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Ausiannikava D, Mitchell L, Marriott H, Smith V, Hawkins M, Makarova KS, Koonin EV, Nieduszynski CA, Allers T. Evolution of Genome Architecture in Archaea: Spontaneous Generation of a New Chromosome in Haloferax volcanii. Mol Biol Evol 2018; 35:1855-1868. [PMID: 29668953 PMCID: PMC6063281 DOI: 10.1093/molbev/msy075] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The common ancestry of archaea and eukaryotes is evident in their genome architecture. All eukaryotic and several archaeal genomes consist of multiple chromosomes, each replicated from multiple origins. Three scenarios have been proposed for the evolution of this genome architecture: 1) mutational diversification of a multi-copy chromosome; 2) capture of a new chromosome by horizontal transfer; 3) acquisition of new origins and splitting into two replication-competent chromosomes. We report an example of the third scenario: the multi-origin chromosome of the archaeon Haloferax volcanii has split into two elements via homologous recombination. The newly generated elements are bona fide chromosomes, because each bears "chromosomal" replication origins, rRNA loci, and essential genes. The new chromosomes were stable during routine growth but additional genetic manipulation, which involves selective bottlenecks, provoked further rearrangements. To the best of our knowledge, rearrangement of a naturally evolved prokaryotic genome to generate two new chromosomes has not been described previously.
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Affiliation(s)
- Darya Ausiannikava
- School of Life Sciences, University of Nottingham, Queen’s Medical Centre, Nottingham, United Kingdom
| | - Laura Mitchell
- School of Life Sciences, University of Nottingham, Queen’s Medical Centre, Nottingham, United Kingdom
| | - Hannah Marriott
- School of Life Sciences, University of Nottingham, Queen’s Medical Centre, Nottingham, United Kingdom
| | - Victoria Smith
- School of Life Sciences, University of Nottingham, Queen’s Medical Centre, Nottingham, United Kingdom
| | - Michelle Hawkins
- School of Life Sciences, University of Nottingham, Queen’s Medical Centre, Nottingham, United Kingdom
| | - Kira S Makarova
- National Center for Biotechnology Information, National Library of Medicine, NIH, Bethesda, MD
| | - Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, NIH, Bethesda, MD
| | | | - Thorsten Allers
- School of Life Sciences, University of Nottingham, Queen’s Medical Centre, Nottingham, United Kingdom
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52
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The evolution of the temporal program of genome replication. Nat Commun 2018; 9:2199. [PMID: 29875360 PMCID: PMC5989221 DOI: 10.1038/s41467-018-04628-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 05/08/2018] [Indexed: 01/19/2023] Open
Abstract
Genome replication is highly regulated in time and space, but the rules governing the remodeling of these programs during evolution remain largely unknown. We generated genome-wide replication timing profiles for ten Lachancea yeasts, covering a continuous evolutionary range from closely related to more divergent species. We show that replication programs primarily evolve through a highly dynamic evolutionary renewal of the cohort of active replication origins. We found that gained origins appear with low activity yet become more efficient and fire earlier as they evolutionarily age. By contrast, origins that are lost comprise the complete range of firing strength. Additionally, they preferentially occur in close vicinity to strong origins. Interestingly, despite high evolutionary turnover, active replication origins remain regularly spaced along chromosomes in all species, suggesting that origin distribution is optimized to limit large inter-origin intervals. We propose a model on the evolutionary birth, death, and conservation of active replication origins. Temporal programs of genome replication show different levels of conservation between closely or distantly related species. Here, the authors generate genome-wide replication timing profiles for ten yeast species, and analyze their evolutionary dynamics.
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53
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Sharp NP, Sandell L, James CG, Otto SP. The genome-wide rate and spectrum of spontaneous mutations differ between haploid and diploid yeast. Proc Natl Acad Sci U S A 2018; 115:E5046-E5055. [PMID: 29760081 PMCID: PMC5984525 DOI: 10.1073/pnas.1801040115] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
By altering the dynamics of DNA replication and repair, alternative ploidy states may experience different rates and types of new mutations, leading to divergent evolutionary outcomes. We report a direct comparison of the genome-wide spectrum of spontaneous mutations arising in haploids and diploids following a mutation-accumulation experiment in the budding yeast Saccharomyces cerevisiae Characterizing the number, types, locations, and effects of thousands of mutations revealed that haploids were more prone to single-nucleotide mutations (SNMs) and mitochondrial mutations, while larger structural changes were more common in diploids. Mutations were more likely to be detrimental in diploids, even after accounting for the large impact of structural changes, contrary to the prediction that mutations would have weaker effects, due to masking, in diploids. Haploidy is expected to reduce the opportunity for conservative DNA repair involving homologous chromosomes, increasing the insertion-deletion rate, but we found little support for this idea. Instead, haploids were more susceptible to SNMs in late-replicating genomic regions, resulting in a ploidy difference in the spectrum of substitutions. In diploids, we detect mutation rate variation among chromosomes in association with centromere location, a finding that is supported by published polymorphism data. Diploids are not simply doubled haploids; instead, our results predict that the spectrum of spontaneous mutations will substantially shape the dynamics of genome evolution in haploid and diploid populations.
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Affiliation(s)
- Nathaniel P Sharp
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Linnea Sandell
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Christopher G James
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Sarah P Otto
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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54
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Kedziora S, Gali VK, Wilson RHC, Clark KRM, Nieduszynski CA, Hiraga SI, Donaldson AD. Rif1 acts through Protein Phosphatase 1 but independent of replication timing to suppress telomere extension in budding yeast. Nucleic Acids Res 2018; 46:3993-4003. [PMID: 29529242 PMCID: PMC5934629 DOI: 10.1093/nar/gky132] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 02/09/2018] [Accepted: 02/23/2018] [Indexed: 12/24/2022] Open
Abstract
The Rif1 protein negatively regulates telomeric TG repeat length in the budding yeast Saccharomyces cerevisiae, but how it prevents telomere over-extension is unknown. Rif1 was recently shown to control DNA replication by acting as a Protein Phosphatase 1 (PP1)-targeting subunit. Therefore, we investigated whether Rif1 controls telomere length by targeting PP1 activity. We find that a Rif1 mutant defective for PP1 interaction causes a long-telomere phenotype, similar to that of rif1Δ cells. Tethering PP1 at a specific telomere partially substitutes for Rif1 in limiting TG repeat length, confirming the importance of PP1 in telomere length control. Ablating Rif1-PP1 interaction is known to cause precocious activation of telomere-proximal replication origins and aberrantly early telomere replication. However, we find that Rif1 still limits telomere length even if late replication is forced through deletion of nearby replication origins, indicating that Rif1 can control telomere length independent of replication timing. Moreover we find that, even at a de novo telomere created after DNA synthesis during a mitotic block, Rif1-PP1 interaction is required to suppress telomere lengthening and prevent inappropriate recruitment of Tel1 kinase. Overall, our results show that Rif1 controls telomere length by recruiting PP1 to directly suppress telomerase-mediated TG repeat lengthening.
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Affiliation(s)
- Sylwia Kedziora
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
| | - Vamsi K Gali
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
| | - Rosemary HC Wilson
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Kate RM Clark
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
| | - Conrad A Nieduszynski
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Shin-ichiro Hiraga
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
| | - Anne D Donaldson
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
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55
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Fang D, Lengronne A, Shi D, Forey R, Skrzypczak M, Ginalski K, Yan C, Wang X, Cao Q, Pasero P, Lou H. Dbf4 recruitment by forkhead transcription factors defines an upstream rate-limiting step in determining origin firing timing. Genes Dev 2018; 31:2405-2415. [PMID: 29330352 PMCID: PMC5795786 DOI: 10.1101/gad.306571.117] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 11/30/2017] [Indexed: 12/26/2022]
Abstract
Fang et al. show that Dbf4 is enriched at early origins through its interaction with forkhead transcription factors Fkh1 and Fkh2. Dbf4 interacts directly with Sld3 and promotes the recruitment of downstream limiting factors. Initiation of eukaryotic chromosome replication follows a spatiotemporal program. The current model suggests that replication origins compete for a limited pool of initiation factors. However, it remains to be answered how these limiting factors are preferentially recruited to early origins. Here, we report that Dbf4 is enriched at early origins through its interaction with forkhead transcription factors Fkh1 and Fkh2. This interaction is mediated by the Dbf4 C terminus and was successfully reconstituted in vitro. An interaction-defective mutant, dbf4ΔC, phenocopies fkh alleles in terms of origin firing. Remarkably, genome-wide replication profiles reveal that the direct fusion of the DNA-binding domain (DBD) of Fkh1 to Dbf4 restores the Fkh-dependent origin firing but interferes specifically with the pericentromeric origin activation. Furthermore, Dbf4 interacts directly with Sld3 and promotes the recruitment of downstream limiting factors. These data suggest that Fkh1 targets Dbf4 to a subset of noncentromeric origins to promote early replication in a manner that is reminiscent of the recruitment of Dbf4 to pericentromeric origins by Ctf19.
