1
|
Division of Labor by the HELQ, BLM, and FANCM Helicases during Homologous Recombination Repair in Drosophila melanogaster. Genes (Basel) 2022; 13:genes13030474. [PMID: 35328029 PMCID: PMC8951532 DOI: 10.3390/genes13030474] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 03/02/2022] [Accepted: 03/07/2022] [Indexed: 02/01/2023] Open
Abstract
Repair of DNA double-strand breaks by homologous recombination (HR) requires a carefully orchestrated sequence of events involving many proteins. One type of HR, synthesis-dependent strand annealing (SDSA), proceeds via the formation of a displacement loop (D-loop) when RAD51-coated single-stranded DNA invades a homologous template. The 3' end of the single-stranded DNA is extended by DNA synthesis. In SDSA, the D-loop is then disassembled prior to strand annealing. While many helicases can unwind D-loops in vitro, how their action is choreographed in vivo remains to be determined. To clarify the roles of various DNA helicases during SDSA, we used a double-strand gap repair assay to study the outcomes of homologous recombination repair in Drosophila melanogaster lacking the BLM, HELQ, and FANCM helicases. We found that the absence of any of these three helicases impairs gap repair. In addition, flies lacking both BLM and HELQ or HELQ and FANCM had more severe SDSA defects than the corresponding single mutants. In the absence of BLM, a large percentage of repair events were accompanied by flanking deletions. Strikingly, these deletions were mostly abolished in the blm helq and blm fancm double mutants. Our results suggest that the BLM, HELQ, and FANCM helicases play distinct roles during SDSA, with HELQ and FANCM acting early to promote the formation of recombination intermediates that are then processed by BLM to prevent repair by deletion-prone mechanisms.
Collapse
|
2
|
Mitchell C, Becker V, DeLoach J, Nestore E, Bolterstein E, Kohl KP. The Drosophila Mutagen-Sensitivity Gene mus109 Encodes DmDNA2. Genes (Basel) 2022; 13:genes13020312. [PMID: 35205357 PMCID: PMC8872385 DOI: 10.3390/genes13020312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Revised: 02/02/2022] [Accepted: 02/04/2022] [Indexed: 02/05/2023] Open
Abstract
The identification of mutants through forward genetic screens is the backbone of Drosophila genetics research, yet many mutants identified through these screens have yet to be mapped to the Drosophila genome. This is especially true of mutants that have been identified as mutagen-sensitive (mus), but have not yet been mapped to their associated molecular locus. Our study addressed the need for additional mus gene identification by determining the locus and exploring the function of the X-linked mutagen-sensitive gene mus109 using three available mutant alleles: mus109D1, mus109D2, and mus109lS. After first confirming that all three mus109 alleles were sensitive to methyl methanesulfonate (MMS) using complementation analysis, we used deletion mapping to narrow the candidate genes for mus109. Through DNA sequencing, we were able to determine that mus109 is the uncharacterized gene CG2990, which encodes the Drosophila ortholog of the highly conserved DNA2 protein that is important for DNA replication and repair. We further used the sequence and structure of DNA2 to predict the impact of the mus109 allele mutations on the final gene product. Together, these results provide a tool for researchers to further investigate the role of DNA2 in DNA repair processes in Drosophila.
Collapse
Affiliation(s)
- Chandani Mitchell
- Biology Department, Winthrop University, Rock Hill, SC 29733, USA; (C.M.); (J.D.); (E.N.)
| | - Vada Becker
- Biology Department, Northeastern Illinois University, Chicago, IL 60625, USA; (V.B.); (E.B.)
| | - Jordan DeLoach
- Biology Department, Winthrop University, Rock Hill, SC 29733, USA; (C.M.); (J.D.); (E.N.)
| | - Erica Nestore
- Biology Department, Winthrop University, Rock Hill, SC 29733, USA; (C.M.); (J.D.); (E.N.)
| | - Elyse Bolterstein
- Biology Department, Northeastern Illinois University, Chicago, IL 60625, USA; (V.B.); (E.B.)
| | - Kathryn P. Kohl
- Biology Department, Winthrop University, Rock Hill, SC 29733, USA; (C.M.); (J.D.); (E.N.)
- Correspondence:
| |
Collapse
|
3
|
Yang Q, Mumusoglu S, Qin Y, Sun Y, Hsueh AJ. A kaleidoscopic view of ovarian genes associated with premature ovarian insufficiency and senescence. FASEB J 2021; 35:e21753. [PMID: 34233068 DOI: 10.1096/fj.202100756r] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 06/04/2021] [Accepted: 06/08/2021] [Indexed: 12/14/2022]
Abstract
Ovarian infertility and subfertility presenting with premature ovarian insufficiency (POI) and diminished ovarian reserve are major issues facing the developed world due to the trend of delaying childbirth. Ovarian senescence and POI represent a continuum of physiological/pathophysiological changes in ovarian follicle functions. Based on advances in whole exome sequencing, evaluation of gene copy variants, together with family-based and genome-wide association studies, we discussed genes responsible for POI and ovarian senescence. We used a gene-centric approach to sort out literature deposited in the Ovarian Kaleidoscope database (http://okdb.appliedbioinfo.net) by sub-categorizing candidate genes as ligand-receptor signaling, meiosis and DNA repair, transcriptional factors, RNA metabolism, enzymes, and others. We discussed individual gene mutations found in POI patients and verification of gene functions in gene-deleted model organisms. Decreased expression of some of the POI genes could be responsible for ovarian senescence, especially those essential for DNA repair, meiosis and mitochondrial functions. We propose to set up a candidate gene panel for targeted sequencing in POI patients together with studies on mitochondria-associated genes in middle-aged subfertile patients.
Collapse
Affiliation(s)
- Qingling Yang
- Center for Reproductive Medicine, Henan Key Laboratory of Reproduction and Genetics, First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, CA, USA
| | - Sezcan Mumusoglu
- Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Obstetrics and Gynecology, Hacettepe University School of Medicine, Ankara, Turkey
| | - Yingying Qin
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Yingpu Sun
- Center for Reproductive Medicine, Henan Key Laboratory of Reproduction and Genetics, First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Aaron J Hsueh
- Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, CA, USA
| |
Collapse
|
4
|
Rieckher M, Garinis GA, Schumacher B. Molecular pathology of rare progeroid diseases. Trends Mol Med 2021; 27:907-922. [PMID: 34272172 DOI: 10.1016/j.molmed.2021.06.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 06/18/2021] [Accepted: 06/22/2021] [Indexed: 12/21/2022]
Abstract
Progeroid syndromes (PSs) are characterized by the premature onset of age-related pathologies. The genetic mutations underlying PSs are functionally linked to genome maintenance and repair, supporting the causative role of DNA damage accumulation in aging. Recent advances from studies in animal models of PSs have provided new insight into the role of DNA repair mechanisms in human disease and the physiological adaptations to accumulating DNA damage during aging. The molecular pathology of PSs is reminiscent of the natural aging process, highlighting the relevance for a wide range of age-related diseases. Recent progress has led to the development of novel therapeutic strategies against age-related diseases that are relevant to rare diseases as well as the general aging population.
Collapse
Affiliation(s)
- Matthias Rieckher
- Institute for Genome Stability in Aging and Disease, Medical Faculty, University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Center for Molecular Medicine (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - George A Garinis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, GR70013, Heraklion, Crete, Greece; Department of Biology, University of Crete, Heraklion, Crete, Greece
| | - Björn Schumacher
- Institute for Genome Stability in Aging and Disease, Medical Faculty, University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Center for Molecular Medicine (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany.
| |
Collapse
|
5
|
Transcriptomic profiling of the digestive tract of the rat flea, Xenopsylla cheopis, following blood feeding and infection with Yersinia pestis. PLoS Negl Trop Dis 2020; 14:e0008688. [PMID: 32946437 PMCID: PMC7526888 DOI: 10.1371/journal.pntd.0008688] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 09/30/2020] [Accepted: 08/10/2020] [Indexed: 01/29/2023] Open
Abstract
Yersinia pestis, the causative agent of plague, is a highly lethal pathogen transmitted by the bite of infected fleas. Once ingested by a flea, Y. pestis establish a replicative niche in the gut and produce a biofilm that promotes foregut colonization and transmission. The rat flea Xenopsylla cheopis is an important vector to several zoonotic bacterial pathogens including Y. pestis. Some fleas naturally clear themselves of infection; however, the physiological and immunological mechanisms by which this occurs are largely uncharacterized. To address this, RNA was extracted, sequenced, and distinct transcript profiles were assembled de novo from X. cheopis digestive tracts isolated from fleas that were either: 1) not fed for 5 days; 2) fed sterile blood; or 3) fed blood containing ~5x108 CFU/ml Y. pestis KIM6+. Analysis and comparison of the transcript profiles resulted in identification of 23 annotated (and 11 unknown or uncharacterized) digestive tract transcripts that comprise the early transcriptional response of the rat flea gut to infection with Y. pestis. The data indicate that production of antimicrobial peptides regulated by the immune-deficiency pathway (IMD) is the primary flea immune response to infection with Y. pestis. The remaining infection-responsive transcripts, not obviously associated with the immune response, were involved in at least one of 3 physiological themes: 1) alterations to chemosensation and gut peristalsis; 2) modification of digestion and metabolism; and 3) production of chitin-binding proteins (peritrophins). Despite producing several peritrophin transcripts shortly after feeding, including a subset that were infection-responsive, no thick peritrophic membrane was detectable by histochemistry or electron microscopy of rat flea guts for the first 24 hours following blood-feeding. Here we discuss the physiological implications of rat flea infection-responsive transcripts, the function of X. cheopis peritrophins, and the mechanisms by which Y. pestis may be cleared from the flea gut. The goal of this study was to characterize the transcriptional response of the digestive tract of the rat flea, Xenopsylla cheopis, to infection with Yersinia pestis, the causative agent of plague. This flea is generally considered the most prevalent and efficient vector of Y. pestis. Because most pathogens transmitted by fleas, including Y. pestis, reside in the insect digestive tract prior to transmission, the transcriptional program induced in the gut epithelium likely influences bacterial colonization of the flea. To determine the specific response to infection, RNA profiles were generated from fleas that were either unfed, fed sterile blood, or fed blood containing Y. pestis. Comparative analyses of the transcriptomes resulted in identification of 34 infection-responsive transcripts. The functions of these differentially regulated genes indicate that infection of fleas with Y. pestis induces a limited immune response and potentially alters the insect’s behavior, metabolism, and other aspects of its physiology. Based on these data, we describe potential mechanisms fleas use to eliminate bacteria and the corresponding strategies Y. pestis uses to resist elimination. These findings may be helpful for developing targeted strategies to make fleas resistant to microbial infection and thereby reduce the incidence of diseases they spread.
