1
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Herriage HC, Huang YT, Calvi BR. The antagonistic relationship between apoptosis and polyploidy in development and cancer. Semin Cell Dev Biol 2024; 156:35-43. [PMID: 37331841 PMCID: PMC10724375 DOI: 10.1016/j.semcdb.2023.05.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 05/23/2023] [Accepted: 05/30/2023] [Indexed: 06/20/2023]
Abstract
One of the important functions of regulated cell death is to prevent cells from inappropriately acquiring extra copies of their genome, a state known as polyploidy. Apoptosis is the primary cell death mechanism that prevents polyploidy, and defects in this apoptotic response can result in polyploid cells whose subsequent error-prone chromosome segregation are a major contributor to genome instability and cancer progression. Conversely, some cells actively repress apoptosis to become polyploid as part of normal development or regeneration. Thus, although apoptosis prevents polyploidy, the polyploid state can actively repress apoptosis. In this review, we discuss progress in understanding the antagonistic relationship between apoptosis and polyploidy in development and cancer. Despite recent advances, a key conclusion is that much remains unknown about the mechanisms that link apoptosis to polyploid cell cycles. We suggest that drawing parallels between the regulation of apoptosis in development and cancer could help to fill this knowledge gap and lead to more effective therapies.
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Affiliation(s)
- Hunter C Herriage
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Yi-Ting Huang
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Brian R Calvi
- Department of Biology, Indiana University, Bloomington, IN 47405, USA.
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2
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Darmasaputra GS, van Rijnberk LM, Galli M. Functional consequences of somatic polyploidy in development. Development 2024; 151:dev202392. [PMID: 38415794 PMCID: PMC10946441 DOI: 10.1242/dev.202392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Polyploid cells contain multiple genome copies and arise in many animal tissues as a regulated part of development. However, polyploid cells can also arise due to cell division failure, DNA damage or tissue damage. Although polyploidization is crucial for the integrity and function of many tissues, the cellular and tissue-wide consequences of polyploidy can be very diverse. Nonetheless, many polyploid cell types and tissues share a remarkable similarity in function, providing important information about the possible contribution of polyploidy to cell and tissue function. Here, we review studies on polyploid cells in development, underlining parallel functions between different polyploid cell types, as well as differences between developmentally-programmed and stress-induced polyploidy.
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Affiliation(s)
- Gabriella S. Darmasaputra
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, the Netherlands
| | - Lotte M. van Rijnberk
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, the Netherlands
| | - Matilde Galli
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, the Netherlands
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3
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Wang Y, Tamori Y. Polyploid Cancer Cell Models in Drosophila. Genes (Basel) 2024; 15:96. [PMID: 38254985 PMCID: PMC10815460 DOI: 10.3390/genes15010096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 01/04/2024] [Accepted: 01/12/2024] [Indexed: 01/24/2024] Open
Abstract
Cells with an abnormal number of chromosomes have been found in more than 90% of solid tumors, and among these, polyploidy accounts for about 40%. Polyploidized cells most often have duplicate centrosomes as well as genomes, and thus their mitosis tends to promote merotelic spindle attachments and chromosomal instability, which produces a variety of aneuploid daughter cells. Polyploid cells have been found highly resistant to various stress and anticancer therapies, such as radiation and mitogenic inhibitors. In other words, common cancer therapies kill proliferative diploid cells, which make up the majority of cancer tissues, while polyploid cells, which lurk in smaller numbers, may survive. The surviving polyploid cells, prompted by acute environmental changes, begin to mitose with chromosomal instability, leading to an explosion of genetic heterogeneity and a concomitant cell competition and adaptive evolution. The result is a recurrence of the cancer during which the tenacious cells that survived treatment express malignant traits. Although the presence of polyploid cells in cancer tissues has been observed for more than 150 years, the function and exact role of these cells in cancer progression has remained elusive. For this reason, there is currently no effective therapeutic treatment directed against polyploid cells. This is due in part to the lack of suitable experimental models, but recently several models have become available to study polyploid cells in vivo. We propose that the experimental models in Drosophila, for which genetic techniques are highly developed, could be very useful in deciphering mechanisms of polyploidy and its role in cancer progression.
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Affiliation(s)
| | - Yoichiro Tamori
- Department of Molecular Oncology, Kyoto University Graduate School of Medicine, Kyoto 606-8501, Japan
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4
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Hill HJ, Bonser D, Golic KG. Dicentric chromosome breakage in Drosophila melanogaster is influenced by pericentric heterochromatin and occurs in nonconserved hotspots. Genetics 2023; 224:iyad052. [PMID: 37010100 PMCID: PMC10213500 DOI: 10.1093/genetics/iyad052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 10/18/2022] [Accepted: 03/13/2023] [Indexed: 04/04/2023] Open
Abstract
Chromosome breakage plays an important role in the evolution of karyotypes and can produce deleterious effects within a single individual, such as aneuploidy or cancer. Forces that influence how and where chromosomes break are not fully understood. In humans, breakage tends to occur in conserved hotspots called common fragile sites (CFS), especially during replication stress. By following the fate of dicentric chromosomes in Drosophila melanogaster, we find that breakage under tension also tends to occur in specific hotspots. Our experimental approach was to induce sister chromatid exchange in a ring chromosome to generate a dicentric chromosome with a double chromatid bridge. In the following cell division, the dicentric bridges may break. We analyzed the breakage patterns of 3 different ring-X chromosomes. These chromosomes differ by the amount and quality of heterochromatin they carry as well as their genealogical history. For all 3 chromosomes, breakage occurs preferentially in several hotspots. Surprisingly, we found that the hotspot locations are not conserved between the 3 chromosomes: each displays a unique array of breakage hotspots. The lack of hotspot conservation, along with a lack of response to aphidicolin, suggests that these breakage sites are not entirely analogous to CFS and may reveal new mechanisms of chromosome fragility. Additionally, the frequency of dicentric breakage and the durability of each chromosome's spindle attachment vary significantly between the 3 chromosomes and are correlated with the origin of the centromere and the amount of pericentric heterochromatin. We suggest that different centromere strengths could account for this.
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Affiliation(s)
- Hunter J Hill
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Danielle Bonser
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Kent G Golic
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
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5
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Shimell M, O'Connor MB. Endoreplication in the Drosophila melanogaster prothoracic gland is dispensable for the critical weight checkpoint. MICROPUBLICATION BIOLOGY 2023; 2023:10.17912/micropub.biology.000741. [PMID: 36908310 PMCID: PMC9996309 DOI: 10.17912/micropub.biology.000741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 02/06/2023] [Accepted: 02/11/2023] [Indexed: 03/14/2023]
Abstract
Critical weight (CW) attainment is a key life event in the development of holometabolous insects including Drosophila melanogaster. It indicates that sufficient growth has occurred to initiate the juvenile-to-adult transition. The prothoracic gland (PG), the major insect larval endocrine organ, is a polyploid tissue that plays a key role in the determination of CW via release of the steroid hormone ecdysone. Here we show that when the cells of the PG fail to make the mitotic-to-endocycle switch, but instead remain mitotic, the result is more but smaller cells. Nevertheless, they reach the same CW and produce healthy adults after only a moderate developmental delay. We propose that the CW checkpoint can be reached by either an endocycling or mitotic PG and may simply reflect the attainment of sufficient ecdysone biosynthetic capacity to initiate metamorphosis.
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Affiliation(s)
- MaryJane Shimell
- Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota, United States
| | - Michael B O'Connor
- Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota, United States
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6
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Edwards MM, Zuccaro MV, Sagi I, Ding Q, Vershkov D, Benvenisty N, Egli D, Koren A. Delayed DNA replication in haploid human embryonic stem cells. Genome Res 2021; 31:2155-2169. [PMID: 34810218 PMCID: PMC8647822 DOI: 10.1101/gr.275953.121] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 10/20/2021] [Indexed: 11/25/2022]
Abstract
Haploid human embryonic stem cells (ESCs) provide a powerful genetic system but diploidize at high rates. We hypothesized that diploidization results from aberrant DNA replication. To test this, we profiled DNA replication timing in isogenic haploid and diploid ESCs. The greatest difference was the earlier replication of the X Chromosome in haploids, consistent with the lack of X-Chromosome inactivation. We also identified 21 autosomal regions that had delayed replication in haploids, extending beyond the normal S phase and into G2/M. Haploid-delays comprised a unique set of quiescent genomic regions that are also underreplicated in polyploid placental cells. The same delays were observed in female ESCs with two active X Chromosomes, suggesting that increased X-Chromosome dosage may cause delayed autosomal replication. We propose that incomplete replication at the onset of mitosis could prevent cell division and result in re-entry into the cell cycle and whole genome duplication.
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Affiliation(s)
- Matthew M Edwards
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
| | - Michael V Zuccaro
- Department of Pediatrics and Naomi Berrie Diabetes Center, Columbia University, New York, New York 10032, USA
- Columbia University Stem Cell Initiative, New York, New York 10032, USA
| | - Ido Sagi
- The Azrieli Center for Stem Cells and Genetic Research, Department of Genetics, Silberman Institute of Life Sciences, The Hebrew University, Jerusalem 91904, Israel
| | - Qiliang Ding
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
| | - Dan Vershkov
- The Azrieli Center for Stem Cells and Genetic Research, Department of Genetics, Silberman Institute of Life Sciences, The Hebrew University, Jerusalem 91904, Israel
| | - Nissim Benvenisty
- The Azrieli Center for Stem Cells and Genetic Research, Department of Genetics, Silberman Institute of Life Sciences, The Hebrew University, Jerusalem 91904, Israel
| | - Dieter Egli
- Department of Pediatrics and Naomi Berrie Diabetes Center, Columbia University, New York, New York 10032, USA
- Columbia University Stem Cell Initiative, New York, New York 10032, USA
| | - Amnon Koren
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
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7
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Das S, Caballero M, Kolesnikova T, Zhimulev I, Koren A, Nordman J. Replication timing analysis in polyploid cells reveals Rif1 uses multiple mechanisms to promote underreplication in Drosophila. Genetics 2021; 219:6369517. [PMID: 34740250 PMCID: PMC8570783 DOI: 10.1093/genetics/iyab147] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 09/01/2021] [Indexed: 11/23/2022] Open
Abstract
Regulation of DNA replication and copy number is necessary to promote genome stability and maintain cell and tissue function. DNA replication is regulated temporally in a process known as replication timing (RT). Rap1-interacting factor 1 (Rif1) is a key regulator of RT and has a critical function in copy number control in polyploid cells. Previously, we demonstrated that Rif1 functions with SUUR to inhibit replication fork progression and promote underreplication (UR) of specific genomic regions. How Rif1-dependent control of RT factors into its ability to promote UR is unknown. By applying a computational approach to measure RT in Drosophila polyploid cells, we show that SUUR and Rif1 have differential roles in controlling UR and RT. Our findings reveal that Rif1 acts to promote late replication, which is necessary for SUUR-dependent underreplication. Our work provides new insight into the process of UR and its links to RT.
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Affiliation(s)
- Souradip Das
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA
| | - Madison Caballero
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Tatyana Kolesnikova
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia.,Laboratory of Structural, Functional and Comparative Genomics, Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Igor Zhimulev
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia.,Laboratory of Structural, Functional and Comparative Genomics, Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Amnon Koren
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Jared Nordman
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA
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8
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Bailey EC, Kobielski S, Park J, Losick VP. Polyploidy in Tissue Repair and Regeneration. Cold Spring Harb Perspect Biol 2021; 13:a040881. [PMID: 34187807 PMCID: PMC8485745 DOI: 10.1101/cshperspect.a040881] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Polyploidy is defined as a cell with three or more whole genome sets and enables cell growth across the kingdoms of life. Studies in model organisms have revealed that polyploid cell growth can be required for optimal tissue repair and regeneration. In mammals, polyploid cell growth contributes to repair of many tissues, including the liver, heart, kidney, bladder, and eye, and similar strategies have been identified in Drosophila and zebrafish tissues. This review discusses the heterogeneity and versatility of polyploidy in tissue repair and regeneration. Polyploidy has been shown to restore tissue mass and maintain organ size as well as protect against oncogenic insults and genotoxic stress. Polyploid cells can also serve as a reservoir for new diploid cells in regeneration. The numerous mechanisms to generate polyploid cells provide an unlimited resource for tissues to exploit to undergo repair or regeneration.
