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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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2
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Zhang Q, Lin X, Jiang K, Deng J, Ke L, Wu Z, Xia P, Li Q, Yu L, Ni P, Lv W, Hu J. PD0166285 sensitizes esophageal squamous cell carcinoma to radiotherapy by dual inhibition of WEE1 and PKMYT1. Front Oncol 2022. [DOI: 10.3389/fonc.2022.1061988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BackgroundEsophageal squamous cell carcinoma (ESCC) is an aggressive tumor with a 5-year survival rate of only 20%. More than 80% of ESCC patients possess TP53 mutation, which abolishes the G1/S checkpoint and accelerates the cell cycle. Thus, WEE1 and PKMYT1, regulators of G2/M phase in cell cycle, play essential roles in TP53-mutated cancer cells. PD0166285(PD) is a pyridopyrimidine compound that can inhibit WEE1 and PKMYT1 simultaneously, however, the effects of PD on ESCC, either as monotherapy or in combination therapy with radiotherapy, remain unclear.MethodsTo measure the anti-tumor efficacy of PD in ESCC cells, cell viability, cell cycle and cell apoptosis assays were examined in KYSE150 and TE1 cells with PD treatment. The combination therapy of PD and irradiation was also performed in ESCC cells to find whether PD can sensitize ESCC cells to irradiation. Vivo assays were also performed to investigate the efficacy of PD.ResultsWe found that the IC50 values of PD among ESCC cells ranged from 234 to 694 nM, PD can regulate cell cycle and induce cell apoptosis in ESCC cells in a dose-dependent manner. When combined with irradiation, PD sensitized ESCC cells to irradiation by abolishing G2/M phase arrest, inducing a high ratio of mitosis catastrophe, eventually leading to cell death. We also demonstrated that PD can attenuate DNA damage repair by inhibiting Rad51, further research also found the interaction of WEE1 and Rad51. In vivo assays, PD inhibited the tumor growth in mice, combination therapy showed better therapeutic efficacy.ConclusionPD0166285 can exert antitumor effect by inhibiting the function of WEE1 and PKMYT1 in ESCC cells, and also sensitize ESCC cells to irradiation not only by abolishing G2/M arrest but also attenuating DNA repair directly. We believe PD0166285 can be a potent treatment option for ESCC in the future.
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Baonza A, Tur-Gracia S, Pérez-Aguilera M, Estella C. Regulation and coordination of the different DNA damage responses in Drosophila. Front Cell Dev Biol 2022; 10:993257. [PMID: 36147740 PMCID: PMC9486394 DOI: 10.3389/fcell.2022.993257] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 08/10/2022] [Indexed: 11/17/2022] Open
Abstract
Cells have evolved mechanisms that allow them to respond to DNA damage to preserve genomic integrity and maintain tissue homeostasis. These responses include the activation of the cell cycle checkpoints and the repair mechanisms or the induction of apoptosis that eventually will eliminate damaged cells. These “life” vs. “death” decisions differ depending on the cell type, stages of development, and the proliferation status of the cell. The apoptotic response after DNA damage is of special interest as defects in its induction could contribute to tumorigenesis or the resistance of cancer cells to therapeutic agents such as radiotherapy. Multiples studies have elucidated the molecular mechanisms that mediate the activation of the DNA damage response pathway (DDR) and specifically the role of p53. However, much less is known about how the different cellular responses such as cell proliferation control and apoptosis are coordinated to maintain tissue homeostasis. Another interesting question is how the differential apoptotic response to DNA damage is regulated in distinct cell types. The use of Drosophila melanogaster as a model organism has been fundamental to understand the molecular and cellular mechanisms triggered by genotoxic stress. Here, we review the current knowledge regarding the cellular responses to ionizing radiation as the cause of DNA damage with special attention to apoptosis in Drosophila: how these responses are regulated and coordinated in different cellular contexts and in different tissues. The existence of intrinsic mechanisms that might attenuate the apoptotic pathway in response to this sort of DNA damage may well be informative for the differences in the clinical responsiveness of tumor cells after radiation therapy.
