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Vicars H, Karg T, Mills A, Sullivan W. Acentric chromosome congression and alignment on the metaphase plate via kinetochore-independent forces in Drosophila. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.14.567057. [PMID: 38798431 PMCID: PMC11118298 DOI: 10.1101/2023.11.14.567057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Chromosome congression and alignment on the metaphase plate involves lateral and microtubule plus-end interactions with the kinetochore. Here we take advantage of our ability to efficiently generate a GFP-marked acentric X chromosome fragment in Drosophila neuroblasts to identify forces acting on chromosome arms that drive congression and alignment. We find acentrics efficiently align on the metaphase plate, often more rapidly than kinetochore-bearing chromosomes. Unlike intact chromosomes, the paired sister acentrics oscillate as they move to and reside on the metaphase plate in a plane distinct and significantly further from the main mass of intact chromosomes. Consequently, at anaphase onset acentrics are oriented either parallel or perpendicular to the spindle. Parallel-oriented sisters separate by sliding while those oriented perpendicularly separate via unzipping. This oscillation, together with the fact that in monopolar spindles acentrics are rapidly shunted away from the poles, indicates that distributed plus-end directed forces are primarily responsible for acentric migration. This conclusion is supported by the observation that reduction of EB1 preferentially disrupts acentric alignment. In addition, reduction of Klp3a activity, a gene required for the establishment of pole-to-pole microtubules, preferentially disrupts acentric alignment. Taken together these studies suggest that plus-end forces mediated by the outer pole-to-pole microtubules are primarily responsible for acentric metaphase alignment. Surprisingly, we find that a small fraction of sister acentrics are anti-parallel aligned indicating that the kinetochore is required to ensure parallel alignment of sister chromatids. Finally, we find induction of acentric chromosome fragments results in a global reorganization of the congressed chromosomes into a torus configuration. Article Summary The kinetochore serves as a site for attaching microtubules and allows for successful alignment, separation, and segregation of replicated sister chromosomes during cell division. However, previous studies have revealed that sister chromosomes without kinetochores (acentrics) often align to the metaphase plate, undergo separation and segregation, and are properly transmitted to daughter cells. In this study, we discuss the forces acting on chromosomes, independent of the kinetochore, underlying their successful alignment in early mitosis.
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2
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Kanoh J. Subtelomeres: hotspots of genome variation. Genes Genet Syst 2023; 98:155-160. [PMID: 37648502 DOI: 10.1266/ggs.23-00049] [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] [Indexed: 09/01/2023] Open
Abstract
Eukaryotic cells contain multiple types of duplicated sequences. Typical examples are tandem repeat sequences including telomeres, centromeres, rDNA genes and transposable elements. Most of these sequences are unstable; thus, their copy numbers or sequences change rapidly in the course of evolution. In this review, I will describe roles of subtelomere regions, which are located adjacent to telomeres at chromosome ends, and recent discoveries about their sequence variation.
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Affiliation(s)
- Junko Kanoh
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo
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3
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Kuse R, Ishii K. Flexible Attachment and Detachment of Centromeres and Telomeres to and from Chromosomes. Biomolecules 2023; 13:1016. [PMID: 37371596 DOI: 10.3390/biom13061016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 06/15/2023] [Accepted: 06/18/2023] [Indexed: 06/29/2023] Open
Abstract
Accurate transmission of genomic information across multiple cell divisions and generations, without any losses or errors, is fundamental to all living organisms. To achieve this goal, eukaryotes devised chromosomes. Eukaryotic genomes are represented by multiple linear chromosomes in the nucleus, each carrying a centromere in the middle, a telomere at both ends, and multiple origins of replication along the chromosome arms. Although all three of these DNA elements are indispensable for chromosome function, centromeres and telomeres possess the potential to detach from the original chromosome and attach to new chromosomal positions, as evident from the events of telomere fusion, centromere inactivation, telomere healing, and neocentromere formation. These events seem to occur spontaneously in nature but have not yet been elucidated clearly, because they are relatively infrequent and sometimes detrimental. To address this issue, experimental setups have been developed using model organisms such as yeast. In this article, we review some of the key experiments that provide clues as to the extent to which these paradoxical and elusive features of chromosomally indispensable elements may become valuable in the natural context.
