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Fan LH, Qi ST, Wang ZB, Ouyang YC, Lei WL, Wang Y, Li A, Wang F, Li J, Li L, Li YY, Hou Y, Schatten H, Wang WH, Sun QY, Ou XH. MEIKIN expression and its C-terminal phosphorylation by PLK1 is closely related the metaphase-anaphase transition by affecting cyclin B1 and Securin stabilization in meiotic oocyte. Histochem Cell Biol 2024:10.1007/s00418-024-02316-7. [PMID: 39093409 DOI: 10.1007/s00418-024-02316-7] [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] [Accepted: 07/22/2024] [Indexed: 08/04/2024]
Abstract
Oocyte meiotic maturation failure and chromosome abnormality is one of the main causes of infertility, abortion, and diseases. The mono-orientation of sister chromatids during the first meiosis is important for ensuring accurate chromosome segregation in oocytes. MEIKIN is a germ cell-specific protein that can regulate the mono-orientation of sister chromatids and the protection of the centromeric cohesin complex during meiosis I. Here we found that MEIKIN is a maternal protein that was highly expressed in mouse oocytes before the metaphase I (MI) stage, but became degraded by the MII stage and dramatically reduced after fertilization. Strikingly, MEIKIN underwent phosphorylation modification after germinal vesicle breakdown (GVBD), indicating its possible function in subsequent cellular event regulation. We further showed that MEIKIN phosphorylation was mediated by PLK1 at its carboxyl terminal region and its C-terminus was its key functional domain. To clarify the biological significance of meikin degradation during later stages of oocyte maturation, exogenous expression of MEIKIN was employed, which showed that suppression of MEIKIN degradation resulted in chromosome misalignment, cyclin B1 and Securin degradation failure, and MI arrest through a spindle assembly checkpoint (SAC)-independent mechanism. Exogenous expression of MEIKIN also inhibited metaphase II (MII) exit and early embryo development. These results indicate that proper MEIKIN expression level and its C-terminal phosphorylation by PLK1 are critical for regulating the metaphase-anaphase transition in meiotic oocyte. The findings of this study are important for understanding the regulation of chromosome segregation and the prevention meiotic abnormality.
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Affiliation(s)
- Li-Hua Fan
- Fertility Preservation Laboratory, Reproductive Medicine Center, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- Guangdong-Hong Kong Metabolism & Reproduction Joint Laboratory, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China
- University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Shu-Tao Qi
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- Key Laboratory of Major Obstetrics Diseases of Guangdong Province, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, 510150, China
| | - Zhen-Bo Wang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Ying-Chun Ouyang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Wen-Long Lei
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Yue Wang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Ang Li
- Fertility Preservation Laboratory, Reproductive Medicine Center, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- Guangdong-Hong Kong Metabolism & Reproduction Joint Laboratory, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China
| | - Feng Wang
- Fertility Preservation Laboratory, Reproductive Medicine Center, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- Guangdong-Hong Kong Metabolism & Reproduction Joint Laboratory, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China
| | - Jian Li
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Li Li
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Yuan-Yuan Li
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yi Hou
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Heide Schatten
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO, 65211, USA
| | - Wei-Hua Wang
- Key Laboratory of Major Obstetrics Diseases of Guangdong Province, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, 510150, China.
| | - Qing-Yuan Sun
- Fertility Preservation Laboratory, Reproductive Medicine Center, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China.
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China.
- Guangdong-Hong Kong Metabolism & Reproduction Joint Laboratory, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China.
- University of Chinese Academy of Sciences, Beijing, 100101, China.
| | - Xiang-Hong Ou
- Fertility Preservation Laboratory, Reproductive Medicine Center, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China.
- Guangdong-Hong Kong Metabolism & Reproduction Joint Laboratory, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China.
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2
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Koch LB, Spanos C, Kelly V, Ly T, Marston AL. Rewiring of the phosphoproteome executes two meiotic divisions in budding yeast. EMBO J 2024; 43:1351-1383. [PMID: 38413836 PMCID: PMC10987667 DOI: 10.1038/s44318-024-00059-8] [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: 09/13/2023] [Revised: 02/06/2024] [Accepted: 02/07/2024] [Indexed: 02/29/2024] Open
Abstract
The cell cycle is ordered by a controlled network of kinases and phosphatases. To generate gametes via meiosis, two distinct and sequential chromosome segregation events occur without an intervening S phase. How canonical cell cycle controls are modified for meiosis is not well understood. Here, using highly synchronous budding yeast populations, we reveal how the global proteome and phosphoproteome change during the meiotic divisions. While protein abundance changes are limited to key cell cycle regulators, dynamic phosphorylation changes are pervasive. Our data indicate that two waves of cyclin-dependent kinase (Cdc28Cdk1) and Polo (Cdc5Polo) kinase activity drive successive meiotic divisions. These two distinct phases of phosphorylation are ensured by the meiosis-specific Spo13 protein, which rewires the phosphoproteome. Spo13 binds to Cdc5Polo to promote phosphorylation in meiosis I, particularly of substrates containing a variant of the canonical Cdc5Polo motif. Overall, our findings reveal that a master regulator of meiosis directs the activity of a kinase to change the phosphorylation landscape and elicit a developmental cascade.
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Affiliation(s)
- Lori B Koch
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh, EH9 3BF, UK
| | - Christos Spanos
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh, EH9 3BF, UK
| | - Van Kelly
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh, EH9 3BF, UK
| | - Tony Ly
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh, EH9 3BF, UK
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Adele L Marston
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh, EH9 3BF, UK.
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3
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Rojas J, Oz T, Jonak K, Lyzak O, Massaad V, Biriuk O, Zachariae W. Spo13/MEIKIN ensures a Two-Division meiosis by preventing the activation of APC/C Ama1 at meiosis I. EMBO J 2023; 42:e114288. [PMID: 37728253 PMCID: PMC10577557 DOI: 10.15252/embj.2023114288] [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: 04/14/2023] [Revised: 09/03/2023] [Accepted: 09/04/2023] [Indexed: 09/21/2023] Open
Abstract
Genome haploidization at meiosis depends on two consecutive nuclear divisions, which are controlled by an oscillatory system consisting of Cdk1-cyclin B and the APC/C bound to the Cdc20 activator. How the oscillator generates exactly two divisions has been unclear. We have studied this question in yeast where exit from meiosis involves accumulation of the APC/C activator Ama1 at meiosis II. We show that inactivation of the meiosis I-specific protein Spo13/MEIKIN results in a single-division meiosis due to premature activation of APC/CAma1 . In the wild type, Spo13 bound to the polo-like kinase Cdc5 prevents Ama1 synthesis at meiosis I by stabilizing the translational repressor Rim4. In addition, Cdc5-Spo13 inhibits the activity of Ama1 by converting the B-type cyclin Clb1 from a substrate to an inhibitor of Ama1. Cdc20-dependent degradation of Spo13 at anaphase I unleashes a feedback loop that increases Ama1's synthesis and activity, leading to irreversible exit from meiosis at the second division. Thus, by repressing the exit machinery at meiosis I, Cdc5-Spo13 ensures that cells undergo two divisions to produce haploid gametes.
