1
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Yang L, Zhu A, Aman JM, Denberg D, Kilwein MD, Marmion RA, Johnson ANT, Veraksa A, Singh M, Wühr M, Shvartsman SY. ERK synchronizes embryonic cleavages in Drosophila. Dev Cell 2024:S1534-5807(24)00487-8. [PMID: 39208802 DOI: 10.1016/j.devcel.2024.08.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 06/13/2024] [Accepted: 08/05/2024] [Indexed: 09/04/2024]
Abstract
Extracellular-signal-regulated kinase (ERK) signaling controls development and homeostasis and is genetically deregulated in human diseases, including neurocognitive disorders and cancers. Although the list of ERK functions is vast and steadily growing, the full spectrum of processes controlled by any specific ERK activation event remains unknown. Here, we show how ERK functions can be systematically identified using targeted perturbations and global readouts of ERK activation. Our experimental model is the Drosophila embryo, where ERK signaling at the embryonic poles has thus far only been associated with the transcriptional patterning of the future larva. Through a combination of live imaging and phosphoproteomics, we demonstrated that ERK activation at the poles is also critical for maintaining the speed and synchrony of embryonic cleavages. The presented approach to interrogating phosphorylation networks identifies a hidden function of a well-studied signaling event and sets the stage for similar studies in other organisms.
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Affiliation(s)
- Liu Yang
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Audrey Zhu
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Chemical & Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Javed M Aman
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Computer Science, Princeton University, Princeton, NJ 08544, USA
| | - David Denberg
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Program in Quantitative and Computational Biology, Princeton University, Princeton, NJ 08544, USA
| | - Marcus D Kilwein
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Robert A Marmion
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Alex N T Johnson
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Chemical & Biological Engineering, Princeton University, Princeton, NJ 08544, USA; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Alexey Veraksa
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Mona Singh
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Computer Science, Princeton University, Princeton, NJ 08544, USA
| | - Martin Wühr
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Chemical & Biological Engineering, Princeton University, Princeton, NJ 08544, USA; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
| | - Stanislav Y Shvartsman
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Program in Quantitative and Computational Biology, Princeton University, Princeton, NJ 08544, USA; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Flatiron Institute, New York, NY 10010, USA.
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2
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Wang W, Ji L, Jing X, Zhao P, Xia Q. MicroRNA let-7 targets BmCDK1 to regulate cell proliferation and endomitosis of silk gland in the silkworm, Bombyx mori. INSECT SCIENCE 2024; 31:1026-1040. [PMID: 38053466 DOI: 10.1111/1744-7917.13302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Revised: 09/17/2023] [Accepted: 10/19/2023] [Indexed: 12/07/2023]
Abstract
MicroRNAs play critical roles in multiple developmental processes in insects. Our previous study showed that CRISPR/Cas9-mediated knock down of the microRNA let-7 in silkworms increased the size of larvae and silk glands, thereby improving the silk production capacity. In this study, we elucidate the molecular mechanism underlying of let-7 regulates growth. Identification of differentially expressed genes in response to let-7 knock down revealed enrichment of pathways associated with cell proliferation and DNA replication. let-7 dysregulation affected the cell cycle and proliferation of the Bombyx mori cell line BmN. Dual-luciferase and target site mutation assays showed that BmCDK1 is a direct target gene of let-7, with only 1 binding site on its 3'-untranslated region. RNA interference of BmCDK1 inhibited cell proliferation, but this effect was counteracted by co-transfection with let-7 antagomir. Moreover, let-7 knock down induced BmCDK1 expression and promoted cell proliferation in multiple tissues, and further induced endomitosis in the silk gland in vivo. Knock down of BmCDK1 resulted in abnormal formation of a new epidermis, and larval development was arrested at the 2nd or 3rd molt stage. Taken together, our results demonstrated that BmCDK1 is a novel target of let-7 in cell fate determination, possessing potential for improving silk yield in silkworm.
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Affiliation(s)
- Wei Wang
- Integrative Science Center of Germplasm Creation in Western China (Chongqing) Science City, Biological Science Research Center, Southwest University, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing, China
- Engineering Laboratory of Sericultural and Functional Genome and Biotechnology, Development and Reform Commission, Chongqing, China
| | - Linshengzhe Ji
- Integrative Science Center of Germplasm Creation in Western China (Chongqing) Science City, Biological Science Research Center, Southwest University, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing, China
| | - Xinyuan Jing
- Integrative Science Center of Germplasm Creation in Western China (Chongqing) Science City, Biological Science Research Center, Southwest University, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing, China
| | - Ping Zhao
- Integrative Science Center of Germplasm Creation in Western China (Chongqing) Science City, Biological Science Research Center, Southwest University, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing, China
- Engineering Laboratory of Sericultural and Functional Genome and Biotechnology, Development and Reform Commission, Chongqing, China
| | - Qingyou Xia
- Integrative Science Center of Germplasm Creation in Western China (Chongqing) Science City, Biological Science Research Center, Southwest University, China
- Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Chongqing, China
- Engineering Laboratory of Sericultural and Functional Genome and Biotechnology, Development and Reform Commission, Chongqing, China
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3
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Deichsel S, Gahr BM, Mastel H, Preiss A, Nagel AC. Numerous Serine/Threonine Kinases Affect Blood Cell Homeostasis in Drosophila melanogaster. Cells 2024; 13:576. [PMID: 38607015 PMCID: PMC11011202 DOI: 10.3390/cells13070576] [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: 02/20/2024] [Revised: 03/20/2024] [Accepted: 03/25/2024] [Indexed: 04/13/2024] Open
Abstract
Blood cells in Drosophila serve primarily innate immune responses. Various stressors influence blood cell homeostasis regarding both numbers and the proportion of blood cell types. The principle molecular mechanisms governing hematopoiesis are conserved amongst species and involve major signaling pathways like Notch, Toll, JNK, JAK/Stat or RTK. Albeit signaling pathways generally rely on the activity of protein kinases, their specific contribution to hematopoiesis remains understudied. Here, we assess the role of Serine/Threonine kinases with the potential to phosphorylate the transcription factor Su(H) in crystal cell homeostasis. Su(H) is central to Notch signal transduction, and its inhibition by phosphorylation impedes crystal cell formation. Overall, nearly twenty percent of all Drosophila Serine/Threonine kinases were studied in two assays, global and hemocyte-specific overexpression and downregulation, respectively. Unexpectedly, the majority of kinases influenced crystal cell numbers, albeit only a few were related to hematopoiesis so far. Four kinases appeared essential for crystal cell formation, whereas most kinases restrained crystal cell development. This group comprises all kinase classes, indicative of the complex regulatory network underlying blood cell homeostasis. The rather indiscriminative response we observed opens the possibility that blood cells measure their overall phospho-status as a proxy for stress-signals, and activate an adaptive immune response accordingly.
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Affiliation(s)
- Sebastian Deichsel
- Department of Molecular Genetics, Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Bernd M. Gahr
- Department of Molecular Genetics, Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Helena Mastel
- Department of Molecular Genetics, Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Anette Preiss
- Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Anja C. Nagel
- Department of Molecular Genetics, Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany
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4
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Abstract
Embryonic development hinges on effective coordination of molecular events across space and time. Waves have recently emerged as constituting an ubiquitous mechanism that ensures rapid spreading of regulatory signals across embryos, as well as reliable control of their patterning, namely, for the emergence of body plan structures. In this article, we review a selection of recent quantitative work on signaling waves and present an overview of the theory of waves. Our aim is to provide a succinct yet comprehensive guiding reference for the theoretical frameworks by which signaling waves can arise in embryos. We start, then, from reaction-diffusion systems, both static and time dependent; move to excitable dynamics; and conclude with systems of coupled oscillators. We link these theoretical models to molecular mechanisms recently elucidated for the control of mitotic waves in early embryos, patterning of the vertebrate body axis, micropattern cultures, and bone regeneration. Our goal is to inspire experimental work that will advance theory in development and connect its predictions to quantitative biological observations. Expected final online publication date for the Annual Review of Biophysics, Volume 51 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, USA
| | - Massimo Vergassola
- Laboratoire de physique de l'École Normale Supérieure, CNRS, PSL Research University, Sorbonne Université, Paris, France; .,Department of Physics, University of California, San Diego, California, USA
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5
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Non-canonical Wnt signaling promotes directed migration of intestinal stem cells to sites of injury. Nat Commun 2021; 12:7150. [PMID: 34887411 PMCID: PMC8660829 DOI: 10.1038/s41467-021-27384-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 11/15/2021] [Indexed: 12/16/2022] Open
Abstract
Tissue regeneration after injury requires coordinated regulation of stem cell activation, division, and daughter cell differentiation, processes that are increasingly well understood in many regenerating tissues. How accurate stem cell positioning and localized integration of new cells into the damaged epithelium are achieved, however, remains unclear. Here, we show that enteroendocrine cells coordinate stem cell migration towards a wound in the Drosophila intestinal epithelium. In response to injury, enteroendocrine cells release the N-terminal domain of the PTK7 orthologue, Otk, which activates non-canonical Wnt signaling in intestinal stem cells, promoting actin-based protrusion formation and stem cell migration towards a wound. We find that this migratory behavior is closely linked to proliferation, and that it is required for efficient tissue repair during injury. Our findings highlight the role of non-canonical Wnt signaling in regeneration of the intestinal epithelium, and identify enteroendocrine cell-released ligands as critical coordinators of intestinal stem cell migration.