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Affiliation(s)
- Riku Kuse
- Laboratory of Chromosome Function and Regulation, Graduate School of Engineering, Kochi University of Technology, Kochi 782-8502, Japan
| | - Kojiro Ishii
- Laboratory of Chromosome Function and Regulation, Graduate School of Engineering, Kochi University of Technology, Kochi 782-8502, Japan
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4
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Everson KM, McGinnis RC, Burdine OP, Huddleston TR, Hylick TM, Keith AL, Moore SC, O’Brien AE, Vilardo AL, Krupa JJ. Disentangling morphology and genetics in two voles ( Microtus pennsylvanicus and M. ochrogaster) in a region of sympatry. J Mammal 2023; 104:532-545. [PMID: 37287702 PMCID: PMC10243968 DOI: 10.1093/jmammal/gyac119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 11/17/2022] [Indexed: 10/09/2023] Open
Abstract
Species in recent, rapid radiations can be difficult to distinguish from one another due to incomplete sorting of traits, insufficient time for novel morphologies to evolve, and elevated rates of hybridization and gene flow. The vole genus Microtus (58 spp.) is one such system where all three factors are likely at play. In the central United States, the prairie vole, Microtus ochrogaster, and the eastern meadow vole, M. pennsylvanicus, occur in sympatry and can be distinguished on the basis of molar cusp patterns but are known to be exceptionally difficult to distinguish using external morphological characters. Using a combination of morphometrics, pelage color analyses, and phylogenetics, we explored which traits are most effective for species identification and whether these same traits can be used to identify the subspecies M. o. ohionensis. While we were able to identify six traits that differed significantly between M. ochrogaster and M. pennsylvanicus, we also found substantial measurement overlap which limits the utility of these traits for species identification. The subspecies M. o. ohionensis was particularly difficult to distinguish from M. p. pennsylvanicus, and we did not find any evidence that this subspecies forms a distinct genetic clade. Furthermore, the full species M. ochrogaster and M. pennsylvanicus did not form reciprocal clades in phylogenetic analyses. We discuss several possible reasons for these patterns, including unrecognized variation in molar cusp patterns and/or localized hybridization. Overall, our results provide useful information that will aid in the identification of these species and subspecies in the future, and provides a case study of how genetics, morphometrics, and fur color analyses can be used to disentangle signatures of evolutionary history and hybridization.
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Affiliation(s)
- Kathryn M Everson
- Department of Biology, T.H. Morgan Building, University of Kentucky, 675 Rose Street, Lexington, Kentucky 40506, USA
| | - Robert C McGinnis
- Department of Biology, T.H. Morgan Building, University of Kentucky, 675 Rose Street, Lexington, Kentucky 40506, USA
| | - Olivia P Burdine
- Department of Biology, T.H. Morgan Building, University of Kentucky, 675 Rose Street, Lexington, Kentucky 40506, USA
| | - Taniece R Huddleston
- Department of Biology, T.H. Morgan Building, University of Kentucky, 675 Rose Street, Lexington, Kentucky 40506, USA
| | - Tyler M Hylick
- Department of Biology, T.H. Morgan Building, University of Kentucky, 675 Rose Street, Lexington, Kentucky 40506, USA
| | - Audrey L Keith
- Department of Biology, T.H. Morgan Building, University of Kentucky, 675 Rose Street, Lexington, Kentucky 40506, USA
| | - Savannah C Moore
- Department of Biology, T.H. Morgan Building, University of Kentucky, 675 Rose Street, Lexington, Kentucky 40506, USA
| | - Aidan E O’Brien
- Department of Biology, T.H. Morgan Building, University of Kentucky, 675 Rose Street, Lexington, Kentucky 40506, USA
| | - Ava L Vilardo
- Department of Biology, T.H. Morgan Building, University of Kentucky, 675 Rose Street, Lexington, Kentucky 40506, USA
| | - James J Krupa
- Department of Biology, T.H. Morgan Building, University of Kentucky, 675 Rose Street, Lexington, Kentucky 40506, USA
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5
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Kanoh J. Roles of Specialized Chromatin and DNA Structures at Subtelomeres in Schizosaccharomyces pombe. Biomolecules 2023; 13:biom13050810. [PMID: 37238680 DOI: 10.3390/biom13050810] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 04/28/2023] [Accepted: 05/02/2023] [Indexed: 05/28/2023] Open
Abstract
Eukaryotes have linear chromosomes with domains called telomeres at both ends. The telomere DNA consists of a simple tandem repeat sequence, and multiple telomere-binding proteins including the shelterin complex maintain chromosome-end structures and regulate various biological reactions, such as protection of chromosome ends and control of telomere DNA length. On the other hand, subtelomeres, which are located adjacent to telomeres, contain a complex mosaic of multiple common segmental sequences and a variety of gene sequences. This review focused on roles of the subtelomeric chromatin and DNA structures in the fission yeast Schizosaccharomyces pombe. The fission yeast subtelomeres form three distinct chromatin structures; one is the shelterin complex, which is localized not only at the telomeres but also at the telomere-proximal regions of subtelomeres to form transcriptionally repressive chromatin structures. The others are heterochromatin and knob, which have repressive effects in gene expression, but the subtelomeres are equipped with a mechanism that prevents these condensed chromatin structures from invading adjacent euchromatin regions. On the other hand, recombination reactions within or near subtelomeric sequences allow chromosomes to be circularized, enabling cells to survive in telomere shortening. Furthermore, DNA structures of the subtelomeres are more variable than other chromosomal regions, which may have contributed to biological diversity and evolution while changing gene expression and chromatin structures.
