1
|
Colon Plaza S, Su TT. Ionizing radiation induces cells with past caspase activity that contribute to the adult organ in Drosophila and show reduced Loss of Heterozygosity. Cell Death Discov 2024; 10:6. [PMID: 38182576 PMCID: PMC10770159 DOI: 10.1038/s41420-023-01769-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 12/01/2023] [Accepted: 12/07/2023] [Indexed: 01/07/2024] Open
Abstract
There is increasing recognition that cells may activate apoptotic caspases but not die, instead displaying various physiologically relevant consequences. Mechanisms that underlie the life-or-death decision in a cell that has activated apoptotic caspases, however, are incompletely understood. By optimizing a published reporter for past caspase activity, we were able to visualize cells that survived caspase activation specifically after exposure to ionizing radiation in Drosophila larval wing discs. We found that cells with X-ray-induced past active caspases (XPAC) did not arise at random but were born at specific locations within the developing wing imaginal discs of Drosophila larvae. Inhibiting key components of the apoptotic pathway decreased XPAC number, suggesting that apoptotic signaling is needed to induce XPAC cells. Yet, XPAC cells appeared in stereotypical patterns that did not follow the pattern of IR-induced apoptosis, suggesting additional controls at play. Functional testing identified the contribution of wingless (Drosophila Wnt1) and Ras signaling to the prevalence of XPAC cells. Furthermore, by following irradiated larvae into adulthood, we found that XPAC cells contribute to the adult wing. To address the relationship between XPAC and genome stability, we combined a reporter for past caspase activity with mwh, an adult marker for Loss of Heterozygosity (LOH). We found a lower incidence of LOH among XPAC compared to cells that did not activate the reporter for past caspase activity. In addition, at time points when wing disc cells are finishing DNA repair, XPAC cells show an anti-correlation with cells with unrepaired IR-induced double-stranded breaks. Our data suggest that non-lethal caspase activity safeguards the genome by facilitating DNA repair and reducing LOH after transient exposure to X-rays. These results identify a physiological role for non-lethal caspase activity during recovery from radiation damage.
Collapse
Affiliation(s)
- Sarah Colon Plaza
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, 80309-0347, USA
| | - Tin Tin Su
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, 80309-0347, USA.
| |
Collapse
|
2
|
Brown J, Su TT. E2F1, DIAP1, and the presence of a homologous chromosome promote while JNK inhibits radiation-induced loss of heterozygosity in Drosophila melanogaster. Genetics 2024; 226:iyad192. [PMID: 37874851 PMCID: PMC10763536 DOI: 10.1093/genetics/iyad192] [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: 08/25/2023] [Revised: 08/25/2023] [Accepted: 10/04/2023] [Indexed: 10/26/2023] Open
Abstract
Loss of heterozygosity (LOH) can occur when a heterozygous mutant cell loses the remaining wild-type allele to become a homozygous mutant. LOH can have physiological consequences if, for example, the affected gene encodes a tumor suppressor. We used fluorescent reporters to study the mechanisms of LOH induction by X-rays, a type of ionizing radiation (IR), in Drosophila melanogaster larval wing discs. IR is used to treat more than half of patients with cancer, so understanding its effects is of biomedical relevance. Quantitative analysis of IR-induced LOH at different positions between the telomere and the centromere on the X chromosome showed a strong sex dependence and the need for a recombination-proficient homologous chromosome, whereas, paradoxically, position along the chromosome made little difference in LOH incidence. We propose that published data documenting high recombination frequency within centromeric heterochromatin on the X chromosome can explain these data. Using a focused screen, we identified E2F1 as a key promotor of LOH and further testing suggests a mechanism involving its role in cell-cycle regulation. We leveraged the loss of a transcriptional repressor through LOH to express transgenes specifically in cells that have already acquired LOH. This approach identified JNK signaling and apoptosis as key determinants of LOH maintenance. These studies reveal previously unknown mechanisms for the generation and elimination of cells with chromosome aberrations after exposure to IR.
Collapse
Affiliation(s)
- Jeremy Brown
- Department of Molecular, Cellular and Developmental Biology, 347 UCB, University of Colorado, Boulder, CO 80309-0347, USA
- Department of Cell and Developmental Biology, University of Colorado, Anschutz Medical Campus, 13001 E. 17th Pl., Aurora, CO 80045, USA
| | - Tin Tin Su
- Department of Molecular, Cellular and Developmental Biology, 347 UCB, University of Colorado, Boulder, CO 80309-0347, USA
- University of Colorado Cancer Center, Anschutz Medical Campus, 13001 E. 17th Pl., Aurora, CO 80045, USA
| |
Collapse
|
3
|
Brown J, Su TT. E2F1 promotes, JNK and DIAP1 inhibit, and chromosomal position has little effect on radiation-induced Loss of Heterozygosity in Drosophila. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.09.540084. [PMID: 37214983 PMCID: PMC10197609 DOI: 10.1101/2023.05.09.540084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Loss of Heterozygosity (LOH) can occur when a heterozygous mutant cell loses the remaining wild type allele to become a homozygous mutant. LOH can have physiological consequences if, for example, the affected gene encodes a tumor suppressor. We used two fluorescent reporters to study mechanisms of LOH induction by X-rays, a type of ionizing radiation (IR), in Drosophila larval wing discs. IR is used to treat more than half of cancer patients, so understanding its effects is of biomedical relevance. We report that IR-induced LOH does not correlate with the chromosomal position of the LOH locus, unlike previously shown for spontaneously occurring LOH. Like spontaneous LOH, however, IR-induced LOH of X-linked loci shows a sex-dependence, occurring predominately in females. A focused genetic screen identified E2F1 as a key promotor of LOH and further testing suggests a mechanism involving its role in cell cycle regulation rather than apoptosis. We combined the QF/QS LOH reporter with QUAS-transgenes to manipulate gene function after LOH induction. This approach identified JNK signaling and apoptosis as key determinants of LOH maintenance. These studies reveal previously unknown mechanisms for generation and maintenance of cells with chromosome aberrations after exposure to IR.
Collapse
|
4
|
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: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [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.
Collapse
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
| |
Collapse
|
5
|
Brown J, Bush I, Bozon J, Su TT. Cells with loss-of-heterozygosity after exposure to ionizing radiation in Drosophila are culled by p53-dependent and p53-independent mechanisms. PLoS Genet 2020; 16:e1009056. [PMID: 33075096 PMCID: PMC7595702 DOI: 10.1371/journal.pgen.1009056] [Citation(s) in RCA: 4] [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: 12/26/2019] [Revised: 10/29/2020] [Accepted: 08/17/2020] [Indexed: 11/18/2022] Open
Abstract
Loss of Heterozygosity (LOH) typically refers to a phenomenon in which diploid cells that are heterozygous for a mutant allele lose their wild type allele through mutations. LOH is implicated in oncogenesis when it affects the remaining wild type copy of a tumor suppressor. Drosophila has been a useful model to identify genes that regulate the incidence of LOH, but most of these studies use adult phenotypic markers such as multiple wing hair (mwh). Here, we describe a cell-autonomous fluorescence-based system that relies on the QF/QS transcriptional module to detect LOH, which may be used in larval, pupal and adult stages and in conjunction with the GAL4/UAS system. Using the QF/QS system, we were able to detect the induction of cells with LOH by X-rays in a dose-dependent manner in the larval wing discs, and to monitor their fate through subsequent development in pupa and adult stages. We tested the genetic requirement for changes in LOH, using both classical mutants and GAL4/UAS-mediated RNAi. Our results identify two distinct culling phases that eliminate cells with LOH, one in late larval stages and another in the pupa. The two culling phases are genetically separable, showing differential requirement for pro-apoptotic genes of the H99 locus and transcription factor Srp. A direct comparison of mwh LOH and QF/QS LOH suggests that cells with different LOH events are distinguished from each other in a p53-dependent manner and are retained to different degrees in the final adult structure. These studies reveal previously unknown mechanisms for the elimination of cells with chromosome aberrations.
Collapse
Affiliation(s)
- Jeremy Brown
- Department of Molecular, Cellular and Developmental Biology, 347 UCB, University of Colorado, Boulder, CO, United States of America
| | - Inle Bush
- Department of Molecular, Cellular and Developmental Biology, 347 UCB, University of Colorado, Boulder, CO, United States of America
| | - Justine Bozon
- Department of Molecular, Cellular and Developmental Biology, 347 UCB, University of Colorado, Boulder, CO, United States of America
| | - Tin Tin Su
- Department of Molecular, Cellular and Developmental Biology, 347 UCB, University of Colorado, Boulder, CO, United States of America
| |
Collapse
|
6
|
Sekelsky J. DNA Repair in Drosophila: Mutagens, Models, and Missing Genes. Genetics 2017; 205:471-490. [PMID: 28154196 PMCID: PMC5289830 DOI: 10.1534/genetics.116.186759] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 10/18/2016] [Indexed: 12/22/2022] Open
Abstract
The numerous processes that damage DNA are counterbalanced by a complex network of repair pathways that, collectively, can mend diverse types of damage. Insights into these pathways have come from studies in many different organisms, including Drosophila melanogaster Indeed, the first ideas about chromosome and gene repair grew out of Drosophila research on the properties of mutations produced by ionizing radiation and mustard gas. Numerous methods have been developed to take advantage of Drosophila genetic tools to elucidate repair processes in whole animals, organs, tissues, and cells. These studies have led to the discovery of key DNA repair pathways, including synthesis-dependent strand annealing, and DNA polymerase theta-mediated end joining. Drosophila appear to utilize other major repair pathways as well, such as base excision repair, nucleotide excision repair, mismatch repair, and interstrand crosslink repair. In a surprising number of cases, however, DNA repair genes whose products play important roles in these pathways in other organisms are missing from the Drosophila genome, raising interesting questions for continued investigations.