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6
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Mofatteh M, Echegaray-Iturra F, Alamban A, Dalla Ricca F, Bakshi A, Aydogan MG. Autonomous clocks that regulate organelle biogenesis, cytoskeletal organization, and intracellular dynamics. eLife 2021; 10:e72104. [PMID: 34586070 PMCID: PMC8480978 DOI: 10.7554/elife.72104] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 09/14/2021] [Indexed: 12/27/2022] Open
Abstract
How do cells perceive time? Do cells use temporal information to regulate the production/degradation of their enzymes, membranes, and organelles? Does controlling biological time influence cytoskeletal organization and cellular architecture in ways that confer evolutionary and physiological advantages? Potential answers to these fundamental questions of cell biology have historically revolved around the discussion of 'master' temporal programs, such as the principal cyclin-dependent kinase/cyclin cell division oscillator and the circadian clock. In this review, we provide an overview of the recent evidence supporting an emerging concept of 'autonomous clocks,' which under normal conditions can be entrained by the cell cycle and/or the circadian clock to run at their pace, but can also run independently to serve their functions if/when these major temporal programs are halted/abrupted. We begin the discussion by introducing recent developments in the study of such clocks and their roles at different scales and complexities. We then use current advances to elucidate the logic and molecular architecture of temporal networks that comprise autonomous clocks, providing important clues as to how these clocks may have evolved to run independently and, sometimes at the cost of redundancy, have strongly coupled to run under the full command of the cell cycle and/or the circadian clock. Next, we review a list of important recent findings that have shed new light onto potential hallmarks of autonomous clocks, suggestive of prospective theoretical and experimental approaches to further accelerate their discovery. Finally, we discuss their roles in health and disease, as well as possible therapeutic opportunities that targeting the autonomous clocks may offer.
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Affiliation(s)
- Mohammad Mofatteh
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
| | - Fabio Echegaray-Iturra
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
| | - Andrew Alamban
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
| | - Francesco Dalla Ricca
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
| | - Anand Bakshi
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
| | - Mustafa G Aydogan
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
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7
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Abstract
Understanding the mechanisms of embryonic cell cycles is a central goal of developmental biology, as the regulation of the cell cycle must be closely coordinated with other events during early embryogenesis. Quantitative imaging approaches have recently begun to reveal how the cell cycle oscillator is controlled in space and time, and how it is integrated with mechanical signals to drive morphogenesis. Here, we discuss how the Drosophila embryo has served as an excellent model for addressing the molecular and physical mechanisms of embryonic cell cycles, with comparisons to other model systems to highlight conserved and species-specific mechanisms. We describe how the rapid cleavage divisions characteristic of most metazoan embryos require chemical waves and cytoplasmic flows to coordinate morphogenesis across the large expanse of the embryo. We also outline how, in the late cleavage divisions, the cell cycle is inter-regulated with the activation of gene expression to ensure a reliable maternal-to-zygotic transition. Finally, we discuss how precise transcriptional regulation of the timing of mitosis ensures that tissue morphogenesis and cell proliferation are tightly controlled during gastrulation.
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Affiliation(s)
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27705, USA
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8
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Liu B, Zhao H, Wu K, Großhans J. Temporal Gradients Controlling Embryonic Cell Cycle. BIOLOGY 2021; 10:biology10060513. [PMID: 34207742 PMCID: PMC8228447 DOI: 10.3390/biology10060513] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 06/05/2021] [Accepted: 06/07/2021] [Indexed: 12/17/2022]
Abstract
Simple Summary Embryonic cells sense temporal gradients of regulatory signals to determine whether and when to proceed or remodel the cell cycle. Such a control mechanism is allowed to accurately link the cell cycle with the developmental program, including cell differentiation, morphogenesis, and gene expression. The mid-blastula transition has been a paradigm for timing in early embryogenesis in frog, fish, and fly, among others. It has been argued for decades now if the events associated with the mid-blastula transition, i.e., the onset of zygotic gene expression, remodeling of the cell cycle, and morphological changes, are determined by a control mechanism or by absolute time. Recent studies indicate that multiple independent signals and mechanisms contribute to the timing of these different processes. Here, we focus on the mechanisms for cell cycle remodeling, specifically in Drosophila, which relies on gradual changes of the signal over time. We discuss pathways for checkpoint activation, decay of Cdc25 protein levels, as well as depletion of deoxyribonucleotide metabolites and histone proteins. The gradual changes of these signals are linked to Cdk1 activity by readout mechanisms involving thresholds. Abstract Cell proliferation in early embryos by rapid cell cycles and its abrupt pause after a stereotypic number of divisions present an attractive system to study the timing mechanism in general and its coordination with developmental progression. In animals with large eggs, such as Xenopus, zebrafish, or Drosophila, 11–13 very fast and synchronous cycles are followed by a pause or slowdown of the cell cycle. The stage when the cell cycle is remodeled falls together with changes in cell behavior and activation of the zygotic genome and is often referred to as mid-blastula transition. The number of fast embryonic cell cycles represents a clear and binary readout of timing. Several factors controlling the cell cycle undergo dynamics and gradual changes in activity or concentration and thus may serve as temporal gradients. Recent studies have revealed that the gradual loss of Cdc25 protein, gradual depletion of free deoxyribonucleotide metabolites, or gradual depletion of free histone proteins impinge on Cdk1 activity in a threshold-like manner. In this review, we will highlight with a focus on Drosophila studies our current understanding and recent findings on the generation and readout of these temporal gradients, as well as their position within the regulatory network of the embryonic cell cycle.
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Affiliation(s)
- Boyang Liu
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan 250012, China; (B.L.); (H.Z.); (K.W.)
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Shandong University, Jinan 250012, China
- Shandong Key Laboratory of Reproductive Medicine, Jinan 250012, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan 250012, China
| | - Han Zhao
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan 250012, China; (B.L.); (H.Z.); (K.W.)
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Shandong University, Jinan 250012, China
- Shandong Key Laboratory of Reproductive Medicine, Jinan 250012, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan 250012, China
| | - Keliang Wu
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan 250012, China; (B.L.); (H.Z.); (K.W.)
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Shandong University, Jinan 250012, China
- Shandong Key Laboratory of Reproductive Medicine, Jinan 250012, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan 250012, China
| | - Jörg Großhans
- Department of Biology, Philipps University, 35043 Marburg, Germany
- Correspondence:
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9
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Wu C, Twort VG, Newcomb RD, Buckley TR. Divergent Gene Expression Following Duplication of Meiotic Genes in the Stick Insect Clitarchus hookeri. Genome Biol Evol 2021; 13:6245840. [PMID: 33885769 DOI: 10.1093/gbe/evab060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/17/2021] [Indexed: 01/02/2023] Open
Abstract
Some animal groups, such as stick insects (Phasmatodea), have repeatedly evolved alternative reproductive strategies, including parthenogenesis. Genomic studies have found modification of the genes underlying meiosis exists in some of these animals. Here we examine the evolution of copy number, evolutionary rate, and gene expression in candidate meiotic genes of the New Zealand geographic parthenogenetic stick insect Clitarchus hookeri. We characterized 101 genes from a de novo transcriptome assembly from female and male gonads that have homology with meiotic genes from other arthropods. For each gene we determined copy number, the pattern of gene duplication relative to other arthropod orthologs, and the potential for meiosis-specific expression. There are five genes duplicated in C. hookeri, including one also duplicated in the stick insect Timema cristinae, that are not or are uncommonly duplicated in other arthropods. These included two sister chromatid cohesion associated genes (SA2 and SCC2), a recombination gene (HOP1), an RNA-silencing gene (AGO2) and a cell-cycle regulation gene (WEE1). Interestingly, WEE1 and SA2 are also duplicated in the cyclical parthenogenetic aphid Acyrthosiphon pisum and Daphnia duplex, respectively, indicating possible roles in the evolution of reproductive mode. Three of these genes (SA2, SCC2, and WEE1) have one copy displaying gonad-specific expression. All genes, with the exception of WEE1, have significantly different nonsynonymous/synonymous ratios between the gene duplicates, indicative of a shift in evolutionary constraints following duplication. These results suggest that stick insects may have evolved genes with novel functions in gamete production by gene duplication.
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Affiliation(s)
- Chen Wu
- School of Biological Sciences, The University of Auckland, New Zealand.,Manaaki Whenua-Landcare Research, Auckland, New Zealand.,New Zealand Institute for Plant & Food Research Ltd, Auckland, New Zealand
| | - Victoria G Twort
- School of Biological Sciences, The University of Auckland, New Zealand.,Manaaki Whenua-Landcare Research, Auckland, New Zealand.,Zoology Unit, Finnish Museum of Natural History, LUOMUS, University of Helsinki, Finland
| | - Richard D Newcomb
- School of Biological Sciences, The University of Auckland, New Zealand.,New Zealand Institute for Plant & Food Research Ltd, Auckland, New Zealand
| | - Thomas R Buckley
- School of Biological Sciences, The University of Auckland, New Zealand.,Manaaki Whenua-Landcare Research, Auckland, New Zealand
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10
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Shindo Y, Amodeo AA. Excess histone H3 is a competitive Chk1 inhibitor that controls cell-cycle remodeling in the early Drosophila embryo. Curr Biol 2021; 31:2633-2642.e6. [PMID: 33848457 DOI: 10.1016/j.cub.2021.03.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 02/08/2021] [Accepted: 03/10/2021] [Indexed: 12/31/2022]
Abstract
The DNA damage checkpoint is crucial to protect genome integrity.1,2 However, the early embryos of many metazoans sacrifice this safeguard to allow for rapid cleavage divisions that are required for speedy development. At the mid-blastula transition (MBT), embryos switch from rapid cleavage divisions to slower, patterned divisions with the addition of gap phases and acquisition of DNA damage checkpoints. The timing of the MBT is dependent on the nuclear-to-cytoplasmic (N/C ratio)3-7 and the activation of the checkpoint kinase, Chk1.8-17 How Chk1 activity is coupled to the N/C ratio has remained poorly understood. Here, we show that dynamic changes in histone H3 availability in response to the increasing N/C ratio control Chk1 activity and thus time the MBT in the Drosophila embryo. We show that excess H3 in the early cycles interferes with cell-cycle slowing independent of chromatin incorporation. We find that the N-terminal tail of H3 acts as a competitive inhibitor of Chk1 in vitro and reduces Chk1 activity in vivo. Using a H3-tail mutant that has reduced Chk1 inhibitor activity, we show that the amount of available Chk1 sites in the H3 pool controls the dynamics of cell-cycle progression. Mathematical modeling quantitatively supports a mechanism where titration of H3 during early cleavage cycles regulates Chk1-dependent cell-cycle slowing. This study defines Chk1 regulation by H3 as a key mechanism that coordinates cell-cycle remodeling with developmental progression.