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Affiliation(s)
- Julie Rojas
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
- Present address:
Laboratory of GeneticsUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Tugce Oz
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Katarzyna Jonak
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
- Present address:
Institute of Biochemistry and BiophysicsPolish Academy of SciencesWarsawPoland
| | - Oleksii Lyzak
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Vinal Massaad
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Olha Biriuk
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Wolfgang Zachariae
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
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4
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Börner GV, Hochwagen A, MacQueen AJ. Meiosis in budding yeast. Genetics 2023; 225:iyad125. [PMID: 37616582 PMCID: PMC10550323 DOI: 10.1093/genetics/iyad125] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 06/13/2023] [Indexed: 08/26/2023] Open
Abstract
Meiosis is a specialized cell division program that is essential for sexual reproduction. The two meiotic divisions reduce chromosome number by half, typically generating haploid genomes that are packaged into gametes. To achieve this ploidy reduction, meiosis relies on highly unusual chromosomal processes including the pairing of homologous chromosomes, assembly of the synaptonemal complex, programmed formation of DNA breaks followed by their processing into crossovers, and the segregation of homologous chromosomes during the first meiotic division. These processes are embedded in a carefully orchestrated cell differentiation program with multiple interdependencies between DNA metabolism, chromosome morphogenesis, and waves of gene expression that together ensure the correct number of chromosomes is delivered to the next generation. Studies in the budding yeast Saccharomyces cerevisiae have established essentially all fundamental paradigms of meiosis-specific chromosome metabolism and have uncovered components and molecular mechanisms that underlie these conserved processes. Here, we provide an overview of all stages of meiosis in this key model system and highlight how basic mechanisms of genome stability, chromosome architecture, and cell cycle control have been adapted to achieve the unique outcome of meiosis.
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Affiliation(s)
- G Valentin Börner
- Center for Gene Regulation in Health and Disease (GRHD), Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, OH 44115, USA
| | | | - Amy J MacQueen
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06459, USA
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5
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Jeong SM, Bui QT, Kwak M, Lee JY, Lee PCW. Targeting Cdc20 for cancer therapy. Biochim Biophys Acta Rev Cancer 2022; 1877:188824. [DOI: 10.1016/j.bbcan.2022.188824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 09/26/2022] [Accepted: 10/06/2022] [Indexed: 11/26/2022]
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6
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Oz T, Mengoli V, Rojas J, Jonak K, Braun M, Zagoriy I, Zachariae W. The Spo13/Meikin pathway confines the onset of gamete differentiation to meiosis II in yeast. EMBO J 2022; 41:e109446. [PMID: 35023198 PMCID: PMC8844990 DOI: 10.15252/embj.2021109446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 12/06/2021] [Accepted: 12/20/2021] [Indexed: 11/09/2022] Open
Abstract
Sexual reproduction requires genome haploidization by the two divisions of meiosis and a differentiation program to generate gametes. Here, we have investigated how sporulation, the yeast equivalent of gamete differentiation, is coordinated with progression through meiosis. Spore differentiation is initiated at metaphase II when a membrane-nucleating structure, called the meiotic plaque, is assembled at the centrosome. While all components of this structure accumulate already at entry into meiosis I, they cannot assemble because centrosomes are occupied by Spc72, the receptor of the γ-tubulin complex. Spc72 is removed from centrosomes by a pathway that depends on the polo-like kinase Cdc5 and the meiosis-specific kinase Ime2, which is unleashed by the degradation of Spo13/Meikin upon activation of the anaphase-promoting complex at anaphase I. Meiotic plaques are finally assembled upon reactivation of Cdk1 at entry into metaphase II. This unblocking-activation mechanism ensures that only single-copy genomes are packaged into spores and might serve as a paradigm for the regulation of other meiosis II-specific processes.
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Affiliation(s)
- Tugce Oz
- Laboratory of Chromosome Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Valentina Mengoli
- Laboratory of Chromosome Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Julie Rojas
- Laboratory of Chromosome Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Katarzyna Jonak
- Laboratory of Chromosome Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Marianne Braun
- Max Planck Institute of Neurobiology, Martinsried, Germany
| | - Ievgeniia Zagoriy
- Laboratory of Chromosome Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Wolfgang Zachariae
- Laboratory of Chromosome Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
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7
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Maier NK, Ma J, Lampson MA, Cheeseman IM. Separase cleaves the kinetochore protein Meikin at the meiosis I/II transition. Dev Cell 2021; 56:2192-2206.e8. [PMID: 34331869 PMCID: PMC8355204 DOI: 10.1016/j.devcel.2021.06.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 05/03/2021] [Accepted: 06/25/2021] [Indexed: 12/19/2022]
Abstract
To generate haploid gametes, germ cells undergo two consecutive meiotic divisions requiring key changes to the cell division machinery. Here, we demonstrate that the protease separase rewires key cell division processes at the meiosis I/II transition by cleaving the meiosis-specific protein Meikin. Separase proteolysis does not inactivate Meikin but instead alters its function to create a distinct activity state. Full-length Meikin and the C-terminal Meikin separase cleavage product both localize to kinetochores, bind to Plk1 kinase, and promote Rec8 cleavage, but our results reveal distinct roles for these proteins in controlling meiosis. Mutations that prevent Meikin cleavage or that conditionally inactivate Meikin at anaphase I result in defective meiosis II chromosome alignment in mouse oocytes. Finally, as oocytes exit meiosis, C-Meikin is eliminated by APC/C-mediated degradation prior to the first mitotic division. Thus, multiple regulatory events irreversibly modulate Meikin activity during successive meiotic divisions to rewire the cell division machinery at two distinct transitions.
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Affiliation(s)
- Nolan K Maier
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Jun Ma
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Michael A Lampson
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Iain M Cheeseman
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
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8
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Mengoli V, Jonak K, Lyzak O, Lamb M, Lister LM, Lodge C, Rojas J, Zagoriy I, Herbert M, Zachariae W. Deprotection of centromeric cohesin at meiosis II requires APC/C activity but not kinetochore tension. EMBO J 2021; 40:e106812. [PMID: 33644894 PMCID: PMC8013787 DOI: 10.15252/embj.2020106812] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 01/21/2021] [Accepted: 01/22/2021] [Indexed: 01/03/2023] Open
Abstract
Genome haploidization involves sequential loss of cohesin from chromosome arms and centromeres during two meiotic divisions. At centromeres, cohesin's Rec8 subunit is protected from separase cleavage at meiosis I and then deprotected to allow its cleavage at meiosis II. Protection of centromeric cohesin by shugoshin-PP2A seems evolutionarily conserved. However, deprotection has been proposed to rely on spindle forces separating the Rec8 protector from cohesin at metaphase II in mammalian oocytes and on APC/C-dependent destruction of the protector at anaphase II in yeast. Here, we have activated APC/C in the absence of sister kinetochore biorientation at meiosis II in yeast and mouse oocytes, and find that bipolar spindle forces are dispensable for sister centromere separation in both systems. Furthermore, we show that at least in yeast, protection of Rec8 by shugoshin and inhibition of separase by securin are both required for the stability of centromeric cohesin at metaphase II. Our data imply that related mechanisms preserve the integrity of dyad chromosomes during the short metaphase II of yeast and the prolonged metaphase II arrest of mammalian oocytes.