Collapse
Affiliation(s)
- Jeff Sekelsky
- Department of Biology and Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, North Carolina 27599
| |
Collapse
|
7
|
Srinivasan DG, Abdelhady A, Stern DL. Gene expression analysis of parthenogenetic embryonic development of the pea aphid, Acyrthosiphon pisum, suggests that aphid parthenogenesis evolved from meiotic oogenesis. PLoS One 2014; 9:e115099. [PMID: 25501006 PMCID: PMC4264872 DOI: 10.1371/journal.pone.0115099] [Citation(s) in RCA: 12] [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: 07/26/2014] [Accepted: 11/18/2014] [Indexed: 11/18/2022] Open
Abstract
Aphids exhibit a form of phenotypic plasticity, called polyphenism, in which genetically identical females reproduce sexually during one part of the life cycle and asexually (via parthenogenesis) during the remainder of the life cycle. The molecular basis for aphid parthenogenesis is unknown. Cytological observations of aphid parthenogenesis suggest that asexual oogenesis evolved either through a modification of meiosis or from a mitotic process. As a test of these alternatives, we assessed the expression levels and expression patterns of canonical meiotic recombination and germline genes in the sexual and asexual ovaries of the pea aphid, Acyrthosiphon pisum. We observed expression of all meiosis genes in similar patterns in asexual and sexual ovaries, with the exception that some genes encoding Argonaute-family members were not expressed in sexual ovaries. In addition, we observed that asexual aphid tissues accumulated unspliced transcripts of Spo11, whereas sexual aphid tissues accumulated primarily spliced transcripts. In situ hybridization revealed Spo11 transcript in sexual germ cells and undetectable levels of Spo11 transcript in asexual germ cells. We also found that an obligately asexual strain of pea aphid produced little spliced Spo11 transcript. Together, these results suggest that parthenogenetic oogenesis evolved from a meiosis-like, and not a mitosis-like, process and that the aphid reproductive polyphenism may involve a modification of Spo11 gene activity.
Collapse
Affiliation(s)
- Dayalan G. Srinivasan
- Howard Hughes Medical Institute and Department of Ecology and Evolutionary Biology, Guyot Hall, Princeton University, Princeton, NJ, 08544, United States of America
- Department of Biological Science, Rowan University, 201 Mullica Hill Rd, Glassboro, NJ, 08028, United States of America
| | - Ahmed Abdelhady
- Department of Biological Science, Rowan University, 201 Mullica Hill Rd, Glassboro, NJ, 08028, United States of America
| | - David L. Stern
- Howard Hughes Medical Institute and Department of Ecology and Evolutionary Biology, Guyot Hall, Princeton University, Princeton, NJ, 08544, United States of America
| |
Collapse
|
8
|
Lee EM, Trinh TTB, Shim HJ, Park SY, Nguyen TTT, Kim MJ, Song YH. Drosophila Claspin is required for the G2 arrest that is induced by DNA replication stress but not by DNA double-strand breaks. DNA Repair (Amst) 2012; 11:741-52. [PMID: 22796626 DOI: 10.1016/j.dnarep.2012.06.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 05/31/2012] [Accepted: 06/22/2012] [Indexed: 01/24/2023]
Abstract
ATR and Chk1 are protein kinases that perform major roles in the DNA replication checkpoint that delays entry into mitosis in response to DNA replication stress by hydroxyurea (HU) treatment. They are also activated by ionizing radiation (IR) that induces DNA double-strand breaks. Studies in human tissue culture and Xenopus egg extracts identified Claspin as a mediator that increased the activity of ATR toward Chk1. Because the in vivo functions of Claspin are not known, we generated Drosophila lines that each contained a mutated Claspin gene. Similar to the Drosophila mei-41/ATR and grp/Chk1 mutants, embryos of the Claspin mutant showed defects in checkpoint activation, which normally occurs in early embryogenesis in response to incomplete DNA replication. Additionally, Claspin mutant larvae were defective in G2 arrest after HU treatment; however, the defects were less severe than those of the mei-41/ATR and grp/Chk1 mutants. In contrast, IR-induced G2 arrest, which was severely defective in mei-41/ATR and grp/Chk1 mutants, occurred normally in the Claspin mutant. We also found that Claspin was phosphorylated in response to HU and IR treatment and a hyperphosphorylated form of Claspin was generated only after HU treatment in mei-41/ATR-dependent and tefu/ATM-independent way. In summary, our data suggest that Drosophila Claspin is required for the G2 arrest that is induced by DNA replication stress but not by DNA double-strand breaks, and this difference is probably due to distinct phosphorylation statuses.
Collapse
Affiliation(s)
- Eun-Mi Lee
- Ilsong Institute of Life Science, Hallym University, Anyang, Republic of Korea
| | | | | | | | | | | | | |
Collapse
|
9
|
Gregg SQ, Robinson AR, Niedernhofer LJ. Physiological consequences of defects in ERCC1-XPF DNA repair endonuclease. DNA Repair (Amst) 2011; 10:781-91. [PMID: 21612988 DOI: 10.1016/j.dnarep.2011.04.026] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
ERCC1-XPF is a structure-specific endonuclease required for nucleotide excision repair, interstrand crosslink repair, and the repair of some double-strand breaks. Mutations in ERCC1 or XPF cause xeroderma pigmentosum, XFE progeroid syndrome or cerebro-oculo-facio-skeletal syndrome, characterized by increased risk of cancer, accelerated aging and severe developmental abnormalities, respectively. This review provides a comprehensive overview of the health impact of ERCC1-XPF deficiency, based on these rare diseases and mouse models of them. This offers an understanding of the tremendous health impact of DNA damage derived from environmental and endogenous sources.
Collapse
Affiliation(s)
- Siobhán Q Gregg
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | | | | |
Collapse
|
10
|
Papaconstantinou M, Pepper AN, Wu Y, Kasimer D, Westwood T, Campos AR, Bédard PA. Menin links the stress response to genome stability in Drosophila melanogaster. PLoS One 2010; 5:e14049. [PMID: 21124979 PMCID: PMC2987805 DOI: 10.1371/journal.pone.0014049] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Accepted: 10/01/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The multiple endocrine neoplasia type I gene functions as a tumor suppressor gene in humans and mouse models. In Drosophila melanogaster, mutants of the menin gene (Mnn1) are hypersensitive to mutagens or gamma irradiation and have profound defects in the response to several stresses including heat shock, hypoxia, hyperosmolarity and oxidative stress. However, it is not known if the function of menin in the stress response contributes to genome stability. The objective of this study was to examine the role of menin in the control of the stress response and genome stability. METHODOLOGY/PRINCIPAL FINDINGS Using a test of loss-of-heterozygosity, we show that Drosophila strains lacking a functional Mnn1 gene or expressing a Mnn1 dsRNA display increased genome instability in response to non-lethal heat shock or hypoxia treatments. This is also true for strains lacking all Hsp70 genes, implying that a precise control of the stress response is required for genome stability. While menin is required for Hsp70 expression, the results of epistatic studies indicate that the increase in genome instability observed in Mnn1 lack-of-function mutants cannot be accounted for by mis-expression of Hsp70. Therefore, menin may promote genome stability by controlling the expression of other stress-responsive genes. In agreement with this notion, gene profiling reveals that Mnn1 is required for sustained expression of all heat shock protein genes but is dispensable for early induction of the heat shock response. CONCLUSIONS/SIGNIFICANCE Mutants of the Mnn1 gene are hypersensitive to several stresses and display increased genome instability when subjected to conditions, such as heat shock, generally regarded as non-genotoxic. In this report, we describe a role for menin as a global regulator of heat shock gene expression and critical factor in the maintenance of genome integrity. Therefore, menin links the stress response to the control of genome stability in Drosophila melanogaster.
Collapse
Affiliation(s)
| | - Alicia N. Pepper
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
| | - Ying Wu
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
| | - Dahlia Kasimer
- Department of Cell and Systems Biology and Canadian Drosophila Microarray Centre, University of Toronto, Mississauga, Ontario, Canada
| | - Tim Westwood
- Department of Cell and Systems Biology and Canadian Drosophila Microarray Centre, University of Toronto, Mississauga, Ontario, Canada
| | - Ana Regina Campos
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
| | - Pierre-André Bédard
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
- * E-mail:
| |
Collapse
|
11
|
Abstract
Within-laboratory collaborative projects wherein each worker performs the technique he or she does best are common nowadays. Opportunities for projects wherein everyone does everything are less common, but these projects bring their own satisfactions; the Great Translocation Hunt is presented as an example.