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Coordination between cell proliferation and apoptosis after DNA damage in Drosophila. Cell Death Differ 2022; 29:832-845. [PMID: 34824391 PMCID: PMC8989919 DOI: 10.1038/s41418-021-00898-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 11/03/2021] [Accepted: 11/08/2021] [Indexed: 12/31/2022] Open
Abstract
Exposure to genotoxic stress promotes cell cycle arrest and DNA repair or apoptosis. These "life" or "death" cell fate decisions often rely on the activity of the tumor suppressor gene p53. Therefore, the precise regulation of p53 is essential to maintain tissue homeostasis and to prevent cancer development. However, how cell cycle progression has an impact on p53 cell fate decision-making is mostly unknown. In this work, we demonstrate that Drosophila p53 proapoptotic activity can be impacted by the G2/M kinase Cdk1. We find that cell cycle arrested or endocycle-induced cells are refractory to ionizing radiation-induced apoptosis. We show that p53 binding to the regulatory elements of the proapoptotic genes and its ability to activate their expression is compromised in experimentally arrested cells. Our results indicate that p53 genetically and physically interacts with Cdk1 and that p53 proapoptotic role is regulated by the cell cycle status of the cell. We propose a model in which cell cycle progression and p53 proapoptotic activity are molecularly connected to coordinate the appropriate response after DNA damage.
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5
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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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6
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Lewis CW, Bukhari AB, Xiao EJ, Choi WS, Smith JD, Homola E, Mackey JR, Campbell SD, Gamper AM, Chan GK. Upregulation of Myt1 Promotes Acquired Resistance of Cancer Cells to Wee1 Inhibition. Cancer Res 2019; 79:5971-5985. [PMID: 31594837 DOI: 10.1158/0008-5472.can-19-1961] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 09/04/2019] [Accepted: 10/04/2019] [Indexed: 11/16/2022]
Abstract
Adavosertib (also known as AZD1775 or MK1775) is a small-molecule inhibitor of the protein kinase Wee1, with single-agent activity in multiple solid tumors, including sarcoma, glioblastoma, and head and neck cancer. Adavosertib also shows promising results in combination with genotoxic agents such as ionizing radiation or chemotherapy. Previous studies have investigated molecular mechanisms of primary resistance to Wee1 inhibition. Here, we investigated mechanisms of acquired resistance to Wee1 inhibition, focusing on the role of the Wee1-related kinase Myt1. Myt1 and Wee1 kinases were both capable of phosphorylating and inhibiting Cdk1/cyclin B, the key enzymatic complex required for mitosis, demonstrating their functional redundancy. Ectopic activation of Cdk1 induced aberrant mitosis and cell death by mitotic catastrophe. Cancer cells with intrinsic adavosertib resistance had higher levels of Myt1 compared with sensitive cells. Furthermore, cancer cells that acquired resistance following short-term adavosertib treatment had higher levels of Myt1 compared with mock-treated cells. Downregulating Myt1 enhanced ectopic Cdk1 activity and restored sensitivity to adavosertib. These data demonstrate that upregulating Myt1 is a mechanism by which cancer cells acquire resistance to adavosertib. SIGNIFICANCE: Myt1 is a candidate predictive biomarker of acquired resistance to the Wee1 kinase inhibitor adavosertib.
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Affiliation(s)
- Cody W Lewis
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada
| | - Amirali B Bukhari
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada
| | - Edric J Xiao
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada
| | - Won-Shik Choi
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada
| | - Joanne D Smith
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada
| | - Ellen Homola
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - John R Mackey
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.,Medical Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada
| | - Shelagh D Campbell
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Armin M Gamper
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada
| | - Gordon K Chan
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada. .,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada
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7
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Gerlach SU, Sander M, Song S, Herranz H. The miRNA bantam regulates growth and tumorigenesis by repressing the cell cycle regulator tribbles. Life Sci Alliance 2019; 2:2/4/e201900381. [PMID: 31331981 PMCID: PMC6653758 DOI: 10.26508/lsa.201900381] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 07/15/2019] [Accepted: 07/15/2019] [Indexed: 12/15/2022] Open
Abstract
This work identifies the cell cycle regulator tribbles as a target of the miRNA bantam involved in the growth regulatory and oncogenic functions of bantam in Drosophila epithelia. One of the fundamental issues in biology is understanding how organ size is controlled. Tissue growth has to be carefully regulated to generate well-functioning organs, and defects in growth control can result in tumor formation. The Hippo signaling pathway is a universal growth regulator and has been implicated in cancer. In Drosophila, the Hippo pathway acts through the miRNA bantam to regulate cell proliferation and apoptosis. Even though the bantam targets regulating apoptosis have been determined, the target genes controlling proliferation have not been identified thus far. In this study, we identify the gene tribbles as a direct bantam target gene. Tribbles limits cell proliferation by suppressing G2/M transition. We show that tribbles regulation by bantam is central in controlling tissue growth and tumorigenesis. We expand our study to other cell cycle regulators and show that deregulated G2/M transition can collaborate with oncogene activation driving tumor formation.
