1
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Bedet C, Quarato P, Palladino F, Cecere G, Robert VJ. The C. elegans SET1 histone methyltransferase SET-2 is not required for transgenerational memory of silencing. MICROPUBLICATION BIOLOGY 2024; 2024:10.17912/micropub.biology.001143. [PMID: 38808193 PMCID: PMC11130714 DOI: 10.17912/micropub.biology.001143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 03/22/2024] [Accepted: 05/09/2024] [Indexed: 05/30/2024]
Abstract
The SET-2 /SET1 histone H3K4 methyltransferase and RNAi pathway components are required to maintain fertility across generations in C. elegans . SET-2 preserves the germline transcriptional program transgenerationally, and RNAi pathways rely on small RNAs to establish and maintain transgenerational gene silencing. We investigated whether the functionality of RNAi-induced transgenerational silencing and the composition of pools of endogenous small RNA are affected by the absence of SET-2 . Our results suggest that defects in RNAi pathways are not responsible for the transcriptional misregulation observed in the absence of SET-2 .
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Affiliation(s)
- Cécile Bedet
- Ecole Normale Supérieure de Lyon, Laboratory of Biology and Modeling of the Cell, CNRS UMR5239, Inserm U1293, University Claude Bernard Lyon 1, 69007 Lyon, France Auvergne-Rhône-Alpes, France
| | - Piergiuseppe Quarato
- Mechanisms of Epigenetic Inheritance, Department of Developmental and Stem Cell Biology, Institut Pasteur, CNRS UMR3738, Paris, France
- Current address: San Raffaele Telethon Institute for Gene Therapy, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Francesca Palladino
- Ecole Normale Supérieure de Lyon, Laboratory of Biology and Modeling of the Cell, CNRS UMR5239, Inserm U1293, University Claude Bernard Lyon 1, 69007 Lyon, France Auvergne-Rhône-Alpes, France
| | - Germano Cecere
- Mechanisms of Epigenetic Inheritance, Department of Developmental and Stem Cell Biology, Institut Pasteur, CNRS UMR3738, Paris, France
| | - Valérie J Robert
- Ecole Normale Supérieure de Lyon, Laboratory of Biology and Modeling of the Cell, CNRS UMR5239, Inserm U1293, University Claude Bernard Lyon 1, 69007 Lyon, France Auvergne-Rhône-Alpes, France
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2
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Mota APZ, Koutsovoulos GD, Perfus-Barbeoch L, Despot-Slade E, Labadie K, Aury JM, Robbe-Sermesant K, Bailly-Bechet M, Belser C, Péré A, Rancurel C, Kozlowski DK, Hassanaly-Goulamhoussen R, Da Rocha M, Noel B, Meštrović N, Wincker P, Danchin EGJ. Unzipped genome assemblies of polyploid root-knot nematodes reveal unusual and clade-specific telomeric repeats. Nat Commun 2024; 15:773. [PMID: 38316773 PMCID: PMC10844300 DOI: 10.1038/s41467-024-44914-y] [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: 04/20/2023] [Accepted: 01/09/2024] [Indexed: 02/07/2024] Open
Abstract
Using long-read sequencing, we assembled and unzipped the polyploid genomes of Meloidogyne incognita, M. javanica and M. arenaria, three of the most devastating plant-parasitic nematodes. We found the canonical nematode telomeric repeat to be missing in these and other Meloidogyne genomes. In addition, we find no evidence for the enzyme telomerase or for orthologs of C. elegans telomere-associated proteins, suggesting alternative lengthening of telomeres. Instead, analyzing our assembled genomes, we identify species-specific composite repeats enriched mostly at one extremity of contigs. These repeats are G-rich, oriented, and transcribed, similarly to canonical telomeric repeats. We confirm them as telomeric using fluorescent in situ hybridization. These repeats are mostly found at one single end of chromosomes in these species. The discovery of unusual and specific complex telomeric repeats opens a plethora of perspectives and highlights the evolutionary diversity of telomeres despite their central roles in senescence, aging, and chromosome integrity.
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Affiliation(s)
- Ana Paula Zotta Mota
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France.
| | - Georgios D Koutsovoulos
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France
| | - Laetitia Perfus-Barbeoch
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France
| | - Evelin Despot-Slade
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000, Zagreb, Croatia
| | - Karine Labadie
- Genoscope, Institut François Jacob, CEA, CNRS, Univ Evry, Université Paris-Saclay, 91057, Evry, France
| | - Jean-Marc Aury
- Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, Univ Evry, Université Paris-Saclay, 91057, Evry, France
| | - Karine Robbe-Sermesant
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France
| | - Marc Bailly-Bechet
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France
| | - Caroline Belser
- Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, Univ Evry, Université Paris-Saclay, 91057, Evry, France
| | - Arthur Péré
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France
| | - Corinne Rancurel
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France
| | - Djampa K Kozlowski
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France
- Université Côte d'Azur, Center of Modeling, Simulation, and Interactions, 28 Avenue Valrose, 06000, Nice, France
| | - Rahim Hassanaly-Goulamhoussen
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France
| | - Martine Da Rocha
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France
| | - Benjamin Noel
- Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, Univ Evry, Université Paris-Saclay, 91057, Evry, France
| | - Nevenka Meštrović
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000, Zagreb, Croatia
| | - Patrick Wincker
- Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, Univ Evry, Université Paris-Saclay, 91057, Evry, France
| | - Etienne G J Danchin
- Institut Sophia Agrobiotech, INRAE, Université Côte d'Azur, CNRS, 400 routes des Chappes, 06903, Sophia-Antipolis, France.
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3
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Lim J, Kim W, Kim J, Lee J. Telomeric repeat evolution in the phylum Nematoda revealed by high-quality genome assemblies and subtelomere structures. Genome Res 2023; 33:gr.278124.123. [PMID: 37918961 PMCID: PMC10760449 DOI: 10.1101/gr.278124.123] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 10/16/2023] [Indexed: 11/04/2023]
Abstract
Telomeres are composed of tandem arrays of telomeric-repeat motifs (TRMs) and telomere-binding proteins (TBPs), which are responsible for ensuring end-protection and end-replication of chromosomes. TRMs are highly conserved owing to the sequence specificity of TBPs, although significant alterations in TRM have been observed in several taxa, except Nematoda. We used public whole-genome sequencing data sets to analyze putative TRMs of 100 nematode species and determined that three distinct branches included specific novel TRMs, suggesting that evolutionary alterations in TRMs occurred in Nematoda. We focused on one of the three branches, the Panagrolaimidae family, and performed a de novo assembly of four high-quality draft genomes of the canonical (TTAGGC) and novel TRM (TTAGAC) isolates; the latter genomes revealed densely clustered arrays of the novel TRM. We then comprehensively analyzed the subtelomeric regions of the genomes to infer how the novel TRM evolved. We identified DNA damage-repair signatures in subtelomeric sequences that were representative of consequences of telomere maintenance mechanisms by alternative lengthening of telomeres. We propose a hypothetical scenario in which TTAGAC-containing units are clustered in subtelomeric regions and pre-existing TBPs capable of binding both canonical and novel TRMs aided the evolution of the novel TRM in the Panagrolaimidae family.
