1
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Kojima ML, Hoppe C, Giraldez AJ. The maternal-to-zygotic transition: reprogramming of the cytoplasm and nucleus. Nat Rev Genet 2025; 26:245-267. [PMID: 39587307 PMCID: PMC11928286 DOI: 10.1038/s41576-024-00792-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2024] [Indexed: 11/27/2024]
Abstract
A fertilized egg is initially transcriptionally silent and relies on maternally provided factors to initiate development. For embryonic development to proceed, the oocyte-inherited cytoplasm and the nuclear chromatin need to be reprogrammed to create a permissive environment for zygotic genome activation (ZGA). During this maternal-to-zygotic transition (MZT), which is conserved in metazoans, transient totipotency is induced and zygotic transcription is initiated to form the blueprint for future development. Recent technological advances have enhanced our understanding of MZT regulation, revealing common themes across species and leading to new fundamental insights about transcription, mRNA decay and translation.
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Affiliation(s)
- Mina L Kojima
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA
| | - Caroline Hoppe
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA
| | - Antonio J Giraldez
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA.
- Yale Stem Cell Center, Yale University School of Medicine, New Haven, CT, USA.
- Yale Cancer Center, Yale University School of Medicine, New Haven, CT, USA.
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2
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Göder A, Maric CA, Rainey MD, O’Connor A, Cazzaniga C, Shamavu D, Cadoret JC, Santocanale C. DBF4, not DRF1, is the crucial regulator of CDC7 kinase at replication forks. J Cell Biol 2024; 223:e202402144. [PMID: 38865090 PMCID: PMC11169917 DOI: 10.1083/jcb.202402144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 04/02/2024] [Accepted: 05/04/2024] [Indexed: 06/13/2024] Open
Abstract
CDC7 kinase is crucial for DNA replication initiation and is involved in fork processing and replication stress response. Human CDC7 requires the binding of either DBF4 or DRF1 for its activity. However, it is unclear whether the two regulatory subunits target CDC7 to a specific set of substrates, thus having different biological functions, or if they act redundantly. Using genome editing technology, we generated isogenic cell lines deficient in either DBF4 or DRF1: these cells are viable but present signs of genomic instability, indicating that both can independently support CDC7 for bulk DNA replication. Nonetheless, DBF4-deficient cells show altered replication efficiency, partial deficiency in MCM helicase phosphorylation, and alterations in the replication timing of discrete genomic regions. Notably, we find that CDC7 function at replication forks is entirely dependent on DBF4 and not on DRF1. Thus, DBF4 is the primary regulator of CDC7 activity, mediating most of its functions in unperturbed DNA replication and upon replication interference.
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Affiliation(s)
- Anja Göder
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway, Ireland
| | | | - Michael D. Rainey
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway, Ireland
| | - Aisling O’Connor
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway, Ireland
| | - Chiara Cazzaniga
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway, Ireland
| | - Daniel Shamavu
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway, Ireland
| | | | - Corrado Santocanale
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway, Ireland
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3
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Fukushima HS, Ikeda T, Ikeda S, Takeda H. Cell cycle length governs heterochromatin reprogramming during early development in non-mammalian vertebrates. EMBO Rep 2024; 25:3300-3323. [PMID: 38943003 PMCID: PMC11315934 DOI: 10.1038/s44319-024-00188-5] [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: 01/28/2024] [Revised: 06/06/2024] [Accepted: 06/12/2024] [Indexed: 06/30/2024] Open
Abstract
Heterochromatin marks such as H3K9me3 undergo global erasure and re-establishment after fertilization, and the proper reprogramming of H3K9me3 is essential for early development. Despite the widely conserved dynamics of heterochromatin reprogramming in invertebrates and non-mammalian vertebrates, previous studies have shown that the underlying mechanisms may differ between species. Here, we investigate the molecular mechanism of H3K9me3 dynamics in medaka (Japanese killifish, Oryzias latipes) as a non-mammalian vertebrate model, and show that rapid cell cycle during cleavage stages causes DNA replication-dependent passive erasure of H3K9me3. We also find that cell cycle slowing, toward the mid-blastula transition, permits increasing nuclear accumulation of H3K9me3 histone methyltransferase Setdb1, leading to the onset of H3K9me3 re-accumulation. We further demonstrate that cell cycle length in early development also governs H3K9me3 reprogramming in zebrafish and Xenopus laevis. Together with the previous studies in invertebrates, we propose that a cell cycle length-dependent mechanism for both global erasure and re-accumulation of H3K9me3 is conserved among rapid-cleavage species of non-mammalian vertebrates and invertebrates such as Drosophila, C. elegans, Xenopus and teleost fish.
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Affiliation(s)
- Hiroto S Fukushima
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033, Japan.
- Center for Integrative Medical Sciences, RIKEN, Yokohama, 230-0045, Japan.
| | - Takafumi Ikeda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033, Japan
- Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, 603-8555, Japan
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, 603-8555, Japan
| | - Shinra Ikeda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Hiroyuki Takeda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033, Japan.
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, 603-8555, Japan.
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4
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Schindler-Johnson M, Petridou NI. Collective effects of cell cleavage dynamics. Front Cell Dev Biol 2024; 12:1358971. [PMID: 38559810 PMCID: PMC10978805 DOI: 10.3389/fcell.2024.1358971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 03/05/2024] [Indexed: 04/04/2024] Open
Abstract
A conserved process of early embryonic development in metazoans is the reductive cell divisions following oocyte fertilization, termed cell cleavages. Cell cleavage cycles usually start synchronously, lengthen differentially between the embryonic cells becoming asynchronous, and cease before major morphogenetic events, such as germ layer formation and gastrulation. Despite exhibiting species-specific characteristics, the regulation of cell cleavage dynamics comes down to common controllers acting mostly at the single cell/nucleus level, such as nucleus-to-cytoplasmic ratio and zygotic genome activation. Remarkably, recent work has linked cell cleavage dynamics to the emergence of collective behavior during embryogenesis, including pattern formation and changes in embryo-scale mechanics, raising the question how single-cell controllers coordinate embryo-scale processes. In this review, we summarize studies across species where an association between cell cleavages and collective behavior was made, discuss the underlying mechanisms, and propose that cell-to-cell variability in cell cleavage dynamics can serve as a mechanism of long-range coordination in developing embryos.
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Affiliation(s)
- Magdalena Schindler-Johnson
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Faculty of Biosciences, Heidelberg University, Heidelberg, Germany
| | - Nicoletta I. Petridou
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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5
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Colding-Christensen CS, Kakulidis ES, Arroyo-Gomez J, Hendriks IA, Arkinson C, Fábián Z, Gambus A, Mailand N, Duxin JP, Nielsen ML. Profiling ubiquitin signalling with UBIMAX reveals DNA damage- and SCF β-Trcp1-dependent ubiquitylation of the actin-organizing protein Dbn1. Nat Commun 2023; 14:8293. [PMID: 38097601 PMCID: PMC10721886 DOI: 10.1038/s41467-023-43873-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 11/22/2023] [Indexed: 12/17/2023] Open
Abstract
Ubiquitin widely modifies proteins, thereby regulating most cellular functions. The complexity of ubiquitin signalling necessitates unbiased methods enabling global detection of dynamic protein ubiquitylation. Here, we describe UBIMAX (UBiquitin target Identification by Mass spectrometry in Xenopus egg extracts), which enriches ubiquitin-conjugated proteins and quantifies regulation of protein ubiquitylation under precise and adaptable conditions. We benchmark UBIMAX by investigating DNA double-strand break-responsive ubiquitylation events, identifying previously known targets and revealing the actin-organizing protein Dbn1 as a major target of DNA damage-induced ubiquitylation. We find that Dbn1 is targeted for proteasomal degradation by the SCFβ-Trcp1 ubiquitin ligase, in a conserved mechanism driven by ATM-mediated phosphorylation of a previously uncharacterized β-Trcp1 degron containing an SQ motif. We further show that this degron is sufficient to induce DNA damage-dependent protein degradation of a model substrate. Collectively, we demonstrate UBIMAX's ability to identify targets of stimulus-regulated ubiquitylation and reveal an SCFβ-Trcp1-mediated ubiquitylation mechanism controlled directly by the apical DNA damage response kinases.