Collapse
|
6
|
The Drosophila melanogaster Ortholog of RFWD3 Functions Independently of RAD51 During DNA Repair. G3-GENES GENOMES GENETICS 2020; 10:999-1004. [PMID: 31900333 PMCID: PMC7056982 DOI: 10.1534/g3.119.400903] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Repair of damaged DNA is required for the viability of all organisms. Studies in Drosophila melanogaster, driven by the power of genetic screens, pioneered the discovery and characterization of many genes and pathways involved in DNA repair in animals. However, fewer than half of the alleles identified in these screens have been mapped to a specific gene, leaving a potential for new discoveries in this field. Here we show that the previously uncharacterized mutagen sensitive gene mus302 codes for the Drosophila melanogaster ortholog of the E3 ubiquitin ligase RING finger and WD domain protein 3 (RFWD3). In human cells, RFWD3 promotes ubiquitylation of RPA and RAD51 to facilitate repair of collapsed replication forks and double-strand breaks through homologous recombination. Despite the high similarity in sequence to the human ortholog, our evidence fails to support a role for Mus302 in the repair of these types of damage. Last, we observe that the N-terminal third of RFWD3 is only found in mammals, but not in other vertebrates or invertebrates. We propose that the new N-terminal sequence accounts for the acquisition of a new biological function in mammals that explains the functional differences between the human and the fly orthologs, and that Drosophila Mus302 may retain the ancestral function of the protein.
Collapse
|
7
|
Koval L, Proshkina E, Shaposhnikov M, Moskalev A. The role of DNA repair genes in radiation-induced adaptive response in Drosophila melanogaster is differential and conditional. Biogerontology 2019; 21:45-56. [PMID: 31624983 DOI: 10.1007/s10522-019-09842-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 10/04/2019] [Indexed: 12/13/2022]
Abstract
Studies in human and mammalian cell cultures have shown that induction of DNA repair mechanisms is required for the formation of stimulation effects of low doses of ionizing radiation, named "hormesis". Nevertheless, the role of cellular defense mechanisms in the formation of radiation-induced hormesis at the level of whole organism remains poorly studied. The aim of this work was to investigate the role of genes involved in different mechanisms and stages of DNA repair in radioadaptive response and radiation hormesis by lifespan parameters in Drosophila melanogaster. We studied genes that control DNA damage sensing (D-Gadd45, Hus1, mnk), nucleotide excision repair (mei-9, mus210, Mus209), base excision repair (Rrp1), DNA double-stranded break repair by homologous recombination (Brca2, spn-B, okr) and non-homologous end joining (Ku80, WRNexo), and the Mus309 gene that participates in several mechanisms of DNA repair. The obtained results demonstrate that in flies with mutations in studied genes radioadaptive response and radiation hormesis are absent or appear to a lesser extent than in wild-type Canton-S flies. Chronic exposure of γ-radiation in a low dose during pre-imaginal stages of development leads to an increase in expression of the studied DNA repair genes, which is maintained throughout the lifespan of flies. However, the activation of conditional ubiquitous overexpression of DNA repair genes does not induce resistance to an acute exposure to γ-radiation and reinforces its negative impact.
Collapse
Affiliation(s)
- Liubov Koval
- Laboratory of Geroprotective and Radioprotective Technologies, Institute of Biology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Komi Republic, Russian Federation, 167982
- Pitirim Sorokin Syktyvkar State University, Syktyvkar, Komi Republic, Russian Federation, 167000
| | - Ekaterina Proshkina
- Laboratory of Geroprotective and Radioprotective Technologies, Institute of Biology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Komi Republic, Russian Federation, 167982
| | - Mikhail Shaposhnikov
- Laboratory of Geroprotective and Radioprotective Technologies, Institute of Biology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Komi Republic, Russian Federation, 167982
- Pitirim Sorokin Syktyvkar State University, Syktyvkar, Komi Republic, Russian Federation, 167000
| | - Alexey Moskalev
- Laboratory of Geroprotective and Radioprotective Technologies, Institute of Biology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Komi Republic, Russian Federation, 167982.
- Pitirim Sorokin Syktyvkar State University, Syktyvkar, Komi Republic, Russian Federation, 167000.
- Laboratory of Post-Genomic Research, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russian Federation, 119991.
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russian Federation, 141701.
| |
Collapse
|
8
|
Ji J, Tang X, Hu W, Maggert KA, Rong YS. The processivity factor Pol32 mediates nuclear localization of DNA polymerase delta and prevents chromosomal fragile site formation in Drosophila development. PLoS Genet 2019; 15:e1008169. [PMID: 31100062 PMCID: PMC6542543 DOI: 10.1371/journal.pgen.1008169] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 05/30/2019] [Accepted: 04/30/2019] [Indexed: 12/29/2022] Open
Abstract
The Pol32 protein is one of the universal subunits of DNA polymerase δ (Pol δ), which is responsible for genome replication in eukaryotic cells. Although the role of Pol32 in DNA repair has been well-characterized, its exact function in genome replication remains obscure as studies in single cell systems have not established an essential role for Pol32 in the process. Here we characterize Pol32 in the context of Drosophila melanogaster development. In the rapidly dividing embryonic cells, loss of Pol32 halts genome replication as it specifically disrupts Pol δ localization to the nucleus. This function of Pol32 in facilitating the nuclear import of Pol δ would be similar to that of accessory subunits of DNA polymerases from mammalian Herpes viruses. In post-embryonic cells, loss of Pol32 reveals mitotic fragile sites in the Drosophila genome, a defect more consistent with Pol32’s role as a polymerase processivity factor. Interestingly, these fragile sites do not favor repetitive sequences in heterochromatin, with the rDNA locus being a striking exception. Our study uncovers a possibly universal function for DNA polymerase ancillary factors and establishes a powerful system for the study of chromosomal fragile sites in a non-mammalian organism. Cancer etiological studies suggest that the majority of pathological mutations occurred under near normal DNA replication conditions, emphasizing the importance of understanding replication regulation under non-lethal conditions. To gain such a better understanding, we investigated the function of Pol32, a conserved ancillary subunit of the essential DNA polymerase Delta complex, through the development of the fruit fly Drosophila. We uncovered a previously unappreciated function of Pol32 in regulating the nuclear import of the polymerase complex, and this function is developmentally regulated. By utilizing mutations in pol32 and other replication factors, we have started to define basic features of Chromosome Fragile Sites (CFS) in Drosophila somatic cells. CFS is a major source of genome instability associated with replication stresses, and has been an important topic of cancer biology. We discovered that CFS formation does not favor genomic regions with repetitive sequences except the highly transcribed locus encoding ribosomal RNA. Our work lays the groundwork for future studies using Drosophila as an alternative system to uncover the most fundamental features of CFS.
Collapse
Affiliation(s)
- Jingyun Ji
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Xiaona Tang
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Wen Hu
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Keith A. Maggert
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, United States of America
| | - Yikang S. Rong
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
- * E-mail:
| |
Collapse
|
9
|
The Role of Blm Helicase in Homologous Recombination, Gene Conversion Tract Length, and Recombination Between Diverged Sequences in Drosophilamelanogaster. Genetics 2017; 207:923-933. [PMID: 28912341 DOI: 10.1534/genetics.117.300285] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 09/10/2017] [Indexed: 11/18/2022] Open
Abstract
DNA double-strand breaks (DSBs) are a particularly deleterious class of DNA damage that threatens genome integrity. DSBs are repaired by three pathways: nonhomologous-end joining (NHEJ), homologous recombination (HR), and single-strand annealing (SSA). Drosophila melanogaster Blm (DmBlm) is the ortholog of Saccharomyces cerevisiae SGS1 and human BLM, and has been shown to suppress crossovers in mitotic cells and repair mitotic DNA gaps via HR. To further elucidate the role of DmBlm in repair of a simple DSB, and in particular recombination mechanisms, we utilized the Direct Repeat of white (DR-white) and Direct Repeat of whitewith mutations (DR-white.mu) repair assays in multiple mutant allele backgrounds. DmBlm null and helicase-dead mutants both demonstrated a decrease in repair by noncrossover HR, and a concurrent increase in non-HR events, possibly including SSA, crossovers, deletions, and NHEJ, although detectable processing of the ends was not significantly impacted. Interestingly, gene conversion tract lengths of HR repair events were substantially shorter in DmBlm null but not helicase-dead mutants, compared to heterozygote controls. Using DR-white.mu, we found that, in contrast to Sgs1, DmBlm is not required for suppression of recombination between diverged sequences. Taken together, our data suggest that DmBlm helicase function plays a role in HR, and the steps that contribute to determining gene conversion tract length are helicase-independent.