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Affiliation(s)
- Jiseon Lim
- Department of Biological Sciences, Seoul National University, Gwanak-gu, Seoul 08826, South Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Seoul 08826, South Korea
| | - Wonjoo Kim
- Department of Biological Sciences, Seoul National University, Gwanak-gu, Seoul 08826, South Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Seoul 08826, South Korea
| | - Jun Kim
- Department of Biological Sciences, Seoul National University, Gwanak-gu, Seoul 08826, South Korea;
- Research Institute of Basic Sciences, Seoul National University, Seoul 08826, South Korea
- Department of Convergent Bioscience and Informatics, College of Bioscience and Biotechnology, Chungnam National University, Daejeon 34134, South Korea
| | - Junho Lee
- Department of Biological Sciences, Seoul National University, Gwanak-gu, Seoul 08826, South Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Seoul 08826, South Korea
- Research Institute of Basic Sciences, Seoul National University, Seoul 08826, South Korea
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4
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Manzato C, Larini L, Oss Pegorar C, Dello Stritto MR, Jurikova K, Jantsch V, Cusanelli E. TERRA expression is regulated by the telomere-binding proteins POT-1 and POT-2 in Caenorhabditis elegans. Nucleic Acids Res 2023; 51:10681-10699. [PMID: 37713629 PMCID: PMC10602879 DOI: 10.1093/nar/gkad742] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 08/23/2023] [Accepted: 08/31/2023] [Indexed: 09/17/2023] Open
Abstract
Several aspects of telomere biology are regulated by the telomeric repeat-containing RNA TERRA. While TERRA expression is conserved through evolution, species-specific mechanisms regulate its biogenesis and function. Here we report on the expression of TERRA in Caenorhabditis elegans. We show that C. elegans TERRA is regulated by the telomere-binding proteins POT-1 and POT-2 which repress TERRA in a telomere-specific manner. C. elegans TERRA transcripts are heterogeneous in length and form discrete nuclear foci, as detected by RNA FISH, in both postmitotic and germline cells; a fraction of TERRA foci localizes to telomeres. Interestingly, in germ cells, TERRA is expressed in all stages of meiotic prophase I, and it increases during pachytene, a stage in meiosis when homologous recombination is ongoing. We used the MS2-GFP system to study the spatiotemporal dynamics of single-telomere TERRA molecules. Single particle tracking revealed different types of motilities, suggesting complex dynamics of TERRA transcripts. Finally, we unveiled distinctive features of C. elegans TERRA, which is regulated by telomere shortening in a telomere-specific manner, and it is upregulated in the telomerase-deficient trt-1; pot-2 double mutant prior to activation of the alternative lengthening mechanism ALT. Interestingly, in these worms TERRA displays distinct dynamics with a higher fraction of fast-moving particles.
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Affiliation(s)
- Caterina Manzato
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, 38123, Trento, Italy
| | - Luca Larini
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, 38123, Trento, Italy
| | - Claudio Oss Pegorar
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, 38123, Trento, Italy
| | - Maria Rosaria Dello Stritto
- Department of Chromosome Biology, Max Perutz Laboratories, University of Vienna, Vienna Biocenter 1030, Vienna, Austria
| | - Katarina Jurikova
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, 38123, Trento, Italy
- Department of Genetics, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, Mlynská dolina 84215, Bratislava, Slovakia
| | - Verena Jantsch
- Department of Chromosome Biology, Max Perutz Laboratories, University of Vienna, Vienna Biocenter 1030, Vienna, Austria
| | - Emilio Cusanelli
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, 38123, Trento, Italy
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5
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Yu X, Gray S, Ferreira H. POT-3 preferentially binds the terminal DNA-repeat on the telomeric G-overhang. Nucleic Acids Res 2023; 51:610-618. [PMID: 36583365 PMCID: PMC9881156 DOI: 10.1093/nar/gkac1203] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 12/01/2022] [Accepted: 12/06/2022] [Indexed: 12/31/2022] Open
Abstract
Eukaryotic chromosomes typically end in 3' telomeric overhangs. The safeguarding of telomeric single-stranded DNA overhangs is carried out by factors related to the protection of telomeres 1 (POT1) protein in humans. Of the three POT1-like proteins in Caenorhabditis elegans, POT-3 was the only member thought to not play a role at telomeres. Here, we provide evidence that POT-3 is a bona fide telomere-binding protein. Using a new loss-of-function mutant, we show that the absence of POT-3 causes telomere lengthening and increased levels of telomeric C-circles. We find that POT-3 directly binds the telomeric G-strand in vitro and map its minimal DNA binding site to the six-nucleotide motif, GCTTAG. We further show that the closely related POT-2 protein binds the same motif, but that POT-3 shows higher sequence selectivity. Crucially, in contrast to POT-2, POT-3 prefers binding sites immediately adjacent to the 3' end of DNA. These differences are significant as genetic analyses reveal that pot-2 and pot-3 do not function redundantly with each other in vivo. Our work highlights the rapid evolution and specialisation of telomere binding proteins and places POT-3 in a unique position to influence activities that control telomere length.
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Affiliation(s)
- Xupeng Yu
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, North Haugh, St Andrews, UK
| | - Sean Gray
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, North Haugh, St Andrews, UK
| | - Helder C Ferreira
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, North Haugh, St Andrews, UK
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6
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Abstract
The nematode Caenorhabditis elegans has shed light on many aspects of eukaryotic biology, including genetics, development, cell biology, and genomics. A major factor in the success of C. elegans as a model organism has been the availability, since the late 1990s, of an essentially gap-free and well-annotated nuclear genome sequence, divided among 6 chromosomes. In this review, we discuss the structure, function, and biology of C. elegans chromosomes and then provide a general perspective on chromosome biology in other diverse nematode species. We highlight malleable chromosome features including centromeres, telomeres, and repetitive elements, as well as the remarkable process of programmed DNA elimination (historically described as chromatin diminution) that induces loss of portions of the genome in somatic cells of a handful of nematode species. An exciting future prospect is that nematode species may enable experimental approaches to study chromosome features and to test models of chromosome evolution. In the long term, fundamental insights regarding how speciation is integrated with chromosome biology may be revealed.
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Affiliation(s)
- Peter M Carlton
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Richard E Davis
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Denver, CO 80045, USA.,RNA Bioscience Initiative, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Shawn Ahmed
- Department of Genetics, University of North Carolina, Chapel Hill, NC 27599, USA.,Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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7
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Genetic and Epigenetic Inheritance at Telomeres. EPIGENOMES 2022; 6:epigenomes6010009. [PMID: 35323213 PMCID: PMC8947350 DOI: 10.3390/epigenomes6010009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 02/21/2022] [Accepted: 03/08/2022] [Indexed: 12/17/2022] Open
Abstract
Transgenerational inheritance can occur at telomeres in distinct contexts. Deficiency for telomerase or telomere-binding proteins in germ cells can result in shortened or lengthened chromosome termini that are transmitted to progeny. In human families, altered telomere lengths can result in stem cell dysfunction or tumor development. Genetic inheritance of altered telomeres as well as mutations that alter telomeres can result in progressive telomere length changes over multiple generations. Telomeres of yeast can modulate the epigenetic state of subtelomeric genes in a manner that is mitotically heritable, and the effects of telomeres on subtelomeric gene expression may be relevant to senescence or other human adult-onset disorders. Recently, two novel epigenetic states were shown to occur at C. elegans telomeres, where very low or high levels of telomeric protein foci can be inherited for multiple generations through a process that is regulated by histone methylation.Together, these observations illustrate that information relevant to telomere biology can be inherited via genetic and epigenetic mechanisms, although the broad impact of epigenetic inheritance to human biology remains unclear.
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8
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The double-stranded DNA-binding proteins TEBP-1 and TEBP-2 form a telomeric complex with POT-1. Nat Commun 2021; 12:2668. [PMID: 33976151 PMCID: PMC8113555 DOI: 10.1038/s41467-021-22861-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 03/30/2021] [Indexed: 02/03/2023] Open
Abstract
Telomeres are bound by dedicated proteins, which protect them from DNA damage and regulate telomere length homeostasis. In the nematode Caenorhabditis elegans, a comprehensive understanding of the proteins interacting with the telomere sequence is lacking. Here, we harnessed a quantitative proteomics approach to identify TEBP-1 and TEBP-2, two paralogs expressed in the germline and embryogenesis that associate to telomeres in vitro and in vivo. tebp-1 and tebp-2 mutants display strikingly distinct phenotypes: tebp-1 mutants have longer telomeres than wild-type animals, while tebp-2 mutants display shorter telomeres and a Mortal Germline. Notably, tebp-1;tebp-2 double mutant animals have synthetic sterility, with germlines showing signs of severe mitotic and meiotic arrest. Furthermore, we show that POT-1 forms a telomeric complex with TEBP-1 and TEBP-2, which bridges TEBP-1/-2 with POT-2/MRT-1. These results provide insights into the composition and organization of a telomeric protein complex in C. elegans.
