1
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Scalabrin S, Magris G, Liva M, Vitulo N, Vidotto M, Scaglione D, Del Terra L, Ruosi MR, Navarini L, Pellegrino G, Berny Mier Y Teran JC, Toniutti L, Suggi Liverani F, Cerutti M, Di Gaspero G, Morgante M. A chromosome-scale assembly reveals chromosomal aberrations and exchanges generating genetic diversity in Coffea arabica germplasm. Nat Commun 2024; 15:463. [PMID: 38263403 PMCID: PMC10805892 DOI: 10.1038/s41467-023-44449-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 12/13/2023] [Indexed: 01/25/2024] Open
Abstract
In order to better understand the mechanisms generating genetic diversity in the recent allotetraploid species Coffea arabica, here we present a chromosome-level assembly obtained with long read technology. Two genomic compartments with different structural and functional properties are identified in the two homoeologous genomes. The resequencing data from a large set of accessions reveals low intraspecific diversity in the center of origin of the species. Across a limited number of genomic regions, diversity increases in some cultivated genotypes to levels similar to those observed within one of the progenitor species, Coffea canephora, presumably as a consequence of introgressions deriving from the so-called Timor hybrid. It also reveals that, in addition to few, early-occurring exchanges between homoeologous chromosomes, there are numerous recent chromosomal aberrations including aneuploidies, deletions, duplications and exchanges. These events are still polymorphic in the germplasm and could represent a fundamental source of genetic variation in such a lowly variable species.
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Affiliation(s)
| | - Gabriele Magris
- Istituto di Genomica Applicata, 33100, Udine, Italy
- Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, 33100, Udine, Italy
| | - Mario Liva
- IGA Technology Services, 33100, Udine, Italy
- Istituto di Genomica Applicata, 33100, Udine, Italy
- Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, 33100, Udine, Italy
| | - Nicola Vitulo
- Department of Biotechnology, University of Verona, 37134, Verona, Italy
| | | | | | | | | | | | | | | | - Lucile Toniutti
- World Coffee Research, Portland, 97225, OR, USA
- CIRAD, UMR AGAP Institut, 97130, Capesterre-Belle-Eau, Guadeloupe, France
- UMR AGAP Institut, University of Montpellier, CIRAD, INRAE, Institut Agro, 34060, Montpellier, France
| | | | | | | | - Michele Morgante
- Istituto di Genomica Applicata, 33100, Udine, Italy.
- Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, 33100, Udine, Italy.
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2
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Al Zouabi L, Stefanutti M, Roumeliotis S, Le Meur G, Boumard B, Riddiford N, Rubanova N, Bohec M, Gervais L, Servant N, Bardin AJ. Molecular underpinnings and environmental drivers of loss of heterozygosity in Drosophila intestinal stem cells. Cell Rep 2023; 42:113485. [PMID: 38032794 DOI: 10.1016/j.celrep.2023.113485] [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: 08/03/2022] [Revised: 09/29/2023] [Accepted: 11/08/2023] [Indexed: 12/02/2023] Open
Abstract
During development and aging, genome mutation leading to loss of heterozygosity (LOH) can uncover recessive phenotypes within tissue compartments. This phenomenon occurs in normal human tissues and is prevalent in pathological genetic conditions and cancers. While studies in yeast have defined DNA repair mechanisms that can promote LOH, the predominant pathways and environmental triggers in somatic tissues of multicellular organisms are not well understood. Here, we investigate mechanisms underlying LOH in intestinal stem cells in Drosophila. Infection with the pathogenic bacteria, Erwinia carotovora carotovora 15, but not Pseudomonas entomophila, increases LOH frequency. Using whole genome sequencing of somatic LOH events, we demonstrate that they arise primarily via mitotic recombination. Molecular features and genetic evidence argue against a break-induced replication mechanism and instead support cross-over via double Holliday junction-based repair. This study provides a mechanistic understanding of mitotic recombination, an important mediator of LOH, and its effects on stem cells in vivo.
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Affiliation(s)
- Lara Al Zouabi
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Marine Stefanutti
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Spyridon Roumeliotis
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Gwenn Le Meur
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Benjamin Boumard
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Nick Riddiford
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Natalia Rubanova
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France; Bioinformatics, Biostatistics, Epidemiology and Computational Systems Unit, Institut Curie, PSL Research University, INSERM U900, 75005 Paris, France
| | - Mylène Bohec
- ICGex Next-Generation Sequencing Platform, Institut Curie, PSL Research University, 75005 Paris, France
| | - Louis Gervais
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Nicolas Servant
- Bioinformatics, Biostatistics, Epidemiology and Computational Systems Unit, Institut Curie, PSL Research University, INSERM U900, 75005 Paris, France
| | - Allison J Bardin
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France.
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3
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Overton MS, Guy SE, Chen X, Martsul A, Carolino K, Akbari OS, Meyer JR, Kryazhimskiy S. Upper Bound on the Mutational Burden Imposed by a CRISPR-Cas9 Gene-Drive Element. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.28.569142. [PMID: 38076841 PMCID: PMC10705488 DOI: 10.1101/2023.11.28.569142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
CRISPR-Cas9 gene drives (CCGDs) are powerful tools for genetic control of wild populations, useful for eradication of disease vectors, conservation of endangered species and other applications. However, Cas9 alone and in a complex with gRNA can cause double-stranded DNA breaks at off-target sites, which could increase the mutational load and lead to loss of heterozygosity (LOH). These undesired effects raise potential concerns about the long-term evolutionary safety of CCGDs, but the magnitude of these effects is unknown. To estimate how the presence of a CCGD or a Cas9 alone in the genome affects the rates of LOH events and de novo mutations, we carried out a mutation accumulation experiment in yeast Saccharomyces cerevisiae. Despite its substantial statistical power, our experiment revealed no detectable effect of CCGD or Cas9 alone on the genome-wide rates of mutations or LOH events, suggesting that these rates are affected by less than 30%. Nevertheless, we found that Cas9 caused a slight but significant shift towards more interstitial and fewer terminal LOH events, and the CCGD caused a significant difference in the distribution of LOH events on Chromosome V. Taken together, our results show that these genetic elements impose a weak and likely localized additional mutational burden in the yeast model. Although the mutagenic effects of CCGDs need to be further evaluated in other systems, our results suggest that the effect of CCGDs on off-target mutation rates and genetic diversity may be acceptable.
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Affiliation(s)
- Michael S. Overton
- Department of Ecology, Behavior and Evolution, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Sean E. Guy
- Department of Ecology, Behavior and Evolution, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093
- Current address: Bionano Genomics, San Diego, CA 92121
| | - Xingsen Chen
- Department of Ecology, Behavior and Evolution, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093
- Current address: Department of Entomology, University of Arizona, Tucson, Arizona, USA
| | - Alena Martsul
- Department of Ecology, Behavior and Evolution, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093
- Current address: Illumina Inc., San Diego, CA 92122
| | - Krypton Carolino
- Department of Ecology, Behavior and Evolution, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Omar S. Akbari
- Department of Cell and Developmental Biology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Justin R. Meyer
- Department of Ecology, Behavior and Evolution, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Sergey Kryazhimskiy
- Department of Ecology, Behavior and Evolution, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093
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4
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Tosato V, Rossi B, Sims J, Bruschi CV. Timing of Chromosome DNA Integration throughout the Yeast Cell Cycle. Biomolecules 2023; 13:biom13040614. [PMID: 37189362 DOI: 10.3390/biom13040614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 03/22/2023] [Accepted: 03/23/2023] [Indexed: 03/31/2023] Open
Abstract
The dynamic mechanism of cell uptake and genomic integration of exogenous linear DNA still has to be completely clarified, especially within each phase of the cell cycle. We present a study of integration events of double-stranded linear DNA molecules harboring at their ends sequence homologies to the host’s genome, all throughout the cell cycle of the model organism Saccharomyces cerevisiae, comparing the efficiency of chromosomal integration of two types of DNA cassettes tailored for site-specific integration and bridge-induced translocation. Transformability increases in S phase regardless of the sequence homologies, while the efficiency of chromosomal integration during a specific cycle phase depends upon the genomic targets. Moreover, the frequency of a specific translocation between chromosomes XV and VIII strongly increased during DNA synthesis under the control of Pol32 polymerase. Finally, in the null POL32 double mutant, different pathways drove the integration in the various phases of the cell cycle and bridge-induced translocation was possible outside the S phase even without Pol32. The discovery of this cell-cycle dependent regulation of specific pathways of DNA integration, associated with an increase of ROS levels following translocation events, is a further demonstration of a sensing ability of the yeast cell in determining a cell-cycle-related choice of DNA repair pathways under stress.
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5
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Sui Y, Epstein A, Dominska M, Zheng DQ, Petes T, Klein H. Ribodysgenesis: sudden genome instability in the yeast Saccharomyces cerevisiae arising from RNase H2 cleavage at genomic-embedded ribonucleotides. Nucleic Acids Res 2022; 50:6890-6902. [PMID: 35748861 PMCID: PMC9262587 DOI: 10.1093/nar/gkac536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 05/27/2022] [Accepted: 06/07/2022] [Indexed: 12/24/2022] Open
Abstract
Ribonucleotides can be incorporated into DNA during replication by the replicative DNA polymerases. These aberrant DNA subunits are efficiently recognized and removed by Ribonucleotide Excision Repair, which is initiated by the heterotrimeric enzyme RNase H2. While RNase H2 is essential in higher eukaryotes, the yeast Saccharomyces cerevisiae can survive without RNase H2 enzyme, although the genome undergoes mutation, recombination and other genome instability events at an increased rate. Although RNase H2 can be considered as a protector of the genome from the deleterious events that can ensue from recognition and removal of embedded ribonucleotides, under conditions of high ribonucleotide incorporation and retention in the genome in a RNase H2-negative strain, sudden introduction of active RNase H2 causes massive DNA breaks and genome instability in a condition which we term 'ribodysgenesis'. The DNA breaks and genome instability arise solely from RNase H2 cleavage directed to the ribonucleotide-containing genome. Survivors of ribodysgenesis have massive loss of heterozygosity events stemming from recombinogenic lesions on the ribonucleotide-containing DNA, with increases of over 1000X from wild-type. DNA breaks are produced over one to two divisions and subsequently cells adapt to RNase H2 and ribonucleotides in the genome and grow with normal levels of genome instability.
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Affiliation(s)
- Yang Sui
- State Key Laboratory of Motor Vehicle Biofuel Technology, Ocean College, Zhejiang University, Zhoushan 316021, China,Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Anastasiya Epstein
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Margaret Dominska
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Dao-Qiong Zheng
- State Key Laboratory of Motor Vehicle Biofuel Technology, Ocean College, Zhejiang University, Zhoushan 316021, China,Hainan Institute of Zhejiang University, Sanya 572000, China,ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311200, China
| | - Thomas D Petes
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Hannah L Klein
- To whom correspondence should be addressed. Tel: +1 212 263 5778;
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6
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Aggeli D, Marad DA, Liu X, Buskirk SW, Levy SF, Lang GI. Overdominant and partially dominant mutations drive clonal adaptation in diploid Saccharomyces cerevisiae. Genetics 2022; 221:6569837. [PMID: 35435209 PMCID: PMC9157133 DOI: 10.1093/genetics/iyac061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Accepted: 04/06/2022] [Indexed: 11/14/2022] Open
Abstract
Identification of adaptive targets in experimental evolution typically relies on extensive replication and genetic reconstruction. An alternative approach is to directly assay all mutations in an evolved clone by generating pools of segregants that contain random combinations of evolved mutations. Here, we apply this method to six Saccharomyces cerevisiae clones isolated from four diploid populations that were clonally evolved for 2,000 generations in rich glucose medium. Each clone contains 17-26 mutations relative to the ancestor. We derived intermediate genotypes between the founder and the evolved clones by bulk mating sporulated cultures of the evolved clones to a barcoded haploid version of the ancestor. We competed the resulting barcoded diploids en masse and quantified fitness in the experimental and alternative environments by barcode sequencing. We estimated average fitness effects of evolved mutations using barcode-based fitness assays and whole genome sequencing for a subset of segregants. In contrast to our previous work with haploid evolved clones, we find that diploids carry fewer beneficial mutations, with modest fitness effects (up to 5.4%) in the environment in which they arose. In agreement with theoretical expectations, reconstruction experiments show that all mutations with a detectable fitness effect manifest some degree of dominance over the ancestral allele, and most are overdominant. Genotypes with lower fitness effects in alternative environments allowed us to identify conditions that drive adaptation in our system.