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Affiliation(s)
- Erin C Bailey
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Sara Kobielski
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - John Park
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Vicki P Losick
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467, USA
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9
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Kim M, Delos Santos K, Moon NS. Proper CycE-Cdk2 activity in endocycling tissues requires regulation of the cyclin-dependent kinase inhibitor Dacapo by dE2F1b in Drosophila. Genetics 2021; 217:1-15. [PMID: 33683365 DOI: 10.1093/genetics/iyaa029] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Accepted: 12/06/2020] [Indexed: 01/05/2023] Open
Abstract
Polyploidy is an integral part of development and is associated with cellular stress, aging, and pathological conditions. The endocycle, comprised of successive rounds of G and S phases without mitosis, is widely employed to produce polyploid cells in plants and animals. In Drosophila, maintenance of the endocycle is dependent on E2F-governed oscillations of Cyclin E (CycE)-Cdk2 activity, which is known to be largely regulated at the level of transcription. In this study, we report an additional level of E2F-dependent control of CycE-Cdk2 activity during the endocycle. Genetic experiments revealed that an alternative isoform of Drosophila de2f1, dE2F1b, regulates the expression of the p27CIP/KIP-like Cdk inhibitor Dacapo (Dap). We provide evidence showing that dE2F1b-dependent Dap expression in endocycling tissues is necessary for setting proper CycE-Cdk2 activity. Furthermore, we demonstrate that dE2F1b is required for proliferating cell nuclear antigen expression that establishes a negative feedback loop in S phase. Overall, our study reveals previously unappreciated E2F-dependent regulatory networks that are critical for the periodic transition between G and S phases during the endocycle.
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Affiliation(s)
- Minhee Kim
- Department of Biology, Developmental Biology Research Initiative, McGill University, Montreal, Quebec H3A 1B1 Canada
| | - Keemo Delos Santos
- Department of Biology, Developmental Biology Research Initiative, McGill University, Montreal, Quebec H3A 1B1 Canada
| | - Nam-Sung Moon
- Department of Biology, Developmental Biology Research Initiative, McGill University, Montreal, Quebec H3A 1B1 Canada
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10
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Wear EE, Song J, Zynda GJ, Mickelson-Young L, LeBlanc C, Lee TJ, Deppong DO, Allen GC, Martienssen RA, Vaughn MW, Hanley-Bowdoin L, Thompson WF. Comparing DNA replication programs reveals large timing shifts at centromeres of endocycling cells in maize roots. PLoS Genet 2020; 16:e1008623. [PMID: 33052904 PMCID: PMC7588055 DOI: 10.1371/journal.pgen.1008623] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Revised: 10/26/2020] [Accepted: 08/28/2020] [Indexed: 12/20/2022] Open
Abstract
Plant cells undergo two types of cell cycles–the mitotic cycle in which DNA replication is coupled to mitosis, and the endocycle in which DNA replication occurs in the absence of cell division. To investigate DNA replication programs in these two types of cell cycles, we pulse labeled intact root tips of maize (Zea mays) with 5-ethynyl-2’-deoxyuridine (EdU) and used flow sorting of nuclei to examine DNA replication timing (RT) during the transition from a mitotic cycle to an endocycle. Comparison of the sequence-based RT profiles showed that most regions of the maize genome replicate at the same time during S phase in mitotic and endocycling cells, despite the need to replicate twice as much DNA in the endocycle and the fact that endocycling is typically associated with cell differentiation. However, regions collectively corresponding to 2% of the genome displayed significant changes in timing between the two types of cell cycles. The majority of these regions are small with a median size of 135 kb, shift to a later RT in the endocycle, and are enriched for genes expressed in the root tip. We found larger regions that shifted RT in centromeres of seven of the ten maize chromosomes. These regions covered the majority of the previously defined functional centromere, which ranged between 1 and 2 Mb in size in the reference genome. They replicate mainly during mid S phase in mitotic cells but primarily in late S phase of the endocycle. In contrast, the immediately adjacent pericentromere sequences are primarily late replicating in both cell cycles. Analysis of CENH3 enrichment levels in 8C vs 2C nuclei suggested that there is only a partial replacement of CENH3 nucleosomes after endocycle replication is complete. The shift to later replication of centromeres and possible reduction in CENH3 enrichment after endocycle replication is consistent with a hypothesis that centromeres are inactivated when their function is no longer needed. In traditional cell division, or mitosis, a cell’s genetic material is duplicated and then split between two daughter cells. In contrast, in some specialized cell types, the DNA is duplicated a second time without an intervening division step, resulting in cells that carry twice as much DNA. This phenomenon, which is called the endocycle, is common during plant development. At each step, DNA replication follows an ordered program in which highly compacted DNA is unraveled and replicated in sections at different times during the synthesis (S) phase. In plants, it is unclear whether traditional and endocycle programs are the same, especially since endocycling cells are typically in the process of differentiation. Using root tips of maize, we found that in comparison to replication in the mitotic cell cycle, there is a small portion of the genome whose replication in the endocycle is shifted in time, usually to later in S phase. Some of these regions are scattered around the genome and mostly coincide with active genes. However, the most prominent shifts occur in centromeres. The shift to later replication in centromeres is noteworthy because they orchestrate the process of separating duplicated chromosomes into daughter cells, a function that is not needed in the endocycle.
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Affiliation(s)
- Emily E. Wear
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
- * E-mail:
| | - Jawon Song
- Texas Advanced Computing Center, University of Texas, Austin, Texas, United States of America
| | - Gregory J. Zynda
- Texas Advanced Computing Center, University of Texas, Austin, Texas, United States of America
| | - Leigh Mickelson-Young
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Chantal LeBlanc
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Tae-Jin Lee
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - David O. Deppong
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - George C. Allen
- Department of Horticultural Science, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Robert A. Martienssen
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Matthew W. Vaughn
- Texas Advanced Computing Center, University of Texas, Austin, Texas, United States of America
| | - Linda Hanley-Bowdoin
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - William F. Thompson
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
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11
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Mamun MA, Albergante L, J Blow J, Newman TJ. 3 tera-basepairs as a fundamental limit for robust DNA replication. Phys Biol 2020; 17:046002. [PMID: 32320972 DOI: 10.1088/1478-3975/ab8c2f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In order to maintain functional robustness and species integrity, organisms must ensure high fidelity of the genome duplication process. This is particularly true during early development, where cell division is often occurring both rapidly and coherently. By studying the extreme limits of suppressing DNA replication failure due to double fork stall errors, we uncover a fundamental constant that describes a trade-off between genome size and architectural complexity of the developing organism. This constant has the approximate value N U ≈ 3 × 1012 basepairs, and depends only on two highly conserved molecular properties of DNA biology. We show that our theory is successful in interpreting a diverse range of data across the Eukaryota.
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Affiliation(s)
- M Al Mamun
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom. CIB-CSIC, Madrid 28040, Spain
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12
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Sun T, Song Y, Dai J, Mao D, Ma M, Ni JQ, Liang X, Pastor-Pareja JC. Spectraplakin Shot Maintains Perinuclear Microtubule Organization in Drosophila Polyploid Cells. Dev Cell 2019; 49:731-747.e7. [DOI: 10.1016/j.devcel.2019.03.027] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 02/05/2019] [Accepted: 03/26/2019] [Indexed: 02/06/2023]
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13
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Nuclear Scaling Is Coordinated among Individual Nuclei in Multinucleated Muscle Fibers. Dev Cell 2019; 49:48-62.e3. [PMID: 30905770 DOI: 10.1016/j.devcel.2019.02.020] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 11/28/2018] [Accepted: 02/22/2019] [Indexed: 12/22/2022]
Abstract
Optimal cell performance depends on cell size and the appropriate relative size, i.e., scaling, of the nucleus. How nuclear scaling is regulated and contributes to cell function is poorly understood, especially in skeletal muscle fibers, which are among the largest cells, containing hundreds of nuclei. Here, we present a Drosophila in vivo system to analyze nuclear scaling in whole multinucleated muscle fibers, genetically manipulate individual components, and assess muscle function. Despite precise global coordination, we find that individual nuclei within a myofiber establish different local scaling relationships by adjusting their size and synthetic activity in correlation with positional or spatial cues. While myonuclei exhibit compensatory potential, even minor changes in global nuclear size scaling correlate with reduced muscle function. Our study provides the first comprehensive approach to unraveling the intrinsic regulation of size in multinucleated muscle fibers. These insights to muscle cell biology will accelerate the development of interventions for muscle diseases.
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14
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Sequeira-Mendes J, Vergara Z, Peiró R, Morata J, Aragüez I, Costas C, Mendez-Giraldez R, Casacuberta JM, Bastolla U, Gutierrez C. Differences in firing efficiency, chromatin, and transcription underlie the developmental plasticity of the Arabidopsis DNA replication origins. Genome Res 2019; 29:784-797. [PMID: 30846531 PMCID: PMC6499314 DOI: 10.1101/gr.240986.118] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 02/25/2019] [Indexed: 12/20/2022]
Abstract
Eukaryotic genome replication depends on thousands of DNA replication origins (ORIs). A major challenge is to learn ORI biology in multicellular organisms in the context of growing organs to understand their developmental plasticity. We have identified a set of ORIs of Arabidopsis thaliana and their chromatin landscape at two stages of post-embryonic development. ORIs associate with multiple chromatin signatures including transcription start sites (TSS) but also proximal and distal regulatory regions and heterochromatin, where ORIs colocalize with retrotransposons. In addition, quantitative analysis of ORI activity led us to conclude that strong ORIs have high GC content and clusters of GGN trinucleotides. Development primarily influences ORI firing strength rather than ORI location. ORIs that preferentially fire at early developmental stages colocalize with GC-rich heterochromatin, but at later stages with transcribed genes, perhaps as a consequence of changes in chromatin features associated with developmental processes. Our study provides the set of ORIs active in an organism at the post-embryo stage that should allow us to study ORI biology in response to development, environment, and mutations with a quantitative approach. In a wider scope, the computational strategies developed here can be transferred to other eukaryotic systems.
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Affiliation(s)
- Joana Sequeira-Mendes
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
| | - Zaida Vergara
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
| | - Ramon Peiró
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
| | - Jordi Morata
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus Universitat Autónoma de Barcelona, Bellaterra, Cerdanyola del Valles, 08193 Barcelona, Spain
| | - Irene Aragüez
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
| | - Celina Costas
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
| | - Raul Mendez-Giraldez
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
| | - Josep M Casacuberta
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus Universitat Autónoma de Barcelona, Bellaterra, Cerdanyola del Valles, 08193 Barcelona, Spain
| | - Ugo Bastolla
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
| | - Crisanto Gutierrez
- Centro de Biologia Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049 Madrid, Spain
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15
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Gjelsvik KJ, Besen-McNally R, Losick VP. Solving the Polyploid Mystery in Health and Disease. Trends Genet 2019; 35:6-14. [PMID: 30470486 PMCID: PMC6457904 DOI: 10.1016/j.tig.2018.10.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 10/12/2018] [Accepted: 10/22/2018] [Indexed: 01/12/2023]
Abstract
Polyploidy (the more than doubling of a cell's genome) frequently arises during organogenesis, tissue repair, and age-associated diseases. Despite its prevalence, major gaps exist in how polyploid cells emerge and affect tissue function. Studies have begun to elucidate the signals required for polyploid cell growth as well as the advantages and disadvantages of polyploidy in health and disease. This review highlights the recent advances on the role and regulation of polyploidy in Drosophila and vertebrate models. The newly discovered versatility of polyploid cells has the potential to provide alternative strategies to promote tissue growth and repair, while limiting disease and dysfunction.
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Affiliation(s)
- K J Gjelsvik
- MDI Biological Laboratory, 159 Old Bar Harbor Road, Bar Harbor, ME 04609, USA
| | - R Besen-McNally
- MDI Biological Laboratory, 159 Old Bar Harbor Road, Bar Harbor, ME 04609, USA
| | - V P Losick
- MDI Biological Laboratory, 159 Old Bar Harbor Road, Bar Harbor, ME 04609, USA.