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9
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Spichal M, Heestand B, Billmyre KK, Frenk S, Mello CC, Ahmed S. Germ granule dysfunction is a hallmark and mirror of Piwi mutant sterility. Nat Commun 2021; 12:1420. [PMID: 33658512 PMCID: PMC7930041 DOI: 10.1038/s41467-021-21635-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 01/29/2021] [Indexed: 01/31/2023] Open
Abstract
In several species, Piwi/piRNA genome silencing defects cause immediate sterility that correlates with transposon expression and transposon-induced genomic instability. In C. elegans, mutations in the Piwi-related gene (prg-1) and other piRNA deficient mutants cause a transgenerational decline in fertility over a period of several generations. Here we show that the sterility of late generation piRNA mutants correlates poorly with increases in DNA damage signaling. Instead, sterile individuals consistently exhibit altered perinuclear germ granules. We show that disruption of germ granules does not activate transposon expression but induces multiple phenotypes found in sterile prg-1 pathway mutants. Furthermore, loss of the germ granule component pgl-1 enhances prg-1 mutant infertility. Environmental restoration of germ granule function for sterile pgl-1 mutants restores their fertility. We propose that Piwi mutant sterility is a reproductive arrest phenotype that is characterized by perturbed germ granule structure and is phenocopied by germ granule dysfunction, independent of genomic instability.
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Affiliation(s)
- Maya Spichal
- grid.410711.20000 0001 1034 1720Department of Genetics, University of North Carolina, Chapel Hill, NC USA ,grid.410711.20000 0001 1034 1720Department of Biology, University of North Carolina, Chapel Hill, NC USA ,grid.168645.80000 0001 0742 0364RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA USA
| | - Bree Heestand
- grid.410711.20000 0001 1034 1720Department of Genetics, University of North Carolina, Chapel Hill, NC USA ,grid.410711.20000 0001 1034 1720Department of Biology, University of North Carolina, Chapel Hill, NC USA
| | - Katherine Kretovich Billmyre
- grid.410711.20000 0001 1034 1720Department of Genetics, University of North Carolina, Chapel Hill, NC USA ,grid.410711.20000 0001 1034 1720Department of Biology, University of North Carolina, Chapel Hill, NC USA ,grid.250820.d0000 0000 9420 1591Present Address: Stowers Institute for Medical Research, Kansas City, MO USA
| | - Stephen Frenk
- grid.410711.20000 0001 1034 1720Department of Genetics, University of North Carolina, Chapel Hill, NC USA ,grid.410711.20000 0001 1034 1720Department of Biology, University of North Carolina, Chapel Hill, NC USA ,Present Address: Achilles Therapeutics Limited, London, UK
| | - Craig C. Mello
- grid.168645.80000 0001 0742 0364RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA USA ,grid.413575.10000 0001 2167 1581Howard Hughes Medical Institute, Worcester, MA USA
| | - Shawn Ahmed
- grid.410711.20000 0001 1034 1720Department of Genetics, University of North Carolina, Chapel Hill, NC USA ,grid.410711.20000 0001 1034 1720Department of Biology, University of North Carolina, Chapel Hill, NC USA ,grid.410711.20000 0001 1034 1720Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC USA
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10
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Gartner A, Engebrecht J. DNA repair, recombination, and damage signaling. Genetics 2021; 220:6522877. [PMID: 35137093 PMCID: PMC9097270 DOI: 10.1093/genetics/iyab178] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 10/10/2021] [Indexed: 01/09/2023] Open
Abstract
DNA must be accurately copied and propagated from one cell division to the next, and from one generation to the next. To ensure the faithful transmission of the genome, a plethora of distinct as well as overlapping DNA repair and recombination pathways have evolved. These pathways repair a large variety of lesions, including alterations to single nucleotides and DNA single and double-strand breaks, that are generated as a consequence of normal cellular function or by external DNA damaging agents. In addition to the proteins that mediate DNA repair, checkpoint pathways have also evolved to monitor the genome and coordinate the action of various repair pathways. Checkpoints facilitate repair by mediating a transient cell cycle arrest, or through initiation of cell suicide if DNA damage has overwhelmed repair capacity. In this chapter, we describe the attributes of Caenorhabditis elegans that facilitate analyses of DNA repair, recombination, and checkpoint signaling in the context of a whole animal. We review the current knowledge of C. elegans DNA repair, recombination, and DNA damage response pathways, and their role during development, growth, and in the germ line. We also discuss how the analysis of mutational signatures in C. elegans is helping to inform cancer mutational signatures in humans.
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Affiliation(s)
- Anton Gartner
- Department for Biological Sciences, IBS Center for Genomic Integrity, Ulsan National Institute of Science and Technology, Ulsan 689-798, Republic of Korea,Corresponding author: (A.G.); (J.E.)
| | - JoAnne Engebrecht
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA 95616, USA,Corresponding author: (A.G.); (J.E.)
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11
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Lister-Shimauchi EH, Dinh M, Maddox P, Ahmed S. Gametes deficient for Pot1 telomere binding proteins alter levels of telomeric foci for multiple generations. Commun Biol 2021; 4:158. [PMID: 33542458 PMCID: PMC7862594 DOI: 10.1038/s42003-020-01624-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 12/15/2020] [Indexed: 11/20/2022] Open
Abstract
Deficiency for telomerase results in transgenerational shortening of telomeres. However, telomeres have no known role in transgenerational epigenetic inheritance. C. elegans Protection Of Telomeres 1 (Pot1) proteins form foci at the telomeres of germ cells that disappear at fertilization and gradually accumulate during development. We find that gametes from mutants deficient for Pot1 proteins alter levels of telomeric foci for multiple generations. Gametes from pot-2 mutants give rise to progeny with abundant POT-1::mCherry and mNeonGreen::POT-2 foci throughout development, which persists for six generations. In contrast, gametes from pot-1 mutants or pot-1; pot-2 double mutants induce diminished Pot1 foci for several generations. Deficiency for MET-2, SET-25, or SET-32 methyltransferases, which promote heterochromatin formation, results in gametes that induce diminished Pot1 foci for several generations. We propose that C. elegans POT-1 may interact with H3K9 methyltransferases during pot-2 mutant gametogenesis to induce a persistent form of transgenerational epigenetic inheritance that causes constitutively high levels of heterochromatic Pot1 foci.
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Affiliation(s)
- Evan H Lister-Shimauchi
- Department of Genetics, University of North Carolina, Chapel Hill, NC, 27599, USA.
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA.
| | - Michael Dinh
- Department of Genetics, University of North Carolina, Chapel Hill, NC, 27599, USA
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Paul Maddox
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Shawn Ahmed
- Department of Genetics, University of North Carolina, Chapel Hill, NC, 27599, USA.
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA.
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, USA.
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, 27599, USA.
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12
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Yamamoto I, Zhang K, Zhang J, Vorontsov E, Shibuya H. Telomeric double-strand DNA-binding proteins DTN-1 and DTN-2 ensure germline immortality in Caenorhabditis elegans. eLife 2021; 10:64104. [PMID: 33476260 PMCID: PMC7819708 DOI: 10.7554/elife.64104] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 01/14/2021] [Indexed: 12/31/2022] Open
Abstract
Telomeres are nucleoprotein complexes at the ends of chromosomes and are indispensable for the protection and lengthening of terminal DNA. Despite the evolutionarily conserved roles of telomeres, the telomeric double-strand DNA (dsDNA)-binding proteins have evolved rapidly. Here, we identified double-strand telomeric DNA-binding proteins (DTN-1 and DTN-2) in Caenorhabditis elegans as non-canonical telomeric dsDNA-binding proteins. DTN-1 and DTN-2 are paralogous proteins that have three putative MYB-like DNA-binding domains and bind to telomeric dsDNA in a sequence-specific manner. DTN-1 and DTN-2 form complexes with the single-strand telomeric DNA-binding proteins POT-1 and POT-2 and constitutively localize to telomeres. The dtn-1 and dtn-2 genes function redundantly, and their simultaneous deletion results in progressive germline mortality, which accompanies telomere hyper-elongation and chromosomal bridges. Our study suggests that DTN-1 and DTN-2 are core shelterin components in C. elegans telomeres that act as negative regulators of telomere length and are essential for germline immortality.
