1
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D'Alfonso A, Micheli G, Camilloni G. rDNA transcription, replication and stability in Saccharomyces cerevisiae. Semin Cell Dev Biol 2024; 159-160:1-9. [PMID: 38244478 DOI: 10.1016/j.semcdb.2024.01.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 12/20/2023] [Accepted: 01/10/2024] [Indexed: 01/22/2024]
Abstract
The ribosomal DNA locus (rDNA) is central for the functioning of cells because it encodes ribosomal RNAs, key components of ribosomes, and also because of its links to fundamental metabolic processes, with significant impact on genome integrity and aging. The repetitive nature of the rDNA gene units forces the locus to maintain sequence homogeneity through recombination processes that are closely related to genomic stability. The co-presence of basic DNA transactions, such as replication, transcription by major RNA polymerases, and recombination, in a defined and restricted area of the genome is of particular relevance as it affects the stability of the rDNA locus by both direct and indirect mechanisms. This condition is well exemplified by the rDNA of Saccharomyces cerevisiae. In this review we summarize essential knowledge on how the complexity and overlap of different processes contribute to the control of rDNA and genomic stability in this model organism.
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Affiliation(s)
- Anna D'Alfonso
- Dipartimento di Biologia e Biotecnologie C. Darwin, Università degli studi di Roma, Sapienza, Rome, Italy
| | - Gioacchino Micheli
- Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche, Rome, Italy
| | - Giorgio Camilloni
- Dipartimento di Biologia e Biotecnologie C. Darwin, Università degli studi di Roma, Sapienza, Rome, Italy.
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2
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Sadler DE, Watts PC, Uusi-Heikkilä S. Directional selection, not the direction of selection, affects telomere length and copy number at ribosomal RNA loci. Sci Rep 2024; 14:12162. [PMID: 38802448 PMCID: PMC11130246 DOI: 10.1038/s41598-024-63030-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Accepted: 05/23/2024] [Indexed: 05/29/2024] Open
Abstract
Many fisheries exert directional selection on traits such as body size and growth rate. Whether directional selection impacts regions of the genome associated with traits related to growth is unknown. To address this issue, we characterised copy number variation in three regions of the genome associated with cell division, (1) telomeric DNA, (2) loci transcribed as ribosomal RNA (rDNA), and (3) mitochondrial DNA (mtDNA), in three selection lines of zebrafish reared at three temperatures (22 °C, 28 °C, and 34 °C). Selection lines differed in (1) the direction of selection (two lines experienced directional selection for large or small body size) and (2) whether they experienced any directional selection itself. Lines that had experienced directional selection were smaller, had lower growth rate, shorter telomeres, and lower rDNA copy number than the line that experiencing no directional selection. Neither telomere length nor rDNA copy number were affected by temperature. In contrast, mtDNA content increased at elevated temperature but did not differ among selection lines. Though directional selection impacts rDNA and telomere length, direction of such selection did not matter, whereas mtDNA acts as a stress marker for temperature. Future work should examine the consequences of these genomic changes in natural fish stocks.
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Affiliation(s)
- Daniel E Sadler
- Department of Biological and Environmental Science, University of Jyväskylä, 40014, Jyväskylä, Finland.
| | - Phillip C Watts
- Department of Biological and Environmental Science, University of Jyväskylä, 40014, Jyväskylä, Finland
| | - Silva Uusi-Heikkilä
- Department of Biological and Environmental Science, University of Jyväskylä, 40014, Jyväskylä, Finland
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3
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Cook D, Kozmin SG, Yeh E, Petes TD, Bloom K. Dicentric chromosomes are resolved through breakage and repair at their centromeres. Chromosoma 2024; 133:117-134. [PMID: 38165460 PMCID: PMC11180013 DOI: 10.1007/s00412-023-00814-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 11/11/2023] [Accepted: 12/21/2023] [Indexed: 01/03/2024]
Abstract
Chromosomes with two centromeres provide a unique opportunity to study chromosome breakage and DNA repair using completely endogenous cellular machinery. Using a conditional transcriptional promoter to control the second centromere, we are able to activate the dicentric chromosome and follow the appearance of DNA repair products. We find that the rate of appearance of DNA repair products resulting from homology-based mechanisms exceeds the expected rate based on their limited centromere homology (340 bp) and distance from one another (up to 46.3 kb). In order to identify whether DNA breaks originate in the centromere, we introduced 12 single-nucleotide polymorphisms (SNPs) into one of the centromeres. Analysis of the distribution of SNPs in the recombinant centromeres reveals that recombination was initiated with about equal frequency within the conserved centromere DNA elements CDEII and CDEIII of the two centromeres. The conversion tracts range from about 50 bp to the full length of the homology between the two centromeres (340 bp). Breakage and repair events within and between the centromeres can account for the efficiency and distribution of DNA repair products. We propose that in addition to providing a site for kinetochore assembly, the centromere may be a point of stress relief in the face of genomic perturbations.
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Affiliation(s)
- Diana Cook
- Department of Biology, University of North Carolina Chapel Hill, Chapel Hill, NC, 27599-3280, USA
| | - Stanislav G Kozmin
- Department of Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Elaine Yeh
- Department of Biology, University of North Carolina Chapel Hill, Chapel Hill, NC, 27599-3280, USA
| | - Thomas D Petes
- Department of Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Kerry Bloom
- Department of Biology, University of North Carolina Chapel Hill, Chapel Hill, NC, 27599-3280, USA.
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4
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Jiang S, Cai Z, Wang Y, Zeng C, Zhang J, Yu W, Su C, Zhao S, Chen Y, Shen Y, Ma Y, Cai Y, Dai J. High plasticity of ribosomal DNA organization in budding yeast. Cell Rep 2024; 43:113742. [PMID: 38324449 DOI: 10.1016/j.celrep.2024.113742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 12/12/2023] [Accepted: 01/19/2024] [Indexed: 02/09/2024] Open
Abstract
In eukaryotic genomes, rDNA generally resides as a highly repetitive and dynamic structure, making it difficult to study. Here, a synthetic rDNA array on chromosome III in budding yeast was constructed to serve as the sole source of rRNA. Utilizing the loxPsym site within each rDNA repeat and the Cre recombinase, we were able to reduce the copy number to as few as eight copies. Additionally, we constructed strains with two or three rDNA arrays and found that the presence of multiple arrays did not affect the formation of a single nucleolus. Although alteration of the position and number of rDNA arrays did impact the three-dimensional genome structure, the additional rDNA arrays had no deleterious influence on cell growth or transcriptomes. Overall, this study sheds light on the high plasticity of rDNA organization and opens up opportunities for future rDNA engineering.
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Affiliation(s)
- Shuangying Jiang
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.
| | - Zelin Cai
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yun Wang
- BGI Research, BGI, Shenzhen 518083, China; Guangdong Provincial Key Laboratory of Genome Read and Write, BGI-Shenzhen, Shenzhen 518120, China
| | - Cheng Zeng
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Jiaying Zhang
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China; School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, China
| | - Wenfei Yu
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chenghao Su
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Shijun Zhao
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ying Chen
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China; BGI Research, BGI, Shenzhen 518083, China
| | - Yue Shen
- BGI Research, BGI, Shenzhen 518083, China; Guangdong Provincial Key Laboratory of Genome Read and Write, BGI-Shenzhen, Shenzhen 518120, China
| | - Yingxin Ma
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Yizhi Cai
- Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7DN, UK.
| | - Junbiao Dai
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China; Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Key Laboratory of Synthetic Biology, Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China; College of Life Sciences and Oceanography, Shenzhen University, 1066 Xueyuan Road, Shenzhen 518055, China.
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5
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Normand C, Dez C, Dauban L, Queille S, Danché S, Abderrahmane S, Beckouet F, Gadal O. RNA polymerase I mutant affects ribosomal RNA processing and ribosomal DNA stability. RNA Biol 2024; 21:1-16. [PMID: 39049162 PMCID: PMC11275518 DOI: 10.1080/15476286.2024.2381910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 07/12/2024] [Accepted: 07/15/2024] [Indexed: 07/27/2024] Open
Abstract
Transcription is a major contributor to genomic instability. The ribosomal RNA (rDNA) gene locus consists of a head-to-tail repeat of the most actively transcribed genes in the genome. RNA polymerase I (RNAPI) is responsible for massive rRNA production, and nascent rRNA is co-transcriptionally assembled with early assembly factors in the yeast nucleolus. In Saccharomyces cerevisiae, a mutant form of RNAPI bearing a fusion of the transcription factor Rrn3 with RNAPI subunit Rpa43 (CARA-RNAPI) has been described previously. Here, we show that the CARA-RNAPI allele results in a novel type of rRNA processing defect, associated with rDNA genomic instability. A fraction of the 35S rRNA produced in CARA-RNAPI mutant escapes processing steps and accumulates. This accumulation is increased in mutants affecting exonucleolytic activities of the exosome complex. CARA-RNAPI is synthetic lethal with monopolin mutants that are known to affect the rDNA condensation. CARA-RNAPI strongly impacts rDNA organization and increases rDNA copy number variation. Reduced rDNA copy number suppresses lethality, suggesting that the chromosome segregation defect is caused by genomic rDNA instability. We conclude that a constitutive association of Rrn3 with transcribing RNAPI results in the accumulation of rRNAs that escape normal processing, impacting rDNA organization and affecting rDNA stability.
