1
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Messer CL, Fox DT. Broken chromosomes heading into mitosis: More than one way to patch a flat tire. J Cell Biol 2024; 223:e202401085. [PMID: 38477879 PMCID: PMC10937182 DOI: 10.1083/jcb.202401085] [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: 01/17/2024] [Revised: 02/22/2024] [Accepted: 02/23/2024] [Indexed: 03/14/2024] Open
Abstract
A cell dealing with a broken chromosome in mitosis is like a driver dealing with a flat tire on the highway: damage repair must occur under non-ideal circumstances. Mitotic chromosome breaks encounter problems related to structures called micronuclei. These aberrant nuclei are linked to cell death, mutagenesis, and cancer. In the last few years, a flurry of studies illuminated two mechanisms that prevent mitotic problems related to micronuclei. One mechanism prevents micronuclei from forming during mitosis and involves DNA Polymerase Theta, a DNA repair regulator that patches up broken mitotic chromosomes. A second mechanism is activated after micronuclei form and then rupture, and involves CIP2A and TOPBP1 proteins, which patch micronuclear fragments to promote their subsequent mitotic segregation. Here, we review recent progress in this field of mitotic DNA damage and discuss why multiple mechanisms exist. Future studies in this exciting area will reveal new DNA break responses and inform therapeutic strategies.
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Affiliation(s)
- C. Luke Messer
- Department of Biology, St. Bonaventure University, St. Bonaventure, NY, USA
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Donald T. Fox
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
- Duke Regeneration Center, Duke University Medical Center, Durham, NC, USA
- Duke Cancer Institute, Duke University Medical Center, Durham, NC, USA
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2
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Kiparaki M, Baker NE. Ribosomal protein mutations and cell competition: autonomous and nonautonomous effects on a stress response. Genetics 2023; 224:iyad080. [PMID: 37267156 PMCID: PMC10691752 DOI: 10.1093/genetics/iyad080] [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: 01/09/2023] [Accepted: 04/16/2023] [Indexed: 06/04/2023] Open
Abstract
Ribosomal proteins (Rps) are essential for viability. Genetic mutations affecting Rp genes were first discovered in Drosophila, where they represent a major class of haploinsufficient mutations. One mutant copy gives rise to the dominant "Minute" phenotype, characterized by slow growth and small, thin bristles. Wild-type (WT) and Minute cells compete in mosaics, that is, Rp+/- are preferentially lost when their neighbors are of the wild-type genotype. Many features of Rp gene haploinsufficiency (i.e. Rp+/- phenotypes) are mediated by a transcriptional program. In Drosophila, reduced translation and slow growth are under the control of Xrp1, a bZip-domain transcription factor induced in Rp mutant cells that leads ultimately to the phosphorylation of eIF2α and consequently inhibition of most translation. Rp mutant phenotypes are also mediated transcriptionally in yeast and in mammals. In mammals, the Impaired Ribosome Biogenesis Checkpoint activates p53. Recent findings link Rp mutant phenotypes to other cellular stresses, including the DNA damage response and endoplasmic reticulum stress. We suggest that cell competition results from nonautonomous inputs to stress responses, bringing decisions between adaptive and apoptotic outcomes under the influence of nearby cells. In Drosophila, cell competition eliminates aneuploid cells in which loss of chromosome leads to Rp gene haploinsufficiency. The effects of Rp gene mutations on the whole organism, in Minute flies or in humans with Diamond-Blackfan Anemia, may be inevitable consequences of pathways that are useful in eliminating individual cells from mosaics. Alternatively, apparently deleterious whole organism phenotypes might be adaptive, preventing even more detrimental outcomes. In mammals, for example, p53 activation appears to suppress oncogenic effects of Rp gene haploinsufficiency.
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Affiliation(s)
- Marianthi Kiparaki
- Institute for Fundamental Biomedical Research, Biomedical Sciences Research Center “Alexander Fleming”, Vari 16672, Greece
| | - Nicholas E Baker
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Department of Visual Sciences and Ophthalmology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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3
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Hill HJ, Bonser D, Golic KG. Dicentric chromosome breakage in Drosophila melanogaster is influenced by pericentric heterochromatin and occurs in nonconserved hotspots. Genetics 2023; 224:iyad052. [PMID: 37010100 PMCID: PMC10213500 DOI: 10.1093/genetics/iyad052] [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: 10/18/2022] [Revised: 10/18/2022] [Accepted: 03/13/2023] [Indexed: 04/04/2023] Open
Abstract
Chromosome breakage plays an important role in the evolution of karyotypes and can produce deleterious effects within a single individual, such as aneuploidy or cancer. Forces that influence how and where chromosomes break are not fully understood. In humans, breakage tends to occur in conserved hotspots called common fragile sites (CFS), especially during replication stress. By following the fate of dicentric chromosomes in Drosophila melanogaster, we find that breakage under tension also tends to occur in specific hotspots. Our experimental approach was to induce sister chromatid exchange in a ring chromosome to generate a dicentric chromosome with a double chromatid bridge. In the following cell division, the dicentric bridges may break. We analyzed the breakage patterns of 3 different ring-X chromosomes. These chromosomes differ by the amount and quality of heterochromatin they carry as well as their genealogical history. For all 3 chromosomes, breakage occurs preferentially in several hotspots. Surprisingly, we found that the hotspot locations are not conserved between the 3 chromosomes: each displays a unique array of breakage hotspots. The lack of hotspot conservation, along with a lack of response to aphidicolin, suggests that these breakage sites are not entirely analogous to CFS and may reveal new mechanisms of chromosome fragility. Additionally, the frequency of dicentric breakage and the durability of each chromosome's spindle attachment vary significantly between the 3 chromosomes and are correlated with the origin of the centromere and the amount of pericentric heterochromatin. We suggest that different centromere strengths could account for this.
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Affiliation(s)
- Hunter J Hill
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Danielle Bonser
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Kent G Golic
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
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4
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Warecki B, Bast I, Tajima M, Sullivan W. Connections between sister and non-sister telomeres of segregating chromatids maintain euploidy. Curr Biol 2023; 33:58-74.e5. [PMID: 36525974 PMCID: PMC9839490 DOI: 10.1016/j.cub.2022.11.038] [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: 05/04/2022] [Revised: 10/05/2022] [Accepted: 11/17/2022] [Indexed: 12/23/2022]
Abstract
The complete separation of sister chromatids during anaphase is a fundamental requirement for successful mitosis. Therefore, divisions with either persistent DNA-based connections or lagging chromosome fragments threaten aneuploidy if unresolved. Here, we demonstrate the existence of an anaphase mechanism in normally dividing cells in which pervasive connections between telomeres of segregating chromosomes aid in rescuing lagging chromosome fragments. We observe that in a large proportion of Drosophila melanogaster neuronal stem cell divisions, early anaphase sister and non-sister chromatids remain connected by thin telomeric DNA threads. Normally, these threads are resolved in mid-to-late anaphase via a spatial mechanism. However, we find that the presence of a nearby unrepaired DNA break recruits histones, BubR1 kinase, Polo kinase, Aurora B kinase, and BAF to the telomeric thread of the broken chromosome, stabilizing it. Stabilized connections then aid lagging chromosome rescue. These results suggest a model in which pervasive anaphase telomere-telomere connections that are normally resolved quickly can instead be stabilized to retain wayward chromosome fragments. Thus, the liability of persistent anaphase inter-chromosomal connections in normal divisions may be offset by their ability to maintain euploidy in the face of chromosome damage and genome loss.
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Affiliation(s)
- Brandt Warecki
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA.
| | - Ian Bast
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
| | - Matthew Tajima
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
| | - William Sullivan
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
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5
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Hill HJ, Golic KG. Chromosome Tug of War: Dicentric Chromosomes and the Centromere Strength Hypothesis. Cells 2022; 11:3550. [PMID: 36428979 PMCID: PMC9688759 DOI: 10.3390/cells11223550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Accepted: 11/09/2022] [Indexed: 11/12/2022] Open
Abstract
It has been 70 years since the concept of varied centromere strengths was introduced based on the behavior of dicentric chromosomes. One of the key conclusions from those early experiments was that some centromeres could pull with sufficient force to break a dicentric chromosome bridge, while others could not. In the ensuing decades there have been numerous studies to characterize strengths of the various components involved, such as the spindle, the kinetochore, and the chromosome itself. We review these various measurements to determine if the conclusions about centromere strength are supported by current evidence, with special attention to characterization of Drosophila melanogaster kinetochores upon which the original conclusions were based.
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Affiliation(s)
| | - Kent G. Golic
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
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6
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Baker NE, Montagna C. Reducing the aneuploid cell burden - cell competition and the ribosome connection. Dis Model Mech 2022; 15:dmm049673. [PMID: 36444717 PMCID: PMC10621665 DOI: 10.1242/dmm.049673] [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] [Indexed: 12/03/2022] Open
Abstract
Aneuploidy, the gain or loss of chromosomes, is the cause of birth defects and miscarriage and is almost ubiquitous in cancer cells. Mosaic aneuploidy causes cancer predisposition, as well as age-related disorders. Despite the cell-intrinsic mechanisms that prevent aneuploidy, sporadic aneuploid cells do arise in otherwise normal tissues. These aneuploid cells can differ from normal cells in the copy number of specific dose-sensitive genes, and may also experience proteotoxic stress associated with mismatched expression levels of many proteins. These differences may mark aneuploid cells for recognition and elimination. The ribosomal protein gene dose in aneuploid cells could be important because, in Drosophila, haploinsufficiency for these genes leads to elimination by the process of cell competition. Constitutive haploinsufficiency for human ribosomal protein genes causes Diamond Blackfan anemia, but it is not yet known whether ribosomal protein gene dose contributes to aneuploid cell elimination in mammals. In this Review, we discuss whether cell competition on the basis of ribosomal protein gene dose is a tumor suppressor mechanism, reducing the accumulation of aneuploid cells. We also discuss how this might relate to the tumor suppressor function of p53 and the p53-mediated elimination of aneuploid cells from murine embryos, and how cell competition defects could contribute to the cancer predisposition of Diamond Blackfan anemia.