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Affiliation(s)
- Io Yamamoto
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
| | - Kexin Zhang
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
| | - Jingjing Zhang
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
| | - Egor Vorontsov
- Proteomics Core Facility, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Hiroki Shibuya
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
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13
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Harnessing the power of genetics: fast forward genetics in Caenorhabditis elegans. Mol Genet Genomics 2020; 296:1-20. [PMID: 32888055 DOI: 10.1007/s00438-020-01721-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Accepted: 08/27/2020] [Indexed: 12/23/2022]
Abstract
Forward genetics is a powerful tool to unravel molecular mechanisms of diverse biological processes. The success of genetic screens primarily relies on the ease of genetic manipulation of an organism and the availability of a plethora of genetic tools. The roundworm Caenorhabditis elegans has been one of the favorite models for genetic studies due to its hermaphroditic lifestyle, ease of maintenance, and availability of various genetic manipulation tools. The strength of C. elegans genetics is highlighted by the leading role of this organism in the discovery of several conserved biological processes. In this review, the principles and strategies for forward genetics in C. elegans are discussed. Further, the recent advancements that have drastically accelerated the otherwise time-consuming process of mutation identification, making forward genetic screens a method of choice for understanding biological functions, are discussed. The emphasis of the review has been on providing practical and conceptual pointers for designing genetic screens that will identify mutations, specifically disrupting the biological processes of interest.
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14
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Barbero Barcenilla B, Shippen DE. Back to the future: The intimate and evolving connection between telomere-related factors and genotoxic stress. J Biol Chem 2019; 294:14803-14813. [PMID: 31434740 DOI: 10.1074/jbc.aw119.008145] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The conversion of circular genomes to linear chromosomes during molecular evolution required the invention of telomeres. This entailed the acquisition of factors necessary to fulfill two new requirements: the need to fully replicate terminal DNA sequences and the ability to distinguish chromosome ends from damaged DNA. Here we consider the multifaceted functions of factors recruited to perpetuate and stabilize telomeres. We discuss recent theories for how telomere factors evolved from existing cellular machineries and examine their engagement in nontelomeric functions such as DNA repair, replication, and transcriptional regulation. We highlight the remarkable versatility of protection of telomeres 1 (POT1) proteins that was fueled by gene duplication and divergence events that occurred independently across several eukaryotic lineages. Finally, we consider the relationship between oxidative stress and telomeres and the enigmatic role of telomere-associated proteins in mitochondria. These findings point to an evolving and intimate connection between telomeres and cellular physiology and the strong drive to maintain chromosome integrity.
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Affiliation(s)
- Borja Barbero Barcenilla
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128
| | - Dorothy E Shippen
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128
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15
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Kobayashi CR, Castillo-González C, Survotseva Y, Canal E, Nelson ADL, Shippen DE. Recent emergence and extinction of the protection of telomeres 1c gene in Arabidopsis thaliana. PLANT CELL REPORTS 2019; 38:1081-1097. [PMID: 31134349 PMCID: PMC6708462 DOI: 10.1007/s00299-019-02427-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 03/27/2019] [Indexed: 05/20/2023]
Abstract
Duplicate POT1 genes must rapidly diverge or be inactivated. Protection of telomeres 1 (POT1) encodes a conserved telomere binding protein implicated in both chromosome end protection and telomere length maintenance. Most organisms harbor a single POT1 gene, but in the few lineages where the POT1 family has expanded, the duplicate genes have diversified. Arabidopsis thaliana bears three POT1-like loci, POT1a, POT1b and POT1c. POT1a retains the ancestral function of telomerase regulation, while POT1b is implicated in chromosome end protection. Here we examine the function and evolution of the third POT1 paralog, POT1c. POT1c is a new gene, unique to A. thaliana, and was derived from a duplication event involving the POT1a locus and a neighboring gene encoding ribosomal protein S17. The duplicate S17 locus (dS17) is highly conserved across A. thaliana accessions, while POT1c is highly divergent, harboring multiple deletions within the gene body and two transposable elements within the promoter. The POT1c locus is transcribed at very low to non-detectable levels under standard growth conditions. In addition, no discernable molecular or developmental defects are associated with plants bearing a CRISPR mutation in the POT1c locus. However, forced expression of POT1c leads to decreased telomerase enzyme activity and shortened telomeres. Evolutionary reconstruction indicates that transposons invaded the POT1c promoter soon after the locus was formed, permanently silencing the gene. Altogether, these findings argue that POT1 dosage is critically important for viability and duplicate gene copies are retained only upon functional divergence.
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Affiliation(s)
- Callie R Kobayashi
- Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | | | - Yulia Survotseva
- Yale Center for Molecular Discovery, Yale University, New Haven, Connecticut, USA
| | - Elijah Canal
- Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Andrew D L Nelson
- The School of Plant Sciences, University of Arizona, Tucson, Arizona, USA
| | - Dorothy E Shippen
- Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA.
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16
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Frenk S, Lister-Shimauchi EH, Ahmed S. Telomeric small RNAs in the genus Caenorhabditis. RNA (NEW YORK, N.Y.) 2019; 25:1061-1077. [PMID: 31239299 PMCID: PMC6800518 DOI: 10.1261/rna.071324.119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 05/28/2019] [Indexed: 06/09/2023]
Abstract
Telomeric DNA is composed of simple tandem repeat sequences and has a G-rich strand that runs 5' to 3' toward the chromosome terminus. Small RNAs with homology to telomeres have been observed in several organisms and could originate from telomeres or from interstitial telomere sequences (ITSs), which are composites of degenerate and perfect telomere repeat sequences found on chromosome arms. We identified Caenorhabditis elegans small RNAs composed of the Caenorhabditis telomere sequence (TTAGGC)n with up to three mismatches, which might interact with telomeres. We rigorously defined ITSs for genomes of C. elegans and for two closely related nematodes, Caenorhabditis briggsae and Caenorhabditis remanei Most telomeric small RNAs with mismatches originated from ITSs, which were depleted from mRNAs but were enriched in introns whose genes often displayed hallmarks of genomic silencing. C. elegans small RNAs composed of perfect telomere repeats were very rare but their levels increased by several orders of magnitude in C. briggsae and C. remanei Major small RNA species in C. elegans begin with a 5' guanine nucleotide, which was strongly depleted from perfect telomeric small RNAs of all three Caenorhabditis species. Perfect G-rich or C-rich telomeric small RNAs commonly began with 5' UAGGCU and 5' UUAGGC or 5' CUAAGC, respectively. In contrast, telomeric small RNAs with mismatches had a mixture of all four 5' nucleotides. We suggest that perfect telomeric small RNAs have a mechanism of biogenesis that is distinct from known classes of small RNAs and that a dramatic change in their regulation occurred during recent Caenorhabditis evolution.
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Affiliation(s)
- Stephen Frenk
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
| | - Evan H Lister-Shimauchi
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
| | - Shawn Ahmed
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
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17
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Weiser NE, Kim JK. Multigenerational Regulation of the Caenorhabditis elegans Chromatin Landscape by Germline Small RNAs. Annu Rev Genet 2019; 53:289-311. [PMID: 31150586 DOI: 10.1146/annurev-genet-112618-043505] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In animals, small noncoding RNAs that are expressed in the germline and transmitted to progeny control gene expression to promote fertility. Germline-expressed small RNAs, including endogenous small interfering RNAs (endo-siRNAs) and Piwi-interacting RNAs (piRNAs), drive the repression of deleterious transcripts such as transposons, repetitive elements, and pseudogenes. Recent studies have highlighted an important role for small RNAs in transgenerational epigenetic inheritance via regulation of heritable chromatin marks; therefore, small RNAs are thought to convey an epigenetic memory of genomic self and nonself elements. Small RNA pathways are highly conserved in metazoans and have been best described for the model organism Caenorhabditis elegans. In this review, we describe the biogenesis, regulation, and function of C. elegans endo-siRNAs and piRNAs, along with recent insights into how these distinct pathways are integrated to collectively regulate germline gene expression, transgenerational epigenetic inheritance, and ultimately, animal fertility.
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Affiliation(s)
- Natasha E Weiser
- Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - John K Kim
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA;
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18
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Saltzman AL, Soo MW, Aram R, Lee JT. Multiple Histone Methyl-Lysine Readers Ensure Robust Development and Germline Immortality in Caenorhabditis elegans. Genetics 2018; 210:907-923. [PMID: 30185429 PMCID: PMC6218232 DOI: 10.1534/genetics.118.301518] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 08/23/2018] [Indexed: 11/18/2022] Open
Abstract
Chromatin modifications, including methylation of histone H3 at lysine 27 (H3K27me) by the Polycomb group proteins, play a broadly conserved role in the maintenance of cell fate. Diverse chromatin organization modifier (chromo) domain proteins act as "readers" of histone methylation states. However, understanding the functional relationships among chromo domains and their roles in the inheritance of gene expression patterns remains challenging. Here, we identify two chromo-domain proteins, CEC-1 and CEC-6, as potential readers of H3K27me in Caenorhabditis elegans, where they have divergent expression patterns and contribute to distinct phenotypes. Both cec-1 and cec-6 genetically interact with another chromo-domain gene, cec-3, a reader of H3K9 methylation. Combined loss of cec-1 and cec-3 leads to developmental defects in the adult that result in decreased fitness. Furthermore, loss of cec-6 and cec-3 surprisingly leads to a progressive loss of fertility across generations, a "mortal germline" phenotype. Our results provide evidence of functional compensation between H3K27me and H3K9me heterochromatin pathways, and show that histone methylation readers contribute to both somatic development and transgenerational fitness.