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Affiliation(s)
- Christophe Normand
- Molecular, Cellular and Developmental Biology Unit (MCD), Centre de Biologie Integrative (CBI), University of Toulouse, CNRS, UPS, Toulouse, France
| | - Christophe Dez
- Molecular, Cellular and Developmental Biology Unit (MCD), Centre de Biologie Integrative (CBI), University of Toulouse, CNRS, UPS, Toulouse, France
| | - Lise Dauban
- Molecular, Cellular and Developmental Biology Unit (MCD), Centre de Biologie Integrative (CBI), University of Toulouse, CNRS, UPS, Toulouse, France
| | - Sophie Queille
- Molecular, Cellular and Developmental Biology Unit (MCD), Centre de Biologie Integrative (CBI), University of Toulouse, CNRS, UPS, Toulouse, France
| | - Sarah Danché
- Molecular, Cellular and Developmental Biology Unit (MCD), Centre de Biologie Integrative (CBI), University of Toulouse, CNRS, UPS, Toulouse, France
| | - Sarra Abderrahmane
- Molecular, Cellular and Developmental Biology Unit (MCD), Centre de Biologie Integrative (CBI), University of Toulouse, CNRS, UPS, Toulouse, France
| | - Frederic Beckouet
- Molecular, Cellular and Developmental Biology Unit (MCD), Centre de Biologie Integrative (CBI), University of Toulouse, CNRS, UPS, Toulouse, France
| | - Olivier Gadal
- Molecular, Cellular and Developmental Biology Unit (MCD), Centre de Biologie Integrative (CBI), University of Toulouse, CNRS, UPS, Toulouse, France
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6
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Nguyen TH, Kang BY, Kim HH. Chromosomal dynamics in Senna: comparative PLOP-FISH analysis of tandem repeats and flow cytometric nuclear genome size estimations. FRONTIERS IN PLANT SCIENCE 2023; 14:1288220. [PMID: 38173930 PMCID: PMC10762312 DOI: 10.3389/fpls.2023.1288220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 11/08/2023] [Indexed: 01/05/2024]
Abstract
Introduction Tandem repeats (TRs) occur abundantly in plant genomes. They play essential roles that affect genome organization and evolution by inducing or generating chromosomal rearrangements such as duplications, deletions, inversions, and translocations. These impact gene expression and chromosome structure and even contribute to the emergence of new species. Method We investigated the effects of TRs on speciation in Senna genus by performing a comparative analysis using fluorescence in situ hybridization (FISH) with S. tora-specific TR probes. We examined the chromosomal distribution of these TRs and compared the genome sizes of seven Senna species (estimated using flow cytometry) to better understand their evolutionary relationships. Results Two (StoTR03_159 and StoTR04_55) of the nine studied TRs were not detected in any of the seven Senna species, whereas the remaining seven were found in all or some species with patterns that were similar to or contrasted with those of S. tora. Of these studies species, only S. angulata showed significant genome rearrangements and dysploid karyotypes resembling those of S. tora. The genome sizes varied among these species and did not positively correlate with chromosome number. Notably, S. angulata had the fewest chromosomes (2n = 22) but a relatively large genome size. Discussion These findings reveal the dynamics of TRs and provide a cytogenetic depiction of chromosomal rearrangements during speciation in Senna. To further elucidate the dynamics of repeat sequences in Senna, future studies must include related species and extensive repeatomic studies, including those on transposable elements.
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Affiliation(s)
| | | | - Hyun Hee Kim
- Chromosome Research Institute, Department of Chemistry & Life Science, Sahmyook University, Seoul, Republic of Korea
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7
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Sasaki M, Kobayashi T. Regulatory processes that maintain or alter ribosomal DNA stability during the repair of programmed DNA double-strand breaks. Genes Genet Syst 2023; 98:103-119. [PMID: 35922917 DOI: 10.1266/ggs.22-00046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Organisms have evolved elaborate mechanisms that maintain genome stability. Deficiencies in these mechanisms result in changes to the nucleotide sequence as well as copy number and structural variations in the genome. Genome instability has been implicated in numerous human diseases. However, genomic alterations can also be beneficial as they are an essential part of the evolutionary process. Organisms sometimes program genomic changes that drive genetic and phenotypic diversity. Therefore, genome alterations can have both positive and negative impacts on cellular growth and functions, which underscores the need to control the processes that restrict or induce such changes to the genome. The ribosomal RNA gene (rDNA) is highly abundant in eukaryotic genomes, forming a cluster where numerous rDNA copies are tandemly arrayed. Budding yeast can alter the stability of its rDNA cluster by changing the rDNA copy number within the cluster or by producing extrachromosomal rDNA circles. Here, we review the mechanisms that regulate the stability of the budding yeast rDNA cluster during repair of DNA double-strand breaks that are formed in response to programmed DNA replication fork arrest.
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Affiliation(s)
- Mariko Sasaki
- Laboratory of Genome Regeneration, Institute for Quantitative Biosciences (IQB), The University of Tokyo
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo
| | - Takehiko Kobayashi
- Laboratory of Genome Regeneration, Institute for Quantitative Biosciences (IQB), The University of Tokyo
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo
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8
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Kindelay SM, Maggert KA. Under the magnifying glass: The ups and downs of rDNA copy number. Semin Cell Dev Biol 2023; 136:38-48. [PMID: 35595601 PMCID: PMC9976841 DOI: 10.1016/j.semcdb.2022.05.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 04/27/2022] [Accepted: 05/09/2022] [Indexed: 11/22/2022]
Abstract
The ribosomal DNA (rDNA) in Drosophila is found as two additive clusters of individual 35 S cistrons. The multiplicity of rDNA is essential to assure proper translational demands, but the nature of the tandem arrays expose them to copy number variation within and between populations. Here, we discuss means by which a cell responds to insufficient rDNA copy number, including a historical view of rDNA magnification whose mechanism was inferred some 35 years ago. Recent work has revealed that multiple conditions may also result in rDNA loss, in response to which rDNA magnification may have evolved. We discuss potential models for the mechanism of magnification, and evaluate possible consequences of rDNA copy number variation.
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Affiliation(s)
- Selina M Kindelay
- Genetics Graduate Interdisciplinary Program, The University of Arizona, Tucson, AZ 85724, USA
| | - Keith A Maggert
- Genetics Graduate Interdisciplinary Program, The University of Arizona, Tucson, AZ 85724, USA; Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, AZ 85724, USA.
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9
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Arrey G, Keating ST, Regenberg B. A unifying model for extrachromosomal circular DNA load in eukaryotic cells. Semin Cell Dev Biol 2022; 128:40-50. [PMID: 35292190 DOI: 10.1016/j.semcdb.2022.03.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 03/03/2022] [Accepted: 03/03/2022] [Indexed: 02/06/2023]
Abstract
Extrachromosomal circular DNA (eccDNA) with exons and whole genes are common features of eukaryotic cells. Work from especially tumours and the yeast Saccharomyces cerevisiae has revealed that eccDNA can provide large selective advantages and disadvantages. Besides the phenotypic effect due to expression of an eccDNA fragment, eccDNA is different from other mutations in that it is released from 1:1 segregation during cell division. This means that eccDNA can quickly change copy number, pickup secondary mutations and reintegrate into a chromosome to establish substantial genetic variation that could not have evolved via canonical mechanisms. We propose a unifying 5-factor model for conceptualizing the eccDNA load of a eukaryotic cell, emphasizing formation, replication, segregation, selection and elimination. We suggest that the magnitude of these sequential events and their interactions determine the copy number of eccDNA in mitotically dividing cells. We believe that our model will provide a coherent framework for eccDNA research, to understand its biology and the factors that can be manipulated to modulate eccDNA load in eukaryotic cells.
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Affiliation(s)
- Gerard Arrey
- Section for Ecology and Evolution, University of Copenhagen, Copenhagen, Denmark
| | - Samuel T Keating
- Section for Ecology and Evolution, University of Copenhagen, Copenhagen, Denmark
| | - Birgitte Regenberg
- Section for Ecology and Evolution, University of Copenhagen, Copenhagen, Denmark.