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Affiliation(s)
- Nicholas E. Baker
- Departments of Genetics, Developmental and Molecular Biology, and Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Cristina Montagna
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, 195 Little Albany Street, New Brunswick, NJ 08901, USA
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7
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Warecki B, Titen SWA, Alam MS, Vega G, Lemseffer N, Hug K, Minden JS, Sullivan W. Wolbachia action in the sperm produces developmentally deferred chromosome segregation defects during the Drosophila mid-blastula transition. eLife 2022; 11:81292. [PMID: 36149408 PMCID: PMC9507124 DOI: 10.7554/elife.81292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 09/09/2022] [Indexed: 11/29/2022] Open
Abstract
Wolbachia, a vertically transmitted endosymbiont infecting many insects, spreads rapidly through uninfected populations by a mechanism known as cytoplasmic incompatibility (CI). In CI, a paternally delivered modification of the sperm leads to chromatin defects and lethality during and after the first mitosis of embryonic development in multiple species. However, whether CI-induced defects in later stage embryos are a consequence of the first division errors or caused by independent defects remains unresolved. To address this question, we focused on ~1/3 of embryos from CI crosses in Drosophila simulans that develop apparently normally through the first and subsequent pre-blastoderm divisions before exhibiting mitotic errors during the mid-blastula transition and gastrulation. We performed single embryo PCR and whole genome sequencing to find a large percentage of these developed CI-derived embryos bypass the first division defect. Using fluorescence in situ hybridization, we find increased chromosome segregation errors in gastrulating CI-derived embryos that had avoided the first division defect. Thus, Wolbachia action in the sperm induces developmentally deferred defects that are not a consequence of the first division errors. Like the immediate defect, the delayed defect is rescued through crosses to infected females. These studies inform current models on the molecular and cellular basis of CI.
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Affiliation(s)
- Brandt Warecki
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Simon William Abraham Titen
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States.,Department of Biology and Chemistry, California State University Monterey Bay, Seaside, United States
| | - Mohammad Shahriyar Alam
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Giovanni Vega
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Nassim Lemseffer
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Karen Hug
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Jonathan S Minden
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, United States
| | - William Sullivan
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
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8
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Baonza A, Tur-Gracia S, Pérez-Aguilera M, Estella C. Regulation and coordination of the different DNA damage responses in Drosophila. Front Cell Dev Biol 2022; 10:993257. [PMID: 36147740 PMCID: PMC9486394 DOI: 10.3389/fcell.2022.993257] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 08/10/2022] [Indexed: 11/17/2022] Open
Abstract
Cells have evolved mechanisms that allow them to respond to DNA damage to preserve genomic integrity and maintain tissue homeostasis. These responses include the activation of the cell cycle checkpoints and the repair mechanisms or the induction of apoptosis that eventually will eliminate damaged cells. These “life” vs. “death” decisions differ depending on the cell type, stages of development, and the proliferation status of the cell. The apoptotic response after DNA damage is of special interest as defects in its induction could contribute to tumorigenesis or the resistance of cancer cells to therapeutic agents such as radiotherapy. Multiples studies have elucidated the molecular mechanisms that mediate the activation of the DNA damage response pathway (DDR) and specifically the role of p53. However, much less is known about how the different cellular responses such as cell proliferation control and apoptosis are coordinated to maintain tissue homeostasis. Another interesting question is how the differential apoptotic response to DNA damage is regulated in distinct cell types. The use of Drosophila melanogaster as a model organism has been fundamental to understand the molecular and cellular mechanisms triggered by genotoxic stress. Here, we review the current knowledge regarding the cellular responses to ionizing radiation as the cause of DNA damage with special attention to apoptosis in Drosophila: how these responses are regulated and coordinated in different cellular contexts and in different tissues. The existence of intrinsic mechanisms that might attenuate the apoptotic pathway in response to this sort of DNA damage may well be informative for the differences in the clinical responsiveness of tumor cells after radiation therapy.
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9
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Villela D, Mazzonetto PC, Migliavacca MP, Perrone E, Guida G, Milanezi MFG, Jorge AAL, Ribeiro-Bicudo LA, Kok F, Campagnari F, de Rosso-Giuliani L, da Costa SS, Vianna-Morgante AM, Pearson PL, Krepischi ACV, Rosenberg C. Congenital chromoanagenesis in the routine postnatal chromosomal microarray analyses. Am J Med Genet A 2021; 185:2335-2344. [PMID: 33988290 DOI: 10.1002/ajmg.a.62237] [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: 09/28/2020] [Revised: 02/19/2021] [Accepted: 02/26/2021] [Indexed: 11/07/2022]
Abstract
Chromosomal microarray analyses (CMA) have greatly increased both the yield and diagnostic accuracy of postnatal analysis; it has been used as a first-tier cytogenetic test in patients with intellectual disability, autism spectrum disorder, and multiple congenital abnormalities. During the last 15 years, we performed CMA in approximately 8,000 patients with neurodevelopmental and/or congenital disorders, of which 13 (0.16%) genetically catastrophic complex chromosomal rearrangements were identified. These ultrarare rearrangements showed clustering of breakpoints, characteristic of chromoanagenesis events. Al1 13 complex events display underlying formation mechanisms, originating either by a synchronization of the shattering of clustered chromosome regions in which regional asynchrony of DNA replication may be one of the main causes of disruption. We provide an overview of the copy number profiling in these patients. Although several previous studies have suggested that chromoanagenesis is often a genetic disease source in postnatal diagnostic screening, due to either the challenge of clinical interpretation of these complex rearrangements or the limitation of microarray resolution relative to the small size and complexity of chromogenic induced chromosome abnormalities, bringing further attention and to study its occurrence in the clinical setting is extremely important.
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Affiliation(s)
- Darine Villela
- The Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil.,GeneOne, DASA, Brazil
| | | | | | - Eduardo Perrone
- GeneOne, DASA, Brazil.,Department of Clinical Genetics, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | | | | | - Alexander A L Jorge
- Genetic Endocrinology Unit, Laboratory of Cellular and Molecular Endocrinology LIM25, Division of Endocrinology and Metabology, Clinical Hospital of University of São Paulo Medical School (FMUSP), São Paulo, Brazil
| | | | | | | | - Liane de Rosso-Giuliani
- University Hospital Maria Aparecida Pedrossian, Federal University of Mato Grosso Do Sul (HUMAP-UFMS), Campo Grande, Brazil
| | - Silvia Souza da Costa
- The Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil
| | - Angela M Vianna-Morgante
- The Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil
| | - Peter L Pearson
- The Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil
| | - Ana C V Krepischi
- The Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil
| | - Carla Rosenberg
- The Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil.,GeneOne, DASA, Brazil
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10
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Ji Z, Chuen J, Kiparaki M, Baker N. Cell competition removes segmental aneuploid cells from Drosophila imaginal disc-derived tissues based on ribosomal protein gene dose. eLife 2021; 10:61172. [PMID: 33847264 PMCID: PMC8043752 DOI: 10.7554/elife.61172] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 03/08/2021] [Indexed: 12/22/2022] Open
Abstract
Aneuploidy causes birth defects and miscarriages, occurs in nearly all cancers and is a hallmark of aging. Individual aneuploid cells can be eliminated from developing tissues by unknown mechanisms. Cells with ribosomal protein (Rp) gene mutations are also eliminated, by cell competition with normal cells. Because Rp genes are spread across the genome, their copy number is a potential marker for aneuploidy. We found that elimination of imaginal disc cells with irradiation-induced genome damage often required cell competition genes. Segmentally aneuploid cells derived from targeted chromosome excisions were eliminated by the RpS12-Xrp1 cell competition pathway if they differed from neighboring cells in Rp gene dose, whereas cells with normal doses of the Rp and eIF2γ genes survived and differentiated adult tissues. Thus, cell competition, triggered by differences in Rp gene dose between cells, is a significant mechanism for the elimination of aneuploid somatic cells, likely to contribute to preventing cancer. Aneuploid cells emerge when cellular division goes awry and a cell ends up with the wrong number of chromosomes, the tiny genetic structures carrying the instructions that control life’s processes. Aneuploidy can lead to fatal conditions during development, and to cancer in an adult organism. A safety mechanism may exist that helps the body to detect and remove these cells. Yet, exactly this happens is still poorly understood: in particular, it is unclear how cells manage to ‘count’ their chromosomes. One way they could do so is through the ribosomes, the molecular ‘factories’ that create the building blocks required for life. In a cell, every chromosome carries genes that code for the proteins (known as Rps) forming ribosomes. Aneuploidy will alter the number of Rp genes, and in turn the amount and type of Rps the cell produces, so that ribosomes and the genes for Rps could act as a ‘readout’ of aneuploidy. Ji et al set out to test this theory in fruit flies. The first experiment used a genetic manipulation technique called site-specific recombination to remove parts of chromosomes from cells in the developing eye and wing. Cells which retained all their Rp genes survived, while those that were missing some usually died – but only when the surrounding cells were normal. In this situation, healthy cells eliminated their damaged neighbours through a process known as cell competition. A second experiment, using radiation as an alternative method of damaging chromosomes, also gave similar results. The work by Ji et al. reveals how the body can detect and eliminate aneuploid cells, potentially before they can cause harm. If the same mechanism applies in humans, boosting cell competition may, one day, helps to combat diseases like cancer.