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Affiliation(s)
- Dimitra Aggeli
- Department of Biological Sciences, Lehigh University, Bethlehem, PA18015, USA
| | - Daniel A Marad
- Department of Biological Sciences, Lehigh University, Bethlehem, PA18015, USA
| | - Xianan Liu
- Joint Initiative for Metrology in Biology, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA94025, USA
| | - Sean W Buskirk
- Department of Biological Sciences, Lehigh University, Bethlehem, PA18015, USA.,Department of Biology, West Chester University, West Chester, PA19383, USA
| | - Sasha F Levy
- Joint Initiative for Metrology in Biology, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA94025, USA
| | - Gregory I Lang
- Department of Biological Sciences, Lehigh University, Bethlehem, PA18015, USA
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7
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Global genomic instability caused by reduced expression of DNA polymerase ε in yeast. Proc Natl Acad Sci U S A 2022; 119:e2119588119. [PMID: 35290114 PMCID: PMC8944251 DOI: 10.1073/pnas.2119588119] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
SignificanceAlthough most studies of the genetic regulation of genome stability involve an analysis of mutations within the coding sequences of genes required for DNA replication or DNA repair, recent studies in yeast show that reduced levels of wild-type enzymes can also produce a mutator phenotype. By whole-genome sequencing and other methods, we find that reduced levels of the wild-type DNA polymerase ε in yeast greatly increase the rates of mitotic recombination, aneuploidy, and single-base mutations. The observed pattern of genome instability is different from those observed in yeast strains with reduced levels of the other replicative DNA polymerases, Pol α and Pol δ. These observations are relevant to our understanding of cancer and other diseases associated with genetic instability.
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8
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Jinks-Robertson S, Petes TD. Mitotic recombination in yeast: what we know and what we don't know. Curr Opin Genet Dev 2021; 71:78-85. [PMID: 34311384 PMCID: PMC8671248 DOI: 10.1016/j.gde.2021.07.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 06/29/2021] [Accepted: 07/01/2021] [Indexed: 12/11/2022]
Abstract
Saccharomyces cerevisiae is at the forefront of defining the major recombination mechanisms/models that repair targeted double-strand breaks during mitosis. Each of these models predicts specific molecular intermediates as well as genetic outcomes. Recent use of single-nucleotide polymorphisms to track the exchange of sequences in recombination products has provided an unprecedented level of detail about the corresponding intermediates and the extents to which different mechanisms are utilized. This approach also has revealed complexities that are not predicted by canonical models, suggesting that modifications to these models are needed. Current data are consistent with the initiation of most inter-homolog spontaneous mitotic recombination events by a double-strand break. In addition, the sister chromatid is preferred over the homolog as a repair template.
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Affiliation(s)
- Sue Jinks-Robertson
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, United States
| | - Thomas D Petes
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, United States.
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9
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Stewart JA, Hillegass MB, Oberlitner JH, Younkin EM, Wasserman BF, Casper AM. Noncanonical outcomes of break-induced replication produce complex, extremely long-tract gene conversion events in yeast. G3 (BETHESDA, MD.) 2021; 11:jkab245. [PMID: 34568913 PMCID: PMC8473981 DOI: 10.1093/g3journal/jkab245] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 07/06/2021] [Indexed: 11/18/2022]
Abstract
Long-tract gene conversions (LTGC) can result from the repair of collapsed replication forks, and several mechanisms have been proposed to explain how the repair process produces this outcome. We studied LTGC events produced from repair collapsed forks at yeast fragile site FS2. Our analysis included chromosome sizing by contour-clamped homogeneous electric field electrophoresis, next-generation whole-genome sequencing, and Sanger sequencing across repair event junctions. We compared the sequence and structure of LTGC events in our cells to the expected qualities of LTGC events generated by proposed mechanisms. Our evidence indicates that some LTGC events arise from half-crossover during BIR, some LTGC events arise from gap repair, and some LTGC events can be explained by either gap repair or "late" template switch during BIR. Also based on our data, we propose that models of collapsed replication forks be revised to show not a one-end double-strand break (DSB), but rather a two-end DSB in which the ends are separated in time and subject to gap repair.
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Affiliation(s)
- Joseph A Stewart
- Department of Environmental & Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | | | - Joseph H Oberlitner
- Department of Biology, Interdisciplinary Graduate Program in Genetics, The University of Iowa, Iowa City, IA 52242, USA
| | - Ellen M Younkin
- Department of Biology, Eastern Michigan University, Ypsilanti, MI 48197, USA
| | - Beth F Wasserman
- Department of Biology, Eastern Michigan University, Ypsilanti, MI 48197, USA
| | - Anne M Casper
- Department of Biology, Eastern Michigan University, Ypsilanti, MI 48197, USA
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10
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Fisher KJ, Vignogna RC, Lang GI. Overdominant Mutations Restrict Adaptive Loss of Heterozygosity at Linked Loci. Genome Biol Evol 2021; 13:6345346. [PMID: 34363476 PMCID: PMC8382679 DOI: 10.1093/gbe/evab181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2021] [Indexed: 12/29/2022] Open
Abstract
Loss of heterozygosity is a common mode of adaptation in asexual diploid populations. Because mitotic recombination frequently extends the full length of a chromosome arm, the selective benefit of loss of heterozygosity may be constrained by linked heterozygous mutations. In a previous laboratory evolution experiment with diploid yeast, we frequently observed homozygous mutations in the WHI2 gene on the right arm of Chromosome XV. However, when heterozygous mutations arose in the STE4 gene, another common target on Chromosome XV, loss of heterozygosity at WHI2 was not observed. Here, we show that mutations at WHI2 are partially dominant and that mutations at STE4 are overdominant. We test whether beneficial heterozygous mutations at these two loci interfere with one another by measuring loss of heterozygosity at WHI2 over 1,000 generations for ∼300 populations that differed initially only at STE4 and WHI2. We show that the presence of an overdominant mutation in STE4 reduces, but does not eliminate, loss of heterozygosity at WHI2. By sequencing 40 evolved clones, we show that populations with linked overdominant and partially dominant mutations show less parallelism at the gene level, more varied evolutionary outcomes, and increased rates of aneuploidy. Our results show that the degree of dominance and the phasing of heterozygous beneficial mutations can constrain loss of heterozygosity along a chromosome arm, and that conflicts between partially dominant and overdominant mutations can affect evolutionary outcomes.
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Affiliation(s)
- Kaitlin J Fisher
- Department of Biological Sciences, Lehigh University, USA.,Laboratory of Genetics, University of Wisconsin-Madison, USA
| | | | - Gregory I Lang
- Department of Biological Sciences, Lehigh University, USA
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11
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Dutta A, Dutreux F, Schacherer J. Loss of heterozygosity results in rapid but variable genome homogenization across yeast genetic backgrounds. eLife 2021; 10:70339. [PMID: 34159898 PMCID: PMC8245132 DOI: 10.7554/elife.70339] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 06/11/2021] [Indexed: 12/12/2022] Open
Abstract
The dynamics and diversity of the appearance of genetic variants play an essential role in the evolution of the genome and the shaping of biodiversity. Recent population-wide genome sequencing surveys have highlighted the importance of loss of heterozygosity (LOH) events and have shown that they are a neglected part of the genetic diversity landscape. To assess the extent, variability, and spectrum, we explored the accumulation of LOH events in 169 heterozygous diploid Saccharomyces cerevisiae mutation accumulation lines across nine genetic backgrounds. In total, we detected a large set of 22,828 LOH events across distinct genetic backgrounds with a heterozygous level ranging from 0.1% to 1%. LOH events are very frequent with a rate consistently much higher than the mutation rate, showing their importance for genome evolution. We observed that the interstitial LOH (I-LOH) events, resulting in internal short LOH tracts, were much frequent (n = 19,660) than the terminal LOH (T-LOH) events, that is, tracts extending to the end of the chromosome (n = 3168). However, the spectrum, the rate, and the fraction of the genome under LOH vary across genetic backgrounds. Interestingly, we observed that the more the ancestors were heterozygous, the more they accumulated T-LOH events. In addition, frequent short I-LOH tracts are a signature of the lines derived from hybrids with low spore fertility. Finally, we found lines showing almost complete homozygotization during vegetative progression. Overall, our results highlight that the variable dynamics of the LOH accumulation across distinct genetic backgrounds might lead to rapid differential genome evolution during vegetative growth.
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Affiliation(s)
- Abhishek Dutta
- Université de Strasbourg, CNRS, GMGM UMR 7156, Strasbourg, France
| | - Fabien Dutreux
- Université de Strasbourg, CNRS, GMGM UMR 7156, Strasbourg, France
| | - Joseph Schacherer
- Université de Strasbourg, CNRS, GMGM UMR 7156, Strasbourg, France.,Institut Universitaire de France (IUF), Paris, France
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12
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Nguyen DT, Wu B, Long H, Zhang N, Patterson C, Simpson S, Morris K, Thomas WK, Lynch M, Hao W. Variable Spontaneous Mutation and Loss of Heterozygosity among Heterozygous Genomes in Yeast. Mol Biol Evol 2021; 37:3118-3130. [PMID: 33219379 DOI: 10.1093/molbev/msaa150] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Mutation and recombination are the primary sources of genetic variation. To better understand the evolution of genetic variation, it is crucial to comprehensively investigate the processes involving mutation accumulation and recombination. In this study, we performed mutation accumulation experiments on four heterozygous diploid yeast species in the Saccharomycodaceae family to determine spontaneous mutation rates, mutation spectra, and losses of heterozygosity (LOH). We observed substantial variation in mutation rates and mutation spectra. We also observed high LOH rates (1.65-11.07×10-6 events per heterozygous site per cell division). Biases in spontaneous mutation and LOH together with selection ultimately shape the variable genome-wide nucleotide landscape in yeast species.
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Affiliation(s)
- Duong T Nguyen
- Department of Biological Sciences, Wayne State University, Detroit, MI
| | - Baojun Wu
- Department of Biological Sciences, Wayne State University, Detroit, MI
| | - Hongan Long
- Institute of Evolution and Marine Biodiversity, KLMME, Ocean University of China, Qingdao, Shandong Province, China
| | - Nan Zhang
- Department of Biological Sciences, Wayne State University, Detroit, MI
| | | | | | | | | | - Michael Lynch
- Center for Mechanisms of Evolution, The Biodesign Institute, Arizona State University, Tempe, AZ
| | - Weilong Hao
- Department of Biological Sciences, Wayne State University, Detroit, MI
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13
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Sandmann G, Pollmann H, Gassel S, Breitenbach J. Xanthophyllomyces dendrorhous, a Versatile Platform for the Production of Carotenoids and Other Acetyl-CoA-Derived Compounds. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1261:137-151. [PMID: 33783736 DOI: 10.1007/978-981-15-7360-6_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Xanthophyllomyces dendrorhous (with Phaffia rhodozyma as its anamorphic state) is a basidiomycetous, moderately psychrophilic, red yeast belonging to the Cystofilobasidiales. Its red pigmentation is caused by the accumulation of astaxanthin, which is a unique feature among fungi. The present chapter reviews astaxanthin biosynthesis and acetyl-CoA metabolism in X. dendrorhous and describes the construction of a versatile platform for the production of carotenoids, such as astaxanthin, and other acetyl-CoA-derived compounds including fatty acids by using this fungus.