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10
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Intragenomic variation in nuclear ribosomal markers and its implication in species delimitation, identification and barcoding in fungi. FUNGAL BIOL REV 2022. [DOI: 10.1016/j.fbr.2022.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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11
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Qi H, Yu L, Li Y, Cai M, He J, Liu J, Hao L, Xu H, Qiao M. Developing Multi-Copy Chromosomal Integration Strategies for Heterologous Biosynthesis of Caffeic Acid in Saccharomyces cerevisiae. Front Microbiol 2022; 13:851706. [PMID: 35300487 PMCID: PMC8923693 DOI: 10.3389/fmicb.2022.851706] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 02/09/2022] [Indexed: 11/13/2022] Open
Abstract
Caffeic acid, a plant-sourced phenolic compound, has a variety of biological activities, such as antioxidant and antimicrobial properties. The caffeic acid biosynthetic pathway was initially constructed in S. cerevisiae, using codon-optimized TAL (coTAL, encoding tyrosine ammonia lyase) from Rhodobacter capsulatus, coC3H (encoding p-coumaric acid 3-hydroxylase) and coCPR1 (encoding cytochrome P450 reductase 1) from Arabidopsis thaliana in 2 μ multi-copy plasmids to produce caffeic acid from glucose. Then, integrated expression of coTAL via delta integration with the POT1 gene (encoding triose phosphate isomerase) as selection marker and episomal expression of coC3H, coCPR1 using the episomal plasmid pLC-c3 were combined, and caffeic acid production was proved to be improved. Next, the delta and rDNA multi-copy integration methods were applied to integrate the genes coC3H and coCPR1 into the chromosome of high p-coumaric acid yielding strain QT3-20. The strain D9 constructed via delta integration outperformed the other strains, leading to 50-fold increased caffeic acid production in optimized rich media compared with the initial construct. The intercomparison between three alternative multi-copy strategies for de novo synthesis of caffeic acid in S. cerevisiae suggested that delta-integration was effective in improving caffeic acid productivity, providing a promising strategy for the production of valuable bio-based chemicals in recombinant S. cerevisiae.
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Affiliation(s)
- Hang Qi
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China
| | - Long Yu
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China
| | - Yuanzi Li
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China.,School of Light Industry, Beijing Technology and Business University, Beijing, China
| | - Miao Cai
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China
| | - Jiaze He
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China
| | - Jiayu Liu
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China
| | - Luyao Hao
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China
| | - Haijin Xu
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China
| | - Mingqiang Qiao
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, China
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12
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Zheng H, Wang K, Xu X, Pan J, Sun X, Hou J, Liu W, Shen Y. Highly efficient
rDNA
‐mediated multicopy integration based on the dynamic balance of rDNA in
Saccharomyces cerevisiae. Microb Biotechnol 2022; 15:1511-1524. [PMID: 35098688 PMCID: PMC9049599 DOI: 10.1111/1751-7915.14010] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 01/16/2022] [Indexed: 11/30/2022] Open
Abstract
Engineered Saccharomyces cerevisiae strains are good cell factories, and developing additional genetic manipulation tools will accelerate construction of metabolically engineered strains. Highly repetitive rDNA sequence is one of two main sites typically used for multicopy integration of genes. Here, we developed a simple and high‐efficiency strategy for rDNA‐mediated multicopy gene integration based on the dynamic balance of rDNA in S. cerevisiae. rDNA copy number was decreased by pre‐treatment with hydroxyurea (HU). Then, heterologous genes were integrated into the rDNA sequence. The copy number of the integrated heterologous genes increased along with restoration of the copy number of rDNA. Our results demonstrated that HU pre‐treatment doubled the number of integrated gene copies; moreover, compared with removing HU stress during transformation, removing HU stress after selection of transformants had a higher probability of resulting in transformants with high‐copy integrated genes. Finally, we integrated 18.0 copies of the xylose isomerase gene into the S. cerevisiae genome in a single step. This novel rDNA‐mediated multicopy genome integration strategy provides a convenient and efficient tool for further metabolic engineering of S. cerevisiae.
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Affiliation(s)
- Huihui Zheng
- State Key Laboratory of Microbial Technology Institute of Microbial Technology Shandong University Qingdao China
| | - Kai Wang
- State Key Laboratory of Microbial Technology Institute of Microbial Technology Shandong University Qingdao China
| | - Xiaoxiao Xu
- State Key Laboratory of Microbial Technology Institute of Microbial Technology Shandong University Qingdao China
| | - Jing Pan
- State Key Laboratory of Microbial Technology Institute of Microbial Technology Shandong University Qingdao China
| | - Xinhua Sun
- State Key Laboratory of Microbial Technology Institute of Microbial Technology Shandong University Qingdao China
| | - Jin Hou
- State Key Laboratory of Microbial Technology Institute of Microbial Technology Shandong University Qingdao China
| | - Weifeng Liu
- State Key Laboratory of Microbial Technology Institute of Microbial Technology Shandong University Qingdao China
| | - Yu Shen
- State Key Laboratory of Microbial Technology Institute of Microbial Technology Shandong University Qingdao China
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13
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Nakajima T, Hosoyamada S, Kobayashi T, Mukai Y. Secreted acid phosphatases maintain replicative lifespan via inositol polyphosphate metabolism in budding yeast. FEBS Lett 2022; 596:189-198. [PMID: 34845723 DOI: 10.1002/1873-3468.14245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 11/03/2021] [Accepted: 11/24/2021] [Indexed: 11/07/2022]
Abstract
Secreted acid phosphatases (APases) dephosphorylate extracellular organic phosphate compounds to supply inorganic phosphate (Pi) to maintain cellular functions. Here, we show that APases are necessary to maintain a normal replicative lifespan in Saccharomyces cerevisiae. Deletion of all four APase genes shortened the lifespan in yeast strains on synthetic media (irrespective of the concentrations of Pi in the media), but it did not affect the intracellular ortho- and polyphosphate levels. Deletion of inositol-pentakisphosphate 2-kinase (IPK1), which encodes inositol-pentakisphosphate 2-kinase, restored the lifespan in APase-null mutants, and IPK1 overexpression shortened the lifespan in wild-type strains. Overexpression of inositol hexakisphosphate (IP6 ) and heptakisphosphate kinases, KCS1 and VIP1, recovered the lifespan in APase-null mutants. Thus, yeast APases modulate the replicative lifespan, probably through dephosphorylation of intracellular IP6 .
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Affiliation(s)
- Toshio Nakajima
- Department of Frontier Bioscience, Nagahama Institute of Bio-Science and Technology, Shiga, Japan
| | - Shun Hosoyamada
- Institute for Quantitative Biosciences, The University of Tokyo, Japan
| | - Takehiko Kobayashi
- Institute for Quantitative Biosciences, The University of Tokyo, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Japan
| | - Yukio Mukai
- Department of Frontier Bioscience, Nagahama Institute of Bio-Science and Technology, Shiga, Japan
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14
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Jernfors T, Danforth J, Kesäniemi J, Lavrinienko A, Tukalenko E, Fajkus J, Dvořáčková M, Mappes T, Watts PC. Expansion of rDNA and pericentromere satellite repeats in the genomes of bank voles Myodes glareolus exposed to environmental radionuclides. Ecol Evol 2021; 11:8754-8767. [PMID: 34257925 PMCID: PMC8258220 DOI: 10.1002/ece3.7684] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 04/27/2021] [Accepted: 05/05/2021] [Indexed: 12/21/2022] Open
Abstract
Altered copy number of certain highly repetitive regions of the genome, such as satellite DNA within heterochromatin and ribosomal RNA loci (rDNA), is hypothesized to help safeguard the genome against damage derived from external stressors. We quantified copy number of the 18S rDNA and a pericentromeric satellite DNA (Msat-160) in bank voles (Myodes glareolus) inhabiting the Chernobyl Exclusion Zone (CEZ), an area that is contaminated by radionuclides and where organisms are exposed to elevated levels of ionizing radiation. We found a significant increase in 18S rDNA and Msat-160 content in the genomes of bank voles from contaminated locations within the CEZ compared with animals from uncontaminated locations. Moreover, 18S rDNA and Msat-160 copy number were positively correlated in the genomes of bank voles from uncontaminated, but not in the genomes of animals inhabiting contaminated, areas. These results show the capacity for local-scale geographic variation in genome architecture and are consistent with the genomic safeguard hypothesis. Disruption of cellular processes related to genomic stability appears to be a hallmark effect in bank voles inhabiting areas contaminated by radionuclides.
