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Castellano CM, Lacroix L, Mathis E, Prorok P, Hennion M, Lopez-Rubio JJ, Méchali M, Gomes A. The genetic landscape of origins of replication in P. falciparum. Nucleic Acids Res 2024; 52:660-676. [PMID: 38038269 PMCID: PMC10810204 DOI: 10.1093/nar/gkad1103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 10/18/2023] [Accepted: 11/01/2023] [Indexed: 12/02/2023] Open
Abstract
Various origin mapping approaches have enabled genome-wide identification of origins of replication (ORI) in model organisms, but only a few studies have focused on divergent organisms. By employing three complementary approaches we provide a high-resolution map of ORIs in Plasmodium falciparum, the deadliest human malaria parasite. We profiled the distribution of origin of recognition complex (ORC) binding sites by ChIP-seq of two PfORC subunits and mapped active ORIs using NFS and SNS-seq. We show that ORIs lack sequence specificity but are not randomly distributed, and group in clusters. Licensing is biased towards regions of higher GC content and associated with G-quadruplex forming sequences (G4FS). While strong transcription likely enhances firing, active origins are depleted from transcription start sites. Instead, most accumulate in transcriptionally active gene bodies. Single molecule analysis of nanopore reads containing multiple initiation events, which could have only come from individual nuclei, showed a relationship between the replication fork pace and the distance to the nearest origin. While some similarities were drawn with the canonic eukaryote model, the distribution of ORIs in P. falciparum is likely shaped by unique genomic features such as extreme AT-richness-a product of evolutionary pressure imposed by the parasitic lifestyle.
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Affiliation(s)
| | - Laurent Lacroix
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Paris, France
| | - Emilie Mathis
- LPHI, CNRS, Université de Montpellier, 34095 Montpellier, France
| | - Paulina Prorok
- Institute of Human Genetics, CNRS, 34396 Montpellier, France
| | - Magali Hennion
- Université Paris Cité, CNRS, Epigenetics and Cell Fate, F-75013 Paris, France
| | | | - Marcel Méchali
- Institute of Human Genetics, CNRS, 34396 Montpellier, France
| | - Ana Rita Gomes
- LPHI, CNRS, Université de Montpellier, 34095 Montpellier, France
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2
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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: 14] [Impact Index Per Article: 2.0] [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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3
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Miotto B. Comment l’approche génomique aide à comprendre le processus d’initiation de la réplication. Med Sci (Paris) 2017; 33:143-150. [DOI: 10.1051/medsci/20173302009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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4
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Gutierrez C, Desvoyes B, Vergara Z, Otero S, Sequeira-Mendes J. Links of genome replication, transcriptional silencing and chromatin dynamics. CURRENT OPINION IN PLANT BIOLOGY 2016; 34:92-99. [PMID: 27816819 DOI: 10.1016/j.pbi.2016.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 10/06/2016] [Accepted: 10/13/2016] [Indexed: 06/06/2023]
Abstract
Genome replication in multicellular organisms involves duplication of both the genetic material and the epigenetic information stored in DNA and histones. In some cases, the DNA replication process provides a window of opportunity for resetting chromatin marks in the genome of the future daughter cells instead of transferring them identical copies. This crucial step of genome replication depends on the correct function of DNA replication factors and the coordination between replication and transcription in proliferating cells. In fact, the histone composition and modification status appears to be intimately associated with the proliferation potential of cells within developing organs. Here we discuss these topics in the light of recent advances in our understanding of how genome replication, transcriptional silencing and chromatin dynamics are coordinated in proliferating cells.