Collapse
|
10
|
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: 79] [Impact Index Per Article: 11.3] [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
|
11
|
Cunniff C, Bassetti JA, Ellis NA. Bloom's Syndrome: Clinical Spectrum, Molecular Pathogenesis, and Cancer Predisposition. Mol Syndromol 2017; 8:4-23. [PMID: 28232778 PMCID: PMC5260600 DOI: 10.1159/000452082] [Citation(s) in RCA: 160] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/22/2016] [Indexed: 01/07/2023] Open
Abstract
Bloom's syndrome is an autosomal recessive disorder characterized by prenatal and postnatal growth deficiency, photosensitive skin changes, immune deficiency, insulin resistance, and a greatly increased risk of early onset of cancer and for the development of multiple cancers. Loss-of-function mutations of BLM, which codes for a RecQ helicase, cause Bloom's syndrome. The absence of a functional BLM protein causes chromosome instability, excessive homologous recombination, and a greatly increased number of sister chromatid exchanges that are pathognomonic of the syndrome. A common founder mutation designated blmAsh is present in about 1 in 100 persons of Eastern European Jewish ancestry, and there are additional recurrent founder mutations among other populations. Missense, nonsense, and frameshift mutations as well as multiexonic deletions have all been observed. Bloom's syndrome is a prototypical chromosomal instability syndrome, and the somatic mutations that occur as a result of that instability are responsible for the increased cancer risk. Although there is currently no treatment aimed at the underlying genetic abnormality, persons with Bloom's syndrome benefit from sun protection, aggressive treatment of infections, surveillance for insulin resistance, and early identification of cancer.
Collapse
Affiliation(s)
- Christopher Cunniff
- Division of Medical Genetics, Department of Pediatrics, Weill Cornell Medical College, New York, N.Y, USA
| | - Jennifer A. Bassetti
- Division of Medical Genetics, Department of Pediatrics, Weill Cornell Medical College, New York, N.Y, USA
| | - Nathan A. Ellis
- Department of Cellular and Molecular Medicine, University of Arizona Cancer Center, Tucson, Ariz., USA
| |
Collapse
|
12
|
A Role for the Twins Protein Phosphatase (PP2A-B55) in the Maintenance of Drosophila Genome Integrity. Genetics 2016; 205:1151-1167. [PMID: 28040742 DOI: 10.1534/genetics.116.192781] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 12/21/2016] [Indexed: 01/14/2023] Open
Abstract
The protein phosphatase 2A (PP2A) is a conserved heterotrimeric enzyme that regulates several cellular processes including the DNA damage response and mitosis. Consistent with these functions, PP2A is mutated in many types of cancer and acts as a tumor suppressor. In mammalian cells, PP2A inhibition results in DNA double strand breaks (DSBs) and chromosome aberrations (CABs). However, the mechanisms through which PP2A prevents DNA damage are still unclear. Here, we focus on the role of the Drosophila twins (tws) gene in the maintenance of chromosome integrity; tws encodes the B regulatory subunit (B/B55) of PP2A. Mutations in tws cause high frequencies of CABs (0.5 CABs/cell) in Drosophila larval brain cells and lead to an abnormal persistence of γ-H2Av repair foci. However, mutations that disrupt the PP4 phosphatase activity impair foci dissolution but do not cause CABs, suggesting that a delayed foci regression is not clastogenic. We also show that Tws is required for activation of the G2/M DNA damage checkpoint while PP4 is required for checkpoint recovery, a result that points to a conserved function of these phosphatases from flies to humans. Mutations in the ATM-coding gene tefu are strictly epistatic to tws mutations for the CAB phenotype, suggesting that failure to dephosphorylate an ATM substrate(s) impairs DNA DSBs repair. In addition, mutations in the Ku70 gene, which do not cause CABs, completely suppress CAB formation in tws Ku70 double mutants. These results suggest the hypothesis that an improperly phosphorylated Ku70 protein can lead to DNA damage and CABs.
Collapse
|
13
|
Drosophila IRBP bZIP heterodimer binds P-element DNA and affects hybrid dysgenesis. Proc Natl Acad Sci U S A 2016; 113:13003-13008. [PMID: 27799520 DOI: 10.1073/pnas.1613508113] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
In Drosophila, P-element transposition causes mutagenesis and genome instability during hybrid dysgenesis. The P-element 31-bp terminal inverted repeats (TIRs) contain sequences essential for transposase cleavage and have been implicated in DNA repair via protein-DNA interactions with cellular proteins. The identity and function of these cellular proteins were unknown. Biochemical characterization of proteins that bind the TIRs identified a heterodimeric basic leucine zipper (bZIP) complex between an uncharacterized protein that we termed "Inverted Repeat Binding Protein (IRBP) 18" and its partner Xrp1. The reconstituted IRBP18/Xrp1 heterodimer binds sequence-specifically to its dsDNA-binding site within the P-element TIRs. Genetic analyses implicate both proteins as critical for repair of DNA breaks following transposase cleavage in vivo. These results identify a cellular protein complex that binds an active mobile element and plays a more general role in maintaining genome stability.
Collapse
|
14
|
Cenci G, Ciapponi L, Marzullo M, Raffa GD, Morciano P, Raimondo D, Burla R, Saggio I, Gatti M. The Analysis of Pendolino (peo) Mutants Reveals Differences in the Fusigenic Potential among Drosophila Telomeres. PLoS Genet 2015; 11:e1005260. [PMID: 26110638 PMCID: PMC4481407 DOI: 10.1371/journal.pgen.1005260] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 05/04/2015] [Indexed: 01/08/2023] Open
Abstract
Drosophila telomeres are sequence-independent structures that are maintained by transposition to chromosome ends of three specialized retroelements (HeT-A, TART and TAHRE; collectively designated as HTT) rather than telomerase activity. Fly telomeres are protected by the terminin complex (HOAP-HipHop-Moi-Ver) that localizes and functions exclusively at telomeres and by non-terminin proteins that do not serve telomere-specific functions. Although all Drosophila telomeres terminate with HTT arrays and are capped by terminin, they differ in the type of subtelomeric chromatin; the Y, XR, and 4L HTT are juxtaposed to constitutive heterochromatin, while the XL, 2L, 2R, 3L and 3R HTT are linked to the TAS repetitive sequences; the 4R HTT is associated with a chromatin that has features common to both euchromatin and heterochromatin. Here we show that mutations in pendolino (peo) cause telomeric fusions (TFs). The analysis of several peo mutant combinations showed that these TFs preferentially involve the Y, XR and 4th chromosome telomeres, a TF pattern never observed in the other 10 telomere-capping mutants so far characterized. peo encodes a non-terminin protein homologous to the E2 variant ubiquitin-conjugating enzymes. The Peo protein directly interacts with the terminin components, but peo mutations do not affect telomeric localization of HOAP, Moi, Ver and HP1a, suggesting that the peo-dependent telomere fusion phenotype is not due to loss of terminin from chromosome ends. peo mutants are also defective in DNA replication and PCNA recruitment. However, our results suggest that general defects in DNA replication are unable to induce TFs in Drosophila cells. We thus hypothesize that DNA replication in Peo-depleted cells results in specific fusigenic lesions concentrated in heterochromatin-associated telomeres. Alternatively, it is possible that Peo plays a dual function being independently required for DNA replication and telomere capping. Telomeres are specialized structures that protect chromosome ends from incomplete replication, degradation and end-to-end fusion. Abnormalities in telomere structure or maintenance can promote a variety of human diseases including premature aging and cancer. Although all human telomeres contain the same DNA sequences, they differ from each other in the subtelomeric regions or subtelomeres. Recent work has shown that human subtelomeres control telomere replication and that abnormalities in these structures can lead to localized chromosome instability and disease. However, the relationships between subtelomeres and telomeres are currently poorly understood. Here, we have addressed this problem using the fruit fly Drosophila melanogaster as model system. Drosophila subtelomers are very different from each other as they contain different types of chromatin. We have found that mutations in a gene we called pendolino (peo) cause telomeric fusions (TFs) and that these fusions preferentially involve the telomeres associated with a tightly packed form of chromatin called heterochromatin. Interestingly, none of the 10 mutants with TFs so far described in Drosophila shows the pattern of TFs observed in peo mutants. Thus, our data provide the first demonstration that subtelomeres can affect telomere fusion. We believe that these results will stimulate further studies on the role of subtelomeres in the maintenance of genome stability.
Collapse
Affiliation(s)
- Giovanni Cenci
- Dipartimento di Biologia e Biotecnologie, Sapienza—Università di Roma, Roma, Italy
- Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza—Università di Roma, Roma, Italy
| | - Laura Ciapponi
- Dipartimento di Biologia e Biotecnologie, Sapienza—Università di Roma, Roma, Italy
- Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza—Università di Roma, Roma, Italy
| | - Marta Marzullo
- Dipartimento di Biologia e Biotecnologie, Sapienza—Università di Roma, Roma, Italy
- Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza—Università di Roma, Roma, Italy
| | - Grazia D. Raffa
- Dipartimento di Biologia e Biotecnologie, Sapienza—Università di Roma, Roma, Italy
- Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza—Università di Roma, Roma, Italy
| | - Patrizia Morciano
- Dipartimento di Biologia e Biotecnologie, Sapienza—Università di Roma, Roma, Italy
- Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza—Università di Roma, Roma, Italy
| | | | - Romina Burla
- Dipartimento di Biologia e Biotecnologie, Sapienza—Università di Roma, Roma, Italy
- Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza—Università di Roma, Roma, Italy
| | - Isabella Saggio
- Dipartimento di Biologia e Biotecnologie, Sapienza—Università di Roma, Roma, Italy
- Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza—Università di Roma, Roma, Italy
- IBPM CNR, Sapienza—Università di Roma, Roma, Italy
| | - Maurizio Gatti
- Dipartimento di Biologia e Biotecnologie, Sapienza—Università di Roma, Roma, Italy
- Istituto Pasteur Fondazione Cenci Bolognetti, Sapienza—Università di Roma, Roma, Italy
- IBPM CNR, Sapienza—Università di Roma, Roma, Italy
- * E-mail:
| |
Collapse
|
15
|
Majumdar S, Rio DC. P Transposable Elements in Drosophila and other Eukaryotic Organisms. Microbiol Spectr 2015; 3:MDNA3-0004-2014. [PMID: 26104714 PMCID: PMC4399808 DOI: 10.1128/microbiolspec.mdna3-0004-2014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Indexed: 11/20/2022] Open
Abstract
P transposable elements were discovered in Drosophila as the causative agents of a syndrome of genetic traits called hybrid dysgenesis. Hybrid dysgenesis exhibits a unique pattern of maternal inheritance linked to the germline-specific small RNA piwi-interacting (piRNA) pathway. The use of P transposable elements as vectors for gene transfer and as genetic tools revolutionized the field of Drosophila molecular genetics. P element transposons have served as a useful model to investigate mechanisms of cut-and-paste transposition in eukaryotes. Biochemical studies have revealed new and unexpected insights into how eukaryotic DNA-based transposons are mobilized. For example, the P element transposase makes unusual 17nt-3' extended double-strand DNA breaks at the transposon termini and uses guanosine triphosphate (GTP) as a cofactor to promote synapsis of the two transposon ends early in the transposition pathway. The N-terminal DNA binding domain of the P element transposase, called a THAP domain, contains a C2CH zinc-coordinating motif and is the founding member of a large family of animal-specific site-specific DNA binding proteins. Over the past decade genome sequencing efforts have revealed the presence of P element-like transposable elements or P element transposase-like genes (called THAP9) in many eukaryotic genomes, including vertebrates, such as primates including humans, zebrafish and Xenopus, as well as the human parasite Trichomonas vaginalis, the sea squirt Ciona, sea urchin and hydra. Surprisingly, the human and zebrafish P element transposase-related THAP9 genes promote transposition of the Drosophila P element transposon DNA in human and Drosophila cells, indicating that the THAP9 genes encode active P element "transposase" proteins.