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Affiliation(s)
- Camilla S Colding-Christensen
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Ellen S Kakulidis
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Javier Arroyo-Gomez
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Ivo A Hendriks
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Connor Arkinson
- Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, UK
- California Institute for Quantitative Biosciences and Department of Molecular and Cell Biology and Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, 94720, USA
| | - Zita Fábián
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Agnieszka Gambus
- Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, UK
| | - Niels Mailand
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Julien P Duxin
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
| | - Michael L Nielsen
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
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6
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Knoblochova L, Duricek T, Vaskovicova M, Zorzompokou C, Rayova D, Ferencova I, Baran V, Schultz RM, Hoffmann ER, Drutovic D. CHK1-CDC25A-CDK1 regulate cell cycle progression and protect genome integrity in early mouse embryos. EMBO Rep 2023; 24:e56530. [PMID: 37694680 PMCID: PMC10561370 DOI: 10.15252/embr.202256530] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 08/17/2023] [Accepted: 08/18/2023] [Indexed: 09/12/2023] Open
Abstract
After fertilization, remodeling of the oocyte and sperm genomes is essential to convert these highly differentiated and transcriptionally quiescent cells into early cleavage-stage blastomeres that are transcriptionally active and totipotent. This developmental transition is accompanied by cell cycle adaptation, such as lengthening or shortening of the gap phases G1 and G2. However, regulation of these cell cycle changes is poorly understood, especially in mammals. Checkpoint kinase 1 (CHK1) is a protein kinase that regulates cell cycle progression in somatic cells. Here, we show that CHK1 regulates cell cycle progression in early mouse embryos by restraining CDK1 kinase activity due to CDC25A phosphatase degradation. CHK1 kinase also ensures the long G2 phase needed for genome activation and reprogramming gene expression in two-cell stage mouse embryos. Finally, Chk1 depletion leads to DNA damage and chromosome segregation errors that result in aneuploidy and infertility.
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Affiliation(s)
- Lucie Knoblochova
- Institute of Animal Physiology and Genetics of the Czech Academy of SciencesLibechovCzech Republic
- Faculty of ScienceCharles UniversityPragueCzech Republic
| | - Tomas Duricek
- Institute of Animal Physiology and Genetics of the Czech Academy of SciencesLibechovCzech Republic
| | - Michaela Vaskovicova
- Institute of Animal Physiology and Genetics of the Czech Academy of SciencesLibechovCzech Republic
| | - Chrysoula Zorzompokou
- Institute of Animal Physiology and Genetics of the Czech Academy of SciencesLibechovCzech Republic
| | - Diana Rayova
- Institute of Animal Physiology and Genetics of the Czech Academy of SciencesLibechovCzech Republic
| | - Ivana Ferencova
- Institute of Animal Physiology and Genetics of the Czech Academy of SciencesLibechovCzech Republic
| | - Vladimir Baran
- Institute of Animal Physiology, Centre of Biosciences, Slovak Academy of SciencesKosiceSlovakia
| | - Richard M Schultz
- Department of BiologyUniversity of PennsylvaniaPhiladelphiaPAUSA
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary MedicineUniversity of CaliforniaDavisCAUSA
| | - Eva R Hoffmann
- DNRF Center for Chromosome Stability, Department of Cellular and Molecular Medicine, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - David Drutovic
- Institute of Animal Physiology and Genetics of the Czech Academy of SciencesLibechovCzech Republic
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7
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Feng SX, Wang X, Zhang Y, Qin G, Lin Q, Zhang YH. Genetic basis of embryo and juvenile physiological responses to salinity changes in freshwater pipefish ( Hippichthys heptagonus). Zool Res 2023; 44:743-746. [PMID: 37443403 PMCID: PMC10415779 DOI: 10.24272/j.issn.2095-8137.2023.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 07/12/2023] [Indexed: 07/15/2023] Open
Affiliation(s)
- Shi-Xiang Feng
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong 510301, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xin Wang
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong 510301, China
| | - Yuan Zhang
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong 510301, China
| | - Geng Qin
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong 510301, China
| | - Qiang Lin
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong 510301, China
- University of Chinese Academy of Sciences, Beijing 100049, China. E-mail:
| | - Yan-Hong Zhang
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong 510301, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, Shandong 266071, China. E-mail:
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8
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Guille M, Grainger R. Genetics and Gene Editing Methods in Xenopus laevis and Xenopus tropicalis. Cold Spring Harb Protoc 2023; 2023:pdb.top107045. [PMID: 36283837 DOI: 10.1101/pdb.top107045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Our understanding of biological systems has for many years been heavily influenced by experimental approaches that exploit genetic methods. These include gain-of-function experiments that overexpress transgenes or ectopically express injected RNA and loss-of-function experiments that knock out genes or knock down RNAs. Here, we review how these methods have been applied in Xenopus frogs and introduce a variety of protocols for genetic manipulation of Xenopus laevis and Xenopus tropicalis.
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Affiliation(s)
- Matthew Guille
- European Xenopus Resource Centre, School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2UP, United Kingdom
| | - Robert Grainger
- Department of Biology, University of Virginia, Charlottesville, Virginia 22903, USA
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9
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Hadzhiev Y, Wheatley L, Cooper L, Ansaloni F, Whalley C, Chen Z, Finaurini S, Gustincich S, Sanges R, Burgess S, Beggs A, Müller F. The miR-430 locus with extreme promoter density forms a transcription body during the minor wave of zygotic genome activation. Dev Cell 2023; 58:155-170.e8. [PMID: 36693321 PMCID: PMC9904021 DOI: 10.1016/j.devcel.2022.12.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 08/10/2022] [Accepted: 12/16/2022] [Indexed: 01/24/2023]
Abstract
In anamniote embryos, the major wave of zygotic genome activation starts during the mid-blastula transition. However, some genes escape global genome repression, are activated substantially earlier, and contribute to the minor wave of genome activation. The mechanisms underlying the minor wave of genome activation are little understood. We explored the genomic organization and cis-regulatory mechanisms of a transcription body, in which the minor wave of genome activation is first detected in zebrafish. We identified the miR-430 cluster as having excessive copy number and the highest density of Pol-II-transcribed promoters in the genome, and this is required for forming the transcription body. However, this transcription body is not essential for, nor does it encompasse, minor wave transcription globally. Instead, distinct minor-wave-specific promoter architecture suggests that promoter-autonomous mechanisms regulate the minor wave of genome activation. The minor-wave-specific features also suggest distinct transcription initiation mechanisms between the minor and major waves of genome activation.