Collapse
|
12
|
Abstract
SUMMARYBy means of genetic mosaics we have studied the cell autonomy ofmei-41andmei-9, two loci involved in DNA metabolism. The frequency of spontaneous somatic spots resulting from unrepaired chromosome damage and the sensitivity of mutant cells to killing by X-irradiation - two traits indicative of deficient DNA repair - have been analysed at the cellular level. The results show that: (1) The effect of both mutations on chromosome stability is cell autonomous. (2) After 1000 r of X-irradiation practically all the cells homozygous formei-41disappear while about one-third of the cells homozygous formei-9asurvive the irradiation. The possibility of using these mutants as tools to approach developmental problems is discussed.
Collapse
|
13
|
Abstract
DNA damage or unprotected telomeres can trigger apoptosis via signaling pathways that directly sense abnormal DNA structures and activate the p53 transcription factor. We describe a p53-independent mechanism that acts in parallel to the canonical DNA damage response pathway in Drosophila to induce apoptosis after exposure to ionizing radiation. Following recovery from damage-induced cell cycle arrest, p53 mutant cells activate the JNK pathway and expression of the pro-apoptotic gene hid. Mutations in grp, a cell cycle checkpoint gene, and puc, a negative regulator of the JNK pathway, sensitize p53 mutant cells to ionizing radiation (IR)-induced apoptosis. Induction of chromosome aberrations by DNA damage generates cells with segmental aneuploidy and heterozygous for mutations in ribosomal protein genes. p53-independent apoptosis limits the formation of these aneuploid cells following DNA damage. We propose that reduced copy number of haploinsufficient genes following chromosome damage activates apoptosis and helps maintain genomic integrity.
Collapse
|
14
|
Vannier JB, Depeiges A, White C, Gallego ME. ERCC1/XPF protects short telomeres from homologous recombination in Arabidopsis thaliana. PLoS Genet 2009; 5:e1000380. [PMID: 19214203 PMCID: PMC2632759 DOI: 10.1371/journal.pgen.1000380] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Accepted: 01/13/2009] [Indexed: 12/17/2022] Open
Abstract
Many repair and recombination proteins play essential roles in telomere function and chromosome stability, notwithstanding the role of telomeres in "hiding" chromosome ends from DNA repair and recombination. Among these are XPF and ERCC1, which form a structure-specific endonuclease known for its essential role in nucleotide excision repair and is the subject of considerable interest in studies of recombination. In contrast to observations in mammalian cells, we observe no enhancement of chromosomal instability in Arabidopsis plants mutated for either XPF (AtRAD1) or ERCC1 (AtERCC1) orthologs, which develop normally and show wild-type telomere length. However, in the absence of telomerase, mutation of either of these two genes induces a significantly earlier onset of chromosomal instability. This early appearance of telomere instability is not due to a general acceleration of telomeric repeat loss, but is associated with the presence of dicentric chromosome bridges and cytologically visible extrachromosomal DNA fragments in mitotic anaphase. Such extrachromosomal fragments are not observed in later-generation single-telomerase mutant plants presenting similar frequencies of anaphase bridges. Extensive FISH analyses show that these DNAs are broken chromosomes and correspond to two specific chromosome arms. Analysis of the Arabidopsis genome sequence identified two extensive blocks of degenerate telomeric repeats, which lie at the bases of these two arms. Our data thus indicate a protective role of ERCC1/XPF against 3' G-strand overhang invasion of interstitial telomeric repeats. The fact that the Atercc1 (and Atrad1) mutants dramatically potentiate levels of chromosome instability in Attert mutants, and the absence of such events in the presence of telomerase, have important implications for models of the roles of recombination at telomeres and is a striking illustration of the impact of genome structure on the outcomes of equivalent recombination processes in different organisms.
Collapse
Affiliation(s)
- Jean-Baptiste Vannier
- Génétique, Reproduction et Développement, UMR CNRS 6247, Clermont Université, INSERM U931, Aubière, France
| | - Annie Depeiges
- Génétique, Reproduction et Développement, UMR CNRS 6247, Clermont Université, INSERM U931, Aubière, France
| | - Charles White
- Génétique, Reproduction et Développement, UMR CNRS 6247, Clermont Université, INSERM U931, Aubière, France
| | - Maria Eugenia Gallego
- Génétique, Reproduction et Développement, UMR CNRS 6247, Clermont Université, INSERM U931, Aubière, France
- * E-mail:
| |
Collapse
|
15
|
Abstract
ERCC1-XPF endonuclease is required for nucleotide excision repair (NER) of helix-distorting DNA lesions. However, mutations in ERCC1 or XPF in humans or mice cause a more severe phenotype than absence of NER, prompting a search for novel repair activities of the nuclease. In Saccharomyces cerevisiae, orthologs of ERCC1-XPF (Rad10-Rad1) participate in the repair of double-strand breaks (DSBs). Rad10-Rad1 contributes to two error-prone DSB repair pathways: microhomology-mediated end joining (a Ku86-independent mechanism) and single-strand annealing. To determine if ERCC1-XPF participates in DSB repair in mammals, mutant cells and mice were screened for sensitivity to gamma irradiation. ERCC1-XPF-deficient fibroblasts were hypersensitive to gamma irradiation, and gammaH2AX foci, a marker of DSBs, persisted in irradiated mutant cells, consistent with a defect in DSB repair. Mutant mice were also hypersensitive to irradiation, establishing an essential role for ERCC1-XPF in protecting against DSBs in vivo. Mice defective in both ERCC1-XPF and Ku86 were not viable. However, Ercc1(-/-) Ku86(-/-) fibroblasts were hypersensitive to gamma irradiation compared to single mutants and accumulated significantly greater chromosomal aberrations. Finally, in vitro repair of DSBs with 3' overhangs led to large deletions in the absence of ERCC1-XPF. These data support the conclusion that, as in yeast, ERCC1-XPF facilitates DSB repair via an end-joining mechanism that is Ku86 independent.
Collapse
|
16
|
Saunders RDC, Boubriak I, Clancy DJ, Cox LS. Identification and characterization of a Drosophila ortholog of WRN exonuclease that is required to maintain genome integrity. Aging Cell 2008; 7:418-25. [PMID: 18346216 PMCID: PMC2408639 DOI: 10.1111/j.1474-9726.2008.00388.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The premature human aging Werner syndrome (WS) is caused by mutation of the RecQ-family WRN helicase, which is unique in possessing also 3′–5′ exonuclease activity. WS patients show significant genomic instability with elevated cancer incidence. WRN is implicated in restraining illegitimate recombination, especially during DNA replication. Here we identify a Drosophila ortholog of the WRN exonuclease encoded by the CG7670 locus. The predicted DmWRNexo protein shows conservation of structural motifs and key catalytic residues with human WRN exonuclease, but entirely lacks a helicase domain. Insertion of a piggyBac element into the 5′ UTR of CG7670 severely reduces gene expression. DmWRNexo mutant flies homozygous for this insertional allele of CG7670 are thus severely hypomorphic; although adults show no gross morphological abnormalities, females are sterile. Like human WS cells, we show that the DmWRNexo mutant flies are hypersensitive to the topoisomerase I inhibitor camptothecin. Furthermore, these mutant flies show highly elevated rates of mitotic DNA recombination resulting from excessive reciprocal exchange. This study identifies a novel WRN ortholog in flies and demonstrates an important role for WRN exonuclease in maintaining genome stability.
Collapse
Affiliation(s)
- Robert D C Saunders
- Department of Biological Sciences, The Open University, Milton Keynes MK7 6AA, UK.
| | | | | | | |
Collapse
|
17
|
Lake CM, Teeter K, Page SL, Nielsen R, Hawley RS. A genetic analysis of the Drosophila mcm5 gene defines a domain specifically required for meiotic recombination. Genetics 2007; 176:2151-63. [PMID: 17565942 PMCID: PMC1950621 DOI: 10.1534/genetics.107.073551] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Members of the minichromosome maintenance (MCM) family have pivotal roles in many biological processes. Although originally studied for their role in DNA replication, it is becoming increasingly apparent that certain members of this family are multifunctional and also play roles in transcription, cohesion, condensation, and recombination. Here we provide a genetic dissection of the mcm5 gene in Drosophila that demonstrates an unexpected function for this protein. First, we show that homozygotes for a null allele of mcm5 die as third instar larvae, apparently as a result of blocking those replication events that lead to mitotic divisions without impairing endo-reduplication. However, we have also recovered a viable and fertile allele of mcm5 (denoted mcm5(A7)) that specifically impairs the meiotic recombination process. We demonstrate that the decrease in recombination observed in females homozygous for mcm5(A7) is not due to a failure to create or repair meiotically induced double strand breaks (DSBs), but rather to a failure to resolve those DSBs into meiotic crossovers. Consistent with their ability to repair meiotically induced DSBs, flies homozygous for mcm5(A7) are fully proficient in somatic DNA repair. These results strengthen the observation that members of the prereplicative complex have multiple functions and provide evidence that mcm5 plays a critical role in the meiotic recombination pathway.
