1
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Jones RM, Reynolds-Winczura A, Gambus A. A Decade of Discovery-Eukaryotic Replisome Disassembly at Replication Termination. BIOLOGY 2024; 13:233. [PMID: 38666845 PMCID: PMC11048390 DOI: 10.3390/biology13040233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 03/23/2024] [Accepted: 03/25/2024] [Indexed: 04/28/2024]
Abstract
The eukaryotic replicative helicase (CMG complex) is assembled during DNA replication initiation in a highly regulated manner, which is described in depth by other manuscripts in this Issue. During DNA replication, the replicative helicase moves through the chromatin, unwinding DNA and facilitating nascent DNA synthesis by polymerases. Once the duplication of a replicon is complete, the CMG helicase and the remaining components of the replisome need to be removed from the chromatin. Research carried out over the last ten years has produced a breakthrough in our understanding, revealing that replication termination, and more specifically replisome disassembly, is indeed a highly regulated process. This review brings together our current understanding of these processes and highlights elements of the mechanism that are conserved or have undergone divergence throughout evolution. Finally, we discuss events beyond the classic termination of DNA replication in S-phase and go over the known mechanisms of replicative helicase removal from chromatin in these particular situations.
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Affiliation(s)
- Rebecca M. Jones
- Institute of Cancer and Genomic Sciences, Birmingham Centre for Genome Biology, University of Birmingham, Birmingham B15 2TT, UK; (R.M.J.); (A.R.-W.)
- School of Biosciences, Aston University, Birmingham B4 7ET, UK
| | - Alicja Reynolds-Winczura
- Institute of Cancer and Genomic Sciences, Birmingham Centre for Genome Biology, University of Birmingham, Birmingham B15 2TT, UK; (R.M.J.); (A.R.-W.)
| | - Agnieszka Gambus
- Institute of Cancer and Genomic Sciences, Birmingham Centre for Genome Biology, University of Birmingham, Birmingham B15 2TT, UK; (R.M.J.); (A.R.-W.)
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2
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Tarcan Z, Poovathumkadavil D, Skagia A, Gambus A. The p97 segregase cofactor Ubxn7 facilitates replisome disassembly during S-phase. J Biol Chem 2022; 298:102234. [PMID: 35798141 PMCID: PMC9358472 DOI: 10.1016/j.jbc.2022.102234] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 06/22/2022] [Accepted: 06/23/2022] [Indexed: 11/20/2022] Open
Abstract
Complex cellular processes are driven by the regulated assembly and disassembly of large multiprotein complexes. While we are beginning to understand the molecular mechanism for assembly of the eukaryotic DNA replication machinery (replisome), we still know relatively little about the regulation of its disassembly at replication termination. Recently, the first elements of this process have emerged, revealing that the replicative helicase, at the heart of the replisome, is polyubiquitylated prior to unloading and that this unloading requires p97 segregase activity. Two different E3 ubiquitin ligases have now been shown to ubiquitylate the helicase under different conditions: Cul2Lrr1 and TRAIP. Here, using Xenopus laevis egg extract cell-free system and biochemical approaches, we have found two p97 cofactors, Ubxn7 and Faf1, which can interact with p97 during replisome disassembly during S-phase. We show only Ubxn7, however, facilitates efficient replisome disassembly. Ubxn7 delivers this role through its interaction via independent domains with both Cul2Lrr1 and p97 to allow coupling between Mcm7 ubiquitylation and its removal from chromatin. Our data therefore characterize Ubxn7 as the first substrate-specific p97 cofactor regulating replisome disassembly in vertebrates and a rationale for the efficacy of the Cul2Lrr1 replisome unloading pathway in unperturbed S-phase.
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3
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Benavidez JM, Kim JH, Greenwald I. Influences of HLH-2 stability on anchor cell fate specification during Caenorhabditis elegans gonadogenesis. G3 GENES|GENOMES|GENETICS 2022; 12:6520806. [PMID: 35134193 PMCID: PMC8982380 DOI: 10.1093/g3journal/jkac028] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 01/24/2022] [Indexed: 11/25/2022]
Abstract
The Caenorhabditis elegans E protein ortholog HLH-2 is required for the specification and function of the anchor cell, a unique, terminally differentiated somatic gonad cell that organizes uterine and vulval development. Initially, 4 cells—2 α cells and their sisters, the β cells—have the potential to be the sole anchor cell. The β cells rapidly lose anchor cell potential and invariably become ventral uterine precursor cells, while the 2 α cells interact via LIN-12/Notch to resolve which will be the anchor cell and which will become another ventral uterine precursor cell. HLH-2 protein stability is dynamically regulated in cells with anchor cell potential; initially present in all 4 cells, HLH-2 is degraded in presumptive ventral uterine precursor cells while remaining stable in the anchor cell. Here, we demonstrate that stability of HLH-2 protein is regulated by the activity of lin-12/Notch in both α and β cells. Our analysis provides evidence that activation of LIN-12 promotes degradation of HLH-2 as part of a negative feedback loop during the anchor cell/ventral uterine precursor cell decision by the α cells, and that absence of lin-12 activity in β cells increases HLH-2 stability and may account for their propensity to adopt the anchor cell fate in a lin-12 null background. We also performed an RNA interference screen of 232 ubiquitin-related genes and identified 7 genes that contribute to HLH-2 degradation in ventral uterine precursor cells; however, stabilizing HLH-2 by depleting ubiquitin ligases in a lin-12(+) background does not result in supernumerary anchor cells, suggesting that LIN-12 activation does not oppose hlh-2 activity solely by causing HLH-2 protein degradation. Finally, we provide evidence for lin-12-independent transcriptional regulation of hlh-2 in β cells that correlates with known differences in POP-1/TCF levels and anchor cell potential between α and β cells. Together, our results indicate that hlh-2 activity is regulated at multiple levels to restrict the anchor cell fate to a single cell.