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Affiliation(s)
- Yavor Hadzhiev
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Lucy Wheatley
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Ledean Cooper
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Federico Ansaloni
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK; Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy; Central RNA Laboratory, Istituto Italiano di Tecnologia (IIT), 16163 Genoa, Italy
| | - Celina Whalley
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Zhelin Chen
- South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China; Translational and Functional Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892-2152, USA
| | - Sara Finaurini
- Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy
| | - Stefano Gustincich
- Central RNA Laboratory, Istituto Italiano di Tecnologia (IIT), 16163 Genoa, Italy
| | - Remo Sanges
- Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy; Central RNA Laboratory, Istituto Italiano di Tecnologia (IIT), 16163 Genoa, Italy
| | - Shawn Burgess
- Translational and Functional Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892-2152, USA
| | - Andrew Beggs
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Ferenc Müller
- Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK.
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10
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Balachandra S, Sarkar S, Amodeo AA. The Nuclear-to-Cytoplasmic Ratio: Coupling DNA Content to Cell Size, Cell Cycle, and Biosynthetic Capacity. Annu Rev Genet 2022; 56:165-185. [PMID: 35977407 PMCID: PMC10165727 DOI: 10.1146/annurev-genet-080320-030537] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Though cell size varies between different cells and across species, the nuclear-to-cytoplasmic (N/C) ratio is largely maintained across species and within cell types. A cell maintains a relatively constant N/C ratio by coupling DNA content, nuclear size, and cell size. We explore how cells couple cell division and growth to DNA content. In some cases, cells use DNA as a molecular yardstick to control the availability of cell cycle regulators. In other cases, DNA sets a limit for biosynthetic capacity. Developmentally programmed variations in the N/C ratio for a given cell type suggest that a specific N/C ratio is required to respond to given physiological demands. Recent observations connecting decreased N/C ratios with cellular senescence indicate that maintaining the proper N/C ratio is essential for proper cellular functioning. Together, these findings suggest a causative, not simply correlative, role for the N/C ratio in regulating cell growth and cell cycle progression.
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Affiliation(s)
- Shruthi Balachandra
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA; ,
| | - Sharanya Sarkar
- Department of Microbiology and Immunology, Dartmouth College, Hanover, New Hampshire, USA;
| | - Amanda A Amodeo
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA; ,
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11
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Gillespie PJ, Blow JJ. DDK: The Outsourced Kinase of Chromosome Maintenance. BIOLOGY 2022; 11:biology11060877. [PMID: 35741398 PMCID: PMC9220011 DOI: 10.3390/biology11060877] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 05/31/2022] [Accepted: 06/02/2022] [Indexed: 11/16/2022]
Abstract
The maintenance of genomic stability during the mitotic cell-cycle not only demands that the DNA is duplicated and repaired with high fidelity, but that following DNA replication the chromatin composition is perpetuated and that the duplicated chromatids remain tethered until their anaphase segregation. The coordination of these processes during S phase is achieved by both cyclin-dependent kinase, CDK, and Dbf4-dependent kinase, DDK. CDK orchestrates the activation of DDK at the G1-to-S transition, acting as the ‘global’ regulator of S phase and cell-cycle progression, whilst ‘local’ control of the initiation of DNA replication and repair and their coordination with the re-formation of local chromatin environments and the establishment of chromatid cohesion are delegated to DDK. Here, we discuss the regulation and the multiple roles of DDK in ensuring chromosome maintenance. Regulation of replication initiation by DDK has long been known to involve phosphorylation of MCM2-7 subunits, but more recent results have indicated that Treslin:MTBP might also be important substrates. Molecular mechanisms by which DDK regulates replisome stability and replicated chromatid cohesion are less well understood, though important new insights have been reported recently. We discuss how the ‘outsourcing’ of activities required for chromosome maintenance to DDK allows CDK to maintain outright control of S phase progression and the cell-cycle phase transitions whilst permitting ongoing chromatin replication and cohesion establishment to be completed and achieved faithfully.
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12
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Borel V, Boeing S, Van Wietmarschen N, Sridharan S, Hill BR, Ombrato L, Perez-Lloret J, Jackson D, Goldstone R, Boulton SJ, Nussenzweig A, Bellelli R. Disrupted control of origin activation compromises genome integrity upon destabilization of Polε and dysfunction of the TRP53-CDKN1A/P21 axis. Cell Rep 2022; 39:110871. [PMID: 35649380 PMCID: PMC9637995 DOI: 10.1016/j.celrep.2022.110871] [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: 04/07/2021] [Revised: 02/16/2022] [Accepted: 05/04/2022] [Indexed: 11/28/2022] Open
Abstract
The maintenance of genome stability relies on coordinated control of origin activation and replication fork progression. How the interplay between these processes influences human genetic disease and cancer remains incompletely characterized. Here we show that mouse cells featuring Polε instability exhibit impaired genome-wide activation of DNA replication origins, in an origin-location-independent manner. Strikingly, Trp53 ablation in primary Polε hypomorphic cells increased Polε levels and origin activation and reduced DNA damage in a transcription-dependent manner. Transcriptome analysis of primary Trp53 knockout cells revealed that the TRP53-CDKN1A/P21 axis maintains appropriate levels of replication factors and CDK activity during unchallenged S phase. Loss of this control mechanism deregulates origin activation and perturbs genome-wide replication fork progression. Thus, while our data support an impaired origin activation model for genetic diseases affecting CMG formation, we propose that loss of the TRP53-CDKN1A/P21 tumor suppressor axis induces inappropriate origin activation and deregulates genome-wide fork progression.
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Affiliation(s)
- Valerie Borel
- The Francis Crick Institute, 1 Midland Road, NW1 1AT London, UK
| | - Stefan Boeing
- The Francis Crick Institute, 1 Midland Road, NW1 1AT London, UK
| | | | - Sriram Sridharan
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD, USA
| | - Bethany Rebekah Hill
- Centre for Cancer Cell and Molecular Biology, The Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, Barbican, EC1M 6BE London, UK
| | - Luigi Ombrato
- Centre for Tumour Microenvironment, The Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, Barbican, EC1M 6BE London, UK
| | | | - Deb Jackson
- The Francis Crick Institute, 1 Midland Road, NW1 1AT London, UK
| | | | - Simon J Boulton
- The Francis Crick Institute, 1 Midland Road, NW1 1AT London, UK
| | - Andre Nussenzweig
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD, USA
| | - Roberto Bellelli
- Centre for Cancer Cell and Molecular Biology, The Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, Barbican, EC1M 6BE London, UK.
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13
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Kinterová V, Kaňka J, Bartková A, Toralová T. SCF Ligases and Their Functions in Oogenesis and Embryogenesis-Summary of the Most Important Findings throughout the Animal Kingdom. Cells 2022; 11:234. [PMID: 35053348 PMCID: PMC8774150 DOI: 10.3390/cells11020234] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/07/2022] [Accepted: 01/09/2022] [Indexed: 12/10/2022] Open
Abstract
SCF-dependent proteolysis was first discovered via genetic screening of budding yeast almost 25 years ago. In recent years, more and more functions of SCF (Skp1-Cullin 1-F-box) ligases have been described, and we can expect the number of studies on this topic to increase. SCF ligases, which are E3 ubiquitin multi-protein enzymes, catalyse protein ubiquitination and thus allow protein degradation mediated by the 26S proteasome. They play a crucial role in the degradation of cell cycle regulators, regulation of the DNA repair and centrosome cycle and play an important role in several diseases. SCF ligases seem to be needed during all phases of development, from oocyte formation through fertilization, activation of the embryonic genome to embryo implantation. In this review, we summarize known data on SCF ligase-mediated degradation during oogenesis and embryogenesis. In particular, SCFβTrCP and SCFSEL-10/FBXW7 are among the most important and best researched ligases during early development. SCFβTrCP is crucial for the oogenesis of Xenopus and mouse and also in Xenopus and Drosophila embryogenesis. SCFSEL-10/FBXW7 participates in the degradation of several RNA-binding proteins and thereby affects the regulation of gene expression during the meiosis of C. elegans. Nevertheless, a large number of SCF ligases that are primarily involved in embryogenesis remain to be elucidated.