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16
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Munden A, Rong Z, Sun A, Gangula R, Mallal S, Nordman JT. Rif1 inhibits replication fork progression and controls DNA copy number in Drosophila. eLife 2018; 7:39140. [PMID: 30277458 PMCID: PMC6185109 DOI: 10.7554/elife.39140] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 10/01/2018] [Indexed: 12/22/2022] Open
Abstract
Control of DNA copy number is essential to maintain genome stability and ensure proper cell and tissue function. In Drosophila polyploid cells, the SNF2-domain-containing SUUR protein inhibits replication fork progression within specific regions of the genome to promote DNA underreplication. While dissecting the function of SUUR's SNF2 domain, we identified an interaction between SUUR and Rif1. Rif1 has many roles in DNA metabolism and regulates the replication timing program. We demonstrate that repression of DNA replication is dependent on Rif1. Rif1 localizes to active replication forks in a partially SUUR-dependent manner and directly regulates replication fork progression. Importantly, SUUR associates with replication forks in the absence of Rif1, indicating that Rif1 acts downstream of SUUR to inhibit fork progression. Our findings uncover an unrecognized function of the Rif1 protein as a regulator of replication fork progression.
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Affiliation(s)
- Alexander Munden
- Department of Biological Sciences, Vanderbilt University, Nashville, United States
| | - Zhan Rong
- Department of Biological Sciences, Vanderbilt University, Nashville, United States
| | - Amanda Sun
- Department of Biological Sciences, Vanderbilt University, Nashville, United States
| | - Rama Gangula
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, United States
| | - Simon Mallal
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, United States.,Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, United States
| | - Jared T Nordman
- Department of Biological Sciences, Vanderbilt University, Nashville, United States
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17
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Dynamic changes in ORC localization and replication fork progression during tissue differentiation. BMC Genomics 2018; 19:623. [PMID: 30134926 PMCID: PMC6103881 DOI: 10.1186/s12864-018-4992-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 08/02/2018] [Indexed: 12/23/2022] Open
Abstract
Background Genomic regions repressed for DNA replication, resulting in either delayed replication in S phase or underreplication in polyploid cells, are thought to be controlled by inhibition of replication origin activation. Studies in Drosophila polytene cells, however, raised the possibility that impeding replication fork progression also plays a major role. Results We exploited genomic regions underreplicated (URs) with tissue specificity in Drosophila polytene cells to analyze mechanisms of replication repression. By localizing the Origin Recognition Complex (ORC) in the genome of the larval fat body and comparing this to ORC binding in the salivary gland, we found that sites of ORC binding show extensive tissue specificity. In contrast, there are common domains nearly devoid of ORC in the salivary gland and fat body that also have reduced density of ORC binding sites in diploid cells. Strikingly, domains lacking ORC can still be replicated in some polytene tissues, showing absence of ORC and origins is insufficient to repress replication. Analysis of the width and location of the URs with respect to ORC position indicates that whether or not a genomic region lacking ORC is replicated is controlled by whether replication forks formed outside the region are inhibited. Conclusions These studies demonstrate that inhibition of replication fork progression can block replication across genomic regions that constitutively lack ORC. Replication fork progression can be inhibited in both tissue-specific and genome region-specific ways. Consequently, when evaluating sources of genome instability it is important to consider altered control of replication forks in response to differentiation. Electronic supplementary material The online version of this article (10.1186/s12864-018-4992-3) contains supplementary material, which is available to authorized users.
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18
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Okano-Uchida T, Kent LN, Ouseph MM, McCarty B, Frank JJ, Kladney R, Cuitino MC, Thompson JC, Coppola V, Asano M, Leone G. Endoreduplication of the mouse genome in the absence of ORC1. Genes Dev 2018; 32:978-990. [PMID: 29967292 PMCID: PMC6075035 DOI: 10.1101/gad.311910.118] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 05/09/2018] [Indexed: 01/24/2023]
Abstract
In this study, Okano-Uchida et al. describe the physiological role of ORC1 in mice by generating knock-in mice with LoxP sites flanking exons encoding the critical ATPase domain of ORC1. They show that ORC1 ablation in extraembryonic trophoblasts and hepatocytes failed to impede genome endoreduplication and organ development and function and conclude that ORC1 in mice is essential for mitotic cell divisions but dispensable for endoreduplication. The largest subunit of the origin recognition complex (ORC1) is essential for assembly of the prereplicative complex, firing of DNA replication origins, and faithful duplication of the genome. Here, we generated knock-in mice with LoxP sites flanking exons encoding the critical ATPase domain of ORC1. Global or tissue-specific ablation of ORC1 function in mouse embryo fibroblasts and fetal and adult diploid tissues blocked DNA replication, cell lineage expansion, and organ development. Remarkably, ORC1 ablation in extraembryonic trophoblasts and hepatocytes, two polyploid cell types in mice, failed to impede genome endoreduplication and organ development and function. Thus, ORC1 in mice is essential for mitotic cell divisions but dispensable for endoreduplication. We propose that DNA replication of mammalian polyploid genomes uses a distinct ORC1-independent mechanism.
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Affiliation(s)
- Takayuki Okano-Uchida
- Department of Biochemistry and Molecular Biology, Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina 29425, USA
| | - Lindsey N Kent
- Department of Biochemistry and Molecular Biology, Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina 29425, USA
| | - Madhu M Ouseph
- Solid Tumor Biology Program, Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210, USA.,Department of Cancer Biology and Genetics, Ohio State University, Columbus, Ohio 43210, USA
| | - Britney McCarty
- Solid Tumor Biology Program, Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210, USA.,Department of Cancer Biology and Genetics, Ohio State University, Columbus, Ohio 43210, USA
| | - Jeffrey J Frank
- Solid Tumor Biology Program, Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210, USA.,Department of Cancer Biology and Genetics, Ohio State University, Columbus, Ohio 43210, USA
| | - Raleigh Kladney
- Solid Tumor Biology Program, Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210, USA.,Department of Cancer Biology and Genetics, Ohio State University, Columbus, Ohio 43210, USA
| | - Maria C Cuitino
- Department of Biochemistry and Molecular Biology, Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina 29425, USA
| | - John C Thompson
- Solid Tumor Biology Program, Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210, USA.,Department of Cancer Biology and Genetics, Ohio State University, Columbus, Ohio 43210, USA
| | - Vincenzo Coppola
- Solid Tumor Biology Program, Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210, USA.,Department of Cancer Biology and Genetics, Ohio State University, Columbus, Ohio 43210, USA
| | - Maki Asano
- Solid Tumor Biology Program, Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Cellular and Biochemistry, Ohio State University, Columbus, Ohio 43210, USA
| | - Gustavo Leone
- Department of Biochemistry and Molecular Biology, Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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19
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Pokholkova GV, Demakov SA, Andreenkov OV, Andreenkova NG, Volkova EI, Belyaeva ES, Zhimulev IF. Tethering of CHROMATOR and dCTCF proteins results in decompaction of condensed bands in the Drosophila melanogaster polytene chromosomes but does not affect their transcription and replication timing. PLoS One 2018; 13:e0192634. [PMID: 29608600 PMCID: PMC5880345 DOI: 10.1371/journal.pone.0192634] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 01/26/2018] [Indexed: 01/20/2023] Open
Abstract
Instulator proteins are central to domain organization and gene regulation in the genome. We used ectopic tethering of CHROMATOR (CHRIZ/CHRO) and dCTCF to pre-defined regions of the genome to dissect the influence of these proteins on local chromatin organization, to analyze their interaction with other key chromatin proteins and to evaluate the effects on transcription and replication. Specifically, using UAS-GAL4DBD system, CHRO and dCTCF were artificially recruited into highly compacted polytene chromosome bands that share the features of silent chromatin type known as intercalary heterochromatin (IH). This led to local chromatin decondensation, formation of novel DHSes and recruitment of several "open chromatin" proteins. CHRO tethering resulted in the recruitment of CP190 and Z4 (PZG), whereas dCTCF tethering attracted CHRO, CP190, and Z4. Importantly, formation of a local stretch of open chromatin did not result in the reactivation of silent marker genes yellow and mini-white immediately adjacent to the targeting region (UAS), nor did RNA polII become recruited into this chromatin. The decompacted region retained late replicated, similarly to the wild-type untargeted region.
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Affiliation(s)
- Galina V. Pokholkova
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences (IMCB RAS), Novosibirsk, Russia
| | - Sergei A. Demakov
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences (IMCB RAS), Novosibirsk, Russia
- Novosibirsk State University (NSU), Novosibirsk, Russia
| | - Oleg V. Andreenkov
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences (IMCB RAS), Novosibirsk, Russia
| | - Natalia G. Andreenkova
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences (IMCB RAS), Novosibirsk, Russia
| | - Elena I. Volkova
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences (IMCB RAS), Novosibirsk, Russia
| | - Elena S. Belyaeva
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences (IMCB RAS), Novosibirsk, Russia
| | - Igor F. Zhimulev
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences (IMCB RAS), Novosibirsk, Russia
- Novosibirsk State University (NSU), Novosibirsk, Russia
- * E-mail:
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20
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Landskron L, Steinmann V, Bonnay F, Burkard TR, Steinmann J, Reichardt I, Harzer H, Laurenson AS, Reichert H, Knoblich JA. The asymmetrically segregating lncRNA cherub is required for transforming stem cells into malignant cells. eLife 2018; 7:31347. [PMID: 29580384 PMCID: PMC5871330 DOI: 10.7554/elife.31347] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 02/06/2018] [Indexed: 12/20/2022] Open
Abstract
Tumor cells display features that are not found in healthy cells. How they become immortal and how their specific features can be exploited to combat tumorigenesis are key questions in tumor biology. Here we describe the long non-coding RNA cherub that is critically required for the development of brain tumors in Drosophila but is dispensable for normal development. In mitotic Drosophila neural stem cells, cherub localizes to the cell periphery and segregates into the differentiating daughter cell. During tumorigenesis, de-differentiation of cherub-high cells leads to the formation of tumorigenic stem cells that accumulate abnormally high cherub levels. We show that cherub establishes a molecular link between the RNA-binding proteins Staufen and Syncrip. As Syncrip is part of the molecular machinery specifying temporal identity in neural stem cells, we propose that tumor cells proliferate indefinitely, because cherub accumulation no longer allows them to complete their temporal neurogenesis program. Many biological signals control how cells grow and divide. However, cancer cells do not obey these growth-restricting signals, and as a result large tumors may develop. Recent experiments have suggested that stem cells – the precursors to the different types of specialized cells found in the body – are particularly important for generating tumors. A stem cell normally divides unequally to form a self-renewing cell and a more specialized cell (often a progenitor cell that will give rise to increasingly specialized cell types). The timing of when the specialization occurs can be key to guiding the ultimately produced cell progenies to their final identity. However, in a tumor cells can retain the ability to self-renew. Ultimately, the resulting ‘tumor stem cells’ become immortal and proliferate indefinitely. It is not fully understood why this uncontrolled proliferation occurs. Just like mammals (including humans), fruit flies can develop tumors. Some of the DNA mutations responsible for tumor development were already identified in flies as early as in the 1970s. This has made fruit flies a well-studied model system for uncovering the principle defects that cause tumors to form. Landskron et al. have now studied the neural stem cells found in brain tumors in fruit flies. Additional DNA mutations were not responsible for these cells becoming immortal. Instead, certain RNA molecules – products that are ‘transcribed’ from the DNA – were present in different amounts in tumor cells. The RNA that showed the greatest increase in tumor cells is a so-called long non-coding RNA named cherub. This RNA molecule has no important role in normal fruit flies, but is critical for tumor formation. Landskron et al. found that during cell division cherub segregates from the neural stem cells to the newly formed progenitor cells, where it breaks down over time. Progenitor cells that contain high levels of cherub give rise to tumor-generating neural stem cells. At the molecular level, cherubhelps two proteins to interact with each other: one called Syncrip that makes the neural stem cells take on a older identity, and another one (Staufen) that tethers it to the cell membrane. By restricting Syncrip to a particular location in the cell, cherub alters the timing of stem cell specialization, which contributes to tumor formation. Overall, the results presented by Landskron et al. reveal a new role for long non-coding RNAs: controlling the localization of the proteins that determine the fate of the cell. They also highlight a critical link between the timing of stem cell development and the proliferation of the cells. Further work is now needed to test whether the same control mechanism works in species other than fruit flies.