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Affiliation(s)
- Valentina Mengoli
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
- Present address:
Institute for Research in BiomedicineUniversità della Svizzera ItalianaBellinzonaSwitzerland
| | - Katarzyna Jonak
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Oleksii Lyzak
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Mahdi Lamb
- Biosciences InstituteCentre for LifeTimes SquareNewcastle UniversityNewcastle upon TyneUK
| | - Lisa M Lister
- Biosciences InstituteCentre for LifeTimes SquareNewcastle UniversityNewcastle upon TyneUK
| | - Chris Lodge
- Biosciences InstituteCentre for LifeTimes SquareNewcastle UniversityNewcastle upon TyneUK
| | - Julie Rojas
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Ievgeniia Zagoriy
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
- Present address:
EMBL HeidelbergHeidelbergGermany
| | - Mary Herbert
- Biosciences InstituteCentre for LifeTimes SquareNewcastle UniversityNewcastle upon TyneUK
| | - Wolfgang Zachariae
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
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9
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Galander S, Marston AL. Meiosis I Kinase Regulators: Conserved Orchestrators of Reductional Chromosome Segregation. Bioessays 2020; 42:e2000018. [PMID: 32761854 PMCID: PMC7116124 DOI: 10.1002/bies.202000018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Revised: 06/15/2020] [Indexed: 12/19/2022]
Abstract
Research over the last two decades has identified a group of meiosis-specific proteins, consisting of budding yeast Spo13, fission yeast Moa1, mouse MEIKIN, and Drosophila Mtrm, with essential functions in meiotic chromosome segregation. These proteins, which we call meiosis I kinase regulators (MOKIRs), mediate two major adaptations to the meiotic cell cycle to allow the generation of haploid gametes from diploid mother cells. Firstly, they promote the segregation of homologous chromosomes in meiosis I (reductional division) by ensuring that sister kinetochores face towards the same pole (mono-orientation). Secondly, they safeguard the timely separation of sister chromatids in meiosis II (equational division) by counteracting the premature removal of pericentromeric cohesin, and thus prevent the formation of aneuploid gametes. Although MOKIRs bear no obvious sequence similarity, they appear to play functionally conserved roles in regulating meiotic kinases. Here, the known functions of MOKIRs are reviewed and their possible mechanisms of action are discussed. Also see the video abstract here https://youtu.be/tLE9KL89bwk.
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Affiliation(s)
- Stefan Galander
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born Crescent, Edinburgh, EH9 3BF UK
| | - Adèle L Marston
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born Crescent, Edinburgh, EH9 3BF UK
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10
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Tsunematsu T, Arakaki R, Kawai H, Ruppert J, Tsuneyama K, Ishimaru N, Earnshaw WC, Pagano M, Kudo Y. APC/C Cdh1 is required for the termination of chromosomal passenger complex activity upon mitotic exit. J Cell Sci 2020; 133:133/18/jcs251314. [PMID: 32934012 PMCID: PMC7520452 DOI: 10.1242/jcs.251314] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 07/13/2020] [Indexed: 01/31/2023] Open
Abstract
During mitosis, the chromosomal passenger complex (CPC) ensures the faithful transmission of the genome. The CPC is composed of the enzymatic component Aurora B (AURKB) and the three regulatory and targeting components borealin, INCENP, and survivin (also known as BIRC5). Although the CPC is known to be involved in diverse mitotic events, it is still unclear how CPC function terminates after mitosis. Here we show that borealin is ubiquitylated by the anaphase promoting complex/cyclosome (APC/C) and its cofactor Cdh1 (also known as FZR1) and is subsequently degraded in G1 phase. Cdh1 binds to regions within the N terminus of borealin that act as a non-canonical degron. Aurora B has also been shown previously to be degraded by the APC/CCdh1 from late mitosis to G1. Indeed, Cdh1 depletion sustains an Aurora B activity with stable levels of borealin and Aurora B throughout the cell cycle, and causes reduced efficiency of DNA replication after release from serum starvation. Notably, inhibition of Aurora B kinase activity improves the efficiency of DNA replication in Cdh1-depleted cells. We thus propose that APC/CCdh1 terminates CPC activity upon mitotic exit and thereby contributes to proper control of DNA replication. Summary: APC/CCdh1 ubiquitylates both borealin, via a non-canonical degron motif, and Aurora B to terminate activity of the CPC in G1 phase. Disruption of this ubiquitylation reduces the efficiency of DNA replication.
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Affiliation(s)
- Takaaki Tsunematsu
- Department of Oral Molecular Pathology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8504, Japan
| | - Rieko Arakaki
- Department of Oral Molecular Pathology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8504, Japan
| | - Hidehiko Kawai
- Department of Nucleic Acids Biochemistry, Hiroshima University Graduate School of Biomedical & Health Sciences, Hiroshima 734-8553, Japan
| | - Jan Ruppert
- Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK
| | - Koichi Tsuneyama
- Department of Pathology and Laboratory Medicine, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8504, Japan
| | - Naozumi Ishimaru
- Department of Oral Molecular Pathology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8504, Japan
| | - William C Earnshaw
- Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK
| | - Michele Pagano
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA.,NYU Perlmutter Cancer Center, New York University School of Medicine, New York, NY 10016, USA.,Howard Hughes Medical Institute, New York University School of Medicine, New York, NY 10016, USA
| | - Yasusei Kudo
- Department of Oral Molecular Pathology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8504, Japan .,Department of Oral Bioscience, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8504, Japan
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11
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Bansal S, Tiwari S. Mechanisms for the temporal regulation of substrate ubiquitination by the anaphase-promoting complex/cyclosome. Cell Div 2019; 14:14. [PMID: 31889987 PMCID: PMC6927175 DOI: 10.1186/s13008-019-0057-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 12/04/2019] [Indexed: 12/16/2022] Open
Abstract
The anaphase-promoting complex/cyclosome (APC/C) is a multi-subunit, multifunctional ubiquitin ligase that controls the temporal degradation of numerous cell cycle regulatory proteins to direct the unidirectional cell cycle phases. Several different mechanisms contribute to ensure the correct order of substrate modification by the APC/C complex. Recent advances in biochemical, biophysical and structural studies of APC/C have provided a deep mechanistic insight into the working of this complex ubiquitin ligase. This complex displays remarkable conformational flexibility in response to various binding partners and post-translational modifications, which together regulate substrate selection and catalysis of APC/C. Apart from this, various features and modifications of the substrates also influence their recognition and affinity to APC/C complex. Ultimately, temporal degradation of substrates depends on the kind of ubiquitin modification received, the processivity of APC/C, and other extrinsic mechanisms. This review discusses our current understanding of various intrinsic and extrinsic mechanisms responsible for 'substrate ordering' by the APC/C complex.