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Affiliation(s)
- Zhejun Ji
- Department of Genetics, Albert Einstein College of Medicine, Bronx, United States
| | - Jacky Chuen
- Department of Genetics, Albert Einstein College of Medicine, Bronx, United States
| | - Marianthi Kiparaki
- Department of Genetics, Albert Einstein College of Medicine, Bronx, United States
| | - Nicholas Baker
- Department of Genetics, Albert Einstein College of Medicine, Bronx, United States
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11
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Warecki B, Sullivan W. Mechanisms driving acentric chromosome transmission. Chromosome Res 2020; 28:229-246. [PMID: 32712740 DOI: 10.1007/s10577-020-09636-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 07/16/2020] [Accepted: 07/19/2020] [Indexed: 02/07/2023]
Abstract
The kinetochore-microtubule association is a core, conserved event that drives chromosome transmission during mitosis. Failure to establish this association on even a single chromosome results in aneuploidy leading to cell death or the development of cancer. However, although many chromosomes lacking centromeres, termed acentrics, fail to segregate, studies in a number of systems reveal robust alternative mechanisms that can drive segregation and successful poleward transport of acentrics. In contrast to the canonical mechanism that relies on end-on microtubule attachments to kinetochores, mechanisms of acentric transmission largely fall into three categories: direct attachments to other chromosomes, kinetochore-independent lateral attachments to microtubules, and long-range tether-based attachments. Here, we review these "non-canonical" methods of acentric chromosome transmission. Just as the discovery and exploration of cell cycle checkpoints provided insight into both the origins of cancer and new therapies, identifying mechanisms and structures specifically involved in acentric segregation may have a significant impact on basic and applied cancer research.
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Affiliation(s)
- Brandt Warecki
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA, USA
| | - William Sullivan
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA, USA.
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12
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Site-Specific Recombination with Inverted Target Sites: A Cautionary Tale of Dicentric and Acentric Chromosomes. Genetics 2020; 215:923-930. [PMID: 32586890 DOI: 10.1534/genetics.120.303394] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 06/22/2020] [Indexed: 11/18/2022] Open
Abstract
Site-specific recombinases are widely used tools for analysis of genetics, development, and cell biology, and many schemes have been devised to alter gene expression by recombinase-mediated DNA rearrangements. Because the FRT and lox target sites for the commonly used FLP and Cre recombinases are asymmetrical, and must pair in the same direction to recombine, construct design must take into account orientation of the target sites. Both direct and inverted configurations have been used. However, the outcome of recombination between target sites on sister chromatids is frequently overlooked. This is especially consequential with inverted target sites, where exchange between oppositely oriented target sites on sisters will produce dicentric and acentric chromosomes. By using constructs that have inverted target sites in Drosophila melanogaster and in mice, we show here that dicentric chromosomes are produced in the presence of recombinase, and that the frequency of this event is quite high. The negative effects on cell viability and behavior can be significant, and should be considered when using such constructs.
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13
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Wang Y, Wang JN, Chen XZ, Hu QX, Liu QQ, Wu G. Heat stress-induced expression of Px-pdrg and Px-aspp2 in insecticide-resistant and -susceptible Plutella xylostella. BULLETIN OF ENTOMOLOGICAL RESEARCH 2020; 110:177-184. [PMID: 31559929 DOI: 10.1017/s0007485319000543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
p53, DNA damage regulated gene (PDRG) and apoptosis-stimulating p53 protein 2 (ASPP2) are p53-related genes which can promote apoptosis. The full-length cDNA sequence of the Px-pdrg and Px-aspp2 genes were characterized and their mRNA expression dynamics under heat stress were studied in diamondback moth (DBM) Plutella xylostella collected from Fuzhou, China. The full-length cDNA of Px-pdrg and Px-aspp2 spans 721 and 4201 bp, containing 395 and 3216 bp of the open reading frame, which encode a putative protein comprising 130 and 1072 amino acids with a calculated molecular weight of 14.58 and 118.91 kDa, respectively. As compared to 25°C, both Px-pdrg and Px-aspp2 were upregulated in chlorpyrifos-resistant (Rc) and -susceptible (Sm) strains of DBM adults and pupae under heat stress. In addition, Rc DBM showed a significantly higher expression level of Px-pdrg and Px-aspp2 in contrast to Sm DBM. The results indicate that high temperature can significantly promote apoptosis process, especially in Rc-DBM. Significant fitness cost in Rc-DBM might be associated with drastically higher transcript abundance of Px-pdrg and Px-aspp2 under the heat stress.
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Affiliation(s)
- Yu Wang
- Key Laboratory of Biopesticide and Chemical Biology (Ministry of Education), Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jing Nan Wang
- Key Laboratory of Biopesticide and Chemical Biology (Ministry of Education), Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xue Zhun Chen
- Key Laboratory of Biopesticide and Chemical Biology (Ministry of Education), Fujian Agriculture and Forestry University, Fuzhou, China
| | - Qi Xing Hu
- Key Laboratory of Biopesticide and Chemical Biology (Ministry of Education), Fujian Agriculture and Forestry University, Fuzhou, China
| | - Qi Qing Liu
- Key Laboratory of Biopesticide and Chemical Biology (Ministry of Education), Fujian Agriculture and Forestry University, Fuzhou, China
| | - Gang Wu
- Key Laboratory of Biopesticide and Chemical Biology (Ministry of Education), Fujian Agriculture and Forestry University, Fuzhou, China
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14
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Abstract
The tumour microenvironment plays a critical role in determining tumour fate. Within that environment, and indeed throughout epithelial tissues, cells experience competition with their neighbours, with those less fit being eliminated by fitter adjacent cells. Herein we discuss evidence suggesting that mutations in cancer cells may be selected for their ability to exploit cell competition to kill neighbouring host cells, thereby facilitating tumour expansion. In some instances, cell competition may help host tissues to defend against cancer, by removing neoplastic and aneuploid cells. Cancer risk factors, such as high-sugar or high-fat diet and inflammation, impact cell competition-based host defences, suggesting that their effect on tumour risk may in part be accounted for by their influence on cell competition. We propose that interventions aimed at modifying the strength and direction of cell competition could induce cancer cell killing and form the basis for novel anticancer therapies.
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Affiliation(s)
- Medhavi Vishwakarma
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - Eugenia Piddini
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK.
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15
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Pillon MC, Lo YH, Stanley RE. IT'S 2 for the price of 1: Multifaceted ITS2 processing machines in RNA and DNA maintenance. DNA Repair (Amst) 2019; 81:102653. [PMID: 31324529 PMCID: PMC6764878 DOI: 10.1016/j.dnarep.2019.102653] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cells utilize sophisticated RNA processing machines to ensure the quality of RNA. Many RNA processing machines have been further implicated in regulating the DNA damage response signifying a strong link between RNA processing and genome maintenance. One of the most intricate and highly regulated RNA processing pathways is the processing of the precursor ribosomal RNA (pre-rRNA), which is paramount for the production of ribosomes. Removal of the Internal Transcribed Spacer 2 (ITS2), located between the 5.8S and 25S rRNA, is one of the most complex steps of ribosome assembly. Processing of the ITS2 is initiated by the newly discovered endoribonuclease Las1, which cleaves at the C2 site within the ITS2, generating products that are further processed by the polynucleotide kinase Grc3, the 5'→3' exonuclease Rat1, and the 3'→5' RNA exosome complex. In addition to their defined roles in ITS2 processing, these critical cellular machines participate in other stages of ribosome assembly, turnover of numerous cellular RNAs, and genome maintenance. Here we summarize recent work defining the molecular mechanisms of ITS2 processing by these essential RNA processing machines and highlight their emerging roles in transcription termination, heterochromatin function, telomere maintenance, and DNA repair.
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Affiliation(s)
- Monica C Pillon
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, 111 T. W. Alexander Drive, Research Triangle Park, NC 27709, USA
| | - Yu-Hua Lo
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, 111 T. W. Alexander Drive, Research Triangle Park, NC 27709, USA
| | - Robin E Stanley
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, 111 T. W. Alexander Drive, Research Triangle Park, NC 27709, USA.
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16
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Bhandari J, Karg T, Golic KG. Homolog-Dependent Repair Following Dicentric Chromosome Breakage in Drosophila melanogaster. Genetics 2019; 212:615-630. [PMID: 31053594 PMCID: PMC6614899 DOI: 10.1534/genetics.119.302247] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 04/29/2019] [Indexed: 12/11/2022] Open
Abstract
Double-strand DNA breaks are repaired by one of several mechanisms that rejoin two broken ends. However, cells are challenged when asked to repair a single broken end and respond by: (1) inducing programmed cell death; (2) healing the broken end by constructing a new telomere; (3) adapting to the broken end and resuming the mitotic cycle without repair; and (4) using information from the sister chromatid or homologous chromosome to restore a normal chromosome terminus. During one form of homolog-dependent repair in yeast, termed break-induced replication (BIR), a template chromosome can be copied for hundreds of kilobases. BIR efficiency depends on Pif1 helicase and Pol32, a nonessential subunit of DNA polymerase δ. To date, there is little evidence that BIR can be used for extensive chromosome repair in higher eukaryotes. We report that a dicentric chromosome broken in mitosis in the male germline of Drosophila melanogaster is usually repaired by healing, but can also be repaired in a homolog-dependent fashion, restoring at least 1.3 Mb of terminal sequence information. This mode of repair is significantly reduced in pif1 and pol32 mutants. Formally, the repaired chromosomes are recombinants. However, the absence of reciprocal recombinants and the dependence on Pif1 and Pol32 strongly support the hypothesis that BIR is the mechanism for restoration of the chromosome terminus. In contrast to yeast, pif1 mutants in Drosophila exhibit a reduced rate of chromosome healing, likely owing to fundamental differences in telomeres between these organisms.