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Affiliation(s)
- Arneet L Saltzman
- Department of Molecular Biology, Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, Massachusetts 02114
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
| | - Mark W Soo
- Department of Molecular Biology, Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, Massachusetts 02114
| | - Reta Aram
- Department of Cell and Systems Biology, University of Toronto, Ontario M5S 3G5, Canada
| | - Jeannie T Lee
- Department of Molecular Biology, Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, Massachusetts 02114
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
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19
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Wilson DM, Rieckher M, Williams AB, Schumacher B. Systematic analysis of DNA crosslink repair pathways during development and aging in Caenorhabditis elegans. Nucleic Acids Res 2017; 45:9467-9480. [PMID: 28934497 PMCID: PMC5766164 DOI: 10.1093/nar/gkx660] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 07/18/2017] [Indexed: 01/12/2023] Open
Abstract
DNA interstrand crosslinks (ICLs) are generated by endogenous sources and chemotherapeutics, and pose a threat to genome stability and cell survival. Using Caenorhabditis elegans mutants, we identify DNA repair factors that protect against the genotoxicity of ICLs generated by trioxsalen/ultraviolet A (TMP/UVA) during development and aging. Mutations in nucleotide excision repair (NER) components (e.g. XPA-1 and XPF-1) imparted extreme sensitivity to TMP/UVA relative to wild-type animals, manifested as developmental arrest, defects in adult tissue morphology and functionality, and shortened lifespan. Compensatory roles for global-genome (XPC-1) and transcription-coupled (CSB-1) NER in ICL sensing were exposed. The analysis also revealed contributions of homologous recombination (BRC-1/BRCA1), the MUS-81, EXO-1, SLX-1 and FAN-1 nucleases, and the DOG-1 (FANCJ) helicase in ICL resolution, influenced by the replicative-status of the cell/tissue. No obvious or critical role in ICL repair was seen for non-homologous end-joining (cku-80) or base excision repair (nth-1, exo-3), the Fanconi-related proteins BRC-2 (BRCA2/FANCD1) and FCD-2 (FANCD2), the WRN-1 or HIM-6 (BLM) helicases, or the GEN-1 or MRT-1 (SNM1) nucleases. Our efforts uncover replication-dependent and -independent ICL repair networks, and establish nematodes as a model for investigating the repair and consequences of DNA crosslinks in metazoan development and in adult post-mitotic and proliferative germ cells.
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Affiliation(s)
- David M Wilson
- Laboratory of Molecular Gerontology, National Institute on Aging, Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Matthias Rieckher
- Institute for Genome Stability in Aging and Disease, Medical Faculty, Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne (CMMC) and Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Ashley B Williams
- Institute for Genome Stability in Aging and Disease, Medical Faculty, Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne (CMMC) and Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Björn Schumacher
- Institute for Genome Stability in Aging and Disease, Medical Faculty, Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne (CMMC) and Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
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20
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Fradin H, Kiontke K, Zegar C, Gutwein M, Lucas J, Kovtun M, Corcoran DL, Baugh LR, Fitch DHA, Piano F, Gunsalus KC. Genome Architecture and Evolution of a Unichromosomal Asexual Nematode. Curr Biol 2017; 27:2928-2939.e6. [PMID: 28943090 PMCID: PMC5659720 DOI: 10.1016/j.cub.2017.08.038] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/14/2017] [Accepted: 08/15/2017] [Indexed: 10/24/2022]
Abstract
Asexual reproduction in animals, though rare, is the main or exclusive mode of reproduction in some long-lived lineages. The longevity of asexual clades may be correlated with the maintenance of heterozygosity by mechanisms that rearrange genomes and reduce recombination. Asexual species thus provide an opportunity to gain insight into the relationship between molecular changes, genome architecture, and cellular processes. Here we report the genome sequence of the parthenogenetic nematode Diploscapter pachys with only one chromosome pair. We show that this unichromosomal architecture is shared by a long-lived clade of asexual nematodes closely related to the genetic model organism Caenorhabditis elegans. Analysis of the genome assembly reveals that the unitary chromosome arose through fusion of six ancestral chromosomes, with extensive rearrangement among neighboring regions. Typical nematode telomeres and telomeric protection-encoding genes are lacking. Most regions show significant heterozygosity; homozygosity is largely concentrated to one region and attributed to gene conversion. Cell-biological and molecular evidence is consistent with the absence of key features of meiosis I, including synapsis and recombination. We propose that D. pachys preserves heterozygosity and produces diploid embryos without fertilization through a truncated meiosis. As a prelude to functional studies, we demonstrate that D. pachys is amenable to experimental manipulation by RNA interference.
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Affiliation(s)
- Hélène Fradin
- Department of Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Karin Kiontke
- Department of Biology, New York University, New York, NY 10003, USA
| | - Charles Zegar
- Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Michelle Gutwein
- Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Jessica Lucas
- Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Mikhail Kovtun
- Duke Center for Genomic and Computational Biology, Duke University, Durham, NC 27708, USA
| | - David L Corcoran
- Duke Center for Genomic and Computational Biology, Duke University, Durham, NC 27708, USA
| | - L Ryan Baugh
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - David H A Fitch
- Department of Biology, New York University, New York, NY 10003, USA.
| | - Fabio Piano
- Department of Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
| | - Kristin C Gunsalus
- Department of Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
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21
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Abstract
Most animals have male and female sexes, implying that sex is ancient and beneficial; yet some have survived for millions of years without sex. The genome of the parthenogenetic nematode Diploscapter pachys gives clues as to how 'ancient asexual' animals can exist.
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Affiliation(s)
- Erich M Schwarz
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
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22
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Weiser NE, Yang DX, Feng S, Kalinava N, Brown KC, Khanikar J, Freeberg MA, Snyder MJ, Csankovszki G, Chan RC, Gu SG, Montgomery TA, Jacobsen SE, Kim JK. MORC-1 Integrates Nuclear RNAi and Transgenerational Chromatin Architecture to Promote Germline Immortality. Dev Cell 2017; 41:408-423.e7. [PMID: 28535375 DOI: 10.1016/j.devcel.2017.04.023] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 04/05/2017] [Accepted: 04/25/2017] [Indexed: 12/12/2022]
Abstract
Germline-expressed endogenous small interfering RNAs (endo-siRNAs) transmit multigenerational epigenetic information to ensure fertility in subsequent generations. In Caenorhabditis elegans, nuclear RNAi ensures robust inheritance of endo-siRNAs and deposition of repressive H3K9me3 marks at target loci. How target silencing is maintained in subsequent generations is poorly understood. We discovered that morc-1 is essential for transgenerational fertility and acts as an effector of endo-siRNAs. Unexpectedly, morc-1 is dispensable for siRNA inheritance but is required for target silencing and maintenance of siRNA-dependent chromatin organization. A forward genetic screen identified mutations in met-1, which encodes an H3K36 methyltransferase, as potent suppressors of morc-1(-) and nuclear RNAi mutant phenotypes. Further analysis of nuclear RNAi and morc-1(-) mutants revealed a progressive, met-1-dependent enrichment of H3K36me3, suggesting that robust fertility requires repression of MET-1 activity at nuclear RNAi targets. Without MORC-1 and nuclear RNAi, MET-1-mediated encroachment of euchromatin leads to detrimental decondensation of germline chromatin and germline mortality.