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Affiliation(s)
- Stephan U Gerlach
- Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Moritz Sander
- Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Shilin Song
- Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Héctor Herranz
- Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark
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8
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Zhu JY, Cuellar RA, Berndt N, Lee HE, Olesen SH, Martin MP, Jensen JT, Georg GI, Schönbrunn E. Structural Basis of Wee Kinases Functionality and Inactivation by Diverse Small Molecule Inhibitors. J Med Chem 2017; 60:7863-7875. [PMID: 28792760 PMCID: PMC6200136 DOI: 10.1021/acs.jmedchem.7b00996] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Members of the Wee family of kinases negatively regulate the cell cycle via phosphorylation of CDK1 and are considered potential drug targets. Herein, we investigated the structure-function relationship of human Wee1, Wee2, and Myt1 (PKMYT1). Purified recombinant full-length proteins and kinase domain constructs differed substantially in phosphorylation states and catalytic competency, suggesting complex mechanisms of activation. A series of crystal structures reveal unique features that distinguish Wee1 and Wee2 from Myt1 and establish the structural basis of differential inhibition by the widely used Wee1 inhibitor MK-1775. Kinome profiling and cellular studies demonstrate that, in addition to Wee1 and Wee2, MK-1775 is an equally potent inhibitor of the polo-like kinase PLK1. Several previously unrecognized inhibitors of Wee kinases were discovered and characterized. Combined, the data provide a comprehensive view on the catalytic and structural properties of Wee kinases and a framework for the rational design of novel inhibitors thereof.
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Affiliation(s)
- Jin-Yi Zhu
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida 33612, United States
| | - Rebecca A. Cuellar
- Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota 55414, United States
| | - Norbert Berndt
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida 33612, United States
| | - Hee Eun Lee
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida 33612, United States
| | - Sanne H. Olesen
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida 33612, United States
| | - Mathew P. Martin
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida 33612, United States
| | - Jeffrey T. Jensen
- Division of Reproductive and Developmental Science, Oregon National Primate Research Center, Beaverton, Oregon 97006, United States
| | - Gunda I. Georg
- Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota 55414, United States
| | - Ernst Schönbrunn
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida 33612, United States
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9
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Lewis CW, Jin Z, Macdonald D, Wei W, Qian XJ, Choi WS, He R, Sun X, Chan G. Prolonged mitotic arrest induced by Wee1 inhibition sensitizes breast cancer cells to paclitaxel. Oncotarget 2017; 8:73705-73722. [PMID: 29088738 PMCID: PMC5650293 DOI: 10.18632/oncotarget.17848] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 04/27/2017] [Indexed: 11/25/2022] Open
Abstract
Wee1 kinase is a crucial negative regulator of Cdk1/cyclin B1 activity and is required for normal entry into and exit from mitosis. Wee1 activity can be chemically inhibited by the small molecule MK-1775, which is currently being tested in phase I/II clinical trials in combination with other anti-cancer drugs. MK-1775 promotes cancer cells to bypass the cell-cycle checkpoints and prematurely enter mitosis. In our study, we show premature mitotic cells that arise from MK-1775 treatment exhibited centromere fragmentation, a morphological feature of mitotic catastrophe that is characterized by centromeres and kinetochore proteins that co-cluster away from the condensed chromosomes. In addition to stimulating early mitotic entry, MK-1775 treatment also delayed mitotic exit. Specifically, cells treated with MK-1775 following release from G1/S or prometaphase arrested in mitosis. MK-1775 induced arrest occurred at metaphase and thus, cells required 12 times longer to transition into anaphase compared to controls. Consistent with an arrest in mitosis, MK-1775 treated prometaphase cells maintained high cyclin B1 and low phospho-tyrosine 15 Cdk1. Importantly, MK-1775 induced mitotic arrest resulted in cell death regardless the of cell-cycle phase prior to treatment suggesting that Wee1 inhibitors are also anti-mitotic agents. We found that paclitaxel enhances MK-1775 mediated cell killing. HeLa and different breast cancer cell lines (T-47D, MCF7, MDA-MB-468 and MDA-MB-231) treated with different concentrations of MK-1775 and low dose paclitaxel exhibited reduced cell survival compared to mono-treatments. Our data highlight a new potential strategy for enhancing MK-1775 mediated cell killing in breast cancer cells.