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Affiliation(s)
- Justin M Benavidez
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Jee Hun Kim
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Iva Greenwald
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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4
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Xiong Y, Yu C, Zhang Q. Ubiquitin-Proteasome System-Regulated Protein Degradation in Spermatogenesis. Cells 2022; 11:1058. [PMID: 35326509 PMCID: PMC8947704 DOI: 10.3390/cells11061058] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/14/2022] [Accepted: 03/18/2022] [Indexed: 12/12/2022] Open
Abstract
Spermatogenesis is a prolonged and highly ordered physiological process that produces haploid male germ cells through more than 40 steps and experiences dramatic morphological and cellular transformations. The ubiquitin proteasome system (UPS) plays central roles in the precise control of protein homeostasis to ensure the effectiveness of certain protein groups at a given stage and the inactivation of them after this stage. Many UPS components have been demonstrated to regulate the progression of spermatogenesis at different levels. Especially in recent years, novel testis-specific proteasome isoforms have been identified to be essential and unique for spermatogenesis. In this review, we set out to discuss our current knowledge in functions of diverse USP components in mammalian spermatogenesis through: (1) the composition of proteasome isoforms at each stage of spermatogenesis; (2) the specificity of each proteasome isoform and the associated degradation events; (3) the E3 ubiquitin ligases mediating protein ubiquitination in male germ cells; and (4) the deubiquitinases involved in spermatogenesis and male fertility. Exploring the functions of UPS machineries in spermatogenesis provides a global picture of the proteome dynamics during male germ cell production and shed light on the etiology and pathogenesis of human male infertility.
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Affiliation(s)
- Yi Xiong
- Zhejiang University-University of Edinburgh Institute (ZJU-UoE Institute), Zhejiang University School of Medicine, International Campus, Zhejiang University, 718 East Haizhou Rd, Haining 314400, China;
| | - Chao Yu
- Key Laboratory of Reproductive Dysfunction Management of Zhejiang Province, Assisted Reproduction Unit, Department of Obstetrics and Gynecology, School of Medicine, Zhejiang University, Sir Run Run Shaw Hospital, 3 East Qing Chun Rd, Hangzhou 310020, China;
- College of Life Sciences, Zhejiang University, 866 Yuhangtang Rd, Hangzhou 310058, China
| | - Qianting Zhang
- Zhejiang University-University of Edinburgh Institute (ZJU-UoE Institute), Zhejiang University School of Medicine, International Campus, Zhejiang University, 718 East Haizhou Rd, Haining 314400, China;
- Department of Dermatology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou 310029, China
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5
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Xia Y, Fujisawa R, Deegan TD, Sonneville R, Labib KPM. TIMELESS-TIPIN and UBXN-3 promote replisome disassembly during DNA replication termination in Caenorhabditis elegans. EMBO J 2021; 40:e108053. [PMID: 34269473 PMCID: PMC8408604 DOI: 10.15252/embj.2021108053] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 06/10/2021] [Accepted: 06/11/2021] [Indexed: 12/30/2022] Open
Abstract
The eukaryotic replisome is rapidly disassembled during DNA replication termination. In metazoa, the cullin-RING ubiquitin ligase CUL-2LRR-1 drives ubiquitylation of the CMG helicase, leading to replisome disassembly by the p97/CDC-48 "unfoldase". Here, we combine in vitro reconstitution with in vivo studies in Caenorhabditis elegans embryos, to show that the replisome-associated TIMELESS-TIPIN complex is required for CUL-2LRR-1 recruitment and efficient CMG helicase ubiquitylation. Aided by TIMELESS-TIPIN, CUL-2LRR-1 directs a suite of ubiquitylation enzymes to ubiquitylate the MCM-7 subunit of CMG. Subsequently, the UBXN-3 adaptor protein directly stimulates the disassembly of ubiquitylated CMG by CDC-48_UFD-1_NPL-4. We show that UBXN-3 is important in vivo for replisome disassembly in the absence of TIMELESS-TIPIN. Correspondingly, co-depletion of UBXN-3 and TIMELESS causes profound synthetic lethality. Since the human orthologue of UBXN-3, FAF1, is a candidate tumour suppressor, these findings suggest that manipulation of CMG disassembly might be applicable to future strategies for treating human cancer.