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Affiliation(s)
- Natasha E Weiser
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Danny X Yang
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Suhua Feng
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, PO Box 957239, Los Angeles, CA 90095-7239, USA; Eli and Edyth Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Natallia Kalinava
- Department of Molecular Biology and Biochemistry, Rutgers the State University of New Jersey, Piscataway, NJ 08854, USA
| | - Kristen C Brown
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Jayshree Khanikar
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Mallory A Freeberg
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
| | - Martha J Snyder
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Györgyi Csankovszki
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Raymond C Chan
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Sam G Gu
- Department of Molecular Biology and Biochemistry, Rutgers the State University of New Jersey, Piscataway, NJ 08854, USA
| | - Taiowa A Montgomery
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Steven E Jacobsen
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, PO Box 957239, Los Angeles, CA 90095-7239, USA; Eli and Edyth Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA 90095, USA; Howard Hughes Medical Institute, Los Angeles, CA 90095, USA.
| | - John K Kim
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA; Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.
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23
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AMPK blocks starvation-inducible transgenerational defects in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2017; 114:E2689-E2698. [PMID: 28289190 DOI: 10.1073/pnas.1616171114] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Life history events, such as traumatic stress, illness, or starvation, can influence us through molecular changes that are recorded in a pattern of characteristic chromatin modifications. These modifications are often associated with adaptive adjustments in gene expression that can persist throughout the lifetime of the organism, or even span multiple generations. Although these adaptations may confer some selective advantage, if they are not appropriately regulated they can also be maladaptive in a context-dependent manner. We show here that during periods of acute starvation in Caenorhabditis elegans larvae, the master metabolic regulator AMP-activated protein kinase (AMPK) plays a critical role in blocking modifications to the chromatin landscape. This ensures that gene expression remains inactive in the germ-line precursors during adverse conditions. In its absence, critical chromatin modifications occur in the primordial germ cells (PGCs) of emergent starved L1 larvae that correlate with compromised reproductive fitness of the generation that experienced the stress, but also in the subsequent generations that never experienced the initial event. Our findings suggest that AMPK regulates the activity of the chromatin modifying COMPASS complex (complex proteins associated with Set1) to ensure that chromatin marks are not established until nutrient/energy contingencies are satisfied. Our study provides molecular insight that links metabolic adaptation to transgenerational epigenetic modification in response to acute periods of starvation.
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24
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The Genetic Basis of Natural Variation in Caenorhabditis elegans Telomere Length. Genetics 2016; 204:371-83. [PMID: 27449056 PMCID: PMC5012401 DOI: 10.1534/genetics.116.191148] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Accepted: 07/14/2016] [Indexed: 01/03/2023] Open
Abstract
Telomeres are involved in the maintenance of chromosomes and the prevention of genome instability. Despite this central importance, significant variation in telomere length has been observed in a variety of organisms. The genetic determinants of telomere-length variation and their effects on organismal fitness are largely unexplored. Here, we describe natural variation in telomere length across the Caenorhabditis elegans species. We identify a large-effect variant that contributes to differences in telomere length. The variant alters the conserved oligonucleotide/oligosaccharide-binding fold of protection of telomeres 2 (POT-2), a homolog of a human telomere-capping shelterin complex subunit. Mutations within this domain likely reduce the ability of POT-2 to bind telomeric DNA, thereby increasing telomere length. We find that telomere-length variation does not correlate with offspring production or longevity in C. elegans wild isolates, suggesting that naturally long telomeres play a limited role in modifying fitness phenotypes in C. elegans.
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25
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26
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Roerink SF, van Schendel R, Tijsterman M. Polymerase theta-mediated end joining of replication-associated DNA breaks in C. elegans. Genome Res 2014; 24:954-62. [PMID: 24614976 PMCID: PMC4032859 DOI: 10.1101/gr.170431.113] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 03/04/2014] [Indexed: 11/24/2022]
Abstract
DNA lesions that block replication fork progression are drivers of cancer-associated genome alterations, but the error-prone DNA repair mechanisms acting on collapsed replication are incompletely understood, and their contribution to genome evolution largely unexplored. Here, through whole-genome sequencing of animal populations that were clonally propagated for more than 50 generations, we identify a distinct class of deletions that spontaneously accumulate in C. elegans strains lacking translesion synthesis (TLS) polymerases. Emerging DNA double-strand breaks are repaired via an error-prone mechanism in which the outermost nucleotide of one end serves to prime DNA synthesis on the other end. This pathway critically depends on the A-family polymerase theta, which protects the genome against gross chromosomal rearrangements. By comparing the genomes of isolates of C. elegans from different geographical regions, we found that in fact most spontaneously evolving structural variations match the signature of polymerase theta-mediated end joining (TMEJ), illustrating that this pathway is an important source of genetic diversification.
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Affiliation(s)
| | | | - Marcel Tijsterman
- Department of Toxicogenetics, Leiden University Medical Center, 2300 RC Leiden, The Netherlands
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Clauson C, Schärer OD, Niedernhofer L. Advances in understanding the complex mechanisms of DNA interstrand cross-link repair. Cold Spring Harb Perspect Biol 2013; 5:a012732. [PMID: 24086043 DOI: 10.1101/cshperspect.a012732] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
DNA interstrand cross-links (ICLs) are lesions caused by a variety of endogenous metabolites, environmental exposures, and cancer chemotherapeutic agents that have two reactive groups. The common feature of these diverse lesions is that two nucleotides on opposite strands are covalently joined. ICLs prevent the separation of two DNA strands and therefore essential cellular processes including DNA replication and transcription. ICLs are mainly detected in S phase when a replication fork stalls at an ICL. Damage signaling and repair of ICLs are promoted by the Fanconi anemia pathway and numerous posttranslational modifications of DNA repair and chromatin structural proteins. ICLs are also detected and repaired in nonreplicating cells, although the mechanism is less clear. A unique feature of ICL repair is that both strands of DNA must be incised to completely remove the lesion. This is accomplished in sequential steps to prevent creating multiple double-strand breaks. Unhooking of an ICL from one strand is followed by translesion synthesis to fill the gap and create an intact duplex DNA, harboring a remnant of the ICL. Removal of the lesion from the second strand is likely accomplished by nucleotide excision repair. Inadequate repair of ICLs is particularly detrimental to rapidly dividing cells, explaining the bone marrow failure characteristic of Fanconi anemia and why cross-linking agents are efficacious in cancer therapy. Herein, recent advances in our understanding of ICLs and the biological responses they trigger are discussed.
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Affiliation(s)
- Cheryl Clauson
- Department of Microbiology and Molecular Genetics, The University of Pittsburgh, Pittsburgh, Pennsylvania 15219
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Saito TT, Lui DY, Kim HM, Meyer K, Colaiácovo MP. Interplay between structure-specific endonucleases for crossover control during Caenorhabditis elegans meiosis. PLoS Genet 2013; 9:e1003586. [PMID: 23874210 PMCID: PMC3715419 DOI: 10.1371/journal.pgen.1003586] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 05/07/2013] [Indexed: 11/18/2022] Open
Abstract
The number and distribution of crossover events are tightly regulated at prophase of meiosis I. The resolution of Holliday junctions by structure-specific endonucleases, including MUS-81, SLX-1, XPF-1 and GEN-1, is one of the main mechanisms proposed for crossover formation. However, how these nucleases coordinately resolve Holliday junctions is still unclear. Here we identify both the functional overlap and differences between these four nucleases regarding their roles in crossover formation and control in the Caenorhabditis elegans germline. We show that MUS-81, XPF-1 and SLX-1, but not GEN-1, can bind to HIM-18/SLX4, a key scaffold for nucleases. Analysis of synthetic mitotic defects revealed that MUS-81 and SLX-1, but not XPF-1 and GEN-1, have overlapping roles with the Bloom syndrome helicase ortholog, HIM-6, supporting their in vivo roles in processing recombination intermediates. Taking advantage of the ease of genetic analysis and high-resolution imaging afforded by C. elegans, we examined crossover designation, frequency, distribution and chromosomal morphology in single, double, triple and quadruple mutants of the structure-specific endonucleases. This revealed that XPF-1 functions redundantly with MUS-81 and SLX-1 in executing crossover formation during meiotic double-strand break repair. Analysis of crossover distribution revealed that SLX-1 is required for crossover suppression at the center region of the autosomes. Finally, analysis of chromosome morphology in oocytes at late meiosis I stages uncovered that SLX-1 and XPF-1 promote meiotic chromosomal stability by preventing formation of chromosomal abnormalities. We propose a model in which coordinate action between structure-specific nucleases at different chromosome domains, namely MUS-81, SLX-1 and XPF-1 at the arms and SLX-1 at the center region, exerts positive and negative regulatory roles, respectively, for crossover control during C. elegans meiosis.