Collapse
Affiliation(s)
- Cathleen M Lake
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA.
| | | | | | | | | |
Collapse
|
18
|
LaRocque JR, Dougherty DL, Hussain SK, Sekelsky J. Reducing DNA polymerase alpha in the absence of Drosophila ATR leads to P53-dependent apoptosis and developmental defects. Genetics 2007; 176:1441-51. [PMID: 17483406 PMCID: PMC1931523 DOI: 10.1534/genetics.107.073635] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The ability to respond to DNA damage and incomplete replication ensures proper duplication and stability of the genome. Two checkpoint kinases, ATM and ATR, are required for DNA damage and replication checkpoint responses. In Drosophila, the ATR ortholog (MEI-41) is essential for preventing entry into mitosis in the presence of DNA damage. In the absence of MEI-41, heterozygosity for the E(mus304) mutation causes rough eyes. We found that E(mus304) is a mutation in DNApol-alpha180, which encodes the catalytic subunit of DNA polymerase alpha. We did not find any defects resulting from reducing Polalpha by itself. However, reducing Polalpha in the absence of MEI-41 resulted in elevated P53-dependent apoptosis, rough eyes, and increased genomic instability. Reducing Polalpha in mutants that lack downstream components of the DNA damage checkpoint (DmChk1 and DmChk2) results in the same defects. Furthermore, reducing levels of mitotic cyclins rescues both phenotypes. We suggest that reducing Polalpha slows replication, imposing an essential requirement for the MEI-41-dependent checkpoint for maintenance of genome stability, cell survival, and proper development. This work demonstrates a critical contribution of the checkpoint function of MEI-41 in responding to endogenous damage.
Collapse
Affiliation(s)
- Jeannine R LaRocque
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | | | | | | |
Collapse
|
19
|
Blanton HL, Radford SJ, McMahan S, Kearney HM, Ibrahim JG, Sekelsky J. REC, Drosophila MCM8, drives formation of meiotic crossovers. PLoS Genet 2006; 1:e40. [PMID: 16189551 PMCID: PMC1231718 DOI: 10.1371/journal.pgen.0010040] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Accepted: 08/17/2005] [Indexed: 11/19/2022] Open
Abstract
Crossovers ensure the accurate segregation of homologous chromosomes from one another during meiosis. Here, we describe the identity and function of the Drosophila melanogaster gene recombination defective (rec), which is required for most meiotic crossing over. We show that rec encodes a member of the mini-chromosome maintenance (MCM) protein family. Six MCM proteins (MCM2–7) are essential for DNA replication and are found in all eukaryotes. REC is the Drosophila ortholog of the recently identified seventh member of this family, MCM8. Our phylogenetic analysis reveals the existence of yet another family member, MCM9, and shows that MCM8 and MCM9 arose early in eukaryotic evolution, though one or both have been lost in multiple eukaryotic lineages. Drosophila has lost MCM9 but retained MCM8, represented by REC. We used genetic and molecular methods to study the function of REC in meiotic recombination. Epistasis experiments suggest that REC acts after the Rad51 ortholog SPN-A but before the endonuclease MEI-9. Although crossovers are reduced by 95% in rec mutants, the frequency of noncrossover gene conversion is significantly increased. Interestingly, gene conversion tracts in rec mutants are about half the length of tracts in wild-type flies. To account for these phenotypes, we propose that REC facilitates repair synthesis during meiotic recombination. In the absence of REC, synthesis does not proceed far enough to allow formation of an intermediate that can give rise to crossovers, and recombination proceeds via synthesis-dependent strand annealing to generate only noncrossover products. Most of our cells have two copies of each chromosome. For sexual reproduction, these must separate from one another to produce sperm or eggs with one copy of each chromosome. This occurs during meiosis, when chromosomes pair and exchange DNA segments. This exchange— meiotic recombination—creates physical linkages between chromosome pairs and is also a source of genetic diversity. To learn more about the process of meiotic recombination, the authors characterized the gene recombination defective (rec) from the fruit fly Drosophila melanogaster. Molecular analysis revealed that rec is related to a large family of genes found in all animals, plants, and protists. These genes are thought to be important in DNA replication, but rec appears to have a novel function. The authors found that mutants lacking rec are unable to copy enough DNA during meiotic recombination to form linkages between chromosomes. This results in chromosomes segregating randomly during meiosis, so that most eggs have an incorrect number or composition of chromosomes.
Collapse
Affiliation(s)
- Hunter L Blanton
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Sarah J Radford
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Susan McMahan
- Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Hutton M Kearney
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Joseph G Ibrahim
- Department of Biostatistics, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Jeff Sekelsky
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- * To whom correspondence should be addressed. E-mail:
| |
Collapse
|
20
|
Chmuzh EV, Shestakova LA, Volkova VS, Zakharov IK. Diversity of mechanisms and functions of enzyme systems of DNA repair in Drosophila melanogaster. RUSS J GENET+ 2006. [DOI: 10.1134/s1022795406040028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
21
|
McEwen DG, Peifer M. Puckered, a Drosophila MAPK phosphatase, ensures cell viability by antagonizing JNK-induced apoptosis. Development 2005; 132:3935-46. [PMID: 16079158 DOI: 10.1242/dev.01949] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
MAPK phosphatases (MKPs) are important negative regulators of MAPKs in vivo, but ascertaining the role of specific MKPs is hindered by functional redundancy in vertebrates. Thus, we characterized MKP function by examining the function of Puckered (Puc), the sole Drosophila Jun N-terminal kinase (JNK)-specific MKP, during embryonic and imaginal disc development. We demonstrate that Puc is a key anti-apoptotic factor that prevents apoptosis in epithelial cells by restraining basal JNK signaling. Furthermore, we demonstrate that JNK signaling plays an important role in gamma-irradiation-induced apoptosis, and examine how JNK signaling fits into the circuitry regulating this process. Radiation upregulates both JNK activity and puc expression in a p53-dependent manner, and apoptosis induced by loss of Puc can be suppressed by p53 inactivation. JNK signaling acts upstream of both Reaper and effector caspases. Finally, we demonstrate that JNK signaling directs normal developmentally regulated apoptotic events. However, if cell death is prevented, JNK activation can trigger tissue overgrowth. Thus, MKPs are key regulators of the delicate balance between proliferation, differentiation and apoptosis during development.
Collapse
Affiliation(s)
- Donald G McEwen
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA.
| | | |
Collapse
|
22
|
Blanton H, Sekelsky J. Unique invasions and resolutions: DNA repair proteins in meiotic recombination in Drosophila melanogaster. Cytogenet Genome Res 2005; 107:172-9. [PMID: 15467362 DOI: 10.1159/000080595] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2003] [Accepted: 02/06/2004] [Indexed: 11/19/2022] Open
Abstract
To ensure the accurate disjunction of homologous chromosomes during meiosis, most eukaryotes rely on physical connections called chiasmata, which form at sites of crossing over. In the absence of crossing over, homologs may segregate randomly, resulting in high frequencies of aneuploid gametes. The process of meiotic recombination poses unique problems for the cell that must be overcome to ensure normal disjunction of homologous chromosomes. How is it ensured that crossovers occur between homologous chromosomes, rather than between sister chromatids? What determines the number and location of crossovers? The functions of DNA repair proteins hold some of the answers to these questions. In this review, we discuss DNA repair proteins that function in meiotic recombination in Drosophila melanogaster. We emphasize the processes of strand invasion and Holliday junction resolution in order to shed light on the questions raised above. Also, we compare the variety of ways several eukaryotes perform these processes and the different proteins they require.
Collapse
Affiliation(s)
- H Blanton
- Department of Biology and Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | | |
Collapse
|
23
|
|
24
|
Yildiz O, Kearney H, Kramer BC, Sekelsky JJ. Mutational analysis of the Drosophila DNA repair and recombination gene mei-9. Genetics 2005; 167:263-73. [PMID: 15166153 PMCID: PMC1470841 DOI: 10.1534/genetics.167.1.263] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Drosophila mei-9 is essential for several DNA repair and recombination pathways, including nucleotide excision repair (NER), interstrand crosslink repair, and meiotic recombination. To better understand the role of MEI-9 in these processes, we characterized 10 unique mutant alleles of mei-9. These include a P-element insertion that disrupts repair functions but not the meiotic function; three nonsense mutations, one of which has nearly wild-type levels of protein; three missense mutations, one of which disrupts the meiotic function but not repair functions; two small in-frame deletions; and one frameshift.
Collapse
Affiliation(s)
- Ozlem Yildiz
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | | | | | | |
Collapse
|
25
|
Symphorien S, Woodruff RC. Effect of DNA Repair on Aging of Transgenic Drosophila melanogaster: I. mei-41 Locus. J Gerontol A Biol Sci Med Sci 2003; 58:B782-7. [PMID: 14528032 DOI: 10.1093/gerona/58.9.b782] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Aging appears to be increased by diminished DNA repair. To study this relationship between aging and DNA repair, we measured the life span of Drosophila melanogaster males in the absence of mei-41 excision repair and transgenic flies with 1 or 2 extra copies of the mei-41 wild-type gene. Life span was significantly reduced in the absence of repair and was significantly increased by an extra dose of excision repair. However, these changes in life span with alterations in DNA repair were not large.