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Affiliation(s)
- Junko Kanoh
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
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6
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Kakui Y, Barrington C, Kusano Y, Thadani R, Fallesen T, Hirota T, Uhlmann F. Chromosome arm length, and a species-specific determinant, define chromosome arm width. Cell Rep 2022; 41:111753. [PMID: 36476849 DOI: 10.1016/j.celrep.2022.111753] [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: 04/20/2022] [Revised: 09/05/2022] [Accepted: 11/09/2022] [Indexed: 12/12/2022] Open
Abstract
Mitotic chromosomes in different organisms adopt various dimensions. What defines these dimensions is scarcely understood. Here, we compare mitotic chromosomes in budding and fission yeasts harboring similarly sized genomes distributed among 16 or 3 chromosomes, respectively. Hi-C analyses and superresolution microscopy reveal that budding yeast chromosomes are characterized by shorter-ranging mitotic chromatin contacts and are thinner compared with the thicker fission yeast chromosomes that contain longer-ranging mitotic contacts. These distinctions persist even after budding yeast chromosomes are fused to form three fission-yeast-length entities, revealing a species-specific organizing principle. Species-specific widths correlate with the known binding site intervals of the chromosomal condensin complex. Unexpectedly, within each species, we find that longer chromosome arms are always thicker and harbor longer-ranging contacts, a trend that we also observe with human chromosomes. Arm length as a chromosome width determinant informs mitotic chromosome formation models.
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Affiliation(s)
- Yasutaka Kakui
- Waseda Institute for Advanced Study, Waseda University, Tokyo 169-0051, Japan; Laboratory of Cytoskeletal Logistics, Center for Advanced Biomedical Sciences, Waseda University, Tokyo 162-8480, Japan; Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK.
| | - Christopher Barrington
- Bioinformatics & Biostatistics Science Technology Platform, The Francis Crick Institute, London NW1 1AT, UK
| | - Yoshiharu Kusano
- Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo 135-8550, Japan
| | - Rahul Thadani
- Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK
| | - Todd Fallesen
- Advanced Light Microscopy Science Technology Platform, The Francis Crick Institute, London NW1 1AT, UK
| | - Toru Hirota
- Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo 135-8550, Japan
| | - Frank Uhlmann
- Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK.
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Clay DE, Bretscher HS, Jezuit EA, Bush KB, Fox DT. Persistent DNA damage signaling and DNA polymerase theta promote broken chromosome segregation. J Cell Biol 2021; 220:e202106116. [PMID: 34613334 PMCID: PMC8500225 DOI: 10.1083/jcb.202106116] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 08/24/2021] [Accepted: 09/14/2021] [Indexed: 01/16/2023] Open
Abstract
Cycling cells must respond to DNA double-strand breaks (DSBs) to avoid genome instability. Missegregation of chromosomes with DSBs during mitosis results in micronuclei, aberrant structures linked to disease. How cells respond to DSBs during mitosis is incompletely understood. We previously showed that Drosophilamelanogaster papillar cells lack DSB checkpoints (as observed in many cancer cells). Here, we show that papillar cells still recruit early acting repair machinery (Mre11 and RPA3) and the Fanconi anemia (FA) protein Fancd2 to DSBs. These proteins persist as foci on DSBs as cells enter mitosis. Repair foci are resolved in a stepwise manner during mitosis. DSB repair kinetics depends on both monoubiquitination of Fancd2 and the alternative end-joining protein DNA polymerase θ. Disruption of either or both of these factors causes micronuclei after DNA damage, which disrupts intestinal organogenesis. This study reveals a mechanism for how cells with inactive DSB checkpoints can respond to DNA damage that persists into mitosis.