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Affiliation(s)
- Lisa Landskron
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Victoria Steinmann
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Francois Bonnay
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Thomas R Burkard
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Jonas Steinmann
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Ilka Reichardt
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Heike Harzer
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | | | | | - Jürgen A Knoblich
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
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21
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Zykova TY, Levitsky VG, Belyaeva ES, Zhimulev IF. Polytene Chromosomes - A Portrait of Functional Organization of the Drosophila Genome. Curr Genomics 2018; 19:179-191. [PMID: 29606905 PMCID: PMC5850506 DOI: 10.2174/1389202918666171016123830] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 04/01/2016] [Accepted: 09/26/2017] [Indexed: 12/15/2022] Open
Abstract
This mini-review is devoted to the problem genetic meaning of main polytene chromosome structures – bands and interbands. Generally, densely packed chromatin forms black bands, moderately condensed regions form grey loose bands, whereas decondensed regions of the genome appear as interbands. Recent progress in the annotation of the Drosophila genome and epigenome has made it possible to compare the banding pattern and the structural organization of genes, as well as their activity. This was greatly aided by our ability to establish the borders of bands and interbands on the physical map, which allowed to perform comprehensive side-by-side comparisons of cytology, genetic and epigenetic maps and to uncover the association between the morphological structures and the functional domains of the genome. These studies largely conclude that interbands 5’-ends of housekeeping genes that are active across all cell types. Interbands are enriched with proteins involved in transcription and nucleosome remodeling, as well as with active histone modifications. Notably, most of the replication origins map to interband regions. As for grey loose bands adjacent to interbands, they typically host the bodies of house-keeping genes. Thus, the bipartite structure composed of an interband and an adjacent grey band functions as a standalone genetic unit. Finally, black bands harbor tissue-specific genes with narrow temporal and tissue expression profiles. Thus, the uniform and permanent activity of interbands combined with the inactivity of genes in bands forms the basis of the universal banding pattern observed in various Drosophila tissues.
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Affiliation(s)
- Tatyana Yu Zykova
- Institute of Molecular and Cellular Biology of the Russian Academy of Sciences, Novosibirsk630090, Russian Federation
| | - Victor G Levitsky
- Institute of Cytology and Genetics of the Russian Academy of Sciences, Novosibirsk630090, Russian Federation.,Novoisibirsk State University, Novosibirsk630090, Russian Federation
| | - Elena S Belyaeva
- Institute of Molecular and Cellular Biology of the Russian Academy of Sciences, Novosibirsk630090, Russian Federation
| | - Igor F Zhimulev
- Institute of Molecular and Cellular Biology of the Russian Academy of Sciences, Novosibirsk630090, Russian Federation.,Novoisibirsk State University, Novosibirsk630090, Russian Federation
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22
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Marelja Z, Leimkühler S, Missirlis F. Iron Sulfur and Molybdenum Cofactor Enzymes Regulate the Drosophila Life Cycle by Controlling Cell Metabolism. Front Physiol 2018; 9:50. [PMID: 29491838 PMCID: PMC5817353 DOI: 10.3389/fphys.2018.00050] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 01/16/2018] [Indexed: 12/20/2022] Open
Abstract
Iron sulfur (Fe-S) clusters and the molybdenum cofactor (Moco) are present at enzyme sites, where the active metal facilitates electron transfer. Such enzyme systems are soluble in the mitochondrial matrix, cytosol and nucleus, or embedded in the inner mitochondrial membrane, but virtually absent from the cell secretory pathway. They are of ancient evolutionary origin supporting respiration, DNA replication, transcription, translation, the biosynthesis of steroids, heme, catabolism of purines, hydroxylation of xenobiotics, and cellular sulfur metabolism. Here, Fe-S cluster and Moco biosynthesis in Drosophila melanogaster is reviewed and the multiple biochemical and physiological functions of known Fe-S and Moco enzymes are described. We show that RNA interference of Mocs3 disrupts Moco biosynthesis and the circadian clock. Fe-S-dependent mitochondrial respiration is discussed in the context of germ line and somatic development, stem cell differentiation and aging. The subcellular compartmentalization of the Fe-S and Moco assembly machinery components and their connections to iron sensing mechanisms and intermediary metabolism are emphasized. A biochemically active Fe-S core complex of heterologously expressed fly Nfs1, Isd11, IscU, and human frataxin is presented. Based on the recent demonstration that copper displaces the Fe-S cluster of yeast and human ferredoxin, an explanation for why high dietary copper leads to cytoplasmic iron deficiency in flies is proposed. Another proposal that exosomes contribute to the transport of xanthine dehydrogenase from peripheral tissues to the eye pigment cells is put forward, where the Vps16a subunit of the HOPS complex may have a specialized role in concentrating this enzyme within pigment granules. Finally, we formulate a hypothesis that (i) mitochondrial superoxide mobilizes iron from the Fe-S clusters in aconitase and succinate dehydrogenase; (ii) increased iron transiently displaces manganese on superoxide dismutase, which may function as a mitochondrial iron sensor since it is inactivated by iron; (iii) with the Krebs cycle thus disrupted, citrate is exported to the cytosol for fatty acid synthesis, while succinyl-CoA and the iron are used for heme biosynthesis; (iv) as iron is used for heme biosynthesis its concentration in the matrix drops allowing for manganese to reactivate superoxide dismutase and Fe-S cluster biosynthesis to reestablish the Krebs cycle.
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Affiliation(s)
- Zvonimir Marelja
- Imagine Institute, Université Paris Descartes-Sorbonne Paris Cité, Paris, France
| | - Silke Leimkühler
- Department of Molecular Enzymology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Fanis Missirlis
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
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23
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Cohen E, Allen SR, Sawyer JK, Fox DT. Fizzy-Related dictates A cell cycle switch during organ repair and tissue growth responses in the Drosophila hindgut. eLife 2018; 7:38327. [PMID: 30117808 PMCID: PMC6130973 DOI: 10.7554/elife.38327] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 08/16/2018] [Indexed: 12/21/2022] Open
Abstract
Ploidy-increasing cell cycles drive tissue growth in many developing organs. Such cycles, including endocycles, are increasingly appreciated to drive tissue growth following injury or activated growth signaling in mature organs. In these organs, the regulation and distinct roles of different cell cycles remains unclear. Here, we uncover a programmed switch between cell cycles in the Drosophila hindgut pylorus. Using an acute injury model, we identify mitosis as the response in larval pyloric cells, whereas endocycles occur in adult pyloric cells. By developing a novel genetic method, DEMISE (Dual-Expression-Method-for-Induced-Site-specific-Eradication), we show the cell cycle regulator Fizzy-related dictates the decision between mitosis and endocycles. After injury, both cycles accurately restore tissue mass and genome content. However, in response to sustained growth signaling, only endocycles preserve epithelial architecture. Our data reveal distinct cell cycle programming in response to similar stimuli in mature vs. developmental states and reveal a tissue-protective role of endocycles.
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Affiliation(s)
- Erez Cohen
- Department of Cell BiologyDuke University School of MedicineDurhamUnited States
| | - Scott R Allen
- Department of Cell BiologyDuke University School of MedicineDurhamUnited States
| | - Jessica K Sawyer
- Department of Pharmacology & Cancer BiologyDuke University School of MedicineDurhamUnited States
| | - Donald T Fox
- Department of Cell BiologyDuke University School of MedicineDurhamUnited States,Department of Pharmacology & Cancer BiologyDuke University School of MedicineDurhamUnited States,Regeneration Next InitiativeDuke University School of MedicineDurhamUnited States
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24
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Guarner A, Morris R, Korenjak M, Boukhali M, Zappia MP, Van Rechem C, Whetstine JR, Ramaswamy S, Zou L, Frolov MV, Haas W, Dyson NJ. E2F/DP Prevents Cell-Cycle Progression in Endocycling Fat Body Cells by Suppressing dATM Expression. Dev Cell 2017; 43:689-703.e5. [PMID: 29233476 PMCID: PMC5901703 DOI: 10.1016/j.devcel.2017.11.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 08/28/2017] [Accepted: 11/07/2017] [Indexed: 10/18/2022]
Abstract
To understand the consequences of the complete elimination of E2F regulation, we profiled the proteome of Drosophila dDP mutants that lack functional E2F/DP complexes. The results uncovered changes in the larval fat body, a differentiated tissue that grows via endocycles. We report an unexpected mechanism of E2F/DP action that promotes quiescence in this tissue. In the fat body, dE2F/dDP limits cell-cycle progression by suppressing DNA damage responses. Loss of dDP upregulates dATM, allowing cells to sense and repair DNA damage and increasing replication of loci that are normally under-replicated in wild-type tissues. Genetic experiments show that ectopic dATM is sufficient to promote DNA synthesis in wild-type fat body cells. Strikingly, reducing dATM levels in dDP-deficient fat bodies restores cell-cycle control, improves tissue morphology, and extends animal development. These results show that, in some cellular contexts, dE2F/dDP-dependent suppression of DNA damage signaling is key for cell-cycle control and needed for normal development.
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Affiliation(s)
- Ana Guarner
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13(th) Street, Charlestown, MA 02129, USA
| | - Robert Morris
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13(th) Street, Charlestown, MA 02129, USA
| | - Michael Korenjak
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13(th) Street, Charlestown, MA 02129, USA
| | - Myriam Boukhali
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13(th) Street, Charlestown, MA 02129, USA
| | - Maria Paula Zappia
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland Avenue, Chicago, IL 60607, USA
| | - Capucine Van Rechem
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13(th) Street, Charlestown, MA 02129, USA
| | - Johnathan R Whetstine
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13(th) Street, Charlestown, MA 02129, USA
| | - Sridhar Ramaswamy
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13(th) Street, Charlestown, MA 02129, USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13(th) Street, Charlestown, MA 02129, USA
| | - Maxim V Frolov
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland Avenue, Chicago, IL 60607, USA
| | - Wilhelm Haas
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13(th) Street, Charlestown, MA 02129, USA
| | - Nicholas J Dyson
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13(th) Street, Charlestown, MA 02129, USA.
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25
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DNA Replication Control During Drosophila Development: Insights into the Onset of S Phase, Replication Initiation, and Fork Progression. Genetics 2017; 207:29-47. [PMID: 28874453 PMCID: PMC5586379 DOI: 10.1534/genetics.115.186627] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 05/19/2017] [Indexed: 12/11/2022] Open
Abstract
Proper control of DNA replication is critical to ensure genomic integrity during cell proliferation. In addition, differential regulation of the DNA replication program during development can change gene copy number to influence cell size and gene expression. Drosophila melanogaster serves as a powerful organism to study the developmental control of DNA replication in various cell cycle contexts in a variety of differentiated cell and tissue types. Additionally, Drosophila has provided several developmentally regulated replication models to dissect the molecular mechanisms that underlie replication-based copy number changes in the genome, which include differential underreplication and gene amplification. Here, we review key findings and our current understanding of the developmental control of DNA replication in the contexts of the archetypal replication program as well as of underreplication and differential gene amplification. We focus on the use of these latter two replication systems to delineate many of the molecular mechanisms that underlie the developmental control of replication initiation and fork elongation.
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Spradling AC. Polytene Chromosome Structure and Somatic Genome Instability. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2017; 82:293-304. [PMID: 29167281 DOI: 10.1101/sqb.2017.82.033670] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Polytene chromosomes have for 80 years provided the highest resolution view of interphase genome structure in an animal cell nucleus. These chromosomes represent the normal genomic state of nearly all Drosophila larval and many adult cells, and a better understanding of their striking banded structure has been sought for decades. A more recently appreciated characteristic of Drosophila polytene cells is somatic genome instability caused by unfinished replication (UR). Repair of stalled forks generates enough deletions in polytene salivary gland cells to alter 10%-90% of the DNA strands within more than 100 UR regions comprising 20% of the euchromatic genome. We accurately map UR regions and show that most approximate large polytene bands, indicating that replication forks frequently stall near band boundaries in late S phase. Chromosome conformation capture has recently identified dense topologically associated domains (TADs) in many genomes and most UR bands are similar or slightly smaller than a cognate Drosophila TAD. We argue that bands serve the evolutionarily ancient function of coordinating genome replication with local gene activity. We also discuss the relatively recent evolution of polyteny and somatic instability in Diptera and propose that these processes helped propel the amazing success of two-winged flies in becoming the most ecologically diverse insect group, with 200 times the number of species as mammals.