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Affiliation(s)
- Cody W Lewis
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada T6G 1Z2.,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada T6G 1Z2.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada T6G 2J7
| | - Zhigang Jin
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada T6G 1Z2.,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada T6G 1Z2.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada T6G 2J7
| | - Dawn Macdonald
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada T6G 1Z2.,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada T6G 1Z2.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada T6G 2J7
| | - Wenya Wei
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada T6G 1Z2
| | - Xu Jing Qian
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada T6G 1Z2
| | - Won Shik Choi
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada T6G 1Z2
| | - Ruicen He
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada T6G 1Z2
| | - Xuejun Sun
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada T6G 1Z2.,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada T6G 1Z2.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada T6G 2J7
| | - Gordon Chan
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada T6G 1Z2.,Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada T6G 1Z2.,Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, Alberta, Canada T6G 2J7
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10
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Ibar C, Glavic Á. Drosophila p115 is required for Cdk1 activation and G2/M cell cycle transition. Mech Dev 2017; 144:191-200. [PMID: 28396045 DOI: 10.1016/j.mod.2017.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 03/28/2017] [Accepted: 04/07/2017] [Indexed: 11/25/2022]
Abstract
Golgi complex inheritance and its relationship with the cell cycle are central in cell biology. Golgi matrix proteins, known as golgins, are one of the components that underlie the shape and functionality of this organelle. In mammalian cells, golgins are phosphorylated during mitosis to allow fragmentation of the Golgi ribbon and they also participate in spindle dynamics; both processes are required for cell cycle progression. Little is known about the function of golgins during mitosis in metazoans in vivo. This is particularly significant in Drosophila, in which the Golgi architecture is distributed in numerous units scattered throughout the cytoplasm, in contrast with mammalian cells. We examined the function of the ER/cis-Golgi golgin p115 during the proliferative phase of the Drosophila wing imaginal disc. Knockdown of p115 decreased tissue size. This phenotype was not caused by programmed cell death or cell size reductions, but by a reduction in the final cell number due to an accumulation of cells at the G2/M transition. This phenomenon frequently allows mitotic bypass and re-replication of DNA. These outcomes are similar to those observed following the partial loss of function of positive regulators of Cdk1 in Drosophila. In agreement with this, Cdk1 activation was reduced upon p115 knockdown. Interestingly, these phenotypes were fully rescued by Cdk1 overexpression and partially rescued by Myt1 depletion, but not by String (also known as Cdc25) overexpression. Additionally, we confirmed the physical interaction between p115 and Cdk1, suggesting that the formation of a complex where both proteins are present is essential for the full activation of Cdk1 and thus the correct progression of mitosis in proliferating tissues.
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Affiliation(s)
- Consuelo Ibar
- FONDAP Center for Genome Regulation, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile.
| | - Álvaro Glavic
- FONDAP Center for Genome Regulation, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile.
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11
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Hunter GL, Hadjivasiliou Z, Bonin H, He L, Perrimon N, Charras G, Baum B. Coordinated control of Notch/Delta signalling and cell cycle progression drives lateral inhibition-mediated tissue patterning. Development 2016; 143:2305-10. [PMID: 27226324 PMCID: PMC4958321 DOI: 10.1242/dev.134213] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 05/10/2016] [Indexed: 01/07/2023]
Abstract
Coordinating cell differentiation with cell growth and division is crucial for the successful development, homeostasis and regeneration of multicellular tissues. Here, we use bristle patterning in the fly notum as a model system to explore the regulatory and functional coupling of cell cycle progression and cell fate decision-making. The pattern of bristles and intervening epithelial cells (ECs) becomes established through Notch-mediated lateral inhibition during G2 phase of the cell cycle, as neighbouring cells physically interact with each other via lateral contacts and/or basal protrusions. Since Notch signalling controls cell division timing downstream of Cdc25, ECs in lateral contact with a Delta-expressing cell experience higher levels of Notch signalling and divide first, followed by more distant neighbours, and lastly Delta-expressing cells. Conversely, mitotic entry and cell division makes ECs refractory to lateral inhibition signalling, fixing their fate. Using a combination of experiments and computational modelling, we show that this reciprocal relationship between Notch signalling and cell cycle progression acts like a developmental clock, providing a delimited window of time during which cells decide their fate, ensuring efficient and orderly bristle patterning. Summary: In the fly notum, a reciprocal relationship between Notch signalling and cell cycle progression acts like a clock, providing a delimited window of time during which cells decide their fate.