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Affiliation(s)
- Delisa E. Clay
- Department of Cell Biology, Duke University School of Medicine, Durham, NC
| | - Heidi S. Bretscher
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC
| | - Erin A. Jezuit
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC
| | - Korie B. Bush
- University Program in Genetics and Genomics, Duke University School of Medicine, Durham, NC
| | - Donald T. Fox
- Department of Cell Biology, Duke University School of Medicine, Durham, NC
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC
- University Program in Genetics and Genomics, Duke University School of Medicine, Durham, NC
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8
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Clay DE, Fox DT. DNA Damage Responses during the Cell Cycle: Insights from Model Organisms and Beyond. Genes (Basel) 2021; 12:1882. [PMID: 34946831 PMCID: PMC8701014 DOI: 10.3390/genes12121882] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 11/22/2021] [Accepted: 11/23/2021] [Indexed: 12/25/2022] Open
Abstract
Genome damage is a threat to all organisms. To respond to such damage, DNA damage responses (DDRs) lead to cell cycle arrest, DNA repair, and cell death. Many DDR components are highly conserved, whereas others have adapted to specific organismal needs. Immense progress in this field has been driven by model genetic organism research. This review has two main purposes. First, we provide a survey of model organism-based efforts to study DDRs. Second, we highlight how model organism study has contributed to understanding how specific DDRs are influenced by cell cycle stage. We also look forward, with a discussion of how future study can be expanded beyond typical model genetic organisms to further illuminate how the genome is protected.
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Affiliation(s)
- Delisa E. Clay
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710, USA;
| | - Donald T. Fox
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710, USA;
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA
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9
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Liolophura species discrimination with geographical distribution patterns and their divergence and expansion history on the northwestern Pacific coast. Sci Rep 2021; 11:17602. [PMID: 34475451 PMCID: PMC8413323 DOI: 10.1038/s41598-021-96823-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 08/17/2021] [Indexed: 11/18/2022] Open
Abstract
The chiton Liolophura japonica (Lischke 1873) is distributed in intertidal areas of the northwestern Pacific. Using COI and 16S rRNA, we found three genetic lineages, suggesting separation into three different species. Population genetic analyses, the two distinct COI barcoding gaps albeit one barcoding gap in the 16S rRNA, and phylogenetic relationships with a congeneric species supported this finding. We described L. koreana, sp. nov. over ca. 33°24′ N (JJ), and L. sinensis, sp. nov. around ca. 27°02′–28°00′ N (ZJ). We confirmed that these can be morphologically distinguished by lateral and dorsal black spots on the tegmentum and the shape of spicules on the perinotum. We also discuss species divergence during the Plio-Pleistocene, demographic expansions following the last interglacial age in the Pleistocene, and augmentation of COI haplotype diversity during the Pleistocene. Our study sheds light on the potential for COI in examining marine invertebrate species discrimination and distribution in the northwestern Pacific.
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Schotanus K, Yadav V, Heitman J. Epigenetic dynamics of centromeres and neocentromeres in Cryptococcus deuterogattii. PLoS Genet 2021; 17:e1009743. [PMID: 34464380 PMCID: PMC8407549 DOI: 10.1371/journal.pgen.1009743] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 07/26/2021] [Indexed: 11/25/2022] Open
Abstract
Deletion of native centromeres in the human fungal pathogen Cryptococcus deuterogattii leads to neocentromere formation. Native centromeres span truncated transposable elements, while neocentromeres do not and instead span actively expressed genes. To explore the epigenetic organization of neocentromeres, we analyzed the distribution of the heterochromatic histone modification H3K9me2, 5mC DNA methylation and the euchromatin mark H3K4me2. Native centromeres are enriched for both H3K9me2 and 5mC DNA methylation marks and are devoid of H3K4me2, while neocentromeres do not exhibit any of these features. Neocentromeres in cen10Δ mutants are unstable and chromosome-chromosome fusions occur. After chromosome fusion, the neocentromere is inactivated and the native centromere of the chromosome fusion partner remains as the sole, active centromere. In the present study, the active centromere of a fused chromosome was deleted to investigate if epigenetic memory promoted the re-activation of the inactive neocentromere. Our results show that the inactive neocentromere is not re-activated and instead a novel neocentromere forms directly adjacent to the deleted centromere of the fused chromosome. To study the impact of transcription on centromere stability, the actively expressed URA5 gene was introduced into the CENP-A bound regions of a native centromere. The introduction of the URA5 gene led to a loss of CENP-A from the native centromere, and a neocentromere formed adjacent to the native centromere location. Remarkably, the inactive, native centromere remained enriched for heterochromatin, yet the integrated gene was expressed and devoid of H3K9me2. A cumulative analysis of multiple CENP-A distribution profiles revealed centromere drift in C. deuterogattii, a previously unreported phenomenon in fungi. The CENP-A-binding shifted within the ORF-free regions and showed a possible association with a truncated transposable element. Taken together, our findings reveal that neocentromeres in C. deuterogattii are highly unstable and are not marked with an epigenetic memory, distinguishing them from native centromeres. Linear eukaryotic chromosomes require a specific chromosomal region, the centromere, where the macromolecular kinetochore protein complex assembles. In most organisms, centromeres are located in gene-free, repeat-rich chromosomal regions and may or may not be associated with heterochromatic epigenetic marks. We report that the native centromeres of the human fungal pathogen Cryptococcus deuterogattii are enriched with heterochromatin marks. Deleting a centromere in C. deuterogattii results in formation of neocentromeres that span genes. In some cases, neocentromeres are unstable leading to chromosome-chromosome fusions and neocentromere inactivation. These neocentromeres, unlike native centromeres, lack any of the tested heterochromatic marks or any epigenetic memory. We also found that neocentromere formation can be triggered not only by deletion of the native centromere but also by disrupting its function via insertion of a gene. These results show that neocentromere dynamics in this fungal pathogen are unique among organisms studied so far. Our results also revealed key differences between epigenetics of native centromeres between C. deuterogattii and its sister species, C. neoformans. These finding provide an opportunity to test and study the evolution of centromeres, as well as neocentromeres, in this species complex and how it might contribute to their genome evolution.