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Affiliation(s)
- Allan C Spradling
- Department of Embryology, Howard Hughes Medical Institute, Carnegie Institution for Science, Baltimore, Maryland 21218
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Stormo BM, Fox DT. Polyteny: still a giant player in chromosome research. Chromosome Res 2017; 25:201-214. [PMID: 28779272 PMCID: PMC5768140 DOI: 10.1007/s10577-017-9562-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 07/19/2017] [Accepted: 07/21/2017] [Indexed: 12/17/2022]
Abstract
In this era of high-resolution mapping of chromosome territories, topological interactions, and chromatin states, it is increasingly appreciated that the positioning of chromosomes and their interactions within the nucleus is critical for cellular function. Due to their large size and distinctive structure, polytene chromosomes have contributed a wealth of knowledge regarding chromosome regulation. In this review, we discuss the diversity of polytene chromosomes in nature and in disease, examine the recurring structural features of polytene chromosomes in terms of what they reveal about chromosome biology, and discuss recent advances regarding how polytene chromosomes are assembled and disassembled. After over 130 years of study, these giant chromosomes are still powerful tools to understand chromosome biology.
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Affiliation(s)
- Benjamin M Stormo
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Donald T Fox
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA.
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Rapid DNA Synthesis During Early Drosophila Embryogenesis Is Sensitive to Maternal Humpty Dumpty Protein Function. Genetics 2017; 207:935-947. [PMID: 28942426 DOI: 10.1534/genetics.117.300318] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 09/20/2017] [Indexed: 12/29/2022] Open
Abstract
Problems with DNA replication cause cancer and developmental malformations. It is not fully understood how DNA replication is coordinated with development and perturbed in disease. We had previously identified the Drosophila gene humpty dumpty (hd), and showed that null alleles cause incomplete DNA replication, tissue undergrowth, and lethality. Animals homozygous for the missense allele, hd272-9 , were viable, but adult females had impaired amplification of eggshell protein genes in the ovary, resulting in the maternal effects of thin eggshells and embryonic lethality. Here, we show that expression of an hd transgene in somatic cells of the ovary rescues amplification and eggshell synthesis but not embryo viability. The germline of these mothers remain mutant for the hd272-9 allele, resulting in reduced maternal Hd protein and embryonic arrest during mitosis of the first few S/M nuclear cleavage cycles with chromosome instability and chromosome bridges. Epistasis analysis of hd with the rereplication mutation plutonium indicates that the chromosome bridges of hd embryos are the result of a failed attempt to segregate incompletely replicated sister chromatids. This study reveals that maternally encoded Humpty dumpty protein is essential for DNA replication and genome integrity during the little-understood embryonic S/M cycles. Moreover, the two hd272-9 maternal-effect phenotypes suggest that ovarian gene amplification and embryonic cleavage are two time periods in development that are particularly sensitive to mild deficits in DNA replication function. This last observation has broader relevance for interpreting why mild mutations in the human ortholog of humpty dumpty and other DNA replication genes cause tissue-specific malformations of microcephalic dwarfisms.
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Abstract
Replication forks encounter obstacles that must be repaired or bypassed to complete chromosome duplication before cell division. Proteomic analysis of replication forks suggests that the checkpoint and repair machinery travels with unperturbed forks, implying that they are poised to respond to stalling and collapse. However, impaired fork progression still generates aberrations, including repeat copy number instability and chromosome rearrangements. Deregulated origin firing also causes fork instability if a newer fork collides with an older one, generating double-strand breaks (DSBs) and partially rereplicated DNA. Current evidence suggests that multiple mechanisms are used to repair rereplication damage, yet these can have deleterious consequences for genome integrity.
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Brown SC, Bourge M, Maunoury N, Wong M, Wolfe Bianchi M, Lepers-Andrzejewski S, Besse P, Siljak-Yakovlev S, Dron M, Satiat-Jeunemaître B. DNA Remodeling by Strict Partial Endoreplication in Orchids, an Original Process in the Plant Kingdom. Genome Biol Evol 2017; 9:1051-1071. [PMID: 28419219 PMCID: PMC5546068 DOI: 10.1093/gbe/evx063] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/11/2017] [Indexed: 12/12/2022] Open
Abstract
DNA remodeling during endoreplication appears to be a strong developmental characteristic in orchids. In this study, we analyzed DNA content and nuclei in 41 species of orchids to further map the genome evolution in this plant family. We demonstrate that the DNA remodeling observed in 36 out of 41 orchids studied corresponds to strict partial endoreplication. Such process is developmentally regulated in each wild species studied. Cytometry data analyses allowed us to propose a model where nuclear states 2C, 4E, 8E, etc. form a series comprising a fixed proportion, the euploid genome 2C, plus 2-32 additional copies of a complementary part of the genome. The fixed proportion ranged from 89% of the genome in Vanilla mexicana down to 19% in V. pompona, the lowest value for all 148 orchids reported. Insterspecific hybridization did not suppress this phenomenon. Interestingly, this process was not observed in mass-produced epiphytes. Nucleolar volumes grow with the number of endocopies present, coherent with high transcription activity in endoreplicated nuclei. Our analyses suggest species-specific chromatin rearrangement. Towards understanding endoreplication, V. planifolia constitutes a tractable system for isolating the genomic sequences that confer an advantage via endoreplication from those that apparently suffice at diploid level.
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Affiliation(s)
- Spencer C. Brown
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université
Paris‐Sud, Université Paris‐Saclay, Gif‐sur‐Yvette Cedex, France
| | - Mickaël Bourge
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université
Paris‐Sud, Université Paris‐Saclay, Gif‐sur‐Yvette Cedex, France
| | - Nicolas Maunoury
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université
Paris‐Sud, Université Paris‐Saclay, Gif‐sur‐Yvette Cedex, France
| | - Maurice Wong
- Service du Développement Rural, Papeete Tahiti, French Polynesia,
France
| | - Michele Wolfe Bianchi
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université
Paris‐Sud, Université Paris‐Saclay, Gif‐sur‐Yvette Cedex, France
| | | | - Pascale Besse
- UMR 53, PVBMT Université de la Réunion – Cirad, Pôle de Protection des
Plantes, St Pierre, France
| | - Sonja Siljak-Yakovlev
- Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech,
Université Paris-Saclay, Orsay Cedex, France
| | - Michel Dron
- Institute of Plant Sciences Paris Saclay IPS2, Université Paris-Sud, CNRS,
INRA, Université Evry, Université Paris Diderot, Sorbonne Paris-Cité, Université
Paris-Saclay, Orsay, France
| | - Béatrice Satiat-Jeunemaître
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université
Paris‐Sud, Université Paris‐Saclay, Gif‐sur‐Yvette Cedex, France
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Sekelsky J. DNA Repair in Drosophila: Mutagens, Models, and Missing Genes. Genetics 2017; 205:471-490. [PMID: 28154196 PMCID: PMC5289830 DOI: 10.1534/genetics.116.186759] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 10/18/2016] [Indexed: 12/22/2022] Open
Abstract
The numerous processes that damage DNA are counterbalanced by a complex network of repair pathways that, collectively, can mend diverse types of damage. Insights into these pathways have come from studies in many different organisms, including Drosophila melanogaster Indeed, the first ideas about chromosome and gene repair grew out of Drosophila research on the properties of mutations produced by ionizing radiation and mustard gas. Numerous methods have been developed to take advantage of Drosophila genetic tools to elucidate repair processes in whole animals, organs, tissues, and cells. These studies have led to the discovery of key DNA repair pathways, including synthesis-dependent strand annealing, and DNA polymerase theta-mediated end joining. Drosophila appear to utilize other major repair pathways as well, such as base excision repair, nucleotide excision repair, mismatch repair, and interstrand crosslink repair. In a surprising number of cases, however, DNA repair genes whose products play important roles in these pathways in other organisms are missing from the Drosophila genome, raising interesting questions for continued investigations.
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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
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Ohhara Y, Kobayashi S, Yamanaka N. Nutrient-Dependent Endocycling in Steroidogenic Tissue Dictates Timing of Metamorphosis in Drosophila melanogaster. PLoS Genet 2017; 13:e1006583. [PMID: 28121986 PMCID: PMC5298324 DOI: 10.1371/journal.pgen.1006583] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 02/08/2017] [Accepted: 01/13/2017] [Indexed: 01/09/2023] Open
Abstract
Many animals have an intrinsic growth checkpoint during juvenile development, after which an irreversible decision is made to upregulate steroidogenesis, triggering the metamorphic juvenile-to-adult transition. However, a molecular process underlying such a critical developmental decision remains obscure. Here we show that nutrient-dependent endocycling in steroidogenic cells provides the machinery necessary for irreversible activation of metamorphosis in Drosophila melanogaster. Endocycle progression in cells of the prothoracic gland (PG) is tightly coupled with the growth checkpoint, and block of endocycle in PG cells causes larval developmental arrest due to reduction in biosynthesis of the steroid hormone ecdysone. Moreover, inhibition of the nutrient sensor target of rapamycin (TOR) in the PG during the checkpoint period causes endocycle inhibition and developmental arrest, which can be rescued by inducing additional rounds of endocycles by Cyclin E. We propose that a TOR-mediated cell cycle checkpoint in steroidogenic tissue provides a systemic growth checkpoint for reproductive maturation. Onset of sexual maturation constitutes a point of no return in animals; once this life-changing decision is made, upregulation of steroidogenesis leads to irreversible juvenile-to-adult transition in humans and insects alike. While nutrient signals contributing to this decision-making process have been well studied, molecular events that ultimately determine its precise timing remain a mystery. We report here that nutrient-dependent endoreplication, the replication of genomic DNA without cell division, in steroidogenic cells functions as an intrinsic timer, whereby degree of polyploidy sets the timing of reproductive maturation (i.e. metamorphosis) in fruit flies. The cumulative and irreversible nature of endoreplication thus provides an intrinsic molecular machinery underlying the irreversible decision-making process, which may be widely leveraged as a fundamental developmental timing mechanism.
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Affiliation(s)
- Yuya Ohhara
- Department of Entomology, Institute for Integrative Genome Biology, Center for Disease Vector Research, University of California, Riverside, Riverside, California, United States of America
| | - Satoru Kobayashi
- Life Science Center of Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Naoki Yamanaka
- Department of Entomology, Institute for Integrative Genome Biology, Center for Disease Vector Research, University of California, Riverside, Riverside, California, United States of America
- * E-mail:
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Hřibová E, Holušová K, Trávníček P, Petrovská B, Ponert J, Šimková H, Kubátová B, Jersáková J, Čurn V, Suda J, Doležel J, Vrána J. The Enigma of Progressively Partial Endoreplication: New Insights Provided by Flow Cytometry and Next-Generation Sequencing. Genome Biol Evol 2016; 8:1996-2005. [PMID: 27324917 PMCID: PMC4943206 DOI: 10.1093/gbe/evw141] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In many plant species, somatic cell differentiation is accompanied by endoreduplication, a process during which cells undergo one or more rounds of DNA replication cycles in the absence of mitosis, resulting in nuclei with multiples of 2C DNA amounts (4C, 8C, 16C, etc.). In some orchids, a disproportionate increase in nuclear DNA contents has been observed, where successive endoreduplication cycles result in DNA amounts 2C + P, 2C + 3P, 2C + 7P, etc., where P is the DNA content of the replicated part of the 2C nuclear genome. This unique phenomenon was termed "progressively partial endoreplication" (PPE). We investigated processes behind the PPE in Ludisia discolor using flow cytometry (FCM) and Illumina sequencing. In particular, we wanted to determine whether chromatin elimination or incomplete genome duplication was involved, and to identify types of DNA sequences that were affected. Cell cycle analysis of root tip cell nuclei pulse-labeled with EdU revealed two cell cycles, one ending above the population of nuclei with 2C + P content, and the other with a typical "horseshoe" pattern of S-phase nuclei ranging from 2C to 4C DNA contents. The process leading to nuclei with 2C + P amounts therefore involves incomplete genome replication. Subsequent Illumina sequencing of flow-sorted 2C and 2C + P nuclei showed that all types of repetitive DNA sequences were affected during PPE; a complete elimination of any specific type of repetitive DNA was not observed. We hypothesize that PPE is part of a highly controlled transition mechanism from proliferation phase to differentiation phase of plant tissue development.