Collapse
Affiliation(s)
| | - Donald C. Rio
- Department of Molecular and Cell Biology University of California, Berkeley Berkeley, CA 94720-3204
| |
Collapse
|
16
|
Drosophila RecQ5 is involved in proper progression of early spermatogenesis. Biochem Biophys Res Commun 2014; 452:1071-7. [PMID: 25245292 DOI: 10.1016/j.bbrc.2014.09.051] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 09/12/2014] [Indexed: 11/22/2022]
Abstract
RecQ5, a member of the conserved RecQ DNA helicase family, is required for the maintenance of genome stability. The human RECQL5 gene is expressed ubiquitously in almost all tissues, with strong expression in the testes (Shimamoto et al., 2000). However, it remains to be elucidated in which cells RecQ5 is expressed and how RecQ5 functions in the testes. In this present study we analyzed the expression of RecQ5 in Drosophila testes. The RecQ5 protein was specifically expressed in germline cells in larval, pupal, and adult testes. Drosophila RecQ5 was localized in nuclei of male germline stem cells, spermatogoniablasts, spermatogonia, and early spermatocytes. As growth of the early spermatocyte proceeded, the amount of RecQ5 increased in the nuclei. However, before maturation of the spermatocyte, the level of RecQ5 declined. Thus, RecQ5 expression was regulated. Furthermore, we compared recq5 mutant testes with the wild-type ones. The most conspicuous alterations were swelling of the apical region of and an increase in the number of spermatocytes in the recq5 testis, suggesting a relative accumulation of spermatocytes in the recq5 mutant testes. Therefore, Drosophila RecQ5 may contribute to the proper progression from germline stem cells to spermatocytes for maintenance of genome stability.
Collapse
|
17
|
Drosophila FANCM helicase prevents spontaneous mitotic crossovers generated by the MUS81 and SLX1 nucleases. Genetics 2014; 198:935-45. [PMID: 25205745 DOI: 10.1534/genetics.114.168096] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Several helicases function during repair of double-strand breaks and handling of blocked or stalled replication forks to promote pathways that prevent formation of crossovers. Among these are the Bloom syndrome helicase BLM and the Fanconi anemia group M (FANCM) helicase. To better understand functions of these helicases, we compared phenotypes of Drosophila melanogaster Blm and Fancm mutants. As previously reported for BLM, FANCM has roles in responding to several types of DNA damage in preventing mitotic and meiotic crossovers and in promoting the synthesis-dependent strand annealing pathway for repair of a double-strand gap. In most assays, the phenotype of Fancm mutants is less severe than that of Blm mutants, and the phenotype of Blm Fancm double mutants is more severe than either single mutant, indicating both overlapping and unique functions. It is thought that mitotic crossovers arise when structure-selective nucleases cleave DNA intermediates that would normally be unwound or disassembled by these helicases. When BLM is absent, three nucleases believed to function as Holliday junction resolvases--MUS81-MMS4, MUS312-SLX1, and GEN--become essential. In contrast, no single resolvase is essential in mutants lacking FANCM, although simultaneous loss of GEN and either of the others is lethal in Fancm mutants. Since Fancm mutants can tolerate loss of a single resolvase, we were able to show that spontaneous mitotic crossovers that occur when FANCM is missing are dependent on MUS312 and either MUS81 or SLX1.
Collapse
|
18
|
Milán M, Clemente-Ruiz M, Dekanty A, Muzzopappa M. Aneuploidy and tumorigenesis in Drosophila. Semin Cell Dev Biol 2014; 28:110-5. [DOI: 10.1016/j.semcdb.2014.03.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 03/03/2014] [Accepted: 03/10/2014] [Indexed: 12/15/2022]
|
19
|
Dekanty A, Barrio L, Milán M. Contributions of DNA repair, cell cycle checkpoints and cell death to suppressing the DNA damage-induced tumorigenic behavior of Drosophila epithelial cells. Oncogene 2014; 34:978-85. [DOI: 10.1038/onc.2014.42] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 02/04/2014] [Accepted: 02/07/2014] [Indexed: 12/21/2022]
|
20
|
Li JJ, Gu QH, Li M, Yang HP, Cao LM, Hu CP. Role of Ku70 and Bax in epigallocatechin-3-gallate-induced apoptosis of A549 cells in vivo. Oncol Lett 2012; 5:101-106. [PMID: 23255902 DOI: 10.3892/ol.2012.972] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 08/15/2012] [Indexed: 11/06/2022] Open
Abstract
EGCG (epigallocatechin-3-gallate), the major catechin found in green tea, has been demonstrated to inhibit proliferation and induce apoptosis in a number of types of tumors. Recent studies reveal that EGCG has various anticancer effects. This study investigated a further possible molecular mechanism of the anticancer effects of EGCG in murine lung cancer xenografts. In the study, A549 human lung cancer cells were injected into nude mice. Tumor volume was used to measure cancer cell growth. The weight of the animals was used to assess the toxicity of the drugs. The expression of protein and mRNA was assayed by western blot analysis and RT-PCR, respectively. The interaction between Bax and Ku70 was determined by immunoprecipitation. Our results suggest that EGCG induced A549 lung cancer cell apoptosis in vivo, and had less toxic effects compared to classical anticancer drugs. EGCG may inhibit the surrogate markers of proliferation and apoptosis (caspase 3) in A549 tumor xenografts in vivo. In addition, EGCG downregulated the expression of Bcl-xl and upregulated the expression of Bax mRNA and protein. Further experiments indicated that EGCG downregulated the protein expression of Ku70 and interrupted the binding of Ku70 and Bax. This is the first study demonstrating that the induction of apoptosis by EGCG may be caused by the downregulation of Ku70 and that EGCG disrupts the interaction between Ku70 and Bax in lung cancer.
Collapse
Affiliation(s)
- Jing-Jing Li
- Department of Respiratory Medicine, Xiangya Hospital, Central South University, Changsha, Hunan 410008, P.R. China
| | | | | | | | | | | |
Collapse
|
21
|
Drosophila Mgr, a Prefoldin subunit cooperating with von Hippel Lindau to regulate tubulin stability. Proc Natl Acad Sci U S A 2012; 109:5729-34. [PMID: 22451918 DOI: 10.1073/pnas.1108537109] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Mutations in Drosophila merry-go-round (mgr) have been known for over two decades to lead to circular mitotic figures and loss of meiotic spindle integrity. However, the identity of its gene product has remained undiscovered. We now show that mgr encodes the Prefoldin subunit counterpart of human von Hippel Lindau binding-protein 1. Depletion of Mgr from cultured cells also leads to formation of monopolar and abnormal spindles and centrosome loss. These phenotypes are associated with reductions of tubulin levels in both mgr flies and mgr RNAi-treated cultured cells. Moreover, mgr spindle defects can be phenocopied by depleting β-tubulin, suggesting Mgr function is required for tubulin stability. Instability of β-tubulin in the mgr larval brain is less pronounced than in either mgr testes or in cultured cells. However, expression of transgenic β-tubulin in the larval brain leads to increased tubulin instability, indicating that Prefoldin might only be required when tubulins are synthesized at high levels. Mgr interacts with Drosophila von Hippel Lindau protein (Vhl). Both proteins interact with unpolymerized tubulins, suggesting they cooperate in regulating tubulin functions. Accordingly, codepletion of Vhl with Mgr gives partial rescue of tubulin instability, monopolar spindle formation, and loss of centrosomes, leading us to propose a requirement for Vhl to promote degradation of incorrectly folded tubulin in the absence of functional Prefoldin. Thus, Vhl may play a pivotal role: promoting microtubule stabilization when tubulins are correctly folded by Prefoldin and tubulin destruction when they are not.