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Affiliation(s)
- Shivangee Bansal
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067 India
| | - Swati Tiwari
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067 India
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12
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Galander S, Barton RE, Borek WE, Spanos C, Kelly DA, Robertson D, Rappsilber J, Marston AL. Reductional Meiosis I Chromosome Segregation Is Established by Coordination of Key Meiotic Kinases. Dev Cell 2019; 49:526-541.e5. [PMID: 31031198 PMCID: PMC6547162 DOI: 10.1016/j.devcel.2019.04.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 12/05/2018] [Accepted: 03/31/2019] [Indexed: 02/07/2023]
Abstract
Meiosis produces gametes through a specialized, two-step cell division, which is highly error prone in humans. Reductional meiosis I, where maternal and paternal chromosomes (homologs) segregate, is followed by equational meiosis II, where sister chromatids separate. Uniquely during meiosis I, sister kinetochores are monooriented and pericentromeric cohesin is protected. Here, we demonstrate that these key adaptations for reductional chromosome segregation are achieved through separable control of multiple kinases by the meiosis-I-specific budding yeast Spo13 protein. Recruitment of Polo kinase to kinetochores directs monoorientation, while independently, cohesin protection is achieved by containing the effects of cohesin kinases. Therefore, reductional chromosome segregation, the defining feature of meiosis, is established by multifaceted kinase control by a master regulator. The recent identification of Spo13 orthologs, fission yeast Moa1 and mouse MEIKIN, suggests that kinase coordination by a meiosis I regulator may be a general feature in the establishment of reductional chromosome segregation.
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Affiliation(s)
- Stefan Galander
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Rachael E Barton
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Weronika E Borek
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Christos Spanos
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - David A Kelly
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Daniel Robertson
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Juri Rappsilber
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born Crescent, Edinburgh EH9 3BF, UK; Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Adèle L Marston
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born Crescent, Edinburgh EH9 3BF, UK.
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13
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Mehta G, Anbalagan GK, Bharati AP, Gadre P, Ghosh SK. An interplay between Shugoshin and Spo13 for centromeric cohesin protection and sister kinetochore mono-orientation during meiosis I in Saccharomyces cerevisiae. Curr Genet 2018; 64:1141-1152. [PMID: 29644457 DOI: 10.1007/s00294-018-0832-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 03/24/2018] [Accepted: 04/03/2018] [Indexed: 10/17/2022]
Abstract
Meiosis is a specialized cell division process by which haploid gametes are produced from a diploid mother cell. Reductional chromosome segregation during meiosis I (MI) is achieved by two unique and conserved events: centromeric cohesin protection (CCP) and sister kinetochore mono-orientation (SKM). In Saccharomyces cerevisiae, a meiosis-specific protein Spo13 plays a role in both these centromere-specific events. Despite genome-wide association of Spo13, we failed to detect its function in global processes such as cohesin loading, cohesion establishment and homologs pairing. While Shugoshin (Sgo1) and protein phosphatase 2A (PP2ARts1) play a central role in CCP, it is not fully understood whether Spo13 functions in the process through a Sgo1- PP2ARts1-dependent or -independent mechanism. To delineate this and to find the relative contribution of each of these proteins in CCP and SKM, we meticulously observed the sister chromatid segregation pattern in the wild type, sgo1Δ, rts1Δ and spo13Δ single mutants and in their respective double mutants. We found that Spo13 protects centromeric cohesin through a Sgo1- PP2ARts1-independent mechanism. To our surprise, we observed a hitherto unknown role of Sgo1 in SKM. Further investigation revealed that Sgo1-mediated recruitment of aurora kinase Ipl1 to the centromere facilitates monopolin loading at the kinetochore during MI. Hence, this study uncovers the role of Sgo1 in SKM and demonstartes how the regulators (Sgo1, PP2ARts1, Spo13) work in a coordinated manner to achieve faithful chromosome segregation during meiosis, the failure of which leads to aneuploidy and birth defects.
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Affiliation(s)
- Gunjan Mehta
- National Cancer Institute, National Institutes of Health, 41 Medlars Drive, Bethesda, MD, 20892, USA
| | | | - Akhilendra Pratap Bharati
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Bombay, Powai, Mumbai, 400076, India
| | - Purna Gadre
- B231, Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, 400005, India
| | - Santanu Kumar Ghosh
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Bombay, Powai, Mumbai, 400076, India.
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14
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Alfieri C, Zhang S, Barford D. Visualizing the complex functions and mechanisms of the anaphase promoting complex/cyclosome (APC/C). Open Biol 2017; 7:170204. [PMID: 29167309 PMCID: PMC5717348 DOI: 10.1098/rsob.170204] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 10/10/2017] [Indexed: 12/17/2022] Open
Abstract
The anaphase promoting complex or cyclosome (APC/C) is a large multi-subunit E3 ubiquitin ligase that orchestrates cell cycle progression by mediating the degradation of important cell cycle regulators. During the two decades since its discovery, much has been learnt concerning its role in recognizing and ubiquitinating specific proteins in a cell-cycle-dependent manner, the mechanisms governing substrate specificity, the catalytic process of assembling polyubiquitin chains on its target proteins, and its regulation by phosphorylation and the spindle assembly checkpoint. The past few years have witnessed significant progress in understanding the quantitative mechanisms underlying these varied APC/C functions. This review integrates the overall functions and properties of the APC/C with mechanistic insights gained from recent cryo-electron microscopy (cryo-EM) studies of reconstituted human APC/C complexes.
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Affiliation(s)
- Claudio Alfieri
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Suyang Zhang
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - David Barford
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
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15
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Davey NE, Morgan DO. Building a Regulatory Network with Short Linear Sequence Motifs: Lessons from the Degrons of the Anaphase-Promoting Complex. Mol Cell 2017; 64:12-23. [PMID: 27716480 DOI: 10.1016/j.molcel.2016.09.006] [Citation(s) in RCA: 110] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The anaphase-promoting complex or cyclosome (APC/C) is a ubiquitin ligase that polyubiquitinates specific substrates at precise times in the cell cycle, thereby triggering the events of late mitosis in a strict order. The robust substrate specificity of the APC/C prevents the potentially deleterious degradation of non-APC/C substrates and also averts the cell-cycle errors and genomic instability that could result from mistimed degradation of APC/C targets. The APC/C recognizes short linear sequence motifs, or degrons, on its substrates. The specific and timely modification and degradation of APC/C substrates is likely to be modulated by variations in degron sequence and context. We discuss the extensive affinity, specificity, and selectivity determinants encoded in APC/C degrons, and we describe some of the extrinsic mechanisms that control APC/C-substrate recognition. As an archetype for protein motif-driven regulation of cell function, the APC/C-substrate interaction provides insights into the general properties of post-translational regulatory systems.
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Affiliation(s)
- Norman E Davey
- Conway Institute of Biomolecular and Biomedical Sciences, University College Dublin, Dublin 4, Ireland.
| | - David O Morgan
- Departments of Physiology and Biochemistry & Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA.