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Affiliation(s)
- Eva Hřibová
- Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, Olomouc, Czech Republic
| | - Kateřina Holušová
- Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, Olomouc, Czech Republic
| | - Pavel Trávníček
- Institute of Botany, the Czech Academy of Sciences, Průhonice, Czech Republic Department of Botany, Faculty of Science, Charles University in Prague, Czech Republic Biotechnological Centre, Faculty of Agriculture, University of South Bohemia in České Budějovice, Czech Republic
| | - Beáta Petrovská
- Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, Olomouc, Czech Republic
| | - Jan Ponert
- Department of Experimental Plant Biology, Faculty of Science, Charles University in Prague, Czech Republic Prague Botanical Garden, Prague, Czech Republic
| | - Hana Šimková
- Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, Olomouc, Czech Republic
| | - Barbora Kubátová
- Biotechnological Centre, Faculty of Agriculture, University of South Bohemia in České Budějovice, Czech Republic
| | - Jana Jersáková
- Department of Ecosystem Biology, Faculty of Science, University of South Bohemia in České Budějovice, Czech Republic
| | - Vladislav Čurn
- Biotechnological Centre, Faculty of Agriculture, University of South Bohemia in České Budějovice, Czech Republic
| | - Jan Suda
- Institute of Botany, the Czech Academy of Sciences, Průhonice, Czech Republic Department of Botany, Faculty of Science, Charles University in Prague, Czech Republic
| | - Jaroslav Doležel
- Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, Olomouc, Czech Republic
| | - Jan Vrána
- Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, Olomouc, Czech Republic
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Khoroshko VA, Levitsky VG, Zykova TY, Antonenko OV, Belyaeva ES, Zhimulev IF. Chromatin Heterogeneity and Distribution of Regulatory Elements in the Late-Replicating Intercalary Heterochromatin Domains of Drosophila melanogaster Chromosomes. PLoS One 2016; 11:e0157147. [PMID: 27300486 PMCID: PMC4907538 DOI: 10.1371/journal.pone.0157147] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 05/25/2016] [Indexed: 12/28/2022] Open
Abstract
Late-replicating domains (intercalary heterochromatin) in the Drosophila genome display a number of features suggesting their organization is quite unique. Typically, they are quite large and encompass clusters of functionally unrelated tissue-specific genes. They correspond to the topologically associating domains and conserved microsynteny blocks. Our study aims at exploring further details of molecular organization of intercalary heterochromatin and has uncovered surprising heterogeneity of chromatin composition in these regions. Using the 4HMM model developed in our group earlier, intercalary heterochromatin regions were found to host chromatin fragments with a particular epigenetic profile. Aquamarine chromatin fragments (spanning 0.67% of late-replicating regions) are characterized as a class of sequences that appear heterogeneous in terms of their decompactization. These fragments are enriched with enhancer sequences and binding sites for insulator proteins. They likely mark the chromatin state that is related to the binding of cis-regulatory proteins. Malachite chromatin fragments (11% of late-replicating regions) appear to function as universal transitional regions between two contrasting chromatin states. Namely, they invariably delimit intercalary heterochromatin regions from the adjacent active chromatin of interbands. Malachite fragments also flank aquamarine fragments embedded in the repressed chromatin of late-replicating regions. Significant enrichment of insulator proteins CP190, SU(HW), and MOD2.2 was observed in malachite chromatin. Neither aquamarine nor malachite chromatin types appear to correlate with the positions of highly conserved non-coding elements (HCNE) that are typically replete in intercalary heterochromatin. Malachite chromatin found on the flanks of intercalary heterochromatin regions tends to replicate earlier than the malachite chromatin embedded in intercalary heterochromatin. In other words, there exists a gradient of replication progressing from the flanks of intercalary heterochromatin regions center-wise. The peculiar organization and features of replication in large late-replicating regions are discussed as possible factors shaping the evolutionary stability of intercalary heterochromatin.
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Affiliation(s)
| | - Viktor G. Levitsky
- Novosibirsk State University, Novosibirsk, Russia
- Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia
| | - Tatyana Yu. Zykova
- Institute of Molecular and Cellular Biology, SB RAS, Novosibirsk, Russia
| | | | - Elena S. Belyaeva
- Institute of Molecular and Cellular Biology, SB RAS, Novosibirsk, Russia
| | - Igor F. Zhimulev
- Institute of Molecular and Cellular Biology, SB RAS, Novosibirsk, Russia
- Novosibirsk State University, Novosibirsk, Russia
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35
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Bretscher HS, Fox DT. Proliferation of Double-Strand Break-Resistant Polyploid Cells Requires Drosophila FANCD2. Dev Cell 2016; 37:444-57. [PMID: 27270041 PMCID: PMC4901310 DOI: 10.1016/j.devcel.2016.05.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 02/22/2016] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Conserved DNA-damage responses (DDRs) sense genome damage and prevent mitosis of broken chromosomes. How cells lacking DDRs cope with broken chromosomes during mitosis is poorly understood. DDRs are frequently inactivated in cells with extra genomes (polyploidy), suggesting that study of polyploidy can reveal how cells with impaired DDRs/genome damage continue dividing. Here, we show that continued division and normal organ development occurs in polyploid, DDR-impaired Drosophila papillar cells. As papillar cells become polyploid, they naturally accumulate broken acentric chromosomes but do not apoptose/arrest the cell cycle. To survive mitosis with acentric chromosomes, papillar cells require Fanconi anemia proteins FANCD2 and FANCI, as well as Blm helicase, but not canonical DDR signaling. FANCD2 acts independently of previous S phases to promote alignment and segregation of acentric DNA produced by double-strand breaks, thus avoiding micronuclei and organ malformation. Because polyploidy and impaired DDRs can promote cancer, our findings provide insight into disease-relevant DNA-damage tolerance mechanisms.
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Affiliation(s)
- Heidi S Bretscher
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, DUMC Box 3813, Durham, NC 27710, USA
| | - Donald T Fox
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, DUMC Box 3813, Durham, NC 27710, USA.
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Stormo BM, Fox DT. Distinct responses to reduplicated chromosomes require distinct Mad2 responses. eLife 2016; 5. [PMID: 27159240 PMCID: PMC4898934 DOI: 10.7554/elife.15204] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 05/08/2016] [Indexed: 01/17/2023] Open
Abstract
Duplicating chromosomes once each cell cycle produces sister chromatid pairs, which separate accurately at anaphase. In contrast, reduplicating chromosomes without separation frequently produces polytene chromosomes, a barrier to accurate mitosis. Chromosome reduplication occurs in many contexts, including: polytene tissue development, polytene tumors, and following treatment with mitosis-blocking chemotherapeutics. However, mechanisms responding to or resolving polyteny during mitosis are poorly understood. Here, using Drosophila, we uncover two distinct reduplicated chromosome responses. First, when reduplicated polytene chromosomes persist into metaphase, an anaphase delay prevents tissue malformation and apoptosis. Second, reduplicated polytene chromosomes can also separate prior to metaphase through a spindle-independent mechanism termed Separation-Into-Recent-Sisters (SIRS). Both reduplication responses require the spindle assembly checkpoint protein Mad2. While Mad2 delays anaphase separation of metaphase polytene chromosomes, Mad2’s control of overall mitotic timing ensures efficient SIRS. Our results pinpoint mechanisms enabling continued proliferation after genome reduplication, a finding with implications for cancer progression and prevention. DOI:http://dx.doi.org/10.7554/eLife.15204.001 Before a cell divides, it duplicates all its genetic information, which is stored on chromosomes. Then, each chromosome evenly divides into two new cells so that each cell ends up with identical copies of the genetic information. Because the cellular machinery that evenly divides chromosomes is built to recognize chromosomes that were duplicated exactly once, it is important to maintain this pattern of alternating one round of duplication with one round of division. Cells that instead duplicate their chromosomes more than once can make mistakes during division that are associated with diseases such as cancer. Chromosomes with extra duplications are present in normal tissues such as the placenta of mammals. They can also occur in human diseases and may even result from chemotherapy treatment. However, we know almost nothing about how cells respond to these problematic chromosomes when dividing. By studying cells from the Drosophila melanogaster species of fruit fly, Stormo and Fox discovered two distinct ways in which cells respond to extra chromosome duplications. One response occurs in cells that were experimentally engineered to undergo an extra chromosome duplication. These cells delay division so that the chromosome separation machinery can somehow adapt to the challenge of separating more than two chromosome copies at once. The second response occurs in cells that naturally undergo extra chromosome duplications before division. In these cells, Stormo and Fox discovered a new type of chromosome separation, whereby the extra chromosome copies move apart from each other before cell division. In doing so the chromosomes can better interact with the chromosome separation machinery during division. Stormo and Fox also found that a protein named Mad2 is important in both responses, and gives the cell enough time to respond to extra chromosome copies. Without Mad2, the separation of chromosomes with extra duplications is too hasty, and can lead to severe cell division errors and cause organs to form incorrectly. Having uncovered two new responses that cells use to adapt to extra chromosomes, it will now be important to find other proteins like Mad2 that are important in these events. Understanding these processes and the proteins involved in more detail could help to prevent diseases that are associated with extra chromosomes. DOI:http://dx.doi.org/10.7554/eLife.15204.002
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Affiliation(s)
- Benjamin M Stormo
- Department of Cell Biology, Duke University Medical Center, Durham, United States
| | - Donald T Fox
- Department of Cell Biology, Duke University Medical Center, Durham, United States.,Department of Pharamacology and Cancer biology, Duke University Medical Center, Durham, United States
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37
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Qi S, Calvi BR. Different cell cycle modifications repress apoptosis at different steps independent of developmental signaling in Drosophila. Mol Biol Cell 2016; 27:1885-97. [PMID: 27075174 PMCID: PMC4907722 DOI: 10.1091/mbc.e16-03-0139] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 04/08/2016] [Indexed: 11/11/2022] Open
Abstract
Genetic manipulations of the cell cycle repress apoptosis independent of developmental signaling. The findings have broader relevance to understanding the coordination of cell proliferation and apoptosis in development and disease. Apoptotic cell death is important for the normal development of a variety of organisms. Apoptosis is also a response to DNA damage and an important barrier to oncogenesis. The apoptotic response to DNA damage is dampened in specific cell types during development. Developmental signaling pathways can repress apoptosis, and reduced cell proliferation also correlates with a lower apoptotic response. However, because developmental signaling regulates both cell proliferation and apoptosis, the relative contribution of cell division to the apoptotic response has been hard to discern in vivo. Here we use Drosophila oogenesis as an in vivo model system to determine the extent to which cell proliferation influences the apoptotic response to DNA damage. We find that different types of cell cycle modifications are sufficient to repress the apoptotic response to ionizing radiation independent of developmental signaling. The step(s) at which the apoptosis pathway was repressed depended on the type of cell cycle modification—either upstream or downstream of expression of the p53-regulated proapoptotic genes. Our findings have important implications for understanding the coordination of cell proliferation with the apoptotic response in development and disease, including cancer and the tissue-specific responses to radiation therapy.
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Affiliation(s)
- Suozhi Qi
- Department of Biology, Indiana University, Bloomington, IN 47405
| | - Brian R Calvi
- Department of Biology, Indiana University, Bloomington, IN 47405
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38
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Hoffmann RF, Moshkin YM, Mouton S, Grzeschik NA, Kalicharan RD, Kuipers J, Wolters AHG, Nishida K, Romashchenko AV, Postberg J, Lipps H, Berezikov E, Sibon OCM, Giepmans BNG, Lansdorp PM. Guanine quadruplex structures localize to heterochromatin. Nucleic Acids Res 2015; 44:152-63. [PMID: 26384414 PMCID: PMC4705689 DOI: 10.1093/nar/gkv900] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 08/21/2015] [Indexed: 12/27/2022] Open
Abstract
Increasing amounts of data support a role for guanine quadruplex (G4) DNA and RNA structures in various cellular processes. We stained different organisms with monoclonal antibody 1H6 specific for G4 DNA. Strikingly, immuno-electron microscopy showed exquisite specificity for heterochromatin. Polytene chromosomes from Drosophila salivary glands showed bands that co-localized with heterochromatin proteins HP1 and the SNF2 domain-containing protein SUUR. Staining was retained in SUUR knock-out mutants but lost upon overexpression of SUUR. Somatic cells in Macrostomum lignano were strongly labeled, but pluripotent stem cells labeled weakly. Similarly, germline stem cells in Drosophila ovaries were weakly labeled compared to most other cells. The unexpected presence of G4 structures in heterochromatin and the difference in G4 staining between somatic cells and stem cells with germline DNA in ciliates, flatworms, flies and mammals point to a conserved role for G4 structures in nuclear organization and cellular differentiation.