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Affiliation(s)
- Toni Jernfors
- Department of Biological and Environmental ScienceUniversity of JyväskyläJyväskyläFinland
| | - John Danforth
- Department of Biochemistry & Molecular BiologyRobson DNA Science CentreArnie Charbonneau Cancer InstituteCumming School of MedicineUniversity of CalgaryCalgaryCanada
| | - Jenni Kesäniemi
- Department of Biological and Environmental ScienceUniversity of JyväskyläJyväskyläFinland
| | - Anton Lavrinienko
- Department of Biological and Environmental ScienceUniversity of JyväskyläJyväskyläFinland
| | - Eugene Tukalenko
- Department of Biological and Environmental ScienceUniversity of JyväskyläJyväskyläFinland
- National Research Center for Radiation Medicine of the National Academy of Medical ScienceKyivUkraine
| | - Jiří Fajkus
- Mendel Centre for Plant Genomics and ProteomicsCentral European Institute of Technology (CEITEC)Masaryk UniversityBrnoCzech Republic
- Laboratory of Functional Genomics and ProteomicsNCBRFaculty of ScienceMasaryk UniversityBrnoCzech Republic
- Department of Cell Biology and RadiobiologyInstitute of Biophysics of the Czech Academy of SciencesBrnoCzech Republic
| | - Martina Dvořáčková
- Mendel Centre for Plant Genomics and ProteomicsCentral European Institute of Technology (CEITEC)Masaryk UniversityBrnoCzech Republic
| | - Tapio Mappes
- Department of Biological and Environmental ScienceUniversity of JyväskyläJyväskyläFinland
| | - Phillip C. Watts
- Department of Biological and Environmental ScienceUniversity of JyväskyläJyväskyläFinland
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15
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Eigenfeld M, Kerpes R, Becker T. Understanding the Impact of Industrial Stress Conditions on Replicative Aging in Saccharomyces cerevisiae. FRONTIERS IN FUNGAL BIOLOGY 2021; 2:665490. [PMID: 37744109 PMCID: PMC10512339 DOI: 10.3389/ffunb.2021.665490] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 03/30/2021] [Indexed: 09/26/2023]
Abstract
In yeast, aging is widely understood as the decline of physiological function and the decreasing ability to adapt to environmental changes. Saccharomyces cerevisiae has become an important model organism for the investigation of these processes. Yeast is used in industrial processes (beer and wine production), and several stress conditions can influence its intracellular aging processes. The aim of this review is to summarize the current knowledge on applied stress conditions, such as osmotic pressure, primary metabolites (e.g., ethanol), low pH, oxidative stress, heat on aging indicators, age-related physiological changes, and yeast longevity. There is clear evidence that yeast cells are exposed to many stressors influencing viability and vitality, leading to an age-related shift in age distribution. Currently, there is a lack of rapid, non-invasive methods allowing the investigation of aspects of yeast aging in real time on a single-cell basis using the high-throughput approach. Methods such as micromanipulation, centrifugal elutriator, or biotinylation do not provide real-time information on age distributions in industrial processes. In contrast, innovative approaches, such as non-invasive fluorescence coupled flow cytometry intended for high-throughput measurements, could be promising for determining the replicative age of yeast cells in fermentation and its impact on industrial stress conditions.
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Affiliation(s)
| | - Roland Kerpes
- Research Group Beverage and Cereal Biotechnology, Institute of Brewing and Beverage Technology, Technical University of Munich, Freising, Germany
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16
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The S-Phase Cyclin Clb5 Promotes rRNA Gene (rDNA) Stability by Maintaining Replication Initiation Efficiency in rDNA. Mol Cell Biol 2021; 41:MCB.00324-20. [PMID: 33619126 PMCID: PMC8088266 DOI: 10.1128/mcb.00324-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Accepted: 02/05/2021] [Indexed: 11/26/2022] Open
Abstract
Regulation of replication origins is important for complete duplication of the genome, but the effect of origin activation on the cellular response to replication stress is poorly understood. The budding yeast rRNA gene (rDNA) forms tandem repeats and undergoes replication fork arrest at the replication fork barrier (RFB), inducing DNA double-strand breaks (DSBs) and genome instability accompanied by copy number alterations. Regulation of replication origins is important for complete duplication of the genome, but the effect of origin activation on the cellular response to replication stress is poorly understood. The budding yeast rRNA gene (rDNA) forms tandem repeats and undergoes replication fork arrest at the replication fork barrier (RFB), inducing DNA double-strand breaks (DSBs) and genome instability accompanied by copy number alterations. Here, we demonstrate that the S-phase cyclin Clb5 promotes rDNA stability. Absence of Clb5 led to reduced efficiency of replication initiation in rDNA but had little effect on the number of replication forks arrested at the RFB, suggesting that arrival of the converging fork is delayed and forks are more stably arrested at the RFB. Deletion of CLB5 affected neither DSB formation nor its repair at the RFB but led to homologous recombination-dependent rDNA instability. Therefore, arrested forks at the RFB may be subject to DSB-independent, recombination-dependent rDNA instability. The rDNA instability in clb5Δ was not completely suppressed by the absence of Fob1, which is responsible for fork arrest at the RFB. Thus, Clb5 establishes the proper interval for active replication origins and shortens the travel distance for DNA polymerases, which may reduce Fob1-independent DNA damage.
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17
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Pérez-Ortín JE, Mena A, Barba-Aliaga M, Singh A, Chávez S, García-Martínez J. Cell volume homeostatically controls the rDNA repeat copy number and rRNA synthesis rate in yeast. PLoS Genet 2021; 17:e1009520. [PMID: 33826644 PMCID: PMC8055003 DOI: 10.1371/journal.pgen.1009520] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 04/19/2021] [Accepted: 03/25/2021] [Indexed: 01/20/2023] Open
Abstract
The adjustment of transcription and translation rates to the changing needs of cells is of utmost importance for their fitness and survival. We have previously shown that the global transcription rate for RNA polymerase II in budding yeast Saccharomyces cerevisiae is regulated in relation to cell volume. Total mRNA concentration is constant with cell volume since global RNApol II-dependent nascent transcription rate (nTR) also keeps constant but mRNA stability increases with cell size. In this paper, we focus on the case of rRNA and RNA polymerase I. Contrarily to that found for RNA pol II, we detected that RNA polymerase I nTR increases proportionally to genome copies and cell size in polyploid cells. In haploid mutant cells with larger cell sizes, the rDNA repeat copy number rises. By combining mathematical modeling and experimental work with the large-size cln3 strain, we observed that the increasing repeat copy number is based on a feedback mechanism in which Sir2 histone deacetylase homeostatically controls the amplification of rDNA repeats in a volume-dependent manner. This amplification is paralleled with an increase in rRNA nTR, which indicates a control of the RNA pol I synthesis rate by cell volume. Synthesis rates of biological macromolecules should be strictly regulated and adjusted to the changing conditions of cells. The change in volume is one of the commonest variables along individual cell life and also when comparing different cell types. We previously found that cells with asymmetric division, such as budding yeasts, use a compensatory change in the global RNA polymerase II synthesis rate and mRNA decay rate to maintain mRNA homeostasis. In the present study, we address the same issue for the RNA polymerase that makes rRNAs, which are essential components of ribosomes and the most abundant RNAs in the cell. We found that the copy number of the gene encoding 35S rRNA, transcribed by RNA polymerase I, changes proportionally to the cell volume in budding yeast via a feedback mechanism based on the Sir2 histone deacetylase, which guarantees that yeast cells have the appropriate RNA polymerase I synthesis rate required for rRNA homeostasis.
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Affiliation(s)
- José E. Pérez-Ortín
- Instituto de Biotecnología y Biomedicina (Biotecmed), Universitat de València, Burjassot, Spain
- * E-mail: (JEP-O); (JG-M)
| | - Adriana Mena
- Instituto de Biotecnología y Biomedicina (Biotecmed), Universitat de València, Burjassot, Spain
| | - Marina Barba-Aliaga
- Instituto de Biotecnología y Biomedicina (Biotecmed), Universitat de València, Burjassot, Spain
| | - Abhyudai Singh
- Department of Electrical and Computer Engineering, University of Delaware, Newark, DE, United States of America
| | - Sebastián Chávez
- Instituto de Biomedicina de Sevilla. Campus Hospital Universitario Virgen del Rocío, Seville, Spain
| | - José García-Martínez
- Instituto de Biotecnología y Biomedicina (Biotecmed), Universitat de València, Burjassot, Spain
- * E-mail: (JEP-O); (JG-M)
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18
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Goffová I, Fajkus J. The rDNA Loci-Intersections of Replication, Transcription, and Repair Pathways. Int J Mol Sci 2021; 22:1302. [PMID: 33525595 PMCID: PMC7865372 DOI: 10.3390/ijms22031302] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 01/25/2021] [Accepted: 01/25/2021] [Indexed: 12/28/2022] Open
Abstract
Genes encoding ribosomal RNA (rDNA) are essential for cell survival and are particularly sensitive to factors leading to genomic instability. Their repetitive character makes them prone to inappropriate recombinational events arising from collision of transcriptional and replication machineries, resulting in unstable rDNA copy numbers. In this review, we summarize current knowledge on the structure and organization of rDNA, its role in sensing changes in the genome, and its linkage to aging. We also review recent findings on the main factors involved in chromatin assembly and DNA repair in the maintenance of rDNA stability in the model plants Arabidopsis thaliana and the moss Physcomitrella patens, providing a view across the plant evolutionary tree.