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16
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Qin L, Guimarães DSPSF, Melesse M, Hall MC. Substrate Recognition by the Cdh1 Destruction Box Receptor Is a General Requirement for APC/CCdh1-mediated Proteolysis. J Biol Chem 2016; 291:15564-74. [PMID: 27226622 DOI: 10.1074/jbc.m116.731190] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Indexed: 11/06/2022] Open
Abstract
The anaphase-promoting complex, or cyclosome (APC/C), is a ubiquitin ligase that selectively targets proteins for degradation in mitosis and the G1 phase and is an important component of the eukaryotic cell cycle control system. How the APC/C specifically recognizes its substrates is not fully understood. Although well characterized degron motifs such as the destruction box (D-box) and KEN-box are commonly found in APC/C substrates, many substrates apparently lack these motifs. A variety of alternative APC/C degrons have been reported, suggesting either that multiple modes of substrate recognition are possible or that our definitions of degron structure are incomplete. We used an in vivo yeast assay to compare the G1 degradation rate of 15 known substrates of the APC/C co-activator Cdh1 under normal conditions and conditions that impair binding of D-box, KEN-box, and the recently identified ABBA motif degrons to Cdh1. The D-box receptor was required for efficient proteolysis of all Cdh1 substrates, despite the absence of canonical D-boxes in many. In contrast, the KEN-box receptor was only required for normal proteolysis of a subset of substrates and the ABBA motif receptor for a single substrate in our system. Our results suggest that binding to the D-box receptor may be a shared requirement for recognition and processing of all Cdh1 substrates.
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Affiliation(s)
- Liang Qin
- From the Department of Biochemistry and Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
| | | | - Michael Melesse
- From the Department of Biochemistry and Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
| | - Mark C Hall
- From the Department of Biochemistry and Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
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17
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Tsunematsu T, Arakaki R, Yamada A, Ishimaru N, Kudo Y. The Non-Canonical Role of Aurora-A in DNA Replication. Front Oncol 2015; 5:187. [PMID: 26380219 PMCID: PMC4548192 DOI: 10.3389/fonc.2015.00187] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 08/05/2015] [Indexed: 12/04/2022] Open
Abstract
Aurora-A is a well-known mitotic kinase that regulates mitotic entry, spindle formation, and chromosome maturation as a canonical role. During mitosis, Aurora-A protein is stabilized by its phosphorylation at Ser51 via blocking anaphase-promoting complex/cyclosome-mediated proteolysis. Importantly, overexpression and/or hyperactivation of Aurora-A is involved in tumorigenesis via aneuploidy and genomic instability. Recently, the novel function of Aurora-A for DNA replication has been revealed. In mammalian cells, DNA replication is strictly regulated for preventing over-replication. Pre-replication complex (pre-RC) formation is required for DNA replication as an initiation step occurring at the origin of replication. The timing of pre-RC formation depends on the protein level of geminin, which is controlled by the ubiquitin–proteasome pathway. Aurora-A phosphorylates geminin to prevent its ubiquitin-mediated proteolysis at the mitotic phase to ensure proper pre-RC formation and ensuing DNA replication. In this review, we introduce the novel non-canonical role of Aurora-A in DNA replication.
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Affiliation(s)
- Takaaki Tsunematsu
- Department of Oral Molecular Pathology, Institute of Biomedical Sciences, Tokushima University Graduate School , Tokushima , Japan
| | - Rieko Arakaki
- Department of Oral Molecular Pathology, Institute of Biomedical Sciences, Tokushima University Graduate School , Tokushima , Japan
| | - Akiko Yamada
- Department of Oral Molecular Pathology, Institute of Biomedical Sciences, Tokushima University Graduate School , Tokushima , Japan
| | - Naozumi Ishimaru
- Department of Oral Molecular Pathology, Institute of Biomedical Sciences, Tokushima University Graduate School , Tokushima , Japan
| | - Yasusei Kudo
- Department of Oral Molecular Pathology, Institute of Biomedical Sciences, Tokushima University Graduate School , Tokushima , Japan
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18
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Nasmyth K. A meiotic mystery: How sister kinetochores avoid being pulled in opposite directions during the first division. Bioessays 2015; 37:657-65. [PMID: 25874377 PMCID: PMC4683677 DOI: 10.1002/bies.201500006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 03/12/2015] [Accepted: 03/12/2015] [Indexed: 12/21/2022]
Abstract
We now take for granted that despite the disproportionate contribution of females to initial growth of their progeny, there is little or no asymmetry in the contribution of males and females to the eventual character of their shared offspring. In fact, this key insight was only established towards the end of the eighteenth century by Joseph Koelreuter's pioneering plant breeding experiments. If males and females supply equal amounts of hereditary material, then the latter must double each time an embryo is conceived. How then does the amount of this mysterious stuff not multiply exponentially from generation to generation? A compensatory mechanism for diluting the hereditary material must exist, one that ensures that if each parent contributes one half, each grandparent contributes a quarter, and each great grandparent merely an eighth. An important piece of the puzzle of how hereditary material is diluted at each generation has been elucidated over the past ten years.
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Affiliation(s)
- Kim Nasmyth
- Department of Biochemistry, Oxford University, Oxford, UK
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19
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The anaphase promoting complex regulates yeast lifespan and rDNA stability by targeting Fob1 for degradation. Genetics 2013; 196:693-709. [PMID: 24361936 DOI: 10.1534/genetics.113.158949] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Genomic stability, stress response, and nutrient signaling all play critical, evolutionarily conserved roles in lifespan determination. However, the molecular mechanisms coordinating these processes with longevity remain unresolved. Here we investigate the involvement of the yeast anaphase promoting complex (APC) in longevity. The APC governs passage through M and G1 via ubiquitin-dependent targeting of substrate proteins and is associated with cancer and premature aging when defective. Our two-hybrid screen utilizing Apc5 as bait recovered the lifespan determinant Fob1 as prey. Fob1 is unstable specifically in G1, cycles throughout the cell cycle in a manner similar to Clb2 (an APC target), and is stabilized in APC (apc5(CA)) and proteasome (rpn10) mutants. Deletion of FOB1 increased replicative lifespan (RLS) in wild type (WT), apc5(CA), and apc10 cells, and suppressed apc5(CA) cell cycle progression and rDNA recombination defects. Alternatively, increased FOB1 expression decreased RLS in WT cells, but did not reduce the already short apc5(CA) RLS, suggesting an epistatic interaction between apc5(CA) and fob1. Mutation to a putative L-Box (Fob1(E420V)), a Destruction Box-like motif, abolished Fob1 modifications, stabilized the protein, and increased rDNA recombination. Our work provides a mechanistic role played by the APC to promote replicative longevity and genomic stability in yeast.