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Affiliation(s)
- Jayaram Bhandari
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
| | - Travis Karg
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
| | - Kent G Golic
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
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17
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Kordyukova MY, Kalmykova AI. Nature and Functions of Telomeric Transcripts. BIOCHEMISTRY (MOSCOW) 2019; 84:137-146. [DOI: 10.1134/s0006297919020044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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18
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Zhou L. P53 and Apoptosis in the Drosophila Model. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1167:105-112. [PMID: 31520351 DOI: 10.1007/978-3-030-23629-8_6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Human P53 (HsP53) is the most frequently mutated gene associated with cancers. Despite heightened research interest over the last four decades, a clear picture of how wild type HsP53 functions as the guardian against malignant transformation remains elusive. Studying the ortholog of P53 in the genetic model organism Drosophila melanogaster (DmP53) has revealed many interesting insights. This chapter focuses on recent findings that have shed light on how DmP53 -mediated apoptosis plays an important role in maintaining genome integrity, and how the immediate output of activated DmP53 is determined by the epigenetic landscape of individual cells.
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Affiliation(s)
- Lei Zhou
- Department of Molecular Genetics and Microbiology, UF Health Cancer Center, College of Medicine, University of Florida, Gainesville, FL, USA.
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19
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Baillon L, Germani F, Rockel C, Hilchenbach J, Basler K. Xrp1 is a transcription factor required for cell competition-driven elimination of loser cells. Sci Rep 2018; 8:17712. [PMID: 30531963 PMCID: PMC6286310 DOI: 10.1038/s41598-018-36277-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 11/14/2018] [Indexed: 11/16/2022] Open
Abstract
The elimination of unfit cells from a tissue is a process known in Drosophila and mammals as cell competition. In a well-studied paradigm “loser” cells that are heterozygous mutant for a haploinsufficient ribosomal protein gene are eliminated from developing tissues via apoptosis when surrounded by fitter wild-type cells, referred to as “winner” cells. However, the mechanisms underlying the induction of this phenomenon are not fully understood. Here we report that a CCAAT-Enhancer-Binding Protein (C/EBP), Xrp1, which is known to help maintaining genomic stability after genotoxic stress, is necessary for the elimination of loser clones in cell competition. In loser cells, Xrp1 is transcriptionally upregulated by an autoregulatory loop and is able to trigger apoptosis - driving cell elimination. We further show that Xrp1 acts in the nucleus to regulate the transcription of several genes that have been previously involved in cell competition. We therefore speculate that Xrp1 might play a fundamental role as a molecular caretaker of the genomic integrity of tissues.
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Affiliation(s)
- Ludovic Baillon
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Federico Germani
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland.
| | - Claudia Rockel
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Jochen Hilchenbach
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Konrad Basler
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland.
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20
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Hanlon SL, Miller DE, Eche S, Hawley RS. Origin, Composition, and Structure of the Supernumerary B Chromosome of Drosophila melanogaster. Genetics 2018; 210:1197-1212. [PMID: 30249684 PMCID: PMC6283169 DOI: 10.1534/genetics.118.301478] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 09/23/2018] [Indexed: 01/18/2023] Open
Abstract
The number of chromosomes carried by an individual species is one of its defining characteristics. Some species, however, can also carry supernumerary chromosomes referred to as B chromosomes. B chromosomes were recently identified in a laboratory stock of Drosophila melanogaster-an established model organism with a wealth of genetic and genomic resources-enabling us to subject them to extensive molecular analysis. We isolated the B chromosomes by pulsed-field gel electrophoresis and determined their composition through next-generation sequencing. Although these B chromosomes carry no known euchromatic sequence, they are rich in transposable elements and long arrays of short nucleotide repeats, the most abundant being the uncharacterized AAGAT satellite repeat. Fluorescent in situ hybridization on metaphase chromosome spreads revealed this repeat is located on chromosome 4, strongly suggesting the origin of the B chromosomes is chromosome 4 Cytological and quantitative comparisons of signal intensity between chromosome 4 and the B chromosomes supports the hypothesis that the structure of the B chromosome is an isochromosome. We also report the identification of a new B chromosome variant in a related laboratory stock. This B chromosome has a similar repeat signature as the original but is smaller and much less prevalent. We examined additional stocks with similar genotypes and did not find B chromosomes, but did find these stocks lacked the AAGAT satellite repeat. Our molecular characterization of D. melanogaster B chromosomes is the first step toward understanding how supernumerary chromosomes arise from essential chromosomes and what may be necessary for their stable inheritance.
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Affiliation(s)
- Stacey L Hanlon
- Stowers Institute for Medical Research, Kansas City, Missouri 64110
| | - Danny E Miller
- Department of Pediatrics, Seattle Children's Hospital, University of Washington, Seattle, Washington 98105
| | - Salam Eche
- Stowers Institute for Medical Research, Kansas City, Missouri 64110
| | - R Scott Hawley
- Stowers Institute for Medical Research, Kansas City, Missouri 64110
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas 66160
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21
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Bayer FE, Zimmermann M, Preiss A, Nagel AC. Overexpression of the Drosophila ATR homologous checkpoint kinase Mei-41 induces a G2/M checkpoint in Drosophila imaginal tissue. Hereditas 2018; 155:27. [PMID: 30202398 PMCID: PMC6125995 DOI: 10.1186/s41065-018-0066-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 08/28/2018] [Indexed: 11/25/2022] Open
Abstract
Background DNA damage generally results in the activation of ATM/ATR kinases and the downstream checkpoint kinases Chk1/Chk2. In Drosophila melanogaster, the ATR homologue meiotic 41 (mei-41) is pivotal to DNA damage repair and cell cycle checkpoint signalling. Although various mei-41 mutant alleles have been analyzed in the past, no gain-of-function allele is yet available. To fill this gap, we have generated transgenic flies allowing temporal and tissue-specific induction of mei-41. Results Overexpression of mei-41 in wing and eye anlagen affects proliferation and a G2/M checkpoint even in the absence of genomic stress. Similar consequences were observed following the overexpression of the downstream kinase Grapes (Grp) but not of Loki (Lok), encoding the respective Drosophila Chk1 and Chk2 homologues, in agreement with their previously reported activities. Moreover, we show that irradiation induced cell cycle arrest was prolonged in the presence of ectopic mei-41 expression. Similar to irradiation stress, mei-41 triggered the occurrence of a slower migrating form of Grp, implying specific phosphorylation of Grp in response to either signal. Using a p53R-GFP biosensor, we further show that overexpression of mei-41 was sufficient to elicit a robust p53 activation in vivo. Conclusion We conclude that overexpression of the Drosophila ATR homologue mei-41 elicits an effectual DNA damage response irrespective of irradiation. Electronic supplementary material The online version of this article (10.1186/s41065-018-0066-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Fabienne E Bayer
- Universität Hohenheim, Institut für Genetik, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Mirjam Zimmermann
- Universität Hohenheim, Institut für Genetik, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Anette Preiss
- Universität Hohenheim, Institut für Genetik, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Anja C Nagel
- Universität Hohenheim, Institut für Genetik, Garbenstr. 30, 70599 Stuttgart, Germany
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22
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Micronuclei Formation Is Prevented by Aurora B-Mediated Exclusion of HP1a from Late-Segregating Chromatin in Drosophila. Genetics 2018; 210:171-187. [PMID: 29986897 PMCID: PMC6116970 DOI: 10.1534/genetics.118.301031] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 07/03/2018] [Indexed: 11/18/2022] Open
Abstract
While it is known that micronuclei pose a serious risk to genomic integrity by undergoing chromothripsis, mechanisms preventing micronucleus formation remain poorly understood. Here, we investigate how late-segregating acentric chromosomes that would otherwise form micronuclei instead reintegrate into daughter nuclei by passing through Aurora B kinase-dependent channels in the nuclear envelope of Drosophila melanogaster neuroblasts. We find that localized concentrations of Aurora B preferentially phosphorylate H3(S10) on acentrics and their associated DNA tethers. This phosphorylation event prevents HP1a from associating with heterochromatin and results in localized inhibition of nuclear envelope reassembly on endonuclease- and X-irradiation-induced acentrics, promoting channel formation. Finally, we find that HP1a also specifies initiation sites of nuclear envelope reassembly on undamaged chromatin. Taken together, these results demonstrate that Aurora B-mediated regulation of HP1a-chromatin interaction plays a key role in maintaining genome integrity by locally preventing nuclear envelope assembly and facilitating the incorporation of late-segregating acentrics into daughter nuclei.
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23
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Caridi PC, Delabaere L, Zapotoczny G, Chiolo I. And yet, it moves: nuclear and chromatin dynamics of a heterochromatic double-strand break. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0291. [PMID: 28847828 PMCID: PMC5577469 DOI: 10.1098/rstb.2016.0291] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/07/2017] [Indexed: 12/15/2022] Open
Abstract
Heterochromatin is mostly composed of repeated DNA sequences prone to aberrant recombination. How cells maintain the stability of these sequences during double-strand break (DSB) repair has been a long-standing mystery. Studies in Drosophila cells revealed that faithful homologous recombination repair of heterochromatic DSBs relies on the striking relocalization of repair sites to the nuclear periphery before Rad51 recruitment and repair progression. Here, we summarize our current understanding of this response, including the molecular mechanisms involved, and conserved pathways in mammalian cells. We will highlight important similarities with pathways identified in budding yeast for repair of other types of repeated sequences, including rDNA and short telomeres. We will also discuss the emerging role of chromatin composition and regulation in heterochromatin repair progression. Together, these discoveries challenged previous assumptions that repair sites are substantially static in multicellular eukaryotes, that heterochromatin is largely inert in the presence of DSBs, and that silencing and compaction in this domain are obstacles to repair. This article is part of the themed issue ‘Chromatin modifiers and remodellers in DNA repair and signalling’.