Collapse
|
22
|
Loss of the bloom syndrome helicase increases DNA ligase 4-independent genome rearrangements and tumorigenesis in aging Drosophila. Genome Biol 2011; 12:R121. [PMID: 22183041 PMCID: PMC3334616 DOI: 10.1186/gb-2011-12-12-r121] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 11/25/2011] [Accepted: 12/19/2011] [Indexed: 12/12/2022] Open
Abstract
Background The BLM DNA helicase plays a vital role in maintaining genome stability. Mutations in BLM cause Bloom syndrome, a rare disorder associated with cancer predisposition and premature aging. Humans and mice with blm mutations have increased frequencies of spontaneous mutagenesis, but the molecular basis of this increase is not well understood. In addition, the effect of aging on spontaneous mutagenesis in blm mutants has not been characterized. To address this, we used a lacZ reporter system in wild-type and several mutant strains of Drosophila melanogaster to analyze mechanisms of mutagenesis throughout their lifespan. Results Our data show that Drosophila lacking BLM have an elevated frequency of spontaneous genome rearrangements that increases with age. Although in normal flies most genome rearrangements occur through DNA ligase 4-dependent classical end joining, most rearrangements that accumulate during aging in blm mutants do not require DNA ligase 4, suggesting the influence of an alternative end-joining mechanism. Adult blm mutants also display reduced lifespan and ligase 4-independent enhanced tumorigenesis in mitotically active tissues. Conclusions These results suggest that Drosophila BLM suppresses error-prone alternative end-joining repair of DNA double-strand breaks that can result in genome instability and tumor formation during aging. In addition, since loss of BLM significantly affects lifespan and tumorigenesis, the data provide a link between error-prone end joining, genome rearrangements, and tumor formation in a model metazoan.
Collapse
|
23
|
RecQ helicases; at the crossroad of genome replication, repair, and recombination. Mol Biol Rep 2011; 39:4527-43. [PMID: 21947842 DOI: 10.1007/s11033-011-1243-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 09/14/2011] [Indexed: 01/07/2023]
Abstract
DNA helicases are ubiquitous enzymes that unwind double-stranded DNA in an ATP-dependent and directionally specific manner. Such an action is essential for the processes of DNA repair, recombination, transcription, and DNA replication. Here, I focus on a subgroup of DNA helicases, the RecQ family, which is highly conserved in evolution. Members of this conserved family of proteins have a key role in protecting and stabilizing the genome against deleterious changes. Deficiencies in RecQ helicases can lead to high levels of genomic instability and, in humans, to premature aging and increased susceptibility to cancer. Their diverse roles in DNA metabolism, which include a role in telomere maintenance, reflect interactions with multiple cellular proteins, some of which are multifunctional and also have very diverse functions. In this review, protein structural motifs and the roles of different domains will be discussed first. The Review moves on to speculate about the different models to explain why RecQ helicases are required to protect against genome instability.
Collapse
|
24
|
Mishra M, Sharma A, Negi MPS, Dwivedi UN, Chowdhuri DK. Tracing the tracks of genotoxicity by trivalent and hexavalent chromium in Drosophila melanogaster. Mutat Res 2011; 722:44-51. [PMID: 21382505 DOI: 10.1016/j.mrgentox.2011.02.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Revised: 02/14/2011] [Accepted: 02/27/2011] [Indexed: 01/08/2023]
Abstract
Mutagen sensitive strains (mus) in Drosophila are known for their hypersensitivity to mutagens and environmental carcinogens. Accordingly, these mutants were grouped in pre- and post-replication repair pathways. However, studying mutants belonging to one particular repair pathway may not be adequate for examining chemical-induced genotoxicity when other repair pathways may neutralize its effect. To test whether both pre-and post-replication pathways are involved and effect of Cr(III)- and Cr(VI)-induced genotoxicity in absence or presence of others, we used double mutant approach in D. melanogaster. We observed DNA damage as evident by changes in Comet assay DNA migration in cells of larvae of Oregon R(+) and single mutants of pre- (mei-9, mus201 and mus210) and post- (mei-41, mus209 and mus309) replication repair pathways and also in double mutants of different combinations (pre-pre, pre-post and post-post replication repair) exposed to increasing concentrations of Cr(VI) (0.0, 5.0, 10.0 and 20.0 μg/ml) for 48 h. The damage was greater in pre-replication repair mutants after exposure to 5.0 μg/ml Cr(VI), while effects on Oregon R(+) and post replication repair mutants were insignificant. Post-replication repair mutants revealed significant DNA damage after exposure to 20.0 μg/ml Cr(VI). Further, double mutants generated in the above repair categories were examined for DNA damage following Cr(VI) exposure and a comparison of damage was studied between single and double mutants. Combinations of double mutants generated in the pre-pre replication repair pathways showed an indifferent interaction between the two mutants after Cr(VI) exposure while a synergistic interaction was evident in exposed post-post replication repair double mutants. Cr(III) (20.0 μg/ml) exposure to these strains did not induce any significant DNA damage in their cells. The study suggests that both pre- and post-replication pathways are affected in Drosophila by Cr(VI) leading to genotoxicity, which may have consequences for metal-induced carcinogenesis.
Collapse
Affiliation(s)
- Manish Mishra
- Embryotoxicology Section, Indian Institute of Toxicology Research, Lucknow 226 001, India
| | | | | | | | | |
Collapse
|
25
|
Abstract
The RecQ helicases are conserved from bacteria to humans and play a critical role in genome stability. In humans, loss of RecQ gene function is associated with cancer predisposition and/or premature aging. Recent experiments have shown that the RecQ helicases function during distinct steps during DNA repair; DNA end resection, displacement-loop (D-loop) processing, branch migration, and resolution of double Holliday junctions (dHJs). RecQ function in these different processing steps has important implications for its role in repair of double-strand breaks (DSBs) that occur during DNA replication and meiosis, as well as at specific genomic loci such as telomeres.
Collapse
Affiliation(s)
- Kara A Bernstein
- Columbia University Medical Center, Department of Genetics & Development, New York, New York 10032, USA.
| | | | | |
Collapse
|
26
|
Lem AJ, Boonstra VH, Renes JS, Breukhoven PE, de Jong FH, Laven JSE, Hokken-Koelega ACS. Anti-Mullerian hormone in short girls born small for gestational age and the effect of growth hormone treatment. Hum Reprod 2011; 26:898-903. [DOI: 10.1093/humrep/deq391] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
27
|
Evidence based on studies of the mus309 mutant, deficient in DNA double-strand break repair, that meiotic crossing over in Drosophila melanogaster is a two-phase process. Genetica 2010; 138:1033-45. [PMID: 20803348 DOI: 10.1007/s10709-010-9489-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 08/19/2010] [Indexed: 10/19/2022]
Abstract
The mus309 gene in Drosophila melanogaster encodes a RecQ helicase which is involved in DNA double-strand break (DSB) repair and specifically in the choice between the different pathways of the repair. In a brood pattern analysis of mus309 and wild type females which either had or had not experienced a temperature shock, different parameters of meiotic crossing over including map distances and crossover interference in the X chromosome were measured. The results suggest that, like in other eukaryotes studied, the control of meiotic crossover formation also in D. melanogaster is a two-phase process. The first phase seems to be temperature shock sensitive, independent of the mus309 gene and coincidental with the premeiotic DNA synthesis, thus most likely representing the formation of DSBs. The second phase seems to be temperature shock tolerant, dependent on the mus309 gene, occurring during the meiotic prophase and most likely representing the choice made by the oocyte between the different pathways of the DSB repair. A hypothesis of the localization of chiasmata is also presented, combining the mechanisms of interference and the so-called centromere effect, and based on the balance between the SDSA and DSBR pathways of DSB repair.
Collapse
|
28
|
Portin P. Retraction: Effect of temperature shock treatment on crossing over in themus309mutant, deficient in DNA double-strand break repair, ofDrosophila melanogastersuggests a two-phase control of crossover formation and interference. Hereditas 2010. [DOI: 10.1111/j.1601-5223.2010.02180.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
29
|
Chan SH, Yu AM, McVey M. Dual roles for DNA polymerase theta in alternative end-joining repair of double-strand breaks in Drosophila. PLoS Genet 2010; 6:e1001005. [PMID: 20617203 PMCID: PMC2895639 DOI: 10.1371/journal.pgen.1001005] [Citation(s) in RCA: 178] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Accepted: 05/27/2010] [Indexed: 11/25/2022] Open
Abstract
DNA double-strand breaks are repaired by multiple mechanisms that are roughly grouped into the categories of homology-directed repair and non-homologous end joining. End-joining repair can be further classified as either classical non-homologous end joining, which requires DNA ligase 4, or “alternative” end joining, which does not. Alternative end joining has been associated with genomic deletions and translocations, but its molecular mechanism(s) are largely uncharacterized. Here, we report that Drosophila melanogaster DNA polymerase theta (pol theta), encoded by the mus308 gene and previously implicated in DNA interstrand crosslink repair, plays a crucial role in DNA ligase 4-independent alternative end joining. In the absence of pol theta, end joining is impaired and residual repair often creates large deletions flanking the break site. Analysis of break repair junctions from flies with mus308 separation-of-function alleles suggests that pol theta promotes the use of long microhomologies during alternative end joining and increases the likelihood of complex insertion events. Our results establish pol theta as a key protein in alternative end joining in Drosophila and suggest a potential mechanistic link between alternative end joining and interstrand crosslink repair. DNA double-strand breaks, in which both strands of the DNA double helix are cut, must be recognized and accurately repaired in order to promote cell survival and prevent the accumulation of mutations. However, error-prone repair occasionally occurs, even when accurate repair is possible. We have investigated the genetic requirements of an error-prone break-repair mechanism called alternative end joining. We have previously shown that alternative end joining is frequently used in the fruit fly, Drosophila melanogaster. Here, we demonstrate that a fruit fly protein named DNA polymerase theta is a key player in this inaccurate repair mechanism. Genetic analysis suggests that polymerase theta may be important for two processes associated with alternative end joining: (1) annealing at short, complementary DNA sequences, and (2) DNA synthesis that creates small insertions at break-repair sites. In the absence of polymerase theta, a backup repair mechanism that frequently results in large chromosome deletions is revealed. Because DNA polymerase theta is highly expressed in many types of human cancers, our findings lay the groundwork for further investigations into how polymerase theta is involved in repair processes that may promote the development of cancer.