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Affiliation(s)
- Yuki Shindo
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Amanda A Amodeo
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA.
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11
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Gao M, Liu T, Li J, Guan Q, Wang H, Yan S, Li Z, Zuo D, Zhang W, Wu Y. YAN, a novel microtubule inhibitor, inhibits P-gp and MRP1 function and induces mitotic slippage followed by apoptosis in multidrug-resistant A549/Taxol cells. Toxicol In Vitro 2020; 69:104971. [DOI: 10.1016/j.tiv.2020.104971] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 08/09/2020] [Accepted: 08/13/2020] [Indexed: 01/05/2023]
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12
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Mohallem R, Aryal UK. Regulators of TNFα mediated insulin resistance elucidated by quantitative proteomics. Sci Rep 2020; 10:20878. [PMID: 33257747 PMCID: PMC7705713 DOI: 10.1038/s41598-020-77914-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 11/03/2020] [Indexed: 12/21/2022] Open
Abstract
Obesity is a growing epidemic worldwide and is a major risk factor for several chronic diseases, including diabetes, kidney disease, heart disease, and cancer. Obesity often leads to type 2 diabetes mellitus, via the increased production of proinflammatory cytokines such as tumor necrosis factor-α (TNFα). Our study combines different proteomic techniques to investigate the changes in the global proteome, secretome and phosphoproteome of adipocytes under chronic inflammation condition, as well as fundamental cross-talks between different cellular pathways regulated by chronic TNFα exposure. Our results show that many key regulator proteins of the canonical and non-canonical NF-κB pathways, such as Nfkb2, and its downstream effectors, including Csf-1 and Lgals3bp, directly involved in leukocyte migration and invasion, were significantly upregulated at the intra and extracellular proteomes suggesting the progression of inflammation. Our data provides evidence of several key proteins that play a role in the development of insulin resistance.
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Affiliation(s)
- Rodrigo Mohallem
- Department of Comparative Pathobiology, Purdue University, West Lafayette, USA
- Purdue Proteomics Facility, Bindley Bioscience Center, Purdue University, West Lafayette, USA
| | - Uma K Aryal
- Department of Comparative Pathobiology, Purdue University, West Lafayette, USA.
- Purdue Proteomics Facility, Bindley Bioscience Center, Purdue University, West Lafayette, USA.
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13
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Willms RJ, Zeng J, Campbell SD. Myt1 Kinase Couples Mitotic Cell Cycle Exit with Differentiation in Drosophila. Cell Rep 2020; 33:108400. [DOI: 10.1016/j.celrep.2020.108400] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 09/03/2020] [Accepted: 10/27/2020] [Indexed: 12/16/2022] Open
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14
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Aydogan MG, Steinacker TL, Mofatteh M, Wilmott ZM, Zhou FY, Gartenmann L, Wainman A, Saurya S, Novak ZA, Wong SS, Goriely A, Boemo MA, Raff JW. An Autonomous Oscillation Times and Executes Centriole Biogenesis. Cell 2020; 181:1566-1581.e27. [PMID: 32531200 PMCID: PMC7327525 DOI: 10.1016/j.cell.2020.05.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 12/19/2019] [Accepted: 05/08/2020] [Indexed: 01/18/2023]
Abstract
The accurate timing and execution of organelle biogenesis is crucial for cell physiology. Centriole biogenesis is regulated by Polo-like kinase 4 (Plk4) and initiates in S-phase when a daughter centriole grows from the side of a pre-existing mother. Here, we show that a Plk4 oscillation at the base of the growing centriole initiates and times centriole biogenesis to ensure that centrioles grow at the right time and to the right size. The Plk4 oscillation is normally entrained to the cell-cycle oscillator but can run autonomously of it-potentially explaining why centrioles can duplicate independently of cell-cycle progression. Mathematical modeling indicates that the Plk4 oscillation can be generated by a time-delayed negative feedback loop in which Plk4 inactivates the interaction with its centriolar receptor through multiple rounds of phosphorylation. We hypothesize that similar organelle-specific oscillations could regulate the timing and execution of organelle biogenesis more generally.
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Affiliation(s)
- Mustafa G Aydogan
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK.
| | - Thomas L Steinacker
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Mohammad Mofatteh
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Zachary M Wilmott
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK; Mathematical Institute, University of Oxford, Oxford OX2 6GG, UK
| | - Felix Y Zhou
- Ludwig Institute for Cancer Research, University of Oxford, Oxford OX3 7DQ, UK
| | - Lisa Gartenmann
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Alan Wainman
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Saroj Saurya
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Zsofia A Novak
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Siu-Shing Wong
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Alain Goriely
- Mathematical Institute, University of Oxford, Oxford OX2 6GG, UK
| | - Michael A Boemo
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK.
| | - Jordan W Raff
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK.
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15
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Liu B, Gregor I, Müller HA, Großhans J. Fluorescence fluctuation analysis reveals PpV dependent Cdc25 protein dynamics in living embryos. PLoS Genet 2020; 16:e1008735. [PMID: 32251417 PMCID: PMC7162543 DOI: 10.1371/journal.pgen.1008735] [Citation(s) in RCA: 5] [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: 11/25/2019] [Revised: 04/16/2020] [Accepted: 03/25/2020] [Indexed: 12/21/2022] Open
Abstract
The protein phosphatase Cdc25 is a key regulator of the cell cycle by activating Cdk-cyclin complexes. Cdc25 is regulated by its expression levels and post-translational mechanisms. In early Drosophila embryogenesis, Cdc25/Twine drives the fast and synchronous nuclear cycles. A pause in the cell cycle and the remodeling to a more generic cell cycle mode with a gap phase are determined by Twine inactivation and destruction in early interphase 14, in response to zygotic genome activation. Although the pseudokinase Tribbles contributes to the timely degradation of Twine, Twine levels are controlled by additional yet unknown post-translational mechanisms. Here, we apply a non-invasive method based on fluorescence fluctuation analysis (FFA) to record the absolute concentration profiles of Twine with minute-scale resolution in single living embryos. Employing this assay, we found that Protein phosphatase V (PpV), the homologue of the catalytic subunit of human PP6, ensures appropriately low Twine protein levels at the onset of interphase 14. PpV controls directly or indirectly the phosphorylation of Twine at multiple serine and threonine residues as revealed by phosphosite mapping. Mutational analysis confirmed that these sites are involved in control of Twine protein dynamics, and cell cycle remodeling is delayed in a fraction of the phosphosite mutant embryos. Our data reveal a novel mechanism for control of Twine protein levels and their significance for embryonic cell cycle remodeling.
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Affiliation(s)
- Boyang Liu
- Fachbereich Biologie (FB17), Philipps-Universität Marburg, Marburg, Germany
- Institut für Entwicklungsbiochemie, Universitätsmedizin, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Ingo Gregor
- Drittes Physikalisches Institut, Georg-August-Universität Göttingen, Göttingen, Germany
| | - H.-Arno Müller
- Fachgebiet Entwicklungsgenetik, Institut für Biologie, Universität Kassel, Kassel, Germany
| | - Jörg Großhans
- Fachbereich Biologie (FB17), Philipps-Universität Marburg, Marburg, Germany
- Institut für Entwicklungsbiochemie, Universitätsmedizin, Georg-August-Universität Göttingen, Göttingen, Germany
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16
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Yu L, Li G, Deng J, Jiang X, Xue J, Zhu Y, Huang W, Tang B, Duan R. The UFM1 cascade times mitosis entry associated with microcephaly. FASEB J 2019; 34:1319-1330. [PMID: 31914610 DOI: 10.1096/fj.201901751r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 10/15/2019] [Accepted: 11/14/2019] [Indexed: 02/02/2023]
Abstract
Posttranslational modifications enhance the functional diversity of the proteome by modifying the substrates. The UFM1 cascade is a novel ubiquitin-like modification system. The mutations in UFM1, its E1 (UBA5) and E2 (UFC1), have been identified in patients with microcephaly. However, its pathological mechanisms remain unclear. Herein, we observed the disruption of the UFM1 cascade in Drosophila neuroblasts (NBs) decreased the number of NBs, leading to a smaller brain size. The lack of ufmylation in NBs resulted in an increased mitotic index and an extended G2/M phase, indicating a defect in mitotic progression. In addition, live imaging of the embryos revealed an impaired E3 ligase (Ufl1) function resulted in premature entry into mitosis and failed cellularization. Even worse, the embryonic lethality occurred as early as within the first few mitotic cycles following the depletion of Ufm1. Knockdown of ufmylation in the fixed embryos exhibited severe phenotypes, including detached centrosomes, defective microtubules, and DNA bridge. Furthermore, we observed that the UFM1 cascade could alter the level of phosphorylation on tyrosine-15 of CDK1 (pY15-CDK1), which is a negative regulator of the G2 to M transition. These findings yield unambiguous evidence suggesting that the UFM1 cascade is a microcephaly-causing factor that regulates the progression of the cell cycle at mitosis phase entry.
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Affiliation(s)
- Li Yu
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, China
| | - Guangxu Li
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, China
| | - Jing Deng
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, China
| | - Xuan Jiang
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, China
| | - Jin Xue
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, China
| | - Yingbao Zhu
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, China
| | - Wen Huang
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, China
| | - Beisha Tang
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.,Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Ranhui Duan
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, China.,Hunan Key Laboratory of Animal Models for Human Diseases, Central South University, Changsha, China
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17
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Chari S, Wilky H, Govindan J, Amodeo AA. Histone concentration regulates the cell cycle and transcription in early development. Development 2019; 146:dev.177402. [PMID: 31511251 DOI: 10.1242/dev.177402] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 08/28/2019] [Indexed: 12/12/2022]
Abstract
The early embryos of many animals, including flies, fish and frogs, have unusually rapid cell cycles and delayed onset of transcription. These divisions are dependent on maternally supplied RNAs and proteins including histones. Previous work suggests that the pool size of maternally provided histones can alter the timing of zygotic genome activation (ZGA) in frogs and fish. Here, we examine the effects of under- and overexpression of maternal histones in Drosophila embryogenesis. Decreasing histone concentration advances zygotic transcription, cell cycle elongation, Chk1 activation and gastrulation. Conversely, increasing histone concentration delays transcription and results in an additional nuclear cycle before gastrulation. Numerous zygotic transcripts are sensitive to histone concentration, and the promoters of histone-sensitive genes are associated with specific chromatin features linked to increased histone turnover. These include enrichment of the pioneer transcription factor Zelda, and lack of SIN3A and associated histone deacetylases. Our findings uncover a crucial regulatory role for histone concentrations in ZGA of Drosophila.