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Affiliation(s)
- Dingqiang Fang
- State Key Laboratory of Agro-Biotechnology, Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Armelle Lengronne
- Institute of Human Genetics, Centre National de la Recherche Scientifique, University of Montpellier, Equipe Labellisée Ligue Contre le Cancer, F-34396 Montpellier Cedex 5, France
| | - Di Shi
- State Key Laboratory of Agro-Biotechnology, Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Romain Forey
- Institute of Human Genetics, Centre National de la Recherche Scientifique, University of Montpellier, Equipe Labellisée Ligue Contre le Cancer, F-34396 Montpellier Cedex 5, France
| | - Magdalena Skrzypczak
- Laboratory of Bioinformatics and Systems Biology, Centre of New Technologies, University of Warsaw, 02-089 Warsaw, Poland
| | - Krzysztof Ginalski
- Laboratory of Bioinformatics and Systems Biology, Centre of New Technologies, University of Warsaw, 02-089 Warsaw, Poland
| | - Changhui Yan
- Department of Computer Science, North Dakota State University, Fargo, North Dakota 58108, USA
| | - Xiaoke Wang
- State Key Laboratory of Agro-Biotechnology, Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Qinhong Cao
- State Key Laboratory of Agro-Biotechnology, Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Philippe Pasero
- Institute of Human Genetics, Centre National de la Recherche Scientifique, University of Montpellier, Equipe Labellisée Ligue Contre le Cancer, F-34396 Montpellier Cedex 5, France
| | - Huiqiang Lou
- State Key Laboratory of Agro-Biotechnology, Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Biological Sciences, China Agricultural University, Beijing 100193, China
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56
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Marques CA, McCulloch R. Conservation and Variation in Strategies for DNA Replication of Kinetoplastid Nuclear Genomes. Curr Genomics 2018; 19:98-109. [PMID: 29491738 PMCID: PMC5814967 DOI: 10.2174/1389202918666170815144627] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Revised: 03/19/2017] [Accepted: 04/11/2017] [Indexed: 12/21/2022] Open
Abstract
Introduction: Understanding how the nuclear genome of kinetoplastid parasites is replicated received experimental stimulus from sequencing of the Leishmania major, Trypanosoma brucei and Trypanosoma cruzi genomes around 10 years ago. Gene annotations suggested key players in DNA replication initiation could not be found in these organisms, despite considerable conservation amongst characterised eukaryotes. Initial studies that indicated trypanosomatids might possess an archaeal-like Origin Recognition Complex (ORC), composed of only a single factor termed ORC1/CDC6, have been supplanted by the more recent identification of an ORC in T. brucei. However, the constituent subunits of T. brucei ORC are highly diverged relative to other eukaryotic ORCs and the activity of the complex appears subject to novel, positive regulation. The availability of whole genome sequences has also allowed the deployment of genome-wide strategies to map DNA replication dynamics, to date in T. brucei and Leishmania. ORC1/CDC6 binding and function in T. brucei displays pronounced overlap with the unconventional organisation of gene expression in the genome. Moreover, mapping of sites of replication initiation suggests pronounced differences in replication dynamics in Leishmania relative to T. brucei. Conclusion: Here we discuss what implications these emerging data may have for parasite and eukaryotic biology of DNA replication.
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Affiliation(s)
- Catarina A Marques
- Division of Biological Chemistry and Drug Discovery, School of Life Sciences, Dow Street, University of Dundee, Dundee, DD1 5EH, UK
| | - Richard McCulloch
- The Wellcome Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, Sir Graeme Davis Building, 120 University Place, University of Glasgow, Glasgow, G12 8TA, UK
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57
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Abstract
Profiling of DNA replication during progression through S phase allows a quantitative snap-shot of replication origin usage and DNA replication fork progression. We present a method for using deep sequencing data to profile DNA replication in S. cerevisiae.
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Affiliation(s)
- Xanita Saayman
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON, Canada, M5S 3E1
| | - Cristina Ramos-Pérez
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON, Canada, M5S 3E1
| | - Grant W Brown
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON, Canada, M5S 3E1.
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58
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Abstract
Site-specific arrest of DNA replication is a useful tool for analyzing cellular responses to DNA replication perturbation. The E. coli Tus-Ter replication barrier can be reconstituted in eukaryotic cells as a system to engineer an unscheduled collision between a replication fork and an "alien" impediment to DNA replication. To further develop this system as a versatile tool, we describe a set of reagents and a detailed protocol that can be used to engineer Tus-Ter barriers into any locus in the budding yeast genome. Because the Tus-Ter complex is a bipartite system with intrinsic DNA replication-blocking activity, the reagents and protocols developed and validated in yeast could also be optimized to engineer site-specific replication fork barriers into other eukaryotic cell types.
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59
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Nakato R, Shirahige K. Recent advances in ChIP-seq analysis: from quality management to whole-genome annotation. Brief Bioinform 2017; 18:279-290. [PMID: 26979602 PMCID: PMC5444249 DOI: 10.1093/bib/bbw023] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Indexed: 02/06/2023] Open
Abstract
Chromatin immunoprecipitation followed by sequencing (ChIP-seq) analysis can detect protein/DNA-binding and histone-modification sites across an entire genome. Recent advances in sequencing technologies and analyses enable us to compare hundreds of samples simultaneously; such large-scale analysis has potential to reveal the high-dimensional interrelationship level for regulatory elements and annotate novel functional genomic regions de novo. Because many experimental considerations are relevant to the choice of a method in a ChIP-seq analysis, the overall design and quality management of the experiment are of critical importance. This review offers guiding principles of computation and sample preparation for ChIP-seq analyses, highlighting the validity and limitations of the state-of-the-art procedures at each step. We also discuss the latest challenges of single-cell analysis that will encourage a new era in this field.
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Affiliation(s)
- Ryuichiro Nakato
- Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo, Japan
| | - Katsuhiko Shirahige
- Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo, Japan.,Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency, Kawaguchi, Japan
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60
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Localization of Cdc7 Protein Kinase During DNA Replication in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2017; 7:3757-3774. [PMID: 28924058 PMCID: PMC5677158 DOI: 10.1534/g3.117.300223] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
DDK, a conserved serine-threonine protein kinase composed of a regulatory subunit, Dbf4, and a catalytic subunit, Cdc7, is essential for DNA replication initiation during S phase of the cell cycle through MCM2-7 helicase phosphorylation. The biological significance of DDK is well characterized, but the full mechanism of how DDK associates with substrates remains unclear. Cdc7 is bound to chromatin in the Saccharomyces cerevisiae genome throughout the cell cycle, but there is little empirical evidence as to specific Cdc7 binding locations. Using biochemical and genetic techniques, this study investigated the specific localization of Cdc7 on chromatin. The Calling Cards method, using Ty5 retrotransposons as a marker for DNA–protein binding, suggests Cdc7 kinase is preferentially bound to genomic DNA known to replicate early in S phase, including centromeres and origins of replication. We also discovered Cdc7 binding throughout the genome, which may be necessary to initiate other cellular processes, including meiotic recombination and translesion synthesis. A kinase dead Cdc7 point mutation increases the Ty5 retrotransposon integration efficiency and a 55-amino acid C-terminal truncation of Cdc7, unable to bind Dbf4, reduces Cdc7 binding suggesting a requirement for Dbf4 to stabilize Cdc7 on chromatin during S phase. Chromatin immunoprecipitation demonstrates that Cdc7 binding near specific origins changes during S phase. Our results suggest a model where Cdc7 is loosely bound to chromatin during G1. At the G1/S transition, Cdc7 binding to chromatin is increased and stabilized, preferentially at sites that may become origins, in order to carry out a variety of cellular processes.