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Affiliation(s)
- Veronika Kinterová
- Laboratory of Developmental Biology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, 27721 Libechov, Czech Republic; (J.K.); (A.B.); (T.T.)
| | - Jiří Kaňka
- Laboratory of Developmental Biology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, 27721 Libechov, Czech Republic; (J.K.); (A.B.); (T.T.)
| | - Alexandra Bartková
- Laboratory of Developmental Biology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, 27721 Libechov, Czech Republic; (J.K.); (A.B.); (T.T.)
- Faculty of Natural Sciences, Constantine the Philosopher University in Nitra, 949 01 Nitra, Slovakia
| | - Tereza Toralová
- Laboratory of Developmental Biology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, 27721 Libechov, Czech Republic; (J.K.); (A.B.); (T.T.)
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14
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Jukam D, Kapoor RR, Straight AF, Skotheim JM. The DNA-to-cytoplasm ratio broadly activates zygotic gene expression in Xenopus. Curr Biol 2021; 31:4269-4281.e8. [PMID: 34388374 DOI: 10.1016/j.cub.2021.07.035] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 05/13/2021] [Accepted: 07/14/2021] [Indexed: 10/20/2022]
Abstract
In multicellular animals, the first major event after fertilization is the switch from maternal to zygotic control of development. During this transition, zygotic gene transcription is broadly activated in an otherwise quiescent genome in a process known as zygotic genome activation (ZGA). In fast-developing embryos, ZGA often overlaps with the slowing of initially synchronous cell divisions at the mid-blastula transition (MBT). Initial studies of the MBT led to the nuclear-to-cytoplasmic ratio model where MBT timing is regulated by the exponentially increasing amounts of some nuclear component "N" titrated against a fixed cytoplasmic component "C." However, more recent experiments have been interpreted to suggest that ZGA is independent of the N/C ratio. To determine the role of the N/C ratio in ZGA, we generated Xenopus frog embryos with ∼3-fold differences in genomic DNA (i.e., N) by using X. tropicalis sperm to fertilize X. laevis eggs with or without their maternal genome. Resulting embryos have otherwise identical X. tropicalis genome template amounts, embryo sizes, and X. laevis maternal environments. We generated transcriptomic time series across the MBT in both conditions and used X. tropicalis paternally derived mRNA to identify a high-confidence set of exclusively zygotic transcripts. Both ZGA and the increase in cell-cycle duration are delayed in embryos with ∼3-fold less DNA per cell. Thus, DNA is an important component of the N/C ratio, which is a critical regulator of zygotic genome activation in Xenopus embryos.
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Affiliation(s)
- David Jukam
- Department of Biology, Stanford University, Stanford, CA 94305, USA; Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Rishabh R Kapoor
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Aaron F Straight
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Jan M Skotheim
- Department of Biology, Stanford University, Stanford, CA 94305, USA.
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15
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Liu B, Zhao H, Wu K, Großhans J. Temporal Gradients Controlling Embryonic Cell Cycle. BIOLOGY 2021; 10:biology10060513. [PMID: 34207742 PMCID: PMC8228447 DOI: 10.3390/biology10060513] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 06/05/2021] [Accepted: 06/07/2021] [Indexed: 12/17/2022]
Abstract
Simple Summary Embryonic cells sense temporal gradients of regulatory signals to determine whether and when to proceed or remodel the cell cycle. Such a control mechanism is allowed to accurately link the cell cycle with the developmental program, including cell differentiation, morphogenesis, and gene expression. The mid-blastula transition has been a paradigm for timing in early embryogenesis in frog, fish, and fly, among others. It has been argued for decades now if the events associated with the mid-blastula transition, i.e., the onset of zygotic gene expression, remodeling of the cell cycle, and morphological changes, are determined by a control mechanism or by absolute time. Recent studies indicate that multiple independent signals and mechanisms contribute to the timing of these different processes. Here, we focus on the mechanisms for cell cycle remodeling, specifically in Drosophila, which relies on gradual changes of the signal over time. We discuss pathways for checkpoint activation, decay of Cdc25 protein levels, as well as depletion of deoxyribonucleotide metabolites and histone proteins. The gradual changes of these signals are linked to Cdk1 activity by readout mechanisms involving thresholds. Abstract Cell proliferation in early embryos by rapid cell cycles and its abrupt pause after a stereotypic number of divisions present an attractive system to study the timing mechanism in general and its coordination with developmental progression. In animals with large eggs, such as Xenopus, zebrafish, or Drosophila, 11–13 very fast and synchronous cycles are followed by a pause or slowdown of the cell cycle. The stage when the cell cycle is remodeled falls together with changes in cell behavior and activation of the zygotic genome and is often referred to as mid-blastula transition. The number of fast embryonic cell cycles represents a clear and binary readout of timing. Several factors controlling the cell cycle undergo dynamics and gradual changes in activity or concentration and thus may serve as temporal gradients. Recent studies have revealed that the gradual loss of Cdc25 protein, gradual depletion of free deoxyribonucleotide metabolites, or gradual depletion of free histone proteins impinge on Cdk1 activity in a threshold-like manner. In this review, we will highlight with a focus on Drosophila studies our current understanding and recent findings on the generation and readout of these temporal gradients, as well as their position within the regulatory network of the embryonic cell cycle.
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Affiliation(s)
- Boyang Liu
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan 250012, China; (B.L.); (H.Z.); (K.W.)
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Shandong University, Jinan 250012, China
- Shandong Key Laboratory of Reproductive Medicine, Jinan 250012, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan 250012, China
| | - Han Zhao
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan 250012, China; (B.L.); (H.Z.); (K.W.)
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Shandong University, Jinan 250012, China
- Shandong Key Laboratory of Reproductive Medicine, Jinan 250012, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan 250012, China
| | - Keliang Wu
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan 250012, China; (B.L.); (H.Z.); (K.W.)
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Shandong University, Jinan 250012, China
- Shandong Key Laboratory of Reproductive Medicine, Jinan 250012, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan 250012, China
| | - Jörg Großhans
- Department of Biology, Philipps University, 35043 Marburg, Germany
- Correspondence:
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16
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Shindo Y, Amodeo AA. Excess histone H3 is a competitive Chk1 inhibitor that controls cell-cycle remodeling in the early Drosophila embryo. Curr Biol 2021; 31:2633-2642.e6. [PMID: 33848457 DOI: 10.1016/j.cub.2021.03.035] [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: 09/21/2020] [Revised: 02/08/2021] [Accepted: 03/10/2021] [Indexed: 12/31/2022]
Abstract
The DNA damage checkpoint is crucial to protect genome integrity.1,2 However, the early embryos of many metazoans sacrifice this safeguard to allow for rapid cleavage divisions that are required for speedy development. At the mid-blastula transition (MBT), embryos switch from rapid cleavage divisions to slower, patterned divisions with the addition of gap phases and acquisition of DNA damage checkpoints. The timing of the MBT is dependent on the nuclear-to-cytoplasmic (N/C ratio)3-7 and the activation of the checkpoint kinase, Chk1.8-17 How Chk1 activity is coupled to the N/C ratio has remained poorly understood. Here, we show that dynamic changes in histone H3 availability in response to the increasing N/C ratio control Chk1 activity and thus time the MBT in the Drosophila embryo. We show that excess H3 in the early cycles interferes with cell-cycle slowing independent of chromatin incorporation. We find that the N-terminal tail of H3 acts as a competitive inhibitor of Chk1 in vitro and reduces Chk1 activity in vivo. Using a H3-tail mutant that has reduced Chk1 inhibitor activity, we show that the amount of available Chk1 sites in the H3 pool controls the dynamics of cell-cycle progression. Mathematical modeling quantitatively supports a mechanism where titration of H3 during early cleavage cycles regulates Chk1-dependent cell-cycle slowing. This study defines Chk1 regulation by H3 as a key mechanism that coordinates cell-cycle remodeling with developmental progression.