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Affiliation(s)
- Yisui Xia
- The MRC Protein Phosphorylation and Ubiquitylation UnitSchool of Life SciencesUniversity of DundeeDundeeUK
| | - Ryo Fujisawa
- The MRC Protein Phosphorylation and Ubiquitylation UnitSchool of Life SciencesUniversity of DundeeDundeeUK
| | - Tom D Deegan
- The MRC Protein Phosphorylation and Ubiquitylation UnitSchool of Life SciencesUniversity of DundeeDundeeUK
| | - Remi Sonneville
- The MRC Protein Phosphorylation and Ubiquitylation UnitSchool of Life SciencesUniversity of DundeeDundeeUK
| | - Karim P M Labib
- The MRC Protein Phosphorylation and Ubiquitylation UnitSchool of Life SciencesUniversity of DundeeDundeeUK
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6
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Le TT, Ainsworth J, Polo Rivera C, Macartney T, Labib KP. Reconstitution of human CMG helicase ubiquitylation by CUL2LRR1 and multiple E2 enzymes. Biochem J 2021; 478:2825-2842. [PMID: 34195792 PMCID: PMC8331092 DOI: 10.1042/bcj20210315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 06/25/2021] [Accepted: 06/29/2021] [Indexed: 11/17/2022]
Abstract
Cullin ubiquitin ligases drive replisome disassembly during DNA replication termination. In worm, frog and mouse cells, CUL2LRR1 is required to ubiquitylate the MCM7 subunit of the CMG helicase. Here, we show that cullin ligases also drive CMG-MCM7 ubiquitylation in human cells, thereby making the helicase into a substrate for the p97 unfoldase. Using purified human proteins, including a panel of E2 ubiquitin-conjugating enzymes, we have reconstituted CMG helicase ubiquitylation, dependent upon neddylated CUL2LRR1. The reaction is highly specific to CMG-MCM7 and requires the LRR1 substrate targeting subunit, since replacement of LRR1 with the alternative CUL2 adaptor VHL switches ubiquitylation from CMG-MCM7 to HIF1. CUL2LRR1 firstly drives monoubiquitylation of CMG-MCM7 by the UBE2D class of E2 enzymes. Subsequently, CUL2LRR1 activates UBE2R1/R2 or UBE2G1/G2 to extend a single K48-linked ubiquitin chain on CMG-MCM7. Thereby, CUL2LRR1 converts CMG into a substrate for p97, which disassembles the ubiquitylated helicase during DNA replication termination.
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Affiliation(s)
- Thanh Thi Le
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Johanna Ainsworth
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Cristian Polo Rivera
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Thomas Macartney
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Karim P.M. Labib
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
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7
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Fan Y, Köberlin MS, Ratnayeke N, Liu C, Deshpande M, Gerhardt J, Meyer T. LRR1-mediated replisome disassembly promotes DNA replication by recycling replisome components. J Cell Biol 2021; 220:212186. [PMID: 34037657 PMCID: PMC8160578 DOI: 10.1083/jcb.202009147] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 03/30/2021] [Accepted: 05/04/2021] [Indexed: 11/22/2022] Open
Abstract
After two converging DNA replication forks meet, active replisomes are disassembled and unloaded from chromatin. A key process in replisome disassembly is the unloading of CMG helicases (CDC45–MCM–GINS), which is initiated in Caenorhabditis elegans and Xenopus laevis by the E3 ubiquitin ligase CRL2LRR1. Here, we show that human cells lacking LRR1 fail to unload CMG helicases and accumulate increasing amounts of chromatin-bound replisome components as cells progress through S phase. Markedly, we demonstrate that the failure to disassemble replisomes reduces the rate of DNA replication increasingly throughout S phase by sequestering rate-limiting replisome components on chromatin and blocking their recycling. Continued binding of CMG helicases to chromatin during G2 phase blocks mitosis by activating an ATR-mediated G2/M checkpoint. Finally, we provide evidence that LRR1 is an essential gene for human cell division, suggesting that CRL2LRR1 enzyme activity is required for the proliferation of cancer cells and is thus a potential target for cancer therapy.
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Affiliation(s)
- Yilin Fan
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA.,Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY
| | - Marielle S Köberlin
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA
| | - Nalin Ratnayeke
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA.,Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY
| | - Chad Liu
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA
| | - Madhura Deshpande
- Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY
| | - Jeannine Gerhardt
- Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY.,Department of Obstetrics and Gynecology, Weill Cornell Medicine, New York, NY
| | - Tobias Meyer
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA.,Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY
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8
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Replication stress promotes cell elimination by extrusion. Nature 2021; 593:591-596. [PMID: 33953402 DOI: 10.1038/s41586-021-03526-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 04/09/2021] [Indexed: 01/21/2023]
Abstract
Cell extrusion is a mechanism of cell elimination that is used by organisms as diverse as sponges, nematodes, insects and mammals1-3. During extrusion, a cell detaches from a layer of surrounding cells while maintaining the continuity of that layer4. Vertebrate epithelial tissues primarily eliminate cells by extrusion, and the dysregulation of cell extrusion has been linked to epithelial diseases, including cancer1,5. The mechanisms that drive cell extrusion remain incompletely understood. Here, to analyse cell extrusion by Caenorhabditis elegans embryos3, we conducted a genome-wide RNA interference screen, identified multiple cell-cycle genes with S-phase-specific function, and performed live-imaging experiments to establish how those genes control extrusion. Extruding cells experience replication stress during S phase and activate a replication-stress response via homologues of ATR and CHK1. Preventing S-phase entry, inhibiting the replication-stress response, or allowing completion of the cell cycle blocked cell extrusion. Hydroxyurea-induced replication stress6,7 triggered ATR-CHK1- and p53-dependent cell extrusion from a mammalian epithelial monolayer. We conclude that cell extrusion induced by replication stress is conserved among animals and propose that this extrusion process is a primordial mechanism of cell elimination with a tumour-suppressive function in mammals.
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9
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Hefel A, Honda M, Cronin N, Harrell K, Patel P, Spies M, Smolikove S. RPA complexes in Caenorhabditis elegans meiosis; unique roles in replication, meiotic recombination and apoptosis. Nucleic Acids Res 2021; 49:2005-2026. [PMID: 33476370 PMCID: PMC7913698 DOI: 10.1093/nar/gkaa1293] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 12/24/2020] [Accepted: 12/29/2020] [Indexed: 12/20/2022] Open
Abstract
Replication Protein A (RPA) is a critical complex that acts in replication and promotes homologous recombination by allowing recombinase recruitment to processed DSB ends. Most organisms possess three RPA subunits (RPA1, RPA2, RPA3) that form a trimeric complex critical for viability. The Caenorhabditis elegans genome encodes RPA-1, RPA-2 and an RPA-2 paralog RPA-4. In our analysis, we determined that RPA-2 is critical for germline replication and normal repair of meiotic DSBs. Interestingly, RPA-1 but not RPA-2 is essential for somatic replication, in contrast to other organisms that require both subunits. Six different hetero- and homodimeric complexes containing permutations of RPA-1, RPA-2 and RPA-4 can be detected in whole animal extracts. Our in vivo studies indicate that RPA-1/4 dimer is less abundant in the nucleus and its formation is inhibited by RPA-2. While RPA-4 does not participate in replication or recombination, we find that RPA-4 inhibits RAD-51 filament formation and promotes apoptosis of a subset of damaged nuclei. Altogether these findings point to sub-functionalization and antagonistic roles of RPA complexes in C. elegans.