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61
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Li R, Xiong G, Yuan S, Wu Z, Miao Y, Weng P. Investigating the underlying mechanism of Saccharomyces cerevisiae in response to ethanol stress employing RNA-seq analysis. World J Microbiol Biotechnol 2017; 33:206. [PMID: 29101531 DOI: 10.1007/s11274-017-2376-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Accepted: 10/29/2017] [Indexed: 11/26/2022]
Abstract
Saccharomyces cerevisiae has been widely used for wine fermentation and bio-fuels production. A S. cerevisiae strain Sc131 isolated from tropical fruit shows good fermentation properties and ethanol tolerance, exhibiting significant potential in Chinese bayberry wine fermentation. In this study, RNA-sequence and RT-qPCR was used to investigate the transcriptome profile of Sc131 in response to ethanol stress. Scanning Electron Microscopy were carried out to observe surface morphology of yeast cells. Totally, 937 genes were identified differential expressed, including 587 up-regulated and 350 down-regulated genes, after 4-h ethanol stress (10% v/v). Transcriptomic analysis revealed that, most genes involved in regulating filamentous growth or pseudohyphal growth were significantly up-regulated in response to ethanol stress. The complex protein quality control machineries, Hsp90/Hsp70 and Hsp104/Hsp70/Hsp40 based chaperone system combining with ubiquitin-proteasome proteolytic pathway were both activated to recognize and degrade misfolding proteins. Genes related to biosynthesis and metabolism of two well-known stress-responsive substances trehalose and ergosterol were generally up-regulated, while genes associated with amino acids biosynthesis and metabolism processes were differentially expressed. Moreover, thiamine was also important in response to ethanol stress. This research may promote the potential applications of Sc131 in the fermentation of Chinese bayberry wine.
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Affiliation(s)
- Ruoyun Li
- Department of Food Science and Engineering, School of Marine Sciences, Ningbo University, Ningbo, 315211, People's Republic of China
| | - Guotong Xiong
- Department of Food Science and Engineering, School of Marine Sciences, Ningbo University, Ningbo, 315211, People's Republic of China
| | - Shukun Yuan
- Department of Food Science and Engineering, School of Marine Sciences, Ningbo University, Ningbo, 315211, People's Republic of China
| | - Zufang Wu
- Department of Food Science and Engineering, School of Marine Sciences, Ningbo University, Ningbo, 315211, People's Republic of China.
- Key Laboratory of Applied Marine Biotechnology of Ministry of Education, Ningbo University, Ningbo, 315211, People's Republic of China.
| | - Yingjie Miao
- Department of Food Science and Engineering, School of Marine Sciences, Ningbo University, Ningbo, 315211, People's Republic of China
| | - Peifang Weng
- Department of Food Science and Engineering, School of Marine Sciences, Ningbo University, Ningbo, 315211, People's Republic of China
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62
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Ruiz L, Bottacini F, Boinett CJ, Cain AK, O'Connell-Motherway M, Lawley TD, van Sinderen D. The essential genomic landscape of the commensal Bifidobacterium breve UCC2003. Sci Rep 2017; 7:5648. [PMID: 28717159 PMCID: PMC5514069 DOI: 10.1038/s41598-017-05795-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 06/02/2017] [Indexed: 01/15/2023] Open
Abstract
Bifidobacteria are common gut commensals with purported health-promoting effects. This has encouraged scientific research into bifidobacteria, though recalcitrance to genetic manipulation and scarcity of molecular tools has hampered our knowledge on the precise molecular determinants of their health-promoting attributes and gut adaptation. To overcome this problem and facilitate functional genomic analyses in bifidobacteria, we created a large Tn5 transposon mutant library of the commensal Bifidobacterium breve UCC2003 that was further characterized by means of a Transposon Directed Insertion Sequencing (TraDIS) approach. Statistical analysis of transposon insertion distribution revealed a set of 453 genes that are essential for or markedly contribute to growth of this strain under laboratory conditions. These essential genes encode functions involved in the so-called bifid-shunt, most enzymes related to nucleotide biosynthesis and a range of housekeeping functions. Comparison to the Bifidobacterium and B. breve core genomes highlights a high degree of conservation of essential genes at the species and genus level, while comparison to essential gene datasets from other gut bacteria identified essential genes that appear specific to bifidobacteria. This work establishes a useful molecular tool for scientific discovery of bifidobacteria and identifies targets for further studies aimed at characterizing essential functions not previously examined in bifidobacteria.
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Affiliation(s)
- Lorena Ruiz
- School of Microbiology and APC Microbiome Institute, National University of Ireland, Cork, Western Road, Ireland.,Department of Nutrition, Bromatology and Food Technology, Complutense University, Avda Puerta de Hierro s/n, 28040, Madrid, Spain
| | - Francesca Bottacini
- School of Microbiology and APC Microbiome Institute, National University of Ireland, Cork, Western Road, Ireland
| | | | - Amy K Cain
- Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK
| | - Mary O'Connell-Motherway
- School of Microbiology and APC Microbiome Institute, National University of Ireland, Cork, Western Road, Ireland
| | | | - Douwe van Sinderen
- School of Microbiology and APC Microbiome Institute, National University of Ireland, Cork, Western Road, Ireland.
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63
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Devlin R, Marques CA, McCulloch R. Does DNA replication direct locus-specific recombination during host immune evasion by antigenic variation in the African trypanosome? Curr Genet 2017; 63:441-449. [PMID: 27822899 PMCID: PMC5422504 DOI: 10.1007/s00294-016-0662-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 10/26/2016] [Accepted: 10/27/2016] [Indexed: 12/14/2022]
Abstract
All pathogens must survive host immune attack and, amongst the survival strategies that have evolved, antigenic variation is a particularly widespread reaction to thwart adaptive immunity. Though the reactions that underlie antigenic variation are highly varied, recombination by gene conversion is a widespread approach to immune survival in bacterial and eukaryotic pathogens. In the African trypanosome, antigenic variation involves gene conversion-catalysed movement of a huge number of variant surface glycoprotein (VSG) genes into a few telomeric sites for VSG expression, amongst which only a single site is actively transcribed at one time. Genetic evidence indicates VSG gene conversion has co-opted the general genome maintenance reaction of homologous recombination, aligning the reaction strategy with targeted rearrangements found in many organisms. What is less clear is how gene conversion might be initiated within the locality of the VSG expression sites. Here, we discuss three emerging models for VSG switching initiation and ask how these compare with processes for adaptive genome change found in other organisms.
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Affiliation(s)
- Rebecca Devlin
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Catarina A Marques
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, UK
| | - Richard McCulloch
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
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64
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Müller CA, Nieduszynski CA. DNA replication timing influences gene expression level. J Cell Biol 2017; 216:1907-1914. [PMID: 28539386 PMCID: PMC5496624 DOI: 10.1083/jcb.201701061] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 04/06/2017] [Accepted: 04/19/2017] [Indexed: 12/31/2022] Open
Abstract
Eukaryotic genomes are replicated in a reproducible temporal order whose physiological significance is poorly understood. Müller and Nieduszynski compare the temporal order of genome replication in phylogenetically diverse yeast species and identify genes for which conserved replication timing contributes to maximal expression. Eukaryotic genomes are replicated in a reproducible temporal order; however, the physiological significance is poorly understood. We compared replication timing in divergent yeast species and identified genomic features with conserved replication times. Histone genes were among the earliest replicating loci in all species. We specifically delayed the replication of HTA1-HTB1 and discovered that this halved the expression of these histone genes. Finally, we showed that histone and cell cycle genes in general are exempt from Rtt109-dependent dosage compensation, suggesting the existence of pathways excluding specific loci from dosage compensation mechanisms. Thus, we have uncovered one of the first physiological requirements for regulated replication time and demonstrated a direct link between replication timing and gene expression.