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Affiliation(s)
- Ivana Goffová
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, CZ-61137 Brno, Czech Republic;
- Chromatin Molecular Complexes, Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, CZ-62500 Brno, Czech Republic
| | - Jiří Fajkus
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, CZ-61137 Brno, Czech Republic;
- Chromatin Molecular Complexes, Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, CZ-62500 Brno, Czech Republic
- Department of Cell Biology and Radiobiology, Institute of Biophysics of the Czech Academy of Sciences, CZ-61265 Brno, Czech Republic
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19
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Lee JW, Ong EBB. Genomic Instability and Cellular Senescence: Lessons From the Budding Yeast. Front Cell Dev Biol 2021; 8:619126. [PMID: 33511130 PMCID: PMC7835410 DOI: 10.3389/fcell.2020.619126] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 12/15/2020] [Indexed: 01/14/2023] Open
Abstract
Aging is a complex biological process that occurs in all living organisms. Aging is initiated by the gradual accumulation of biomolecular damage in cells leading to the loss of cellular function and ultimately death. Cellular senescence is one such pathway that leads to aging. The accumulation of nucleic acid damage and genetic alterations that activate permanent cell-cycle arrest triggers the process of senescence. Cellular senescence can result from telomere erosion and ribosomal DNA instability. In this review, we summarize the molecular mechanisms of telomere length homeostasis and ribosomal DNA stability, and describe how these mechanisms are linked to cellular senescence and longevity through lessons learned from budding yeast.
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Affiliation(s)
- Jee Whu Lee
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Penang, Malaysia.,USM-RIKEN International Centre for Aging Science (URICAS), Universiti Sains Malaysia, Penang, Malaysia
| | - Eugene Boon Beng Ong
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Penang, Malaysia.,USM-RIKEN International Centre for Aging Science (URICAS), Universiti Sains Malaysia, Penang, Malaysia
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20
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Shi S, Luo H, Wang L, Li H, Liang Y, Xia J, Wang Z, Cheng B, Huang L, Liao G, Xu B. Combined inhibition of RNA polymerase I and mTORC1/2 synergize to combat oral squamous cell carcinoma. Biomed Pharmacother 2021; 133:110906. [PMID: 33190037 DOI: 10.1016/j.biopha.2020.110906] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Revised: 10/13/2020] [Accepted: 10/16/2020] [Indexed: 01/27/2023] Open
Abstract
Oral squamous cell carcinoma (OSCC) is the major cause of morbidity and mortality in head and neck cancer patients worldwide. This malignant disease is challenging to treat because of the lack of effective curative strategies and the high incidence of recurrence. This study aimed to investigate the efficacy of a single and dual approach targeting ribosome biogenesis and protein translation to treat OSCC associated with the copy number variation (CNV) of ribosomal DNA (rDNA). Here, we found that primary OSCC tumors frequently exhibited a partial loss of 45S rDNA copy number and demonstrated a high susceptibility to CX5461 (a selective inhibitor of RNA polymerase I) and the coadministration of CX5461 and INK128 (a potent inhibitor of mTORC1/2). Combined treatment displayed the promising synergistic effects that induced cell apoptosis and reactive oxygen species (ROS) generation, and inhibited cell growth and proliferation. Moreover, INK128 compromised NHEJ-DNA repair pathway to reinforce the antitumor activity of CX5461. In vivo, the cotreatment synergistically suppressed tumor growth, triggered apoptosis and strikingly extended the survival time of tumor-bearing mice. Additionally, treatment with the individual compounds and coadministration appeared to reduce the incidence of enlarged inguinal lymph nodes. Our study supports that the combination of CX5461 and INK128 is a novel and efficacious therapeutic strategy that can combat this cancer and that 45S rDNA may serve as a useful indicator to predict the efficacy of this cotreatment.
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Affiliation(s)
- Shanwei Shi
- Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Institute of Stomatological Research, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Huigen Luo
- Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Institute of Stomatological Research, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Lihong Wang
- Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Institute of Stomatological Research, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Hua Li
- The Stowers Institute for Medical Research, Kansas City, Missouri, United States
| | - Yujie Liang
- Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Institute of Stomatological Research, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Juan Xia
- Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Institute of Stomatological Research, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Zhi Wang
- Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Institute of Stomatological Research, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Bin Cheng
- Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Institute of Stomatological Research, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Linfeng Huang
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Guiqing Liao
- Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Institute of Stomatological Research, Sun Yat-sen University, Guangzhou, Guangdong Province, China.
| | - Baoshan Xu
- Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Institute of Stomatological Research, Sun Yat-sen University, Guangzhou, Guangdong Province, China.
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21
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Malcı K, Walls LE, Rios-Solis L. Multiplex Genome Engineering Methods for Yeast Cell Factory Development. Front Bioeng Biotechnol 2020; 8:589468. [PMID: 33195154 PMCID: PMC7658401 DOI: 10.3389/fbioe.2020.589468] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 10/07/2020] [Indexed: 12/12/2022] Open
Abstract
As biotechnological applications of synthetic biology tools including multiplex genome engineering are expanding rapidly, the construction of strategically designed yeast cell factories becomes increasingly possible. This is largely due to recent advancements in genome editing methods like CRISPR/Cas tech and high-throughput omics tools. The model organism, baker's yeast (Saccharomyces cerevisiae) is an important synthetic biology chassis for high-value metabolite production. Multiplex genome engineering approaches can expedite the construction and fine tuning of effective heterologous pathways in yeast cell factories. Numerous multiplex genome editing techniques have emerged to capitalize on this recently. This review focuses on recent advancements in such tools, such as delta integration and rDNA cluster integration coupled with CRISPR-Cas tools to greatly enhance multi-integration efficiency. Examples of pre-placed gate systems which are an innovative alternative approach for multi-copy gene integration were also reviewed. In addition to multiple integration studies, multiplexing of alternative genome editing methods are also discussed. Finally, multiplex genome editing studies involving non-conventional yeasts and the importance of automation for efficient cell factory design and construction are considered. Coupling the CRISPR/Cas system with traditional yeast multiplex genome integration or donor DNA delivery methods expedites strain development through increased efficiency and accuracy. Novel approaches such as pre-placing synthetic sequences in the genome along with improved bioinformatics tools and automation technologies have the potential to further streamline the strain development process. In addition, the techniques discussed to engineer S. cerevisiae, can be adapted for use in other industrially important yeast species for cell factory development.
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Affiliation(s)
- Koray Malcı
- Institute for Bioengineering, School of Engineering, The University of Edinburgh, Edinburgh, United Kingdom.,Centre for Synthetic and Systems Biology (SynthSys), The University of Edinburgh, Edinburgh, United Kingdom
| | - Laura E Walls
- Institute for Bioengineering, School of Engineering, The University of Edinburgh, Edinburgh, United Kingdom.,Centre for Synthetic and Systems Biology (SynthSys), The University of Edinburgh, Edinburgh, United Kingdom
| | - Leonardo Rios-Solis
- Institute for Bioengineering, School of Engineering, The University of Edinburgh, Edinburgh, United Kingdom.,Centre for Synthetic and Systems Biology (SynthSys), The University of Edinburgh, Edinburgh, United Kingdom
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22
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Age-Dependent Ribosomal DNA Variations in Mice. Mol Cell Biol 2020; 40:MCB.00368-20. [PMID: 32900821 PMCID: PMC7588874 DOI: 10.1128/mcb.00368-20] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 09/02/2020] [Indexed: 12/22/2022] Open
Abstract
The rRNA gene, which consists of tandem repetitive arrays (ribosomal DNA [rDNA] repeat), is one of the most unstable regions in the genome. The rDNA repeat in the budding yeast Saccharomyces cerevisiae is known to become unstable as the cell ages. However, it is unclear how the rDNA repeat changes in aging mammalian cells. Using quantitative single-cell analyses, we identified age-dependent alterations in rDNA copy number and levels of methylation in mice. The degree of methylation and copy number of rDNA from bone marrow cells of 2-year-old mice were increased by comparison to levels in 4-week-old mice in two mouse strains, BALB/cA and C57BL/6. The rRNA gene, which consists of tandem repetitive arrays (ribosomal DNA [rDNA] repeat), is one of the most unstable regions in the genome. The rDNA repeat in the budding yeast Saccharomyces cerevisiae is known to become unstable as the cell ages. However, it is unclear how the rDNA repeat changes in aging mammalian cells. Using quantitative single-cell analyses, we identified age-dependent alterations in rDNA copy number and levels of methylation in mice. The degree of methylation and copy number of rDNA from bone marrow cells of 2-year-old mice were increased by comparison to levels in 4-week-old mice in two mouse strains, BALB/cA and C57BL/6. Moreover, the level of pre-rRNA transcripts was reduced in older BALB/cA mice. We also identified many sequence variations in the rDNA. Among them, three mutations were unique to old mice, and two of them were found in the conserved region in budding yeast. We established yeast strains with the old-mouse-specific mutations and found that they shortened the life span of the cells. Our findings suggest that rDNA is also fragile in mammalian cells and that alterations within this region have a profound effect on cellular function.