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Affiliation(s)
- Sudarshan Chari
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Henry Wilky
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Jayalakshmi Govindan
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Amanda A Amodeo
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
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18
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Abstract
The activation of the zygotic genome and onset of transcription in blastula embryos is linked to changes in cell behavior and remodeling of the cell cycle and constitutes a transition from exclusive maternal to zygotic control of development. This step in development is referred to as mid-blastula transition and has served as a paradigm for the link between developmental program and cell behavior and morphology. Here, we discuss the mechanism and functional relationships between the zygotic genome activation and cell cycle control during mid-blastula transition with a focus on Drosophila embryos.
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Affiliation(s)
- Boyang Liu
- Institute for Developmental Biochemistry, Medical School, University of Göttingen, Justus-von-Liebig-Weg11, Göttingen 37077, Germany
| | - Jörg Grosshans
- Institute for Developmental Biochemistry, Medical School, University of Göttingen, Justus-von-Liebig-Weg11, Göttingen 37077, Germany.
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19
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Deneke VE, Melbinger A, Vergassola M, Di Talia S. Waves of Cdk1 Activity in S Phase Synchronize the Cell Cycle in Drosophila Embryos. Dev Cell 2017; 38:399-412. [PMID: 27554859 DOI: 10.1016/j.devcel.2016.07.023] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 06/13/2016] [Accepted: 07/26/2016] [Indexed: 01/16/2023]
Abstract
Embryos of most metazoans undergo rapid and synchronous cell cycles following fertilization. While diffusion is too slow for synchronization of mitosis across large spatial scales, waves of Cdk1 activity represent a possible process of synchronization. However, the mechanisms regulating Cdk1 waves during embryonic development remain poorly understood. Using biosensors of Cdk1 and Chk1 activities, we dissect the regulation of Cdk1 waves in the Drosophila syncytial blastoderm. We show that Cdk1 waves are not controlled by the mitotic switch but by a double-negative feedback between Cdk1 and Chk1. Using mathematical modeling and surgical ligations, we demonstrate a fundamental distinction between S phase Cdk1 waves, which propagate as active trigger waves in an excitable medium, and mitotic Cdk1 waves, which propagate as passive phase waves. Our findings show that in Drosophila embryos, Cdk1 positive feedback serves primarily to ensure the rapid onset of mitosis, while wave propagation is regulated by S phase events.
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Affiliation(s)
- Victoria E Deneke
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Anna Melbinger
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Massimo Vergassola
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
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20
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Regulation of DNA Replication in Early Embryonic Cleavages. Genes (Basel) 2017; 8:genes8010042. [PMID: 28106858 PMCID: PMC5295036 DOI: 10.3390/genes8010042] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 01/06/2017] [Accepted: 01/11/2017] [Indexed: 11/18/2022] Open
Abstract
Early embryonic cleavages are characterized by short and highly synchronous cell cycles made of alternating S- and M-phases with virtually absent gap phases. In this contracted cell cycle, the duration of DNA synthesis can be extraordinarily short. Depending on the organism, the whole genome of an embryo is replicated at a speed that is between 20 to 60 times faster than that of a somatic cell. Because transcription in the early embryo is repressed, DNA synthesis relies on a large stockpile of maternally supplied proteins stored in the egg representing most, if not all, cellular genes. In addition, in early embryonic cell cycles, both replication and DNA damage checkpoints are inefficient. In this article, we will review current knowledge on how DNA synthesis is regulated in early embryos and discuss possible consequences of replicating chromosomes with little or no quality control.
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21
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Deneke VE, Melbinger A, Vergassola M, Di Talia S. Waves of Cdk1 Activity in S Phase Synchronize the Cell Cycle in Drosophila Embryos. Dev Cell 2016. [PMID: 27554859 DOI: 10.1016/j.devcel.2016.07.0240] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
Abstract
Embryos of most metazoans undergo rapid and synchronous cell cycles following fertilization. While diffusion is too slow for synchronization of mitosis across large spatial scales, waves of Cdk1 activity represent a possible process of synchronization. However, the mechanisms regulating Cdk1 waves during embryonic development remain poorly understood. Using biosensors of Cdk1 and Chk1 activities, we dissect the regulation of Cdk1 waves in the Drosophila syncytial blastoderm. We show that Cdk1 waves are not controlled by the mitotic switch but by a double-negative feedback between Cdk1 and Chk1. Using mathematical modeling and surgical ligations, we demonstrate a fundamental distinction between S phase Cdk1 waves, which propagate as active trigger waves in an excitable medium, and mitotic Cdk1 waves, which propagate as passive phase waves. Our findings show that in Drosophila embryos, Cdk1 positive feedback serves primarily to ensure the rapid onset of mitosis, while wave propagation is regulated by S phase events.
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Affiliation(s)
- Victoria E Deneke
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Anna Melbinger
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Massimo Vergassola
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
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22
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Ferree PL, Deneke VE, Di Talia S. Measuring time during early embryonic development. Semin Cell Dev Biol 2016; 55:80-8. [PMID: 26994526 PMCID: PMC4903905 DOI: 10.1016/j.semcdb.2016.03.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 03/15/2016] [Indexed: 11/27/2022]
Abstract
In most metazoans, embryonic development is orchestrated by a precise series of cellular behaviors. Understanding how such events are regulated to achieve a stereotypical temporal progression is a fundamental problem in developmental biology. In this review, we argue that studying the regulation of the cell cycle in early embryonic development will reveal novel principles of how embryos accurately measure time. We will discuss the strategies that have emerged from studying early development of Drosophila embryos. By comparing the development of flies to that of other metazoans, we will highlight both conserved and alternative mechanisms to generate precision during embryonic development.
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Affiliation(s)
- Patrick L Ferree
- Department of Cell Biology, Duke University Medical Center, Durham NC, United States
| | - Victoria E Deneke
- Department of Cell Biology, Duke University Medical Center, Durham NC, United States
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham NC, United States.
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23
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Yuan K, Seller CA, Shermoen AW, O'Farrell PH. Timing the Drosophila Mid-Blastula Transition: A Cell Cycle-Centered View. Trends Genet 2016; 32:496-507. [PMID: 27339317 DOI: 10.1016/j.tig.2016.05.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Revised: 05/19/2016] [Accepted: 05/23/2016] [Indexed: 11/18/2022]
Abstract
At the mid-blastula transition (MBT), externally developing embryos refocus from increasing cell number to elaboration of the body plan. Studies in Drosophila reveal a sequence of changes in regulators of Cyclin:Cdk1 that increasingly restricts the activity of this cell cycle kinase to slow cell cycles during early embryogenesis. By reviewing these events, we provide an outline of the mechanisms slowing the cell cycle at and around the time of MBT. The perspectives developed should provide a guiding paradigm for the study of other MBT changes as the embryo transits from maternal control to a regulatory program centered on the expression of zygotic genes.
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Affiliation(s)
- Kai Yuan
- Department of Biophysics and Biochemistry, University of California San Francisco (UCSF), San Francisco, CA 94158, USA
| | - Charles A Seller
- Department of Biophysics and Biochemistry, University of California San Francisco (UCSF), San Francisco, CA 94158, USA
| | - Antony W Shermoen
- Department of Biophysics and Biochemistry, University of California San Francisco (UCSF), San Francisco, CA 94158, USA
| | - Patrick H O'Farrell
- Department of Biophysics and Biochemistry, University of California San Francisco (UCSF), San Francisco, CA 94158, USA.
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24
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Ayeni JO, Campbell SD. "Ready, set, go": checkpoint regulation by Cdk1 inhibitory phosphorylation. Fly (Austin) 2015; 8:140-7. [PMID: 25483135 DOI: 10.4161/19336934.2014.969147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
ABSTRACT Cell cycle checkpoints prevent mitosis from occurring before DNA replication and repair are completed during S and G2 phases. The checkpoint mechanism involves inhibitory phosphorylation of Cdk1, a conserved kinase that regulates the onset of mitosis. Metazoans have two distinct Cdk1 inhibitory kinases with specialized developmental functions: Wee1 and Myt1. Ayeni et al used transgenic Cdk1 phospho-acceptor mutants to analyze how the distinct biochemical properties of these kinases affected their functions. They concluded from their results that phosphorylation of Cdk1 on Y15 was necessary and sufficient for G2/M checkpoint arrest in imaginal wing discs, whereas phosphorylation on T14 promoted chromosome stability by a different mechanism. A curious relationship was also noted between Y15 inhibitory phosphorylation and T161 activating phosphorylation. These unexpected complexities in Cdk1 inhibitory phosphorylation demonstrate that the checkpoint mechanism is not a simple binary "off/on" switch, but has at least three distinct states: "Ready", to prevent chromosome damage and apoptosis, "Set", for developmentally regulated G2 phase arrest, and "Go", when Cdc25 phosphatases remove inhibitory phosphates to trigger Cdk1 activation at the G2/M transition.