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Affiliation(s)
- Carolin A Müller
- Sir William Dunn School of Pathology, University of Oxford, Oxford, England, UK
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65
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Shen Y, Wang Y, Chen T, Gao F, Gong J, Abramczyk D, Walker R, Zhao H, Chen S, Liu W, Luo Y, Müller CA, Paul-Dubois-Taine A, Alver B, Stracquadanio G, Mitchell LA, Luo Z, Fan Y, Zhou B, Wen B, Tan F, Wang Y, Zi J, Xie Z, Li B, Yang K, Richardson SM, Jiang H, French CE, Nieduszynski CA, Koszul R, Marston AL, Yuan Y, Wang J, Bader JS, Dai J, Boeke JD, Xu X, Cai Y, Yang H. Deep functional analysis of synII, a 770-kilobase synthetic yeast chromosome. Science 2017; 355:eaaf4791. [PMID: 28280153 PMCID: PMC5390853 DOI: 10.1126/science.aaf4791] [Citation(s) in RCA: 135] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 02/01/2017] [Indexed: 12/15/2022]
Abstract
Here, we report the successful design, construction, and characterization of a 770-kilobase synthetic yeast chromosome II (synII). Our study incorporates characterization at multiple levels-including phenomics, transcriptomics, proteomics, chromosome segregation, and replication analysis-to provide a thorough and comprehensive analysis of a synthetic chromosome. Our Trans-Omics analyses reveal a modest but potentially relevant pervasive up-regulation of translational machinery observed in synII, mainly caused by the deletion of 13 transfer RNAs. By both complementation assays and SCRaMbLE (synthetic chromosome rearrangement and modification by loxP-mediated evolution), we targeted and debugged the origin of a growth defect at 37°C in glycerol medium, which is related to misregulation of the high-osmolarity glycerol response. Despite the subtle differences, the synII strain shows highly consistent biological processes comparable to the native strain.
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Affiliation(s)
- Yue Shen
- BGI-Shenzhen, Shenzhen 518083, China
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
- James D. Watson Institute of Genome Sciences, Hangzhou 310058, China
- BGI-Qingdao, Qingdao 266555, China
| | - Yun Wang
- BGI-Shenzhen, Shenzhen 518083, China
- BGI-Qingdao, Qingdao 266555, China
| | - Tai Chen
- BGI-Shenzhen, Shenzhen 518083, China
- BGI-Qingdao, Qingdao 266555, China
| | - Feng Gao
- BGI-Shenzhen, Shenzhen 518083, China
| | | | - Dariusz Abramczyk
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Roy Walker
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | | | | | - Wei Liu
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Yisha Luo
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Carolin A. Müller
- Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK
| | | | - Bonnie Alver
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Giovanni Stracquadanio
- High-Throughput Biology Center, School of Medicine, Johns Hopkins University, Baltimore, Maryland, 21205 USA
- Department of Biomedical Engineering, School of Engineering, Johns Hopkins University, Baltimore, Maryland 21218 USA
| | - Leslie A. Mitchell
- Institute for Systems Genetics, NYU Langone Medical Center, ACLSW Room 503, 430 East 29th Street, New York, NY 10016
| | - Zhouqing Luo
- Key Laboratory of Industrial Biocatalysis (Ministry of Education), Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | | | | | - Bo Wen
- BGI-Shenzhen, Shenzhen 518083, China
| | | | | | - Jin Zi
- BGI-Shenzhen, Shenzhen 518083, China
| | - Zexiong Xie
- Key Laboratory of Systems Bioengineering (Ministry of Education), SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
| | - Bingzhi Li
- Key Laboratory of Systems Bioengineering (Ministry of Education), SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
| | - Kun Yang
- High-Throughput Biology Center, School of Medicine, Johns Hopkins University, Baltimore, Maryland, 21205 USA
| | - Sarah M. Richardson
- High-Throughput Biology Center, School of Medicine, Johns Hopkins University, Baltimore, Maryland, 21205 USA
- Department of Biomedical Engineering, School of Engineering, Johns Hopkins University, Baltimore, Maryland 21218 USA
| | - Hui Jiang
- BGI-Shenzhen, Shenzhen 518083, China
| | | | | | - Romain Koszul
- Department of Genomes and Genetics, Institut Pasteur / CNRS UMR3525, 25-28, rue du Docteur Roux, 75724 Paris Cedex 15, France
| | - Adele L. Marston
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Yingjin Yuan
- Key Laboratory of Systems Bioengineering (Ministry of Education), SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
| | - Jian Wang
- BGI-Shenzhen, Shenzhen 518083, China
| | - Joel S. Bader
- Department of Biomedical Engineering, School of Engineering, Johns Hopkins University, Baltimore, Maryland 21218 USA
- Institute for Systems Genetics, NYU Langone Medical Center, ACLSW Room 503, 430 East 29th Street, New York, NY 10016
| | - Junbiao Dai
- Key Laboratory of Industrial Biocatalysis (Ministry of Education), Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jef D. Boeke
- Institute for Systems Genetics, NYU Langone Medical Center, ACLSW Room 503, 430 East 29th Street, New York, NY 10016
| | - Xun Xu
- BGI-Shenzhen, Shenzhen 518083, China
- BGI-Qingdao, Qingdao 266555, China
| | - Yizhi Cai
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Huanming Yang
- BGI-Shenzhen, Shenzhen 518083, China
- James D. Watson Institute of Genome Sciences, Hangzhou 310058, China
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66
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Gispan A, Carmi M, Barkai N. Model-based analysis of DNA replication profiles: predicting replication fork velocity and initiation rate by profiling free-cycling cells. Genome Res 2016; 27:310-319. [PMID: 28028072 PMCID: PMC5287236 DOI: 10.1101/gr.205849.116] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 12/12/2016] [Indexed: 12/24/2022]
Abstract
Eukaryotic cells initiate DNA synthesis by sequential firing of hundreds of origins. This ordered replication is described by replication profiles, which measure the DNA content within a cell population. Here, we show that replication dynamics can be deduced from replication profiles of free-cycling cells. While such profiles lack explicit temporal information, they are sensitive to fork velocity and initiation capacity through the passive replication pattern, namely the replication of origins by forks emanating elsewhere. We apply our model-based approach to a compendium of profiles that include most viable budding yeast mutants implicated in replication. Predicted changes in fork velocity or initiation capacity are verified by profiling synchronously replicating cells. Notably, most mutants implicated in late (or early) origin effects are explained by global modulation of fork velocity or initiation capacity. Our approach provides a rigorous framework for analyzing DNA replication profiles of free-cycling cells.
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Affiliation(s)
- Ariel Gispan
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Miri Carmi
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Naama Barkai
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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67
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Rodriguez J, Lee L, Lynch B, Tsukiyama T. Nucleosome occupancy as a novel chromatin parameter for replication origin functions. Genome Res 2016; 27:269-277. [PMID: 27895110 PMCID: PMC5287232 DOI: 10.1101/gr.209940.116] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 11/17/2016] [Indexed: 11/01/2022]
Abstract
Eukaryotic DNA replication initiates from multiple discrete sites in the genome, termed origins of replication (origins). Prior to S phase, multiple origins are poised to initiate replication by recruitment of the pre-replicative complex (pre-RC). For proper replication to occur, origin activation must be tightly regulated. At the population level, each origin has a distinct firing time and frequency of activation within S phase. Many studies have shown that chromatin can strongly influence initiation of DNA replication. However, the chromatin parameters that affect properties of origins have not been thoroughly established. We found that nucleosome occupancy in G1 varies greatly around origins across the S. cerevisiae genome, and nucleosome occupancy around origins significantly correlates with the activation time and efficiency of origins, as well as pre-RC formation. We further demonstrate that nucleosome occupancy around origins in G1 is established during transition from G2/M to G1 in a pre-RC-dependent manner. Importantly, the diminished cell-cycle changes in nucleosome occupancy around origins in the orc1-161 mutant are associated with an abnormal global origin usage profile, suggesting that proper establishment of nucleosome occupancy around origins is a critical step for regulation of global origin activities. Our work thus establishes nucleosome occupancy as a novel and key chromatin parameter for proper origin regulation.
