] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 12/10/2013] [Accepted: 12/11/2013] [Indexed: 02/02/2023]
Abstract
The intermingling of genomes that characterizes sexual reproduction requires haploid gametes in which parental homologs have recombined. For this, homologs must pair during meiosis. In a crowded nucleus where sequence homology is obscured by the enormous scale and packaging of the genome, partner alignment is no small task. Here we review the early stages of this process. Chromosomes first establish an initial docking site, usually at telomeres or centromeres. The acquisition of chromosome-specific patterns of binding factors facilitates homolog recognition. Chromosomes are then tethered to the nuclear envelope (NE) and subjected to nuclear movements that 'shake off' inappropriate contacts while consolidating homolog associations. Thereafter, homolog connections are stabilized by building the synaptonemal complex or its equivalent and creating genetic crossovers. Recent perspectives on the roles of these stages will be discussed.
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Affiliation(s)
- Michael Klutstein
- Cancer Research UK, London Research Institute, NIH, London WC2A 3LY, United Kingdom; National Cancer Institute, NIH, Bethesda, MD 20892, United States
| | - Julia Promisel Cooper
- Cancer Research UK, London Research Institute, NIH, London WC2A 3LY, United Kingdom; National Cancer Institute, NIH, Bethesda, MD 20892, United States.
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45
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Tadeo X, Wang J, Kallgren SP, Liu J, Reddy BD, Qiao F, Jia S. Elimination of shelterin components bypasses RNAi for pericentric heterochromatin assembly. Genes Dev 2014; 27:2489-99. [PMID: 24240238 PMCID: PMC3841737 DOI: 10.1101/gad.226118.113] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The RNAi pathway is required for heterochromatin assembly, and loss of RNAi causes pericentric heterochromatin defects. Tadeo et al. show that deletion of telomere shelterin components in RNAi mutants restores pericentric heterochromatin. Shelterin component Poz1 mutant analysis reveals that defective telomere silencing, but not telomere length control, is critical for bypassing RNAi. Furthermore, heterochromatin protein Swi6 is redistributed to pericentric regions in RNAi mutants. Heterochromatin domains thus use multiple pathways to restrain Swi6 and avoid promiscuous heterochromatin formation. The RNAi pathway is required for heterochromatin assembly at repetitive DNA elements in diverse organisms. In fission yeast, loss of RNAi causes pericentric heterochromatin defects, compromising gene silencing and chromosome segregation. Here we show that deletion of telomere shelterin components restores pericentric heterochromatin and its functions in RNAi mutants. We further isolated a separation-of-function mutant of Poz1 and revealed that defective telomere silencing, but not telomere length control, is critical for bypassing RNAi. Further analyses demonstrated that compromising shelterin-mediated heterochromatin assembly in RNAi mutants releases heterochromatin protein Swi6, which is redistributed to pericentric regions through RNAi-independent heterochromatin assembly pathways. Given the high mobility of Swi6 protein and that increased levels of Swi6 facilitates heterochromatin spreading as well as ectopic heterochromatin assembly, our results suggest that constitutive heterochromatin domains use multiple pathways to form high-affinity platforms to restrain Swi6, thus limiting its availability and avoiding promiscuous heterochromatin formation.
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Affiliation(s)
- Xavier Tadeo
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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46
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A single internal telomere tract ensures meiotic spindle formation. EMBO Rep 2013; 14:252-60. [PMID: 23295325 DOI: 10.1038/embor.2012.218] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Revised: 12/03/2012] [Accepted: 12/04/2012] [Indexed: 11/09/2022] Open
Abstract
Contact between telomeres and the fission yeast spindle pole body during meiotic prophase is crucial for subsequent spindle assembly, but the feature of telomeres that confers their ability to promote spindle formation remains mysterious. Here we show that while strains harbouring circular chromosomes devoid of telomere repeat tracts undergo aberrant meiosis with defective spindles, the insertion of a single internal telomere repeat stretch rescues the spindle defects. Moreover, the telomeric overhang-binding protein Pot1 is dispensable for rescue of spindle formation. Hence, an inherent feature of the double-strand telomeric region endows telomeres with the capacity to promote spindle formation.