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Affiliation(s)
- Ginger L Hunter
- MRC-Laboratory for Molecular and Cell Biology, University College London, London WC1E 6BT, UK Institute of Physics of Living Systems, University College London, London WC1E 6BT, UK
| | - Zena Hadjivasiliou
- Centre for Mathematics, Physics, and Engineering in the Life Sciences and Experimental Biology, University College London, London WC1E 6BT, UK Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK
| | - Hope Bonin
- MRC-Laboratory for Molecular and Cell Biology, University College London, London WC1E 6BT, UK
| | - Li He
- Howard Hughes Medical Institute, Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Norbert Perrimon
- Howard Hughes Medical Institute, Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Guillaume Charras
- Institute of Physics of Living Systems, University College London, London WC1E 6BT, UK London Centre for Nanotechnology, University College London, London WC1E 6BT, UK Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Buzz Baum
- MRC-Laboratory for Molecular and Cell Biology, University College London, London WC1E 6BT, UK Institute of Physics of Living Systems, University College London, London WC1E 6BT, UK
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12
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Varadarajan R, Ayeni J, Jin Z, Homola E, Campbell SD. Myt1 inhibition of Cyclin A/Cdk1 is essential for fusome integrity and premeiotic centriole engagement in Drosophila spermatocytes. Mol Biol Cell 2016; 27:2051-63. [PMID: 27170181 PMCID: PMC4927279 DOI: 10.1091/mbc.e16-02-0104] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/05/2016] [Indexed: 12/14/2022] Open
Abstract
Drosophila Myt1 is essential for male fertility. Loss of Myt1 activity causes defective fusomes and premature centriole disengagement during premeiotic G2 phase due to lack of Myt1 inhibition of Cyclin A/Cdk1. These functions are distinct from known roles for Myt1 inhibition of Cyclin B/Cdk1 used to regulate G2/MI timing. Regulation of cell cycle arrest in premeiotic G2 phase coordinates germ cell maturation and meiotic cell division with hormonal and developmental signals by mechanisms that control Cyclin B synthesis and inhibitory phosphorylation of the M-phase kinase, Cdk1. In this study, we investigated how inhibitory phosphorylation of Cdk1 by Myt1 kinase regulates premeiotic G2 phase of Drosophila male meiosis. Immature spermatocytes lacking Myt1 activity exhibit two distinct defects: disrupted intercellular bridges (fusomes) and premature centriole disengagement. As a result, the myt1 mutant spermatocytes enter meiosis with multipolar spindles. These myt1 defects can be suppressed by depletion of Cyclin A activity or ectopic expression of Wee1 (a partially redundant Cdk1 inhibitory kinase) and phenocopied by expression of a Cdk1F mutant defective for inhibitory phosphorylation. We therefore conclude that Myt1 inhibition of Cyclin A/Cdk1 is essential for normal fusome behavior and centriole engagement during premeiotic G2 arrest of Drosophila male meiosis. The novel meiotic functions we discovered for Myt1 kinase are spatially and temporally distinct from previously described functions of Myt1 as an inhibitor of Cyclin B/Cdk1 to regulate G2/MI timing.
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Affiliation(s)
- Ramya Varadarajan
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Joseph Ayeni
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Zhigang Jin
- Cross Cancer Institute, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Ellen Homola
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Shelagh D Campbell
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada
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Ayeni JO, Audibert A, Fichelson P, Srayko M, Gho M, Campbell SD. G2 phase arrest prevents bristle progenitor self-renewal and synchronizes cell division with cell fate differentiation. Development 2016; 143:1160-9. [PMID: 26893341 DOI: 10.1242/dev.134270] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/08/2016] [Indexed: 11/20/2022]
Abstract
Developmentally regulated cell cycle arrest is a fundamental feature of neurogenesis, whose significance is poorly understood. During Drosophila sensory organ (SO) development, primary progenitor (pI) cells arrest in G2 phase for precisely defined periods. Upon re-entering the cell cycle in response to developmental signals, these G2-arrested precursor cells divide and generate specialized neuronal and non-neuronal cells. To study how G2 phase arrest affects SO lineage specification, we forced pI cells to divide prematurely. This produced SOs with normal neuronal lineages but supernumerary non-neuronal cell types because prematurely dividing pI cells generate a secondary pI cell that produces a complete SO and an external precursor cell that undergoes amplification divisions. pI cells are therefore able to undergo self-renewal before transit to a terminal mode of division. Regulation of G2 phase arrest thus serves a dual role in SO development: preventing progenitor self-renewal and synchronizing cell division with developmental signals. Cell cycle arrest in G2 phase temporally coordinates the precursor cell proliferation potential with terminal cell fate determination to ensure formation of organs with a normal set of sensory cells.