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Affiliation(s)
- Gerhard Sandmann
- Biosynthesis Group, Molecular Biosciences, Goethe University, Frankfurt, Germany.
| | - Hendrik Pollmann
- Biosynthesis Group, Molecular Biosciences, Goethe University, Frankfurt, Germany
| | - Sören Gassel
- Biosynthesis Group, Molecular Biosciences, Goethe University, Frankfurt, Germany
| | - Jürgen Breitenbach
- Biosynthesis Group, Molecular Biosciences, Goethe University, Frankfurt, Germany
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14
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Jaron KS, Bast J, Nowell RW, Ranallo-Benavidez TR, Robinson-Rechavi M, Schwander T. Genomic Features of Parthenogenetic Animals. J Hered 2021; 112:19-33. [PMID: 32985658 PMCID: PMC7953838 DOI: 10.1093/jhered/esaa031] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 08/17/2020] [Indexed: 12/21/2022] Open
Abstract
Evolution without sex is predicted to impact genomes in numerous ways. Case studies of individual parthenogenetic animals have reported peculiar genomic features that were suggested to be caused by their mode of reproduction, including high heterozygosity, a high abundance of horizontally acquired genes, a low transposable element load, or the presence of palindromes. We systematically characterized these genomic features in published genomes of 26 parthenogenetic animals representing at least 18 independent transitions to asexuality. Surprisingly, not a single feature was systematically replicated across a majority of these transitions, suggesting that previously reported patterns were lineage-specific rather than illustrating the general consequences of parthenogenesis. We found that only parthenogens of hybrid origin were characterized by high heterozygosity levels. Parthenogens that were not of hybrid origin appeared to be largely homozygous, independent of the cellular mechanism underlying parthenogenesis. Overall, despite the importance of recombination rate variation for the evolution of sexual animal genomes, the genome-wide absence of recombination does not appear to have had the dramatic effects which are expected from classical theoretical models. The reasons for this are probably a combination of lineage-specific patterns, the impact of the origin of parthenogenesis, and a survivorship bias of parthenogenetic lineages.
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Affiliation(s)
- Kamil S Jaron
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
- Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Jens Bast
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Reuben W Nowell
- Department of Life Sciences, Imperial College London, Ascot, Berkshire, UK
- Reuben W. Nowell is now at the Department of Zoology, University of Oxford, Oxford, UK
| | | | - Marc Robinson-Rechavi
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
- Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Tanja Schwander
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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15
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Hartfield M. Approximating the Coalescent Under Facultative Sex. J Hered 2021; 112:145-154. [PMID: 33511984 DOI: 10.1093/jhered/esaa036] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 09/01/2020] [Indexed: 11/14/2022] Open
Abstract
Genome studies of facultative sexual species, which can either reproduce sexually or asexually, are providing insight into the evolutionary consequences of mixed reproductive modes. It is currently unclear to what extent the evolutionary history of facultative sexuals' genomes can be approximated by the standard coalescent, and if a coalescent effective population size Ne exists. Here, I determine if and when these approximations can be made. When sex is frequent (occurring at a frequency much greater than 1/N per reproduction per generation, for N the actual population size), the underlying genealogy can be approximated by the standard coalescent, with a coalescent Ne≈N. When sex is very rare (at frequency much lower than 1/N), approximations for the pairwise coalescent time can be obtained, which is strongly influenced by the frequencies of sex and mitotic gene conversion, rather than N. However, these terms do not translate into a coalescent Ne. These results are used to discuss the best sampling strategies for investigating the evolutionary history of facultative sexual species.
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Affiliation(s)
- Matthew Hartfield
- Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh, UK
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16
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Vakhrusheva OA, Mnatsakanova EA, Galimov YR, Neretina TV, Gerasimov ES, Naumenko SA, Ozerova SG, Zalevsky AO, Yushenova IA, Rodriguez F, Arkhipova IR, Penin AA, Logacheva MD, Bazykin GA, Kondrashov AS. Genomic signatures of recombination in a natural population of the bdelloid rotifer Adineta vaga. Nat Commun 2020; 11:6421. [PMID: 33339818 PMCID: PMC7749112 DOI: 10.1038/s41467-020-19614-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 10/23/2020] [Indexed: 01/08/2023] Open
Abstract
Sexual reproduction is almost ubiquitous among extant eukaryotes. As most asexual lineages are short-lived, abandoning sex is commonly regarded as an evolutionary dead end. Still, putative anciently asexual lineages challenge this view. One of the most striking examples are bdelloid rotifers, microscopic freshwater invertebrates believed to have completely abandoned sexual reproduction tens of Myr ago. Here, we compare whole genomes of 11 wild-caught individuals of the bdelloid rotifer Adineta vaga and present evidence that some patterns in its genetic variation are incompatible with strict clonality and lack of genetic exchange. These patterns include genotype proportions close to Hardy-Weinberg expectations within loci, lack of linkage disequilibrium between distant loci, incongruent haplotype phylogenies across the genome, and evidence for hybridization between divergent lineages. Analysis of triallelic sites independently corroborates these findings. Our results provide evidence for interindividual genetic exchange and recombination in A. vaga, a species previously thought to be anciently asexual.
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Affiliation(s)
- Olga A Vakhrusheva
- Skolkovo Institute of Science and Technology, Moscow, 121205, Russian Federation.
| | - Elena A Mnatsakanova
- Department of General Ecology and Hydrobiology, Faculty of Biology, M. V. Lomonosov Moscow State University, Moscow, 119234, Russian Federation
| | - Yan R Galimov
- Koltzov Institute of Developmental Biology of the Russian Academy of Sciences, Moscow, 119334, Russian Federation
| | - Tatiana V Neretina
- Faculty of Biology, M. V. Lomonosov Moscow State University, Moscow, 119234, Russian Federation
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), Moscow, 127051, Russian Federation
- A. N. Belozersky Institute of Physico-Chemical Biology, M. V. Lomonosov Moscow State University, Moscow, 119992, Russian Federation
| | - Evgeny S Gerasimov
- Faculty of Biology, M. V. Lomonosov Moscow State University, Moscow, 119234, Russian Federation
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), Moscow, 127051, Russian Federation
- Martsinovsky Institute of Medical Parasitology, Tropical and Vector-Borne Diseases, Sechenov University, Moscow, 119435, Russian Federation
| | - Sergey A Naumenko
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), Moscow, 127051, Russian Federation
- Department of Biostatistics, Harvard Chan School of Public Health, Boston, MA, 02115, USA
| | - Svetlana G Ozerova
- Koltzov Institute of Developmental Biology of the Russian Academy of Sciences, Moscow, 119334, Russian Federation
- Medkvadrat, Moscow, 115409, Russian Federation
| | - Arthur O Zalevsky
- Faculty of Bioengineering and Bioinformatics, M. V. Lomonosov Moscow State University, Moscow, 119234, Russian Federation
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow, 117997, Russian Federation
| | - Irina A Yushenova
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
| | - Fernando Rodriguez
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
| | - Irina R Arkhipova
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
| | - Aleksey A Penin
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), Moscow, 127051, Russian Federation
| | - Maria D Logacheva
- Skolkovo Institute of Science and Technology, Moscow, 121205, Russian Federation
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), Moscow, 127051, Russian Federation
- A. N. Belozersky Institute of Physico-Chemical Biology, M. V. Lomonosov Moscow State University, Moscow, 119992, Russian Federation
| | - Georgii A Bazykin
- Skolkovo Institute of Science and Technology, Moscow, 121205, Russian Federation
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), Moscow, 127051, Russian Federation
| | - Alexey S Kondrashov
- A. N. Belozersky Institute of Physico-Chemical Biology, M. V. Lomonosov Moscow State University, Moscow, 119992, Russian Federation
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, 48109, USA
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17
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Mizeriene G, Cerny K, Zyka V, Bakonyi J, Nagy ZÁ, Oliva J, Redondo MA, Corcobado T, Martín-García J, Prospero S. Patterns of Genetic Diversification in the Invasive Hybrid Plant Pathogen Phytophthora × alni and Its Parental Species P. uniformis. PHYTOPATHOLOGY 2020; 110:1959-1969. [PMID: 32633698 DOI: 10.1094/phyto-12-19-0475-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In pathogenic fungi and oomycetes, interspecific hybridization may lead to the formation of new species having a greater impact on natural ecosystems than the parental species. From the early 1990s, a severe alder (Alnus spp.) decline due to an unknown Phytophthora species was observed in several European countries. Genetic analyses revealed that the disease was caused by the triploid hybrid P. × alni, which originated in Europe from the hybridization of P. uniformis and P. × multiformis. Here, we investigated the population structure of P. × alni (158 isolates) and P. uniformis (85 isolates) in several European countries using microsatellite markers. Our analyses confirmed the genetic structure previously observed in other European populations, with P. uniformis populations consisting of at most two multilocus genotypes (MLGs) and P. × alni populations dominated by MLG Pxa-1. The genetic structure of P. × alni populations in the Czech Republic, Hungary and Sweden seemed to reflect the physical isolation of river systems. Most rare P. × alni MLGs showed a loss of heterozygosity (LOH) at one or a few microsatellite loci compared with other MLGs. This LOH may allow a stabilization within the P. × alni genome or a rapid adaptation to stress situations. Alternatively, alleles may be lost because of random genetic drift in small, isolated populations, with no effect on fitness of P. × alni. Additional studies would be necessary to confirm these patterns of population diversification and to better understand the factors driving it.
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Affiliation(s)
- Goda Mizeriene
- Swiss Federal Research Institute WSL, Zuercherstrasse 111, CH-8903 Birmensdorf, Switzerland
- Institute of Botany at The Lithuanian State Research Institute Nature Research Centre, Žaliųjų Ežerų Str. 49, LT-08406 Vilnius, Lithuania
| | - Karel Cerny
- The Silva Tarouca Research Institute for Landscape and Ornamental Gardening (RILOG), Květnové náměstí 391, Průhonice 252 43, The Czech Republic
| | - Vladimir Zyka
- The Silva Tarouca Research Institute for Landscape and Ornamental Gardening (RILOG), Květnové náměstí 391, Průhonice 252 43, The Czech Republic
| | - József Bakonyi
- Plant Protection Institute, Centre for Agricultural Research, Herman Ottó Str. 15, H-1022 Budapest, Hungary
| | - Zoltán Árpád Nagy
- Phytophthora Research Centre, Department of Forest Protection and Wildlife Management, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemědělská 3, 61300 Brno, Czech Republic
| | - Jonas Oliva
- Department Crop and Forest Sciences, University of Lleida, Alcalde Rovira Roure 191, 25198, Lleida, Spain
- Joint Research Unit CTFC-Agrotecnio, Alcalde Rovira Roure 191 Lleida, 25198, Spain
| | - Miguel Angel Redondo
- Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 750 07 Uppsala, Sweden
| | - Tamara Corcobado
- Phytophthora Research Centre, Department of Forest Protection and Wildlife Management, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemědělská 3, 61300 Brno, Czech Republic
- Federal Research and Training Centre for Forests, Natural Hazards and Landscape (BFW), Seckendorff-Gudent-Weg 8, 1131 Vienna, Austria
| | - Jorge Martín-García
- Department of Biology, CESAM (Centre for Environmental and Marine Studies), University of Aveiro, Campus Universitario de Santiago, 3810-193 Aveiro, Portugal
- Department of Plant Production and Forest Resources, University of Valladolid, Avenida de Madrid 44, 34071 Palencia, Spain
| | - Simone Prospero
- Swiss Federal Research Institute WSL, Zuercherstrasse 111, CH-8903 Birmensdorf, Switzerland
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18
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Loss of Heterozygosity and Base Mutation Rates Vary Among Saccharomyces cerevisiae Hybrid Strains. G3-GENES GENOMES GENETICS 2020; 10:3309-3319. [PMID: 32727920 PMCID: PMC7466981 DOI: 10.1534/g3.120.401551] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A growing body of evidence suggests that mutation rates exhibit intra-species specific variation. We estimated genome-wide loss of heterozygosity (LOH), gross chromosomal changes, and single nucleotide mutation rates to determine intra-species specific differences in hybrid and homozygous strains of Saccharomyces cerevisiae. The mutation accumulation lines of the S. cerevisiae hybrid backgrounds - S288c/YJM789 (S/Y) and S288c/RM11-1a (S/R) were analyzed along with the homozygous diploids RM11, S288c, and YJM145. LOH was extensive in both S/Y and S/R hybrid backgrounds. The S/Y background also showed longer LOH tracts, gross chromosomal changes, and aneuploidy. Short copy number aberrations were observed in the S/R background. LOH data from the S/Y and S/R hybrids were used to construct a LOH map for S288c to identify hotspots. Further, we observe up to a sixfold difference in single nucleotide mutation rates among the S. cerevisiae S/Y and S/R genetic backgrounds. Our results demonstrate LOH is common during mitotic divisions in S. cerevisiae hybrids and also highlight genome-wide differences in LOH patterns and rates of single nucleotide mutations between commonly used S. cerevisiae hybrid genetic backgrounds.