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Affiliation(s)
- Crisanto Gutierrez
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain.
| | - Bénédicte Desvoyes
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
| | - Zaida Vergara
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
| | - Sofía Otero
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
| | - Joana Sequeira-Mendes
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
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5
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Lombraña R, Álvarez A, Fernández-Justel JM, Almeida R, Poza-Carrión C, Gomes F, Calzada A, Requena JM, Gómez M. Transcriptionally Driven DNA Replication Program of the Human Parasite Leishmania major. Cell Rep 2016; 16:1774-1786. [PMID: 27477279 DOI: 10.1016/j.celrep.2016.07.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 05/26/2016] [Accepted: 07/01/2016] [Indexed: 01/04/2023] Open
Abstract
Faithful inheritance of eukaryotic genomes requires the orchestrated activation of multiple DNA replication origins (ORIs). Although origin firing is mechanistically conserved, how origins are specified and selected for activation varies across different model systems. Here, we provide a complete analysis of the nucleosomal landscape and replication program of the human parasite Leishmania major, building on a better evolutionary understanding of replication organization in Eukarya. We found that active transcription is a driving force for the nucleosomal organization of the L. major genome and that both the spatial and the temporal program of DNA replication can be explained as associated to RNA polymerase kinetics. This simple scenario likely provides flexibility and robustness to deal with the environmental changes that impose alterations in the genetic programs during parasitic life cycle stages. Our findings also suggest that coupling replication initiation to transcription elongation could be an ancient solution used by eukaryotic cells for origin maintenance.
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Affiliation(s)
- Rodrigo Lombraña
- Functional Organization of the Genome Group, Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Alba Álvarez
- Functional Organization of the Genome Group, Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - José Miguel Fernández-Justel
- Functional Organization of the Genome Group, Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Ricardo Almeida
- Functional Organization of the Genome Group, Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - César Poza-Carrión
- Functional Organization of the Genome Group, Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Fábia Gomes
- Centro Nacional de Biotecnología (CSIC), Darwin 3, 28049 Madrid, Spain
| | - Arturo Calzada
- Centro Nacional de Biotecnología (CSIC), Darwin 3, 28049 Madrid, Spain
| | - José María Requena
- Functional Organization of the Genome Group, Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - María Gómez
- Functional Organization of the Genome Group, Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Nicolás Cabrera 1, 28049 Madrid, Spain.
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6
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Sequeira-Mendes J, Gutierrez C. Links between genome replication and chromatin landscapes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 83:38-51. [PMID: 25847096 DOI: 10.1111/tpj.12847] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Revised: 03/27/2015] [Accepted: 04/01/2015] [Indexed: 05/07/2023]
Abstract
Post-embryonic organogenesis in plants requires the continuous production of cells in the organ primordia, their expansion and a coordinated exit to differentiation. Genome replication is one of the most important processes that occur during the cell cycle, as the maintenance of genomic integrity is of primary relevance for development. As it is chromatin that must be duplicated, a strict coordination occurs between DNA replication, the deposition of new histones, and the introduction of histone modifications and variants. In turn, the chromatin landscape affects several stages during genome replication. Thus, chromatin accessibility is crucial for the initial stages and to specify the location of DNA replication origins with different chromatin signatures. The chromatin landscape also determines the timing of activation during the S phase. Genome replication must occur fully, but only once during each cell cycle. The re-replication avoidance mechanisms rely primarily on restricting the availability of certain replication factors; however, the presence of specific histone modifications are also revealed as contributing to the mechanisms that avoid re-replication, in particular for heterochromatin replication. We provide here an update of genome replication mostly focused on data from Arabidopsis, and the advances that genomic approaches are likely to provide in the coming years. The data available, both in plants and animals, point to the relevance of the chromatin landscape in genome replication, and require a critical evaluation of the existing views about the nature of replication origins, the mechanisms of origin specification and the relevance of epigenetic modifications for genome replication.