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Affiliation(s)
- Klaas Schotanus
- Duke University Medical Center, Durham, North Carolina, United States of America
| | - Vikas Yadav
- Duke University Medical Center, Durham, North Carolina, United States of America
| | - Joseph Heitman
- Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
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11
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Pobiega S, Alibert O, Marcand S. A new assay capturing chromosome fusions shows a protection trade-off at telomeres and NHEJ vulnerability to low-density ionizing radiation. Nucleic Acids Res 2021; 49:6817-6831. [PMID: 34125900 PMCID: PMC8266670 DOI: 10.1093/nar/gkab502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 03/31/2021] [Accepted: 05/27/2021] [Indexed: 11/14/2022] Open
Abstract
Chromosome fusions threaten genome integrity and promote cancer by engaging catastrophic mutational processes, namely chromosome breakage-fusion-bridge cycles and chromothripsis. Chromosome fusions are frequent in cells incurring telomere dysfunctions or those exposed to DNA breakage. Their occurrence and therefore their contribution to genome instability in unchallenged cells is unknown. To address this issue, we constructed a genetic assay able to capture and quantify rare chromosome fusions in budding yeast. This chromosome fusion capture (CFC) assay relies on the controlled inactivation of one centromere to rescue unstable dicentric chromosome fusions. It is sensitive enough to quantify the basal rate of end-to-end chromosome fusions occurring in wild-type cells. These fusions depend on canonical nonhomologous end joining (NHEJ). Our results show that chromosome end protection results from a trade-off at telomeres between positive effectors (Rif2, Sir4, telomerase) and a negative effector partially antagonizing them (Rif1). The CFC assay also captures NHEJ-dependent chromosome fusions induced by ionizing radiation. It provides evidence for chromosomal rearrangements stemming from a single photon-matter interaction.
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Affiliation(s)
- Sabrina Pobiega
- Université de Paris and Université Paris-Saclay, Inserm, CEA IBFJ/iRCM, UMR Stabilité Génétique Cellules Souches et Radiations, 92265 Fontenay-au-Roses, France
| | | | - Stéphane Marcand
- To whom correspondence should be addressed. Tel: +33 1 46 54 82 33;
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12
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Oizumi Y, Kaji T, Tashiro S, Takeshita Y, Date Y, Kanoh J. Complete sequences of Schizosaccharomyces pombe subtelomeres reveal multiple patterns of genome variation. Nat Commun 2021; 12:611. [PMID: 33504776 PMCID: PMC7840980 DOI: 10.1038/s41467-020-20595-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 12/03/2020] [Indexed: 12/20/2022] Open
Abstract
Genome sequences have been determined for many model organisms; however, repetitive regions such as centromeres, telomeres, and subtelomeres have not yet been sequenced completely. Here, we report the complete sequences of subtelomeric homologous (SH) regions of the fission yeast Schizosaccharomyces pombe. We overcame technical difficulties to obtain subtelomeric repetitive sequences by constructing strains that possess single SH regions of a standard laboratory strain. In addition, some natural isolates of S. pombe were analyzed using previous sequencing data. Whole sequences of SH regions revealed that each SH region consists of two distinct parts with mosaics of multiple common segments or blocks showing high variation among subtelomeres and strains. Subtelomere regions show relatively high frequency of nucleotide variations among strains compared with the other chromosomal regions. Furthermore, we identified subtelomeric RecQ-type helicase genes, tlh3 and tlh4, which add to the already known tlh1 and tlh2, and found that the tlh1-4 genes show high sequence variation with missense mutations, insertions, and deletions but no severe effects on their RNA expression. Our results indicate that SH sequences are highly polymorphic and hot spots for genome variation. These features of subtelomeres may have contributed to genome diversity and, conversely, various diseases.