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20
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Whitfield ZJ, Chisholm J, Hawley RS, Orr-Weaver TL. A meiosis-specific form of the APC/C promotes the oocyte-to-embryo transition by decreasing levels of the Polo kinase inhibitor matrimony. PLoS Biol 2013; 11:e1001648. [PMID: 24019759 PMCID: PMC3760765 DOI: 10.1371/journal.pbio.1001648] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 07/23/2013] [Indexed: 11/23/2022] Open
Abstract
During the oocyte-to-embryo transition in Drosophila, degradation of the Polo kinase inhibitor, Matrimony, depends on Cortex, a meiosis-specific form of the Anaphase Promoting Complex/Cyclosome that is required for the oocyte's normal transition from meiosis to mitosis. Oocytes are stockpiled with proteins and mRNA that are required to drive the initial mitotic divisions of embryogenesis. But are there proteins specific to meiosis whose levels must be decreased to begin embryogenesis properly? The Drosophila protein Cortex (Cort) is a female, meiosis-specific activator of the Anaphase Promoting Complex/Cyclosome (APC/C), an E3 ubiquitin ligase. We performed immunoprecipitation of Cortex followed by mass spectrometry, and identified the Polo kinase inhibitor Matrimony (Mtrm) as a potential interactor with Cort. In vitro binding assays showed Mtrm and Cort can bind directly. We found Mtrm protein levels to be reduced dramatically during the oocyte-to-embryo transition, and this downregulation did not take place in cort mutant eggs, consistent with Mtrm being a substrate of APCCort. We showed that Mtrm is subject to APCCort-mediated proteasomal degradation and have identified a putative APC/C recognition motif in Mtrm that when mutated partially stabilized the protein in the embryo. Furthermore, overexpression of Mtrm in the early embryo caused aberrant nuclear divisions and developmental defects, and these were enhanced by decreasing levels of active Polo. These data indicate APCCort ubiquitylates Mtrm at the oocyte-to-embryo transition, thus preventing excessive inhibition of Polo kinase activity due to Mtrm's presence. Despite their many differences, the meiotic and mitotic divisions of the early embryo take place within the same cytoplasmic space. The oocyte-to-embryo transition is the process by which an oocyte, which initially undergoes meiosis, becomes “adapted” to support the rapid mitotic divisions of embryogenesis. This involves fertilization as well as the stockpiling of proteins and mRNA for the transcriptionally silent early embryo. The Anaphase Promoting Complex/Cyclosome (APC/C) is a large protein complex that is active during both mitosis and meiosis and is responsible for targeting certain proteins for degradation. The discovery of the existence of APC/C activators that are present only during meiosis hinted at the possibility that this complex also functions to regulate protein degradation during the oocyte-to-embryo transition. Here we study Cortex, a female- and meiosis-specific activator of the APC/C in the fruit fly Drosophila melanogaster. We find that Cortex activity is necessary for the degradation of Matrimony, a key regulator of female meiosis in Drosophila. Matrimony itself inhibits Polo kinase, another important regulator of both mitosis and meiosis that also functions in chromosome segregation, centrosome dynamics, and cytokinesis. When excess Matrimony protein is not removed from the early embryo, developmental defects arise. Together our findings demonstrate that the precise regulation of Matrimony levels in the egg is necessary for the switch from meiosis to mitosis.
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Affiliation(s)
- Zachary J. Whitfield
- Whitehead Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Jennifer Chisholm
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - R. Scott Hawley
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Terry L. Orr-Weaver
- Whitehead Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- * E-mail:
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21
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Abstract
During meiosis, two consecutive rounds of chromosome segregation yield four haploid gametes from one diploid cell. The Polo kinase Cdc5 is required for meiotic progression, but how Cdc5 coordinates multiple cell-cycle events during meiosis I is not understood. Here we show that CDC5-dependent phosphorylation of Rec8, a subunit of the cohesin complex that links sister chromatids, is required for efficient cohesin removal from chromosome arms, which is a prerequisite for meiosis I chromosome segregation. CDC5 also establishes conditions for centromeric cohesin removal during meiosis II by promoting the degradation of Spo13, a protein that protects centromeric cohesin during meiosis I. Despite CDC5's central role in meiosis I, the protein kinase is dispensable during meiosis II and does not even phosphorylate its meiosis I targets during the second meiotic division. We conclude that Cdc5 has evolved into a master regulator of the unique meiosis I chromosome segregation pattern.
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22
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He J, Chao W, Zhang Z, Yang J, Cronin N, Barford D. Insights into degron recognition by APC/C coactivators from the structure of an Acm1-Cdh1 complex. Mol Cell 2013; 50:649-60. [PMID: 23707760 PMCID: PMC3690534 DOI: 10.1016/j.molcel.2013.04.024] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 03/05/2013] [Accepted: 04/15/2013] [Indexed: 12/14/2022]
Abstract
The anaphase-promoting complex/cyclosome (APC/C) regulates sister chromatid segregation and the exit from mitosis. Selection of most APC/C substrates is controlled by coactivator subunits (either Cdc20 or Cdh1) that interact with substrate destruction motifs--predominantly the destruction (D) box and KEN box degrons. How coactivators recognize D box degrons and how this is inhibited by APC/C regulatory proteins is not defined at the atomic level. Here, from the crystal structure of S. cerevisiae Cdh1 in complex with its specific inhibitor Acm1, which incorporates D and KEN box pseudosubstrate motifs, we describe the molecular basis for D box recognition. Additional interactions between Acm1 and Cdh1 identify a third protein-binding site on Cdh1 that is likely to confer coactivator-specific protein functions including substrate association. We provide a structural rationalization for D box and KEN box recognition by coactivators and demonstrate that many noncanonical APC/C degrons bind APC/C coactivators at the D box coreceptor.
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Affiliation(s)
- Jun He
- Division of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK
| | - William C.H. Chao
- Division of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK
| | - Ziguo Zhang
- Division of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK
| | - Jing Yang
- Division of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK
| | - Nora Cronin
- Division of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK
| | - David Barford
- Division of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK
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23
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Holt LJ. Regulatory modules: Coupling protein stability to phopshoregulation during cell division. FEBS Lett 2012; 586:2773-7. [PMID: 22664379 DOI: 10.1016/j.febslet.2012.05.045] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 05/23/2012] [Accepted: 05/23/2012] [Indexed: 11/28/2022]
Abstract
Multiple post-translational regulation systems regulate cell biology. Two key mechanisms that coordinate the myriad processes of cell replication are phosphorylation and ubiquitin-mediated degradation of proteins. Regulatory modules have evolved to integrate these two control systems at key decision points in the cell division cycle. These modules enable information to be processed with high fidelity by filtering noise, improving specificity, generating feedback loops, and optimizing spatiotemporal coordination of cellular processes. This review provides examples of these modules and considers the advantages of this signaling nexus.
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Affiliation(s)
- Liam J Holt
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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24
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Barford D. Structural insights into anaphase-promoting complex function and mechanism. Philos Trans R Soc Lond B Biol Sci 2012; 366:3605-24. [PMID: 22084387 DOI: 10.1098/rstb.2011.0069] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The anaphase-promoting complex or cyclosome (APC/C) controls sister chromatid segregation and the exit from mitosis by catalysing the ubiquitylation of cyclins and other cell cycle regulatory proteins. This unusually large E3 RING-cullin ubiquitin ligase is assembled from 13 different proteins. Selection of APC/C targets is controlled through recognition of short destruction motifs, predominantly the D box and KEN box. APC/C-mediated coordination of cell cycle progression is achieved through the temporal regulation of APC/C activity and substrate specificity, exerted through a combination of co-activator subunits, reversible phosphorylation and inhibitory proteins and complexes. Recent structural and biochemical studies of the APC/C are beginning to reveal an understanding of the roles of individual APC/C subunits and co-activators and how they mutually interact to mediate APC/C functions. This review focuses on the findings showing how information on the structural organization of the APC/C provides insights into the role of co-activators and core APC/C subunits in mediating substrate recognition. Mechanisms of regulating and modulating substrate recognition are discussed in the context of controlling the binding of the co-activator to the APC/C, and the accessibility and conformation of the co-activator when bound to the APC/C.