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Affiliation(s)
- Joseph O Ayeni
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
| | - Agnès Audibert
- Sorbonne Universités, UPMC University of Paris 06, IBPS-UMR 7622, Laboratory of Developmental Biology, Paris 75005, France
| | - Pierre Fichelson
- CNRS, IBPS-UMR 7622, Laboratory of Developmental Biology, Paris 75005, France
| | - Martin Srayko
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
| | - Michel Gho
- CNRS, IBPS-UMR 7622, Laboratory of Developmental Biology, Paris 75005, France
| | - Shelagh D Campbell
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
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14
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Toledo CM, Ding Y, Hoellerbauer P, Davis RJ, Basom R, Girard EJ, Lee E, Corrin P, Hart T, Bolouri H, Davison J, Zhang Q, Hardcastle J, Aronow BJ, Plaisier CL, Baliga NS, Moffat J, Lin Q, Li XN, Nam DH, Lee J, Pollard SM, Zhu J, Delrow JJ, Clurman BE, Olson JM, Paddison PJ. Genome-wide CRISPR-Cas9 Screens Reveal Loss of Redundancy between PKMYT1 and WEE1 in Glioblastoma Stem-like Cells. Cell Rep 2015; 13:2425-2439. [PMID: 26673326 PMCID: PMC4691575 DOI: 10.1016/j.celrep.2015.11.021] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 10/12/2015] [Accepted: 11/03/2015] [Indexed: 12/31/2022] Open
Abstract
To identify therapeutic targets for glioblastoma (GBM), we performed genome-wide CRISPR-Cas9 knockout (KO) screens in patient-derived GBM stem-like cells (GSCs) and human neural stem/progenitors (NSCs), non-neoplastic stem cell controls, for genes required for their in vitro growth. Surprisingly, the vast majority GSC-lethal hits were found outside of molecular networks commonly altered in GBM and GSCs (e.g., oncogenic drivers). In vitro and in vivo validation of GSC-specific targets revealed several strong hits, including the wee1-like kinase, PKMYT1/Myt1. Mechanistic studies demonstrated that PKMYT1 acts redundantly with WEE1 to inhibit cyclin B-CDK1 activity via CDK1-Y15 phosphorylation and to promote timely completion of mitosis in NSCs. However, in GSCs, this redundancy is lost, most likely as a result of oncogenic signaling, causing GBM-specific lethality.
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Affiliation(s)
- Chad M Toledo
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA; Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA
| | - Yu Ding
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Pia Hoellerbauer
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA; Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA
| | - Ryan J Davis
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA; Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA; Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Ryan Basom
- Genomics and Bioinformatics Shared Resources, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Emily J Girard
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Eunjee Lee
- Department of Genetics and Genomic Sciences, Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Philip Corrin
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Traver Hart
- Department of Molecular Genetics, University of Toronto and Donnelly Centre, Toronto, ON M5S3E1, Canada; Canadian Institute for Advanced Research, Toronto, ON M5G1Z8, Canada
| | - Hamid Bolouri
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Jerry Davison
- Genomics and Bioinformatics Shared Resources, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Qing Zhang
- Genomics and Bioinformatics Shared Resources, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Justin Hardcastle
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Bruce J Aronow
- Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | | | | | - Jason Moffat
- Department of Molecular Genetics, University of Toronto and Donnelly Centre, Toronto, ON M5S3E1, Canada; Canadian Institute for Advanced Research, Toronto, ON M5G1Z8, Canada
| | - Qi Lin
- Brain Tumor Program, Texas Children's Cancer Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Xiao-Nan Li
- Brain Tumor Program, Texas Children's Cancer Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Do-Hyun Nam
- Institute for Refractory Cancer Research, Samsung Medical Center, Seoul 135-710, Korea
| | - Jeongwu Lee
- Department of Stem Cell Biology and Regenerative Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44192, USA
| | - Steven M Pollard
- Edinburgh CRUK Cancer Research Centre and MRC Centre for Regenerative Medicine, The University of Edinburgh, Edinburgh EH16 4UU, UK
| | - Jun Zhu
- Department of Genetics and Genomic Sciences, Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Jeffery J Delrow
- Genomics and Bioinformatics Shared Resources, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Bruce E Clurman
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA; Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - James M Olson
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
| | - Patrick J Paddison
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA; Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA.