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Affiliation(s)
- Yusuke Oizumi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Takuto Kaji
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Sanki Tashiro
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
- Institute of Molecular Biology, University of Oregon, 1370 Franklin Blvd, Eugene, OR, USA
| | - Yumiko Takeshita
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yuko Date
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan
| | - Junko Kanoh
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
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13
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Chen CC, Liu HY, Chen CW, Schneider H, Hyvönen J. On the spore ornamentation of the microsoroid ferns (microsoroideae, polypodiaceae). JOURNAL OF PLANT RESEARCH 2021; 134:55-76. [PMID: 33251557 PMCID: PMC7817562 DOI: 10.1007/s10265-020-01238-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 11/09/2020] [Indexed: 06/12/2023]
Abstract
Microsoroideae is the third largest of the six subfamilies of Polypodiaceae, containing over 180 species. These ferns are widely distributed in the tropical and subtropical regions of the Old World and Oceania. We documented the spore ornamentation and integrated these data into the latest phylogenetic hypotheses, including a sampling of 100 taxa representing each of 17 major lineages of microsoroid ferns. This enabled us to reconstruct the ancestral states of the spore morphology. The results show verrucate ornamentation as an ancestral state for Goniophlebieae and Lecanoptereae, globular for Microsoreae, and rugulate surface for Lepisoreae. In addition, spore ornamentation can be used to distinguish certain clades of the microsoroid ferns. Among all five tribes, Lecanoptereae show most diversity in spore surface ornamentation.
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Affiliation(s)
- Chi-Chuan Chen
- Organismal and Evolutionary Biology, Viikki Plant Science Center and Finnish Museum of Natural History (Botany), University of Helsinki, PO Box 7, 00100, Helsinki, FI, Finland
| | - Ho-Yih Liu
- Department of Biological Sciences, National Sun Yat-Sen University, 70 Lien-hai Rd, Kaohsiung, 804, Taiwan
| | | | - Harald Schneider
- Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Yunnan, China
| | - Jaakko Hyvönen
- Organismal and Evolutionary Biology, Viikki Plant Science Center and Finnish Museum of Natural History (Botany), University of Helsinki, PO Box 7, 00100, Helsinki, FI, Finland.
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14
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Vicars H, Karg T, Warecki B, Bast I, Sullivan W. Kinetochore-independent mechanisms of sister chromosome separation. PLoS Genet 2021; 17:e1009304. [PMID: 33513180 PMCID: PMC7886193 DOI: 10.1371/journal.pgen.1009304] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 02/16/2021] [Accepted: 12/08/2020] [Indexed: 11/19/2022] Open
Abstract
Although kinetochores normally play a key role in sister chromatid separation and segregation, chromosome fragments lacking kinetochores (acentrics) can in some cases separate and segregate successfully. In Drosophila neuroblasts, acentric chromosomes undergo delayed, but otherwise normal sister separation, revealing the existence of kinetochore- independent mechanisms driving sister chromosome separation. Bulk cohesin removal from the acentric is not delayed, suggesting factors other than cohesin are responsible for the delay in acentric sister separation. In contrast to intact kinetochore-bearing chromosomes, we discovered that acentrics align parallel as well as perpendicular to the mitotic spindle. In addition, sister acentrics undergo unconventional patterns of separation. For example, rather than the simultaneous separation of sisters, acentrics oriented parallel to the spindle often slide past one another toward opposing poles. To identify the mechanisms driving acentric separation, we screened 117 RNAi gene knockdowns for synthetic lethality with acentric chromosome fragments. In addition to well-established DNA repair and checkpoint mutants, this candidate screen identified synthetic lethality with X-chromosome-derived acentric fragments in knockdowns of Greatwall (cell cycle kinase), EB1 (microtubule plus-end tracking protein), and Map205 (microtubule-stabilizing protein). Additional image-based screening revealed that reductions in Topoisomerase II levels disrupted sister acentric separation. Intriguingly, live imaging revealed that knockdowns of EB1, Map205, and Greatwall preferentially disrupted the sliding mode of sister acentric separation. Based on our analysis of EB1 localization and knockdown phenotypes, we propose that in the absence of a kinetochore, microtubule plus-end dynamics provide the force to resolve DNA catenations required for sister separation.