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Affiliation(s)
- P Christopher Caridi
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
| | - Laetitia Delabaere
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
| | - Grzegorz Zapotoczny
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
| | - Irene Chiolo
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
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24
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Telomeres: Implications for Cancer Development. Int J Mol Sci 2018; 19:ijms19010294. [PMID: 29351238 PMCID: PMC5796239 DOI: 10.3390/ijms19010294] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 01/12/2018] [Accepted: 01/16/2018] [Indexed: 12/31/2022] Open
Abstract
Telomeres facilitate the protection of natural ends of chromosomes from constitutive exposure to the DNA damage response (DDR). This is most likely achieved by a lariat structure that hides the linear telomeric DNA through protein-protein and protein-DNA interactions. The telomere shortening associated with DNA replication in the absence of a compensatory mechanism culminates in unmasked telomeres. Then, the subsequent activation of the DDR will define the fate of cells according to the functionality of cell cycle checkpoints. Dysfunctional telomeres can suppress cancer development by engaging replicative senescence or apoptotic pathways, but they can also promote tumour initiation. Studies in telomere dynamics and karyotype analysis underpin telomere crisis as a key event driving genomic instability. Significant attainment of telomerase or alternative lengthening of telomeres (ALT)-pathway to maintain telomere length may be permissive and required for clonal evolution of genomically-unstable cells during progression to malignancy. We summarise current knowledge of the role of telomeres in the maintenance of chromosomal stability and carcinogenesis.
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25
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Marcozzi A, Pellestor F, Kloosterman WP. The Genomic Characteristics and Origin of Chromothripsis. Methods Mol Biol 2018; 1769:3-19. [PMID: 29564814 DOI: 10.1007/978-1-4939-7780-2_1] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In 2011 a phenomenon involving complex chromosomal rearrangements was discovered in cancer genomes. This phenomenon has been termed chromothripsis, on the basis of its chromosomal hallmarks, which point to an underlying process involving chromosome (chromo) shattering (thripsis). The prevailing hypothesis of cancer genome evolution as a gradual process of mutation and selection was challenged by the discovery of chromothripsis, because its patterns of chromosome rearrangement rather indicated an one-off catastrophic burst of genome rearrangement. The initial discovery of chromothripsis has led to many more examples of chromothripsis both in cancer genomes as well as in patients with congenital diseases and in the genomes of healthy individuals. Since then, a burning topic has been the study of the molecular mechanism that leads to chromothripsis. Cumulating evidence has shown that chromothripsis may result from lagging chromosomes encapsulated in micronuclei, as well as from telomere fusions followed by chromosome bridge formation. In this chapter, we will outline the genomic characteristics of chromothripsis, and we present genomic methodologies that enable the detection of chromothripsis. Furthermore, we will give an overview of recent insights into the mechanisms underlying chromothripsis.
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Affiliation(s)
- Alessio Marcozzi
- Division of Biomedical Genetics, Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Franck Pellestor
- Laboratory of Chromosomal Genetics, Department of Medical Genetics, Arnaud de Villeneuve Hospital, Montpellier CHRU, Montpellier, France.,INSERM Unit Plasticity of the Genome and Aging, Institute of Functional Genomics, Montpellier, France
| | - Wigard P Kloosterman
- Division of Biomedical Genetics, Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
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26
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Chromosome Healing Is Promoted by the Telomere Cap Component Hiphop in Drosophila. Genetics 2017; 207:949-959. [PMID: 28942425 DOI: 10.1534/genetics.117.300317] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 09/21/2017] [Indexed: 11/18/2022] Open
Abstract
The addition of a new telomere onto a chromosome break, a process termed healing, has been studied extensively in organisms that utilize telomerase to maintain their telomeres. In comparison, relatively little is known about how new telomeres are constructed on broken chromosomes in organisms that do not use telomerase. Chromosome healing was studied in somatic and germline cells of Drosophila melanogaster, a nontelomerase species. We observed, for the first time, that broken chromosomes can be healed in somatic cells. In addition, overexpression of the telomere cap component Hiphop increased the survival of somatic cells with broken chromosomes, while the cap component HP1 did not, and overexpression of the cap protein HOAP decreased their survival. In the male germline, Hiphop overexpression greatly increased the transmission of healed chromosomes. These results indicate that Hiphop can stimulate healing of a chromosome break. We suggest that this reflects a unique function of Hiphop: it is capable of seeding formation of a new telomeric cap on a chromosome end that lacks a telomere.
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27
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Baker NE. Mechanisms of cell competition emerging from Drosophila studies. Curr Opin Cell Biol 2017; 48:40-46. [PMID: 28600967 DOI: 10.1016/j.ceb.2017.05.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 05/15/2017] [Accepted: 05/16/2017] [Indexed: 10/19/2022]
Abstract
Cell competition was described in Drosophila as the loss from mosaic tissues of otherwise viable cells heterozygous for Ribosomal protein mutations ('Minutes'). Cell competition has now been described to occur between multiple other genotypes, such as cells differing in myc expression levels, or mutated for neoplastic tumor suppressors. Recent studies implicate innate immunity components, and possibly mechanical stress, compression and cell intercalation as a consequence of differential growth rates in competitive cell death. Competition to eliminate pre-neoplastic tumors makes use of signals and receptors also used in patterning the nervous system including Slit/Robo2 and Sas/PTP10D to recognize and extrude clones of mutant cells, at least where local epithelial cyto-architecture is favorable. Cell competition facilitates expansion of Drosophila tumors through host tissue, and in normal development may promote developmental robustness and longevity by selecting for optimal progenitor cells.
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Affiliation(s)
- Nicholas E Baker
- Department of Genetics, Department of Developmental and Molecular Biology, Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, United States.
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28
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Karg T, Elting MW, Vicars H, Dumont S, Sullivan W. The chromokinesin Klp3a and microtubules facilitate acentric chromosome segregation. J Cell Biol 2017; 216:1597-1608. [PMID: 28500183 PMCID: PMC5461011 DOI: 10.1083/jcb.201604079] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 02/03/2017] [Accepted: 04/07/2017] [Indexed: 11/23/2022] Open
Abstract
Although chromosome fragments lacking a centromere would be expected to show severe defects in their segregation during anaphase, they do exhibit poleward movement by an unclear mechanism. Karg et al. now show how microtubules and the chromokinesin Klp3a can work together to successfully segregate chromosome fragments to daughter nuclei. Although poleward segregation of acentric chromosomes is well documented, the underlying mechanisms remain poorly understood. Here, we demonstrate that microtubules play a key role in poleward movement of acentric chromosome fragments generated in Drosophila melanogaster neuroblasts. Acentrics segregate with either telomeres leading or lagging in equal frequency and are preferentially associated with peripheral bundled microtubules. In addition, laser ablation studies demonstrate that segregating acentrics are mechanically associated with microtubules. Finally, we show that successful acentric segregation requires the chromokinesin Klp3a. Reduced Klp3a function results in disorganized interpolar microtubules and shortened spindles. Normally, acentric poleward segregation occurs at the periphery of the spindle in association with interpolar microtubules. In klp3a mutants, acentrics fail to localize and segregate along the peripheral interpolar microtubules and are abnormally positioned in the spindle interior. These studies demonstrate an unsuspected role for interpolar microtubules in driving acentric segregation.
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Affiliation(s)
- Travis Karg
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Mary Williard Elting
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143
| | - Hannah Vicars
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Sophie Dumont
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143.,Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94143
| | - William Sullivan
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
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29
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McNulty SM, Sullivan BA. Centromere Silencing Mechanisms. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2017; 56:233-255. [PMID: 28840240 DOI: 10.1007/978-3-319-58592-5_10] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Centromere function is essential for genome stability and chromosome inheritance. Typically, each chromosome has a single locus that consistently serves as the site of centromere formation and kinetochore assembly. Decades of research have defined the DNA sequence and protein components of functional centromeres, and the interdependencies of specific protein complexes for proper centromere assembly. Less is known about how centromeres are disassembled or functionally silenced. Centromere silencing, or inactivation, is particularly relevant in the cases of dicentric chromosomes that occur via genome rearrangements that place two centromeres on the same chromosome. Dicentrics are usually unstable unless one centromere is inactivated, thereby allowing the structurally dicentric chromosome to behave like one of the monocentric, endogenous chromosomes. The molecular basis for centromere inactivation is not well understood, although studies in model organisms and in humans suggest that both genomic and epigenetic mechanisms are involved. In this chapter, we review recent studies using synthetic chromosomes and engineered or induced dicentrics from various organisms to define the molecular processes that are involved in the complex process of centromere inactivation.
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Affiliation(s)
- Shannon M McNulty
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, DUMC 3054, Durham, NC, 27710, USA.,Division of Human Genetics, Duke University Medical Center, DUMC 3054, Durham, NC, 27710, USA
| | - Beth A Sullivan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, DUMC 3054, Durham, NC, 27710, USA. .,Division of Human Genetics, Duke University Medical Center, DUMC 3054, Durham, NC, 27710, USA.