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Affiliation(s)
- Yuki Shindo
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Amanda A Amodeo
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA.
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17
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Islam S, Dutta P, Chopra K, Rapole S, Chauhan R, Santra MK. FBXW8 regulates G1 and S phases of cell cycle progression by restricting β-TrCP1 function. FEBS J 2021; 288:5474-5497. [PMID: 33742524 DOI: 10.1111/febs.15828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 01/21/2021] [Accepted: 03/18/2021] [Indexed: 11/30/2022]
Abstract
Sequential alteration in the expression levels of cell cycle regulatory proteins is crucial for faithful cell cycle progression to maintain the cellular homeostasis. F-box protein β-TrCP1 is known to control the expression levels of several important cell cycle regulatory proteins. However, how the function of β-TrCP1 is regulated in spatiotemporal manner during cell cycle progression remains elusive. Here, we show that expression levels of β-TrCP1 oscillate during cell cycle progression with a minimum level at the G1 and S phases of cell cycle. Using biochemical, flow cytometry, and immunofluorescence techniques, we found that oscillation of β-TrCP1 expression is controlled by another F-box protein FBXW8. FBXW8 directs the proteasomal degradation of β-TrCP1 in MAPK pathway-dependent manner. Interestingly, we found that the attenuation of β-TrCP1 by FBXW8 is important for Cdc25A-mediated cell cycle transition from G1 phase to S phase as well as DNA damage-free progression of S phase. Overall, our study reveals the intriguing molecular mechanism and significance of maintenance of β-TrCP1 levels during cell cycle progression by FBXW8-mediated proteasomal degradation.
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Affiliation(s)
- Sehbanul Islam
- Molecular Oncology Laboratory, National Centre for Cell Science, Pune, India.,Department of Biotechnology, Savitribai Phule Pune University, India
| | - Parul Dutta
- Molecular Oncology Laboratory, National Centre for Cell Science, Pune, India.,Department of Biotechnology, Savitribai Phule Pune University, India
| | - Kriti Chopra
- Laboratory of Structural Biology, National Centre for Cell Science, Pune, India
| | - Srikanth Rapole
- Proteomics Laboratory, National Centre for Cell Science, Pune, India
| | - Radha Chauhan
- Laboratory of Structural Biology, National Centre for Cell Science, Pune, India
| | - Manas Kumar Santra
- Molecular Oncology Laboratory, National Centre for Cell Science, Pune, India
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18
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Gaggioli V, Kieninger MR, Klucnika A, Butler R, Zegerman P. Identification of the critical replication targets of CDK reveals direct regulation of replication initiation factors by the embryo polarity machinery in C. elegans. PLoS Genet 2020; 16:e1008948. [PMID: 33320862 PMCID: PMC7771872 DOI: 10.1371/journal.pgen.1008948] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 12/29/2020] [Accepted: 11/02/2020] [Indexed: 12/26/2022] Open
Abstract
During metazoan development, the cell cycle is remodelled to coordinate proliferation with differentiation. Developmental cues cause dramatic changes in the number and timing of replication initiation events, but the mechanisms and physiological importance of such changes are poorly understood. Cyclin-dependent kinases (CDKs) are important for regulating S-phase length in many metazoa, and here we show in the nematode Caenorhabditis elegans that an essential function of CDKs during early embryogenesis is to regulate the interactions between three replication initiation factors SLD-3, SLD-2 and MUS-101 (Dpb11/TopBP1). Mutations that bypass the requirement for CDKs to generate interactions between these factors is partly sufficient for viability in the absence of Cyclin E, demonstrating that this is a critical embryonic function of this Cyclin. Both SLD-2 and SLD-3 are asymmetrically localised in the early embryo and the levels of these proteins inversely correlate with S-phase length. We also show that SLD-2 asymmetry is determined by direct interaction with the polarity protein PKC-3. This study explains an essential function of CDKs for replication initiation in a metazoan and provides the first direct molecular mechanism through which polarization of the embryo is coordinated with DNA replication initiation factors. How and when a cell divides changes as the cell assumes different fates. How these changes in cell division are brought about are poorly understood, but are critical to ensure that cells do not over-proliferate leading to cancer. The nematode C. elegans is an excellent system to study the role of cell cycle changes during animal development. Here we show that two factors SLD-2 and SLD-3 are critical to control the decision to begin genome duplication. We show that these factors are differently distributed to different cell lineages in the early embryo, which may be a key event in determining the cell cycle rate in these cells. For the first time we show that, PKC-3, a key component of the machinery that determines the front (anterior) from the back (posterior) of the embryo directly controls SLD-2 distribution, which might explain how the polarisation of the embryo causes changes in the proliferation of different cell lineages. As PKC-3 is frequently mutated in human cancers, how this factor controls cell proliferation may be important to understand tumour progression.
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Affiliation(s)
- Vincent Gaggioli
- Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
| | - Manuela R. Kieninger
- Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
| | - Anna Klucnika
- Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
- Department of Genetics, University of Cambridge, United Kingdom
| | - Richard Butler
- Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
| | - Philip Zegerman
- Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
- Department of Biochemistry, University of Cambridge, United Kingdom
- * E-mail:
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19
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Strong IJT, Lei X, Chen F, Yuan K, O’Farrell PH. Interphase-arrested Drosophila embryos activate zygotic gene expression and initiate mid-blastula transition events at a low nuclear-cytoplasmic ratio. PLoS Biol 2020; 18:e3000891. [PMID: 33090988 PMCID: PMC7608951 DOI: 10.1371/journal.pbio.3000891] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 11/03/2020] [Accepted: 09/14/2020] [Indexed: 11/18/2022] Open
Abstract
Externally deposited eggs begin development with an immense cytoplasm and a single overwhelmed nucleus. Rapid mitotic cycles restore normality as the ratio of nuclei to cytoplasm (N/C) increases. A threshold N/C has been widely proposed to activate zygotic genome transcription and onset of morphogenesis at the mid-blastula transition (MBT). To test whether a threshold N/C is required for these events, we blocked N/C increase by down-regulating cyclin/Cdk1 to arrest early cell cycles in Drosophila. Embryos that were arrested two cell cycles prior to the normal MBT activated widespread transcription of the zygotic genome including genes previously described as N/C dependent. Zygotic transcription of these genes largely retained features of their regulation in space and time. Furthermore, zygotically regulated post-MBT events such as cellularization and gastrulation movements occurred in these cell cycle-arrested embryos. These results are not compatible with models suggesting that these MBT events are directly coupled to N/C. Cyclin/Cdk1 activity normally declines in tight association with increasing N/C and is regulated by N/C. By experimentally promoting the decrease in cyclin/Cdk1, we uncoupled MBT from N/C increase, arguing that N/C-guided down-regulation of cyclin/Cdk1 is sufficient for genome activation and MBT.