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Affiliation(s)
- Roland F Hoffmann
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Centre Groningen, A. Deusinglaan 1, NL-9713 AV Groningen, The Netherlands
| | - Yuri M Moshkin
- Department of Biochemistry, Erasmus University Medical Center, Dr. Molewaterplein 50, NL-3015 GE Rotterdam, The Netherlands
| | - Stijn Mouton
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Centre Groningen, A. Deusinglaan 1, NL-9713 AV Groningen, The Netherlands
| | - Nicola A Grzeschik
- Department of Cell Biology, University of Groningen, University Medical Centre Groningen, A. Deusinglaan 1, NL-9713 AV Groningen, The Netherlands
| | - Ruby D Kalicharan
- Department of Cell Biology, University of Groningen, University Medical Centre Groningen, A. Deusinglaan 1, NL-9713 AV Groningen, The Netherlands
| | - Jeroen Kuipers
- Department of Cell Biology, University of Groningen, University Medical Centre Groningen, A. Deusinglaan 1, NL-9713 AV Groningen, The Netherlands
| | - Anouk H G Wolters
- Department of Cell Biology, University of Groningen, University Medical Centre Groningen, A. Deusinglaan 1, NL-9713 AV Groningen, The Netherlands
| | - Kazuki Nishida
- Faculty of Medicine, Kyoto University, Kyoto 606-8501, Japan
| | - Aleksander V Romashchenko
- Department of Biochemistry, Erasmus University Medical Center, Dr. Molewaterplein 50, NL-3015 GE Rotterdam, The Netherlands Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Jan Postberg
- Helios Medical Centre Wuppertal, Paediatrics Centre, Witten/Herdecke University, Wuppertal, Germany
| | - Hans Lipps
- Institute of Cell Biology, Centre for Biomedical Education and Research, Witten/Herdecke University, Witten, Germany
| | - Eugene Berezikov
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Centre Groningen, A. Deusinglaan 1, NL-9713 AV Groningen, The Netherlands Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Ody C M Sibon
- Department of Cell Biology, University of Groningen, University Medical Centre Groningen, A. Deusinglaan 1, NL-9713 AV Groningen, The Netherlands
| | - Ben N G Giepmans
- Department of Cell Biology, University of Groningen, University Medical Centre Groningen, A. Deusinglaan 1, NL-9713 AV Groningen, The Netherlands
| | - Peter M Lansdorp
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Centre Groningen, A. Deusinglaan 1, NL-9713 AV Groningen, The Netherlands Terry Fox Laboratory, British Columbia Cancer Agency and Department of Medicine, University of British Columbia Vancouver, BC, V5Z 1L3, Canada
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Abstract
Polyploid cells, which contain more than two genome copies, occur throughout nature. Beyond well-established roles in increasing cell size/metabolic output, polyploidy can also promote nonuniform genome, transcriptome, and metabolome alterations. Polyploidy also frequently confers resistance to environmental stresses not tolerated by diploid cells. Recent progress has begun to unravel how this fascinating phenomenon contributes to normal physiology and disease.
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Affiliation(s)
- Kevin P Schoenfelder
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710
| | - Donald T Fox
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710
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Nordman JT, Orr-Weaver TL. Understanding replication fork progression, stability, and chromosome fragility by exploiting the Suppressor of Underreplication protein. Bioessays 2015; 37:856-61. [PMID: 26059810 DOI: 10.1002/bies.201500021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
There are many layers of regulation governing DNA replication to ensure that genetic information is accurately transmitted from mother cell to daughter cell. While much of the control occurs at the level of origin selection and firing, less is known about how replication fork progression is controlled throughout the genome. In Drosophila polytene cells, specific regions of the genome become repressed for DNA replication, resulting in underreplication and decreased copy number. Importantly, underreplicated domains share properties with common fragile sites. The Suppressor of Underreplication protein SUUR is essential for this repression. Recent work established that SUUR functions by directly inhibiting replication fork progression, raising several interesting questions as to how replication fork progression and stability can be modulated within targeted regions of the genome. Here we discuss potential mechanisms by which replication fork inhibition can be achieved and the consequences this has on genome stability and copy number control.
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Affiliation(s)
- Jared T Nordman
- Department of Biology, Whitehead Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Terry L Orr-Weaver
- Department of Biology, Whitehead Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
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41
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Alexander JL, Barrasa MI, Orr-Weaver TL. Replication fork progression during re-replication requires the DNA damage checkpoint and double-strand break repair. Curr Biol 2015; 25:1654-60. [PMID: 26051888 DOI: 10.1016/j.cub.2015.04.058] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/02/2015] [Accepted: 04/24/2015] [Indexed: 11/19/2022]
Abstract
Replication origins are under tight regulation to ensure activation occurs only once per cell cycle [1, 2]. Origin re-firing in a single S phase leads to the generation of DNA double-strand breaks (DSBs) and activation of the DNA damage checkpoint [2-7]. If the checkpoint is blocked, cells enter mitosis with partially re-replicated DNA that generates chromosome breaks and fusions [5]. These types of chromosomal aberrations are common in numerous human cancers, suggesting that re-replication events contribute to cancer progression. It was proposed that fork instability and DSBs formed during re-replication are the result of head-to-tail collisions and collapse of adjacent replication forks [3]. However, previously studied systems lack the resolution to determine whether the observed DSBs are generated at sites of fork collisions. Here, we utilize the Drosophila ovarian follicle cells, which exhibit re-replication under precise developmental control [8-10], to model the consequences of re-replication at actively elongating forks. Re-replication occurs from specific replication origins at six genomic loci, termed Drosophila amplicons in follicle cells (DAFCs) [10-12]. Precise developmental timing of DAFC origin firing permits identification of forks at defined points after origin initiation [13, 14]. Here, we show that DAFC re-replication causes fork instability and generates DSBs at sites of potential fork collisions. Immunofluorescence and ChIP-seq demonstrate the DSB marker γH2Av is enriched at elongating forks. Fork progression is reduced in the absence of DNA damage checkpoint components and nonhomologous end-joining (NHEJ), but not homologous recombination. NHEJ appears to continually repair forks during re-replication to maintain elongation.
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Affiliation(s)
- Jessica L Alexander
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 68-132, Cambridge, MA 02139, USA
| | - M Inmaculada Barrasa
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
| | - Terry L Orr-Weaver
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 68-132, Cambridge, MA 02139, USA.
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42
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Nordman JT, Kozhevnikova EN, Verrijzer CP, Pindyurin AV, Andreyeva EN, Shloma VV, Zhimulev IF, Orr-Weaver TL. DNA copy-number control through inhibition of replication fork progression. Cell Rep 2014; 9:841-9. [PMID: 25437540 DOI: 10.1016/j.celrep.2014.10.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 08/29/2014] [Accepted: 09/30/2014] [Indexed: 01/15/2023] Open
Abstract
Proper control of DNA replication is essential to ensure faithful transmission of genetic material and prevent chromosomal aberrations that can drive cancer progression and developmental disorders. DNA replication is regulated primarily at the level of initiation and is under strict cell-cycle regulation. Importantly, DNA replication is highly influenced by developmental cues. In Drosophila, specific regions of the genome are repressed for DNA replication during differentiation by the SNF2 domain-containing protein SUUR through an unknown mechanism. We demonstrate that SUUR is recruited to active replication forks and mediates the repression of DNA replication by directly inhibiting replication fork progression instead of functioning as a replication fork barrier. Mass spectrometry identification of SUUR-associated proteins identified the replicative helicase member CDC45 as a SUUR-associated protein, supporting a role for SUUR directly at replication forks. Our results reveal that control of eukaryotic DNA copy number can occur through the inhibition of replication fork progression.
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Affiliation(s)
- Jared T Nordman
- Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Elena N Kozhevnikova
- Erasmus University Medical Centre, P.O. Box 1738, 3000 DR Rotterdam, the Netherlands; Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 10, Novosibirsk 630090, Russia
| | - C Peter Verrijzer
- Erasmus University Medical Centre, P.O. Box 1738, 3000 DR Rotterdam, the Netherlands
| | - Alexey V Pindyurin
- Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands; Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova St. 2, Novosibirsk 630090, Russia
| | - Evgeniya N Andreyeva
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia
| | - Victor V Shloma
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia
| | - Igor F Zhimulev
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova St. 2, Novosibirsk 630090, Russia
| | - Terry L Orr-Weaver
- Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
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43
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Guo W, Wu Z, Song J, Jiang F, Wang Z, Deng S, Walker VK, Zhou S. Juvenile hormone-receptor complex acts on mcm4 and mcm7 to promote polyploidy and vitellogenesis in the migratory locust. PLoS Genet 2014; 10:e1004702. [PMID: 25340846 PMCID: PMC4207617 DOI: 10.1371/journal.pgen.1004702] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 08/23/2014] [Indexed: 11/18/2022] Open
Abstract
Juvenile hormone (JH), a sesquiterpenoid produced by the corpora allata, coordinates insect growth, metamorphosis, and reproduction. While JH action for the repression of larval metamorphosis has been well studied, the molecular basis of JH in promoting adult reproduction has not been fully elucidated. Methoprene-tolerant (Met), the JH receptor, has been recently shown to mediate JH action during metamorphosis as well as in vitellogenesis, but again, the precise mechanism underlying the latter has been lacking. We have now demonstrated using Met RNAi to phenocopy a JH-deprived condition in migratory locusts, that JH stimulates DNA replication and increases ploidy in preparation for vitellogenesis. Mcm4 and Mcm7, two genes in the DNA replication pathway were expressed in the presence of JH and Met. Depletion of Mcm4 or Mcm7 inhibited de novo DNA synthesis and polyploidization, and resulted in the substantial reduction of vitellogenin mRNA levels as well as severely impaired oocyte maturation and ovarian growth. By using luciferase reporter and electrophoretic mobility shift assays, we have shown that Met directly regulates the transcription of Mcm4 and Mcm7 by binding to upstream consensus sequences with E-box or E-box-like motifs. Our work suggests that the JH-receptor complex acts on Mcm4 and Mcm7 to regulate DNA replication and polyploidy for vitellogenesis and oocyte maturation.
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Affiliation(s)
- Wei Guo
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Zhongxia Wu
- School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Jiasheng Song
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Feng Jiang
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Zhiming Wang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Shun Deng
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | | | - Shutang Zhou
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- * E-mail:
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44
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Yarosh W, Spradling AC. Incomplete replication generates somatic DNA alterations within Drosophila polytene salivary gland cells. Genes Dev 2014; 28:1840-55. [PMID: 25128500 PMCID: PMC4197960 DOI: 10.1101/gad.245811.114] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
DNA replication remains unfinished in many Drosophila polyploid cells, which harbor disproportionately fewer copies of late-replicating chromosomal regions. Using NextGen sequencing of DNA from giant polytene cells of the larval salivary gland, Yarosh and Spradling show that sporadic, incomplete replication during the endocycle S phase alters the Drosophila genome at thousands of sites that differ in every cell; similar events occur in the ovary. The authors propose that the extensive somatic DNA instability described here underlies position effect variegation and molds the structure of polytene chromosomes. DNA replication remains unfinished in many Drosophila polyploid cells, which harbor disproportionately fewer copies of late-replicating chromosomal regions. By analyzing paired-end high-throughput sequence data from polytene larval salivary gland cells, we define 112 underreplicated (UR) euchromatic regions 60–480 kb in size. To determine the effects of underreplication on genome integrity, we analyzed anomalous read pairs and breakpoint reads throughout the euchromatic genome. Each UR euchromatic region contains many different deletions 10–500 kb in size, while very few deletions are present in fully replicated chromosome regions or UR zones from embryo DNA. Thus, during endocycles, stalled forks within UR regions break and undergo local repair instead of remaining stable and generating nested forks. As a result, each salivary gland cell contains hundreds of unique deletions that account for their copy number reductions. Similar UR regions and deletions were observed in ovarian DNA, suggesting that incomplete replication, fork breakage, and repair occur widely in polytene cells. UR regions are enriched in genes encoding immunoglobulin superfamily proteins and contain many neurally expressed and homeotic genes. We suggest that the extensive somatic DNA instability described here underlies position effect variegation, molds the structure of polytene chromosomes, and should be investigated for possible functions.