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Affiliation(s)
- Jairo Rodriguez
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Laura Lee
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.,Molecular and Cellular Biology Program, University of Washington, Seattle, Washington 98195, USA
| | - Bryony Lynch
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Toshio Tsukiyama
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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68
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Abstract
DNA replication origins strikingly differ between eukaryotic species and cell types. Origins are localized and can be highly efficient in budding yeast, are randomly located in early fly and frog embryos, which do not transcribe their genomes, and are clustered in broad (10-100 kb) non-transcribed zones, frequently abutting transcribed genes, in mammalian cells. Nonetheless, in all cases, origins are established during the G1-phase of the cell cycle by the loading of double hexamers of the Mcm 2-7 proteins (MCM DHs), the core of the replicative helicase. MCM DH activation in S-phase leads to origin unwinding, polymerase recruitment, and initiation of bidirectional DNA synthesis. Although MCM DHs are initially loaded at sites defined by the binding of the origin recognition complex (ORC), they ultimately bind chromatin in much greater numbers than ORC and only a fraction are activated in any one S-phase. Data suggest that the multiplicity and functional redundancy of MCM DHs provide robustness to the replication process and affect replication time and that MCM DHs can slide along the DNA and spread over large distances around the ORC. Recent studies further show that MCM DHs are displaced along the DNA by collision with transcription complexes but remain functional for initiation after displacement. Therefore, eukaryotic DNA replication relies on intrinsically mobile and flexible origins, a strategy fundamentally different from bacteria but conserved from yeast to human. These properties of MCM DHs likely contribute to the establishment of broad, intergenic replication initiation zones in higher eukaryotes.
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Affiliation(s)
- Olivier Hyrien
- Institut de Biologie de l'Ecole Normale Superieure (IBENS), Ecole Normale Superieure, PSL Research University, Paris, France
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69
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Dimude JU, Midgley-Smith SL, Stein M, Rudolph CJ. Replication Termination: Containing Fork Fusion-Mediated Pathologies in Escherichia coli. Genes (Basel) 2016; 7:genes7080040. [PMID: 27463728 PMCID: PMC4999828 DOI: 10.3390/genes7080040] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 07/12/2016] [Accepted: 07/19/2016] [Indexed: 01/18/2023] Open
Abstract
Duplication of bacterial chromosomes is initiated via the assembly of two replication forks at a single defined origin. Forks proceed bi-directionally until they fuse in a specialised termination area opposite the origin. This area is flanked by polar replication fork pause sites that allow forks to enter but not to leave. The precise function of this replication fork trap has remained enigmatic, as no obvious phenotypes have been associated with its inactivation. However, the fork trap becomes a serious problem to cells if the second fork is stalled at an impediment, as replication cannot be completed, suggesting that a significant evolutionary advantage for maintaining this chromosomal arrangement must exist. Recently, we demonstrated that head-on fusion of replication forks can trigger over-replication of the chromosome. This over-replication is normally prevented by a number of proteins including RecG helicase and 3’ exonucleases. However, even in the absence of these proteins it can be safely contained within the replication fork trap, highlighting that multiple systems might be involved in coordinating replication fork fusions. Here, we discuss whether considering the problems associated with head-on replication fork fusion events helps us to better understand the important role of the replication fork trap in cellular metabolism.
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Affiliation(s)
- Juachi U Dimude
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK.
| | - Sarah L Midgley-Smith
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK.
| | - Monja Stein
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK.
| | - Christian J Rudolph
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK.
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70
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Akiyama MT, Oshima T, Chumsakul O, Ishikawa S, Maki H. Replication fork progression is paused in two large chromosomal zones flanking the DNA replication origin in Escherichia coli. Genes Cells 2016; 21:907-14. [PMID: 27353572 DOI: 10.1111/gtc.12388] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 05/16/2016] [Indexed: 11/27/2022]
Abstract
Although the speed of nascent DNA synthesis at individual replication forks is relatively uniform in bacterial cells, the dynamics of replication fork progression on the chromosome are hampered by a variety of natural impediments. Genome replication dynamics can be directly measured from an exponentially growing cell population by sequencing newly synthesized DNA strands that were specifically pulse-labeled with the thymidine analogue 5-bromo-2'-deoxyuridine (BrdU). However, a short pulse labeling with BrdU is impracticable for bacteria because of poor incorporation of BrdU into the cells, and thus, the genomewide dynamics of bacterial DNA replication remain undetermined. Using a new thymidine-requiring Escherichia coli strain, eCOMB, and high-throughput sequencing, we succeeded in determining the genomewide replication profile in bacterial cells. We also found that fork progression is paused in two ~200-kb chromosomal zones that flank the replication origin in the growing cells. This origin-proximal obstruction to fork progression was overcome by an increased thymidine concentration in the culture medium and enhanced by inhibition of transcription. These indicate that DNA replication near the origin is sensitive to the impediments to fork progression, namely a scarcity of the DNA precursor deoxythymidine triphosphate and probable conflicts between replication and transcription machineries.
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Affiliation(s)
- Masahiro Tatsumi Akiyama
- Division of Systems Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan
| | - Taku Oshima
- Division of Systems Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan
| | - Onuma Chumsakul
- Division of Systems Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan
| | - Shu Ishikawa
- Division of Systems Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan
| | - Hisaji Maki
- Division of Systems Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan
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71
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Stanojcic S, Sollelis L, Kuk N, Crobu L, Balard Y, Schwob E, Bastien P, Pagès M, Sterkers Y. Single-molecule analysis of DNA replication reveals novel features in the divergent eukaryotes Leishmania and Trypanosoma brucei versus mammalian cells. Sci Rep 2016; 6:23142. [PMID: 26976742 PMCID: PMC4791591 DOI: 10.1038/srep23142] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 02/17/2016] [Indexed: 01/29/2023] Open
Abstract
Leishmania and Trypanosoma are unicellular parasites that possess markedly original biological features as compared to other eukaryotes. The Leishmania genome displays a constitutive 'mosaic aneuploidy', whereas in Trypanosoma brucei, the megabase-sized chromosomes are diploid. We accurately analysed DNA replication parameters in three Leishmania species and Trypanosoma brucei as well as mouse embryonic fibroblasts (MEF). Active replication origins were visualized at the single molecule level using DNA molecular combing. More than one active origin was found on most DNA fibres, showing that the chromosomes are replicated from multiple origins. Inter-origin distances (IODs) were measured and found very large in trypanosomatids: the mean IOD was 160 kb in T. brucei and 226 kb in L. mexicana. Moreover, the progression of replication forks was faster than in any other eukaryote analyzed so far (mean velocity 1.9 kb/min in T. brucei and 2.4-2.6 kb/min in Leishmania). The estimated total number of active DNA replication origins in trypanosomatids is ~170. Finally, 14.4% of unidirectional replication forks were observed in T. brucei, in contrast to 1.5-1.7% in Leishmania and 4% in MEF cells. The biological significance of these original features is discussed.