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Affiliation(s)
- Hannah Vicars
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, California, United States of America
| | - Travis Karg
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, California, United States of America
| | - Brandt Warecki
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, California, United States of America
| | - Ian Bast
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, California, United States of America
| | - William Sullivan
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, California, United States of America
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15
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Warecki B, Sullivan W. Mechanisms driving acentric chromosome transmission. Chromosome Res 2020; 28:229-246. [PMID: 32712740 DOI: 10.1007/s10577-020-09636-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 07/16/2020] [Accepted: 07/19/2020] [Indexed: 02/07/2023]
Abstract
The kinetochore-microtubule association is a core, conserved event that drives chromosome transmission during mitosis. Failure to establish this association on even a single chromosome results in aneuploidy leading to cell death or the development of cancer. However, although many chromosomes lacking centromeres, termed acentrics, fail to segregate, studies in a number of systems reveal robust alternative mechanisms that can drive segregation and successful poleward transport of acentrics. In contrast to the canonical mechanism that relies on end-on microtubule attachments to kinetochores, mechanisms of acentric transmission largely fall into three categories: direct attachments to other chromosomes, kinetochore-independent lateral attachments to microtubules, and long-range tether-based attachments. Here, we review these "non-canonical" methods of acentric chromosome transmission. Just as the discovery and exploration of cell cycle checkpoints provided insight into both the origins of cancer and new therapies, identifying mechanisms and structures specifically involved in acentric segregation may have a significant impact on basic and applied cancer research.
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Affiliation(s)
- Brandt Warecki
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA, USA
| | - William Sullivan
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA, USA.
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16
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Schotanus K, Heitman J. Centromere deletion in Cryptococcus deuterogattii leads to neocentromere formation and chromosome fusions. eLife 2020; 9:56026. [PMID: 32310085 PMCID: PMC7188483 DOI: 10.7554/elife.56026] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 04/16/2020] [Indexed: 02/06/2023] Open
Abstract
The human fungal pathogen Cryptococcus deuterogattii is RNAi-deficient and lacks active transposons in its genome. C. deuterogattii has regional centromeres that contain only transposon relics. To investigate the impact of centromere loss on the C. deuterogattii genome, either centromere 9 or 10 was deleted. Deletion of either centromere resulted in neocentromere formation and interestingly, the genes covered by these neocentromeres maintained wild-type expression levels. In contrast to cen9∆ mutants, cen10∆ mutant strains exhibited growth defects and were aneuploid for chromosome 10. At an elevated growth temperature (37°C), the cen10∆ chromosome was found to have undergone fusion with another native chromosome in some isolates and this fusion restored wild-type growth. Following chromosomal fusion, the neocentromere was inactivated, and the native centromere of the fused chromosome served as the active centromere. The neocentromere formation and chromosomal fusion events observed in this study in C. deuterogattii may be similar to events that triggered genomic changes within the Cryptococcus/Kwoniella species complex and may contribute to speciation throughout the eukaryotic domain.
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Affiliation(s)
- Klaas Schotanus
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States
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17
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Begnis M, Apte MS, Masuda H, Jain D, Wheeler DL, Cooper JP. RNAi drives nonreciprocal translocations at eroding chromosome ends to establish telomere-free linear chromosomes. Genes Dev 2018; 32:537-554. [PMID: 29654060 PMCID: PMC5959237 DOI: 10.1101/gad.311712.118] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 03/29/2018] [Indexed: 12/19/2022]
Abstract
In this study, Begnis et al. show that HAATI, which is a mode of telomerase-minus survival in which canonical telomeres are superseded by blocks of nontelomeric rDNA heterochromatin that have spread to all chromosome ends, is formed and maintained. Their findings demonstrate that HAATI arises when telomere loss triggers a newly recognized illegitimate recombination pathway that requires RNAi factors, uncovering novel roles for ncRNAs in assembling a telomere-free chromosome end protection device. The identification of telomerase-negative HAATI (heterochromatin amplification-mediated and telomerase-independent) cells, in which telomeres are superseded by nontelomeric heterochromatin tracts, challenged the idea that canonical telomeres are essential for chromosome linearity and raised crucial questions as to how such tracts translocate to eroding chromosome ends and confer end protection. Here we show that HAATI arises when telomere loss triggers a newly recognized illegitimate translocation pathway that requires RNAi factors. While RNAi is necessary for the translocation events that mobilize ribosomal DNA (rDNA) tracts to all chromosome ends (forming “HAATIrDNA” chromosomes), it is dispensable for HAATIrDNA maintenance. Surprisingly, Dicer (Dcr1) plays a separate, RNAi-independent role in preventing formation of the rare HAATI subtype in which a different repetitive element (the subtelomeric element) replaces telomeres. Using genetics and fusions between shelterin components and rDNA-binding proteins, we mapped the mechanism by which rDNA loci engage crucial end protection factors—despite the absence of telomere repeats—and secure end protection. Sequence analysis of HAATIrDNA genomes allowed us to propose RNA and DNA polymerase template-switching models for the mechanism of RNAi-triggered rDNA translocations. Collectively, our results reveal unforeseen roles for noncoding RNAs (ncRNAs) in assembling a telomere-free chromosome end protection device.