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19
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Quantifying the Biophysical Impact of Budding Cell Division on the Spatial Organization of Growing Yeast Colonies. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10175780] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Spatial patterns in microbial colonies are the consequence of cell-division dynamics coupled with cell-cell interactions on a physical media. Agent-based models (ABMs) are a powerful tool for understanding the emergence of large scale structure from these individual cell processes. However, most ABMs have focused on fission, a process by which cells split symmetrically into two daughters. The yeast, Saccharomyces cerevisiae, is a model eukaryote which commonly undergoes an asymmetric division process called budding. The resulting mother and daughter cells have unequal sizes and the daughter cell does not inherit the replicative age of the mother. In this work, we develop and analyze an ABM to study the impact of budding cell division and nutrient limitation on yeast colony structure. We find that while budding division does not impact large-scale properties of the colony (such as shape and size), local spatial organization of cells with respect to spatial layout of mother-daughter cell pairs and connectivity of subcolonies is greatly impacted. In addition, we find that nutrient limitation further promotes local spatial organization of cells and changes global colony organization by driving variation in subcolony sizes. Moreover, resulting differences in spatial organization, coupled with differential growth rates from nutrient limitation, create distinct sectoring patterns within growing yeast colonies. Our findings offer novel insights into mechanisms driving experimentally observed sectored yeast colony phenotypes. Furthermore, our work illustrates the need to include relevant biophysical mechanisms when using ABMs to compare to experimental studies.
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20
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Tattini L, Tellini N, Mozzachiodi S, D'Angiolo M, Loeillet S, Nicolas A, Liti G. Accurate Tracking of the Mutational Landscape of Diploid Hybrid Genomes. Mol Biol Evol 2020; 36:2861-2877. [PMID: 31397846 PMCID: PMC6878955 DOI: 10.1093/molbev/msz177] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mutations, recombinations, and genome duplications may promote genetic diversity and trigger evolutionary processes. However, quantifying these events in diploid hybrid genomes is challenging. Here, we present an integrated experimental and computational workflow to accurately track the mutational landscape of yeast diploid hybrids (MuLoYDH) in terms of single-nucleotide variants, small insertions/deletions, copy-number variants, aneuploidies, and loss-of-heterozygosity. Pairs of haploid Saccharomyces parents were combined to generate ancestor hybrids with phased genomes and varying levels of heterozygosity. These diploids were evolved under different laboratory protocols, in particular mutation accumulation experiments. Variant simulations enabled the efficient integration of competitive and standard mapping of short reads, depending on local levels of heterozygosity. Experimental validations proved the high accuracy and resolution of our computational approach. Finally, applying MuLoYDH to four different diploids revealed striking genetic background effects. Homozygous Saccharomyces cerevisiae showed a ∼4-fold higher mutation rate compared with its closely related species S. paradoxus. Intraspecies hybrids unveiled that a substantial fraction of the genome (∼250 bp per generation) was shaped by loss-of-heterozygosity, a process strongly inhibited in interspecies hybrids by high levels of sequence divergence between homologous chromosomes. In contrast, interspecies hybrids exhibited higher single-nucleotide mutation rates compared with intraspecies hybrids. MuLoYDH provided an unprecedented quantitative insight into the evolutionary processes that mold diploid yeast genomes and can be generalized to other genetic systems.
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Affiliation(s)
- Lorenzo Tattini
- CNRS UMR7284, INSERM, IRCAN, Université Côte d'Azur, Nice, France
| | - Nicolò Tellini
- CNRS UMR7284, INSERM, IRCAN, Université Côte d'Azur, Nice, France
| | | | | | - Sophie Loeillet
- CNRS UMR3244, Institut Curie, PSL Research University, Paris, France
| | - Alain Nicolas
- CNRS UMR3244, Institut Curie, PSL Research University, Paris, France
| | - Gianni Liti
- CNRS UMR7284, INSERM, IRCAN, Université Côte d'Azur, Nice, France
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21
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Lawrimore CJ, Bloom K. Common Features of the Pericentromere and Nucleolus. Genes (Basel) 2019; 10:E1029. [PMID: 31835574 PMCID: PMC6947172 DOI: 10.3390/genes10121029] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/05/2019] [Accepted: 12/07/2019] [Indexed: 12/20/2022] Open
Abstract
Both the pericentromere and the nucleolus have unique characteristics that distinguish them amongst the rest of genome. Looping of pericentromeric DNA, due to structural maintenance of chromosome (SMC) proteins condensin and cohesin, drives its ability to maintain tension during metaphase. Similar loops are formed via condensin and cohesin in nucleolar ribosomal DNA (rDNA). Condensin and cohesin are also concentrated in transfer RNA (tRNA) genes, genes which may be located within the pericentromere as well as tethered to the nucleolus. Replication fork stalling, as well as downstream consequences such as genomic recombination, are characteristic of both the pericentromere and rDNA. Furthermore, emerging evidence suggests that the pericentromere may function as a liquid-liquid phase separated domain, similar to the nucleolus. We therefore propose that the pericentromere and nucleolus, in part due to their enrichment of SMC proteins and others, contain similar domains that drive important cellular activities such as segregation, stability, and repair.
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Affiliation(s)
| | - Kerry Bloom
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA;
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22
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Ramos-Pérez C, Dominska M, Anaissi-Afonso L, Cazorla-Rivero S, Quevedo O, Lorenzo-Castrillejo I, Petes TD, Machín F. Cytological and genetic consequences for the progeny of a mitotic catastrophe provoked by Topoisomerase II deficiency. Aging (Albany NY) 2019; 11:11686-11721. [PMID: 31812950 PMCID: PMC6932922 DOI: 10.18632/aging.102573] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 11/24/2019] [Indexed: 02/07/2023]
Abstract
Topoisomerase II (Top2) removes topological linkages between replicated chromosomes. Top2 inhibition leads to mitotic catastrophe (MC) when cells unsuccessfully try to split their genetic material between the two daughter cells. Herein, we have characterized the fate of these daughter cells in the budding yeast. Clonogenic and microcolony experiments, in combination with vital and apoptotic stains, showed that 75% of daughter cells become senescent in the short term; they are unable to divide but remain alive. Decline in cell vitality then occurred, yet slowly, uncoordinatedly when comparing pairs of daughters, and independently of the cell death mediator Mca1/Yca1. Furthermore, we showed that senescence can be modulated by ploidy, suggesting that gross chromosome imbalances during segregation may account for this phenotype. Indeed, we found that diploid long-term survivors of the MC are prone to genomic imbalances such as trisomies, uniparental disomies and terminal loss of heterozygosity (LOH), the latter affecting the longest chromosome arms.
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Affiliation(s)
- Cristina Ramos-Pérez
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.,Escuela de Doctorado y Estudios de Postgrado, Universidad de La Laguna, Tenerife, Spain.,Present address: BenchSci Analytics Inc., Toronto, Canada
| | - Margaret Dominska
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Laura Anaissi-Afonso
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.,Escuela de Doctorado y Estudios de Postgrado, Universidad de La Laguna, Tenerife, Spain
| | - Sara Cazorla-Rivero
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.,Escuela de Doctorado y Estudios de Postgrado, Universidad de La Laguna, Tenerife, Spain
| | - Oliver Quevedo
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.,Present address: Genomic Integrity Unit, Danish Cancer Society Research Center, Copenhagen, Denmark
| | - Isabel Lorenzo-Castrillejo
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Thomas D Petes
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Félix Machín
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.,Instituto de Tecnologías Biomédicas, Universidad de La Laguna, Tenerife, Spain.,Facultad de Ciencias de la Salud, Universidad Fernando Pessoa Canarias, Las Palmas de Gran Canaria, Spain
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23
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Charron G, Marsit S, Hénault M, Martin H, Landry CR. Spontaneous whole-genome duplication restores fertility in interspecific hybrids. Nat Commun 2019; 10:4126. [PMID: 31511504 PMCID: PMC6739354 DOI: 10.1038/s41467-019-12041-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 08/19/2019] [Indexed: 11/21/2022] Open
Abstract
Interspecies hybrids often show some advantages over parents but also frequently suffer from reduced fertility, which can sometimes be overcome through sexual reproduction that sorts out genetic incompatibilities. Sex is however inefficient due to the low viability or fertility of hybrid offspring and thus limits their evolutionary potential. Mitotic cell division could be an alternative to fertility recovery in species such as fungi that can also propagate asexually. Here, to test this, we evolve in parallel and under relaxed selection more than 600 diploid yeast inter-specific hybrids that span from 100,000 to 15 M years of divergence. We find that hybrids can recover fertility spontaneously and rapidly through whole-genome duplication. These events occur in both hybrids between young and well-established species. Our results show that the instability of ploidy in hybrid is an accessible path to spontaneous fertility recovery. Hybridization across species can lead to offspring with reduced fertility. Here, the authors experimentally evolve yeast and show that whole-genome duplication during asexual reproduction can restore fertility in hybrids over a relatively short evolutionary timespan.
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Affiliation(s)
- Guillaume Charron
- Institut de Biologie Intégrative et des Systèmes, 1030 avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.,Regroupement Québécois de Recherche sur la Fonction, l'Ingénierie et les Applications des Protéines, (PROTEO), 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.,Département de biologie, 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada
| | - Souhir Marsit
- Institut de Biologie Intégrative et des Systèmes, 1030 avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.,Regroupement Québécois de Recherche sur la Fonction, l'Ingénierie et les Applications des Protéines, (PROTEO), 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.,Département de biologie, 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.,Département de biochimie, microbiologie et bio-informatique, 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada
| | - Mathieu Hénault
- Institut de Biologie Intégrative et des Systèmes, 1030 avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.,Regroupement Québécois de Recherche sur la Fonction, l'Ingénierie et les Applications des Protéines, (PROTEO), 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.,Département de biochimie, microbiologie et bio-informatique, 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada
| | - Hélène Martin
- Institut de Biologie Intégrative et des Systèmes, 1030 avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.,Regroupement Québécois de Recherche sur la Fonction, l'Ingénierie et les Applications des Protéines, (PROTEO), 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.,Département de biologie, 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.,Département de biochimie, microbiologie et bio-informatique, 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada
| | - Christian R Landry
- Institut de Biologie Intégrative et des Systèmes, 1030 avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada. .,Regroupement Québécois de Recherche sur la Fonction, l'Ingénierie et les Applications des Protéines, (PROTEO), 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada. .,Département de biologie, 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada. .,Département de biochimie, microbiologie et bio-informatique, 1045 Avenue de la Médecine, Université Laval, Québec (Qc), G1V 0A6, Canada.
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24
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Zhang K, Zheng DQ, Sui Y, Qi L, Petes T. Genome-wide analysis of genomic alterations induced by oxidative DNA damage in yeast. Nucleic Acids Res 2019; 47:3521-3535. [PMID: 30668788 PMCID: PMC6468167 DOI: 10.1093/nar/gkz027] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 12/11/2018] [Accepted: 01/15/2019] [Indexed: 12/16/2022] Open
Abstract
Oxidative DNA damage is a threat to genome stability. Using a genetic system in yeast that allows detection of mitotic recombination, we found that the frequency of crossovers is greatly elevated when cells are treated with hydrogen peroxide (H2O2). Using a combination of microarray analysis and genomic sequencing, we mapped the breakpoints of mitotic recombination events and other chromosome rearrangements at a resolution of about 1 kb. Gene conversions and crossovers were the two most common types of events, but we also observed deletions, duplications, and chromosome aneuploidy. In addition, H2O2-treated cells had elevated rates of point mutations (particularly A to T/T to A and C to G/G to C transversions) and small insertions/deletions (in/dels). In cells that underwent multiple rounds of H2O2 treatments, we identified a genetic alteration that resulted in improved H2O2 tolerance by amplification of the CTT1 gene that encodes cytosolic catalase T. Lastly, we showed that cells grown in the absence of oxygen have reduced levels of recombination. This study provided multiple novel insights into how oxidative stress affects genomic instability and phenotypic evolution in aerobic cells.