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Abstract
Gametogenesis combines two important features: reduction of the genome content from diploid to haploid by carefully partitioning chromosomes, and the subsequent differentiation into fertilization-competent gametes, which in males is characterized by profound nuclear restructuring. These are quite difficult tasks and require a tight coordination of different cellular mechanisms. Recent studies in the field established a key role for LINC complexes in both meiosis and sperm head formation. LINC complexes comprise SUN and KASH domain proteins that form nuclear envelope (NE) bridges, linking the nucleoskeleton to the cytoskeleton. They are well known for their crucial roles in diverse cellular and developmental processes, such as nuclear positioning and cell polarization. In this review, we highlight key roles ascribed to LINC complexes and to the nucleocytoskeletal connection in gametogenesis. First, we give a short overview about the general features of LINC components and the profound reorganization of the NE in germ cells. We then focus on specific roles of LINC complexes in meiotic chromosome dynamics and their impact on pairing, synapsis, and recombination. Finally, we provide an update of the mechanisms controlling sperm head formation and discuss the role of sperm-specific LINC complexes in nuclear shaping and their relation to specialized cytoskeletal structures that form concurrently with nuclear restructuring and sperm elongation.
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Affiliation(s)
- Martin P Kracklauer
- Department of Physiology, Wayne State University Medical School, Detroit, Michigan, USA
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Dehé PM, Rog O, Ferreira M, Greenwood J, Cooper J. Taz1 Enforces Cell-Cycle Regulation of Telomere Synthesis. Mol Cell 2012; 46:797-808. [DOI: 10.1016/j.molcel.2012.04.022] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 02/21/2012] [Accepted: 04/13/2012] [Indexed: 01/14/2023]
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Moser BA, Chang YT, Kosti J, Nakamura TM. Tel1ATM and Rad3ATR kinases promote Ccq1-Est1 interaction to maintain telomeres in fission yeast. Nat Struct Mol Biol 2011; 18:1408-13. [PMID: 22101932 PMCID: PMC3230746 DOI: 10.1038/nsmb.2187] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 10/19/2011] [Indexed: 12/22/2022]
Abstract
The shelterin complex plays both positive and negative roles in telomerase regulation. While shelterin prevents the checkpoint kinases ATM and ATR from fully activating DNA damage responses at telomeres, those kinases are also required for telomere maintenance. In fission yeast, cells lacking both Tel1 (ATM ortholog) and Rad3 (ATR ortholog) fail to recruit telomerase to telomeres, and survive by circularizing chromosomes. However, the critical telomere substrate(s) of Tel1ATM/Rad3ATR remained unknown. Here, we show that Tel1ATM/Rad3ATR-dependent phosphorylation of the shelterin subunit Ccq1 on Thr93 is essential for telomerase association with telomeres. In addition, we show that the telomerase subunit Est1 interacts directly with the phosphorylated Thr93 of Ccq1 to ensure telomere maintenance. The shelterin subunits Taz1, Rap1 and Poz1 (previously established inhibitors of telomerase) were also found to negatively regulate Ccq1 phosphorylation. These findings establish Tel1ATM/Rad3ATR-dependent Ccq1 Thr93 phosphorylation as a critical regulator of telomere maintenance in fission yeast.
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Affiliation(s)
- Bettina A Moser
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA
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Creamer KM, Partridge JF. RITS-connecting transcription, RNA interference, and heterochromatin assembly in fission yeast. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 2:632-46. [PMID: 21823226 DOI: 10.1002/wrna.80] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In recent years, a bevy of evidence has been unearthed indicating that 'silent' heterochromatin is not as transcriptionally inert as once thought. In the unicellular yeast Schizosaccharomyces pombe, the processing of transcripts derived from centromeric repeats into homologous short interfering RNA (siRNA) is essential for the formation of centromeric heterochromatin. Deletion of genes required for siRNA biogenesis showed that core components of the canonical RNA interference (RNAi) pathway are essential for centromeric heterochromatin assembly as well as for centromere function. Subsequent purification of the RNA-induced initiation of transcriptional gene silencing (RITS) complex provided the critical link between siRNAs and heterochromatin assembly, with RITS acting as a physical bridge between noncoding RNA scaffolds and chromatin. Here, we review current understanding of how RITS promotes heterochromatin formation and how it participates in transcription-coupled silencing. WIREs RNA 2011 2 632-646 DOI: 10.1002/wrna.80 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Kevin M Creamer
- Integrated Program in Biomedical Sciences, University of Tennessee Health Science Center, Memphis, USA
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