Collapse
Affiliation(s)
- Sonia Symphorien
- Department of Biological Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA
| | | |
Collapse
|
26
|
Sogame N, Kim M, Abrams JM. Drosophila p53 preserves genomic stability by regulating cell death. Proc Natl Acad Sci U S A 2003; 100:4696-701. [PMID: 12672954 PMCID: PMC153618 DOI: 10.1073/pnas.0736384100] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
When animal cells are exposed to stressful conditions, the tumor suppressor protein p53 restrains growth by promoting an arrested cell cycle or initiating a cell death program. How these distinct fates are specified through the action of a single protein is not known. To study its functions in vivo we produced a targeted mutation at the Drosophila p53 (Dmp53) locus. We show that Dmp53 is required for damage-induced apoptosis but not for cell-cycle arrest. Dmp53 function is also required for damage-induced transcription of two tightly linked cell death activators, reaper and sickle. When challenged by ionizing radiation, Dmp53 mutants exhibit radiosensitivity and genomic instability. Hence, elevated mutant loads were not caused by defective checkpoint functions but instead correlated with failures in p53-associated cell death. Our studies support the notion that core ancestral functions of the p53 gene family are intimately coupled to cell death as an adaptive response to maintain genomic stability.
Collapse
Affiliation(s)
- Naoko Sogame
- Department of Cell Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9039, USA
| | | | | |
Collapse
|
27
|
Carpenter ATC. Normal synaptonemal complex and abnormal recombination nodules in two alleles of the Drosophila meiotic mutant mei-W68. Genetics 2003; 163:1337-56. [PMID: 12702679 PMCID: PMC1462523 DOI: 10.1093/genetics/163.4.1337] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The meiotic phenotypes of two mutant alleles of the mei-W68 gene, 1 and L1, were studied by genetics and by serial-section electron microscopy. Despite no or reduced exchange, both mutant alleles have normal synaptonemal complex. However, neither has any early recombination nodules; instead, both exhibit high numbers of very long (up to 2 microm) structures here named "noodles." These are hypothesized to be formed by the unchecked extension of identical but much shorter structures ephemerally seen in wild type, which may be precursors of early recombination nodules. Although the mei-W68(L1) allele is identical to the mei-W68(1) allele in both the absence of early recombination nodules and a high frequency of noodles (i.e., it is amorphic for the noodle phene), it is hypomorphic in its effects on exchange and late recombination nodules. The differential effects of this allele on early and late recombination nodules are consistent with the hypothesis that Drosophila females have two separate recombination pathways-one for simple gene conversion, the other for exchange.
Collapse
|
28
|
Manheim EA, Jang JK, Dominic D, McKim KS. Cytoplasmic localization and evolutionary conservation of MEI-218, a protein required for meiotic crossing-over in Drosophila. Mol Biol Cell 2002; 13:84-95. [PMID: 11809824 PMCID: PMC65074 DOI: 10.1091/mbc.01-06-0318] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
During Drosophila oogenesis, the oocyte is formed within a 16-cell cyst immediately after four incomplete cell divisions. One of the primary events in oocyte development is meiotic recombination. Here, we report the intracellular localization of the MEI-218 protein that is specifically required for meiotic crossing-over. To understand the role of mei-218 in meiosis and to study the regulation of genes required for meiotic recombination, we characterized the expression pattern of its RNA and protein. Furthermore, we cloned and sequenced mei-218 from two other Drosophila species. The mei-218 RNA and protein have a similar expression pattern, appearing first in early meiotic prophase and then rapidly disappearing as prophase is completed. This pattern corresponds to a specific appearance of the mei-218 gene product in the region of the ovary where meiotic prophase occurs. Although mei-218 is required for 95% of all crossovers, the protein is found exclusively in the cytoplasm. Based on these results, we suggest that mei-218 does not have a direct role in recombination but rather regulates other factors required for the production of crossovers. We propose that mei-218 is a molecular link between oocyte differentiation and meiosis.
Collapse
|
29
|
Vogel EW, Nivard MJ. Phenotypes of Drosophila homologs of human XPF and XPG to chemically-induced DNA modifications. Mutat Res 2001; 476:149-65. [PMID: 11336992 DOI: 10.1016/s0027-5107(01)00121-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
DmXPF (mei9) and DmXPG (mus201) mutants are Drosophila homologs of the mammalian XPF and XPG genes, respectively. For Drosophila germ cells, causal correlations exist between the magnitude of a potentiating effect of a deficiency in these functions, measured as the M(NER-)/M(NER+) mutability ratio, and the type of DNA modification. M(NER-)/M(NER+) mutability ratios may vary with time interval between DNA adduct formation and repair, mutagen dose and depend also on the genetic endpoint measured. For forward mutations, there is no indication of any differential response of DmXPF compared to DmXPG. Subtle features appeared from a class-by-class comparison: (i) Methylating agents always produce higher M(NER-)/M(NER+) ratios than their ethylating analogs; (ii) M(NER-)/M(NER+) mutability ratios are significantly enhanced for cross-linking N-mustards, aziridine and di-epoxide compounds, but not for cross-linking nitrosoureas. The low hypermutability effects with bifunctional nitrogen mustards, aziridine and epoxide compounds are attributed to unrepaired mono-alkyl adducts; (iii) The efficient repair of mono-alkyl-adducts at ring nitrogens in wild-type germ cells is evident from the absence of a dose-response relationship for ethylene oxide, propylene imine and methyl methanesulfonate (MMS). These chemicals become powerful germline mutagens when the NER system is disrupted. Systematic studies of the type performed on germ cells are not available for somatic cells of Drosophila. The sparse data available show large differences in the response of germ cells and somatic cells. The bifunctional agent mechlorethamine (MEC) but not the monofunctional MMS or 2-chloroethylamine cause in NER(-) XXfemale symbol the highest potentiating effect on mitotic recombination. The causes of the discrepancy between the extraordinarily high activity of MEC in mus201 somatic cells and its low potentiating effect in germ cells is unknown at present.
Collapse
Affiliation(s)
- E W Vogel
- Department of Radiation Genetics & Chemical Mutagenesis, MGC Sylvius Laboratories, Leiden University Medical Centre, Wassenaarseweg 72, 2300 RA Leiden, The Netherlands.
| | | |
Collapse
|
30
|
Koana T, Okada MO, Takashima Y, Ikehata M, Miyakoshi J. Involvement of eddy currents in the mutagenicity of ELF magnetic fields. Mutat Res 2001; 476:55-62. [PMID: 11336983 DOI: 10.1016/s0027-5107(01)00082-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Possible carcinogenic and/or mutagenic activity of extremely low frequency magnetic fields was examined using somatic mutation and recombination test system of Drosophila melanogaster. An X-linked semi-dominant DNA repair defective mutation mei-41(D5) was introduced into the conventional mwh/flr test system to enhance mutant spot frequency. Virgin females of w mei-41(D5)/FM6; flr/TM6 were crossed with w mei-41(D5)/Y; mwh jv; spa(pol) males. The F(1) third instar larvae were exposed to a 50Hz, 20mT sinusoidal AC magnetic field for 24h. After moulting from pupal cases, their wings were examined under a bright field microscope to detect hair spots with mwh or flr mutant morphology. The exposure caused a statistically significant enhancement in somatic recombination spot frequency. Mutant spots arising due to chromosomal non-disjunction or terminal deletion also increased but the frequency of spots resulting from point mutation was not altered. The enhancement in the recombination spot frequency was suppressed to the control level when a culture medium without electrolytes was used during exposure. When larvae were exposed to a magnetic field in an annular dish, flies from the outer ring showed more mutant spots compared to those from the inner ring. These results suggest that the detected mutagenic activity was that of the induced eddy current, rather than that of the magnetic field itself.
Collapse
Affiliation(s)
- T Koana
- Environmental Biotechnology Laboratory, Railway Technical Research Institute, Hikaricho 2-8-38, Kokubunji, Tokyo 185-8540, Japan.
| | | | | | | | | |
Collapse
|
31
|
Barbosa V, Yamamoto RR, Henderson DS, Glover DM. Mutation of a Drosophila gamma tubulin ring complex subunit encoded by discs degenerate-4 differentially disrupts centrosomal protein localization. Genes Dev 2000; 14:3126-39. [PMID: 11124805 PMCID: PMC317135 DOI: 10.1101/gad.182800] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We have cloned the Drosophila gene discs degenerate-4 (dd4) and find that it encodes a component of the gamma-tubulin ring complex (gammaTuRC) homologous to Spc98 of budding yeast. This provides the first opportunity to study decreased function of a member of the gamma-tubulin ring complex, other than gamma-tubulin itself, in a metazoan cell. gamma-tubulin is no longer at the centrosomes but is dispersed throughout dd4 cells and yet bipolar metaphase spindles do form, although these have a dramatically decreased density of microtubules. Centrosomin (CNN) remains in broad discrete bodies but only at the focused poles of such spindles, whereas Asp (abnormal spindle protein) is always present at the presumptive minus ends of microtubules, whether or not they are focused. This is consistent with the proposed role of Asp in coordinating the nucleation of mitotic microtubule organizing centers. The centrosome associated protein CP190 is partially lost from the spindle poles in dd4 cells supporting a weak interaction with gamma-tubulin, and the displaced protein accumulates in the vicinity of chromosomes. Electron microscopy indicates not only that the poles of dd4 cells have irregular amounts of pericentriolar material, but also that they can have abnormal centrioles. In six dd4 cells subjected to serial sectioning centrioles were missing from one of the two poles. This suggests that in addition to its role in nucleating cytoplasmic and spindle microtubules, the gammaTuRC is also essential to the structure of centrioles and the separation of centrosomes.