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Affiliation(s)
- Joana Sequeira-Mendes
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049, Madrid, Spain
| | - Crisanto Gutierrez
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049, Madrid, Spain
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7
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Lombraña R, Almeida R, Álvarez A, Gómez M. R-loops and initiation of DNA replication in human cells: a missing link? Front Genet 2015; 6:158. [PMID: 25972891 PMCID: PMC4412123 DOI: 10.3389/fgene.2015.00158] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2015] [Accepted: 04/08/2015] [Indexed: 11/13/2022] Open
Abstract
The unanticipated widespread occurrence of stable hybrid DNA/RNA structures (R-loops) in human cells and the increasing evidence of their involvement in several human malignancies have invigorated the research on R-loop biology in recent years. Here we propose that physiological R-loop formation at CpG island promoters can contribute to DNA replication origin specification at these regions, the most efficient replication initiation sites in mammalian cells. Quite likely, this occurs by the strand-displacement reaction activating the formation of G-quadruplex structures that target the origin recognition complex (ORC) in the single-stranded conformation. In agreement with this, we found that R-loops co-localize with the ORC within the same CpG island region in a significant fraction of these efficient replication origins, precisely at the position displaying the highest density of G4 motifs. This scenario builds on the connection between transcription and replication in human cells and suggests that R-loop dysregulation at CpG island promoter-origins might contribute to the phenotype of DNA replication abnormalities and loss of genome integrity detected in cancer cells.
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Affiliation(s)
- Rodrigo Lombraña
- Functional Organization of the Genome Group, Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid , Madrid, Spain
| | - Ricardo Almeida
- Functional Organization of the Genome Group, Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid , Madrid, Spain
| | - Alba Álvarez
- Functional Organization of the Genome Group, Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid , Madrid, Spain
| | - María Gómez
- Functional Organization of the Genome Group, Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid , Madrid, Spain
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8
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Mason PH, Domínguez D JF, Winter B, Grignolio A. Hidden in plain view: degeneracy in complex systems. Biosystems 2014; 128:1-8. [PMID: 25543071 DOI: 10.1016/j.biosystems.2014.12.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 12/20/2014] [Accepted: 12/23/2014] [Indexed: 12/27/2022]
Abstract
Degeneracy is a word with two meanings. The popular usage of the word denotes deviance and decay. In scientific discourse, degeneracy refers to the idea that different pathways can lead to the same output. In the biological sciences, the concept of degeneracy has been ignored for a few key reasons. Firstly, the word "degenerate" in popular culture has negative, emotionally powerful associations that do not inspire scientists to consider its technical meaning. Secondly, the tendency of searching for single causes of natural and social phenomena means that scientists can overlook the multi-stranded relationships between cause and effect. Thirdly, degeneracy and redundancy are often confused with each other. Degeneracy refers to dissimilar structures that are functionally similar while redundancy refers to identical structures. Degeneracy can give rise to novelty in ways that redundancy cannot. From genetic codes to immunology, vaccinology and brain development, degeneracy is a crucial part of how complex systems maintain their functional integrity. This review article discusses how the scientific concept of degeneracy was imported into genetics from physics and was later introduced to immunology and neuroscience. Using examples of degeneracy in immunology, neuroscience and linguistics, we demonstrate that degeneracy is a useful way of understanding how complex systems function. Reviewing the history and theoretical scope of degeneracy allows its usefulness to be better appreciated, its coherency to be further developed, and its application to be more quickly realized.
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Affiliation(s)
- P H Mason
- Woolcock Institute of Medical Research, University of Sydney, 431 Glebe Point Road, Glebe, 2037 NSW, Australia.
| | - J F Domínguez D
- Experimental Neuropsychology Research Unit, School of Psychological Sciences, Monash University, Australia
| | - B Winter
- Cognitive and Information Sciences, University of California, Merced 5200 North Lake Rd., Merced, CA 95343, USA
| | - A Grignolio
- Section and Museum of History of Medicine, University of Rome "La Sapienza", viale dell'Università, 34a 00185 Rome, Italy
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9
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Li WC, Zhong ZJ, Zhu PP, Deng EZ, Ding H, Chen W, Lin H. Sequence analysis of origins of replication in the Saccharomyces cerevisiae genomes. Front Microbiol 2014; 5:574. [PMID: 25477864 PMCID: PMC4235382 DOI: 10.3389/fmicb.2014.00574] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 10/11/2014] [Indexed: 12/26/2022] Open
Abstract
DNA replication is a highly precise process that is initiated from origins of replication (ORIs) and is regulated by a set of regulatory proteins. The mining of DNA sequence information will be not only beneficial for understanding the regulatory mechanism of replication initiation but also for accurately identifying ORIs. In this study, the GC profile and GC skew were calculated to analyze the compositional bias in the Saccharomyces cerevisiae genome. We found that the GC profile in the region of ORIs is significantly lower than that in the flanking regions. By calculating the information redundancy, an estimation of the correlation of nucleotides, we found that the intensity of adjoining correlation in ORIs is dramatically higher than that in flanking regions. Furthermore, the relationships between ORIs and nucleosomes as well as transcription start sites were investigated. Results showed that ORIs are usually not occupied by nucleosomes. Finally, we calculated the distribution of ORIs in yeast chromosomes and found that most ORIs are in transcription terminal regions. We hope that these results will contribute to the identification of ORIs and the study of DNA replication mechanisms.