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Affiliation(s)
- J O Ayeni
- a Department of Biological Sciences ; University of Alberta ; Edmonton , AB , Canada
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25
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Takada S, Collins ER, Kurahashi K. The FHA domain determines Drosophila Chk2/Mnk localization to key mitotic structures and is essential for early embryonic DNA damage responses. Mol Biol Cell 2015; 26:1811-28. [PMID: 25808488 PMCID: PMC4436828 DOI: 10.1091/mbc.e14-07-1238] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 03/17/2015] [Indexed: 01/23/2023] Open
Abstract
DNA damage responses, including mitotic centrosome inactivation, cell-cycle delay in mitosis, and nuclear dropping from embryo cortex, maintain genome integrity in syncytial Drosophila embryos. A conserved signaling kinase, Chk2, known as Mnk/Loki, is essential for the responses. Here we demonstrate that functional EGFP-Mnk expressed from a transgene localizes to the nucleus, centrosomes, interkinetochore/centromere region, midbody, and pseudocleavage furrows without DNA damage and in addition forms numerous foci/aggregates on mitotic chromosomes upon DNA damage. We expressed EGFP-tagged Mnk deletion or point mutation variants and investigated domain functions of Mnk in vivo. A triple mutation in the phosphopeptide-binding site of the forkhead-associated (FHA) domain disrupted normal Mnk localization except to the nucleus. The mutation also disrupted Mnk foci formation on chromosomes upon DNA damage. FHA mutations and deletion of the SQ/TQ-cluster domain (SCD) abolished Mnk transphosphorylations and autophosphorylations, indicative of kinase activation after DNA damage. A potent NLS was found at the C-terminus, which is required for normal Mnk function. We propose that the FHA domain in Mnk plays essential dual functions in mediating embryonic DNA damage responses by means of its phosphopeptide-binding ability: activating Mnk in the nucleus upon DNA damage and recruiting Mnk to multiple subcellular structures independently of DNA damage.
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Affiliation(s)
- Saeko Takada
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Eric R Collins
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Kayo Kurahashi
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
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26
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Tong Y, Torrent M, Florjancic AS, Bromberg KD, Buchanan FG, Ferguson DC, Johnson EF, Lasko LM, Maag D, Merta PJ, Olson AM, Osterling DJ, Soni N, Shoemaker AR, Penning TD. Pyrimidine-based tricyclic molecules as potent and orally efficacious inhibitors of wee1 kinase. ACS Med Chem Lett 2015; 6:58-62. [PMID: 25589931 DOI: 10.1021/ml5002745] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 08/04/2014] [Indexed: 12/22/2022] Open
Abstract
Aided by molecular modeling, compounds with a pyrimidine-based tricyclic scaffold were designed and confirmed to inhibit Wee1 kinase. Structure-activity studies identified key pharmacophores at the aminoaryl and halo-benzene regions responsible for binding affinity with sub-nM K i values. The potent inhibitors demonstrated sub-μM activities in both functional and mechanism-based cellular assays and also possessed desirable pharmacokinetic profiles. The lead molecule, 31, showed oral efficacy in potentiating the antiproliferative activity of irinotecan, a cytotoxic agent, in a NCI-H1299 mouse xenograft model.
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Affiliation(s)
- Yunsong Tong
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Maricel Torrent
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Alan S. Florjancic
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Kenneth D. Bromberg
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Fritz G. Buchanan
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Debra C. Ferguson
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Eric F. Johnson
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Loren M. Lasko
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - David Maag
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Philip J. Merta
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Amanda M. Olson
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Donald J. Osterling
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Nirupama Soni
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Alexander R. Shoemaker
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
| | - Thomas D. Penning
- Cancer Research, ‡Molecular Modeling, §Pharmacology, and ∥High Throughput
Biology, Research and Development, AbbVie, 1 North
Waukegan Road, North Chicago, Illinois 60064-6114, United States
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27
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Coordinating Cell Cycle Remodeling with Transcriptional Activation at the Drosophila MBT. Curr Top Dev Biol 2015; 113:113-48. [DOI: 10.1016/bs.ctdb.2015.06.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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28
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Sopko R, Foos M, Vinayagam A, Zhai B, Binari R, Hu Y, Randklev S, Perkins LA, Gygi SP, Perrimon N. Combining genetic perturbations and proteomics to examine kinase-phosphatase networks in Drosophila embryos. Dev Cell 2014; 31:114-27. [PMID: 25284370 DOI: 10.1016/j.devcel.2014.07.027] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 06/24/2014] [Accepted: 07/28/2014] [Indexed: 02/07/2023]
Abstract
Connecting phosphorylation events to kinases and phosphatases is key to understanding the molecular organization and signaling dynamics of networks. We have generated a validated set of transgenic RNA-interference reagents for knockdown and characterization of all protein kinases and phosphatases present during early Drosophila melanogaster development. These genetic tools enable collection of sufficient quantities of embryos depleted of single gene products for proteomics. As a demonstration of an application of the collection, we have used multiplexed isobaric labeling for quantitative proteomics to derive global phosphorylation signatures associated with kinase-depleted embryos to systematically link phosphosites with relevant kinases. We demonstrate how this strategy uncovers kinase consensus motifs and prioritizes phosphoproteins for kinase target validation. We validate this approach by providing auxiliary evidence for Wee kinase-directed regulation of the chromatin regulator Stonewall. Further, we show how correlative phosphorylation at the site level can indicate function, as exemplified by Sterile20-like kinase-dependent regulation of Stat92E.
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Affiliation(s)
- Richelle Sopko
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
| | - Marianna Foos
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA
| | | | - Bo Zhai
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Richard Binari
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA
| | - Yanhui Hu
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Sakara Randklev
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA
| | | | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Norbert Perrimon
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA.
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Farrell JA, O'Farrell PH. From egg to gastrula: how the cell cycle is remodeled during the Drosophila mid-blastula transition. Annu Rev Genet 2014; 48:269-94. [PMID: 25195504 DOI: 10.1146/annurev-genet-111212-133531] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Many, if not most, embryos begin development with extremely short cell cycles that exhibit unusually rapid DNA replication and no gap phases. The commitment to the cell cycle in the early embryo appears to preclude many other cellular processes that only emerge as the cell cycle slows just prior to gastrulation at a major embryonic transition known as the mid-blastula transition (MBT). As reviewed here, genetic and molecular studies in Drosophila have identified changes that extend S phase and introduce a post-replicative gap phase, G2, to slow the cell cycle. Although many mysteries remain about the upstream regulators of these changes, we review the core mechanisms of the change in cell cycle regulation and discuss advances in our understanding of how these might be timed and triggered. Finally, we consider how the elements of this program may be conserved or changed in other organisms.
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Affiliation(s)
- Jeffrey A Farrell
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138;
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Stickel S, Su TT. Oncogenic mutations produce similar phenotypes in Drosophila tissues of diverse origins. Biol Open 2014; 3:201-9. [PMID: 24570398 PMCID: PMC4001236 DOI: 10.1242/bio.20147161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An emerging interest in oncology is to tailor treatment to particular cancer genotypes, i.e. oncogenic mutations present in the tumor, and not the tissue of cancer incidence. Integral to such a practice is the idea that the same oncogenic mutation(s) produces similar outcomes in different tissues. To test this idea experimentally, we studied tumors driven by a combination of Ras(V12) and scrib(1) mutations in Drosophila larvae. We found that tumors induced in tissues of neural ectodermal and mesodermal origins behaved similarly in every manner examined: cell cycle checkpoints, apoptosis, cellular morphology, increased aneuploidy and response to Taxol. We conclude that oncogenic effects override tissue-specific differences, at least for the mutations, tissues, and phenotypes studied herein.
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Affiliation(s)
- Stefanie Stickel
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309-0347, USA
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31
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miR-16 and miR-26a target checkpoint kinases Wee1 and Chk1 in response to p53 activation by genotoxic stress. Cell Death Dis 2013; 4:e953. [PMID: 24336073 PMCID: PMC3877554 DOI: 10.1038/cddis.2013.483] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Revised: 10/31/2013] [Accepted: 11/04/2013] [Indexed: 01/07/2023]
Abstract
The tumour suppressor p53 is a crucial regulator of cell cycle arrest and apoptosis by acting as a transcription factor to regulate a variety of genes. At least in part, this control is exerted by p53 via regulating expression of numerous microRNAs. We identified two abundantly expressed microRNAs, miR-16 and miR-26a, whose expression is regulated by p53 during the checkpoint arrest induced by the genotoxic drug, doxorubicin. Importantly, among the targets of these miRs are two critical checkpoint kinases, Chk1 and Wee1. The p53-dependent augmentation of miR-16 and miR-26a expression levels led to the cell cycle arrest of tumour cells in G1/S and increased apoptosis. Strikingly, the bioinformatics analysis of survival times for patients with breast and prostate cancers has revealed that co-expression of mir-16 and miR-26a correlated with a better survival outcome. Collectively, our data provide a novel mechanism whereby p53 represses Chk1 and Wee1 expression, at least partially, via upregulation of miR-16 and miR-26a and thus sensitizes tumour cells to genotoxic therapies.
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32
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Dual phosphorylation of cdk1 coordinates cell proliferation with key developmental processes in Drosophila. Genetics 2013; 196:197-210. [PMID: 24214341 DOI: 10.1534/genetics.113.156281] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Eukaryotic organisms use conserved checkpoint mechanisms that regulate Cdk1 by inhibitory phosphorylation to prevent mitosis from interfering with DNA replication or repair. In metazoans, this checkpoint mechanism is also used for coordinating mitosis with dynamic developmental processes. Inhibitory phosphorylation of Cdk1 is catalyzed by Wee1 kinases that phosphorylate tyrosine 15 (Y15) and dual-specificity Myt1 kinases found only in metazoans that phosphorylate Y15 and the adjacent threonine (T14) residue. Despite partially redundant roles in Cdk1 inhibitory phosphorylation, Wee1 and Myt1 serve specialized developmental functions that are not well understood. Here, we expressed wild-type and phospho-acceptor mutant Cdk1 proteins to investigate how biochemical differences in Cdk1 inhibitory phosphorylation influence Drosophila imaginal development. Phosphorylation of Cdk1 on Y15 appeared to be crucial for developmental and DNA damage-induced G2-phase checkpoint arrest, consistent with other evidence that Myt1 is the major Y15-directed Cdk1 inhibitory kinase at this stage of development. Expression of non-inhibitable Cdk1 also caused chromosome defects in larval neuroblasts that were not observed with Cdk1(Y15F) mutant proteins that were phosphorylated on T14, implicating Myt1 in a novel mechanism promoting genome stability. Collectively, these results suggest that dual inhibitory phosphorylation of Cdk1 by Myt1 serves at least two functions during development. Phosphorylation of Y15 is essential for the premitotic checkpoint mechanism, whereas T14 phosphorylation facilitates accumulation of dually inhibited Cdk1-Cyclin B complexes that can be rapidly activated once checkpoint-arrested G2-phase cells are ready for mitosis.