Collapse
Affiliation(s)
- V Barbosa
- Cancer Research Campaign, Cell Cycle Genetics Group, University of Cambridge, Department of Genetics, Cambridge, UK
| | | | | | | |
Collapse
|
32
|
Merino ST, Cummings WJ, Acharya SN, Zolan ME. Replication-dependent early meiotic requirement for Spo11 and Rad50. Proc Natl Acad Sci U S A 2000; 97:10477-82. [PMID: 10973500 PMCID: PMC27049 DOI: 10.1073/pnas.190346097] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Spo11 and the Rad50-Mre11 complex have been indirectly implicated in processes associated with DNA replication. These proteins also have been shown to have early meiotic roles essential for the formation of a programmed DNA double-strand break known in Saccharomyces cerevisiae to initiate meiotic recombination. In both S. cerevisiae and the basidiomycete Coprinus cinereus, spo11 and rad50 mutants are defective in chromosome synapsis during meiosis. Here we demonstrate that a partial restoration of synapsis occurs in C. cinereus spo11 and rad50 mutants if premeiotic DNA replication is prevented. Double mutants were constructed with spo11-1 or rad50-4 and another mutant, spo22-1, which does not undergo premeiotic DNA replication. In both cases, we observed an increase in the percentage of nuclei containing synaptonemal complex (SC) structures, with concomitant decreases in the percentage of nuclei containing axial elements (AE) only or no structures. Both types of double mutants demonstrated significant increases in the average numbers of AE and SC, although SC-containing nuclei did not on average contain more AE than did nuclei showing no synapsis. Our results show that Spo11-induced recombination is not absolutely required for synapsis in C. cinereus, and that the early meiotic role of both Spo11 and Rad50 in SC formation partially depends on premeiotic S phase. This dependency likely reflects either a requirement for these proteins imposed by the premeiotic replication process itself or a requirement for these proteins in synapsis when a sister chromatid (the outcome of DNA replication) is present.
Collapse
Affiliation(s)
- S T Merino
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | | | | | | |
Collapse
|
33
|
Basu J, Williams BC, Li Z, Williams EV, Goldberg ML. Depletion of a Drosophila homolog of yeast Sup35p disrupts spindle assembly, chromosome segregation, and cytokinesis during male meiosis. CELL MOTILITY AND THE CYTOSKELETON 2000; 39:286-302. [PMID: 9556329 DOI: 10.1002/(sici)1097-0169(1998)39:4<286::aid-cm4>3.0.co;2-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In the course of a genetic screen for male-sterile mutations in Drosophila affecting chromosome segregation during the meiotic divisions in spermatocytes, we identified the mutation dsup35(63D). Examination of mutant testes showed that chromosome misbehavior was a consequence of major disruptions in meiotic spindle assembly. These perturbations included problems in aster formation, separation, and migration around the nuclear envelope; aberrations in spindle organization and integrity; and disappearance of the ana/telophase central spindle, which in turn disrupts cytokinesis. The dsup35(63D) mutation is caused by a P element insertion that affects, specifically in the testis, the expression of a gene (dsup35) encoding the Drosophila homolog of the yeast Sup35p and Xenopus eRF3 proteins. These proteins are involved in the termination of polypeptide synthesis on ribosomes, but previous studies have suggested that Sup35p and closely related proteins of the same family also interact directly with microtubules. An affinity-purified antibody directed against the product of the dsup35 gene was prepared; interestingly, this antibody specifically labels primary spermatocytes in one or two discrete foci of unknown structure within the nucleoplasm. We discuss how depletion of the dsup35 gene product in spermatocytes might lead to the global disruptions in meiotic spindle assembly seen in mutant spermatocytes.
Collapse
Affiliation(s)
- J Basu
- Section of Genetics and Development, Cornell University, Ithaca, New York 14853-2703, USA
| | | | | | | | | |
Collapse
|
34
|
Liu H, Jang JK, Graham J, Nycz K, McKim KS. Two genes required for meiotic recombination in Drosophila are expressed from a dicistronic message. Genetics 2000; 154:1735-46. [PMID: 10747066 PMCID: PMC1461038 DOI: 10.1093/genetics/154.4.1735] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have isolated two alleles of a previously unidentified meiotic recombination gene, mei-217. Genetic analysis of these mutants shows that mei-217 is a typical "precondition" gene. The phenotypes of the mutants are meiosis specific. The strongest allele has <10% of the normal level of crossing over, and the residual events are distributed abnormally. We have used double mutant analysis to position mei-217 in the meiotic recombination pathway. In general, mutations causing defects in the initiation of meiotic recombination are epistatic to mutations in mei-41 and spnB. These two mutations, however, are epistatic to mei-217, suggesting that recombination is initiated normally in mei-217 mutants. It is likely that mei-217 mutants are able to make Holliday junction intermediates but are defective in the production of crossovers. These phenotypes are most similar to mutants of the mei-218 gene. This is striking because mei-217 and mei-218 are part of the same transcription unit and are most likely produced from a dicistronic message.
Collapse
Affiliation(s)
- H Liu
- Waksman Institute and Department of Genetics, Rutgers University, Piscataway, New Jersey 08854-8020, USA
| | | | | | | | | |
Collapse
|
35
|
Abstract
Checkpoints block cell cycle progression in eukaryotic cells exposed to DNA damaging agents. We show that several Drosophilahomologs of checkpoint genes, mei-41, grapes, and14-3-3ε, regulate a DNA damage checkpoint in the developing eye. We have used this assay to show that the mutagen-sensitive gene mus304 is also required for this checkpoint. mus304 encodes a novel coiled-coil domain protein, which is targeted to the cytoplasm. Similar to mei-41,mus304 is required for chromosome break repair and for genomic stability. mus304 animals also exhibit three developmental defects, abnormal bristle morphology, decreased meiotic recombination, and arrested embryonic development. We suggest that these phenotypes reflect distinct developmental consequences of a single underlying checkpoint defect. Similar mechanisms may account for the puzzling array of symptoms observed in humans with mutations in the ATM tumor suppressor gene.
Collapse
|
36
|
Brodsky MH, Sekelsky JJ, Tsang G, Hawley RS, Rubin GM. mus304 encodes a novel DNA damage checkpoint protein required during Drosophila development. Genes Dev 2000; 14:666-78. [PMID: 10733527 PMCID: PMC316460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Checkpoints block cell cycle progression in eukaryotic cells exposed to DNA damaging agents. We show that several Drosophila homologs of checkpoint genes, mei-41, grapes, and 14-3-3epsilon, regulate a DNA damage checkpoint in the developing eye. We have used this assay to show that the mutagen-sensitive gene mus304 is also required for this checkpoint. mus304 encodes a novel coiled-coil domain protein, which is targeted to the cytoplasm. Similar to mei-41, mus304 is required for chromosome break repair and for genomic stability. mus304 animals also exhibit three developmental defects, abnormal bristle morphology, decreased meiotic recombination, and arrested embryonic development. We suggest that these phenotypes reflect distinct developmental consequences of a single underlying checkpoint defect. Similar mechanisms may account for the puzzling array of symptoms observed in humans with mutations in the ATM tumor suppressor gene.
Collapse
Affiliation(s)
- M H Brodsky
- Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720 USA.
| | | | | | | | | |
Collapse
|
37
|
Romanienko PJ, Camerini-Otero RD. Cloning, characterization, and localization of mouse and human SPO11. Genomics 1999; 61:156-69. [PMID: 10534401 DOI: 10.1006/geno.1999.5955] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Spo11 is a meiosis-specific protein in yeast that has been found covalently bound to DNA double-strand breaks (DSBs) during the early stages of meiosis. These DSBs initiate homologous recombination, which is required for proper segregation of chromosomes and the generation of genetic diversity during meiosis. Here we report the cloning, characterization, tissue expression, and chromosomal localization of both mouse and human homologues of Spo11. The putative mouse and human proteins are 82% identical and share approximately 25% identity with other family members. Northern blot analysis revealed testis-specific expression for both genes, but RT-PCR results showed ubiquitous expression of at least a portion of Spo11 in mouse. Human SPO11 was also detected in several somatic tissues. Mouse Spo11 was localized to chromosome 2H4, and human SPO11 was localized to chromosome 20q13.2-q13.3, a region amplified in some breast and ovarian tumors.