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Affiliation(s)
- Wen-Chao Li
- Key Laboratory for Neuro-Information of Ministry of Education, Center of Bioinformatics, School of Life Science and Technology, University of Electronic Science and Technology of China Chengdu, China
| | - Zhe-Jin Zhong
- Key Laboratory for Neuro-Information of Ministry of Education, Center of Bioinformatics, School of Life Science and Technology, University of Electronic Science and Technology of China Chengdu, China
| | - Pan-Pan Zhu
- Key Laboratory for Neuro-Information of Ministry of Education, Center of Bioinformatics, School of Life Science and Technology, University of Electronic Science and Technology of China Chengdu, China
| | - En-Ze Deng
- Key Laboratory for Neuro-Information of Ministry of Education, Center of Bioinformatics, School of Life Science and Technology, University of Electronic Science and Technology of China Chengdu, China
| | - Hui Ding
- Key Laboratory for Neuro-Information of Ministry of Education, Center of Bioinformatics, School of Life Science and Technology, University of Electronic Science and Technology of China Chengdu, China
| | - Wei Chen
- Department of Physics, School of Sciences and Center for Genomics and Computational Biology, Hebei United University Tangshan, China
| | - Hao Lin
- Key Laboratory for Neuro-Information of Ministry of Education, Center of Bioinformatics, School of Life Science and Technology, University of Electronic Science and Technology of China Chengdu, China
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10
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Abstract
Enhancer elements regulate the tissue- and developmental-stage-specific expression of genes. Recent estimates suggest that there are more than 50,000 enhancers in mammalian cells. At least a subset of enhancers has been shown to recruit RNA polymerase II transcription complexes and to generate enhancer transcripts. Here, we provide an overview of enhancer function and discuss how transcription of enhancers or enhancer-generated transcripts could contribute to the regulation of gene expression during development and differentiation.
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11
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Olszewski P, Szambowska A, Barałska S, Narajczyk M, Węgrzyn G, Glinkowska M. A dual promoter system regulating λ DNA replication initiation. Nucleic Acids Res 2014; 42:4450-62. [PMID: 24500197 PMCID: PMC3985674 DOI: 10.1093/nar/gku103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Transcription and DNA replication are tightly regulated to ensure coordination of gene expression with growth conditions and faithful transmission of genetic material to progeny. A large body of evidence has accumulated, indicating that encounters between protein machineries carrying out DNA and RNA synthesis occur in vivo and may have important regulatory consequences. This feature may be exacerbated in the case of compact genomes, like the one of bacteriophage λ, used in our study. Transcription that starts at the rightward pR promoter and proceeds through the λ origin of replication and downstream of it was proven to stimulate the initiation of λ DNA replication. Here, we demonstrate that the activity of a convergently oriented pO promoter decreases the efficiency of transcription starting from pR. Our results show, however, that a lack of the functional pO promoter negatively influences λ phage and λ-derived plasmid replication. We present data, suggesting that this effect is evoked by the enhanced level of the pR-driven transcription, occurring in the presence of the defective pO, which may result in the impeded formation of the replication initiation complex. Our data suggest that the cross talk between the two promoters regulates λ DNA replication and coordinates transcription and replication processes.