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Local circadian clock gates cell cycle progression of transient amplifying cells during regenerative hair cycling. Proc Natl Acad Sci U S A 2013; 110:E2106-15. [PMID: 23690597 DOI: 10.1073/pnas.1215935110] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Regenerative cycling of hair follicles offers an unique opportunity to explore the role of circadian clock in physiological tissue regeneration. We focused on the role of circadian clock in actively proliferating transient amplifying cells, as opposed to quiescent stem cells. We identified two key sites of peripheral circadian clock activity specific to regenerating anagen hair follicles, namely epithelial matrix and mesenchymal dermal papilla. We showed that peripheral circadian clock in epithelial matrix cells generates prominent daily mitotic rhythm. As a consequence of this mitotic rhythmicity, hairs grow faster in the morning than in the evening. Because cells are the most susceptible to DNA damage during mitosis, this cycle leads to a remarkable time-of-day-dependent sensitivity of growing hair follicles to genotoxic stress. Same doses of γ-radiation caused dramatic hair loss in wild-type mice when administered in the morning, during mitotic peak, compared with the evening, when hair loss is minimal. This diurnal radioprotective effect becomes lost in circadian mutants, consistent with asynchronous mitoses in their hair follicles. Clock coordinates cell cycle progression with genotoxic stress responses by synchronizing Cdc2/Cyclin B-mediated G2/M checkpoint. Our results uncover diurnal mitotic gating as the essential protective mechanism in highly proliferative hair follicles and offer strategies for minimizing or maximizing cytotoxicity of radiation therapies.
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Creevey L, Ryan J, Harvey H, Bray IM, Meehan M, Khan AR, Stallings RL. MicroRNA-497 increases apoptosis in MYCN amplified neuroblastoma cells by targeting the key cell cycle regulator WEE1. Mol Cancer 2013; 12:23. [PMID: 23531080 PMCID: PMC3626575 DOI: 10.1186/1476-4598-12-23] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 03/17/2013] [Indexed: 12/16/2022] Open
Abstract
Background Neuroblastoma is responsible for 15% of all childhood cancer deaths. Despite advances in treatment and disease management, the overall 5-year survival rates remain poor in high-risk disease (25-40%). MiR-497 was previously identified by our laboratory as a member of a miRNA expression signature, predictive of neuroblastoma patient survival and has been reported as a tumor suppressor in a variety of other cancers. WEE1, a tyrosine kinase regulator of the cell cycle and predicted target of miR-497, has emerged as an oncogene in several cancer types and therefore represents an attractive potential target for novel therapy approaches in high-risk neuroblastoma. Our aim was to investigate the potential tumor suppressive role of miR-497 in high-risk neuroblastoma. Methods Expression levels of miR-497 and WEE1 in tissues and cells were determined using RT-PCR. The effect of miR-497 and siWEE1 on cell viability was evaluated using MTS assays, apoptosis levels were determined using FACS analysis of Annexin V/PI stained cells, and target protein expression was determined using western blot. Luciferase reporter plasmids were constructed to confirm direct targeting. Results were reported as mean±S.E.M and differences were tested for significance using 2-tailed Students t-test. Results We determined that miR-497 expression was significantly lower in high-risk MYCN amplified (MNA) tumors and that low miR-497 expression was associated with worse EFS and OS in our cohort. Over-expression of miR-497 reduced cell viability and increased apoptosis in MNA cells. We identified WEE1 as a novel target for miR-497 in neuroblastoma. Furthermore, our analysis showed that high WEE1 levels are significantly associated with poor EFS and OS in neuroblastoma and that siRNA knockdown of WEE1 in MNA cell lines results in significant levels of apoptosis, supporting an oncogenic role of WEE1 in neuroblastoma. Cisplatin (CDDP) treatment of both miR-497 over-expressing cells and WEE1 inhibited cells, resulted in a significant increase in apoptosis in MNA cells, describing a synergistic effect and therefore a potential therapeutic for high-risk neuroblastoma. Conclusion Our study’s results are consistent with miR-497 being a candidate tumor suppressor in neuroblastoma, through the direct targeting of WEE1. These findings re-enforce the proposal of WEE1 as a therapeutic target in neuroblastoma.
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Affiliation(s)
- Laura Creevey
- Department of Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, York House, York Street, Dublin 2, Ireland
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35
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Number of nuclear divisions in the Drosophila blastoderm controlled by onset of zygotic transcription. Curr Biol 2013; 23:133-8. [PMID: 23290555 DOI: 10.1016/j.cub.2012.12.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 11/25/2012] [Accepted: 12/10/2012] [Indexed: 01/10/2023]
Abstract
The cell number of the early Drosophila embryo is determined by exactly 13 rounds of synchronous nuclear divisions, allowing cellularization and formation of the embryonic epithelium. The pause in G2 in cycle 14 is controlled by multiple pathways, such as activation of DNA repair checkpoint, progression through S phase, and inhibitory phosphorylation of Cdk1, involving the genes grapes, mei41, and wee1. In addition, degradation of maternal RNAs and zygotic gene expression are involved. The zinc finger Vielfältig (Vfl) controls expression of many early zygotic genes, including the mitotic inhibitor frühstart. The functional relationship of these pathways and the mechanism for triggering the cell-cycle pause have remained unclear. Here, we show that a novel single-nucleotide mutation in the 3' UTR of the RNPII215 gene leads to a reduced number of nuclear divisions that is accompanied by premature transcription of early zygotic genes and cellularization. The reduced number of nuclear divisions in mutant embryos depends on the transcription factor Vfl and on zygotic gene expression, but not on grapes, the mitotic inhibitor Frühstart, and the nucleocytoplasmic ratio. We propose that activation of zygotic gene expression is the trigger that determines the timely and concerted cell-cycle pause and cellularization.
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36
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Di Talia S, She R, Blythe SA, Lu X, Zhang QF, Wieschaus EF. Posttranslational control of Cdc25 degradation terminates Drosophila's early cell-cycle program. Curr Biol 2013; 23:127-32. [PMID: 23290553 DOI: 10.1016/j.cub.2012.11.029] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 11/05/2012] [Accepted: 11/12/2012] [Indexed: 11/30/2022]
Abstract
In most metazoans, early embryonic development is characterized by rapid mitotic divisions that are controlled by maternal mRNAs and proteins that accumulate during oogenesis. These rapid divisions pause at the midblastula transition (MBT), coinciding with a dramatic increase in gene transcription and the degradation of a subset of maternal mRNAs. In Drosophila, the cell-cycle pause is controlled by inhibitory phosphorylation of Cdk1, which in turn is driven by downregulation of the activating Cdc25 phosphatases. Here, we show that the two Drosophila Cdc25 homologs, String and Twine, differ in their dynamics and that, contrary to current models, their downregulations are not controlled by mRNA degradation but through different posttranslational mechanisms. The degradation rate of String protein gradually increases during the late syncytial cycles in a manner dependent on the nuclear-to-cytoplasmic ratio and on the DNA replication checkpoints. Twine, on the other hand, is targeted for degradation at the onset of the MBT through a switch-like mechanism controlled, like String, by the nuclear-to-cytoplasmic ratio, but not requiring the DNA replication checkpoints. We demonstrate that posttranslational control of Twine degradation ensures that the proper number of mitoses precede the MBT.
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Affiliation(s)
- Stefano Di Talia
- Howard Hughes Medical Institute, Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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Chow JPH, Poon RYC. The CDK1 inhibitory kinase MYT1 in DNA damage checkpoint recovery. Oncogene 2012; 32:4778-88. [PMID: 23146904 DOI: 10.1038/onc.2012.504] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 09/14/2012] [Accepted: 09/18/2012] [Indexed: 02/07/2023]
Abstract
Inhibition of cyclin-dependent kinase 1 (CDK1) by phosphorylation is a key regulatory mechanism for both the unperturbed cell cycle and the DNA damage checkpoint. Although both WEE1 and MYT1 can phosphorylate CDK1, little is known about the contribution of MYT1. We found that in contrast to WEE1, MYT1 was not important for the normal cell cycle or checkpoint activation. Time-lapse microscopy indicated that MYT1 did, however, have a rate-determining role during checkpoint recovery. Depletion of MYT1 induced precocious mitotic entry when the checkpoint was abrogated with inhibitors of either CHK1 or WEE1, indicating that MYT1 contributes to checkpoint recovery independently of WEE1. The acceleration of checkpoint recovery in MYT1-depleted cells was due to a lowering of threshold for CDK1 activation. The kinase activity of MYT1 was high during checkpoint activation and reduced during checkpoint recovery. Importantly, although depletion of MYT1 alone did not affect long-term cell growth, it potentiated with DNA damage to inhibit cell growth in clonogenic survival and tumor xenograft models. These results reveal the functions of MYT1 in checkpoint recovery and highlight the potential of MYT1 as a target for anti-cancer therapies.