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Affiliation(s)
- Isaac J. T. Strong
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
| | - Xiaoyun Lei
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Fang Chen
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Kai Yuan
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
- Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Patrick H. O’Farrell
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
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20
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Toralova T, Kinterova V, Chmelikova E, Kanka J. The neglected part of early embryonic development: maternal protein degradation. Cell Mol Life Sci 2020; 77:3177-3194. [PMID: 32095869 PMCID: PMC11104927 DOI: 10.1007/s00018-020-03482-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 01/24/2020] [Accepted: 02/07/2020] [Indexed: 12/28/2022]
Abstract
The degradation of maternally provided molecules is a very important process during early embryogenesis. However, the vast majority of studies deals with mRNA degradation and protein degradation is only a very little explored process yet. The aim of this article was to summarize current knowledge about the protein degradation during embryogenesis of mammals. In addition to resuming of known data concerning mammalian embryogenesis, we tried to fill the gaps in knowledge by comparison with facts known about protein degradation in early embryos of non-mammalian species. Maternal protein degradation seems to be driven by very strict rules in terms of specificity and timing. The degradation of some maternal proteins is certainly necessary for the normal course of embryonic genome activation (EGA) and several concrete proteins that need to be degraded before major EGA have been already found. Nevertheless, the most important period seems to take place even before preimplantation development-during oocyte maturation. The defects arisen during this period seems to be later irreparable.
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Affiliation(s)
- Tereza Toralova
- Laboratory of Developmental Biology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, Libechov, Czech Republic
| | - Veronika Kinterova
- Laboratory of Developmental Biology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, Libechov, Czech Republic.
- Department of Veterinary Sciences, Czech University of Life Sciences in Prague, Prague, Czech Republic.
| | - Eva Chmelikova
- Department of Veterinary Sciences, Czech University of Life Sciences in Prague, Prague, Czech Republic
| | - Jiri Kanka
- Laboratory of Developmental Biology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, Libechov, Czech Republic
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21
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Chromatin and Nuclear Architecture: Shaping DNA Replication in 3D. Trends Genet 2020; 36:967-980. [PMID: 32713597 DOI: 10.1016/j.tig.2020.07.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/26/2020] [Accepted: 07/02/2020] [Indexed: 12/13/2022]
Abstract
In eukaryotes, DNA replication progresses through a finely orchestrated temporal and spatial program. The 3D genome structure and nuclear architecture have recently emerged as fundamental determinants of the replication program. Factors with established roles in replication have been recognized as genome organization regulators. Exploiting paradigms from yeasts and mammals, we discuss how DNA replication is regulated in time and space through DNA-associated trans-acting factors, diffusible limiting replication initiation factors, higher-order chromatin folding, dynamic origin localization, and specific nuclear microenvironments. We present an integrated model for the regulation of DNA replication in 3D and highlight the importance of accurate spatio-temporal regulation of DNA replication in physiology and disease.
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22
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Berthel E, Vincent A, Eberst L, Torres AG, Dacheux E, Rey C, Marcel V, Paraqindes H, Lachuer J, Catez F, de Pouplana LR, Treilleux I, Diaz JJ, Dalla Venezia N. Uncovering the Translational Regulatory Activity of the Tumor Suppressor BRCA1. Cells 2020; 9:cells9040941. [PMID: 32290274 PMCID: PMC7226996 DOI: 10.3390/cells9040941] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/30/2020] [Accepted: 04/04/2020] [Indexed: 12/24/2022] Open
Abstract
BRCA1 inactivation is a hallmark of familial breast cancer, often associated with aggressive triple negative breast cancers. BRCA1 is a tumor suppressor with known functions in DNA repair, transcription regulation, cell cycle control, and apoptosis. In the present study, we demonstrate that BRCA1 is also a translational regulator. We previously showed that BRCA1 was implicated in translation regulation. Here, we asked whether translational control could be a novel function of BRCA1 that contributes to its tumor suppressive activity. A combination of RNA-binding protein immunoprecipitation, microarray analysis, and polysome profiling, was used to identify the mRNAs that were specifically deregulated under BRCA1 deficiency. Western blot analysis allowed us to confirm at the protein level the deregulated translation of a subset of mRNAs. A unique and dedicated cohort of patients with documented germ-line BRCA1 pathogenic variant statues was set up, and tissue microarrays with the biopsies of these patients were constructed and analyzed by immunohistochemistry for their content in each candidate protein. Here, we show that BRCA1 translationally regulates a subset of mRNAs with which it associates. These mRNAs code for proteins involved in major programs in cancer. Accordingly, the level of these key proteins is correlated with BRCA1 status in breast cancer cell lines and in patient breast tumors. ADAT2, one of these key proteins, is proposed as a predictive biomarker of efficacy of treatments recently recommended to patients with BRCA1 deficiency. This study proposes that translational control may represent a novel molecular mechanism with potential clinical impact through which BRCA1 is a tumor suppressor.
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Affiliation(s)
- Elise Berthel
- Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon 1, Centre Léon Bérard, F-69008 Lyon, France; (E.B.) ; (A.V.) ; (E.D.) ; (V.M.) ; (H.P.) ; (F.C.) ; (J.-J.D.)
| | - Anne Vincent
- Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon 1, Centre Léon Bérard, F-69008 Lyon, France; (E.B.) ; (A.V.) ; (E.D.) ; (V.M.) ; (H.P.) ; (F.C.) ; (J.-J.D.)
| | - Lauriane Eberst
- Centre Léon Bérard, Medical Oncology Department, Université de Lyon 1, F-69008 Lyon, France;
| | - Adrian Gabriel Torres
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10, 08028 Barcelona, Spain; (A.G.T.); (L.R.d.P.)
| | - Estelle Dacheux
- Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon 1, Centre Léon Bérard, F-69008 Lyon, France; (E.B.) ; (A.V.) ; (E.D.) ; (V.M.) ; (H.P.) ; (F.C.) ; (J.-J.D.)
| | - Catherine Rey
- ProfileXpert, UNIV-US7 INSERM-UMS 3453 CNRS, F-69000 Lyon, France; (C.R.); (J.L.)
| | - Virginie Marcel
- Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon 1, Centre Léon Bérard, F-69008 Lyon, France; (E.B.) ; (A.V.) ; (E.D.) ; (V.M.) ; (H.P.) ; (F.C.) ; (J.-J.D.)
| | - Hermes Paraqindes
- Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon 1, Centre Léon Bérard, F-69008 Lyon, France; (E.B.) ; (A.V.) ; (E.D.) ; (V.M.) ; (H.P.) ; (F.C.) ; (J.-J.D.)
| | - Joël Lachuer
- ProfileXpert, UNIV-US7 INSERM-UMS 3453 CNRS, F-69000 Lyon, France; (C.R.); (J.L.)
| | - Frédéric Catez
- Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon 1, Centre Léon Bérard, F-69008 Lyon, France; (E.B.) ; (A.V.) ; (E.D.) ; (V.M.) ; (H.P.) ; (F.C.) ; (J.-J.D.)
| | - Lluis Ribas de Pouplana
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10, 08028 Barcelona, Spain; (A.G.T.); (L.R.d.P.)
- Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluis Companys 23, 08010 Barcelona, Spain
| | - Isabelle Treilleux
- Department of Translational Research and Innovation, Centre Léon Bérard, F-69008 Lyon, France;
| | - Jean-Jacques Diaz
- Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon 1, Centre Léon Bérard, F-69008 Lyon, France; (E.B.) ; (A.V.) ; (E.D.) ; (V.M.) ; (H.P.) ; (F.C.) ; (J.-J.D.)
| | - Nicole Dalla Venezia
- Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon 1, Centre Léon Bérard, F-69008 Lyon, France; (E.B.) ; (A.V.) ; (E.D.) ; (V.M.) ; (H.P.) ; (F.C.) ; (J.-J.D.)