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Affiliation(s)
- Adam Hefel
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
| | - Masayoshi Honda
- Department of Biochemistry, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Nicholas Cronin
- Department of Biochemistry, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Kailey Harrell
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
| | - Pooja Patel
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
| | - Maria Spies
- Department of Biochemistry, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Sarit Smolikove
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
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10
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Villa F, Fujisawa R, Ainsworth J, Nishimura K, Lie‐A‐Ling M, Lacaud G, Labib KPM. CUL2 LRR1 , TRAIP and p97 control CMG helicase disassembly in the mammalian cell cycle. EMBO Rep 2021; 22:e52164. [PMID: 33590678 PMCID: PMC7926238 DOI: 10.15252/embr.202052164] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 12/16/2020] [Accepted: 01/07/2021] [Indexed: 11/26/2022] Open
Abstract
The eukaryotic replisome is disassembled in each cell cycle, dependent upon ubiquitylation of the CMG helicase. Studies of Saccharomyces cerevisiae, Caenorhabditis elegans and Xenopus laevis have revealed surprising evolutionary diversity in the ubiquitin ligases that control CMG ubiquitylation, but regulated disassembly of the mammalian replisome has yet to be explored. Here, we describe a model system for studying the ubiquitylation and chromatin extraction of the mammalian CMG replisome, based on mouse embryonic stem cells. We show that the ubiquitin ligase CUL2LRR1 is required for ubiquitylation of the CMG-MCM7 subunit during S-phase, leading to disassembly by the p97 ATPase. Moreover, a second pathway of CMG disassembly is activated during mitosis, dependent upon the TRAIP ubiquitin ligase that is mutated in primordial dwarfism and mis-regulated in various cancers. These findings indicate that replisome disassembly in diverse metazoa is regulated by a conserved pair of ubiquitin ligases, distinct from those present in other eukaryotes.
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Affiliation(s)
- Fabrizio Villa
- The MRC Protein Phosphorylation and Ubiquitylation UnitSchool of Life SciencesUniversity of DundeeDundeeUK
| | - Ryo Fujisawa
- The MRC Protein Phosphorylation and Ubiquitylation UnitSchool of Life SciencesUniversity of DundeeDundeeUK
| | - Johanna Ainsworth
- The MRC Protein Phosphorylation and Ubiquitylation UnitSchool of Life SciencesUniversity of DundeeDundeeUK
| | - Kohei Nishimura
- The MRC Protein Phosphorylation and Ubiquitylation UnitSchool of Life SciencesUniversity of DundeeDundeeUK
- Division of Biological ScienceGraduate School of ScienceNagoya UniversityNagoyaJapan
| | - Michael Lie‐A‐Ling
- Cancer Research U.K. Manchester InstituteThe University of ManchesterAlderley ParkUK
| | - Georges Lacaud
- Cancer Research U.K. Manchester InstituteThe University of ManchesterAlderley ParkUK
| | - Karim PM Labib
- The MRC Protein Phosphorylation and Ubiquitylation UnitSchool of Life SciencesUniversity of DundeeDundeeUK
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11
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Pérez-Arnaiz P, Dattani A, Smith V, Allers T. Haloferax volcanii-a model archaeon for studying DNA replication and repair. Open Biol 2020; 10:200293. [PMID: 33259746 PMCID: PMC7776575 DOI: 10.1098/rsob.200293] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 11/09/2020] [Indexed: 12/16/2022] Open
Abstract
The tree of life shows the relationship between all organisms based on their common ancestry. Until 1977, it comprised two major branches: prokaryotes and eukaryotes. Work by Carl Woese and other microbiologists led to the recategorization of prokaryotes and the proposal of three primary domains: Eukarya, Bacteria and Archaea. Microbiological, genetic and biochemical techniques were then needed to study the third domain of life. Haloferax volcanii, a halophilic species belonging to the phylum Euryarchaeota, has provided many useful tools to study Archaea, including easy culturing methods, genetic manipulation and phenotypic screening. This review will focus on DNA replication and DNA repair pathways in H. volcanii, how this work has advanced our knowledge of archaeal cellular biology, and how it may deepen our understanding of bacterial and eukaryotic processes.
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Affiliation(s)
| | | | | | - Thorsten Allers
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, UK
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12
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Sonneville R, Bhowmick R, Hoffmann S, Mailand N, Hickson ID, Labib K. TRAIP drives replisome disassembly and mitotic DNA repair synthesis at sites of incomplete DNA replication. eLife 2019; 8:e48686. [PMID: 31545170 PMCID: PMC6773462 DOI: 10.7554/elife.48686] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 09/20/2019] [Indexed: 11/13/2022] Open
Abstract
The faithful segregation of eukaryotic chromosomes in mitosis requires that the genome be duplicated completely prior to anaphase. However, cells with large genomes sometimes fail to complete replication during interphase and instead enter mitosis with regions of incompletely replicated DNA. These regions are processed in early mitosis via a process known as mitotic DNA repair synthesis (MiDAS), but little is known about how cells switch from conventional DNA replication to MiDAS. Using the early embryo of the nematode Caenorhabditis elegans as a model system, we show that the TRAIP ubiquitin ligase drives replisome disassembly in response to incomplete DNA replication, thereby providing access to replication forks for other factors. Moreover, TRAIP is essential for MiDAS in human cells, and is important in both systems to prevent mitotic segregation errors. Our data indicate that TRAIP is a master regulator of the processing of incomplete DNA replication during mitosis in metazoa.