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15
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Verna C, Sawchuk MG, Linh NM, Scarpella E. Control of vein network topology by auxin transport. BMC Biol 2015; 13:94. [PMID: 26560462 PMCID: PMC4641347 DOI: 10.1186/s12915-015-0208-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 10/28/2015] [Indexed: 02/08/2023] Open
Abstract
Background Tissue networks such as the vascular networks of plant and animal organs transport signals and nutrients in most multicellular organisms. The transport function of tissue networks depends on topological features such as the number of networks’ components and the components’ connectedness; yet what controls tissue network topology is largely unknown, partly because of the difficulties in quantifying the effects of genes on tissue network topology. We address this problem for the vein networks of plant leaves by introducing biologically motivated descriptors of vein network topology; we combine these descriptors with cellular imaging and molecular genetic analysis; and we apply this combination of approaches to leaves of Arabidopsis thaliana that lack function of, overexpress or misexpress combinations of four PIN-FORMED (PIN) genes—PIN1, PIN5, PIN6, and PIN8—which encode transporters of the plant signal auxin and are known to control vein network geometry. Results We find that PIN1 inhibits vein formation and connection, and that PIN6 acts redundantly to PIN1 in these processes; however, the functions of PIN6 in vein formation are nonhomologous to those of PIN1, while the functions of PIN6 in vein connection are homologous to those of PIN1. We further find that PIN8 provides functions redundant and homologous to those of PIN6 in PIN1-dependent inhibition of vein formation, but that PIN8 has no functions in PIN1/PIN6-dependent inhibition of vein connection. Finally, we find that PIN5 promotes vein formation; that all the vein-formation-promoting functions of PIN5 are redundantly inhibited by PIN6 and PIN8; and that these functions of PIN5, PIN6, and PIN8 are independent of PIN1. Conclusions Our results suggest that PIN-mediated auxin transport controls the formation of veins and their connection into networks. Electronic supplementary material The online version of this article (doi:10.1186/s12915-015-0208-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Carla Verna
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
| | - Megan G Sawchuk
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
| | - Nguyen Manh Linh
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
| | - Enrico Scarpella
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
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16
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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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17
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Gupte TM. Mitochondrial Fragmentation Due to Inhibition of Fusion Increases Cyclin B through Mitochondrial Superoxide Radicals. PLoS One 2015; 10:e0126829. [PMID: 26000631 PMCID: PMC4441460 DOI: 10.1371/journal.pone.0126829] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 04/08/2015] [Indexed: 11/25/2022] Open
Abstract
During the cell cycle, mitochondria undergo regulated changes in morphology. Two particularly interesting events are first, mitochondrial hyperfusion during the G1-S transition and second, fragmentation during entry into mitosis. The mitochondria remain fragmented between late G2- and mitotic exit. This mitotic mitochondrial fragmentation constitutes a checkpoint in some cell types, of which little is known. We bypass the ‘mitotic mitochondrial fragmentation’ checkpoint by inducing fragmented mitochondrial morphology and then measure the effect on cell cycle progression. Using Drosophila larval hemocytes, Drosophila S2R+ cell and cells in the pouch region of wing imaginal disc of Drosophila larvae we show that inhibiting mitochondrial fusion, thereby increasing fragmentation, causes cellular hyperproliferation and an increase in mitotic index. However, mitochondrial fragmentation due to over-expression of the mitochondrial fission machinery does not cause these changes. Our experiments suggest that the inhibition of mitochondrial fusion increases superoxide radical content and leads to the upregulation of cyclin B that culminates in the observed changes in the cell cycle. We provide evidence for the importance of mitochondrial superoxide in this process. Our results provide an insight into the need for mitofusin-degradation during mitosis and also help in understanding the mechanism by which mitofusins may function as tumor suppressors.
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Affiliation(s)
- Tejas M. Gupte
- National Centre for Biological Sciences (NCBS-TIFR), UAS-GKVK campus, Bellary road, Bangalore, 560 065, Karnataka, India
- inStem, Institute for Stem Cell Biology and Regenerative Medicine, GKVK post, Bellary road, Bangalore, 560 065, Karnataka, India
- * E-mail:
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18
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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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19
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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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20
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Transcriptional networks controlling the cell cycle. G3-GENES GENOMES GENETICS 2013; 3:75-90. [PMID: 23316440 PMCID: PMC3538345 DOI: 10.1534/g3.112.004283] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 11/07/2012] [Indexed: 01/09/2023]
Abstract
In this work, we map the transcriptional targets of 107 previously identified Drosophila genes whose loss caused the strongest cell-cycle phenotypes in a genome-wide RNA interference screen and mine the resulting data computationally. Besides confirming existing knowledge, the analysis revealed several regulatory systems, among which were two highly-specific and interconnected feedback circuits, one between the ribosome and the proteasome that controls overall protein homeostasis, and the other between the ribosome and Myc/Max that regulates the protein synthesis capacity of cells. We also identified a set of genes that alter the timing of mitosis without affecting gene expression, indicating that the cyclic transcriptional program that produces the components required for cell division can be partially uncoupled from the cell division process itself. These genes all have a function in a pathway that regulates the phosphorylation state of Cdk1. We provide evidence showing that this pathway is involved in regulation of cell size, indicating that a Cdk1-regulated cell size checkpoint exists in metazoans.