- Correspondence: ; Tel.: +33-426-556-745
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23
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SSRP1-mediated histone H1 eviction promotes replication origin assembly and accelerated development. Nat Commun 2020; 11:1345. [PMID: 32165637 PMCID: PMC7067836 DOI: 10.1038/s41467-020-15180-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 02/24/2020] [Indexed: 12/17/2022] Open
Abstract
In several metazoans, the number of active replication origins in embryonic nuclei is higher than in somatic ones, ensuring rapid genome duplication during synchronous embryonic cell divisions. High replication origin density can be restored by somatic nuclear reprogramming. However, mechanisms underlying high replication origin density formation coupled to rapid cell cycles are poorly understood. Here, using Xenopus laevis, we show that SSRP1 stimulates replication origin assembly on somatic chromatin by promoting eviction of histone H1 through its N-terminal domain. Histone H1 removal derepresses ORC and MCM chromatin binding, allowing efficient replication origin assembly. SSRP1 protein decays at mid-blastula transition (MBT) when asynchronous somatic cell cycles start. Increasing levels of SSRP1 delay MBT and, surprisingly, accelerate post-MBT cell cycle speed and embryo development. These findings identify a major epigenetic mechanism regulating DNA replication and directly linking replication origin assembly, cell cycle duration and embryo development in vertebrates. During embryonic development, it is vital to maintain rapid genome duplication. Here, the authors shed light on the mechanism by revealing that SSRP1 stimulates replication origin assembly on somatic nuclei in Xenopus laevis egg extract by promoting histone H1 eviction from somatic chromatin.
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24
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Chan SH, Tang Y, Miao L, Darwich-Codore H, Vejnar CE, Beaudoin JD, Musaev D, Fernandez JP, Benitez MDJ, Bazzini AA, Moreno-Mateos MA, Giraldez AJ. Brd4 and P300 Confer Transcriptional Competency during Zygotic Genome Activation. Dev Cell 2020; 49:867-881.e8. [PMID: 31211993 DOI: 10.1016/j.devcel.2019.05.037] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 01/10/2019] [Accepted: 05/21/2019] [Indexed: 12/28/2022]
Abstract
The awakening of the genome after fertilization is a cornerstone of animal development. However, the mechanisms that activate the silent genome after fertilization are poorly understood. Here, we show that transcriptional competency is regulated by Brd4- and P300-dependent histone acetylation in zebrafish. Live imaging of transcription revealed that genome activation, beginning at the miR-430 locus, is gradual and stochastic. We show that genome activation does not require slowdown of the cell cycle and is regulated through the translation of maternally inherited mRNAs. Among these, the enhancer regulators P300 and Brd4 can prematurely activate transcription and restore transcriptional competency when maternal mRNA translation is blocked, whereas inhibition of histone acetylation blocks genome activation. We conclude that P300 and Brd4 are sufficient to trigger genome-wide transcriptional competency by regulating histone acetylation on the first zygotic genes in zebrafish. This mechanism is critical for initiating zygotic development and developmental reprogramming.
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Affiliation(s)
- Shun Hang Chan
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Yin Tang
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Liyun Miao
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Hiba Darwich-Codore
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Charles E Vejnar
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Jean-Denis Beaudoin
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Damir Musaev
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Juan P Fernandez
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Maria D J Benitez
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Ariel A Bazzini
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | | | - Antonio J Giraldez
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA; Stem Cell Center, Yale University School of Medicine, New Haven, CT 06510, USA; Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06510, USA.
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25
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Abstract
The genetic control of the characteristic cell sizes of different species and tissues is a long-standing enigma. Plants are convenient for studying this question in a multicellular context, as their cells do not move and are easily tracked and measured from organ initiation in the meristems to subsequent morphogenesis and differentiation. In this article, we discuss cell size control in plants compared with other organisms. As seen from yeast cells to mammalian cells, size homeostasis is maintained cell autonomously in the shoot meristem. In developing organs, vacuolization contributes to cell size heterogeneity and may resolve conflicts between growth control at the cellular and organ levels. Molecular mechanisms for cell size control have implications for how cell size responds to changes in ploidy, which are particularly important in plant development and evolution. We also discuss comparatively the functional consequences of cell size and their potential repercussions at higher scales, including genome evolution.
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Affiliation(s)
- Marco D'Ario
- Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Robert Sablowski
- Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
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26
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Kermi C, Aze A, Maiorano D. Preserving Genome Integrity During the Early Embryonic DNA Replication Cycles. Genes (Basel) 2019; 10:genes10050398. [PMID: 31137726 PMCID: PMC6563053 DOI: 10.3390/genes10050398] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 05/15/2019] [Indexed: 02/06/2023] Open
Abstract
During the very early stages of embryonic development chromosome replication occurs under rather challenging conditions, including a very short cell cycle, absence of transcription, a relaxed DNA damage response and, in certain animal species, a highly contracted S-phase. This raises the puzzling question of how the genome can be faithfully replicated in such a peculiar metabolic context. Recent studies have provided new insights into this issue, and unveiled that embryos are prone to accumulate genetic and genomic alterations, most likely due to restricted cellular functions, in particular reduced DNA synthesis quality control. These findings may explain the low rate of successful development in mammals and the occurrence of diseases, such as abnormal developmental features and cancer. In this review, we will discuss recent findings in this field and put forward perspectives to further study this fascinating question.
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Affiliation(s)
- Chames Kermi
- Laboratoire Surveillance et Stabilité du Génome, Institut de Génétique Humaine, UMR9002, CNRS, Université de Montpellier, 34090 Montpellier, France.
- Department of Chemical and Systems Biology, Stanford University School of Medicine, 318 Campus Drive, Stanford, CA 94305-5441, USA.
| | - Antoine Aze
- Laboratoire Surveillance et Stabilité du Génome, Institut de Génétique Humaine, UMR9002, CNRS, Université de Montpellier, 34090 Montpellier, France.
| | - Domenico Maiorano
- Laboratoire Surveillance et Stabilité du Génome, Institut de Génétique Humaine, UMR9002, CNRS, Université de Montpellier, 34090 Montpellier, France.
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27
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A cell cycle-coordinated Polymerase II transcription compartment encompasses gene expression before global genome activation. Nat Commun 2019; 10:691. [PMID: 30741925 PMCID: PMC6370886 DOI: 10.1038/s41467-019-08487-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 01/02/2019] [Indexed: 02/07/2023] Open
Abstract
Most metazoan embryos commence development with rapid, transcriptionally silent cell divisions, with genome activation delayed until the mid-blastula transition (MBT). However, a set of genes escapes global repression and gets activated before MBT. Here we describe the formation and the spatio-temporal dynamics of a pair of distinct transcription compartments, which encompasses the earliest gene expression in zebrafish. 4D imaging of pri-miR430 and zinc-finger-gene activities by a novel, native transcription imaging approach reveals transcriptional sharing of nuclear compartments, which are regulated by homologous chromosome organisation. These compartments carry the majority of nascent-RNAs and active Polymerase II, are chromatin-depleted and represent the main sites of detectable transcription before MBT. Transcription occurs during the S-phase of increasingly permissive cleavage cycles. It is proposed, that the transcription compartment is part of the regulatory architecture of embryonic nuclei and offers a transcriptionally competent environment to facilitate early escape from repression before global genome activation. Transcription is globally repressed in early stage of embryo development, but a set of genes including pri-miR-430 and zinc finger genes is known to escape the repression. Here the authors image the very first transcriptional activities in the living zebra fish embryo, demonstrating a cell cycle-coordinated polymerase II transcription compartment.