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Affiliation(s)
- Remi Sonneville
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life SciencesUniversity of DundeeDundeeUnited Kingdom
| | - Rahul Bhowmick
- Department of Cellular and Molecular Medicine, Center for Chromosome StabilityUniversity of CopenhagenCopenhagenDenmark
| | - Saskia Hoffmann
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Niels Mailand
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Ian D Hickson
- Department of Cellular and Molecular Medicine, Center for Chromosome StabilityUniversity of CopenhagenCopenhagenDenmark
| | - Karim Labib
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life SciencesUniversity of DundeeDundeeUnited Kingdom
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13
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Developmental Control of the Cell Cycle: Insights from Caenorhabditis elegans. Genetics 2019; 211:797-829. [PMID: 30846544 PMCID: PMC6404260 DOI: 10.1534/genetics.118.301643] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Accepted: 10/10/2018] [Indexed: 12/11/2022] Open
Abstract
During animal development, a single fertilized egg forms a complete organism with tens to trillions of cells that encompass a large variety of cell types. Cell cycle regulation is therefore at the center of development and needs to be carried out in close coordination with cell differentiation, migration, and death, as well as tissue formation, morphogenesis, and homeostasis. The timing and frequency of cell divisions are controlled by complex combinations of external and cell-intrinsic signals that vary throughout development. Insight into how such controls determine in vivo cell division patterns has come from studies in various genetic model systems. The nematode Caenorhabditis elegans has only about 1000 somatic cells and approximately twice as many germ cells in the adult hermaphrodite. Despite the relatively small number of cells, C. elegans has diverse tissues, including intestine, nerves, striated and smooth muscle, and skin. C. elegans is unique as a model organism for studies of the cell cycle because the somatic cell lineage is invariant. Somatic cells divide at set times during development to produce daughter cells that adopt reproducible developmental fates. Studies in C. elegans have allowed the identification of conserved cell cycle regulators and provided insights into how cell cycle regulation varies between tissues. In this review, we focus on the regulation of the cell cycle in the context of C. elegans development, with reference to other systems, with the goal of better understanding how cell cycle regulation is linked to animal development in general.
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14
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Ulicna L, Rohozkova J, Hozak P. Multiple Aspects of PIP2 Involvement in C. elegans Gametogenesis. Int J Mol Sci 2018; 19:ijms19092679. [PMID: 30201859 PMCID: PMC6163852 DOI: 10.3390/ijms19092679] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 08/28/2018] [Accepted: 09/05/2018] [Indexed: 12/20/2022] Open
Abstract
One of the most studied phosphoinositides is phosphatidylinositol 4,5-bisphosphate (PIP2), which localizes to the plasma membrane, nuclear speckles, small foci in the nucleoplasm, and to the nucleolus in mammalian cells. Here, we show that PIP2 also localizes to the nucleus in prophase I, during the gametogenesis of C. elegans hermaphrodite. The depletion of PIP2 by type I PIP kinase (PPK-1) kinase RNA interference results in an altered chromosome structure and leads to various defects during meiotic progression. We observed a decreased brood size and aneuploidy in progeny, defects in synapsis, and crossover formation. The altered chromosome structure is reflected in the increased transcription activity of a tightly regulated process in prophase I. To elucidate the involvement of PIP2 in the processes during the C. elegans development, we identified the PIP2-binding partners, leucine-rich repeat (LRR-1) protein and proteasome subunit beta 4 (PBS-4), pointing to its involvement in the ubiquitin–proteasome pathway.
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Affiliation(s)
- Livia Ulicna
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Prague 142 20, Czech Republic.
| | - Jana Rohozkova
- Department of Epigenetics of the Cell Nucleus, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Division BIOCEV, Vestec 252 50, Czech Republic.
| | - Pavel Hozak
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Prague 142 20, Czech Republic.
- Department of Epigenetics of the Cell Nucleus, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Division BIOCEV, Vestec 252 50, Czech Republic.
- Microscopy Centre, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Prague 142 20, Czech Republic.
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15
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Jang SM, Redon CE, Aladjem MI. Chromatin-Bound Cullin-Ring Ligases: Regulatory Roles in DNA Replication and Potential Targeting for Cancer Therapy. Front Mol Biosci 2018; 5:19. [PMID: 29594129 PMCID: PMC5859106 DOI: 10.3389/fmolb.2018.00019] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 02/12/2018] [Indexed: 12/14/2022] Open
Abstract
Cullin-RING (Really Interesting New Gene) E3 ubiquitin ligases (CRLs), the largest family of E3 ubiquitin ligases, are functional multi-subunit complexes including substrate receptors, adaptors, cullin scaffolds, and RING-box proteins. CRLs are responsible for ubiquitination of ~20% of cellular proteins and are involved in diverse biological processes including cell cycle progression, genome stability, and oncogenesis. Not surprisingly, cullins are deregulated in many diseases and instances of cancer. Recent studies have highlighted the importance of CRL-mediated ubiquitination in the regulation of DNA replication/repair, including specific roles in chromatin assembly and disassembly of the replication machinery. The development of novel therapeutics targeting the CRLs that regulate the replication machinery and chromatin in cancer is now an attractive therapeutic strategy. In this review, we summarize the structure and assembly of CRLs and outline their cellular functions and their diverse roles in cancer, emphasizing the regulatory functions of nuclear CRLs in modulating the DNA replication machinery. Finally, we discuss the current strategies for targeting CRLs against cancer in the clinic.