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Affiliation(s)
- David Barford
- Division of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK.
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25
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Tsuchiya D, Gonzalez C, Lacefield S. The spindle checkpoint protein Mad2 regulates APC/C activity during prometaphase and metaphase of meiosis I in Saccharomyces cerevisiae. Mol Biol Cell 2011; 22:2848-61. [PMID: 21697504 PMCID: PMC3154881 DOI: 10.1091/mbc.e11-04-0378] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The spindle checkpoint protein Mad2 sets the duration of meiosis I by down-regulating APC/C activity to ensure the timely degradation of APC/C substrates. In the absence of Mad2, premature APC/C activity can cause misregulation of meiotic cell cycle events, resulting in chromosome missegregation. In many eukaryotes, disruption of the spindle checkpoint protein Mad2 results in an increase in meiosis I nondisjunction, suggesting that Mad2 has a conserved role in ensuring faithful chromosome segregation in meiosis. To characterize the meiotic function of Mad2, we analyzed individual budding yeast cells undergoing meiosis. We find that Mad2 sets the duration of meiosis I by regulating the activity of APCCdc20. In the absence of Mad2, most cells undergo both meiotic divisions, but securin, a substrate of the APC/C, is degraded prematurely, and prometaphase I/metaphase I is accelerated. Some mad2Δ cells have a misregulation of meiotic cell cycle events and undergo a single aberrant division in which sister chromatids separate. In these cells, both APCCdc20 and APCAma1 are prematurely active, and meiosis I and meiosis II events occur in a single meiotic division. We show that Mad2 indirectly regulates APCAma1 activity by decreasing APCCdc20 activity. We propose that Mad2 is an important meiotic cell cycle regulator that ensures the timely degradation of APC/C substrates and the proper orchestration of the meiotic divisions.
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Affiliation(s)
- Dai Tsuchiya
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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26
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McLean JR, Chaix D, Ohi MD, Gould KL. State of the APC/C: organization, function, and structure. Crit Rev Biochem Mol Biol 2011; 46:118-36. [PMID: 21261459 DOI: 10.3109/10409238.2010.541420] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The ubiquitin-proteasome protein degradation system is involved in many essential cellular processes including cell cycle regulation, cell differentiation, and the unfolded protein response. The anaphase-promoting complex/cyclosome (APC/C), an evolutionarily conserved E3 ubiquitin ligase, was discovered 15 years ago because of its pivotal role in cyclin degradation and mitotic progression. Since then, we have learned that the APC/C is a very large, complex E3 ligase composed of 13 subunits, yielding a molecular machine of approximately 1 MDa. The intricate regulation of the APC/C is mediated by the Cdc20 family of activators, pseudosubstrate inhibitors, protein kinases and phosphatases and the spindle assembly checkpoint. The large size, complexity, and dynamic nature of the APC/C represent significant obstacles toward high-resolution structural techniques; however, over the last decade, there have been a number of lower resolution APC/C structures determined using single particle electron microscopy. These structures, when combined with data generated from numerous genetic and biochemical studies, have begun to shed light on how APC/C activity is regulated. Here, we discuss the most recent developments in the APC/C field concerning structure, substrate recognition, and catalysis.
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Affiliation(s)
- Janel R McLean
- Howard Hughes Medical Institute, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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Abstract
AbstractThe complex molecular events responsible for coordinating chromosome replication and segregation with cell division and growth are collectively known as the cell cycle. Progression through the cell cycle is orchestrated by the interplay between controlled protein synthesis and degradation and protein phosphorylation. Protein degradation is primarily regulated through the ubiquitin proteasome system, mediated by two related E3 protein ubiquitin ligases, the Skp1 cullin F-box (SCF) and the anaphase promoting complex (also known as the cyclosome) (APC/C). The APC/C is a multi-subunit cullin-RING E3 ubiquitin ligase that regulates progression through the mitotic phase of the cell cycle and controls entry into S phase by catalysing the ubiquitylation of cyclins and other cell cycle regulatory proteins. Selection of APC/C targets is controlled through recognition of short destruction motifs, predominantly the D-box and KEN-box. APC/C-mediated coordination of cell cycle progression is achieved through the temporal regulation of APC/C activity and substrate specificity, exerted through a combination of co-activator subunits, reversible phosphorylation and inhibitory proteins and complexes. The aim of this article is to discuss the APC/C from a structural and mechanistic perspective. Although an atomic structure of the APC/C is still lacking, a combination of genetic, biochemical, electron microscopy studies of intact APC/C and crystallographic analysis of individual subunits, together with analogies to evolutionarily related E3 ligases of the RING family, has provided deep insights into the molecular mechanisms of catalysis and substrate recognition, and structural organisation of the APC/C.
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Mitotic expression of Spo13 alters M-phase progression and nucleolar localization of Cdc14 in budding yeast. Genetics 2010; 185:841-54. [PMID: 20407133 DOI: 10.1534/genetics.109.113746] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Spo13 is a key meiosis-specific regulator required for centromere cohesion and coorientation, and for progression through two nuclear divisions. We previously reported that it causes a G2/M arrest and may delay the transition from late anaphase to G1, when overexpressed in mitosis. Yet its mechanism of action has remained elusive. Here we show that Spo13, which is phosphorylated and stabilized at G2/M in a Cdk/Clb-dependent manner, acts at two stages during mitotic cell division. Spo13 provokes a G2/M arrest that is reversible and largely independent of the Mad2 spindle checkpoint. Since mRNAs whose induction requires Cdc14 activation are reduced, we propose that its anaphase delay results from inhibition of Cdc14 function. Indeed, the Spo13-induced anaphase delay correlates with Cdc14 phosphatase retention in the nucleolus and with cyclin B accumulation, which both impede anaphase exit. At the onset of arrest, Spo13 is primarily associated with the nucleolus, where Cdc14 accumulates. Significantly, overexpression of separase (Esp1), which promotes G2/M and anaphase progression, suppresses Spo13 effects in mitosis, arguing that Spo13 acts upstream or parallel to Esp1. Given that Spo13 overexpression reduces Pds1 and cyclin B degradation, our findings are consistent with a role for Spo13 in regulating APC, which controls both G2/M and anaphase. Similar effects of Spo13 during meiotic MI may prevent cell cycle exit and initiation of DNA replication prior to MII, thereby ensuring two successive chromosome segregation events without an intervening S phase.
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Matyskiela ME, Rodrigo-Brenni MC, Morgan DO. Mechanisms of ubiquitin transfer by the anaphase-promoting complex. J Biol 2010; 8:92. [PMID: 19874575 PMCID: PMC2790831 DOI: 10.1186/jbiol184] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The anaphase-promoting complex (APC) is a ubiquitin-protein ligase required for the completion of mitosis in all eukaryotes. Recent mechanistic studies reveal how this remarkable enzyme combines specificity in substrate binding with flexibility in ubiquitin transfer, thereby allowing the modification of multiple lysines on the substrate as well as specific lysines on ubiquitin itself.