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30
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Bretscher HS, Fox DT. Proliferation of Double-Strand Break-Resistant Polyploid Cells Requires Drosophila FANCD2. Dev Cell 2016; 37:444-57. [PMID: 27270041 PMCID: PMC4901310 DOI: 10.1016/j.devcel.2016.05.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 02/22/2016] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Conserved DNA-damage responses (DDRs) sense genome damage and prevent mitosis of broken chromosomes. How cells lacking DDRs cope with broken chromosomes during mitosis is poorly understood. DDRs are frequently inactivated in cells with extra genomes (polyploidy), suggesting that study of polyploidy can reveal how cells with impaired DDRs/genome damage continue dividing. Here, we show that continued division and normal organ development occurs in polyploid, DDR-impaired Drosophila papillar cells. As papillar cells become polyploid, they naturally accumulate broken acentric chromosomes but do not apoptose/arrest the cell cycle. To survive mitosis with acentric chromosomes, papillar cells require Fanconi anemia proteins FANCD2 and FANCI, as well as Blm helicase, but not canonical DDR signaling. FANCD2 acts independently of previous S phases to promote alignment and segregation of acentric DNA produced by double-strand breaks, thus avoiding micronuclei and organ malformation. Because polyploidy and impaired DDRs can promote cancer, our findings provide insight into disease-relevant DNA-damage tolerance mechanisms.
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Affiliation(s)
- Heidi S Bretscher
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, DUMC Box 3813, Durham, NC 27710, USA
| | - Donald T Fox
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, DUMC Box 3813, Durham, NC 27710, USA.
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Preferential Breakpoints in the Recovery of Broken Dicentric Chromosomes in Drosophila melanogaster. Genetics 2015; 201:563-72. [PMID: 26294667 DOI: 10.1534/genetics.115.181156] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 08/19/2015] [Indexed: 12/27/2022] Open
Abstract
We designed a system to determine whether dicentric chromosomes in Drosophila melanogaster break at random or at preferred sites. Sister chromatid exchange in a Ring-X chromosome produced dicentric chromosomes with two bridging arms connecting segregating centromeres as cells divide. This double bridge can break in mitosis. A genetic screen recovered chromosomes that were linearized by breakage in the male germline. Because the screen required viability of males with this X chromosome, the breakpoints in each arm of the double bridge must be closely matched to produce a nearly euploid chromosome. We expected that most linear chromosomes would be broken in heterochromatin because there are no vital genes in heterochromatin, and breakpoint distribution would be relatively unconstrained. Surprisingly, approximately half the breakpoints are found in euchromatin, and the breakpoints are clustered in just a few regions of the chromosome that closely match regions identified as intercalary heterochromatin. The results support the Laird hypothesis that intercalary heterochromatin can explain fragile sites in mitotic chromosomes, including fragile X. Opened rings also were recovered after male larvae were exposed to X-rays. This method was much less efficient and produced chromosomes with a strikingly different array of breakpoints, with almost all located in heterochromatin. A series of circularly permuted linear X chromosomes was generated that may be useful for investigating aspects of chromosome behavior, such as crossover distribution and interference in meiosis, or questions of nuclear organization and function.
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Abstract
A veritable explosion of primary research papers within the past 10 years focuses on nucleolar and ribosomal stress, and for good reason: with ribosome biosynthesis consuming ~80% of a cell’s energy, nearly all metabolic and signaling pathways lead ultimately to or from the nucleolus. We begin by describing p53 activation upon nucleolar stress resulting in cell cycle arrest or apoptosis. The significance of this mechanism cannot be understated, as oncologists are now inducing nucleolar stress strategically in cancer cells as a potential anti-cancer therapy. We also summarize the human ribosomopathies, syndromes in which ribosome biogenesis or function are impaired leading to birth defects or bone narrow failures; the perplexing problem in the ribosomopathies is why only certain cells are affected despite the fact that the causative mutation is systemic. We then describe p53-independent nucleolar stress, first in yeast which lacks p53, and then in other model metazoans that lack MDM2, the critical E3 ubiquitin ligase that normally inactivates p53. Do these presumably ancient p53-independent nucleolar stress pathways remain latent in human cells? If they still exist, can we use them to target >50% of known human cancers that lack functional p53?
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Affiliation(s)
- Allison James
- a Department of Biological Sciences; Louisiana State University; Baton Rouge, LA USA
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Russo A, Pacchierotti F, Cimini D, Ganem NJ, Genescà A, Natarajan AT, Pavanello S, Valle G, Degrassi F. Genomic instability: Crossing pathways at the origin of structural and numerical chromosome changes. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2015; 56:563-580. [PMID: 25784636 DOI: 10.1002/em.21945] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 02/02/2015] [Accepted: 02/19/2015] [Indexed: 06/04/2023]
Abstract
Genomic instability leads to a wide spectrum of genetic changes, including single nucleotide mutations, structural chromosome alterations, and numerical chromosome changes. The accepted view on how these events are generated predicts that separate cellular mechanisms and genetic events explain the occurrence of these types of genetic variation. Recently, new findings have shed light on the complexity of the mechanisms leading to structural and numerical chromosome aberrations, their intertwining pathways, and their dynamic evolution, in somatic as well as in germ cells. In this review, we present a critical analysis of these recent discoveries in this area, with the aim to contribute to a deeper knowledge of the molecular networks leading to adverse outcomes in humans following exposure to environmental factors. The review illustrates how several technological advances, including DNA sequencing methods, bioinformatics, and live-cell imaging approaches, have contributed to produce a renewed concept of the mechanisms causing genomic instability. Special attention is also given to the specific pathways causing genomic instability in mammalian germ cells. Remarkably, the same scenario emerged from some pioneering studies published in the 1980s to 1990s, when the evolution of polyploidy, the chromosomal effects of spindle poisons, the fate of micronuclei, were intuitively proposed to share mechanisms and pathways. Thus, an old working hypothesis has eventually found proper validation.
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Affiliation(s)
| | - Francesca Pacchierotti
- Laboratory of Toxicology, Unit of Radiation Biology and Human Health, ENEA CR Casaccia, Rome, Italy
| | - Daniela Cimini
- Department of Biological Sciences and Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia
| | - Neil J Ganem
- Department of Pharmacology, Division of Hematology and Oncology, Boston University School of Medicine, Boston, Massachusetts
| | - Anna Genescà
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | | | - Sofia Pavanello
- Department of Cardiac, Thoracic and Vascular Sciences, Unit of Occupational Medicine, University of Padova, Italy
| | - Giorgio Valle
- Department of Biology, University of Padova, Padova, Italy
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Chakraborty R, Li Y, Zhou L, Golic KG. Corp Regulates P53 in Drosophila melanogaster via a Negative Feedback Loop. PLoS Genet 2015; 11:e1005400. [PMID: 26230084 PMCID: PMC4521751 DOI: 10.1371/journal.pgen.1005400] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Accepted: 06/26/2015] [Indexed: 01/08/2023] Open
Abstract
The tumor suppressor P53 is a critical mediator of the apoptotic response to DNA double-strand breaks through the transcriptional activation of pro-apoptotic genes. This mechanism is evolutionarily conserved from mammals to lower invertebrates, including Drosophila melanogaster. P53 also transcriptionally induces its primary negative regulator, Mdm2, which has not been found in Drosophila. In this study we identified the Drosophila gene companion of reaper (corp) as a gene whose overexpression promotes survival of cells with DNA damage in the soma but reduces their survival in the germline. These disparate effects are shared by p53 mutants, suggesting that Corp may be a negative regulator of P53. Confirming this supposition, we found that corp negatively regulates P53 protein level. It has been previously shown that P53 transcriptionally activates corp; thus, Corp produces a negative feedback loop on P53. We further found that Drosophila Corp shares a protein motif with vertebrate Mdm2 in a region that mediates the Mdm2:P53 physical interaction. In Corp, this motif mediates physical interaction with Drosophila P53. Our findings implicate Corp as a functional analog of vertebrate Mdm2 in flies.
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Affiliation(s)
- Riddhita Chakraborty
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Ying Li
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Lei Zhou
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Kent G. Golic
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
- * E-mail:
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Abstract
Throughout their lifetime, cells may suffer insults that reduce their fitness and disrupt their function, and it is unclear how these potentially harmful cells are managed in adult tissues. We address this question using the adult Drosophila posterior midgut as a model of homeostatic tissue and ribosomal Minute mutations to reduce fitness in groups of cells. We take a quantitative approach combining lineage tracing and biophysical modeling and address how cell competition affects stem cell and tissue population dynamics. We show that healthy cells induce clonal extinction in weak tissues, targeting both stem and differentiated cells for elimination. We also find that competition induces stem cell proliferation and self-renewal in healthy tissue, promoting selective advantage and tissue colonization. Finally, we show that winner cell proliferation is fueled by the JAK-STAT ligand Unpaired-3, produced by Minute−/+ cells in response to chronic JNK stress signaling. In the adult fly gut, wild-type cells outcompete subfit Minute−/+ cells Both stem and differentiated Minute−/+ cells are eliminated by cell competition Cell competition promotes proliferation and self-renewal of normal stem cells The growth of healthy cells is boosted by JAK-STAT signaling
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Zimmermann M, Kugler SJ, Schulz A, Nagel AC. Loss of putzig Activity Results in Apoptosis during Wing Imaginal Development in Drosophila. PLoS One 2015; 10:e0124652. [PMID: 25894556 PMCID: PMC4403878 DOI: 10.1371/journal.pone.0124652] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 03/17/2015] [Indexed: 12/22/2022] Open
Abstract
The Drosophila gene putzig (pzg) encodes a nuclear protein that is an integral component of the Trf2/Dref complex involved in the transcription of proliferation-related genes. Moreover, Pzg is found in a complex together with the nucleosome remodeling factor NURF, where it promotes Notch target gene activation. Here we show that downregulation of pzg activity in the developing wing imaginal discs induces an apoptotic response, accompanied by the induction of the pro-apoptotic gene reaper, repression of Drosophila inhibitor of apoptosis protein accumulation and the activation of the caspases Drice, Caspase3 and Dcp1. As a further consequence ‘Apoptosis induced Proliferation’ (AiP) and ‘Apoptosis induced Apoptosis’ (AiA) are triggered. As expected, the activity of the stress kinase Jun N-terminal kinase (JNK), proposed to mediate both processes, is ectopically induced in response to pzg loss. In addition, the expression of the mitogen wingless (wg) but not of decapentaplegic (dpp) is observed. We present evidence that downregulation of Notch activates Dcp1 caspase and JNK signaling, however, neither induces ectopic wg nor dpp expression. In contrast, the consequences of Dref-RNAi were largely indistinguishable from pzg-RNAi with regard to apoptosis induction. Moreover, overexpression of Dref ameliorated the downregulation of pzg compatible with the notion that the two are required together to maintain cell and tissue homeostasis in Drosophila.