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Affiliation(s)
- Will Yarosh
- Howard Hughes Medical Institute, Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
| | - Allan C Spradling
- Howard Hughes Medical Institute, Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
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45
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Zhang B, Mehrotra S, Ng WL, Calvi BR. Low levels of p53 protein and chromatin silencing of p53 target genes repress apoptosis in Drosophila endocycling cells. PLoS Genet 2014; 10:e1004581. [PMID: 25211335 PMCID: PMC4161308 DOI: 10.1371/journal.pgen.1004581] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 07/03/2014] [Indexed: 12/23/2022] Open
Abstract
Apoptotic cell death is an important response to genotoxic stress that prevents oncogenesis. It is known that tissues can differ in their apoptotic response, but molecular mechanisms are little understood. Here, we show that Drosophila polyploid endocycling cells (G/S cycle) repress the apoptotic response to DNA damage through at least two mechanisms. First, the expression of all the Drosophila p53 protein isoforms is strongly repressed at a post-transcriptional step. Second, p53-regulated pro-apoptotic genes are epigenetically silenced in endocycling cells, preventing activation of a paused RNA Pol II by p53-dependent or p53-independent pathways. Over-expression of the p53A isoform did not activate this paused RNA Pol II complex in endocycling cells, but over-expression of the p53B isoform with a longer transactivation domain did, suggesting that dampened p53B protein levels are crucial for apoptotic repression. We also find that the p53A protein isoform is ubiquitinated and degraded by the proteasome in endocycling cells. In mitotic cycling cells, p53A was the only isoform expressed to detectable levels, and its mRNA and protein levels increased after irradiation, but there was no evidence for an increase in protein stability. However, our data suggest that p53A protein stability is regulated in unirradiated cells, which likely ensures that apoptosis does not occur in the absence of stress. Without irradiation, both p53A protein and a paused RNA pol II were pre-bound to the promoters of pro-apoptotic genes, preparing mitotic cycling cells for a rapid apoptotic response to genotoxic stress. Together, our results define molecular mechanisms by which different cells in development modulate their apoptotic response, with broader significance for the survival of normal and cancer polyploid cells in mammals. In order to maintain genome integrity, eukaryotic cells have evolved multiple ways to respond to DNA damage stress. One of the major cellular responses is apoptosis, during which the cell undergoes programmed cell death in order to prevent the propagation of the damaged genome to daughter cells. Although clinical observations and other studies have shown that tissues can differ in their apoptotic response, the molecular mechanisms underlying these differences are largely unknown. We have shown in our model system, Drosophila, that endocycling cells do not initiate cell death in response to DNA damage. The endocycle is a cell cycle variation that is widely found in nature and conserved from plant to animals. During the endocycle, cells duplicate their genomic DNA but do not enter mitosis to segregate chromosomes, resulting in a polyploid genome content. In this study, we investigate how the apoptotic response to DNA damage is repressed in endocycling cells. We find that the Drosophila ortholog of the human p53 tumor suppressor protein is expressed at very low levels in endocycling cells. Moreover, the downstream pro-apoptotic genes that are regulated by p53 are epigenetically silenced in endocycling cells. Our results provide important insights into tissue-specific apoptotic responses in development, with possible broader impact on understanding radiation therapy response and cancer of different tissues.
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Affiliation(s)
- Bingqing Zhang
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
| | - Sonam Mehrotra
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
| | - Wei Lun Ng
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
| | - Brian R. Calvi
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
- * E-mail:
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46
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Besnard E, Desprat R, Ryan M, Kahli M, Aladjem MI, Lemaitre JM. Best practices for mapping replication origins in eukaryotic chromosomes. ACTA ACUST UNITED AC 2014; 64:22.18.1-13. [PMID: 25181303 DOI: 10.1002/0471143030.cb2218s64] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Understanding the regulatory principles ensuring complete DNA replication in each cell division is critical for deciphering the mechanisms that maintain genomic stability. Recent advances in genome sequencing technology facilitated complete mapping of DNA replication sites and helped move the field from observing replication patterns at a handful of single loci to analyzing replication patterns genome-wide. These advances address issues, such as the relationship between replication initiation events, transcription, and chromatin modifications, and identify potential replication origin consensus sequences. This unit summarizes the technological and fundamental aspects of replication profiling and briefly discusses novel insights emerging from mining large datasets, published in the last 3 years, and also describes DNA replication dynamics on a whole-genome scale.
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Affiliation(s)
- Emilie Besnard
- Laboratory of Genome Plasticity and Aging, Institute of Functional Genomics, CNRS UMR5203, INSERM U661, UMI, Montpellier, France
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47
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Abstract
ENCODE projects exist for many eukaryotes, including humans, but as of yet no defined project exists for plants. A plant ENCODE would be invaluable to the research community and could be more readily produced than its metazoan equivalents by capitalizing on the preexisting infrastructure provided from similar projects. Collecting and normalizing plant epigenomic data for a range of species will facilitate hypothesis generation, cross-species comparisons, annotation of genomes, and an understanding of epigenomic functions throughout plant evolution. Here, we discuss the need for such a project, outline the challenges it faces, and suggest ways forward to build a plant ENCODE.
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Affiliation(s)
- Amanda K Lane
- Department of Genetics, University of Georgia, Athens, Georgia 30602;
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48
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Zhimulev IF, Zykova TY, Goncharov FP, Khoroshko VA, Demakova OV, Semeshin VF, Pokholkova GV, Boldyreva LV, Demidova DS, Babenko VN, Demakov SA, Belyaeva ES. Genetic organization of interphase chromosome bands and interbands in Drosophila melanogaster. PLoS One 2014; 9:e101631. [PMID: 25072930 PMCID: PMC4114487 DOI: 10.1371/journal.pone.0101631] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 06/09/2014] [Indexed: 12/18/2022] Open
Abstract
Drosophila melanogaster polytene chromosomes display specific banding pattern; the underlying genetic organization of this pattern has remained elusive for many years. In the present paper, we analyze 32 cytology-mapped polytene chromosome interbands. We estimated molecular locations of these interbands, described their molecular and genetic organization and demonstrate that polytene chromosome interbands contain the 5' ends of housekeeping genes. As a rule, interbands display preferential "head-to-head" orientation of genes. They are enriched for "broad" class promoters characteristic of housekeeping genes and associate with open chromatin proteins and Origin Recognition Complex (ORC) components. In two regions, 10A and 100B, coding sequences of genes whose 5'-ends reside in interbands map to constantly loosely compacted, early-replicating, so-called "grey" bands. Comparison of expression patterns of genes mapping to late-replicating dense bands vs genes whose promoter regions map to interbands shows that the former are generally tissue-specific, whereas the latter are represented by ubiquitously active genes. Analysis of RNA-seq data (modENCODE-FlyBase) indicates that transcripts from interband-mapping genes are present in most tissues and cell lines studied, across most developmental stages and upon various treatment conditions. We developed a special algorithm to computationally process protein localization data generated by the modENCODE project and show that Drosophila genome has about 5700 sites that demonstrate all the features shared by the interbands cytologically mapped to date.
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Affiliation(s)
- Igor F. Zhimulev
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
- Novosibirsk State University, Novosibirsk, Russia
- * E-mail:
| | - Tatyana Yu. Zykova
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Fyodor P. Goncharov
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Varvara A. Khoroshko
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Olga V. Demakova
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Valeriy F. Semeshin
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Galina V. Pokholkova
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Lidiya V. Boldyreva
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Darya S. Demidova
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
- Novosibirsk State University, Novosibirsk, Russia
| | - Vladimir N. Babenko
- Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Sergey A. Demakov
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Elena S. Belyaeva
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
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49
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Makunin IV, Kolesnikova TD, Andreyenkova NG. Underreplicated regions in Drosophila melanogaster are enriched with fast-evolving genes and highly conserved noncoding sequences. Genome Biol Evol 2014; 6:2050-60. [PMID: 25062918 PMCID: PMC4159006 DOI: 10.1093/gbe/evu156] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Many late replicating regions are underreplicated in polytene chromosomes of Drosophila melanogaster. These regions contain silenced chromatin and overlap long syntenic blocks of conserved gene order in drosophilids. In this report we show that in D. melanogaster the underreplicated regions are enriched with fast-evolving genes lacking homologs in distant species such as mosquito or human, indicating that the phylogenetic conservation of genes correlates with replication timing and chromatin status. Drosophila genes without human homologs located in the underreplicated regions have higher nonsynonymous substitution rate and tend to encode shorter proteins when compared with those in the adjacent regions. At the same time, the underreplicated regions are enriched with ultraconserved elements and highly conserved noncoding sequences, especially in introns of very long genes indicating the presence of an extensive regulatory network that may be responsible for the conservation of gene order in these regions. The regions have a modest preference for long noncoding RNAs but are depleted for small nucleolar RNAs, microRNAs, and transfer RNAs. Our results demonstrate that the underreplicated regions have a specific genic composition and distinct pattern of evolution.
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Affiliation(s)
- Igor V Makunin
- Research Computing Centre, The University of Queensland, St Lucia, Queensland, AustraliaInstitute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Tatyana D Kolesnikova
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, RussiaNovosibirsk State University, Russia
| | - Natalya G Andreyenkova
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
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Hannibal RL, Chuong EB, Rivera-Mulia JC, Gilbert DM, Valouev A, Baker JC. Copy number variation is a fundamental aspect of the placental genome. PLoS Genet 2014; 10:e1004290. [PMID: 24785991 PMCID: PMC4006706 DOI: 10.1371/journal.pgen.1004290] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 02/20/2014] [Indexed: 11/19/2022] Open
Abstract
Discovery of lineage-specific somatic copy number variation (CNV) in mammals has led to debate over whether CNVs are mutations that propagate disease or whether they are a normal, and even essential, aspect of cell biology. We show that 1,000N polyploid trophoblast giant cells (TGCs) of the mouse placenta contain 47 regions, totaling 138 Megabases, where genomic copies are underrepresented (UR). UR domains originate from a subset of late-replicating heterochromatic regions containing gene deserts and genes involved in cell adhesion and neurogenesis. While lineage-specific CNVs have been identified in mammalian cells, classically in the immune system where V(D)J recombination occurs, we demonstrate that CNVs form during gestation in the placenta by an underreplication mechanism, not by recombination nor deletion. Our results reveal that large scale CNVs are a normal feature of the mammalian placental genome, which are regulated systematically during embryogenesis and are propagated by a mechanism of underreplication. Generally, every mammalian cell has the same complement of each part of its genome. However, copy number variation (CNV) can occur, where, compared to the rest of its genome, a cell has either more or less of a specific genomic region. It is unknown whether CNVs cause disease, or whether they are a normal aspect of cell biology. We investigated CNVs in polyploid trophoblast giant cells (TGCs) of the mouse placenta, which have up to 1,000 copies of the genome in each cell. We found that there are 47 regions with decreased copy number in TGCs, which we call underrepresented (UR) domains. These domains are marked in the TGC progenitor cells and we suggest that they gradually form during gestation due to slow replication versus fast replication of the rest of the genome. While UR domains contain cell adhesion and neuronal genes, they also contain significantly fewer genes than other genomic regions. Our results demonstrate that CNVs are a normal feature of the mammalian placental genome, which are regulated systematically during pregnancy.
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Affiliation(s)
- Roberta L. Hannibal
- Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Edward B. Chuong
- Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Juan Carlos Rivera-Mulia
- Department of Biological Science, Florida State University, Tallahassee, Tallahassee Florida, United States of America
| | - David M. Gilbert
- Department of Biological Science, Florida State University, Tallahassee, Tallahassee Florida, United States of America
| | - Anton Valouev
- Division of Bioinformatics, Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles, California, United States of America
| | - Julie C. Baker
- Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
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