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Affiliation(s)
- J P H Chow
- Division of Life Science and Center for Cancer Research, Hong Kong University of Science and Technology, Kowloon, Hong Kong
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Carrassa L, Chilà R, Lupi M, Ricci F, Celenza C, Mazzoletti M, Broggini M, Damia G. Combined inhibition of Chk1 and Wee1: in vitro synergistic effect translates to tumor growth inhibition in vivo. Cell Cycle 2012; 11:2507-17. [PMID: 22713237 DOI: 10.4161/cc.20899] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Targeting Chk1 protein kinase can enhance the antitumor effects of radio- and chemotherapy. Recent evidence disclosed a role of Chk1 in unperturbed cell proliferation and survival, implying that Chk1 inhibitors could also be effective as single agents in tumors with a specific genetic background. To identify genes in synthetic lethality with Chk1, we did a high-throughput screening using a siRNA library directed against 719 human protein kinases in the human ovarian cancer cell line OVCAR-5, resistant to Chk1 inhibitors. Wee1 tyrosine kinase was the most significant gene in synthetic lethality with Chk1. Treatment with non-toxic concentrations of a Chk1 inhibitor (PF-00477736) and a Wee1 inhibitor (MK-1775) confirmed the marked synergistic effect in various human cancer cell lines (breast, ovarian, colon, prostate), independently of the p53 status. Detailed molecular analysis showed that the combination caused cancer cells to undergo premature mitosis before the end of DNA replication, with damaged DNA leading to cell death partly by apoptosis. In vivo treatment of mice bearing OVCAR-5 xenografts with the combination of Chk1 and Wee1 inhibitors led to greater tumor growth inhibition than with the inhibitors used as single agents with no toxicity. These data provide a strong rationale for the clinical investigation of the combination of a Chk1 and a Wee1 inhibitor.
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Affiliation(s)
- Laura Carrassa
- Laboratory of Molecular Pharmacology, Department of Oncology, Istituto di Ricerche Farmacologiche "Mario Negri", Milan, Italy.
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Zeng GH, Wu WJ, Zhang R, Sun J, Xie WG, Shen Y. 3D-QSAR and Docking Studies of Pyrido[2,3-d]pyrimidine Derivatives as Wee1 Inhibitors. CHINESE J CHEM PHYS 2012. [DOI: 10.1088/1674-0068/25/03/297-307] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Dráber P, Sulimenko V, Dráberová E. Cytoskeleton in mast cell signaling. Front Immunol 2012; 3:130. [PMID: 22654883 PMCID: PMC3360219 DOI: 10.3389/fimmu.2012.00130] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2012] [Accepted: 05/05/2012] [Indexed: 11/13/2022] Open
Abstract
Mast cell activation mediated by the high affinity receptor for IgE (FcεRI) is a key event in allergic response and inflammation. Other receptors on mast cells, as c-Kit for stem cell factor and G protein-coupled receptors (GPCRs) synergistically enhance the FcεRI-mediated release of inflammatory mediators. Activation of various signaling pathways in mast cells results in changes in cell morphology, adhesion to substrate, exocytosis, and migration. Reorganization of cytoskeleton is pivotal in all these processes. Cytoskeletal proteins also play an important role in initial stages of FcεRI and other surface receptors induced triggering. Highly dynamic microtubules formed by αβ-tubulin dimers as well as microfilaments build up from polymerized actin are affected in activated cells by kinases/phosphatases, Rho GTPases and changes in concentration of cytosolic Ca(2+). Also important are nucleation proteins; the γ-tubulin complexes in case of microtubules or Arp 2/3 complex with its nucleation promoting factors and formins in case of microfilaments. The dynamic nature of microtubules and microfilaments in activated cells depends on many associated/regulatory proteins. Changes in rigidity of activated mast cells reflect changes in intermediate filaments build up from vimentin. This review offers a critical appraisal of current knowledge on the role of cytoskeleton in mast cells signaling.
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Affiliation(s)
- Pavel Dráber
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech RepublicPrague, Czech Republic
| | - Vadym Sulimenko
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech RepublicPrague, Czech Republic
| | - Eduarda Dráberová
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech RepublicPrague, Czech Republic
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Hong KS, Kim HS, Kim SH, Lim DJ, Park JY, Kim SD. Hypoxia induces Wee1 expression and attenuates hydrogen peroxide-induced endothelial damage in MS1 cells. Exp Mol Med 2012; 43:653-9. [PMID: 21918363 DOI: 10.3858/emm.2011.43.12.074] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
In an oxygen-depleted environment, endothelial cells initiate an adaptive pattern of synthesis, which may enable them to survive hypoxic crises. Using high-resolution two-dimensional gel electrophoresis in conjunction with mass spectroscopy, we obtained a 24 differential display of proteins in the pancreatic endothelial cell line, MS-1, at four time points following induction of hypoxia. The induction of Wee1 under hypoxia was confirmed both at the mRNA and protein levels. The phosphorylation of cell division cycle 2, which is downstream of Wee1, was also increased after hypoxic exposure. In addition, pre-exposure to hypoxia attenuated a decrease in hydrogen peroxide-induced cell number. The induction of bax (a pro-apoptotic protein) and reduction of bcl (an anti-apoptotic protein) after hypoxia stimulus were also attenuated by hypoxic pre-exposure. Moreover, hydrogen peroxide-induced morphologic damage did not appear in the wild-type Wee1-expressing cells. Taken together, our results suggest that Wee1 may have important role in hypoxia- induced pathophysiological situations in endothelial cells.
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Affiliation(s)
- Ki Sun Hong
- Department of Neurosurgery Korea University Ansan Hospital Korea University College of Medicine Ansan 425-707, Korea
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Abstract
The duration of S phase in early embryos is often short, and then increases as development proceeds because of the appearance of late-replicating regions of the genome. In the April 1, 2012, issue of Genes & Development, Farrell and colleagues (pp. 714-725) demonstrate that the down-regulation of cyclin-dependent kinase 1 (Cdk1) activity triggers the onset of late-replicating DNA and an increase in S-phase length in Drosophila embryos, revealing an unexpected role for Cdk1 in replication control during development.
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Affiliation(s)
- Robert J Duronio
- Department of Biology, Department of Genetics, Lineberger Comprehensive Cancer Center, Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599, USA.
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Fasulo B, Koyama C, Yu KR, Homola EM, Hsieh TS, Campbell SD, Sullivan W. Chk1 and Wee1 kinases coordinate DNA replication, chromosome condensation, and anaphase entry. Mol Biol Cell 2012; 23:1047-57. [PMID: 22262459 PMCID: PMC3302732 DOI: 10.1091/mbc.e11-10-0832] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
New chromosome condensation checkpoints are identified. S-phase and topoisomerase inhibitors delay chromosome condensation. These delays require chk1 and wee1. Inhibitors causing defects in chromosome condensation/congression on the metaphase plate delay anaphase entry. wee1 and not the spindle assembly checkpoint mediates the delay. Defects in DNA replication and chromosome condensation are common phenotypes in cancer cells. A link between replication and condensation has been established, but little is known about the role of checkpoints in monitoring chromosome condensation. We investigate this function by live analysis, using the rapid division cycles in the early Drosophila embryo. We find that S-phase and topoisomerase inhibitors delay both the initiation and the rate of chromosome condensation. These cell cycle delays are mediated by the cell cycle kinases chk1 and wee1. Inhibitors that cause severe defects in chromosome condensation and congression on the metaphase plate result in delayed anaphase entry. These delays are mediated by wee1 and are not the result of spindle assembly checkpoint activation. In addition, we provide the first detailed live analysis of the direct effect of widely used anticancer agents (aclarubicin, ICRF-193, VM26, doxorubicin, camptothecin, aphidicolin, hydroxyurea, cisplatin, mechlorethamine and x-rays) on key nuclear and cytoplasmic cell cycle events.
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Affiliation(s)
- Barbara Fasulo
- Sinsheimer Laboratories, Department of Molecular, Cellular and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
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Drosophila Xpd regulates Cdk7 localization, mitotic kinase activity, spindle dynamics, and chromosome segregation. PLoS Genet 2010; 6:e1000876. [PMID: 20300654 PMCID: PMC2837399 DOI: 10.1371/journal.pgen.1000876] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Accepted: 02/06/2010] [Indexed: 12/04/2022] Open
Abstract
The trimeric CAK complex functions in cell cycle control by phosphorylating and activating Cdks while TFIIH-linked CAK functions in transcription. CAK also associates into a tetramer with Xpd, and our analysis of young Drosophila embryos that do not require transcription now suggests a cell cycle function for this interaction. xpd is essential for the coordination and rapid progression of the mitotic divisions during the late nuclear division cycles. Lack of Xpd also causes defects in the dynamics of the mitotic spindle and chromosomal instability as seen in the failure to segregate chromosomes properly during ana- and telophase. These defects appear to be also nucleotide excision repair (NER)–independent. In the absence of Xpd, misrouted spindle microtubules attach to chromosomes of neighboring mitotic figures, removing them from their normal location and causing multipolar spindles and aneuploidy. Lack of Xpd also causes changes in the dynamics of subcellular and temporal distribution of the CAK component Cdk7 and local mitotic kinase activity. xpd thus functions normally to re-localize Cdk7(CAK) to different subcellular compartments, apparently removing it from its cell cycle substrate, the mitotic Cdk. This work proves that the multitask protein Xpd also plays an essential role in cell cycle regulation that appears to be independent of transcription or NER. Xpd dynamically localizes Cdk7/CAK to and away from subcellular substrates, thereby controlling local mitotic kinase activity. Possibly through this activity, xpd controls spindle dynamics and chromosome segregation in our model system. This novel role of xpd should also lead to new insights into the understanding of the neurological and cancer aspects of the human XPD disease phenotypes. Mutations in human xpd cause three different syndromes—XP (xeroderma pigmentosum), TTD (trichothiodystrophy), and CS (Cockayne syndrome)—and various different phenotypes, such as sun-induced hyperpigmentation of the skin, cutaneous abnormalities, neuronal degeneration, and developmental retardation. In addition, while some mutations cause a highly elevated cancer risk, others do not. The multitask protein Xpd functions in transcription, nucleotide excision repair (NER), and in cell cycle regulation. In a situation where transcription is not required and NER not induced, we specifically analyzed the cell cycle function of Xpd in Drosophila. In this situation Xpd locally controls the dynamic localization of Cdk7, the catalytic subunit of the Cdk activating kinase (CAK) to and away from its cellular targets, thereby regulating mitotic kinase activity and mitotic exit. Xpd also controls spindle dynamics to prevent formation of multipolar and promiscuous spindles and aneuploidy. Through multitask proteins like Xpd and Cdk7 cells regulate different cellular pathways in a coordinated fashion. In addition to the basic research relevance, the newly gained knowledge about the cell cycle function of Xpd and its control of spindle dynamics is also relevant for human xpd patients because it shows a possible pathway that could lead to highly increased cancer risk and neurological defects.