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Affiliation(s)
- Mirjam Zimmermann
- Institute of Genetics, University of Hohenheim, 70599 Stuttgart, Germany
| | - Sabrina J. Kugler
- Institute of Genetics, University of Hohenheim, 70599 Stuttgart, Germany
| | - Adriana Schulz
- Institute of Genetics, University of Hohenheim, 70599 Stuttgart, Germany
| | - Anja C. Nagel
- Institute of Genetics, University of Hohenheim, 70599 Stuttgart, Germany
- * E-mail:
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Apoptotic mechanisms during competition of ribosomal protein mutant cells: roles of the initiator caspases Dronc and Dream/Strica. Cell Death Differ 2015; 22:1300-12. [PMID: 25613379 DOI: 10.1038/cdd.2014.218] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 10/11/2014] [Accepted: 10/30/2014] [Indexed: 12/16/2022] Open
Abstract
Heterozygosity for mutations in ribosomal protein genes frequently leads to a dominant phenotype of retarded growth and small adult bristles in Drosophila (the Minute phenotype). Cells with Minute genotypes are subject to cell competition, characterized by their selective apoptosis and removal in mosaic tissues that contain wild-type cells. Competitive apoptosis was found to depend on the pro-apoptotic reaper, grim and head involution defective genes but was independent of p53. Rp/+ cells are protected by anti-apoptotic baculovirus p35 expression but lacked the usual hallmarks of 'undead' cells. They lacked Dronc activity, and neither expression of dominant-negative Dronc nor dronc knockdown by dsRNA prevented competitive apoptosis, which also continued in dronc null mutant cells or in the absence of the initiator caspases dredd and dream/strica. Only simultaneous knockdown of dronc and dream/strica by dsRNA was sufficient to protect Rp/+ cells from competition. By contrast, Rp/Rp cells were also protected by baculovirus p35, but Rp/Rp death was dronc-dependent, and undead Rp/Rp cells exhibited typical dronc-dependent expression of Wingless. Independence of p53 and unusual dependence on Dream/Strica distinguish competitive cell death from noncompetitive apoptosis of Rp/Rp cells and from many other examples of cell death.
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Titen SWA, Lin HC, Bhandari J, Golic KG. Chk2 and p53 regulate the transmission of healed chromosomes in the Drosophila male germline. PLoS Genet 2014; 10:e1004130. [PMID: 24586185 PMCID: PMC3937212 DOI: 10.1371/journal.pgen.1004130] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 12/04/2013] [Indexed: 01/12/2023] Open
Abstract
When a dicentric chromosome breaks in mitosis, the broken ends cannot be repaired by normal mechanisms that join two broken ends since each end is in a separate daughter cell. However, in the male germline of Drosophila melanogaster, a broken end may be healed by de novo telomere addition. We find that Chk2 (encoded by lok) and P53, major mediators of the DNA damage response, have strong and opposite influences on the transmission of broken-and-healed chromosomes: lok mutants exhibit a large increase in the recovery of healed chromosomes relative to wildtype control males, but p53 mutants show a strong reduction. This contrasts with the soma, where mutations in lok and p53 have the nearly identical effect of allowing survival and proliferation of cells with irreparable DNA damage. Examination of testes revealed a transient depletion of germline cells after dicentric chromosome induction in the wildtype controls, and further showed that P53 is required for the germline to recover. Although lok mutant males transmit healed chromosomes at a high rate, broken chromosome ends can also persist through spermatogonial divisions without healing in lok mutants, giving rise to frequent dicentric bridges in Meiosis II. Cytological and genetic analyses show that spermatid nuclei derived from such meiotic divisions are eliminated during spermiogenesis, resulting in strong meiotic drive. We conclude that the primary responsibility for maintaining genome integrity in the male germline lies with Chk2, and that P53 is required to reconstitute the germline when cells are eliminated owing to unrepaired DNA damage.
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Affiliation(s)
- Simon W. A. Titen
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Ho-Chen Lin
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Jayaram Bhandari
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Kent G. Golic
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
- * E-mail:
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40
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Nuclear dynamics of radiation-induced foci in euchromatin and heterochromatin. Mutat Res 2013; 750:56-66. [PMID: 23958412 DOI: 10.1016/j.mrfmmm.2013.08.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 07/29/2013] [Accepted: 08/01/2013] [Indexed: 02/05/2023]
Abstract
Repair of double strand breaks (DSBs) is essential for cell survival and genome integrity. While much is known about the molecular mechanisms involved in DSB repair and checkpoint activation, the roles of nuclear dynamics of radiation-induced foci (RIF) in DNA repair are just beginning to emerge. Here, we summarize results from recent studies that point to distinct features of these dynamics in two different chromatin environments: heterochromatin and euchromatin. We also discuss how nuclear architecture and chromatin components might control these dynamics, and the need of novel quantification methods for a better description and interpretation of these phenomena. These studies are expected to provide new biomarkers for radiation risk and new strategies for cancer detection and treatment.
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Gonzalez C. Drosophila melanogaster: a model and a tool to investigate malignancy and identify new therapeutics. Nat Rev Cancer 2013; 13:172-83. [PMID: 23388617 DOI: 10.1038/nrc3461] [Citation(s) in RCA: 206] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
For decades, lower-model organisms such as Drosophila melanogaster have often provided the first glimpse into the mechanism of action of human cancer-related proteins, thus making a substantial contribution to elucidating the molecular basis of the disease. More recently, D. melanogaster strains that are engineered to recapitulate key aspects of specific types of human cancer have been paving the way for the future role of this 'workhorse' of biomedical research, helping to further investigate the process of malignancy, and serving as platforms for therapeutic drug discovery.
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Affiliation(s)
- Cayetano Gonzalez
- IRB-Barcelona, c/Baldiri Reixac 10-12, Barcelona, Spain. gonzalez@ irbbarcelona.org
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42
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Ji J, Tang D, Wang K, Wang M, Che L, Li M, Cheng Z. The role of OsCOM1 in homologous chromosome synapsis and recombination in rice meiosis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 72:18-30. [PMID: 22507309 DOI: 10.1111/j.1365-313x.2012.05025.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
COM1/SAE2 is a highly conserved gene from yeast to higher eukaryotes. Its orthologs, known to cooperate with the MRX complex (Mre11/Rad50/Xrs2), are required for meiotic DNA double-strand break (DSB) ends resection and specific mitotic DSB repair events. Here, the rice (Oryza sativa, 2n = 2x = 24) COM1/SAE2 homolog was identified through positional cloning, termed OsCOM1. Four independent mutants of OsCOM1 were isolated and characterized. In Oscom1 mutants, synaptonemal complex (SC) formation, homologous pairing and recombination were severely inhibited, whereas aberrant non-homologous chromosome entanglements occurred constantly. Several key meiotic proteins, including ZEP1 and OsMER3, were not loaded normally onto chromosomes in Oscom1 mutants, whereas the localization of OsREC8, PAIR2 and PAIR3 seemed to be normal. Moreover, OsCOM1 was loaded normally onto meiotic chromosomes in Osrec8, zep1 and Osmer3 mutants, but could not be properly loaded in Osam1, pair2 and OsSPO11-1(RNAi) plants. These results provide direct evidence for the functions of OsCOM1 in promoting homologous synapsis and recombination in rice meiosis.
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Affiliation(s)
- Jianhui Ji
- State Key Laboratory of Plant Genomics and Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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43
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The tumor suppressor Caliban regulates DNA damage-induced apoptosis through p53-dependent and -independent activity. Oncogene 2012; 32:3857-66. [PMID: 22964637 DOI: 10.1038/onc.2012.395] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 06/04/2012] [Accepted: 07/20/2012] [Indexed: 12/18/2022]
Abstract
We previously identified Caliban (Clbn) as the Drosophila homolog of human Serologically defined colon cancer antigen 1 gene and demonstrated that it could function as a tumor suppressor in human non-small-cell lung cancer (NSCLC) cells, although its mode of action was unknown. Herein, we identify roles for Clbn in DNA damage response. We generate clbn knockout flies using homologous recombination and demonstrate that they have a heightened sensitivity to irradiation. We show that normal Clbn function facilitates both p53-dependent and -independent DNA damage-induced apoptosis. Clbn coordinates different apoptosis pathways, showing a two-stage upregulation following DNA damage. Clbn has proapoptotic functions, working with both caspase and the proapoptotic gene Hid. Finally, ecotopic expression of clbn(+) in NSCLC cells suppresses tumor formation in athymic nude mice. We conclude that Caliban is a regulator of DNA damage-induced apoptosis, functioning as a tumor suppressor in both p53-dependent and -independent pathways.