Collapse
Affiliation(s)
- Sze Ham Chan
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Amy Marie Yu
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Mitch McVey
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
- Program in Genetics, Tufts Sackler School of Graduate Biomedical Sciences, Boston, Massachusetts, United States of America
- * E-mail:
| |
Collapse
|
30
|
Drosophila RecQ5 is required for efficient SSA repair and suppression of LOH in vivo. Protein Cell 2010; 1:478-90. [PMID: 21203963 DOI: 10.1007/s13238-010-0058-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Accepted: 04/25/2010] [Indexed: 10/19/2022] Open
Abstract
RecQ5 in mammalian cells has been suggested to suppress inappropriate homologous recombination. However, the specific pathway(s) in which it is involved and the underlining mechanism(s) remain poorly understood. We took advantage of genetic tools in Drosophila to investigate how Drosophila RecQ5 (dRecQ5) functions in vivo in homologous recombination-mediated double strand break (DSB) repair. We generated null alleles of dRecQ5 using the targeted recombination technique. The mutant animals are homozygous viable, but with growth retardation during development. The mutants are sensitive to both exogenous DSB-inducing treatment, such as gamma-irradiation, and endogenously induced double strand breaks (DSBs) by I-Sce I endonuclease. In the absence of dRecQ5, single strand annealing (SSA)-mediated DSB repair is compromised with compensatory increases in either inter-homologous gene conversion, or non-homologous end joining (NHEJ) when inter-chromosomal homologous sequence is unavailable. Loss of function of dRecQ5 also leads to genome instability in loss of heterozygosity (LOH) assays. Together, our data demonstrate that dRecQ5 functions in SSA-mediated DSB repair to achieve its full efficiency and in suppression of LOH in Drosophila.
Collapse
|
31
|
Portin P. The effect of the mus309 mutation, defective in DNA double-strand break repair, on crossing over in Drosophila melanogaster suggests a mechanism for the centromere effect of crossing over. Genetica 2009; 138:333-42. [PMID: 19882364 DOI: 10.1007/s10709-009-9422-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 10/20/2009] [Indexed: 11/25/2022]
Abstract
The mus309 gene in Drosophila melanogaster encodes a RecQ helicase which is involved in DNA double-strand break (DSB) repair. In a brood pattern analysis, it was observed that in mus309 mutant females, the frequency of single crossovers in the central cv-v interval of the X chromosome was reduced in young females but returned to the level of the wild type control as the females aged. In the proximal v-f interval, the frequency of single crossovers was increased during the entire experimental period. In particular, it was observed that the frequency of double crossovers, as well as the coefficient of coincidence first increased but then gradually decreased, finally reaching the level of the control flies, as the females aged. Map distances increased due to the mus309 mutation in both gene interval studies, but they did not change as the females aged, a result suggesting that the mus309 gene controls the distribution of DSBs to be repaired as crossovers instead of non-crossovers. The results suggest a mechanism for the centromere effect of crossing over in Drosophila, viz the fact the frequency of meiotic crossing over reduces with the age of the female, and that the reduction is more pronounced the closer the interval is to the proximal heterochromatin of the chromosome arm. According to the model suggested, the centromere effect is simply a matter of the balance between different pathways of the repair of the DSBs of DNA.
Collapse
Affiliation(s)
- Petter Portin
- Department of Biology, University of Turku, Turku, Finland.
| |
Collapse
|
32
|
Robertson HM. The choanoflagellate Monosiga brevicollis karyotype revealed by the genome sequence: telomere-linked helicase genes resemble those of some fungi. Chromosome Res 2009; 17:873-82. [PMID: 19789987 DOI: 10.1007/s10577-009-9078-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 08/06/2009] [Accepted: 08/13/2009] [Indexed: 12/01/2022]
Abstract
The approximately 42 Mbp assembled genome sequence for the choanoflagellate Monosiga brevicollis reveals that most of the large scaffolds of 300-2,600 kb represent entire chromosomes or chromosome arms. Telomeres are partially assembled at the termini of 37 scaffolds, while another 43 scaffolds end in telomere-associated regions containing distinctive gene sets. Potential centromeric regions were identified on 39 scaffolds. Together, these observations suggest a karyotype of approximately 40 metacentric and submetacentric chromosomes averaging 1 Mbp in size. Genes encoding RecQ family DNA helicases, along with ankyrin-domain proteins and serine/threonine kinases, are associated with most telomeres, a feature shared with some fungi. This telomere-linked helicase gene arrangement might be ancestral to both fungi and choanoflagellates in the super-kingdom Opisthokonta; however, the great lability of telomere architecture suggests that it could also be a convergent feature.
Collapse
Affiliation(s)
- Hugh M Robertson
- Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
| |
Collapse
|
33
|
Portin P. The effect of the mus309 mutation, defective in DNA double-strand break repair, on crossing over in Drosophila melanogaster suggests a mechanism for interference. Hereditas 2009; 146:162-76. [PMID: 19765096 DOI: 10.1111/j.1601-5223.2009.02144.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The mus309 gene in Drosophila melanogaster encodes a RecQ helicase which is involved in DNA double-strand break (DSB) repair. In a brood pattern analysis, it was observed that in mus309 mutant females, the frequency of single crossovers in the central cv - v interval of the X chromosome was decreased in young females but returned to the level of the wild type control as the females aged. In the proximal v - f interval, the frequency of single crossovers was increased during the whole experimental period. In particular, it was observed that the frequency of double crossovers, as well as the coefficient of coincidence first increased but then gradually decreased, finally reaching the level of the control flies, as the females aged. Map distances increased due to the mus309 mutation in both gene interval studies, but they did not change as the females aged, a result suggesting that the mus309 gene controls the distribution of DSBs to be repaired as crossovers instead of non-crossovers. The results are consistent with the hypothesis that in general the DSBs are initially independently distributed on the chromosome but non-randomly repaired so that the distribution of crossovers in the mutant flies becomes uniform, but uneven in wild-type flies. The results are consistent with the counting number model of crossover interference, based on genetic distance. On the other hand, the data are not consistent with the reaction-diffusion model based on physical distance. Consequently, the view that crossover interference in Drosophila is tightly tied to genetic distance is supported.
Collapse
Affiliation(s)
- Petter Portin
- Laboratory of Genetics, Department of Biology, University of Turku, Turku, Finland.
| |
Collapse
|
34
|
Removal of the bloom syndrome DNA helicase extends the utility of imprecise transposon excision for making null mutations in Drosophila. Genetics 2009; 183:1187-93. [PMID: 19687136 DOI: 10.1534/genetics.109.108472] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transposable elements are frequently used in Drosophila melanogaster for imprecise excision screens to delete genes of interest. However, these screens are highly variable in the number and size of deletions that are recovered. Here, we show that conducting excision screens in mus309 mutant flies that lack DmBlm, the Drosophila ortholog of the Bloom syndrome protein, increases the percentage and overall size of flanking deletions recovered after excision of either P or Minos elements.
Collapse
|
35
|
Miyoshi T, Kanoh J, Ishikawa F. Fission yeast Ku protein is required for recovery from DNA replication stress. Genes Cells 2009; 14:1091-103. [PMID: 19682091 DOI: 10.1111/j.1365-2443.2009.01337.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The fundamental function of the conserved Ku70-Ku80 heterodimer is to promote the non-homologous end-joining (NHEJ) pathway in double-strand break repair. Although it is thought that Ku plays several roles other than NHEJ in maintaining chromosomal integrity including telomere protection, these precise functions remain unclear. In this study, we describe a novel role of fission yeast Ku proteins encoded by pku70(+) and pku80(+) genes in dealing with DNA replication stress. In the absence of Rqh1, the fission yeast RecQ helicase, the cells are sensitive to reagents inducing replication stress. pkuDeltarqh1Delta double mutant showed synergistic sensitivities to these reagents. However, this synthetic phenotype was not observed when rqh1Delta mutant was coupled with the deletion of lig4(+) that encodes a ligase essential for NHEJ, indicating that the role of Ku in replication stress is NHEJ independent. pkuDeltarqh1Delta double mutant also showed highly variable copy numbers of rDNA repeats even under unstressed condition. Furthermore, the double mutant exhibited inefficient replication resumption after transient replication stalling. These results suggest the possibility that Ku proteins play an important role in genome integrity recovering replication stress.
Collapse
Affiliation(s)
- Tomoichiro Miyoshi
- Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Yoshida-konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | | | | |
Collapse
|
36
|
Xu Y, Lei Z, Huang H, Dui W, Liang X, Ma J, Jiao R. dRecQ4 is required for DNA synthesis and essential for cell proliferation in Drosophila. PLoS One 2009; 4:e6107. [PMID: 19572017 PMCID: PMC2700968 DOI: 10.1371/journal.pone.0006107] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Accepted: 06/02/2009] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The family of RecQ DNA helicases plays an important role in the maintenance of genomic integrity. Mutations in three of the five known RecQ family members in humans, BLM, WRN and RecQ4, lead to disorders that are characterized by predisposition to cancer and premature aging. METHODOLOGY/PRINCIPAL FINDINGS To address the in vivo functions of Drosophila RecQ4 (dRecQ4), we generated mutant alleles of dRecQ4 using the targeted gene knock-out technique. Our data show that dRecQ4 mutants are homozygous lethal with defects in DNA replication, cell cycle progression and cell proliferation. Two sets of experiments suggest that dRecQ4 also plays a role in DNA double strand break repair. First, mutant animals exhibit sensitivity to gamma irradiation. Second, the efficiency of DsRed reconstitution via single strand annealing repair is significantly reduced in the dRecQ4 mutant animals. Rescue experiments further show that both the N-terminal domain and the helicase domain are essential to dRecQ4 function in vivo. The N-terminal domain is sufficient for the DNA repair function of dRecQ4. CONCLUSIONS/SIGNIFICANCE Together, our results show that dRecQ4 is an essential gene that plays an important role in not only DNA replication but also DNA repair and cell cycle progression in vivo.