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Beck H, Nähse V, Larsen MSY, Groth P, Clancy T, Lees M, Jørgensen M, Helleday T, Syljuåsen RG, Sørensen CS. Regulators of cyclin-dependent kinases are crucial for maintaining genome integrity in S phase. ACTA ACUST UNITED AC 2010; 188:629-38. [PMID: 20194642 PMCID: PMC2835936 DOI: 10.1083/jcb.200905059] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
WEE1 and CHK1 jointly regulate Cdk activity to prevent DNA damage during replication. Maintenance of genome integrity is of critical importance to cells. To identify key regulators of genomic integrity, we screened a human cell line with a kinome small interfering RNA library. WEE1, a major regulator of mitotic entry, and CHK1 were among the genes identified. Both kinases are important negative regulators of CDK1 and -2. Strikingly, WEE1 depletion rapidly induced DNA damage in S phase in newly replicated DNA, which was accompanied by a marked increase in single-stranded DNA. This DNA damage is dependent on CDK1 and -2 as well as the replication proteins MCM2 and CDT1 but not CDC25A. Conversely, DNA damage after CHK1 inhibition is highly dependent on CDC25A. Furthermore, the inferior proliferation of CHK1-depleted cells is improved substantially by codepletion of CDC25A. We conclude that the mitotic kinase WEE1 and CHK1 jointly maintain balanced cellular control of Cdk activity during normal DNA replication, which is crucial to prevent the generation of harmful DNA lesions during replication.
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Affiliation(s)
- Halfdan Beck
- Biotech Research and Innovation Centre, University of Copenhagen, 2200 Copenhagen N, Denmark
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Beck SA, Falconer E, Catching A, Hodgson JW, Brock HW. Cell cycle defects in polyhomeotic mutants are caused by abrogation of the DNA damage checkpoint. Dev Biol 2010; 339:320-8. [PMID: 20045683 DOI: 10.1016/j.ydbio.2009.12.031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 10/30/2009] [Accepted: 12/19/2009] [Indexed: 12/31/2022]
Abstract
Polycomb group (PcG) genes are required for heritable silencing of target genes. Many PcG mutants have chromatin bridges and other mitotic defects in early embryos. These phenotypes can arise from defects in S phase or mitosis, so the phenotype does not show when PcG proteins act in cell cycle regulation. We analyzed the cell cycle role of the proximal subunit of Polyhomeotic (PhP) in Drosophila. Time-lapse imaging reveals that chromatin bridges formed during mitosis are able to resolve but sometimes result in chromosome breakage. Chromosome bridging is also observed in canonical cell cycles occurring in larval brains and is therefore not unique to the rapid embryonic cycles. PhP colocalizes with chromatin in S phase but not in mitosis in early embryos, indicating a direct role in DNA synthesis. Time lapse imaging of ph(p) mutants reveals an acceleration of S phase, showing that ph(p) regulates S phase length. Like ph(p) mutations, mutations in DNA damage checkpoints result in S phase acceleration. Consistent with this model, mutations in ph do not affect DNA synthesis rates, but exhibit impaired ability to block cell cycle progression following exposure to gamma-rays. Our data show that the mitotic defects of ph(p) are caused by defects in the DNA damage response that occurs after DNA replication in S phase, and we propose that PhP has a direct role in DNA damage repair.
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Affiliation(s)
- Samantha A Beck
- Molecular Epigenetics Group, Department of Zoology, University of BC, Life Sciences Centre, 2350 Health Sciences Mall Vancouver, BC, Canada V6T 1Z3
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Abstract
Kinesin-5s help assemble the bipolar spindle by crosslinking and sliding apart antiparallel microtubules. A recent study has uncovered a novel pathway for the phospho-regulation of these motors.
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Affiliation(s)
- David J Sharp
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Tyrosines in the kinesin-5 head domain are necessary for phosphorylation by Wee1 and for mitotic spindle integrity. Curr Biol 2009; 19:1670-6. [PMID: 19800237 DOI: 10.1016/j.cub.2009.08.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Revised: 08/05/2009] [Accepted: 08/07/2009] [Indexed: 11/23/2022]
Abstract
Mitotic spindle assembly and maintenance relies on kinesin-5 motors that act as bipolar homotetramers to crosslink microtubules. Kinesin-5 motors have been the subject of extensive structure-function analysis, but the regulation of their activity in the context of mitotic progression remains less well understood. We report here that Drosophila kinesin-5 (KLP61F) is regulated by Drosophila Wee1 (dWee1). Wee1 tyrosine kinases are known to regulate mitotic entry via inhibitory phosphorylation of Cdk1. Recently, we showed that dWee1 also plays a role in mitotic spindle positioning through gamma-tubulin and spindle fidelity through an unknown mechanism. Here, we investigated whether a KLP61F-dWee1 interaction could explain the latter role of dWee1. We found that dWee1 phosphorylates KLP61F in vitro on three tyrosines within the head domain, the catalytic region that mediates movement along microtubules. In vivo, KLP61F with tyrosine-->phenylalanine mutations fails to complement a klp61f mutant and dominantly induces spindle defects similar to ones seen in dwee1 mutants. We propose that phosphorylation of the KLP61F catalytic domain by dWee1 is important for the motor's function. This study identifies a second substrate for a Wee1 kinase and provides evidence for phosphoregulation of a kinesin in the head domain.
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McCleland ML, Shermoen AW, O'Farrell PH. DNA replication times the cell cycle and contributes to the mid-blastula transition in Drosophila embryos. ACTA ACUST UNITED AC 2009; 187:7-14. [PMID: 19786576 PMCID: PMC2762091 DOI: 10.1083/jcb.200906191] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Deletion of S phase disrupts mitotic timing in maternally regulated cycles, but it doesn't alter the cell cycle once zygotic transcription has begun. We examined the contribution of S phase in timing cell cycle progression during Drosophila embryogenesis using an approach that deletes S phase rather than arresting its progress. Injection of Drosophila Geminin, an inhibitor of replication licensing, prevented subsequent replication so that the following mitosis occurred with uninemic chromosomes, which failed to align. The effect of S phase deletion on interphase length changed with development. During the maternally regulated syncytial blastoderm cycles, deleting S phase shortened interphase, and deletion of the last of blastoderm S phase (cycle 14) induced an extra synchronous division and temporarily deferred mid-blastula transition (MBT) events. In contrast, deleting S phase after the MBT in cycle 15 did not dramatically affect mitotic timing, which appears to retain its dependence on developmentally programmed zygotic transcription. We conclude that normal S phase and replication checkpoint activities are important timers of the undisturbed cell cycle before, but not after, the MBT.
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Affiliation(s)
- Mark L McCleland
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA
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Ninov N, Manjón C, Martín-Blanco E. Dynamic control of cell cycle and growth coupling by ecdysone, EGFR, and PI3K signaling in Drosophila histoblasts. PLoS Biol 2009; 7:e1000079. [PMID: 19355788 PMCID: PMC2672598 DOI: 10.1371/journal.pbio.1000079] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Accepted: 02/20/2009] [Indexed: 11/19/2022] Open
Abstract
Regulation of cell proliferation has been extensively studied in cultured cell systems that are characterized by coordinated growth and cell-cycle progression and relatively uniform cell size distribution. During the development of multicellular organisms, however, growth and division can be temporally uncoupled, and the signaling pathways that regulate these growth programs are poorly understood. A good model for analyzing proliferation control in such systems is the morphogenesis of the Drosophila adult abdominal epidermis by histoblasts. These cells undergo a series of temporally regulated transitions during which neither cell size nor division rate is constant. The proliferation of histoblasts during metamorphosis is uniquely amenable to clonal analysis in combination with live imaging. Thereby, we show that abdominal histoblasts, which grow while in G2 arrest during larval stages, enter a proliferative stage in the pupal period that is initiated by ecdysone-dependent string/Cdc25 phosphatase transcription. The proliferating histoblasts have preaccumulated stores of Cyclin E, which trigger an immediate S phase onset after mitosis. These rapid cell cycles lack a G1 phase and result in a progressive reduction of cell size. Eventually, the histoblasts proceed to a stage of slower proliferation that, in contrast to the preceding, depends on epidermal growth factor receptor (EGFR) signaling for progression through the G2/M transition and on insulin receptor/PI3K-mediated signaling for growth. These results uncover the developmentally programmed changes coupling the growth and proliferation of the histoblasts that form the abdominal epidermis of Drosophila. Histoblasts proceed through three distinct stages: growth without division, division without growth, and growth-coupled proliferation. Our identification of the signaling pathways and cell-cycle regulators that control these programs illustrates the power of in vivo time-lapse analyses after clone induction. It sets the stage for the comprehensive understanding of the coordination of cell growth and cell-cycle progression in complex multicellular eukaryotes. A fundamental issue in biology is the question of how the rate of cell division is coupled to cell growth. Coordination of these processes has been studied extensively in cultured cell systems but to a much lesser extent in intact organisms. To study this phenomenon in a physiological setting, we developed a methodology to observe and manipulate cell division and growth in a population of Drosophila abdominal cells called histoblasts. The various developmental stages of histoblast morphogenesis include exit from cell-cycle arrest, initially rapid growth in the absence of cell division, and subsequent coupling of proliferation and growth. We identified several critical developmental signaling pathways (including signaling via ecdysone, the EGF receptor, and PI 3-kinase) that regulate and coordinate cell growth and division cycles during these different types of cell-cycle phenomena. We propose that the internal logic of the Drosophila histoblast system may serve as a basic framework for understanding not only how coordinated cell growth and division operate in a number of other developmental contexts, but also how misregulation of cell growth and division occurs in contexts such as cancer cell populations. Integration of the ecdysone, EGF receptor, and PI 3-kinase signaling pathways determines the relative rates of growth and cell division duringDrosophila abdominal cell morphogenesis.
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