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Dmp53 is sequestered to nuclear bodies in spermatogonia of Drosophila melanogaster. Cell Tissue Res 2012; 350:385-94. [PMID: 22961348 DOI: 10.1007/s00441-012-1479-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 07/06/2012] [Indexed: 10/28/2022]
Abstract
p53 family members have been implicated in regulation of genomic integrity and apoptosis in a variety of tissues. The Drosophila family member, Dmp53, primarily functions to regulate apoptosis in developing and regenerating tissues but loss of function mutants are viable and fertile. Dmp53 exhibits a striking expression pattern in the male germline with high levels found in nuclear bodies in pre-meiotic germ cells. The localisation of Dmp53 to nuclear bodies is dependent upon Dmp53 complexes being able to bind DNA, and although dmp53 mutants do not affect germline stem cell (GSC) maintenance or differentiation, GSCs are sensitive to overexpression of Dmp53 but maturing spermatogonia are not. Dmp53 thus has differential effects depending upon the stage of male germline maturation.
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45
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Abstract
Telomeres protect chromosome ends from being repaired as double-strand breaks (DSBs). Just as DSB repair is suppressed at telomeres, de novo telomere addition is suppressed at the site of DSBs. To identify factors responsible for this suppression, we developed an assay to monitor de novo telomere formation in Drosophila, an organism in which telomeres can be established on chromosome ends with essentially any sequence. Germline expression of the I-SceI endonuclease resulted in precise telomere formation at its cut site with high efficiency. Using this assay, we quantified the frequency of telomere formation in different genetic backgrounds with known or possible defects in DNA damage repair. We showed that disruption of DSB repair factors (Rad51 or DNA ligase IV) or DSB sensing factors (ATRIP or MDC1) resulted in more efficient telomere formation. Interestingly, partial disruption of factors that normally regulate telomere protection (ATM or NBS) also led to higher frequencies of telomere formation, suggesting that these proteins have opposing roles in telomere maintenance vs. establishment. In the ku70 mutant background, telomere establishment was preceded by excessive degradation of DSB ends, which were stabilized upon telomere formation. Most strikingly, the removal of ATRIP caused a dramatic increase in telomeric retrotransposon attachment to broken ends. Our study identifies several pathways that suppress telomere addition at DSBs, paving the way for future mechanistic studies.
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46
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Wells BS, Johnston LA. Maintenance of imaginal disc plasticity and regenerative potential in Drosophila by p53. Dev Biol 2011; 361:263-76. [PMID: 22036477 DOI: 10.1016/j.ydbio.2011.10.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2011] [Revised: 09/14/2011] [Accepted: 10/08/2011] [Indexed: 10/16/2022]
Abstract
Following irradiation (IR), the DNA damage response (DDR) activates p53, which triggers death of cells in which repair cannot be completed. Lost tissue is then replaced and re-patterned through regeneration. We have examined the role of p53 in co-regulation of the DDR and tissue regeneration following IR damage in Drosophila. We find that after IR, p53 is required for imaginal disc cells to repair DNA, and in its absence the damage marker, γ-H2AX is persistently expressed. p53 is also required for the compensatory proliferation and re-patterning of the damaged discs, and our results indicate that cell death is not required to trigger these processes. We identify an IR-induced delay in developmental patterning in wing discs that accompanies an animal-wide delay of the juvenile-adult transition, and demonstrate that both of these delays require p53. In p53 mutants, the lack of developmental delays and of damage resolution leads to anueploidy and tissue defects, and ultimately to morphological abnormalities and adult inviability. We propose that p53 maintains plasticity of imaginal discs by co-regulating the maintenance of genome integrity and disc regeneration, and coordinating these processes with the physiology of the animal. These findings place p53 in a role as master coordinator of DNA and tissue repair following IR.
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Affiliation(s)
- Brent S Wells
- Department of Genetics & Development, Columbia University Medical Center, New York, NY 10032, USA
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47
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Pardue ML, Debaryshe P. Adapting to life at the end of the line: How Drosophila telomeric retrotransposons cope with their job. Mob Genet Elements 2011; 1:128-134. [PMID: 22016861 DOI: 10.4161/mge.1.2.16914] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2011] [Accepted: 06/07/2011] [Indexed: 11/19/2022] Open
Abstract
Drosophila telomeres are remarkable because they are maintained by telomere-specific retrotransposons, rather than the enzyme telomerase that maintains telomeres in almost every other eukaryotic organism. Successive transpositions of the Drosophila retrotransposons onto chromosome ends produce long head-to-tail arrays that are analogous in form and function to the long arrays of short repeats produced by telomerase in other organisms. Nevertheless, Drosophila telomere repeats are retrotransposons, complex entities three orders of magnitude longer than simple telomerase repeats. During the >40-60 My they have been coevolving with their host, these retrotransposons perforce have evolved a complex relationship with Drosophila cells to maintain populations of active elements while carrying out functions analogous to those of telomerase repeats in other organisms. Although they have assumed a vital role in maintaining the Drosophila genome, the three Drosophila telomere-specific elements are non-LTR retrotransposons, closely related to some of the best known non-telomeric elements in the Drosophila genome. Thus, these elements offer an opportunity to study ways in which retrotransposons and their host cells can coevolve cooperatively. The telomere-specific elements display several characteristics that appear important to their roles at the telomere; for example, we have recently reported that they have evolved at least two innovative mechanisms for protecting essential sequence on their 5'ends. Because every element serves as the end of the chromosome immediately after it transposes, its 5'end is subject to chromosomal erosion until it is capped by a new transposition. These two mechanisms make it possible for at least a significant fraction of elements to survive their initial time as the chromosome end without losing sequence necessary to be competent for subsequent transposition. Analysis of sequence from >90 kb of assembled telomere array shows that these mechanisms for small scale sequence protection are part of a unified set which maintains telomere length homeostasis. Here we concentrate on recently elucidated mechanisms that have evolved to provide this small scale 5' protection.
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Affiliation(s)
- Mary-Lou Pardue
- Department of Biology; Massachusetts Institute of Technology; Cambridge, MA USA
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48
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Kurzhals RL, Titen SWA, Xie HB, Golic KG. Chk2 and p53 are haploinsufficient with dependent and independent functions to eliminate cells after telomere loss. PLoS Genet 2011; 7:e1002103. [PMID: 21655087 PMCID: PMC3107200 DOI: 10.1371/journal.pgen.1002103] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2010] [Accepted: 04/08/2011] [Indexed: 02/06/2023] Open
Abstract
The mechanisms that cells use to monitor telomere integrity, and the array of responses that may be induced, are not fully defined. To date there have been no studies in animals describing the ability of cells to survive and contribute to adult organs following telomere loss. We developed assays to monitor the ability of somatic cells to proliferate and differentiate after telomere loss. Here we show that p53 and Chk2 limit the growth and differentiation of cells that lose a telomere. Furthermore, our results show that two copies of the genes encoding p53 and Chk2 are required for the cell to mount a rapid wildtype response to a missing telomere. Finally, our results show that, while Chk2 functions by activating the p53-dependent apoptotic cascade, Chk2 also functions independently of p53 to limit survival. In spite of these mechanisms to eliminate cells that have lost a telomere, we find that such cells can make a substantial contribution to differentiated adult tissues.
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Affiliation(s)
- Rebeccah L. Kurzhals
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Simon W. A. Titen
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Heng B. Xie
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Kent G. Golic
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
- * E-mail:
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49
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Payne CM, Crowley-Skillicorn C, Bernstein C, Holubec H, Bernstein H. Molecular and cellular pathways associated with chromosome 1p deletions during colon carcinogenesis. Clin Exp Gastroenterol 2011; 4:75-119. [PMID: 21753893 PMCID: PMC3132853 DOI: 10.2147/ceg.s17114] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Indexed: 11/23/2022] Open
Abstract
Chromosomal instability is a major pathway of sporadic colon carcinogenesis. Chromosome arm 1p appears to be one of the "hot spots" in the non-neoplastic mucosa that, when deleted, is associated with the initiation of carcinogenesis. Chromosome arm 1p contains genes associated with DNA repair, spindle checkpoint function, apoptosis, multiple microRNAs, the Wnt signaling pathway, tumor suppression, antioxidant activities, and defense against environmental toxins. Loss of 1p is dangerous since it would likely contribute to genomic instability leading to tumorigenesis. The 1p deletion-associated colon carcinogenesis pathways are reviewed at the molecular and cellular levels. Sporadic colon cancer is strongly linked to a high-fat/low-vegetable/low-micronutrient, Western-style diet. We also consider how selected dietary-related compounds (eg, excess hydrophobic bile acids, and low levels of folic acid, niacin, plant-derived antioxidants, and other modulatory compounds) might affect processes leading to chromosomal deletions, and to the molecular and cellular pathways specifically altered by chromosome 1p loss.
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Affiliation(s)
- Claire M Payne
- Department of Cell Biology and Anatomy, College of Medicine, University of Arizona Tucson, AZ, USA
| | | | - Carol Bernstein
- Department of Cell Biology and Anatomy, College of Medicine, University of Arizona Tucson, AZ, USA
| | - Hana Holubec
- Department of Cell Biology and Anatomy, College of Medicine, University of Arizona Tucson, AZ, USA
| | - Harris Bernstein
- Department of Cell Biology and Anatomy, College of Medicine, University of Arizona Tucson, AZ, USA
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