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21
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Sallé J, Campbell SD, Gho M, Audibert A. CycA is involved in the control of endoreplication dynamics in the Drosophila bristle lineage. Development 2012; 139:547-57. [PMID: 22223681 DOI: 10.1242/dev.069823] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Endocycles, which are characterised by repeated rounds of DNA replication without intervening mitosis, are involved in developmental processes associated with an increase in metabolic cell activity and are part of terminal differentiation. Endocycles are currently viewed as a restriction of the canonical cell cycle. As such, mitotic cyclins have been omitted from the endocycle mechanism and their role in this process has not been specifically analysed. In order to study such a role, we focused on CycA, which has been described to function exclusively during mitosis in Drosophila. Using developing mechanosensory organs as model system and PCNA::GFP to follow endocycle dynamics, we show that (1) CycA proteins accumulate during the last period of endoreplication, (2) both CycA loss and gain of function induce changes in endoreplication dynamics and reduce the number of endocycles, and (3) heterochromatin localisation of ORC2, a member of the Pre-RC complex, depends on CycA. These results show for the first time that CycA is involved in endocycle dynamics in Drosophila. As such, CycA controls the final ploidy that cells reached during terminal differentiation. Furthermore, our data suggest that the control of endocycles by CycA involves the subnuclear relocalisation of pre-RC complex members. Our work therefore sheds new light on the mechanism underlying endocycles, implicating a process that involves remodelling of the entire cell cycle network rather than simply a restriction of the canonical cell cycle.
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Affiliation(s)
- Jérémy Sallé
- Université Pierre et Marie Curie-Paris 6, UMR 7622, Paris, France
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22
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Kondo S, Perrimon N. A genome-wide RNAi screen identifies core components of the G₂-M DNA damage checkpoint. Sci Signal 2011; 4:rs1. [PMID: 21205937 PMCID: PMC3489265 DOI: 10.1126/scisignal.2001350] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The DNA damage checkpoint, the first pathway known to be activated in response to DNA damage, is a mechanism by which the cell cycle is temporarily arrested to allow DNA repair. The checkpoint pathway transmits signals from the sites of DNA damage to the cell cycle machinery through the evolutionarily conserved ATM (ataxia telangiectasia mutated) and ATR (ATM- and Rad3-related) kinase cascades. We conducted a genome-wide RNAi (RNA interference) screen in Drosophila cells to identify previously unknown genes and pathways required for the G₂-M checkpoint induced by DNA double-strand breaks (DSBs). Our large-scale analysis provided a systems-level view of the G₂-M checkpoint and revealed the coordinated actions of particular classes of proteins, which include those involved in DNA repair, DNA replication, cell cycle control, chromatin regulation, and RNA processing. Further, from the screen and in vivo analysis, we identified previously unrecognized roles of two DNA damage response genes, mus101 and mus312. Our results suggest that the DNA replication preinitiation complex, which includes MUS101, and the MUS312-containing nuclease complexes, which are important for DSB repair, also function in the G₂-M checkpoint. Our results provide insight into the diverse mechanisms that link DNA damage and the checkpoint signaling pathway.
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Affiliation(s)
- Shu Kondo
- Department of Genetics and Howard Hughes Medical Institute, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA
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23
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Qi J, Yu JY, Shcherbata HR, Mathieu J, Wang AJ, Seal S, Zhou W, Stadler BM, Bourgin D, Wang L, Nelson A, Ware C, Raymond C, Lim LP, Magnus J, Ivanovska I, Diaz R, Ball A, Cleary MA, Ruohola-Baker H. microRNAs regulate human embryonic stem cell division. Cell Cycle 2009; 8:3729-41. [PMID: 19823043 DOI: 10.4161/cc.8.22.10033] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
microRNAs (miRNAs) regulate numerous physiological processes such as cell division and differentiation in many tissue types including stem cells. To probe the role that miRNAs play in regulating processes relevant to embryonic stem cell biology, we used RNA interference to silence DICER and DROSHA, the two main miRNA processing enzymes. Consistent with a role for miRNAs in maintaining normal stem cell division and renewal, we found that perturbation of miRNA pathway function in human embryonic stem cells (hESCs) attenuates cell proliferation. Normal cell growth can be partially restored by introduction of the mature miRNAs miR-195 and miR-372. These miRNAs regulate two tumor suppressor genes, respectively: WEE1, which encodes a negative G2/M kinase modulator of the CycB/CDK complex and CDKN1A, which encodes p21, a CycE/CDK cyclin dependent kinase inhibitor that regulates the G1/S transition. We show that in wild-type hESCs, WEE 1 levels control the rate of hESC division, whereas p21 levels must be maintained at a low level for hESC division to proceed. These data support a model for hESC cell cycle control in which miRNAs regulate negative cell cycle modulators at two phases of the cell cycle to ensure proper replenishment of the stem cell population.
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Affiliation(s)
- Junlin Qi
- Department of Biochemistry and Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA, USA
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24
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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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