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Affiliation(s)
- Slavica Stanojcic
- University of Montpellier, Faculty of Medicine, Laboratory of Parasitology-Mycology, Montpellier, F34090, France
| | - Lauriane Sollelis
- University of Montpellier, Faculty of Medicine, Laboratory of Parasitology-Mycology, Montpellier, F34090, France
| | - Nada Kuk
- University of Montpellier, Faculty of Medicine, Laboratory of Parasitology-Mycology, Montpellier, F34090, France
| | - Lucien Crobu
- CNRS 5290 - IRD 224 - University of Montpellier (UMR "MiVEGEC"), Montpellier, F34090, France
| | - Yves Balard
- University of Montpellier, Faculty of Medicine, Laboratory of Parasitology-Mycology, Montpellier, F34090, France
| | - Etienne Schwob
- Institute of Molecular Genetics, CNRS UMR5535 &University of Montpellier, Montpellier, F34293, France
| | - Patrick Bastien
- University of Montpellier, Faculty of Medicine, Laboratory of Parasitology-Mycology, Montpellier, F34090, France.,CNRS 5290 - IRD 224 - University of Montpellier (UMR "MiVEGEC"), Montpellier, F34090, France.,University Hospital Centre (CHU), Department of Parasitology-Mycology, Montpellier, F34090, France
| | - Michel Pagès
- CNRS 5290 - IRD 224 - University of Montpellier (UMR "MiVEGEC"), Montpellier, F34090, France
| | - Yvon Sterkers
- University of Montpellier, Faculty of Medicine, Laboratory of Parasitology-Mycology, Montpellier, F34090, France.,CNRS 5290 - IRD 224 - University of Montpellier (UMR "MiVEGEC"), Montpellier, F34090, France.,University Hospital Centre (CHU), Department of Parasitology-Mycology, Montpellier, F34090, France
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72
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The Consequences of Replicating in the Wrong Orientation: Bacterial Chromosome Duplication without an Active Replication Origin. mBio 2015; 6:e01294-15. [PMID: 26530381 PMCID: PMC4631800 DOI: 10.1128/mbio.01294-15] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Chromosome replication is regulated in all organisms at the assembly stage of the replication machinery at specific origins. In Escherichia coli, the DnaA initiator protein regulates the assembly of replication forks at oriC. This regulation can be undermined by defects in nucleic acid metabolism. In cells lacking RNase HI, replication initiates independently of DnaA and oriC, presumably at persisting R-loops. A similar mechanism was assumed for origin-independent synthesis in cells lacking RecG. However, recently we suggested that this synthesis initiates at intermediates resulting from replication fork fusions. Here we present data suggesting that in cells lacking RecG or RNase HI, origin-independent synthesis arises by different mechanisms, indicative of these two proteins having different roles in vivo. Our data support the idea that RNase HI processes R-loops, while RecG is required to process replication fork fusion intermediates. However, regardless of how origin-independent synthesis is initiated, a fraction of forks will proceed in an orientation opposite to normal. We show that the resulting head-on encounters with transcription threaten cell viability, especially if taking place in highly transcribed areas. Thus, despite their different functions, RecG and RNase HI are both important factors for maintaining replication control and orientation. Their absence causes severe replication problems, highlighting the advantages of the normal chromosome arrangement, which exploits a single origin to control the number of forks and their orientation relative to transcription, and a defined termination area to contain fork fusions. Any changes to this arrangement endanger cell cycle control, chromosome dynamics, and, ultimately, cell viability. IMPORTANCE Cell division requires unwinding of millions of DNA base pairs to generate the template for RNA transcripts as well as chromosome replication. As both processes use the same template, frequent clashes are unavoidable. To minimize the impact of these clashes, transcription and replication in bacteria follow the same directionality, thereby avoiding head-on collisions. This codirectionality is maintained by a strict regulation of where replication is started. We have used Escherichia coli as a model to investigate cells in which the defined location of replication initiation is compromised. In cells lacking either RNase HI or RecG, replication initiates away from the defined replication origin, and we discuss the different mechanisms by which this synthesis arises. In addition, the resulting forks proceed in a direction opposite to normal, thereby inducing head-on collisions between transcription and replication, and we show that the resulting consequences are severe enough to threaten the viability of cells.
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73
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Marques CA, Dickens NJ, Paape D, Campbell SJ, McCulloch R. Genome-wide mapping reveals single-origin chromosome replication in Leishmania, a eukaryotic microbe. Genome Biol 2015; 16:230. [PMID: 26481451 PMCID: PMC4612428 DOI: 10.1186/s13059-015-0788-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 09/21/2015] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND DNA replication initiates on defined genome sites, termed origins. Origin usage appears to follow common rules in the eukaryotic organisms examined to date: all chromosomes are replicated from multiple origins, which display variations in firing efficiency and are selected from a larger pool of potential origins. To ask if these features of DNA replication are true of all eukaryotes, we describe genome-wide origin mapping in the parasite Leishmania. RESULTS Origin mapping in Leishmania suggests a striking divergence in origin usage relative to characterized eukaryotes, since each chromosome appears to be replicated from a single origin. By comparing two species of Leishmania, we find evidence that such origin singularity is maintained in the face of chromosome fusion or fission events during evolution. Mapping Leishmania origins suggests that all origins fire with equal efficiency, and that the genomic sites occupied by origins differ from related non-origins sites. Finally, we provide evidence that origin location in Leishmania displays striking conservation with Trypanosoma brucei, despite the latter parasite replicating its chromosomes from multiple, variable strength origins. CONCLUSIONS The demonstration of chromosome replication for a single origin in Leishmania, a microbial eukaryote, has implications for the evolution of origin multiplicity and associated controls, and may explain the pervasive aneuploidy that characterizes Leishmania chromosome architecture.
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Affiliation(s)
- Catarina A Marques
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Nicholas J Dickens
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Daniel Paape
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Samantha J Campbell
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Richard McCulloch
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
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74
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Mayle R, Campbell IM, Beck CR, Yu Y, Wilson M, Shaw CA, Bjergbaek L, Lupski JR, Ira G. DNA REPAIR. Mus81 and converging forks limit the mutagenicity of replication fork breakage. Science 2015; 349:742-7. [PMID: 26273056 DOI: 10.1126/science.aaa8391] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Most spontaneous DNA double-strand breaks (DSBs) result from replication-fork breakage. Break-induced replication (BIR), a genome rearrangement-prone repair mechanism that requires the Pol32/POLD3 subunit of eukaryotic DNA Polδ, was proposed to repair broken forks, but how genome destabilization is avoided was unknown. We show that broken fork repair initially uses error-prone Pol32-dependent synthesis, but that mutagenic synthesis is limited to within a few kilobases from the break by Mus81 endonuclease and a converging fork. Mus81 suppresses template switches between both homologous sequences and diverged human Alu repetitive elements, highlighting its importance for stability of highly repetitive genomes. We propose that lack of a timely converging fork or Mus81 may propel genome instability observed in cancer.
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Affiliation(s)
- Ryan Mayle
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Ian M Campbell
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Christine R Beck
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Yang Yu
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Marenda Wilson
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Chad A Shaw
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Lotte Bjergbaek
- Department of Molecular Biology and Genetics, University of Aarhus, Aarhus 8000, Denmark
| | - James R Lupski
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA. Department of Pediatrics, and Human Genome Sequencing Center, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA. Texas Children's Hospital, Houston, TX 77030, USA
| | - Grzegorz Ira
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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75
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Vázquez E, Antequera F. Replication dynamics in fission and budding yeasts through DNA polymerase tracking. Bioessays 2015; 37:1067-73. [PMID: 26293347 PMCID: PMC5054902 DOI: 10.1002/bies.201500072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The dynamics of eukaryotic DNA polymerases has been difficult to establish because of the difficulty of tracking them along the chromosomes during DNA replication. Recent work has addressed this problem in the yeasts Schizosaccharomyces pombe and Saccharomyces cerevisiae through the engineering of replicative polymerases to render them prone to incorporating ribonucleotides at high rates. Their use as tracers of the passage of each polymerase has provided a picture of unprecedented resolution of the organization of replicons and replication origins in the two yeasts and has uncovered important differences between them. Additional studies have found an overlapping distribution of DNA polymorphisms and the junctions of Okazaki fragments along mononucleosomal DNA. This sequence instability is caused by the premature release of polymerase δ and the retention of non proof‐read DNA tracts replicated by polymerase α. The possible implementation of these new experimental approaches in multicellular organisms opens the door to the analysis of replication dynamics under a broad range of genetic backgrounds and physiological or pathological conditions.
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Affiliation(s)
- Enrique Vázquez
- Instituto de Biología, Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain
| | - Francisco Antequera
- Instituto de Biología, Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain
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76
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Ivanova D, Taylor T, Smith SL, Dimude JU, Upton AL, Mehrjouy MM, Skovgaard O, Sherratt DJ, Retkute R, Rudolph CJ. Shaping the landscape of the Escherichia coli chromosome: replication-transcription encounters in cells with an ectopic replication origin. Nucleic Acids Res 2015; 43:7865-77. [PMID: 26160884 PMCID: PMC4652752 DOI: 10.1093/nar/gkv704] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 07/01/2015] [Indexed: 01/02/2023] Open
Abstract
Each cell division requires the unwinding of millions of DNA base pairs to allow chromosome duplication and gene transcription. As DNA replication and transcription share the same template, conflicts between both processes are unavoidable and head-on collisions are thought to be particularly problematic. Surprisingly, a recent study reported unperturbed cell cycle progression in Escherichia coli cells with an ectopic replication origin in which highly transcribed rrn operons were forced to be replicated opposite to normal. In this study we have re-generated a similar strain and found the doubling time to be twice that of normal cells. Replication profiles of this background revealed significant deviations in comparison to wild-type profiles, particularly in highly transcribed regions and the termination area. These deviations were alleviated by mutations that either inactivate the termination area or destabilise RNA polymerase complexes and allow their easier displacement by replication forks. Our data demonstrate that head-on replication-transcription conflicts are highly problematic. Indeed, analysis of the replication profile of the previously published E. coli construct revealed a chromosomal rearrangement that alleviates replication-transcription conflicts in an intriguingly simple way. Our data support the idea that avoiding head-on collisions has significantly contributed to shaping the distinct architecture of bacterial chromosomes.