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Affiliation(s)
- Takamune T. Saito
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Doris Y. Lui
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Hyun-Min Kim
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Katherine Meyer
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Monica P. Colaiácovo
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
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Dargahi D, Baillie D, Pio F. Bioinformatics analysis identify novel OB fold protein coding genes in C. elegans. PLoS One 2013; 8:e62204. [PMID: 23638006 PMCID: PMC3636199 DOI: 10.1371/journal.pone.0062204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 03/20/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The C. elegans genome has been extensively annotated by the WormBase consortium that uses state of the art bioinformatics pipelines, functional genomics and manual curation approaches. As a result, the identification of novel genes in silico in this model organism is becoming more challenging requiring new approaches. The Oligonucleotide-oligosaccharide binding (OB) fold is a highly divergent protein family, in which protein sequences, in spite of having the same fold, share very little sequence identity (5-25%). Therefore, evidence from sequence-based annotation may not be sufficient to identify all the members of this family. In C. elegans, the number of OB-fold proteins reported is remarkably low (n=46) compared to other evolutionary-related eukaryotes, such as yeast S. cerevisiae (n=344) or fruit fly D. melanogaster (n=84). Gene loss during evolution or differences in the level of annotation for this protein family, may explain these discrepancies. METHODOLOGY/PRINCIPAL FINDINGS This study examines the possibility that novel OB-fold coding genes exist in the worm. We developed a bioinformatics approach that uses the most sensitive sequence-sequence, sequence-profile and profile-profile similarity search methods followed by 3D-structure prediction as a filtering step to eliminate false positive candidate sequences. We have predicted 18 coding genes containing the OB-fold that have remarkably partially been characterized in C. elegans. CONCLUSIONS/SIGNIFICANCE This study raises the possibility that the annotation of highly divergent protein fold families can be improved in C. elegans. Similar strategies could be implemented for large scale analysis by the WormBase consortium when novel versions of the genome sequence of C. elegans, or other evolutionary related species are being released. This approach is of general interest to the scientific community since it can be used to annotate any genome.
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Affiliation(s)
- Daryanaz Dargahi
- Molecular Biology and Biochemistry Department, Simon Fraser University, Burnaby, British Columbia, Canada
| | - David Baillie
- Molecular Biology and Biochemistry Department, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Frederic Pio
- Molecular Biology and Biochemistry Department, Simon Fraser University, Burnaby, British Columbia, Canada
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Shtessel L, Lowden MR, Cheng C, Simon M, Wang K, Ahmed S. Caenorhabditis elegans POT-1 and POT-2 repress telomere maintenance pathways. G3 (BETHESDA, MD.) 2013; 3:305-13. [PMID: 23390606 PMCID: PMC3564990 DOI: 10.1534/g3.112.004440] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 12/11/2012] [Indexed: 12/23/2022]
Abstract
Telomeres are composed of simple tandem DNA repeats that protect the ends of linear chromosomes from replicative erosion or inappropriate DNA damage response mechanisms. The mammalian Protection Of Telomeres (POT1) protein interacts with single-stranded telomeric DNA and can exert positive and negative effects on telomere length. Of four distinct POT1 homologs in the roundworm Caenorhabditis elegans, deficiency for POT-1 or POT-2 resulted in progressive telomere elongation that occurred because both proteins negatively regulate telomerase. We created a POT-1::mCherry fusion protein that forms discrete foci at C. elegans telomeres, independent of POT-2, allowing for live analysis of telomere dynamics. Transgenic pot-1::mCherry repressed telomerase in pot-1 mutants. Animals deficient for pot-1, but not pot-2, displayed mildly enhanced telomere erosion rates in the absence of the telomerase reverse transcriptase, trt-1. However, trt-1; pot-1 double mutants exhibited delayed senescence in comparison to trt-1 animals, and senescence was further delayed in trt-1; pot-2; pot-1 triple mutants, some of which survived robustly in the absence of telomerase. Our results indicate that POT-1 and POT-2 play independent roles in suppressing a telomerase-independent telomere maintenance pathway but may function together to repress telomerase.
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Affiliation(s)
- Ludmila Shtessel
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280
| | - Mia Rochelle Lowden
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280
| | - Chen Cheng
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280
| | - Matt Simon
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280
| | - Kyle Wang
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280
| | - Shawn Ahmed
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280
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31
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Van Wynsberghe PM, Maine EM. Epigenetic control of germline development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 757:373-403. [PMID: 22872484 DOI: 10.1007/978-1-4614-4015-4_13] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Dynamic regulation of histone modifications and small noncoding RNAs is observed throughout the development of the C. elegans germ line. Histone modifications are differentially regulated in the mitotic vs meiotic germ line, on X chromosomes vs autosomes and on paired chromosomes vs unpaired chromosomes. Small RNAs function in transposon silencing and developmental gene regulation. Histone modifications and small RNAs produced in the germ line can be inherited and impact embryonic development. Disruption of histone-modifying enzymes or small RNA machinery in the germ line can result in sterility due to degeneration of the germ line and/or an inability to produce functional gametes.
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32
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Cheng C, Shtessel L, Brady MM, Ahmed S. Caenorhabditis elegans POT-2 telomere protein represses a mode of alternative lengthening of telomeres with normal telomere lengths. Proc Natl Acad Sci U S A 2012. [PMID: 22547822 DOI: 10.1073/pnas.lll9191109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023] Open
Abstract
Canonical telomere repeats at chromosome termini can be maintained by a telomerase-independent pathway termed alternative lengthening of telomeres (ALT). Human cancers that survive via ALT can exhibit long and heterogeneous telomeres, although many telomerase-negative tumors possess telomeres of normal length. Here, we report that Caenorhabditis elegans telomerase mutants that survived via ALT possessed either long or normal telomere lengths. Most ALT strains displayed end-to-end chromosome fusions, suggesting that critical telomere shortening occurred before or concomitant with ALT. ALT required the 9-1-1 DNA damage response complex and its clamp loader, HPR-17. Deficiency for the POT-2 telomere binding protein promoted ALT in telomerase mutants, overcame the requirement for the 9-1-1 complex in ALT, and promoted ALT with normal telomere lengths. We propose that telomerase-deficient human tumors with normal telomere lengths could represent a mode of ALT that is facilitated by telomere capping protein dysfunction.
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Affiliation(s)
- Chen Cheng
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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33
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Caenorhabditis elegans POT-2 telomere protein represses a mode of alternative lengthening of telomeres with normal telomere lengths. Proc Natl Acad Sci U S A 2012; 109:7805-10. [PMID: 22547822 DOI: 10.1073/pnas.1119191109] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Canonical telomere repeats at chromosome termini can be maintained by a telomerase-independent pathway termed alternative lengthening of telomeres (ALT). Human cancers that survive via ALT can exhibit long and heterogeneous telomeres, although many telomerase-negative tumors possess telomeres of normal length. Here, we report that Caenorhabditis elegans telomerase mutants that survived via ALT possessed either long or normal telomere lengths. Most ALT strains displayed end-to-end chromosome fusions, suggesting that critical telomere shortening occurred before or concomitant with ALT. ALT required the 9-1-1 DNA damage response complex and its clamp loader, HPR-17. Deficiency for the POT-2 telomere binding protein promoted ALT in telomerase mutants, overcame the requirement for the 9-1-1 complex in ALT, and promoted ALT with normal telomere lengths. We propose that telomerase-deficient human tumors with normal telomere lengths could represent a mode of ALT that is facilitated by telomere capping protein dysfunction.