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Affiliation(s)
| | | | - Mirit I. Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States
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16
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Wang S, Xia W, Qiu M, Wang X, Jiang F, Yin R, Xu L. Atlas on substrate recognition subunits of CRL2 E3 ligases. Oncotarget 2018; 7:46707-46716. [PMID: 27107416 PMCID: PMC5216831 DOI: 10.18632/oncotarget.8732] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 04/02/2016] [Indexed: 12/16/2022] Open
Abstract
The Cullin2-type ubiquitin ligases belong to the Cullin-Ring Ligase (CRL) family, which is a crucial determinant of proteasome-based degradation processes in eukaryotes. Because of the finding of von Hippel-Lindau tumor suppressor (VHL), the Cullin2-type ubiquitin ligases gain focusing in the research of many diseases, especially in tumors. These multisubunit enzymes are composed of the Ring finger protein, the Cullin2 scaffold protein, the Elongin B&C linker protein and the variant substrate recognition subunits (SRSs), among which the Cullin2 scaffold protein is the determining factor of the enzyme mechanism. Substrate recognition of Cullin2-type ubiquitin ligases depends on SRSs and results in the degradation of diseases associated substrates by intracellular signaling events. This review focuses on the diversity and the multifunctionality of SRSs in the Cullin2-type ubiquitin ligases, including VHL, LRR-1, FEM1b, PRAME and ZYG11. Recently, as more SRSs are being discovered and more aspects of substrate recognition have been illuminated, insight into the relationship between Cul2-dependent SRSs and substrates provides a new area for cancer research.
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Affiliation(s)
- Siwei Wang
- Department of Thoracic Surgery, Nanjing Medical University Affiliated Cancer Hospital, Jiangsu Key Laboratory of Molecular and Translational Cancer Research, Cancer Institute of Jiangsu Province, Nanjing, China.,The Fourth Clinical College of Nanjing Medical University, Nanjing, China
| | - Wenjia Xia
- Department of Thoracic Surgery, Nanjing Medical University Affiliated Cancer Hospital, Jiangsu Key Laboratory of Molecular and Translational Cancer Research, Cancer Institute of Jiangsu Province, Nanjing, China.,The Fourth Clinical College of Nanjing Medical University, Nanjing, China
| | - Mantang Qiu
- Department of Thoracic Surgery, Nanjing Medical University Affiliated Cancer Hospital, Jiangsu Key Laboratory of Molecular and Translational Cancer Research, Cancer Institute of Jiangsu Province, Nanjing, China.,The Fourth Clinical College of Nanjing Medical University, Nanjing, China
| | - Xin Wang
- Department of Thoracic Surgery, Nanjing Medical University Affiliated Cancer Hospital, Jiangsu Key Laboratory of Molecular and Translational Cancer Research, Cancer Institute of Jiangsu Province, Nanjing, China.,The Fourth Clinical College of Nanjing Medical University, Nanjing, China
| | - Feng Jiang
- Department of Thoracic Surgery, Nanjing Medical University Affiliated Cancer Hospital, Jiangsu Key Laboratory of Molecular and Translational Cancer Research, Cancer Institute of Jiangsu Province, Nanjing, China
| | - Rong Yin
- Department of Thoracic Surgery, Nanjing Medical University Affiliated Cancer Hospital, Jiangsu Key Laboratory of Molecular and Translational Cancer Research, Cancer Institute of Jiangsu Province, Nanjing, China
| | - Lin Xu
- Department of Thoracic Surgery, Nanjing Medical University Affiliated Cancer Hospital, Jiangsu Key Laboratory of Molecular and Translational Cancer Research, Cancer Institute of Jiangsu Province, Nanjing, China
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17
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Abstract
In this Outlook, Akopian and Rape discuss the Dewar et al. study in this issue, which identified an E3 ubiquitin ligase, CUL2LRR2, that modifies a subunit of the replicative CMG helicase and triggers disassembly of the replication machinery. Anomalies in dismantling the machinery of DNA replication can compromise genome integrity and contribute to tumorigenesis and aging. In this issue of Genes & Development, Dewar and colleagues (pp. 275–290) identified an E3 ubiquitin ligase, CUL2LRR2, that modifies a subunit of the replicative CMG (Cdc45, minichromosome maintenance [MCM] subunits 2–7, and the GINS complex) helicase and triggers disassembly of the replication machinery. Their study offers critical insight into the mechanism of DNA replication termination while at the same time raising important questions for future research.
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Affiliation(s)
- David Akopian
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, California 94720, USA.,Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA
| | - Michael Rape
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, California 94720, USA.,Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA
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18
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Abstract
Genome duplication is carried out by pairs of replication forks that assemble at origins of replication and then move in opposite directions. DNA replication ends when converging replication forks meet. During this process, which is known as replication termination, DNA synthesis is completed, the replication machinery is disassembled and daughter molecules are resolved. In this Review, we outline the steps that are likely to be common to replication termination in most organisms, namely, fork convergence, synthesis completion, replisome disassembly and decatenation. We briefly review the mechanism of termination in the bacterium Escherichia coli and in simian virus 40 (SV40) and also focus on recent advances in eukaryotic replication termination. In particular, we discuss the recently discovered E3 ubiquitin ligases that control replisome disassembly in yeast and higher eukaryotes, and how their activity is regulated to avoid genome instability.