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Affiliation(s)
- Ke Zhang
- College of Life Science, Zhejiang University, Hangzhou 310058, China
| | - Dao-Qiong Zheng
- Ocean College, Zhejiang University, Zhoushan 316021, China
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Yang Sui
- Ocean College, Zhejiang University, Zhoushan 316021, China
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Lei Qi
- Ocean College, Zhejiang University, Zhoushan 316021, China
| | - Thomas D Petes
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
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25
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Fay JC, Liu P, Ong GT, Dunham MJ, Cromie GA, Jeffery EW, Ludlow CL, Dudley AM. A polyploid admixed origin of beer yeasts derived from European and Asian wine populations. PLoS Biol 2019; 17:e3000147. [PMID: 30835725 PMCID: PMC6400334 DOI: 10.1371/journal.pbio.3000147] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 01/30/2019] [Indexed: 11/18/2022] Open
Abstract
Strains of Saccharomyces cerevisiae used to make beer, bread, and wine are genetically and phenotypically distinct from wild populations associated with trees. The origins of these domesticated populations are not always clear; human-associated migration and admixture with wild populations have had a strong impact on S. cerevisiae population structure. We examined the population genetic history of beer strains and found that ale strains and the S. cerevisiae portion of allotetraploid lager strains were derived from admixture between populations closely related to European grape wine strains and Asian rice wine strains. Similar to both lager and baking strains, ale strains are polyploid, providing them with a passive means of remaining isolated from other populations and providing us with a living relic of their ancestral hybridization. To reconstruct their polyploid origin, we phased the genomes of two ale strains and found ale haplotypes to both be recombinants between European and Asian alleles and to also contain novel alleles derived from extinct or as yet uncharacterized populations. We conclude that modern beer strains are the product of a historical melting pot of fermentation technology.
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Affiliation(s)
- Justin C. Fay
- Department of Biology, University of Rochester, Rochester, New York, United States of America
- Department of Genetics, Washington University, St. Louis, Missouri, United States of America
- * E-mail:
| | - Ping Liu
- Department of Genetics, Washington University, St. Louis, Missouri, United States of America
| | - Giang T. Ong
- Department of Genome Sciences, Seattle, Washington, United States of America
| | - Maitreya J. Dunham
- Department of Genome Sciences, Seattle, Washington, United States of America
| | - Gareth A. Cromie
- Pacific Northwest Research Institute, Seattle, Washington, United States of America
| | - Eric W. Jeffery
- Pacific Northwest Research Institute, Seattle, Washington, United States of America
| | - Catherine L. Ludlow
- Pacific Northwest Research Institute, Seattle, Washington, United States of America
| | - Aimée M. Dudley
- Pacific Northwest Research Institute, Seattle, Washington, United States of America
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26
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Veller C, Kleckner N, Nowak MA. A rigorous measure of genome-wide genetic shuffling that takes into account crossover positions and Mendel's second law. Proc Natl Acad Sci U S A 2019; 116:1659-1668. [PMID: 30635424 PMCID: PMC6358705 DOI: 10.1073/pnas.1817482116] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Comparative studies in evolutionary genetics rely critically on evaluation of the total amount of genetic shuffling that occurs during gamete production. Such studies have been hampered by the absence of a direct measure of this quantity. Existing measures consider crossing-over by simply counting the average number of crossovers per meiosis. This is qualitatively inadequate, because the positions of crossovers along a chromosome are also critical: a crossover toward the middle of a chromosome causes more shuffling than a crossover toward the tip. Moreover, traditional measures fail to consider shuffling from independent assortment of homologous chromosomes (Mendel's second law). Here, we present a rigorous measure of genome-wide shuffling that does not suffer from these limitations. We define the parameter [Formula: see text] as the probability that the alleles at two randomly chosen loci are shuffled during gamete production. This measure can be decomposed into separate contributions from crossover number and position and from independent assortment. Intrinsic implications of this metric include the fact that [Formula: see text] is larger when crossovers are more evenly spaced, which suggests a selective advantage of crossover interference. Utilization of [Formula: see text] is enabled by powerful emergent methods for determining crossover positions either cytologically or by DNA sequencing. Application of our analysis to such data from human male and female reveals that (i) [Formula: see text] in humans is close to its maximum possible value of 1/2 and that (ii) this high level of shuffling is due almost entirely to independent assortment, the contribution of which is ∼30 times greater than that of crossovers.
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Affiliation(s)
- Carl Veller
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138
- Program for Evolutionary Dynamics, Harvard University, Cambridge, MA 02138
| | - Nancy Kleckner
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138;
| | - Martin A Nowak
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138
- Program for Evolutionary Dynamics, Harvard University, Cambridge, MA 02138
- Department of Mathematics, Harvard University, Cambridge, MA 02138
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27
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Klein HL, Bačinskaja G, Che J, Cheblal A, Elango R, Epshtein A, Fitzgerald DM, Gómez-González B, Khan SR, Kumar S, Leland BA, Marie L, Mei Q, Miné-Hattab J, Piotrowska A, Polleys EJ, Putnam CD, Radchenko EA, Saada AA, Sakofsky CJ, Shim EY, Stracy M, Xia J, Yan Z, Yin Y, Aguilera A, Argueso JL, Freudenreich CH, Gasser SM, Gordenin DA, Haber JE, Ira G, Jinks-Robertson S, King MC, Kolodner RD, Kuzminov A, Lambert SAE, Lee SE, Miller KM, Mirkin SM, Petes TD, Rosenberg SM, Rothstein R, Symington LS, Zawadzki P, Kim N, Lisby M, Malkova A. Guidelines for DNA recombination and repair studies: Cellular assays of DNA repair pathways. MICROBIAL CELL (GRAZ, AUSTRIA) 2019; 6:1-64. [PMID: 30652105 PMCID: PMC6334234 DOI: 10.15698/mic2019.01.664] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Revised: 08/29/2018] [Accepted: 09/14/2018] [Indexed: 12/29/2022]
Abstract
Understanding the plasticity of genomes has been greatly aided by assays for recombination, repair and mutagenesis. These assays have been developed in microbial systems that provide the advantages of genetic and molecular reporters that can readily be manipulated. Cellular assays comprise genetic, molecular, and cytological reporters. The assays are powerful tools but each comes with its particular advantages and limitations. Here the most commonly used assays are reviewed, discussed, and presented as the guidelines for future studies.
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Affiliation(s)
- Hannah L. Klein
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Giedrė Bačinskaja
- Department of Biology, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Jun Che
- Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, USA
| | - Anais Cheblal
- Friedrich Miescher Institute for Biomedical Research (FMI), 4058 Basel, Switzerland
| | - Rajula Elango
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Anastasiya Epshtein
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Devon M. Fitzgerald
- Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Belén Gómez-González
- Centro Andaluz de BIología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla, Seville, Spain
| | - Sharik R. Khan
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Sandeep Kumar
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | | | - Léa Marie
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA
| | - Qian Mei
- Systems, Synthetic and Physical Biology Graduate Program, Rice University, Houston, TX, USA
| | - Judith Miné-Hattab
- Institut Curie, PSL Research University, CNRS, UMR3664, F-75005 Paris, France
- Sorbonne Université, Institut Curie, CNRS, UMR3664, F-75005 Paris, France
| | - Alicja Piotrowska
- NanoBioMedical Centre, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland
| | | | - Christopher D. Putnam
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, CA, USA
- Department of Medicine, University of California School of Medicine, San Diego, La Jolla, CA, USA
| | | | - Anissia Ait Saada
- Institut Curie, PSL Research University, CNRS, UMR3348 F-91405, Orsay, France
- University Paris Sud, Paris-Saclay University, CNRS, UMR3348, F-91405, Orsay, France
| | - Cynthia J. Sakofsky
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Durham, NC, USA
| | - Eun Yong Shim
- Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, USA
| | - Mathew Stracy
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Jun Xia
- Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Zhenxin Yan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Yi Yin
- Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, NC USA
| | - Andrés Aguilera
- Centro Andaluz de BIología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla, Seville, Spain
| | - Juan Lucas Argueso
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA
| | - Catherine H. Freudenreich
- Department of Biology, Tufts University, Medford, MA USA
- Program in Genetics, Tufts University, Boston, MA, USA
| | - Susan M. Gasser
- Friedrich Miescher Institute for Biomedical Research (FMI), 4058 Basel, Switzerland
| | - Dmitry A. Gordenin
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Durham, NC, USA
| | - James E. Haber
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center Brandeis University, Waltham, MA, USA
| | - Grzegorz Ira
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Sue Jinks-Robertson
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC USA
| | | | - Richard D. Kolodner
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, CA, USA
- Department of Cellular and Molecular Medicine, University of California School of Medicine, San Diego, La Jolla, CA, USA
- Moores-UCSD Cancer Center, University of California School of Medicine, San Diego, La Jolla, CA, USA
- Institute of Genomic Medicine, University of California School of Medicine, San Diego, La Jolla, CA, USA
| | - Andrei Kuzminov
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Sarah AE Lambert
- Institut Curie, PSL Research University, CNRS, UMR3348 F-91405, Orsay, France
- University Paris Sud, Paris-Saclay University, CNRS, UMR3348, F-91405, Orsay, France
| | - Sang Eun Lee
- Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, USA
| | - Kyle M. Miller
- Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
| | | | - Thomas D. Petes
- Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, NC USA
| | - Susan M. Rosenberg
- Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
- Systems, Synthetic and Physical Biology Graduate Program, Rice University, Houston, TX, USA
| | - Rodney Rothstein
- Department of Genetics & Development, Columbia University Irving Medical Center, New York, NY, USA
| | - Lorraine S. Symington
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA
| | - Pawel Zawadzki
- NanoBioMedical Centre, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland
| | - Nayun Kim
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Michael Lisby
- Department of Biology, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Anna Malkova
- Department of Biology, University of Iowa, Iowa City, IA, USA
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28
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Zheng DQ, Petes TD. Genome Instability Induced by Low Levels of Replicative DNA Polymerases in Yeast. Genes (Basel) 2018; 9:genes9110539. [PMID: 30405078 PMCID: PMC6267110 DOI: 10.3390/genes9110539] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 11/04/2018] [Accepted: 11/05/2018] [Indexed: 11/29/2022] Open
Abstract
Most cells of solid tumors have very high levels of genome instability of several different types, including deletions, duplications, translocations, and aneuploidy. Much of this instability appears induced by DNA replication stress. As a model for understanding this type of instability, we have examined genome instability in yeast strains that have low levels of two of the replicative DNA polymerases: DNA polymerase α and DNA polymerase δ (Polα and Polδ). We show that low levels of either of these DNA polymerases results in greatly elevated levels of mitotic recombination, chromosome rearrangements, and deletions/duplications. The spectrum of events in the two types of strains, however, differs in a variety of ways. For example, a reduced level of Polδ elevates single-base alterations and small deletions considerably more than a reduced level of Polα. In this review, we will summarize the methods used to monitor genome instability in yeast, and how this analysis contributes to understanding the linkage between genome instability and DNA replication stress.
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Affiliation(s)
- Dao-Qiong Zheng
- Ocean College, Zhejiang University, Zhoushan 316021, Zhejiang, China.
| | - Thomas D Petes
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA.
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29
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Sexual ancestors generated an obligate asexual and globally dispersed clone within the model diatom species Thalassiosira pseudonana. Sci Rep 2018; 8:10492. [PMID: 30002405 PMCID: PMC6043606 DOI: 10.1038/s41598-018-28630-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 06/26/2018] [Indexed: 12/02/2022] Open
Abstract
Sexual reproduction roots the eukaryotic tree of life, although its loss occurs across diverse taxa. Asexual reproduction and clonal lineages persist in these taxa despite theoretical arguments suggesting that individual clones should be evolutionarily short-lived due to limited phenotypic diversity. Here, we present quantitative evidence that an obligate asexual lineage emerged from a sexual population of the marine diatom Thalassiosira pseudonana and rapidly expanded throughout the world’s oceans. Whole genome comparisons identified two lineages with characteristics expected of sexually reproducing strains in Hardy-Weinberg equilibrium. A third lineage displays genomic signatures for the functional loss of sexual reproduction followed by a recent global colonization by a single ancestral genotype. Extant members of this lineage are genetically differentiated and phenotypically plastic, potentially allowing for rapid adaptation when they are challenged by natural selection. Such mechanisms may be expected to generate new clones within marginal populations of additional unicellular species, facilitating the exploration and colonization of novel environments, aided by exponential growth and ease of dispersal.