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Affiliation(s)
- Darja Ivanova
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK
| | - Toni Taylor
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK
| | - Sarah L Smith
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK
| | - Juachi U Dimude
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK
| | - Amy L Upton
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Mana M Mehrjouy
- The Faculty of Health Sciences, Department of Cellular and Molecular Medicine, Copenhagen University, 2200 Copenhagen N, Denmark
| | - Ole Skovgaard
- Department of Science, Systems and Models, Roskilde University, DK-4000 Roskilde, Denmark
| | - David J Sherratt
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Renata Retkute
- School of Veterinary Medicine & Science, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK
| | - Christian J Rudolph
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK
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77
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Mcm2-7 Is an Active Player in the DNA Replication Checkpoint Signaling Cascade via Proposed Modulation of Its DNA Gate. Mol Cell Biol 2015; 35:2131-43. [PMID: 25870112 DOI: 10.1128/mcb.01357-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 04/05/2015] [Indexed: 01/01/2023] Open
Abstract
The DNA replication checkpoint (DRC) monitors and responds to stalled replication forks to prevent genomic instability. How core replication factors integrate into this phosphorylation cascade is incompletely understood. Here, through analysis of a unique mcm allele targeting a specific ATPase active site (mcm2DENQ), we show that the Mcm2-7 replicative helicase has a novel DRC function as part of the signal transduction cascade. This allele exhibits normal downstream mediator (Mrc1) phosphorylation, implying DRC sensor kinase activation. However, the mutant also exhibits defective effector kinase (Rad53) activation and classic DRC phenotypes. Our previous in vitro analysis showed that the mcm2DENQ mutation prevents a specific conformational change in the Mcm2-7 hexamer. We infer that this conformational change is required for its DRC role and propose that it allosterically facilitates Rad53 activation to ensure a replication-specific checkpoint response.
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78
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Belsky JA, MacAlpine HK, Lubelsky Y, Hartemink AJ, MacAlpine DM. Genome-wide chromatin footprinting reveals changes in replication origin architecture induced by pre-RC assembly. Genes Dev 2015; 29:212-24. [PMID: 25593310 PMCID: PMC4298139 DOI: 10.1101/gad.247924.114] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Start sites of DNA replication are marked by the origin recognition complex (ORC), which coordinates Mcm2–7 helicase loading to form the prereplicative complex (pre-RC). Belsky et al. “footprinted” nucleosomes, transcription factors, and replication proteins at multiple points during the Saccharomyces cerevisiae cell cycle. This revealed a precise ORC-dependent footprint at 269 origins in G2. A separate class of inefficient origins exhibited protein occupancy only in G1. The local chromatin environment restricts the loading of the Mcm2–7 double hexamer either upstream of or downstream from the ACS. Start sites of DNA replication are marked by the origin recognition complex (ORC), which coordinates Mcm2–7 helicase loading to form the prereplicative complex (pre-RC). Although pre-RC assembly is well characterized in vitro, the process is poorly understood within the local chromatin environment surrounding replication origins. To reveal how the chromatin architecture modulates origin selection and activation, we “footprinted” nucleosomes, transcription factors, and replication proteins at multiple points during the Saccharomyces cerevisiae cell cycle. Our nucleotide-resolution protein occupancy profiles resolved a precise ORC-dependent footprint at 269 origins in G2. A separate class of inefficient origins exhibited protein occupancy only in G1, suggesting that stable ORC chromatin association in G2 is a determinant of origin efficiency. G1 nucleosome remodeling concomitant with pre-RC assembly expanded the origin nucleosome-free region and enhanced activation efficiency. Finally, the local chromatin environment restricts the loading of the Mcm2–7 double hexamer either upstream of or downstream from the ARS consensus sequence (ACS).
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Affiliation(s)
- Jason A Belsky
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA; Program in Computational Biology and Bioinformatics, Duke University, Durham, North Carolina 27708, USA
| | - Heather K MacAlpine
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA;
| | - Yoav Lubelsky
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | - Alexander J Hartemink
- Program in Computational Biology and Bioinformatics, Duke University, Durham, North Carolina 27708, USA; Department of Computer Science, Duke University, Durham, North Carolina 27708, USA
| | - David M MacAlpine
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA; Program in Computational Biology and Bioinformatics, Duke University, Durham, North Carolina 27708, USA;
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79
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A global profile of replicative polymerase usage. Nat Struct Mol Biol 2015; 22:192-198. [PMID: 25664722 PMCID: PMC4789492 DOI: 10.1038/nsmb.2962] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 12/23/2014] [Indexed: 12/19/2022]
Abstract
Three eukaryotic DNA polymerases are essential for genome replication. Polymerase (Pol) α-primase initiates each synthesis event and is rapidly replaced by processive DNA polymerases: Polɛ replicates the leading strand, whereas Polδ performs lagging-strand synthesis. However, it is not known whether this division of labor is maintained across the whole genome or how uniform it is within single replicons. Using Schizosaccharomyces pombe, we have developed a polymerase usage sequencing (Pu-seq) strategy to map polymerase usage genome wide. Pu-seq provides direct replication-origin location and efficiency data and indirect estimates of replication timing. We confirm that the division of labor is broadly maintained across an entire genome. However, our data suggest a subtle variability in the usage of the two polymerases within individual replicons. We propose that this results from occasional leading-strand initiation by Polδ followed by exchange for Polɛ.
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80
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Kunnev D, Freeland A, Qin M, Wang J, Pruitt SC. Isolation and sequencing of active origins of DNA replication by nascent strand capture and release (NSCR). J Biol Methods 2015; 2. [PMID: 26949711 DOI: 10.14440/jbm.2015.92] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Nascent strand capture and release (NSCR) is a method for isolation of short nascent strands to identify origins of DNA replication. The protocol provided involves isolation of total DNA, denaturation, size fractionation on a sucrose gradient, 5'-biotinylation of the appropriate size nucleic acids, binding to a streptavidin coated magnetic beads, intensive washing, and specific release of only the RNA-containing chimeric nascent strand DNA using ribonuclease I (RNase I). The method has been applied to mammalian cells derived from proliferative tissues and cell culture but could be used for any system where DNA replication is primed by a small RNA resulting in chimeric RNA-DNA molecules.
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Affiliation(s)
- Dimiter Kunnev
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Amy Freeland
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Maochun Qin
- Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Jianmin Wang
- Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Steven C Pruitt
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
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81
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Jeppsson K, Carlborg KK, Nakato R, Berta DG, Lilienthal I, Kanno T, Lindqvist A, Brink MC, Dantuma NP, Katou Y, Shirahige K, Sjögren C. The chromosomal association of the Smc5/6 complex depends on cohesion and predicts the level of sister chromatid entanglement. PLoS Genet 2014; 10:e1004680. [PMID: 25329383 PMCID: PMC4199498 DOI: 10.1371/journal.pgen.1004680] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 08/18/2014] [Indexed: 11/24/2022] Open
Abstract
The cohesin complex, which is essential for sister chromatid cohesion and chromosome segregation, also inhibits resolution of sister chromatid intertwinings (SCIs) by the topoisomerase Top2. The cohesin-related Smc5/6 complex (Smc5/6) instead accumulates on chromosomes after Top2 inactivation, known to lead to a buildup of unresolved SCIs. This suggests that cohesin can influence the chromosomal association of Smc5/6 via its role in SCI protection. Using high-resolution ChIP-sequencing, we show that the localization of budding yeast Smc5/6 to duplicated chromosomes indeed depends on sister chromatid cohesion in wild-type and top2-4 cells. Smc5/6 is found to be enriched at cohesin binding sites in the centromere-proximal regions in both cell types, but also along chromosome arms when replication has occurred under Top2-inhibiting conditions. Reactivation of Top2 after replication causes Smc5/6 to dissociate from chromosome arms, supporting the assumption that Smc5/6 associates with a Top2 substrate. It is also demonstrated that the amount of Smc5/6 on chromosomes positively correlates with the level of missegregation in top2-4, and that Smc5/6 promotes segregation of short chromosomes in the mutant. Altogether, this shows that the chromosomal localization of Smc5/6 predicts the presence of the chromatid segregation-inhibiting entities which accumulate in top2-4 mutated cells. These are most likely SCIs, and our results thus indicate that, at least when Top2 is inhibited, Smc5/6 facilitates their resolution.