Collapse
Affiliation(s)
- Yanjuan Xu
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, the Chinese Academy of Sciences, Beijing, China
- Graduate School of the Chinese Academy of Sciences, Beijing, China
| | - Zhiyong Lei
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, the Chinese Academy of Sciences, Beijing, China
| | - Hai Huang
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, the Chinese Academy of Sciences, Beijing, China
- Graduate School of the Chinese Academy of Sciences, Beijing, China
| | - Wen Dui
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, the Chinese Academy of Sciences, Beijing, China
- Graduate School of the Chinese Academy of Sciences, Beijing, China
| | - Xuehong Liang
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, the Chinese Academy of Sciences, Beijing, China
| | - Jun Ma
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, the Chinese Academy of Sciences, Beijing, China
- Divisions of Biomedical Informatics and Developmental Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio, United States of America
| | - Renjie Jiao
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, the Chinese Academy of Sciences, Beijing, China
- * E-mail:
| |
Collapse
|
37
|
Kappeler M, Kranz E, Woolcock K, Georgiev O, Schaffner W. Drosophila bloom helicase maintains genome integrity by inhibiting recombination between divergent DNA sequences. Nucleic Acids Res 2008; 36:6907-17. [PMID: 18978019 PMCID: PMC2588521 DOI: 10.1093/nar/gkn793] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
DNA double strand breaks (DSB) can be repaired either via a sequence independent joining of DNA ends or via homologous recombination. We established a detection system in Drosophila melanogaster to investigate the impact of sequence constraints on the usage of the homology based DSB repair via single strand annealing (SSA), which leads to recombination between direct repeats with concomitant loss of one repeat copy. First of all, we find the SSA frequency to be inversely proportional to the spacer length between the repeats, for spacers up to 2.4 kb in length. We further show that SSA between divergent repeats (homeologous SSA) is suppressed in cell cultures and in vivo in a sensitive manner, recognizing sequence divergences smaller than 0.5%. Finally, we demonstrate that the suppression of homeologous SSA depends on the Bloom helicase (Blm), encoded by the Drosophila gene mus309. Suppression of homeologous recombination is a novel function of Blm in ensuring genomic integrity, not described to date in mammalian systems. Unexpectedly, distinct from its function in Saccharomyces cerevisiae, the mismatch repair factor Msh2 encoded by spel1 does not suppress homeologous SSA in Drosophila.
Collapse
Affiliation(s)
- Michael Kappeler
- Insitut für Molekularbiologie der Universität Zürich, Zürich, Switzerland
| | | | | | | | | |
Collapse
|
38
|
Wu J, Capp C, Feng L, Hsieh TS. Drosophila homologue of the Rothmund-Thomson syndrome gene: essential function in DNA replication during development. Dev Biol 2008; 323:130-42. [PMID: 18755177 DOI: 10.1016/j.ydbio.2008.08.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2008] [Revised: 08/05/2008] [Accepted: 08/06/2008] [Indexed: 11/16/2022]
Abstract
Members of the RecQ family play critical roles in maintaining genome integrity. Mutations in human RecQL4 cause a rare genetic disorder, Rothmund-Thomson syndrome. Transgenic mice experiments showed that the RecQ4 null mutant causes embryonic lethality. Although biochemical evidence suggests that the Xenopus RecQ4 is required for the initiation of DNA replication in the oocyte extract, its biological functions during development remain to be elucidated. We present here our results in establishing the use of Drosophila as a model system to probe RecQ4 functions. Immunofluorescence experiments monitoring the cellular distribution of RecQ4 demonstrated that RecQ4 expression peaks during S phase, and RecQ4 is expressed only in tissues active in DNA replication, but not in quiescent cells. We have isolated Drosophila RecQ4 hypomorphic mutants, recq(EP) and recq4(23), which specifically reduce chorion gene amplification of follicle cells by 4-5 fold, resulting in thin and fragile eggshells, and female sterility. Quantitative analysis on amplification defects over a 14-kb domain in chorion gene cluster suggests that RecQ4 may have a specific function at or near the origin of replication. A null allele recq4(19) causes a failure in cell proliferation, decrease in DNA replication, chromosomal fragmentation, and lethality at the stage of first instar larvae. The mosaic analysis indicates that cell clones with homozygous recq4(19) fail to proliferate. These results indicate that RecQ4 is essential for viability and fertility, and is required for most aspects of DNA replication during development.
Collapse
Affiliation(s)
- Jianhong Wu
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | | | | | | |
Collapse
|
39
|
Kusumoto R, Dawut L, Marchetti C, Wan Lee J, Vindigni A, Ramsden D, Bohr VA. Werner protein cooperates with the XRCC4-DNA ligase IV complex in end-processing. Biochemistry 2008; 47:7548-56. [PMID: 18558713 DOI: 10.1021/bi702325t] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Werner syndrome is a rare human disease characterized by the premature onset of aging-associated pathologies, cancer predisposition, and genomic instability. The Werner protein (WRN), which is defective in Werner syndrome ( WS) patients, belongs to the RecQ family helicases and interacts with several DNA metabolic proteins, including DNA repair factors and telomere associated proteins. Nonhomologous end-joining (NHEJ) is an important pathway in the repair of DNA double strand breaks (DSBs), and the DNA-PK complex, composed of the heterodimer Ku 70/86 and the DNA-PK catalytic subunit (DNA-PKcs), together with the XRCC4-DNA ligase IV complex (X4L4), are major factors. One of the most prominent protein interactions of WRN is with Ku 70/86, and it is possible that WRN is involved in NHEJ via its associations with Ku 70/86 and DNA-PKcs. This study demonstrates that WRN physically interacts with the major NHEJ factor, X4L4, which stimulates WRN exonuclease but not its helicase activity. The human RecQ helicase, BLM, which possesses only helicase activity, does not bind to X4L4, and its helicase activity is not affected by X4L4. In a DNA end-joining assay, we find that a substrate, which is processed by WRN, is ligated by X4L4, thus further supporting the significance of their functional interaction.
Collapse
Affiliation(s)
- Rika Kusumoto
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, Maryland 21224, USA
| | | | | | | | | | | | | |
Collapse
|
40
|
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
|
41
|
Two closely related RecQ helicases have antagonistic roles in homologous recombination and DNA repair in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2007; 104:18836-41. [PMID: 18000056 DOI: 10.1073/pnas.0705998104] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
RecQ helicases are involved in the processing of DNA structures arising during replication, recombination, and repair throughout all kingdoms of life. Mutations of different RecQ homologues are responsible for severe human diseases, such as Blooms (BLM) or Werner (WRN) syndrome. The loss of RecQ function is often accompanied by hyperrecombination caused by a lack of crossover suppression. In the Arabidopsis genome seven different RecQ genes are present. Two of them (AtRECQ4A and 4B) arose because of a recent duplication and are still nearly 70% identical on a protein level. Knockout of these genes leads to antagonistic phenotypes: the RECQ4A mutant shows sensitivity to DNA-damaging agents, enhanced homologous recombination (HR) and lethality in a mus81 background. Moreover, mutation of RECQ4A partially suppresses the lethal phenotype of an AtTOP3alpha mutant, a phenomenon that had previously been demonstrated for RecQ homologues of unicellular eukaryotes only. Together, these facts strongly suggest that in plants RECQ4A is functionally equivalent to SGS1 of Saccharomyces cerevisiae and the mammalian BLM protein. In stark contrast, mutants of the closely related RECQ4B are not mutagen-sensitive, not viable in a mus81 background, and unable to suppress the induced lethality caused by loss of TOP3alpha. Moreover, they are strongly impaired in HR. Thus, AtRECQ4B is specifically required to promote but not to suppress crossovers, a role in which it differs from all eukaryotic RecQ homologues known.
Collapse
|
42
|
Abstract
The study of DNA double-strand break (DSB) repair has been greatly facilitated by the use of rare-cutting endonucleases, which induce a break precisely at their cut sites that can be strategically placed in the genome. We previously established such a system in Drosophila and showed that the yeast I-SceI enzyme cuts efficiently in Drosophila cells and those breaks are effectively repaired by conserved mechanisms. In this study, we determined the genetic requirements for the repair of this I-SceI-induced DSB in the germline. We show that Drosophila Rad51 and Rad54 are both required for homologous repair by gene conversion, but are dispensable for single-strand annealing repair. We provided evidence suggesting that Rad51 is more stringently required than Rad54 for intersister gene conversion. We uncovered a significant role of DNA ligase IV in nonhomologous end joining. We conducted a screen for candidate mutations affecting DSB repair and discovered novel mutations in genes that include mutagen sensitive 206, single-strand annealing reducer, and others. In addition, we demonstrated an intricate balance among different repair pathways in which the cell differentially utilizes repair mechanisms in response to both changes in the genomic environment surrounding the break and deficiencies in one or the other repair pathways.
Collapse
Affiliation(s)
- Debbie S Wei
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | |
Collapse
|
43
|
Trowbridge K, McKim K, Brill SJ, Sekelsky J. Synthetic lethality of Drosophila in the absence of the MUS81 endonuclease and the DmBlm helicase is associated with elevated apoptosis. Genetics 2007; 176:1993-2001. [PMID: 17603121 PMCID: PMC1950608 DOI: 10.1534/genetics.106.070060] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mus81-Mms4 (Mus81-Eme1 in some species) is a heterodimeric DNA structure-specific endonuclease that has been implicated in meiotic recombination and processing of damaged replication forks in fungi. We generated and characterized mutations in Drosophila melanogaster mus81 and mms4. Unlike the case in fungi, we did not find any role for MUS81-MMS4 in meiotic crossing over. A possible role for this endonuclease in repairing double-strand breaks that arise during DNA replication is suggested by the finding that mus81 and mms4 mutants are hypersensitive to camptothecin; however, these mutants are not hypersensitive to other agents that generate lesions that slow or block DNA replication. In fungi, mus81, mms4, and eme1 mutations are synthetically lethal with mutations in genes encoding RecQ helicase homologs. Similarly, we found that mutations in Drosophila mus81 and mms4 are synthetically lethal with null mutations in mus309, which encodes the ortholog of the Bloom Syndrome helicase. Synthetic lethality is associated with high levels of apoptosis in proliferating tissues. Lethality and elevated apoptosis were partially suppressed by a mutation in spn-A, which encodes the ortholog of the strand invasion protein Rad51. These findings provide insights into the causes of synthetic lethality.