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30
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Genetic Control of Genomic Alterations Induced in Yeast by Interstitial Telomeric Sequences. Genetics 2018; 209:425-438. [PMID: 29610215 PMCID: PMC5972418 DOI: 10.1534/genetics.118.300950] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 03/27/2018] [Indexed: 11/23/2022] Open
Abstract
In many organisms, telomeric sequences can be located internally on the chromosome in addition to their usual positions at the ends of the chromosome. In humans, such interstitial telomeric sequences (ITSs) are nonrandomly associated with translocation breakpoints in tumor cells and with chromosome fragile sites (regions of the chromosome that break in response to perturbed DNA replication). We previously showed that ITSs in yeast generated several different types of instability, including terminal inversions (recombination between the ITS and the “true” chromosome telomere) and point mutations in DNA sequences adjacent to the ITS. In the current study, we examine the genetic control of these events. We show that the terminal inversions occur by the single-strand annealing pathway of DNA repair following the formation of a double-stranded DNA break within the ITS. The point mutations induced by the ITS require the error-prone DNA polymerase ζ. Unlike the terminal inversions, these events are not initiated by a double-stranded DNA break, but likely result from the error-prone repair of a single-stranded DNA gap or recruitment of DNA polymerase ζ in the absence of DNA damage.
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31
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Nowell RW, Almeida P, Wilson CG, Smith TP, Fontaneto D, Crisp A, Micklem G, Tunnacliffe A, Boschetti C, Barraclough TG. Comparative genomics of bdelloid rotifers: Insights from desiccating and nondesiccating species. PLoS Biol 2018; 16:e2004830. [PMID: 29689044 PMCID: PMC5916493 DOI: 10.1371/journal.pbio.2004830] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Accepted: 03/19/2018] [Indexed: 12/22/2022] Open
Abstract
Bdelloid rotifers are a class of microscopic invertebrates that have existed for millions of years apparently without sex or meiosis. They inhabit a variety of temporary and permanent freshwater habitats globally, and many species are remarkably tolerant of desiccation. Bdelloids offer an opportunity to better understand the evolution of sex and recombination, but previous work has emphasised desiccation as the cause of several unusual genomic features in this group. Here, we present high-quality whole-genome sequences of 3 bdelloid species: Rotaria macrura and R. magnacalcarata, which are both desiccation intolerant, and Adineta ricciae, which is desiccation tolerant. In combination with the published assembly of A. vaga, which is also desiccation tolerant, we apply a comparative genomics approach to evaluate the potential effects of desiccation tolerance and asexuality on genome evolution in bdelloids. We find that ancestral tetraploidy is conserved among all 4 bdelloid species, but homologous divergence in obligately aquatic Rotaria genomes is unexpectedly low. This finding is contrary to current models regarding the role of desiccation in shaping bdelloid genomes. In addition, we find that homologous regions in A. ricciae are largely collinear and do not form palindromic repeats as observed in the published A. vaga assembly. Consequently, several features interpreted as genomic evidence for long-term ameiotic evolution are not general to all bdelloid species, even within the same genus. Finally, we substantiate previous findings of high levels of horizontally transferred nonmetazoan genes in both desiccating and nondesiccating bdelloid species and show that this unusual feature is not shared by other animal phyla, even those with desiccation-tolerant representatives. These comparisons call into question the proposed role of desiccation in mediating horizontal genetic transfer.
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Affiliation(s)
- Reuben W. Nowell
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, United Kingdom
| | - Pedro Almeida
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, United Kingdom
| | - Christopher G. Wilson
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, United Kingdom
| | - Thomas P. Smith
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, United Kingdom
| | - Diego Fontaneto
- National Research Council of Italy, Institute of Ecosystem Study, Verbania Pallanza, Italy
| | - Alastair Crisp
- Department of Chemical Engineering and Biotechnology, West Cambridge Site, University of Cambridge, Cambridge, United Kingdom
| | - Gos Micklem
- Department of Genetics, Cambridge Systems Biology Centre, Downing Site, University of Cambridge, Cambridge, United Kingdom
| | - Alan Tunnacliffe
- Department of Chemical Engineering and Biotechnology, West Cambridge Site, University of Cambridge, Cambridge, United Kingdom
| | - Chiara Boschetti
- Department of Chemical Engineering and Biotechnology, West Cambridge Site, University of Cambridge, Cambridge, United Kingdom
- School of Biological and Marine Sciences, Plymouth University, Portland Square Building, Plymouth, United Kingdom
| | - Timothy G. Barraclough
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, United Kingdom
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32
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Genome Dynamics of Hybrid Saccharomyces cerevisiae During Vegetative and Meiotic Divisions. G3-GENES GENOMES GENETICS 2017; 7:3669-3679. [PMID: 28916648 PMCID: PMC5677154 DOI: 10.1534/g3.117.1135] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Mutation and recombination are the major sources of genetic diversity in all organisms. In the baker’s yeast, all mutation rate estimates are in homozygous background. We determined the extent of genetic change through mutation and loss of heterozygosity (LOH) in a heterozygous Saccharomyces cerevisiae genome during successive vegetative and meiotic divisions. We measured genome-wide LOH and base mutation rates during vegetative and meiotic divisions in a hybrid (S288c/YJM789) S. cerevisiae strain. The S288c/YJM789 hybrid showed nearly complete reduction in heterozygosity within 31 generations of meioses and improved spore viability. LOH in the meiotic lines was driven primarily by the mating of spores within the tetrad. The S288c/YJM789 hybrid lines propagated vegetatively for the same duration as the meiotic lines, showed variable LOH (from 2 to 3% and up to 35%). Two of the vegetative lines with extensive LOH showed frequent and large internal LOH tracts that suggest a high frequency of recombination repair. These results suggest significant LOH can occur in the S288c/YJM789 hybrid during vegetative propagation presumably due to return to growth events. The average base substitution rates for the vegetative lines (1.82 × 10−10 per base per division) and the meiotic lines (1.22 × 10−10 per base per division) are the first genome-wide mutation rate estimates for a hybrid yeast. This study therefore provides a novel context for the analysis of mutation rates (especially in the context of detecting LOH during vegetative divisions), compared to previous mutation accumulation studies in yeast that used homozygous backgrounds.
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Increased LOH due to Defective Sister Chromatid Cohesion Is due Primarily to Chromosomal Aneuploidy and not Recombination. G3-GENES GENOMES GENETICS 2017; 7:3305-3315. [PMID: 28983067 PMCID: PMC5633381 DOI: 10.1534/g3.117.300091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Loss of heterozygosity (LOH) is an important factor in cancer, pathogenic fungi, and adaptation to changing environments. The sister chromatid cohesion process (SCC) suppresses aneuploidy and therefore whole chromosome LOH. SCC is also important to channel recombinational repair to sister chromatids, thereby preventing LOH mediated by allelic recombination. There is, however, insufficient information about the relative roles that the SCC pathway plays in the different modes of LOH. Here, we found that the cohesin mutation mcd1-1, and other mutations in SCC, differentially affect the various types of LOH. The greatest effect, by three orders of magnitude, was on whole chromosome loss (CL). In contrast, there was little increase in recombination-mediated LOH, even for telomeric markers. Some of the LOH events that were increased by SCC mutations were complex, i.e., they were the result of several chromosome transactions. Although these events were independent of POL32, the most parsimonious way to explain the formation of at least some of them was break-induced replication through the centromere. Interestingly, the mcd1-1 pol32Δ double mutant showed a significant reduction in the rate of CL in comparison with the mcd1-1 single mutant. Our results show that defects in SCC allow the formation of complex LOH events that, in turn, can promote drug or pesticide resistance in diploid microbes that are pathogenic to humans or plants.
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34
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Mitotic Gene Conversion Tracts Associated with Repair of a Defined Double-Strand Break in Saccharomyces cerevisiae. Genetics 2017; 207:115-128. [PMID: 28743762 DOI: 10.1534/genetics.117.300057] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 07/18/2017] [Indexed: 11/18/2022] Open
Abstract
Mitotic recombination between homologous chromosomes leads to the uncovering of recessive alleles through loss of heterozygosity. In the current study, a defined double-strand break was used to initiate reciprocal loss of heterozygosity between diverged homologs of chromosome IV in Saccharomyces cerevisiae These events resulted from the repair of two broken chromatids, one of which was repaired as a crossover and the other as a noncrossover. Associated gene conversion tracts resulting from the donor-directed repair of mismatches formed during strand exchange (heteroduplex DNA) were mapped using microarrays. Gene conversion tracts associated with individual crossover and noncrossover events were similar in size and position, with half of the tracts being unidirectional and mapping to only one side of the initiating break. Among crossover events, this likely reflected gene conversion on only one side of the break, with restoration-type repair occurring on the other side. For noncrossover events, an ectopic system was used to directly compare gene conversion tracts produced in a wild-type strain to heteroduplex DNA tracts generated in the absence of the Mlh1 mismatch-repair protein. There was a strong bias for unidirectional tracts in the absence, but not in the presence, of Mlh1 This suggests that mismatch repair acts on heteroduplex DNA that is only transiently present in noncrossover intermediates of the synthesis dependent strand annealing pathway. Although the molecular features of events associated with loss of heterozygosity generally agreed with those predicted by current recombination models, there were unexpected complexities in associated gene conversion tracts.
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Yin Y, Dominska M, Yim E, Petes TD. High-resolution mapping of heteroduplex DNA formed during UV-induced and spontaneous mitotic recombination events in yeast. eLife 2017; 6. [PMID: 28714850 PMCID: PMC5531827 DOI: 10.7554/elife.28069] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 07/14/2017] [Indexed: 12/13/2022] Open
Abstract
In yeast, DNA breaks are usually repaired by homologous recombination (HR). An early step for HR pathways is formation of a heteroduplex, in which a single-strand from the broken DNA molecule pairs with a strand derived from an intact DNA molecule. If the two strands of DNA are not identical, there will be mismatches within the heteroduplex DNA (hetDNA). In wild-type strains, these mismatches are repaired by the mismatch repair (MMR) system, producing a gene conversion event. In strains lacking MMR, the mismatches persist. Most previous studies involving hetDNA formed during mitotic recombination were restricted to one locus. Below, we present a global mapping of hetDNA formed in the MMR-defective mlh1 strain. We find that many recombination events are associated with repair of double-stranded DNA gaps and/or involve Mlh1-independent mismatch repair. Many of our events are not explicable by the simplest form of the double-strand break repair model of recombination. DOI:http://dx.doi.org/10.7554/eLife.28069.001
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Affiliation(s)
- Yi Yin
- Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, United States
| | - Margaret Dominska
- Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, United States
| | - Eunice Yim
- Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, United States
| | - Thomas D Petes
- Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, United States
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Marroni F, Scaglione D, Pinosio S, Policriti A, Miculan M, Di Gaspero G, Morgante M. Reduction of heterozygosity (ROH) as a method to detect mosaic structural variation. PLANT BIOTECHNOLOGY JOURNAL 2017; 15:791-793. [PMID: 28055146 PMCID: PMC5466433 DOI: 10.1111/pbi.12691] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 12/21/2016] [Accepted: 12/29/2016] [Indexed: 05/06/2023]
Affiliation(s)
- Fabio Marroni
- Dipartimento di Scienze agroalimentari, ambientali e animaliUniversità di UdineUdineItaly
- Istituto di Genomica Applicata (IGA)UdineItaly
| | - Davide Scaglione
- IGA Technology ServicesUdineItaly
- Parco Tecnologico PadanoLodiItaly
| | - Sara Pinosio
- Istituto di Genomica Applicata (IGA)UdineItaly
- Institute of Biosciences and BioresourcesNational Research CouncilSesto Fiorentino (Firenze)Italy
- Present address: Dipartimento di Scienze agroalimentari, ambientali e animaliUniversità di UdineVia delle Scienze 206Udine33100Italy
| | - Alberto Policriti
- Istituto di Genomica Applicata (IGA)UdineItaly
- Department of Mathematics and Computer ScienceUniversity of UdineUdineItaly
| | - Mara Miculan
- Dipartimento di Scienze agroalimentari, ambientali e animaliUniversità di UdineUdineItaly
- Istituto di Genomica Applicata (IGA)UdineItaly
| | | | - Michele Morgante
- Dipartimento di Scienze agroalimentari, ambientali e animaliUniversità di UdineUdineItaly
- Istituto di Genomica Applicata (IGA)UdineItaly
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Properties of Mitotic and Meiotic Recombination in the Tandemly-Repeated CUP1 Gene Cluster in the Yeast Saccharomyces cerevisiae. Genetics 2017; 206:785-800. [PMID: 28381587 PMCID: PMC5499186 DOI: 10.1534/genetics.117.201285] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 03/24/2017] [Indexed: 11/24/2022] Open
Abstract
In the yeast Saccharomyces cerevisiae, the genes encoding the metallothionein protein Cup1 are located in a tandem array on chromosome VIII. Using a diploid strain that is heterozygous for an insertion of a selectable marker (URA3) within this tandem array, and heterozygous for markers flanking the array, we measured interhomolog recombination and intra/sister chromatid exchange in the CUP1 locus. The rate of intra/sister chromatid recombination exceeded the rate of interhomolog recombination by >10-fold. Loss of the Rad51 and Rad52 proteins, required for most interhomolog recombination, led to a relatively small reduction of recombination in the CUP1 array. Although interhomolog mitotic recombination in the CUP1 locus is elevated relative to the average genomic region, we found that interhomolog meiotic recombination in the array is reduced compared to most regions. Lastly, we showed that high levels of copper (previously shown to elevate CUP1 transcription) lead to a substantial elevation in rate of both interhomolog and intra/sister chromatid recombination in the CUP1 array; recombination events that delete the URA3 insertion from the CUP1 array occur at a rate of >10−3/division in unselected cells. This rate is almost three orders of magnitude higher than observed for mitotic recombination events involving single-copy genes. In summary, our study shows that some of the basic properties of recombination differ considerably between single-copy and tandemly-repeated genes.