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23
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Balzano E, Pelliccia F, Giunta S. Genome (in)stability at tandem repeats. Semin Cell Dev Biol 2020; 113:97-112. [PMID: 33109442 DOI: 10.1016/j.semcdb.2020.10.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 09/26/2020] [Accepted: 10/10/2020] [Indexed: 12/12/2022]
Abstract
Repeat sequences account for over half of the human genome and represent a significant source of variation that underlies physiological and pathological states. Yet, their study has been hindered due to limitations in short-reads sequencing technology and difficulties in assembly. A important category of repetitive DNA in the human genome is comprised of tandem repeats (TRs), where repetitive units are arranged in a head-to-tail pattern. Compared to other regions of the genome, TRs carry between 10 and 10,000 fold higher mutation rate. There are several mutagenic mechanisms that can give rise to this propensity toward instability, but their precise contribution remains speculative. Given the high degree of homology between these sequences and their arrangement in tandem, once damaged, TRs have an intrinsic propensity to undergo aberrant recombination with non-allelic exchange and generate harmful rearrangements that may undermine the stability of the entire genome. The dynamic mutagenesis at TRs has been found to underlie individual polymorphism associated with neurodegenerative and neuromuscular disorders, as well as complex genetic diseases like cancer and diabetes. Here, we review our current understanding of the surveillance and repair mechanisms operating within these regions, and we describe how alterations in these protective processes can readily trigger mutational signatures found at TRs, ultimately resulting in the pathological correlation between TRs instability and human diseases. Finally, we provide a viewpoint to counter the detrimental effects that TRs pose in light of their selection and conservation, as important drivers of human evolution.
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Affiliation(s)
- Elisa Balzano
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, 00185 Roma, Italy
| | - Franca Pelliccia
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, 00185 Roma, Italy
| | - Simona Giunta
- The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA; Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, 00185 Roma, Italy.
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24
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Does Intraspecific Variation in rDNA Copy Number Affect Analysis of Microbial Communities? Trends Microbiol 2020; 29:19-27. [PMID: 32593503 DOI: 10.1016/j.tim.2020.05.019] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 05/23/2020] [Accepted: 05/28/2020] [Indexed: 01/01/2023]
Abstract
Amplicon sequencing of partial regions of the ribosomal RNA loci (rDNA) is widely used to profile microbial communities. However, the rDNA is dynamic and can exhibit substantial interspecific and intraspecific variation in copy number in prokaryotes and, especially, in microbial eukaryotes. As change in rDNA copy number is a common response to environmental change, rDNA copy number is not necessarily a property of a species. Variation in rDNA copy number, especially the capacity for large intraspecific changes driven by external cues, complicates analyses of rDNA amplicon sequence data. We highlight the need to (i) interpret amplicon sequence data in light of possible interspecific and intraspecific variation, and (ii) examine the potential plasticity in rDNA copy number as an important ecological factor to better understand how microbial communities are structured in heterogeneous environments.
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25
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Shen D, Skibbens RV. Promotion of Hyperthermic-Induced rDNA Hypercondensation in Saccharomyces cerevisiae. Genetics 2020; 214:589-604. [PMID: 31980450 PMCID: PMC7054013 DOI: 10.1534/genetics.119.302994] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 12/29/2019] [Indexed: 12/11/2022] Open
Abstract
Ribosome biogenesis is tightly regulated through stress-sensing pathways that impact genome stability, aging and senescence. In Saccharomyces cerevisiae, ribosomal RNAs are transcribed from rDNA located on the right arm of chromosome XII. Numerous studies reveal that rDNA decondenses into a puff-like structure during interphase, and condenses into a tight loop-like structure during mitosis. Intriguingly, a novel and additional mechanism of increased mitotic rDNA compaction (termed hypercondensation) was recently discovered that occurs in response to temperature stress (hyperthermic-induced) and is rapidly reversible. Here, we report that neither changes in condensin binding or release of DNA during mitosis, nor mutation of factors that regulate cohesin binding and release, appear to play a critical role in hyperthermic-induced rDNA hypercondensation. A candidate genetic approach revealed that deletion of either HSP82 or HSC82 (Hsp90 encoding heat shock paralogs) result in significantly reduced hyperthermic-induced rDNA hypercondensation. Intriguingly, Hsp inhibitors do not impact rDNA hypercondensation. In combination, these findings suggest that Hsp90 either stabilizes client proteins, which are sensitive to very transient thermic challenges, or directly promotes rDNA hypercondensation during preanaphase. Our findings further reveal that the high mobility group protein Hmo1 is a negative regulator of mitotic rDNA condensation, distinct from its role in promoting premature condensation of rDNA during interphase upon nutrient starvation.
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Affiliation(s)
- Donglai Shen
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015
| | - Robert V Skibbens
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015
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26
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The CCR4-NOT Complex Maintains Stability and Transcription of rRNA Genes by Repressing Antisense Transcripts. Mol Cell Biol 2019; 40:MCB.00320-19. [PMID: 31611247 PMCID: PMC6908257 DOI: 10.1128/mcb.00320-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 09/26/2019] [Indexed: 12/21/2022] Open
Abstract
The rRNA genes (rDNA) in eukaryotes are organized into highly repetitive gene clusters. Each organism maintains a particular number of copies, suggesting that the rDNA is actively stabilized. We previously identified about 700 Saccharomyces cerevisiae genes that could contribute to rDNA maintenance. Here, we further analyzed these deletion mutants with unstable rDNA by measuring the amounts of extrachromosomal rDNA circles (ERCs) that are released as by-products of intrachromosomal recombination. The rRNA genes (rDNA) in eukaryotes are organized into highly repetitive gene clusters. Each organism maintains a particular number of copies, suggesting that the rDNA is actively stabilized. We previously identified about 700 Saccharomyces cerevisiae genes that could contribute to rDNA maintenance. Here, we further analyzed these deletion mutants with unstable rDNA by measuring the amounts of extrachromosomal rDNA circles (ERCs) that are released as by-products of intrachromosomal recombination. We found that extremely high levels of ERCs were formed in the absence of Pop2 (Caf1), which is a subunit of the CCR4-NOT complex, important for the regulation of all stages of gene expression. In the pop2 mutant, transcripts from the noncoding promoter E-pro in the rDNA accumulated, and the amounts of cohesin and condensin were reduced, which could promote recombination events. Moreover, we discovered that the amount of rRNA was decreased in the pop2 mutant. Similar phenotypes were observed in the absence of subunits Ccr4 and Not4 that, like Pop2, convey enzymatic activity to the complex. These findings indicate that lack of any CCR4-NOT-associated enzymatic activity resulted in a severe unstable rDNA phenotype related to the accumulation of noncoding RNA from E-pro.
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Crane MM, Russell AE, Schafer BJ, Blue BW, Whalen R, Almazan J, Hong MG, Nguyen B, Goings JE, Chen KL, Kelly R, Kaeberlein M. DNA damage checkpoint activation impairs chromatin homeostasis and promotes mitotic catastrophe during aging. eLife 2019; 8:e50778. [PMID: 31714209 PMCID: PMC6850777 DOI: 10.7554/elife.50778] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 10/30/2019] [Indexed: 02/01/2023] Open
Abstract
Genome instability is a hallmark of aging and contributes to age-related disorders such as cancer and Alzheimer's disease. The accumulation of DNA damage during aging has been linked to altered cell cycle dynamics and the failure of cell cycle checkpoints. Here, we use single cell imaging to study the consequences of increased genomic instability during aging in budding yeast and identify striking age-associated genome missegregation events. This breakdown in mitotic fidelity results from the age-related activation of the DNA damage checkpoint and the resulting degradation of histone proteins. Disrupting the ability of cells to degrade histones in response to DNA damage increases replicative lifespan and reduces genomic missegregations. We present several lines of evidence supporting a model of antagonistic pleiotropy in the DNA damage response where histone degradation, and limited histone transcription are beneficial to respond rapidly to damage but reduce lifespan and genomic stability in the long term.