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Affiliation(s)
- Martina Begnis
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.,Telomere Biology Laboratory, Cancer Research UK, London Research Institute, London WC2A 3LY, United Kingdom
| | - Manasi S Apte
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Hirohisa Masuda
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Devanshi Jain
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - David Lee Wheeler
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Julia Promisel Cooper
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.,Telomere Biology Laboratory, Cancer Research UK, London Research Institute, London WC2A 3LY, United Kingdom
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18
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Cleal K, Norris K, Baird D. Telomere Length Dynamics and the Evolution of Cancer Genome Architecture. Int J Mol Sci 2018; 19:E482. [PMID: 29415479 PMCID: PMC5855704 DOI: 10.3390/ijms19020482] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 01/29/2018] [Accepted: 01/31/2018] [Indexed: 02/06/2023] Open
Abstract
Telomeres are progressively eroded during repeated rounds of cell division due to the end replication problem but also undergo additional more substantial stochastic shortening events. In most cases, shortened telomeres induce a cell-cycle arrest or trigger apoptosis, although for those cells that bypass such signals during tumour progression, a critical length threshold is reached at which telomere dysfunction may ensue. Dysfunction of the telomere nucleoprotein complex can expose free chromosome ends to the DNA double-strand break (DSB) repair machinery, leading to telomere fusion with both telomeric and non-telomeric loci. The consequences of telomere fusions in promoting genome instability have long been appreciated through the breakage-fusion-bridge (BFB) cycle mechanism, although recent studies using high-throughput sequencing technologies have uncovered evidence of involvement in a wider spectrum of genomic rearrangements including chromothripsis. A critical step in cancer progression is the transition of a clone to immortality, through the stabilisation of the telomere repeat array. This can be achieved via the reactivation of telomerase, or the induction of the alternative lengthening of telomeres (ALT) pathway. Whilst telomere dysfunction may promote genome instability and tumour progression, by limiting the replicative potential of a cell and enforcing senescence, telomere shortening can act as a tumour suppressor mechanism. However, the burden of senescent cells has also been implicated as a driver of ageing and age-related pathology, and in the promotion of cancer through inflammatory signalling. Considering the critical role of telomere length in governing cancer biology, we review questions related to the prognostic value of studying the dynamics of telomere shortening and fusion, and discuss mechanisms and consequences of telomere-induced genome rearrangements.
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Affiliation(s)
- Kez Cleal
- Division of Cancer and Genetics, School of Medicine, UHW Main Building, Cardiff CF14 4XN, UK.
| | - Kevin Norris
- Division of Cancer and Genetics, School of Medicine, UHW Main Building, Cardiff CF14 4XN, UK.
| | - Duncan Baird
- Division of Cancer and Genetics, School of Medicine, UHW Main Building, Cardiff CF14 4XN, UK.
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19
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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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20
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Karg T, Elting MW, Vicars H, Dumont S, Sullivan W. The chromokinesin Klp3a and microtubules facilitate acentric chromosome segregation. J Cell Biol 2017; 216:1597-1608. [PMID: 28500183 PMCID: PMC5461011 DOI: 10.1083/jcb.201604079] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 02/03/2017] [Accepted: 04/07/2017] [Indexed: 11/23/2022] Open
Abstract
Although chromosome fragments lacking a centromere would be expected to show severe defects in their segregation during anaphase, they do exhibit poleward movement by an unclear mechanism. Karg et al. now show how microtubules and the chromokinesin Klp3a can work together to successfully segregate chromosome fragments to daughter nuclei. Although poleward segregation of acentric chromosomes is well documented, the underlying mechanisms remain poorly understood. Here, we demonstrate that microtubules play a key role in poleward movement of acentric chromosome fragments generated in Drosophila melanogaster neuroblasts. Acentrics segregate with either telomeres leading or lagging in equal frequency and are preferentially associated with peripheral bundled microtubules. In addition, laser ablation studies demonstrate that segregating acentrics are mechanically associated with microtubules. Finally, we show that successful acentric segregation requires the chromokinesin Klp3a. Reduced Klp3a function results in disorganized interpolar microtubules and shortened spindles. Normally, acentric poleward segregation occurs at the periphery of the spindle in association with interpolar microtubules. In klp3a mutants, acentrics fail to localize and segregate along the peripheral interpolar microtubules and are abnormally positioned in the spindle interior. These studies demonstrate an unsuspected role for interpolar microtubules in driving acentric segregation.
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Affiliation(s)
- Travis Karg
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Mary Williard Elting
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143
| | - Hannah Vicars
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Sophie Dumont
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143.,Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94143
| | - William Sullivan
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
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21
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Affiliation(s)
- Junko Kanoh
- Institute for Protein Research, Osaka University
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