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Pollmann H, Breitenbach J, Sandmann G. Development of Xanthophyllomyces dendrorhous as a production system for the colorless carotene phytoene. J Biotechnol 2017; 247:34-41. [DOI: 10.1016/j.jbiotec.2017.02.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Revised: 02/17/2017] [Accepted: 02/26/2017] [Indexed: 12/11/2022]
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Drozdova P, Mironova L, Zhouravleva G. Haploid yeast cells undergo a reversible phenotypic switch associated with chromosome II copy number. BMC Genet 2016; 17:152. [PMID: 28105933 PMCID: PMC5249023 DOI: 10.1186/s12863-016-0464-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND SUP35 and SUP45 are essential genes encoding polypeptide chain release factors. However, mutants for these genes may be viable but display pleiotropic phenotypes which include, but are not limited to, nonsense suppressor phenotype due to translation termination defect. [PSI +] prion formation is another Sup35p-associated mechanism leading to nonsense suppression through decreased availability of functional Sup35p. [PSI +] differs from genuine sup35 mutations by the possibility of its elimination and subsequent re-induction. Some suppressor sup35 mutants had also been shown to undergo a reversible phenotypic switch in the opposite direction. This reversible switching had been attributed to a prion termed [ISP +]. However, even though many phenotypic and molecular level features of [ISP +] were revealed, the mechanism behind this phenomenon has not been clearly explained and might be more complex than suggested initially. RESULTS Here we took a genomic approach to look into the molecular basis of the difference between the suppressor (Isp-) and non-suppressor (Isp+) phenotypes. We report that the reason for the difference between the Isp+ and the Isp- phenotypes is chromosome II copy number changes and support our finding with showing that these changes are indeed reversible by reproducing the phenotypic switch and tracking karyotypic changes. Finally, we suggest mechanisms that mediate elevation in nonsense suppression efficiency upon amplification of chromosome II and facilitate switching between these states. CONCLUSIONS (i) In our experimental system, amplification of chromosome II confers nonsense suppressor phenotype and guanidine hydrochloride resistance at the cost of overall decreased viability in rich medium. (ii) SFP1 might represent a novel regulator of chromosome stability, as SFP1 overexpression elevates frequency of the additional chromosome loss in our system. (iii) Prolonged treatment with guanidine hydrochloride leads to selection of resistant isolates, some of which are disomic for chromosome II.
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Affiliation(s)
- Polina Drozdova
- Department of Genetics and Biotechnology, St. Petersburg State University, 199034, Universitetskaya nab. 7-9, St. Petersburg, Russia
| | - Ludmila Mironova
- Department of Genetics and Biotechnology, St. Petersburg State University, 199034, Universitetskaya nab. 7-9, St. Petersburg, Russia
| | - Galina Zhouravleva
- Department of Genetics and Biotechnology, St. Petersburg State University, 199034, Universitetskaya nab. 7-9, St. Petersburg, Russia
- Laboratory of Amyloid Biology, St. Petersburg State University, 199034, Universitetskaya nab. 7-9, St. Petersburg, Russia
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Abstract
Somatic recombination is essential to protect genomes of somatic cells from DNA damage but it also has important clinical implications, as it is a driving force of tumorigenesis leading to inactivation of tumor suppressor genes. Despite this importance, our knowledge about somatic recombination in adult tissues remains very limited. Our recent work, using the Drosophila adult midgut has demonstrated that spontaneous events of mitotic recombination accumulate in aging adult intestinal stem cells and result in frequent loss of heterozygosity (LOH). In this Extra View article, we provide further data supporting long-track chromosome LOH and discuss potential mechanisms involved in the process. In addition, we further discuss relevant questions surrounding somatic recombination and how the mechanisms and factors influencing somatic recombination in adult tissues can be explored using the Drosophila midgut model.
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Affiliation(s)
- Katarzyna Siudeja
- a Institut Curie, PSL Research University, CNRS UMR 3215, INSERM U934, Stem Cells and Tissue Homeostasis group , Paris , France , Sorbonne Universités, UPMC Univ Paris 6 , Paris , France
| | - Allison J Bardin
- a Institut Curie, PSL Research University, CNRS UMR 3215, INSERM U934, Stem Cells and Tissue Homeostasis group , Paris , France , Sorbonne Universités, UPMC Univ Paris 6 , Paris , France
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Chumki SA, Dunn MK, Coates TF, Mishler JD, Younkin EM, Casper AM. Remarkably Long-Tract Gene Conversion Induced by Fragile Site Instability in Saccharomyces cerevisiae. Genetics 2016; 204:115-28. [PMID: 27343237 PMCID: PMC5012379 DOI: 10.1534/genetics.116.191205] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 06/23/2016] [Indexed: 01/29/2023] Open
Abstract
Replication stress causes breaks at chromosomal locations called common fragile sites. Deletions causing loss of heterozygosity (LOH) in human tumors are strongly correlated with common fragile sites, but the role of gene conversion in LOH at fragile sites in tumors is less well studied. Here, we investigated gene conversion stimulated by instability at fragile site FS2 in the yeast Saccharomyces cerevisiae In our screening system, mitotic LOH events near FS2 are identified by production of red/white sectored colonies. We analyzed single nucleotide polymorphisms between homologs to determine the cause and extent of LOH. Instability at FS2 increases gene conversion 48- to 62-fold, and conversions unassociated with crossover represent 6-7% of LOH events. Gene conversion can result from repair of mismatches in heteroduplex DNA during synthesis-dependent strand annealing (SDSA), double-strand break repair (DSBR), and from break-induced replication (BIR) that switches templates [double BIR (dBIR)]. It has been proposed that SDSA and DSBR typically result in shorter gene-conversion tracts than dBIR. In cells under replication stress, we found that bidirectional tracts at FS2 have a median length of 40.8 kb and a wide distribution of lengths; most of these tracts are not crossover-associated. Tracts that begin at the fragile site FS2 and extend only distally are significantly shorter. The high abundance and long length of noncrossover, bidirectional gene-conversion tracts suggests that dBIR is a prominent mechanism for repair of lesions at FS2, thus this mechanism is likely to be a driver of common fragile site-stimulated LOH in human tumors.
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Affiliation(s)
- Shahana A Chumki
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
| | - Mikael K Dunn
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
| | - Thomas F Coates
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
| | - Jeanmarie D Mishler
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
| | - Ellen M Younkin
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
| | - Anne M Casper
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
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Phenotypic Consequences of a Spontaneous Loss of Heterozygosity in a Common Laboratory Strain of Candida albicans. Genetics 2016; 203:1161-76. [PMID: 27206717 DOI: 10.1534/genetics.116.189274] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 05/17/2016] [Indexed: 11/18/2022] Open
Abstract
By testing the susceptibility to DNA damaging agents of several Candida albicans mutant strains derived from the commonly used laboratory strain, CAI4, we uncovered sensitivity to methyl methanesulfonate (MMS) in CAI4 and its derivatives, but not in CAF2-1. This sensitivity is not a result of URA3 disruption because the phenotype was not restored after URA3 reintroduction. Rather, we found that homozygosis of a short region of chromosome 3R (Chr3R), which is naturally heterozygous in the MMS-resistant-related strains CAF4-2 and CAF2-1, confers MMS sensitivity and modulates growth polarization in response to MMS. Furthermore, induction of homozygosity in this region in CAF2-1 or CAF4-2 resulted in MMS sensitivity. We identified 11 genes by SNP/comparative genomic hybridization containing only the a alleles in all the MMS-sensitive strains. Four candidate genes, SNF5, POL1, orf19.5854.1, and MBP1, were analyzed by generating hemizygous configurations in CAF2-1 and CAF4-2 for each allele of all four genes. Only hemizygous MBP1a/mbp1b::SAT1-FLIP strains became MMS sensitive, indicating that MBP1a in the homo- or hemizygosis state was sufficient to account for the MMS-sensitive phenotype. In yeast, Mbp1 regulates G1/S genes involved in DNA repair. A second region of homozygosis on Chr2L increased MMS sensitivity in CAI4 (Chr3R homozygous) but not CAF4-2 (Chr3R heterozygous). This is the first example of sign epistasis in C. albicans.
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Andersen SL, Zhang A, Dominska M, Moriel-Carretero M, Herrera-Moyano E, Aguilera A, Petes TD. High-Resolution Mapping of Homologous Recombination Events in rad3 Hyper-Recombination Mutants in Yeast. PLoS Genet 2016; 12:e1005938. [PMID: 26968037 PMCID: PMC4788294 DOI: 10.1371/journal.pgen.1005938] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 02/24/2016] [Indexed: 11/18/2022] Open
Abstract
The Saccharomyces cerevisae RAD3 gene is the homolog of human XPD, an essential gene encoding a DNA helicase of the TFIIH complex involved in both nucleotide excision repair (NER) and transcription. Some mutant alleles of RAD3 (rad3-101 and rad3-102) have partial defects in DNA repair and a strong hyper-recombination (hyper-Rec) phenotype. Previous studies showed that the hyper-Rec phenotype associated with rad3-101 and rad3-102 can be explained as a consequence of persistent single-stranded DNA gaps that are converted to recombinogenic double-strand breaks (DSBs) by replication. The systems previously used to characterize the hyper-Rec phenotype of rad3 strains do not detect the reciprocal products of mitotic recombination. We have further characterized these events using a system in which the reciprocal products of mitotic recombination are recovered. Both rad3-101 and rad3-102 elevate the frequency of reciprocal crossovers about 100-fold. Mapping of these events shows that three-quarters of these crossovers reflect DSBs formed at the same positions in both sister chromatids (double sister-chromatid breaks, DSCBs). The remainder reflects DSBs formed in single chromatids (single chromatid breaks, SCBs). The ratio of DSCBs to SCBs is similar to that observed for spontaneous recombination events in wild-type cells. We mapped 216 unselected genomic alterations throughout the genome including crossovers, gene conversions, deletions, and duplications. We found a significant association between the location of these recombination events and regions with elevated gamma-H2AX. In addition, there was a hotspot for deletions and duplications at the IMA2 and HXT11 genes near the left end of chromosome XV. A comparison of these data with our previous analysis of spontaneous mitotic recombination events suggests that a sub-set of spontaneous events in wild-type cells may be initiated by incomplete NER reactions, and that DSCBs, which cannot be repaired by sister-chromatid recombination, are a major source of mitotic recombination between homologous chromosomes.