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28
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Ciardo D, Goldar A, Marheineke K. On the Interplay of the DNA Replication Program and the Intra-S Phase Checkpoint Pathway. Genes (Basel) 2019; 10:E94. [PMID: 30700024 PMCID: PMC6410103 DOI: 10.3390/genes10020094] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 01/23/2019] [Accepted: 01/25/2019] [Indexed: 12/12/2022] Open
Abstract
DNA replication in eukaryotes is achieved by the activation of multiple replication origins which needs to be precisely coordinated in space and time. This spatio-temporal replication program is regulated by many factors to maintain genome stability, which is frequently threatened through stresses of exogenous or endogenous origin. Intra-S phase checkpoints monitor the integrity of DNA synthesis and are activated when replication forks are stalled. Their activation leads to the stabilization of forks, to the delay of the replication program by the inhibition of late firing origins, and the delay of G2/M phase entry. In some cell cycles during early development these mechanisms are less efficient in order to allow rapid cell divisions. In this article, we will review our current knowledge of how the intra-S phase checkpoint regulates the replication program in budding yeast and metazoan models, including early embryos with rapid S phases. We sum up current models on how the checkpoint can inhibit origin firing in some genomic regions, but allow dormant origin activation in other regions. Finally, we discuss how numerical and theoretical models can be used to connect the multiple different actors into a global process and to extract general rules.
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Affiliation(s)
- Diletta Ciardo
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette CEDEX, France.
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29
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Torres-Zelada EF, Stephenson RE, Alpsoy A, Anderson BD, Swanson SK, Florens L, Dykhuizen EC, Washburn MP, Weake VM. The Drosophila Dbf4 ortholog Chiffon forms a complex with Gcn5 that is necessary for histone acetylation and viability. J Cell Sci 2019; 132:jcs.214072. [PMID: 30559249 DOI: 10.1242/jcs.214072] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 12/11/2018] [Indexed: 02/05/2023] Open
Abstract
Metazoans contain two homologs of the Gcn5-binding protein Ada2, Ada2a and Ada2b, which nucleate formation of the ATAC and SAGA complexes, respectively. In Drosophila melanogaster, there are two splice isoforms of Ada2b: Ada2b-PA and Ada2b-PB. Here, we show that only the Ada2b-PB isoform is in SAGA; in contrast, Ada2b-PA associates with Gcn5, Ada3, Sgf29 and Chiffon, forming the Chiffon histone acetyltransferase (CHAT) complex. Chiffon is the Drosophila ortholog of Dbf4, which binds and activates the cell cycle kinase Cdc7 to initiate DNA replication. In flies, Chiffon and Cdc7 are required in ovary follicle cells for gene amplification, a specialized form of DNA re-replication. Although chiffon was previously reported to be dispensable for viability, here, we find that Chiffon is required for both histone acetylation and viability in flies. Surprisingly, we show that chiffon is a dicistronic gene that encodes distinct Cdc7- and CHAT-binding polypeptides. Although the Cdc7-binding domain of Chiffon is not required for viability in flies, the CHAT-binding domain is essential for viability, but is not required for gene amplification, arguing against a role in DNA replication.
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Affiliation(s)
| | - Robert E Stephenson
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Aktan Alpsoy
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
| | - Benjamin D Anderson
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Selene K Swanson
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA
| | - Laurence Florens
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA
| | - Emily C Dykhuizen
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
| | - Michael P Washburn
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA.,Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Vikki M Weake
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA .,Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
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30
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Seller CA, O’Farrell PH. Rif1 prolongs the embryonic S phase at the Drosophila mid-blastula transition. PLoS Biol 2018; 16:e2005687. [PMID: 29746464 PMCID: PMC5963817 DOI: 10.1371/journal.pbio.2005687] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/22/2018] [Accepted: 04/23/2018] [Indexed: 01/09/2023] Open
Abstract
In preparation for dramatic morphogenetic events of gastrulation, rapid embryonic cell cycles slow at the mid-blastula transition (MBT). In Drosophila melanogaster embryos, down-regulation of cyclin-dependent kinase 1 (Cdk1) activity initiates this slowing by delaying replication of heterochromatic satellite sequences and extending S phase. We found that Cdk1 activity inhibited the chromatin association of Rap1 interacting factor 1 (Rif1), a candidate repressor of replication. Furthermore, Rif1 bound selectively to satellite sequences following Cdk1 down-regulation at the MBT. In the next S phase, Rif1 dissociated from different satellites in an orderly schedule that anticipated their replication. Rif1 lacking potential phosphorylation sites failed to dissociate and dominantly prevented completion of replication. Loss of Rif1 in mutant embryos shortened the post-MBT S phase and rescued embryonic cell cycles disrupted by depletion of the S phase–promoting kinase, cell division cycle 7 (Cdc7). Our work shows that Rif1 and S phase kinases compose a replication timer controlling first the developmental onset of late replication and then the precise schedule of replication within S phase. In addition, we describe how onset of late replication fits into the progressive maturation of heterochromatin during development. Cells divide rapidly in the early embryos of most animals. However, during a conserved period of development known as the mid-blastula transition (MBT), the cell cycle slows down dramatically. In Drosophila embryos, genome duplication abruptly slows to initiate this cell cycle prolongation. This is achieved through the onset of late replication, a well-recognized phenomenon in which specific sequences of the genome await replication until long after other sequences have finished. Even though this temporal program of replication is a major determinant of the duration of S phase, the factors involved in this process remain unknown. Here, we use genetics and real-time microscopy to visualize replication in developing fly embryos and show that the protein Rap1 interacting factor 1 (Rif1) mediates the introduction of late replication at the MBT. We find that at this stage, Rif1 binds to and selectively delays the replication of large blocks of repetitive DNA known as satellite sequences. During the rapid cell cycles before the MBT, we show that the cyclin-dependent kinase 1 (Cdk1) prevents Rif1 from slowing down DNA replication by driving its removal from the chromatin. The developmental down-regulation of Cdk1 at the MBT allows Rif1 to associate with the satellite sequences and initiate cell cycle slowing. Our work provides new insights into the temporal programming of S phase and into the embryonic origin of late replication.
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Affiliation(s)
- Charles A. Seller
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
| | - Patrick H. O’Farrell
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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31
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Abstract
Background. Nuclear size is a tightly regulated cellular feature. Mechanisms that regulate nuclear size and the functional significance of this regulation are largely unknown. Nuclear size and morphology are often altered in many diseases, such as cancer. Therefore, understanding the mechanisms that regulate nuclear size is crucial to provide insight into the role of nuclear size in disease. Scope and Approach. The goal of this review is to summarize the most recent studies about the mechanisms and functional significance of nuclear size control using the Xenopus model system. First, this review describes how Xenopus egg extracts, embryos, and embryo extracts are prepared and used in scientific research. Next, the review focuses on the mechanisms and functional effects of proper nuclear size control that have been learned using the Xenopus system. Key Findings and Conclusions. Xenopus is an excellent in vivo and in vitro experimental platform to study mechanisms of nuclear size control. Given its close evolutionary relationship with mammals and that most cellular processes and pathways are highly conserved between Xenopus and humans, the Xenopus system has been a valuable tool to advance biomedical research. Some of the mechanisms that regulate nuclear size include components of nuclear import such as importin α and NTF2, nuclear lamins, nucleoporins, proteins that regulate the morphology of the endoplasmic reticulum, and cytoskeletal elements.
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