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Affiliation(s)
- Matthew M Crane
- Department of PathologyUniversity of WashingtonSeattleUnited States
| | - Adam E Russell
- Department of PathologyUniversity of WashingtonSeattleUnited States
| | - Brent J Schafer
- Department of PathologyUniversity of WashingtonSeattleUnited States
| | - Ben W Blue
- Department of PathologyUniversity of WashingtonSeattleUnited States
| | - Riley Whalen
- Department of PathologyUniversity of WashingtonSeattleUnited States
| | - Jared Almazan
- Department of PathologyUniversity of WashingtonSeattleUnited States
| | - Mung Gi Hong
- Department of PathologyUniversity of WashingtonSeattleUnited States
| | - Bao Nguyen
- Department of PathologyUniversity of WashingtonSeattleUnited States
| | - Joslyn E Goings
- Department of PathologyUniversity of WashingtonSeattleUnited States
| | - Kenneth L Chen
- Department of PathologyUniversity of WashingtonSeattleUnited States
- Department of Genome SciencesUniversity of WashingtonSeattleUnited States
- Medical Scientist Training ProgramUniversity of WashingtonSeattleUnited States
| | - Ryan Kelly
- Department of PathologyUniversity of WashingtonSeattleUnited States
| | - Matt Kaeberlein
- Department of PathologyUniversity of WashingtonSeattleUnited States
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28
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Wakatsuki T, Sasaki M, Kobayashi T. Defects in the NuA4 acetyltransferase complex increase stability of the ribosomal RNA gene and extend replicative lifespan. Genes Genet Syst 2019; 94:197-206. [PMID: 31694990 DOI: 10.1266/ggs.19-00022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Genome instability is a cause of cellular senescence. The ribosomal RNA gene repeat (rDNA) is one of the most unstable regions in the genome and its instability is proposed to be a major inducer of cellular senescence and restricted lifespan. We previously conducted a genome-wide screen using a budding yeast deletion library to identify mutants that exhibit a change in the stability of the rDNA region, compared to the wild-type. To investigate the correlation between rDNA stability and lifespan, we examined deletion mutants with very stable rDNA and found that deletion of EAF3, encoding a component of the NuA4 histone acetyltransferase complex, reproducibly resulted in increased stabilization of the rDNA. In the absence of Eaf3, and of other subunits of the NuA4 complex, we observed lower levels of extrachromosomal rDNA circles that are produced by recombination in the rDNA and are thus an indicator of rDNA instability. The replicative lifespan in the eaf3 mutant was extended by ~30%, compared to the wild-type strain. Our findings provide evidence that rDNA stability is correlated with extended replicative lifespan. The eaf3 mutation possibly affects the non-coding transcription in rDNA that regulates rDNA recombination through cohesin dissociation.
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Affiliation(s)
- Tsuyoshi Wakatsuki
- Institute for Quantitative Biosciences, The University of Tokyo.,Department of Life Science and Technology, Tokyo Institute of Technology
| | - Mariko Sasaki
- Institute for Quantitative Biosciences, The University of Tokyo
| | - Takehiko Kobayashi
- Institute for Quantitative Biosciences, The University of Tokyo.,Department of Life Science and Technology, Tokyo Institute of Technology.,Collaborative Research Institute for Innovative Microbiology, The University of Tokyo
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29
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Matos-Perdomo E, Machín F. Nucleolar and Ribosomal DNA Structure under Stress: Yeast Lessons for Aging and Cancer. Cells 2019; 8:cells8080779. [PMID: 31357498 PMCID: PMC6721496 DOI: 10.3390/cells8080779] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 07/15/2019] [Accepted: 07/24/2019] [Indexed: 02/06/2023] Open
Abstract
Once thought a mere ribosome factory, the nucleolus has been viewed in recent years as an extremely sensitive gauge of diverse cellular stresses. Emerging concepts in nucleolar biology include the nucleolar stress response (NSR), whereby a series of cell insults have a special impact on the nucleolus. These insults include, among others, ultra-violet radiation (UV), nutrient deprivation, hypoxia and thermal stress. While these stresses might influence nucleolar biology directly or indirectly, other perturbances whose origin resides in the nucleolar biology also trigger nucleolar and systemic stress responses. Among the latter, we find mutations in nucleolar and ribosomal proteins, ribosomal RNA (rRNA) processing inhibitors and ribosomal DNA (rDNA) transcription inhibition. The p53 protein also mediates NSR, leading ultimately to cell cycle arrest, apoptosis, senescence or differentiation. Hence, NSR is gaining importance in cancer biology. The nucleolar size and ribosome biogenesis, and how they connect with the Target of Rapamycin (TOR) signalling pathway, are also becoming important in the biology of aging and cancer. Simple model organisms like the budding yeast Saccharomyces cerevisiae, easy to manipulate genetically, are useful in order to study nucleolar and rDNA structure and their relationship with stress. In this review, we summarize the most important findings related to this topic.
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Affiliation(s)
- Emiliano Matos-Perdomo
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
- Escuela de Doctorado y Estudios de Postgrado, Universidad de La Laguna, 38200 Tenerife, Spain
| | - Félix Machín
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain.
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, 38200 Tenerife, Spain.
- Facultad de Ciencias de la Salud, Universidad Fernando Pessoa Canarias, 35450 Santa María de Guía, Gran Canaria, Spain.
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30
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Symonová R. Integrative rDNAomics-Importance of the Oldest Repetitive Fraction of the Eukaryote Genome. Genes (Basel) 2019; 10:genes10050345. [PMID: 31067804 PMCID: PMC6562748 DOI: 10.3390/genes10050345] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Revised: 04/17/2019] [Accepted: 04/25/2019] [Indexed: 02/06/2023] Open
Abstract
Nuclear ribosomal RNA (rRNA) genes represent the oldest repetitive fraction universal to all eukaryotic genomes. Their deeply anchored universality and omnipresence during eukaryotic evolution reflects in multiple roles and functions reaching far beyond ribosomal synthesis. Merely the copy number of non-transcribed rRNA genes is involved in mechanisms governing e.g., maintenance of genome integrity and control of cellular aging. Their copy number can vary in response to environmental cues, in cellular stress sensing, in development of cancer and other diseases. While reaching hundreds of copies in humans, there are records of up to 20,000 copies in fish and frogs and even 400,000 copies in ciliates forming thus a literal subgenome or an rDNAome within the genome. From the compositional and evolutionary dynamics viewpoint, the precursor 45S rDNA represents universally GC-enriched, highly recombining and homogenized regions. Hence, it is not accidental that both rDNA sequence and the corresponding rRNA secondary structure belong to established phylogenetic markers broadly used to infer phylogeny on multiple taxonomical levels including species delimitation. However, these multiple roles of rDNAs have been treated and discussed as being separate and independent from each other. Here, I aim to address nuclear rDNAs in an integrative approach to better assess the complexity of rDNA importance in the evolutionary context.
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Affiliation(s)
- Radka Symonová
- Faculty of Science, Department of Biology, University of Hradec Králové, 500 03 Hradec Králové, Czech Republic.
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31
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Ribosomal RNA gene repeats associate with the nuclear pore complex for maintenance after DNA damage. PLoS Genet 2019; 15:e1008103. [PMID: 30998688 PMCID: PMC6490929 DOI: 10.1371/journal.pgen.1008103] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 04/30/2019] [Accepted: 03/20/2019] [Indexed: 12/04/2022] Open
Abstract
The ribosomal RNA genes (rDNA) comprise a highly repetitive gene cluster. The copy number of genes at this locus can readily change and is therefore one of the most unstable regions of the genome. DNA damage in rDNA occurs after binding of the replication fork blocking protein Fob1 in S phase, which triggers unequal sister chromatid recombination. However, the precise mechanisms by which such DNA double-strand breaks (DSBs) are repaired is not well understood. Here, we demonstrate that the conserved protein kinase Tel1 maintains rDNA stability after replication fork arrest. We show that rDNA associates with nuclear pores, which is dependent on DNA damage checkpoint kinases Mec1/Tel1 and replisome component Tof1. These findings suggest that rDNA-nuclear pore association is due to a replication fork block and subsequent DSB. Indeed, quantitative microscopy revealed that rDNA is relocated to the nuclear periphery upon induction of a DSB. Finally, rDNA stability was reduced in strains where this association with the nuclear envelope was prevented, which suggests its importance for avoiding improper recombination repair that could induce repeat instability. Ribosomal RNA genes (rDNA) comprise an unstable region of the genome due to their highly repetitive structure and elevated levels of transcription. Collision between transcription and replication machineries of rDNA, which may lead to DNA damage in the form of a double-stranded break, is avoided by the replication fork barrier. When such a break is repaired by homologous recombination with a repeat on the sister chromatid, the abundance of homologous sequences may lead to a change in copy number. In most organisms, however, only small variations in copy number are observed, indicating that the rDNA is stably maintained. Our results suggest that some parts of rDNA become localized to the nuclear pore complex in a DNA double-strand break-dependent manner. This localization requires the protein kinase Tel1, which is involved in the DNA damage response pathway, and factors that recruit condensin, which facilitates condensation and segregation of rDNA during mitosis. We found that the rDNA becomes unstable when association with the nuclear envelope was prevented. Thus, the localization represents a unique strategy for maintaining repeat integrity after DNA damage.