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Affiliation(s)
- Sabrina L. Andersen
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, United States of America
| | - Aimee Zhang
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, United States of America
| | - Margaret Dominska
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, United States of America
| | - María Moriel-Carretero
- Department of Molecular Biology, Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER-Universidad de Sevilla, Seville, Spain
| | - Emilia Herrera-Moyano
- Department of Molecular Biology, Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER-Universidad de Sevilla, Seville, Spain
| | - Andrés Aguilera
- Department of Molecular Biology, Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER-Universidad de Sevilla, Seville, Spain
| | - Thomas D. Petes
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, United States of America
- * E-mail:
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Laureau R, Loeillet S, Salinas F, Bergström A, Legoix-Né P, Liti G, Nicolas A. Extensive Recombination of a Yeast Diploid Hybrid through Meiotic Reversion. PLoS Genet 2016; 12:e1005781. [PMID: 26828862 PMCID: PMC4734685 DOI: 10.1371/journal.pgen.1005781] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 12/09/2015] [Indexed: 11/18/2022] Open
Abstract
In somatic cells, recombination between the homologous chromosomes followed by equational segregation leads to loss of heterozygosity events (LOH), allowing the expression of recessive alleles and the production of novel allele combinations that are potentially beneficial upon Darwinian selection. However, inter-homolog recombination in somatic cells is rare, thus reducing potential genetic variation. Here, we explored the property of S. cerevisiae to enter the meiotic developmental program, induce meiotic Spo11-dependent double-strand breaks genome-wide and return to mitotic growth, a process known as Return To Growth (RTG). Whole genome sequencing of 36 RTG strains derived from the hybrid S288c/SK1 diploid strain demonstrates that the RTGs are bona fide diploids with mosaic recombined genome, derived from either parental origin. Individual RTG genome-wide genotypes are comprised of 5 to 87 homozygous regions due to the loss of heterozygous (LOH) events of various lengths, varying between a few nucleotides up to several hundred kilobases. Furthermore, we show that reiteration of the RTG process shows incremental increases of homozygosity. Phenotype/genotype analysis of the RTG strains for the auxotrophic and arsenate resistance traits validates the potential of this procedure of genome diversification to rapidly map complex traits loci (QTLs) in diploid strains without undergoing sexual reproduction.
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Affiliation(s)
- Raphaëlle Laureau
- Institut Curie, PSL Research University, CNRS, UMR 3244, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 3244, Paris, France
| | - Sophie Loeillet
- Institut Curie, PSL Research University, CNRS, UMR 3244, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 3244, Paris, France
| | - Francisco Salinas
- Institute of Research on Cancer and Ageing of Nice (IRCAN), CNRS UMR 7284-INSERM U1081, Faculté de Médecine, Université de Nice Sophia Antipolis, Nice, France
| | - Anders Bergström
- Institute of Research on Cancer and Ageing of Nice (IRCAN), CNRS UMR 7284-INSERM U1081, Faculté de Médecine, Université de Nice Sophia Antipolis, Nice, France
| | - Patricia Legoix-Né
- Institut Curie, PSL Research University, Next Generation Sequencing Platform, Paris, France
| | - Gianni Liti
- Institute of Research on Cancer and Ageing of Nice (IRCAN), CNRS UMR 7284-INSERM U1081, Faculté de Médecine, Université de Nice Sophia Antipolis, Nice, France
| | - Alain Nicolas
- Institut Curie, PSL Research University, CNRS, UMR 3244, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 3244, Paris, France
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Samyn DR, Persson BL. Inorganic Phosphate and Sulfate Transport in S. cerevisiae. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 892:253-269. [PMID: 26721277 DOI: 10.1007/978-3-319-25304-6_10] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Inorganic ions such as phosphate and sulfate are essential macronutrients required for a broad spectrum of cellular functions and their regulation. In a constantly fluctuating environment microorganisms have for their survival developed specific nutrient sensing and transport systems ensuring that the cellular nutrient needs are met. This chapter focuses on the S. cerevisiae plasma membrane localized transporters, of which some are strongly induced under conditions of nutrient scarcity and facilitate the active uptake of inorganic phosphate and sulfate. Recent advances in studying the properties of the high-affinity phosphate and sulfate transporters by means of site-directed mutagenesis have provided further insight into the molecular mechanisms contributing to substrate selectivity and transporter functionality of this important class of membrane transporters.
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Affiliation(s)
- D R Samyn
- Department of Chemistry and Biomedical Sciences, Centre for Biomaterials Chemistry, Linnaeus University, 391 82, Kalmar, Sweden.
| | - B L Persson
- Department of Chemistry and Biomedical Sciences, Centre for Biomaterials Chemistry, Linnaeus University, 391 82, Kalmar, Sweden
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46
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Abstract
Homology-dependent exchange of genetic information between DNA molecules has a profound impact on the maintenance of genome integrity by facilitating error-free DNA repair, replication, and chromosome segregation during cell division as well as programmed cell developmental events. This chapter will focus on homologous mitotic recombination in budding yeast Saccharomyces cerevisiae. However, there is an important link between mitotic and meiotic recombination (covered in the forthcoming chapter by Hunter et al. 2015) and many of the functions are evolutionarily conserved. Here we will discuss several models that have been proposed to explain the mechanism of mitotic recombination, the genes and proteins involved in various pathways, the genetic and physical assays used to discover and study these genes, and the roles of many of these proteins inside the cell.
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47
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The Transient Inactivation of the Master Cell Cycle Phosphatase Cdc14 Causes Genomic Instability in Diploid Cells of Saccharomyces cerevisiae. Genetics 2015; 200:755-69. [PMID: 25971663 DOI: 10.1534/genetics.115.177626] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 05/07/2015] [Indexed: 11/18/2022] Open
Abstract
Genomic instability is a common feature found in cancer cells . Accordingly, many tumor suppressor genes identified in familiar cancer syndromes are involved in the maintenance of the stability of the genome during every cell division and are commonly referred to as caretakers. Inactivating mutations and epigenetic silencing of caretakers are thought to be the most important mechanisms that explain cancer-related genome instability. However, little is known of whether transient inactivation of caretaker proteins could trigger genome instability and, if so, what types of instability would occur. In this work, we show that a brief and reversible inactivation, during just one cell cycle, of the key phosphatase Cdc14 in the model organism Saccharomyces cerevisiae is enough to result in diploid cells with multiple gross chromosomal rearrangements and changes in ploidy. Interestingly, we observed that such transient loss yields a characteristic fingerprint whereby trisomies are often found in small-sized chromosomes, and gross chromosome rearrangements, often associated with concomitant loss of heterozygosity, are detected mainly on the ribosomal DNA-bearing chromosome XII. Taking into account the key role of Cdc14 in preventing anaphase bridges, resetting replication origins, and controlling spindle dynamics in a well-defined window within anaphase, we speculate that the transient loss of Cdc14 activity causes cells to go through a single mitotic catastrophe with irreversible consequences for the genome stability of the progeny.
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48
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Absence of heterozygosity due to template switching during replicative rearrangements. Am J Hum Genet 2015; 96:555-64. [PMID: 25799105 DOI: 10.1016/j.ajhg.2015.01.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 01/30/2015] [Indexed: 10/23/2022] Open
Abstract
We investigated complex genomic rearrangements (CGRs) consisting of triplication copy-number variants (CNVs) that were accompanied by extended regions of copy-number-neutral absence of heterozygosity (AOH) in subjects with multiple congenital abnormalities. Molecular analyses provided observational evidence that in humans, post-zygotically generated CGRs can lead to regional uniparental disomy (UPD) due to template switches between homologs versus sister chromatids by using microhomology to prime DNA replication-a prediction of the replicative repair model, MMBIR. Our findings suggest that replication-based mechanisms might underlie the formation of diverse types of genomic alterations (CGRs and AOH) implicated in constitutional disorders.
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49
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Genome-destabilizing effects associated with top1 loss or accumulation of top1 cleavage complexes in yeast. PLoS Genet 2015; 11:e1005098. [PMID: 25830313 PMCID: PMC4382028 DOI: 10.1371/journal.pgen.1005098] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 02/23/2015] [Indexed: 12/29/2022] Open
Abstract
Topoisomerase 1 (Top1), a Type IB topoisomerase, functions to relieve transcription- and replication-associated torsional stress in DNA. We investigated the effects of Top1 on genome stability in Saccharomyces cerevisiae using two different assays. First, a sectoring assay that detects loss of heterozygosity (LOH) on a specific chromosome was used to measure reciprocal crossover (RCO) rates. Features of individual RCO events were then molecularly characterized using chromosome-specific microarrays. In the second assay, cells were sub-cultured for 250 generations and LOH was examined genome-wide using microarrays. Though loss of Top1 did not destabilize single-copy genomic regions, RCO events were more complex than in a wild-type strain. In contrast to the stability of single-copy regions, sub-culturing experiments revealed that top1 mutants had greatly elevated levels of instability within the tandemly-repeated ribosomal RNA genes (in agreement with previous results). An intermediate in the enzymatic reaction catalyzed by Top1 is the covalent attachment of Top1 to the cleaved DNA. The resulting Top1 cleavage complex (Top1cc) is usually transient but can be stabilized by the drug camptothecin (CPT) or by the top1-T722A allele. We found that increased levels of the Top1cc resulted in a five- to ten-fold increase in RCOs and greatly increased instability within the rDNA and CUP1 tandem arrays. A detailed analysis of the events in strains with elevated levels of Top1cc suggests that recombinogenic DNA lesions are introduced during or after DNA synthesis. These results have important implications for understanding the effects of CPT as a chemotherapeutic agent. Topoisomerase I (Top1) nicks one strand of DNA to relieve torsional stress associated with replication, transcription and chromatin remodeling. The enzyme forms a transient, covalent intermediate with the nicked DNA and stabilization of the cleavage complex (Top1cc) leads to genetic instability. We examined the effect of Top1 loss or Top1cc stabilization on genome-wide mitotic stability and on mitotic crossovers that lead to loss of heterozygosity (LOH) in budding yeast. The level of Top1cc was elevated using the chemotherapeutic drug camptothecin or a mutant form of the enzyme. Whereas loss of Top1 only destabilized ribosomal DNA repeats, Top1cc accumulation was additionally associated with elevated LOH and genome-wide instability. In particular, the Top1cc greatly elevated copy number variation at the CUP1 tandem-repeat locus, consistent with elevated sister chromatid recombination. Molecular examination of LOH events associated with the Top1cc was also consistent with generation of recombination-initiating lesions during or after DNA synthesis. These results demonstrate that the use of topoisomerase inhibitors results in widespread genome instability that may contribute to secondary neoplasms.
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Yin Y, Petes TD. Recombination between homologous chromosomes induced by unrepaired UV-generated DNA damage requires Mus81p and is suppressed by Mms2p. PLoS Genet 2015; 11:e1005026. [PMID: 25738287 PMCID: PMC4349867 DOI: 10.1371/journal.pgen.1005026] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 01/25/2015] [Indexed: 11/18/2022] Open
Abstract
DNA lesions caused by UV radiation are highly recombinogenic. In wild-type cells, the recombinogenic effect of UV partially reflects the processing of UV-induced pyrimidine dimers into DNA gaps or breaks by the enzymes of the nucleotide excision repair (NER) pathway. In this study, we show that unprocessed pyrimidine dimers also potently induce recombination between homologs. In NER-deficient rad14 diploid strains, we demonstrate that unexcised pyrimidine dimers stimulate crossovers, noncrossovers, and break-induced replication events. The same dose of UV is about six-fold more recombinogenic in a repair-deficient strain than in a repair-proficient strain. We also examined the roles of several genes involved in the processing of UV-induced damage in NER-deficient cells. We found that the resolvase Mus81p is required for most of the UV-induced inter-homolog recombination events. This requirement likely reflects the Mus81p-associated cleavage of dimer-blocked replication forks. The error-free post-replication repair pathway mediated by Mms2p suppresses dimer-induced recombination between homologs, possibly by channeling replication-blocking lesions into recombination between sister chromatids. Ultraviolet (UV) light is a ubiquitous agent of exogenous DNA damage. In normal cells, the nucleotide excision repair (NER) pathway is the primary mechanism for repair of UV-induced DNA lesions. Defects in the NER pathway are associated with the human disease xeroderma pigmentosum (XP), and XP patients are prone to skin cancer. Mitotic recombination is strongly stimulated by UV treatment. In this study, we examined whether such stimulation requires the NER pathway. We show that, in the absence of NER, UV is still able to greatly induce recombination. We then characterized a nuclease that is required to generate recombinogenic breaks. Finally, we examined a previously known recombinogenic pathway called the “post-replication repair (PRR) pathway.” Our results suggest that the PRR pathway mainly promotes recombination between sister chromatids, and suppresses recombination between chromosome homologs.
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Affiliation(s)
- Yi Yin
- Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Thomas D. Petes
- Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
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