Collapse
Affiliation(s)
- Kirsten Trowbridge
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | | | | | | |
Collapse
|
44
|
McVey M, Andersen SL, Broze Y, Sekelsky J. Multiple functions of Drosophila BLM helicase in maintenance of genome stability. Genetics 2007; 176:1979-92. [PMID: 17507683 PMCID: PMC1950607 DOI: 10.1534/genetics.106.070052] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Bloom Syndrome, a rare human disorder characterized by genomic instability and predisposition to cancer, is caused by mutation of BLM, which encodes a RecQ-family DNA helicase. The Drosophila melanogaster ortholog of BLM, DmBlm, is encoded by mus309. Mutations in mus309 cause hypersensitivity to DNA-damaging agents, female sterility, and defects in repairing double-strand breaks (DSBs). To better understand these phenotypes, we isolated novel mus309 alleles. Mutations that delete the N terminus of DmBlm, but not the helicase domain, have DSB repair defects as severe as those caused by null mutations. We found that female sterility is due to a requirement for DmBlm in early embryonic cell cycles; embryos lacking maternally derived DmBlm have anaphase bridges and other mitotic defects. These defects were less severe for the N-terminal deletion alleles, so we used one of these mutations to assay meiotic recombination. Crossovers were decreased to about half the normal rate, and the remaining crossovers were evenly distributed along the chromosome. We also found that spontaneous mitotic crossovers are increased by several orders of magnitude in mus309 mutants. These results demonstrate that DmBlm functions in multiple cellular contexts to promote genome stability.
Collapse
Affiliation(s)
- Mitch McVey
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | | | | | | |
Collapse
|
45
|
Johnson-Schlitz DM, Flores C, Engels WR. Multiple-pathway analysis of double-strand break repair mutations in Drosophila. PLoS Genet 2007; 3:e50. [PMID: 17432935 PMCID: PMC1851981 DOI: 10.1371/journal.pgen.0030050] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2007] [Accepted: 02/20/2007] [Indexed: 11/19/2022] Open
Abstract
The analysis of double-strand break (DSB) repair is complicated by the existence of several pathways utilizing a large number of genes. Moreover, many of these genes have been shown to have multiple roles in DSB repair. To address this complexity we used a repair reporter construct designed to measure multiple repair outcomes simultaneously. This approach provides estimates of the relative usage of several DSB repair pathways in the premeiotic male germline of Drosophila. We applied this system to mutations at each of 11 repair loci plus various double mutants and altered dosage genotypes. Most of the mutants were found to suppress one of the pathways with a compensating increase in one or more of the others. Perhaps surprisingly, none of the single mutants suppressed more than one pathway, but they varied widely in how the suppression was compensated. We found several cases in which two or more loci were similar in which pathway was suppressed while differing in how this suppression was compensated. Taken as a whole, the data suggest that the choice of which repair pathway is used for a given DSB occurs by a two-stage "decision circuit" in which the DSB is first placed into one of two pools from which a specific pathway is then selected.
Collapse
Affiliation(s)
- Dena M Johnson-Schlitz
- Department of Genetics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Carlos Flores
- Department of Genetics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - William R Engels
- Department of Genetics, University of Wisconsin, Madison, Wisconsin, United States of America
- * To whom correspondence should be addressed. E-mail:
| |
Collapse
|
46
|
Weinert BT, Rio DC. DNA strand displacement, strand annealing and strand swapping by the Drosophila Bloom's syndrome helicase. Nucleic Acids Res 2007; 35:1367-76. [PMID: 17272294 PMCID: PMC1849897 DOI: 10.1093/nar/gkl831] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Genetic analysis of the Drosophila Bloom's syndrome helicase homolog (mus309/DmBLM) indicates that DmBLM is required for the synthesis-dependent strand annealing (SDSA) pathway of homologous recombination. Here we report the first biochemical study of DmBLM. Recombinant, epitope-tagged DmBLM was expressed in Drosophila cell culture and highly purified protein was prepared from nuclear extracts. Purified DmBLM exists exclusively as a high molecular weight (∼1.17 MDa) species, is a DNA-dependent ATPase, has 3′→5′ DNA helicase activity, prefers forked substrate DNAs and anneals complementary DNAs. High-affinity DNA binding is ATP-dependent and low-affinity ATP-independent interactions contribute to forked substrate DNA binding and drive strand annealing. DmBLM combines DNA strand displacement with DNA strand annealing to catalyze the displacement of one DNA strand while annealing a second complementary DNA strand.
Collapse
Affiliation(s)
| | - Donald C. Rio
- To whom correspondence should be addressed. Tel: +1 510 642 1071; Fax: +1 510 642 6062;
| |
Collapse
|
47
|
Johnson-Schlitz D, Engels WR. Template disruptions and failure of double Holliday junction dissolution during double-strand break repair in Drosophila BLM mutants. Proc Natl Acad Sci U S A 2006; 103:16840-5. [PMID: 17075047 PMCID: PMC1636541 DOI: 10.1073/pnas.0607904103] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Previous biochemical studies of the BLM gene product have shown its ability in conjunction with topoisomerase IIIalpha to resolve double Holliday structures through a process called "dissolution." This process could prevent crossing over during repair of double-strand breaks. We report an analysis of the Drosophila BLM gene, DmBlm, in the repair of double-strand breaks in the premeiotic germ line of Drosophila males. With a repair reporter construct, Rr3, and other genetic tools, we show that DmBlm mutants are defective for homologous repair but show a compensating increase in single-strand annealing. Increases of 40- to 50-fold in crossing over and flanking deletions also were seen. Perhaps most significantly, the template used for homologous repair in DmBlm mutants is itself subject to deletions and complex rearrangements. These template disruptions are indicative of failure to resolve double Holliday junctions. These findings, along with the demonstration that a weak allele of topoisomerase IIIalpha has some of the same defects as DmBlm, support the dissolution model. Finally, an analysis of DmBlm mutants in conjunction with mus81 or spnA (Rad51) reveals a second function of BLM distinct from the repair of induced double-strand breaks and possibly related to maintenance of replication forks.
Collapse
Affiliation(s)
| | - William R. Engels
- Genetics Department, University of Wisconsin, Madison, WI 53706
- To whom correspondence should be addressed. E-mail:
| |
Collapse
|
48
|
Sharma S, Doherty K, Brosh R. Mechanisms of RecQ helicases in pathways of DNA metabolism and maintenance of genomic stability. Biochem J 2006; 398:319-37. [PMID: 16925525 PMCID: PMC1559444 DOI: 10.1042/bj20060450] [Citation(s) in RCA: 193] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Helicases are molecular motor proteins that couple the hydrolysis of NTP to nucleic acid unwinding. The growing number of DNA helicases implicated in human disease suggests that their vital specialized roles in cellular pathways are important for the maintenance of genome stability. In particular, mutations in genes of the RecQ family of DNA helicases result in chromosomal instability diseases of premature aging and/or cancer predisposition. We will discuss the mechanisms of RecQ helicases in pathways of DNA metabolism. A review of RecQ helicases from bacteria to human reveals their importance in genomic stability by their participation with other proteins to resolve DNA replication and recombination intermediates. In the light of their known catalytic activities and protein interactions, proposed models for RecQ function will be summarized with an emphasis on how this distinct class of enzymes functions in chromosomal stability maintenance and prevention of human disease and cancer.
Collapse
Affiliation(s)
- Sudha Sharma
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, U.S.A
| | - Kevin M. Doherty
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, U.S.A
| | - Robert M. Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, U.S.A
- To whom correspondence should be addressed (email )
| |
Collapse
|
49
|
Lankenau DH. Germline Double-Strand Break Repair and Gene Targeting in Drosophila: A Trajectory System throughout Evolution. Genome Integr 2006. [DOI: 10.1007/7050_019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
|
50
|
Chester N, Babbe H, Pinkas J, Manning C, Leder P. Mutation of the murine Bloom's syndrome gene produces global genome destabilization. Mol Cell Biol 2006; 26:6713-26. [PMID: 16914751 PMCID: PMC1592839 DOI: 10.1128/mcb.00296-06] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Revised: 03/16/2006] [Accepted: 06/15/2006] [Indexed: 11/20/2022] Open
Abstract
Bloom's syndrome (BS) is a genetic disorder characterized cellularly by increases in sister chromatid exchanges (SCEs) and numbers of micronuclei. BS is caused by mutation in the BLM DNA helicase gene and involves a greatly enhanced risk of developing the range of malignancies seen in the general population. With a mouse model for the disease, we set out to determine the relationship between genomic instability and neoplasia. We used a novel two-step analysis to investigate a panel of eight cell lines developed from mammary tumors that appeared in Blm conditional knockout mice. First, the panel of cell lines was examined for instability. High numbers of SCEs were uniformly seen in members of the panel, and several lines produced chromosomal instability (CIN) manifested by high numbers of chromosomal structural aberrations (CAs) and chromosome missegregation events. Second, to see if Blm mutation was responsible for the CIN, time-dependent analysis was conducted on a tumor line harboring a functional floxed Blm allele. The floxed allele was deleted in vitro, and mutant as well as control subclones were cultured for 100 passages. By passage 100, six of nine mutant subclones had acquired high CIN. Nine mutant subclones produced 50-fold more CAs than did nine control subclones. Finally, chromosome loss preceded the appearance of CIN, suggesting that this loss provides a potential mechanism for the induction of instability in mutant subclones. Such aneuploidy or CIN is a universal feature of neoplasia but has an uncertain function in oncogenesis. Our results show that Blm gene mutation produces this instability, strengthening a role for CIN in the development of human cancer.
Collapse
Affiliation(s)
- Nicholas Chester
- Department of Genetics, Harvard Medical School, 356 New Research Building, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.
| | | | | | | | | |
Collapse
|