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Affiliation(s)
- Mary E Matyskiela
- Department of Physiology, University of California, San Francisco, CA 94158, USA
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Wäsch R, Robbins JA, Cross FR. The emerging role of APC/CCdh1 in controlling differentiation, genomic stability and tumor suppression. Oncogene 2009; 29:1-10. [PMID: 19826416 DOI: 10.1038/onc.2009.325] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Deregulation of the G1/G0 phase of the cell cycle can lead to cancer. During G1, most cells commit alternatively to DNA replication and division, or to cell-cycle exit and differentiation. The anaphase-promoting complex or cyclosome (APC/C) activated by Cdh1 coordinately eliminates positive cell-cycle regulators as well as inhibitors of differentiation, thereby coupling cell-cycle exit and differentiation. Misregulation of Cdh1 thus has the potential to promote both cell-cycle re-entry and either perturbed differentiation or dedifferentiation. In addition, APC/C(Cdh1) is required to maintain genomic stability. As a result, loss of Cdh1 can contribute to tumorigenesis in the form of proliferation of poorly differentiated and genetically unstable cells.
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Affiliation(s)
- R Wäsch
- Department of Hematology and Oncology, University Medical Center, Freiburg, Germany.
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Matyskiela ME, Morgan DO. Analysis of activator-binding sites on the APC/C supports a cooperative substrate-binding mechanism. Mol Cell 2009; 34:68-80. [PMID: 19362536 DOI: 10.1016/j.molcel.2009.02.027] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2008] [Revised: 01/21/2009] [Accepted: 02/24/2009] [Indexed: 12/13/2022]
Abstract
The anaphase-promoting complex or cyclosome (APC/C) is a ubiquitin ligase essential for the completion of mitosis in all eukaryotic cells. Substrates are recruited to the APC/C by activator proteins (Cdc20 or Cdh1), but it is not known where substrates are bound during catalysis. We explored this problem by analyzing mutations in the tetratricopeptide-repeat-containing APC/C subunits. We identified residues in Cdc23 and Cdc27 that are required for APC/C binding to Cdc20 and Cdh1 and for APC/C function in vivo. Mutation of these sites increased the rate of activator dissociation from the APC/C but did not affect reaction processivity, suggesting that the mutations have little effect on substrate dissociation from the active site. Further studies revealed that activator dissociation from the APC/C is inhibited by substrate, and that substrates are not bound solely to activator during catalysis but interact bivalently with an additional binding site on the APC/C core.
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Affiliation(s)
- Mary E Matyskiela
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94158, USA
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Choi E, Dial JM, Jeong DE, Hall MC. Unique D box and KEN box sequences limit ubiquitination of Acm1 and promote pseudosubstrate inhibition of the anaphase-promoting complex. J Biol Chem 2008; 283:23701-10. [PMID: 18596038 PMCID: PMC3259782 DOI: 10.1074/jbc.m803695200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 07/01/2008] [Indexed: 12/15/2022] Open
Abstract
The anaphase-promoting complex (APC) regulates cell division in eukaryotes by targeting specific proteins for destruction. APC substrates generally contain one or more short degron sequences that help mediate their recognition and poly-ubiquitination by the APC. The most common and well characterized degrons are the destruction box (D box) and the KEN box. The budding yeast Acm1 protein, an inhibitor of Cdh1-activated APC (APC(Cdh1)) also contains several conserved D and KEN boxes, and here we report that two of these located in the central region of Acm1 constitute a pseudosubstrate sequence required for APC(Cdh1) inhibition. Acm1 interacted with and inhibited substrate binding to the WD40 repeat domain of Cdh1. Combined mutation of the central D and KEN boxes strongly reduced both binding to the Cdh1 WD40 domain and APC(Cdh1) inhibition. Despite this, the double mutant, but not wild-type Acm1, was poly-ubiquitinated by APC(Cdh1) in vitro. Thus, unlike substrates in which D and KEN boxes promote ubiquitination, these same elements in the central region of Acm1 prevent ubiquitination. We propose that this unique property of the Acm1 degron sequences results from an unusually high affinity interaction with the substrate receptor site on the WD40 domain of Cdh1 that may serve both to promote APC inhibition and protect Acm1 from destruction.
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Affiliation(s)
- Eunyoung Choi
- Biochemistry Department and
Purdue Cancer Center, Purdue University, West
Lafayette, Indiana 47907 and the Department of
Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North
Carolina 27599
| | - J. Michael Dial
- Biochemistry Department and
Purdue Cancer Center, Purdue University, West
Lafayette, Indiana 47907 and the Department of
Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North
Carolina 27599
| | - Dah-Eun Jeong
- Biochemistry Department and
Purdue Cancer Center, Purdue University, West
Lafayette, Indiana 47907 and the Department of
Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North
Carolina 27599
| | - Mark C. Hall
- Biochemistry Department and
Purdue Cancer Center, Purdue University, West
Lafayette, Indiana 47907 and the Department of
Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North
Carolina 27599
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Abstract
Following chromosome duplication in S phase of the cell cycle, the sister chromatids are linked by cohesin. At the onset of anaphase, separase cleaves cohesin and thereby initiates sister chromatid separation. Separase activation results from the destruction of its inhibitor, securin, which is triggered by a ubiquitin ligase called the anaphase-promoting complex (APC). Here, we show in budding yeast that securin destruction and, thus, separase activation are not sufficient for the efficient segregation of the repetitive ribosomal DNA (rDNA). We find that rDNA segregation also requires the APC-mediated destruction of the S-phase cyclin Clb5, an activator of the protein kinase Cdk1. Mutations that prevent Clb5 destruction are lethal and cause defects in rDNA segregation and DNA synthesis. These defects are distinct from the mitotic-exit defects caused by stabilization of the mitotic cyclin Clb2, emphasizing the importance of cyclin specificity in the regulation of late-mitotic events. Efficient rDNA segregation, both in mitosis and meiosis, also requires APC-dependent destruction of Dbf4, an activator of the protein kinase Cdc7. We speculate that the dephosphorylation of Clb5-specific Cdk1 substrates and Dbf4-Cdc7 substrates drives the resolution of rDNA in early anaphase. The coincident destruction of securin, Clb5, and Dbf4 coordinates bulk chromosome segregation with segregation of rDNA.
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Abstract
The final stages of mitosis begin in anaphase, when the mitotic spindle segregates the duplicated chromosomes. Mitotic exit is then completed by disassembly of the spindle and packaging of chromosomes into daughter nuclei. The successful completion of mitosis requires that these events occur in a strict order. Two main mechanisms govern progression through late mitosis: dephosphorylation of cyclin-dependent kinase (Cdk) substrates and destruction of the substrates of the anaphase-promoting complex (APC). Here, we discuss the hypothesis that the order of late mitotic events depends, at least in part, on the order in which different Cdk and APC substrates are dephosphorylated or destroyed, respectively.
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Affiliation(s)
- Matt Sullivan
- Department of Physiology, University of California, 600 16th Street, San Francisco, California 94158-2517, USA
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