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Cytogenetic instability of chromosomal nucleolar organizer regions (NORs) in cloned mouse L929 fibroblasts. Chromosome Res 2019; 27:95-108. [PMID: 30604344 DOI: 10.1007/s10577-018-9598-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 12/05/2018] [Accepted: 12/07/2018] [Indexed: 12/23/2022]
Abstract
Ribosomal DNA (rDNA) gene codes for 18S, 5.8S, and 28S rRNA form tandem repetitive clusters, which occupy distinct chromosomal loci called nucleolar organizer regions (NORs). The number and position of NORs on chromosomes are genetic characteristics of the species although within a cell, the NOR sizes can significantly vary due to loss or multiplication of rDNA copies. In the current study, we used mouse L929 fibroblasts, the aneuploid cells which differ in the FISH- and Ag-NOR numbers, to examine whether the parental NOR variability is inherited in clones. By statistical analysis, we showed that the cloned fibroblasts were able to restore the NOR numerical characteristics of the parental cells after long-term culturing. These results support the idea that mammalian cells may have mechanisms which control the number and activity of NORs at the population level. In L929 fibroblasts, we also regularly observed laterally asymmetry of FISH-NORs that evidenced in an unequal distribution of the mother rDNA copies between the daughter cells in mitosis.
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33
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Mena A, Medina DA, García-Martínez J, Begley V, Singh A, Chávez S, Muñoz-Centeno MC, Pérez-Ortín JE. Asymmetric cell division requires specific mechanisms for adjusting global transcription. Nucleic Acids Res 2017; 45:12401-12412. [PMID: 29069448 PMCID: PMC5716168 DOI: 10.1093/nar/gkx974] [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: 08/29/2017] [Accepted: 10/10/2017] [Indexed: 12/19/2022] Open
Abstract
Most cells divide symmetrically into two approximately identical cells. There are many examples, however, of asymmetric cell division that can generate sibling cell size differences. Whereas physical asymmetric division mechanisms and cell fate consequences have been investigated, the specific problem caused by asymmetric division at the transcription level has not yet been addressed. In symmetrically dividing cells the nascent transcription rate increases in parallel to cell volume to compensate it by keeping the actual mRNA synthesis rate constant. This cannot apply to the yeast Saccharomyces cerevisiae, where this mechanism would provoke a never-ending increasing mRNA synthesis rate in smaller daughter cells. We show here that, contrarily to other eukaryotes with symmetric division, budding yeast keeps the nascent transcription rates of its RNA polymerases constant and increases mRNA stability. This control on RNA pol II-dependent transcription rate is obtained by controlling the cellular concentration of this enzyme.
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Affiliation(s)
- Adriana Mena
- Departamento de Bioquímica y Biología Molecular and E.R.I. Biotecmed, Universitat de València, Dr. Moliner, 50, Burjassot 46100, Valencia, Spain
| | - Daniel A Medina
- Departamento de Bioquímica y Biología Molecular and E.R.I. Biotecmed, Universitat de València, Dr. Moliner, 50, Burjassot 46100, Valencia, Spain
| | - José García-Martínez
- Departamento de Genética and E.R.I. Biotecmed, Universitat de València, Dr. Moliner, 50, Burjassot 46100, Valencia, Spain
| | - Victoria Begley
- Departamento de Genética, Universidad de Sevilla and Instituto de Biomedicina de Sevilla (IBiS), Hospital Virgen del Rocío-CSIC-Universidad de Sevilla, 41013 Sevilla, Spain
| | - Abhyudai Singh
- Department of Electrical and Computer Engineering, University of Delaware, Newark, DE 19716, USA
| | - Sebastián Chávez
- Departamento de Genética, Universidad de Sevilla and Instituto de Biomedicina de Sevilla (IBiS), Hospital Virgen del Rocío-CSIC-Universidad de Sevilla, 41013 Sevilla, Spain
| | - Mari C Muñoz-Centeno
- Departamento de Genética, Universidad de Sevilla and Instituto de Biomedicina de Sevilla (IBiS), Hospital Virgen del Rocío-CSIC-Universidad de Sevilla, 41013 Sevilla, Spain
| | - José E Pérez-Ortín
- Departamento de Bioquímica y Biología Molecular and E.R.I. Biotecmed, Universitat de València, Dr. Moliner, 50, Burjassot 46100, Valencia, Spain
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34
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Hult C, Adalsteinsson D, Vasquez PA, Lawrimore J, Bennett M, York A, Cook D, Yeh E, Forest MG, Bloom K. Enrichment of dynamic chromosomal crosslinks drive phase separation of the nucleolus. Nucleic Acids Res 2017; 45:11159-11173. [PMID: 28977453 PMCID: PMC5737219 DOI: 10.1093/nar/gkx741] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2017] [Revised: 08/07/2017] [Accepted: 08/14/2017] [Indexed: 01/24/2023] Open
Abstract
Regions of highly repetitive DNA, such as those found in the nucleolus, show a self-organization that is marked by spatial segregation and frequent self-interaction. The mechanisms that underlie the sequestration of these sub-domains are largely unknown. Using a stochastic, bead-spring representation of chromatin in budding yeast, we find enrichment of protein-mediated, dynamic chromosomal cross-links recapitulates the segregation, morphology and self-interaction of the nucleolus. Rates and enrichment of dynamic crosslinking have profound consequences on domain morphology. Our model demonstrates the nucleolus is phase separated from other chromatin in the nucleus and predicts that multiple rDNA loci will form a single nucleolus independent of their location within the genome. Fluorescent labeling of budding yeast nucleoli with CDC14-GFP revealed that a split rDNA locus indeed forms a single nucleolus. We propose that nuclear sub-domains, such as the nucleolus, result from phase separations within the nucleus, which are driven by the enrichment of protein-mediated, dynamic chromosomal crosslinks.
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Affiliation(s)
- Caitlin Hult
- Department of Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - David Adalsteinsson
- Department of Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Paula A. Vasquez
- Department of Mathematics, University of South Carolina, Columbia, SC 29808, USA
| | - Josh Lawrimore
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Curriculum of Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Maggie Bennett
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Alyssa York
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Diana Cook
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Elaine Yeh
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Mark Gregory Forest
- Department of Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kerry Bloom
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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35
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Sasaki M, Kobayashi T. Ctf4 Prevents Genome Rearrangements by Suppressing DNA Double-Strand Break Formation and Its End Resection at Arrested Replication Forks. Mol Cell 2017; 66:533-545.e5. [PMID: 28525744 DOI: 10.1016/j.molcel.2017.04.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 03/20/2017] [Accepted: 04/26/2017] [Indexed: 12/19/2022]
Abstract
Arrested replication forks lead to DNA double-strand breaks (DSBs), which are a major source of genome rearrangements. Yet DSB repair in the context of broken forks remains poorly understood. Here we demonstrate that DSBs that are formed at arrested forks in the budding yeast ribosomal RNA gene (rDNA) locus are normally repaired by pathways dependent on the Mre11-Rad50-Xrs2 complex but independent of HR. HR is also dispensable for DSB repair at stalled forks at tRNA genes. In contrast, in cells lacking the core replisome component Ctf4, DSBs are formed more frequently, and these DSBs undergo end resection and HR-mediated repair that is prone to rDNA hyper-amplification; this highlights Ctf4 as a key regulator of DSB end resection at arrested forks. End resection also occurs during physiological rDNA amplification even in the presence of Ctf4. Suppression of end resection is thus important for protecting DSBs at arrested forks from chromosome rearrangements.
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MESH Headings
- DNA Breaks, Double-Stranded
- DNA Repair
- DNA Replication
- DNA, Fungal/biosynthesis
- DNA, Fungal/chemistry
- DNA, Fungal/genetics
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Endodeoxyribonucleases/genetics
- Endodeoxyribonucleases/metabolism
- Exodeoxyribonucleases/genetics
- Exodeoxyribonucleases/metabolism
- Gene Rearrangement
- Microbial Viability
- Mutation
- Nucleic Acid Conformation
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- Replication Origin
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Saccharomyces cerevisiae Proteins/genetics
- Saccharomyces cerevisiae Proteins/metabolism
- Time Factors
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Affiliation(s)
- Mariko Sasaki
- Laboratory of Genome Regeneration, Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Takehiko Kobayashi
- Laboratory of Genome Regeneration, Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
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