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34
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Shtessel L, Ahmed S. Telomere dysfunction in human bone marrow failure syndromes. Nucleus 2012; 2:24-9. [PMID: 21647296 DOI: 10.4161/nucl.2.1.13993] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Revised: 10/19/2010] [Accepted: 10/20/2010] [Indexed: 12/25/2022] Open
Abstract
Approximately 90% of all human cancers, in which some deregulation of cell cycle arrest or programmed cell death has occurred, express telomerase, a ribonucleoprotein whose activity is normally turned off in healthy somatic tissues. Additionally, small populations of self-renewing stem cells, such as hematopoietic stem cells, skin and hair follicle basal layer cells and intestinal basal crypt cells, have been shown to retain telomerase activity. Conversely, hereditary defects that result in shortened telomeres in humans have been shown to manifest most often as bone marrow failure or pulmonary fibrosis, along with a myriad of other symptoms, likely due to the loss of the stem and/or progenitor cells of affected tissues. The aim of this review is to highlight our knowledge of the mechanisms of telomere maintenance that contribute to the pathology of human disease caused by dysfunctional telomere homeostasis. Specifically, a new role for the SNM1B/Apollo nuclease in the pathologies of Hoyeraal-Hreidarsson syndrome will be discussed.
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Affiliation(s)
- Ludmila Shtessel
- Department of Genetics, University of North Carolina, Chapel Hill, USA
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35
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Lemmens BBLG, Tijsterman M. DNA double-strand break repair in Caenorhabditis elegans. Chromosoma 2011; 120:1-21. [PMID: 21052706 PMCID: PMC3028100 DOI: 10.1007/s00412-010-0296-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Revised: 10/14/2010] [Accepted: 10/15/2010] [Indexed: 10/25/2022]
Abstract
Faithful repair of DNA double-strand breaks (DSBs) is vital for animal development, as inappropriate repair can cause gross chromosomal alterations that result in cellular dysfunction, ultimately leading to cancer, or cell death. Correct processing of DSBs is not only essential for maintaining genomic integrity, but is also required in developmental programs, such as gametogenesis, in which DSBs are deliberately generated. Accordingly, DSB repair deficiencies are associated with various developmental disorders including cancer predisposition and infertility. To avoid this threat, cells are equipped with an elaborate and evolutionarily well-conserved network of DSB repair pathways. In recent years, Caenorhabditis elegans has become a successful model system in which to study DSB repair, leading to important insights in this process during animal development. This review will discuss the major contributions and recent progress in the C. elegans field to elucidate the complex networks involved in DSB repair, the impact of which extends well beyond the nematode phylum.
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Affiliation(s)
- Bennie B. L. G. Lemmens
- Department of Toxicogenetics, Leids Universitair Medisch Centrum Gebouw 2, Postzone S-4 Postbus 9600, Einthovenweg 20, 2333 ZC Leiden, The Netherlands
| | - Marcel Tijsterman
- Department of Toxicogenetics, Leids Universitair Medisch Centrum Gebouw 2, Postzone S-4 Postbus 9600, Einthovenweg 20, 2333 ZC Leiden, The Netherlands
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36
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Cattell E, Sengerová B, McHugh PJ. The SNM1/Pso2 family of ICL repair nucleases: from yeast to man. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2010; 51:635-645. [PMID: 20175117 DOI: 10.1002/em.20556] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Efficient interstrand crosslink (ICL) repair in yeast depends on the Pso2/Snm1 protein. Pso2 is a member of the highly conserved metallo-beta-lactamase structural family of nucleases. Mammalian cells possess three SNM1/Pso2 related proteins, SNM1A, SNM1B/Apollo, and SNM1C/Artemis. Evidence that SNM1A and SNM1B contribute to ICL repair is mounting, whereas Artemis appears to primarily contribute to non-ICL repair pathways, particularly some double-strand break repair events. Yeast Pso2 and all three mammalian SNM1-family proteins have been shown to possess nuclease activity. Here, we review the biochemical, genetic, and cellular evidence for the SNM1 family as DNA repair factors, focusing on ICL repair.
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Affiliation(s)
- Emma Cattell
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
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McVey M. Strategies for DNA interstrand crosslink repair: insights from worms, flies, frogs, and slime molds. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2010; 51:646-658. [PMID: 20143343 DOI: 10.1002/em.20551] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
DNA interstrand crosslinks (ICLs) are complex lesions that covalently link both strands of the DNA double helix and impede essential cellular processes such as DNA replication and transcription. Recent studies suggest that multiple repair pathways are involved in their removal. Elegant genetic analysis has demonstrated that at least three distinct sets of pathways cooperate in the repair and/or bypass of ICLs in budding yeast. Although the mechanisms of ICL repair in mammals appear similar to those in yeast, important differences have been documented. In addition, mammalian crosslink repair requires other repair factors, such as the Fanconi anemia proteins, whose functions are poorly understood. Because many of these proteins are conserved in simpler metazoans, nonmammalian models have become attractive systems for studying the function(s) of key crosslink repair factors. This review discusses the contributions that various model organisms have made to the field of ICL repair. Specifically, it highlights how studies performed with C. elegans, Drosophila, Xenopus, and the social amoeba Dictyostelium serve to complement those from bacteria, yeast, and mammals. Together, these investigations have revealed that although the underlying themes of ICL repair are largely conserved, the complement of DNA repair proteins utilized and the ways in which each of the proteins is used can vary substantially between different organisms.
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Affiliation(s)
- Mitch McVey
- Department of Biology, Tufts University, Medford, Massachusetts 02155, USA.
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Abstract
Proteins that specifically bind the single-stranded overhang at the ends of telomeres have been identified in a wide range of eukaryotes and play pivotal roles in chromosome end protection and telomere length regulation. Here we summarize recent findings regarding the functions of POT1 proteins in vertebrates and discuss the functional evolution of POT1 proteins following gene duplication in protozoa, plants, nematodes and mice.
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Affiliation(s)
- Peter Baumann
- Howard Hughes Medical Institute, Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
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Abstract
Although now dogma, the idea that nonvertebrate organisms such as yeast, worms, and flies could inform, and in some cases even revolutionize, our understanding of oncogenesis in humans was not immediately obvious. Aided by the conservative nature of evolution and the persistence of a cohort of devoted researchers, the role of model organisms as a key tool in solving the cancer problem has, however, become widely accepted. In this review, we focus on the nematode Caenorhabditis elegans and its diverse and sometimes surprising contributions to our understanding of the tumorigenic process. Specifically, we discuss findings in the worm that address a well-defined set of processes known to be deregulated in cancer cells including cell cycle progression, growth factor signaling, terminal differentiation, apoptosis, the maintenance of genome stability, and developmental mechanisms relevant to invasion and metastasis.
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Affiliation(s)
- Natalia V. Kirienko
- University of Wyoming, College of Agriculture, Department of Molecular Biology, Dept 3944, 1000 E. University Avenue, Laramie, WY 82071
| | - Kumaran Mani
- University of Wyoming, College of Agriculture, Department of Molecular Biology, Dept 3944, 1000 E. University Avenue, Laramie, WY 82071
| | - David S. Fay
- University of Wyoming, College of Agriculture, Department of Molecular Biology, Dept 3944, 1000 E. University Avenue, Laramie, WY 82071
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Wakamatsu T, Kitamura Y, Kotera Y, Nakagawa N, Kuramitsu S, Masui R. Structure of RecJ exonuclease defines its specificity for single-stranded DNA. J Biol Chem 2010; 285:9762-9769. [PMID: 20129927 PMCID: PMC2843225 DOI: 10.1074/jbc.m109.096487] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Revised: 01/29/2010] [Indexed: 11/06/2022] Open
Abstract
RecJ is a single-stranded DNA (ssDNA)-specific 5'-3' exonuclease that plays an important role in DNA repair and recombination. To elucidate how RecJ achieves its high specificity for ssDNA, we determined the entire structures of RecJ both in a ligand-free form and in a complex with Mn(2+) or Mg(2+) by x-ray crystallography. The entire RecJ consists of four domains that form a molecule with an O-like structure. One of two newly identified domains had structural similarities to an oligonucleotide/oligosaccharide-binding (OB) fold. The OB fold domain alone could bind to DNA, indicating that this domain is a novel member of the OB fold superfamily. The truncated RecJ containing only the core domain exhibited much lower affinity for the ssDNA substrate compared with intact RecJ. These results support the hypothesis that these structural features allow specific binding of RecJ to ssDNA. In addition, the structure of the RecJ-Mn(2+) complex suggests that the hydrolysis reaction catalyzed by RecJ proceeds through a two-metal ion mechanism.
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Affiliation(s)
- Taisuke Wakamatsu
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871
| | - Yoshiaki Kitamura
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148
| | - Yutaro Kotera
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Noriko Nakagawa
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148; Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Seiki Kuramitsu
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871; RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148; Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Ryoji Masui
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148; Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
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