Collapse
Affiliation(s)
- P J Romanienko
- Genetics and Biochemistry Branch, NIDDK, National Institutes of Health,Bethesda, MD 20892, USA
| | | |
Collapse
|
38
|
Kasravi A, Walter MF, Brand S, Mason JM, Biessmann H. Molecular cloning and tissue-specific expression of the mutator2 gene (mu2) in Drosophila melanogaster. Genetics 1999; 152:1025-35. [PMID: 10388821 PMCID: PMC1460669 DOI: 10.1093/genetics/152.3.1025] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We present here the molecular cloning and characterization of the mutator2 (mu2) gene of Drosophila melanogaster together with further genetic analyses of its mutant phenotype. mu2 functions in oogenesis during meiotic recombination, during repair of radiation damage in mature oocytes, and in proliferating somatic cells, where mu2 mutations cause an increase in somatic recombination. Our data show that mu2 represents a novel component in the processing of double strand breaks (DSBs) in female meiosis. mu2 does not code for a DNA repair enzyme because mu2 mutants are not hypersensitive to DSB-inducing agents. We have mapped and cloned the mu2 gene and rescued the mu2 phenotype by germ-line transformation with genomic DNA fragments containing the mu2 gene. Sequencing its cDNA demonstrates that mu2 encodes a novel 139-kD protein, which is highly basic in the carboxy half and carries three nuclear localization signals and a helix-loop-helix domain. Consistent with the sex-specific mutant phenotype, the gene is expressed in ovaries but not in testes. During oogenesis its RNA is rapidly transported from the nurse cells into the oocyte where it accumulates specifically at the anterior margin. Expression is also prominent in diploid proliferating cells of larval somatic tissues. Our genetic and molecular data are consistent with the model that mu2 encodes a structural component of the oocyte nucleus. The MU2 protein may be involved in controlling chromatin structure and thus may influence the processing of DNA DSBs.
Collapse
Affiliation(s)
- A Kasravi
- Developmental Biology Center, University of California, Irvine, California 92697, USA
| | | | | | | | | |
Collapse
|
39
|
Abstract
Preservation of the structural integrity of DNA in any organism is crucial to its health and survival. Such preservation is achieved by an extraordinary cellular arsenal of damage surveillance and repair functions, many of which are now being defined at the gene and protein levels. Mutants hypersensitive to the killing effects of DNA-damaging agents have been instrumental in helping to identify DNA repair-related genes and to elucidate repair mechanisms. In Drosophila melanogaster, such strains are generally referred to as mutagen-sensitive (mus) mutants and currently define more than 30 genetic loci. Whereas most mus mutants have been recovered on the basis of hypersensitivity to the monofunctional alkylating agent methyl methanesulfonate, they nevertheless constitute a phenotypically diverse group, with many mutants having effects beyond mutagen sensitivity. These phenotypes include meiotic dysfunctions, somatic chromosome instabilities, chromatin abnormalities, and cell proliferation defects. Within the last few years numerous mus and other DNA repair-related genes of Drosophila have been molecularly cloned, providing new insights into the functions of these genes. This article outlines strategies for isolating mus mutations and reviews recent advances in the Drosophila DNA repair field, emphasizing mutant analysis and gene cloning.
Collapse
Affiliation(s)
- D S Henderson
- Department of Anatomy and Physiology, University of Dundee, Dundee, DD1 4HN, Scotland, United Kingdom
| |
Collapse
|
40
|
Sekelsky JJ, McKim KS, Messina L, French RL, Hurley WD, Arbel T, Chin GM, Deneen B, Force SJ, Hari KL, Jang JK, Laurençon AC, Madden LD, Matthies HJ, Milliken DB, Page SL, Ring AD, Wayson SM, Zimmerman CC, Hawley RS. Identification of novel Drosophila meiotic genes recovered in a P-element screen. Genetics 1999; 152:529-42. [PMID: 10353897 PMCID: PMC1460643 DOI: 10.1093/genetics/152.2.529] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The segregation of homologous chromosomes from one another is the essence of meiosis. In many organisms, accurate segregation is ensured by the formation of chiasmata resulting from crossing over. Drosophila melanogaster females use this type of recombination-based system, but they also have mechanisms for segregating achiasmate chromosomes with high fidelity. We describe a P-element mutagenesis and screen in a sensitized genetic background to detect mutations that impair meiotic chromosome pairing, recombination, or segregation. Our screen identified two new recombination-deficient mutations: mei-P22, which fully eliminates meiotic recombination, and mei-P26, which decreases meiotic exchange by 70% in a polar fashion. We also recovered an unusual allele of the ncd gene, whose wild-type product is required for proper structure and function of the meiotic spindle. However, the screen yielded primarily mutants specifically defective in the segregation of achiasmate chromosomes. Although most of these are alleles of previously undescribed genes, five were in the known genes alphaTubulin67C, CycE, push, and Trl. The five mutations in known genes produce novel phenotypes for those genes.
Collapse
Affiliation(s)
- J J Sekelsky
- Department of Genetics, Section of Molecular and Cellular Biology, University of California, Davis, California 95616, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
McKim KS, Hayashi-Hagihara A. mei-W68 in Drosophila melanogaster encodes a Spo11 homolog: evidence that the mechanism for initiating meiotic recombination is conserved. Genes Dev 1998; 12:2932-42. [PMID: 9744869 PMCID: PMC317166 DOI: 10.1101/gad.12.18.2932] [Citation(s) in RCA: 226] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Meiotic recombination requires the action of several gene products in both Saccharomyces cerevisiae and Drosophila melanogaster. Genetic studies in D. melanogaster have shown that the mei-W68 gene is required for all meiotic gene conversion and crossing-over. We cloned mei-W68 using a new genetic mapping method in which P elements are used to promote crossing-over at their insertion sites. This resulted in the high-resolution mapping of mei-W68 to a <18-kb region that contains a homolog of the S. cerevisiae spo11 gene. Molecular analysis of several mutants confirmed that mei-W68 encodes an spo11 homolog. Spo11 and MEI-W68 are members of a family of proteins similar to a novel type II topoisomerase. On the basis of this and other lines of evidence, Spo11 has been proposed to be the enzymatic activity that creates the double-strand breaks needed to initiate meiotic recombination. This raises the possibility that recombination in Drosophila is also initiated by double-strand breaks. Although these homologous genes are required absolutely for recombination in both species, their roles differ in other respects. In contrast to spo11, mei-W68 is not required for synaptonemal complex formation and does have a mitotic role.
Collapse
Affiliation(s)
- K S McKim
- Waksman Institute, Rutgers University, Piscataway, New Jersey 08854-8020, USA.
| | | |
Collapse
|
42
|
Beumer KJ, Pimpinelli S, Golic KG. Induced chromosomal exchange directs the segregation of recombinant chromatids in mitosis of Drosophila. Genetics 1998; 150:173-88. [PMID: 9725837 PMCID: PMC1460302 DOI: 10.1093/genetics/150.1.173] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In meiosis, the segregation of chromosomes at the reductional division is accomplished by first linking homologs together. Genetic exchange generates the bivalents that direct regular chromosome segregation. We show that genetic exchange in mitosis also generates bivalents and that these bivalents direct mitotic chromosome segregation. After FLP-mediated homologous recombination in G2 of the cell cycle, recombinant chromatids consistently segregate away from each other (x segregation). This pattern of segregation also applies to exchange between heterologs. Most, or all, cases of non-x segregation are the result of exchange in G1. Cytological evidence is presented that confirms the existence of the bivalents that direct this pattern of segregation. Our results implicate sister chromatid cohesion in maintenance of the bivalent. The pattern of chromatid segregation can be altered by providing an additional FRT at a more proximal site on one chromosome. We propose that sister chromatid exchange occurs at the more proximal site, allowing the recombinant chromatids to segregate together. This also allowed the recovery of reciprocal translocations following FLP-mediated heterologous recombination. The observation that exchange can generate a bivalent in mitotic divisions provides support for a simple evolutionary relationship between mitosis and meiosis.
Collapse
Affiliation(s)
- K J Beumer
- Department of Biology, University of Utah, Salt Lake City, Utah 84112, USA
| | | | | |
Collapse
|
43
|
Sekelsky JJ, Burtis KC, Hawley RS. Damage control: the pleiotropy of DNA repair genes in Drosophila melanogaster. Genetics 1998; 148:1587-98. [PMID: 9560378 PMCID: PMC1460071 DOI: 10.1093/genetics/148.4.1587] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Affiliation(s)
- J J Sekelsky
- Department of Genetics, Section of Molecular and Cellular Biology, University of California, Davis 95616, USA
| | | | | |
Collapse
|
44
|
Abstract
The knowledge about the existence of different pathways for the repairing of DNA lesions has made possible a better understanding of mutation processes. The double mutant method has been shown to be useful for grouping rad mutants in yeast. Through this method, three different groups of repair mechanisms were found: (a) RAD3 group corresponding to the excision repair of UV lesions, (b) RAD6 group corresponding to the translesion type of post-replication repair and (c) RAD52 group corresponding to the recombination type of post-replication repair. In this work, a search for a classification of Drosophila mus mutants in groups analogous to yeast RAD groups is done. Information obtained by double mutant studies was integrated with that obtained by biochemical, recombination, DNA damaging agent sensitivity and mutation studies. The following groups were found: (a) group of mei9 and mus201, analogous to RAD3, (b) group of mei41 and mus302 analogous to RAD52 and, (c) group of mus104 and mus101 analogous to RAD6. In addition, there are mutants that belong to a group corresponding to pre-replication repair of MMS lesions such as mus103, mus306 and mus207. As a peculiarity of Drosophila, it was found that interaction between pre- and post-replication repair mechanisms is indifferent and not synergistic as was found in yeast. A possible explanation could be a weaker control of post-replication repair mechanisms in Drosophila than in yeast. It is expected that this research could help for a better understanding of repair mechanisms in complex organisms.