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Affiliation(s)
- Paweł Olszewski
- Department of Molecular Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland, Laboratory of Molecular Biology (affiliated with the University of Gdańsk), Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Wita Stwosza 59, 80-308 Gdańsk, Poland and Laboratory of Electron Microscopy, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
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12
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Abstract
The onset of genomic DNA synthesis requires precise interactions of specialized initiator proteins with DNA at sites where the replication machinery can be loaded. These sites, defined as replication origins, are found at a few unique locations in all of the prokaryotic chromosomes examined so far. However, replication origins are dispersed among tens of thousands of loci in metazoan chromosomes, thereby raising questions regarding the role of specific nucleotide sequences and chromatin environment in origin selection and the mechanisms used by initiators to recognize replication origins. Close examination of bacterial and archaeal replication origins reveals an array of DNA sequence motifs that position individual initiator protein molecules and promote initiator oligomerization on origin DNA. Conversely, the need for specific recognition sequences in eukaryotic replication origins is relaxed. In fact, the primary rule for origin selection appears to be flexibility, a feature that is modulated either by structural elements or by epigenetic mechanisms at least partly linked to the organization of the genome for gene expression.
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Affiliation(s)
- Alan C Leonard
- Department of Biological Sciences, Florida Institute of Technology, Melbourne, Florida 32901
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13
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Lombraña R, Almeida R, Revuelta I, Madeira S, Herranz G, Saiz N, Bastolla U, Gómez M. High-resolution analysis of DNA synthesis start sites and nucleosome architecture at efficient mammalian replication origins. EMBO J 2013; 32:2631-44. [PMID: 23995398 DOI: 10.1038/emboj.2013.195] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 08/07/2013] [Indexed: 11/09/2022] Open
Abstract
DNA replication origins are poorly characterized genomic regions that are essential to recruit and position the initiation complex to start DNA synthesis. Despite the lack of specific replicator sequences, initiation of replication does not occur at random sites in the mammalian genome. This has lead to the view that DNA accessibility could be a major determinant of mammalian origins. Here, we performed a high-resolution analysis of nucleosome architecture and initiation sites along several origins of different genomic location and firing efficiencies. We found that mammalian origins are highly variable in nucleosome conformation and initiation patterns. Strikingly, initiation sites at efficient CpG island-associated origins always occur at positions of high-nucleosome occupancy. Origin recognition complex (ORC) binding sites, however, occur at adjacent but distinct positions marked by labile nucleosomes. We also found that initiation profiles mirror nucleosome architecture, both at endogenous origins and at a transgene in a heterologous system. Our studies provide a unique insight into the relationship between chromatin structure and initiation sites in the mammalian genome that has direct implications for how the replication programme can be accommodated to diverse epigenetic scenarios.
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Affiliation(s)
- Rodrigo Lombraña
- 1Functional Organization of the Genome Group, Centro de Biología Molecular 'Severo Ochoa', Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid (CSIC/UAM), Madrid, Spain
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14
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Valenzuela MS. Initiation of DNA Replication in the Human Genome. HEREDITARY GENETICS : CURRENT RESEARCH 2012; Suppl 1:4903. [PMID: 24511453 PMCID: PMC3915928 DOI: 10.4172/2161-1041.s1-003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Replication of the human genome relies on the presence of thousands of origins distributed along each of the chromosomes. The activation of these origins occurs in a highly regulated manner to ensure that chromosomes are faithfully duplicated only once during each cell cycle. Failure in this regulation can lead to abnormal cell proliferation, or/and genomic instability, the hallmarks of cancer cells. The mechanisms determining how, when, and where origins are activated remains still a mystery. However recent technological advances have facilitated the study of DNA replication in a genome-wide scale, and have provided a wealth of information on several features of this process. Here we present an overview of the current progress on our understanding of the initiation step of DNA replication in human cells, and its relationship to abnormal cell proliferation.
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Affiliation(s)
- Manuel S. Valenzuela
- Department of Biochemistry and Cancer Biology, School of Medicine, Meharry Medical College, 1005 D.B. Todd Jr. Boulevard, Nashville, TN 37208, USA
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