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19
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20
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Sonneville R, Moreno SP, Knebel A, Johnson C, Hastie CJ, Gartner A, Gambus A, Labib K. CUL-2 LRR-1 and UBXN-3 drive replisome disassembly during DNA replication termination and mitosis. Nat Cell Biol 2017; 19:468-479. [PMID: 28368371 PMCID: PMC5410169 DOI: 10.1038/ncb3500] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 02/27/2017] [Indexed: 02/06/2023]
Abstract
Replisome disassembly is the final step of DNA replication in eukaryotes, involving the ubiquitylation and CDC48-dependent dissolution of the CMG helicase (CDC45-MCM-GINS). Using Caenorhabditis elegans early embryos and Xenopus laevis egg extracts, we show that the E3 ligase CUL-2LRR-1 associates with the replisome and drives ubiquitylation and disassembly of CMG, together with the CDC-48 cofactors UFD-1 and NPL-4. Removal of CMG from chromatin in frog egg extracts requires CUL2 neddylation, and our data identify chromatin recruitment of CUL2LRR1 as a key regulated step during DNA replication termination. Interestingly, however, CMG persists on chromatin until prophase in worms that lack CUL-2LRR-1, but is then removed by a mitotic pathway that requires the CDC-48 cofactor UBXN-3, orthologous to the human tumour suppressor FAF1. Partial inactivation of lrr-1 and ubxn-3 leads to synthetic lethality, suggesting future approaches by which a deeper understanding of CMG disassembly in metazoa could be exploited therapeutically.
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Affiliation(s)
- Remi Sonneville
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Sara Priego Moreno
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Axel Knebel
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Clare Johnson
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - C James Hastie
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Anton Gartner
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Agnieszka Gambus
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Karim Labib
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
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21
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Dewar JM, Low E, Mann M, Räschle M, Walter JC. CRL2 Lrr1 promotes unloading of the vertebrate replisome from chromatin during replication termination. Genes Dev 2017; 31:275-290. [PMID: 28235849 PMCID: PMC5358724 DOI: 10.1101/gad.291799.116] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Accepted: 01/30/2017] [Indexed: 01/26/2023]
Abstract
Here, Dewar et al. use a proteomic screen in Xenopus egg extracts to identify factors that are enriched on chromatin when CMG unloading from chromatin, which is a key event during eukaryotic replication termination, is blocked. Their results show that CRL2Lrr1 is a master regulator of replisome disassembly during vertebrate DNA replication termination. A key event during eukaryotic replication termination is the removal of the CMG helicase from chromatin. CMG unloading involves ubiquitylation of its Mcm7 subunit and the action of the p97 ATPase. Using a proteomic screen in Xenopus egg extracts, we identified factors that are enriched on chromatin when CMG unloading is blocked. This approach identified the E3 ubiquitin ligase CRL2Lrr1, a specific p97 complex, other potential regulators of termination, and many replisome components. We show that Mcm7 ubiquitylation and CRL2Lrr1 binding to chromatin are temporally linked and occur only during replication termination. In the absence of CRL2Lrr1, Mcm7 is not ubiquitylated, CMG unloading is inhibited, and a large subcomplex of the vertebrate replisome that includes DNA Pol ε is retained on DNA. Our data identify CRL2Lrr1 as a master regulator of replisome disassembly during vertebrate DNA replication termination.
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Affiliation(s)
- James M Dewar
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Emily Low
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Matthias Mann
- Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Markus Räschle
- Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.,Howard Hughes Medical Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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22
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Gambus A. Termination of Eukaryotic Replication Forks. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:163-187. [DOI: 10.1007/978-981-10-6955-0_8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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23
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RNAi-Based Suppressor Screens Reveal Genetic Interactions Between the CRL2LRR-1 E3-Ligase and the DNA Replication Machinery in Caenorhabditis elegans. G3-GENES GENOMES GENETICS 2016; 6:3431-3442. [PMID: 27543292 PMCID: PMC5068962 DOI: 10.1534/g3.116.033043] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Cullin-RING E3-Ligases (CRLs), the largest family of E3 ubiquitin-Ligases, regulate diverse cellular processes by promoting ubiquitination of target proteins. The evolutionarily conserved Leucine Rich Repeat protein 1 (LRR-1) is a substrate-recognition subunit of a CRL2LRR-1 E3-ligase. Here we provide genetic evidence supporting a role of this E3-enzyme in the maintenance of DNA replication integrity in Caenorhabditis elegans. Through RNAi-based suppressor screens of lrr-1(0) and cul-2(or209ts) mutants, we identified two genes encoding components of the GINS complex, which is part of the Cdc45-MCM-GINS (CMG) replicative helicase, as well as CDC-7 and MUS-101, which drives the assembly of the CMG helicase during DNA replication. In addition, we identified the core components of the ATR/ATL-1 DNA replication checkpoint pathway (MUS-101, ATL-1, CLSP-1, CHK-1). These results suggest that the CRL2LRR-1 E3-ligase acts to modify or degrade factor(s) that would otherwise misregulate the replisome, eventually leading to the activation of the DNA replication checkpoint.