Collapse
Affiliation(s)
- P G de Buendía
- Instituto de Genetica, Universidad de los Andes, Bogotá, Colombia.
| |
Collapse
|
45
|
Sargent RG, Rolig RL, Kilburn AE, Adair GM, Wilson JH, Nairn RS. Recombination-dependent deletion formation in mammalian cells deficient in the nucleotide excision repair gene ERCC1. Proc Natl Acad Sci U S A 1997; 94:13122-7. [PMID: 9371810 PMCID: PMC24273 DOI: 10.1073/pnas.94.24.13122] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Nucleotide excision repair proteins have been implicated in genetic recombination by experiments in Saccharomyces cerevisiae and Drosophila melanogaster, but their role, if any, in mammalian cells is undefined. To investigate the role of the nucleotide excision repair gene ERCC1, the hamster homologue to the S. cerevisiae RADIO gene, we disabled the gene by targeted knockout. Partial tandem duplications of the adenine phosphoribosyltransferase (APRT) gene then were constructed at the endogenous APRT locus in ERCC1- and ERCC1+ cells. To detect the full spectrum of gene-altering events, we used a loss-of-function assay in which the parental APRT+ tandem duplication could give rise to APRT- cells by homologous recombination, gene rearrangement, or point mutation. Measurement of rates and analysis of individual APRT- products indicated that gene rearrangements (principally deletions) were increased at least 50-fold, whereas homologous recombination was affected little. The formation of deletions is not caused by a general effect of the ERCC1 deficiency on gene stability, because ERCC1- cell lines with a single wild-type copy of the APRT gene yielded no increase in deletions. Thus, deletion formation is dependent on the tandem duplication, and presumably the process of homologous recombination. Recombination-dependent deletion formation in ERCC1- cells is supported by a significant decrease in a particular class of crossover products that are thought to arise by repair of a heteroduplex intermediate in recombination. We suggest that the ERCC1 gene product in mammalian cells is involved in the processing of heteroduplex intermediates in recombination and that the misprocessed intermediates in ERCC1- cells are repaired by illegitimate recombination.
Collapse
Affiliation(s)
- R G Sargent
- The Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030, USA
| | | | | | | | | | | |
Collapse
|
46
|
Abstract
The development of a normal cell into a tumor cell appears to depend in part on mutations in genes that normally control cell cycle and cell death, thereby resulting in inappropriate cellular survival and tumorigenesis. ATM ("mutated in ataxia-telangiectasia") and p53 are two gene products that are believed to play a major role in maintaining the integrity of the genome such that alterations in these gene products may contribute to increased incidence of genomic changes such as deletions, translocations, and amplifications, which are common during oncogenesis. p53 is a critical participant in a signal transduction pathway that mediates either a G1 arrest or apoptosis in response to DNA damage. In addition, p53 is believed to be involved in the mitotic spindle checkpoint and in the regulation of centrosome function. Following certain cytotoxic stresses, normal ATM function is required for p53-mediated G1 arrest. ATM is also involved in other cellular processes such as S phase and G2-M phase arrest and in radiosensitivity. The understanding of the roles that both p53 and ATM play in cell cycle progression and cell death in response to DNA damage may provide new insights into the molecular mechanisms of cellular transformation and may help identify potential targets for improved cancer therapies.
Collapse
Affiliation(s)
- S E Morgan
- Johns Hopkins Oncology Center, Baltimore, Maryland 21205, USA
| | | |
Collapse
|
47
|
Hawley RS, Friend SH. Strange bedfellows in even stranger places: the role of ATM in meiotic cells, lymphocytes, tumors, and its functional links to p53. Genes Dev 1996; 10:2383-8. [PMID: 8843191 DOI: 10.1101/gad.10.19.2383] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- R S Hawley
- Department of Genetics, University of California at Davis, 95616, USA
| | | |
Collapse
|
48
|
McKim KS, Dahmus JB, Hawley RS. Cloning of the Drosophila melanogaster meiotic recombination gene mei-218: a genetic and molecular analysis of interval 15E. Genetics 1996; 144:215-28. [PMID: 8878687 PMCID: PMC1207495 DOI: 10.1093/genetics/144.1.215] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The mei-218 gene product is required for both meiotic crossing over and for the production of recombination modules, suggesting that these organelles are required for meiotic exchange. In this study the null phenotype of mei-218 was defined through the analysis of three preexisting and five new alleles. Consistent with previous studies, in homozygous mei-218 mutants meiotic crossing over is reduced to < 10% of normal levels. A molecular analysis of mei-218 was initiated with the isolation and mapping of lethal mutations and genome rearrangements in the region containing mei-218, polytene interval 15E on the X chromosome. This high resolution genetic map was aligned with a physical map constructed from cosmid and P1 clones by genetically mapping restriction fragment length polymorphisms and localizing rearrangement breakpoints. Within a region of 65 kb, we have identified seven transcription units, including mei-218 and the Minute(1)15D gene, which encodes ribosomal protein S5. The mei-218 mutant phenotype has been rescued by germline transformation with both a genomic fragment and a cDNA under the control of the hsp83 promoter. The mei-218 gene is predicted to produce an 1186-amino acid protein that has no significant similarities to any known proteins.
Collapse
Affiliation(s)
- K S McKim
- Section of Molecular and Cellular Biology, University of California, Davis 95616, USA
| | | | | |
Collapse
|
49
|
Rodriguez-Arnaiz R, Soto PO, Oyarzún JC, Graf U. Analysis of mitotic recombination induced by several mono- and bifunctional alkylating agents in the Drosophila wing-spot test. Mutat Res 1996; 351:133-45. [PMID: 8622707 DOI: 10.1016/0027-5107(95)00217-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Mitotic recombination induced by six alkylating agents has been studied in the wing-spot test of Drosophila melanogaster. The model mutagens chosen have different models of action at the DNA level. These are: the direct-acting small alkylating agent methylmethanesulfonate (MMS), the small promutagens N-dimethylnitrosamine (DMN) and N-diethylnitrosamine (DEN), the bifunctional cross-linking alkylating agents mitomycin C (MMC), chlorambucil (CLA) and monocrotaline (MCT). Flies of the standard cross (flr3 / TM3, Bds females and mwh males) were used to produce the larvae to be treated. Three-day old Drosophila larvae were exposed by chronic feeding for 48 h to three different concentrations of all six alkylating agents. Acute feeding for only 2 h was used in addition with DEN and MMC. Wings of the marker-heterozygous (mwh+ / + flr3) as well as of the balancer-heterozygous (mwh+ / TM3, Bds) progeny were analysed. The ranking of the compounds with respect to their genotoxic potency, based on mwh clone formation frequency in marker-heterozygous wings was: MMS > MNC > DMN > CLA approximately MCT > DEN. The ranking with respect to the induction of twin spots, which are produced by mitotic recombination exclusively, was: MMS > DMN > MMC > MCT > CLA > DEN. The quantitative determination of recombinagenic activity, based on mwh clone formation frequencies obtained in both types of wings, gave the following values: MMS, 93%; MCT, 87%; CLA, 80%; MMC, 73%; DMN, 67%; DEN, 22%. A clear relationship exists between the extent of N-alkylation of DNA and the efficiency of the monofunctional agents MMS and DMN as well of the bifunctional agents MCT, CLA and MMC to induce mitotic recombination. This contrasts with the ethylation of base oxygen atoms and the resulting lower efficiency of DEN to produce mitotic recombination.
Collapse
Affiliation(s)
- R Rodriguez-Arnaiz
- Laboratorio de Genética, Fakultad de Ciencias, Universidad Nacional Autónoma de México, D.F., Mexico
| | | | | | | |
Collapse
|
50
|
Kerrebrock AW, Moore DP, Wu JS, Orr-Weaver TL. Mei-S332, a Drosophila protein required for sister-chromatid cohesion, can localize to meiotic centromere regions. Cell 1995; 83:247-56. [PMID: 7585942 DOI: 10.1016/0092-8674(95)90166-3] [Citation(s) in RCA: 183] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Mutations in the Drosophila mei-S332 gene cause premature separation of the sister chromatids in late anaphase of meiosis I. Therefore, the mei-S332 protein was postulated to hold the centromere regions of sister chromatids together until anaphase II. The mei-S332 gene encodes a novel 44 kDa protein. Mutations in mei-S332 that differentially affect function in males or females map to distinct domains of the protein. A fusion of mei-S332 to the green fluorescent protein (GFP) is fully functional and localizes specifically to the centromere region of meiotic chromosomes. When sister chromatids separate at anaphase II, mei-S332-GFP disappears from the chromosomes, suggesting that the destruction or release of this protein is required for sister-chromatid separation.
Collapse
Affiliation(s)
- A W Kerrebrock
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA
| | | | | | | |
Collapse
|