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Affiliation(s)
- Kristian Jeppsson
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Kristian K. Carlborg
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Ryuichiro Nakato
- University of Tokyo, Institute of Molecular and Cellular Biosciences, Laboratory of Genome Structure and Function Center for Epigenetic Disease, Bunkyo-ku, Tokyo, Japan
| | - Davide G. Berta
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Ingrid Lilienthal
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Takaharu Kanno
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Arne Lindqvist
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Maartje C. Brink
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Nico P. Dantuma
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Yuki Katou
- University of Tokyo, Institute of Molecular and Cellular Biosciences, Laboratory of Genome Structure and Function Center for Epigenetic Disease, Bunkyo-ku, Tokyo, Japan
| | - Katsuhiko Shirahige
- University of Tokyo, Institute of Molecular and Cellular Biosciences, Laboratory of Genome Structure and Function Center for Epigenetic Disease, Bunkyo-ku, Tokyo, Japan
| | - Camilla Sjögren
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
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82
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Soriano I, Morafraile EC, Vázquez E, Antequera F, Segurado M. Different nucleosomal architectures at early and late replicating origins in Saccharomyces cerevisiae. BMC Genomics 2014; 15:791. [PMID: 25218085 PMCID: PMC4176565 DOI: 10.1186/1471-2164-15-791] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 09/10/2014] [Indexed: 11/10/2022] Open
Abstract
Background Eukaryotic genomes are replicated during S phase according to a temporal program. Several determinants control the timing of origin firing, including the chromatin environment and epigenetic modifications. However, how chromatin structure influences the timing of the activation of specific origins is still poorly understood. Results By performing high-resolution analysis of genome-wide nucleosome positioning we have identified different chromatin architectures at early and late replication origins. These different patterns are already established in G1 and are tightly correlated with the organization of adjacent transcription units. Moreover, specific early and late nucleosomal patterns are fixed robustly, even in rpd3 mutants in which histone acetylation and origin timing have been significantly altered. Nevertheless, higher histone acetylation levels correlate with the local modulation of chromatin structure, leading to increased origin accessibility. In addition, we conducted parallel analyses of replication and nucleosome dynamics that revealed that chromatin structure at origins is modulated during origin activation. Conclusions Our results show that early and late replication origins present distinctive nucleosomal configurations, which are preferentially associated to different genomic regions. Our data also reveal that origin structure is dynamic and can be locally modulated by histone deacetylation, as well as by origin activation. These data offer novel insight into the contribution of chromatin structure to origin selection and firing in budding yeast. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-791) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | - Mónica Segurado
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas/ Universidad de Salamanca (CSIC/USAL), Campus Miguel de Unamuno, Salamanca 37007, Spain.
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83
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Poptsova MS, Il'icheva IA, Nechipurenko DY, Panchenko LA, Khodikov MV, Oparina NY, Polozov RV, Nechipurenko YD, Grokhovsky SL. Non-random DNA fragmentation in next-generation sequencing. Sci Rep 2014; 4:4532. [PMID: 24681819 PMCID: PMC3970190 DOI: 10.1038/srep04532] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 03/13/2014] [Indexed: 12/04/2022] Open
Abstract
Next Generation Sequencing (NGS) technology is based on cutting DNA into small fragments, and their massive parallel sequencing. The multiple overlapping segments termed “reads” are assembled into a contiguous sequence. To reduce sequencing errors, every genome region should be sequenced several dozen times. This sequencing approach is based on the assumption that genomic DNA breaks are random and sequence-independent. However, previously we showed that for the sonicated restriction DNA fragments the rates of double-stranded breaks depend on the nucleotide sequence. In this work we analyzed genomic reads from NGS data and discovered that fragmentation methods based on the action of the hydrodynamic forces on DNA, produce similar bias. Consideration of this non-random DNA fragmentation may allow one to unravel what factors and to what extent influence the non-uniform coverage of various genomic regions.
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Affiliation(s)
| | - Irina A Il'icheva
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | | | | | - Mingian V Khodikov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | - Nina Y Oparina
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | - Robert V Polozov
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Puschino, Moscow Region, Russia
| | - Yury D Nechipurenko
- 1] Department of Physics, Moscow State University, Moscow, Russia [2] Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | - Sergei L Grokhovsky
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
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84
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GC-rich DNA elements enable replication origin activity in the methylotrophic yeast Pichia pastoris. PLoS Genet 2014; 10:e1004169. [PMID: 24603708 PMCID: PMC3945215 DOI: 10.1371/journal.pgen.1004169] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 12/25/2013] [Indexed: 11/19/2022] Open
Abstract
The well-studied DNA replication origins of the model budding and fission yeasts are A/T-rich elements. However, unlike their yeast counterparts, both plant and metazoan origins are G/C-rich and are associated with transcription start sites. Here we show that an industrially important methylotrophic budding yeast, Pichia pastoris, simultaneously employs at least two types of replication origins--a G/C-rich type associated with transcription start sites and an A/T-rich type more reminiscent of typical budding and fission yeast origins. We used a suite of massively parallel sequencing tools to map and dissect P. pastoris origins comprehensively, to measure their replication dynamics, and to assay the global positioning of nucleosomes across the genome. Our results suggest that some functional overlap exists between promoter sequences and G/C-rich replication origins in P. pastoris and imply an evolutionary bifurcation of the modes of replication initiation.
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85
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Baker A, Bechhoefer J. Inferring the spatiotemporal DNA replication program from noisy data. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:032703. [PMID: 24730871 DOI: 10.1103/physreve.89.032703] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Indexed: 06/03/2023]
Abstract
We generalize a stochastic model of DNA replication to the case where replication-origin-initiation rates vary locally along the genome and with time. Using this generalized model, we address the inverse problem of inferring initiation rates from experimental data concerning replication in cell populations. Previous work based on curve fitting depended on arbitrarily chosen functional forms for the initiation rate, with free parameters that were constrained by the data. We introduce a nonparametric method of inference that is based on Gaussian process regression. The method replaces specific assumptions about the functional form of the initiation rate with more general prior expectations about the smoothness of variation of this rate, along the genome and in time. Using this inference method, we recover, with high precision, simulated replication schemes from noisy data that are typical of current experiments.
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Affiliation(s)
- A Baker
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | - J Bechhoefer
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
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86
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Hawkins M, Retkute R, Müller CA, Saner N, Tanaka TU, de Moura APS, Nieduszynski CA. High-resolution replication profiles define the stochastic nature of genome replication initiation and termination. Cell Rep 2013; 5:1132-41. [PMID: 24210825 PMCID: PMC3898788 DOI: 10.1016/j.celrep.2013.10.014] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 09/18/2013] [Accepted: 10/07/2013] [Indexed: 12/23/2022] Open
Abstract
Eukaryotic genome replication is stochastic, and each cell uses a different cohort of replication origins. We demonstrate that interpreting high-resolution Saccharomyces cerevisiae genome replication data with a mathematical model allows quantification of the stochastic nature of genome replication, including the efficiency of each origin and the distribution of termination events. Single-cell measurements support the inferred values for stochastic origin activation time. A strain, in which three origins were inactivated, confirmed that the distribution of termination events is primarily dictated by the stochastic activation time of origins. Cell-to-cell variability in origin activity ensures that termination events are widely distributed across virtually the whole genome. We propose that the heterogeneity in origin usage contributes to genome stability by limiting potentially deleterious events from accumulating at particular loci. Deep sequencing reveals a high-resolution view of genome replication dynamics Genome-wide modeling and single-cell imaging reveal stochastic origin activity Origin activity determines the location of replication termination events Termination events are widely distributed across the whole genome
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Affiliation(s)
- Michelle Hawkins
- Centre for Genetics and Genomics, School of Life Sciences, Queen's Medical Centre, The University of Nottingham, Nottingham NG7 2UH, UK
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