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24
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Regulation of the MEI-1/MEI-2 Microtubule-Severing Katanin Complex in Early Caenorhabditis elegans Development. G3-GENES GENOMES GENETICS 2016; 6:3257-3268. [PMID: 27527792 PMCID: PMC5068946 DOI: 10.1534/g3.116.031666] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
After fertilization, rapid changes of the Caenorhabditis elegans cytoskeleton occur in the transition from meiosis to mitosis, requiring precise regulation. The MEI-1/MEI-2 katanin microtubule-severing complex is essential for meiotic spindle formation but must be quickly inactivated to allow for proper formation of the mitotic spindle. MEI-1/MEI-2 inactivation is dependent on multiple redundant pathways. The primary pathway employs the MEL-26 substrate adaptor for the CUL-3/cullin-based E3 ubiquitin ligase, which targets MEI-1 for proteosomal degradation. Here, we used quantitative antibody staining to measure MEI-1 levels to determine how other genes implicated in MEI-1 regulation act relative to CUL-3/MEL-26. The anaphase-promoting complex/cyclosome, APC/C, the DYRK (Dual-specificity tyrosine-regulated kinase), MBK-2, and the CUL-2-based E3 ubiquitin ligase act together to degrade MEI-1, in parallel to MEL-26/CUL-3. CUL-2 is known to keep MEL-26 low during meiosis, so CUL-2 apparently changes its target from MEL-26 in meiosis to MEI-1 in mitosis. RFL-1, an activator of cullin E3 ubiquitin ligases, activates CUL-2 but not CUL-3 for MEI-1 elimination. HECD-1 (HECT/Homologous to the E6AP carboxyl terminus domain) E3 ligase acts as a MEI-1 activator in meiosis but functions as an inhibitor during mitosis, without affecting levels of MEI-1 or MEI-2. Our results highlight the multiple layers of MEI-1 regulation that are required during the switch from the meiotic to mitotic modes of cell division.
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25
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Cai W, Yang H. The structure and regulation of Cullin 2 based E3 ubiquitin ligases and their biological functions. Cell Div 2016; 11:7. [PMID: 27222660 PMCID: PMC4878042 DOI: 10.1186/s13008-016-0020-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 05/11/2016] [Indexed: 11/23/2022] Open
Abstract
Background Cullin-RING E3 ubiquitin ligase complexes play a central role in targeting cellular proteins for ubiquitination-dependent protein turnover through 26S proteasome. Cullin-2 is a member of the Cullin family, and it serves as a scaffold protein for Elongin B and C, Rbx1 and various substrate recognition receptors to form E3 ubiquitin ligases. Main body of the abstract First, the composition, structure and the regulation of Cullin-2 based E3 ubiquitin ligases were introduced. Then the targets, the biological functions of complexes that use VHL, Lrr-1, Fem1b, Prame, Zyg-11, BAF250, Rack1 as substrate targeting subunits were described, and their involvement in diseases was discussed. A small molecule inhibitor of Cullins as a potential anti-cancer drug was introduced. Furthermore, proteins with VHL box that might bind to Cullin-2 were described. Finally, how different viral proteins form E3 ubiquitin ligase complexes with Cullin-2 to counter host viral defense were explained. Conclusions Cullin-2 based E3 ubiquitin ligases, using many different substrate recognition receptors, recognize a number of substrates and regulate their protein stability. These complexes play critical roles in biological processes and diseases such as cancer, germline differentiation and viral defense. Through the better understanding of their biology, we can devise and develop new therapeutic strategies to treat cancers, inherited diseases and viral infections.
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Affiliation(s)
- Weijia Cai
- Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 USA
| | - Haifeng Yang
- Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 USA
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26
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Merlet J, Pintard L. Role of the CRL2(LRR-1) E3 ubiquitin-ligase in the development of the germline in C. elegans. WORM 2013; 2:e25716. [PMID: 24778939 PMCID: PMC3875651 DOI: 10.4161/worm.25716] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 07/10/2013] [Indexed: 01/16/2023]
Abstract
The ubiquitin-proteolytic system (UPS) regulates a variety of cellular and biological processes by controlling the stability of regulatory proteins, in space and time. Not surprisingly, defects in this system have been associated with various syndromes and pathologies, including cancer, illustrating the importance of understanding the regulation and the multiple functions of this system. C. elegans is a powerful model system to identify components of the UPS and to study their function during development in multicellular organisms. In C. elegans, the evolutionarily conserved CRL2LRR-1 E3-ligase is critical for the development of the germline. Inactivation of the CUL-2 scaffold or the LRR-1 substrate-recognition subunit leads to a cell cycle arrest in germline stem cells resulting in sterility. Through a genetic screen, we have identified a cul-2 temperature-sensitive allele and we have used this allele to show that CUL-2 plays multiple roles in the development of the germline. CUL-2 (1) promotes germ cell proliferation, (2) influences the balance between mitotic proliferation and meiotic differentiation, and (3) inhibits the first step of meiotic prophase. Here, we discuss how CUL-2 regulates and coordinates these different processes. We suggest that ubiquitin-mediated protein degradation constitutes an important additional layer of regulation that contributes to the spatial organization of the germline.
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Affiliation(s)
- Jorge Merlet
- Institut Jacques Monod; Monod; CNRS; UMR 7592; Univ. Paris Diderot; Sorbonne Paris Cité; F-75205 Paris, France
| | - Lionel Pintard
- Institut Jacques Monod; Monod; CNRS; UMR 7592; Univ. Paris Diderot; Sorbonne Paris Cité; F-75205 Paris, France
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27
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CRL2(LRR-1) E3-ligase regulates proliferation and progression through meiosis in the Caenorhabditis elegans germline. PLoS Genet 2013; 9:e1003375. [PMID: 23555289 PMCID: PMC3610609 DOI: 10.1371/journal.pgen.1003375] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Accepted: 01/29/2013] [Indexed: 11/19/2022] Open
Abstract
The ubiquitin-proteolytic system controls the stability of proteins in space and time. In this study, using a temperature-sensitive mutant allele of the cul-2 gene, we show that CRL2(LRR-1) (CUL-2 RING E3 ubiquitin-ligase and the Leucine Rich Repeat 1 substrate recognition subunit) acts at multiple levels to control germline development. CRL2(LRR-1) promotes germ cell proliferation by counteracting the DNA replication ATL-1 checkpoint pathway. CRL2(LRR-1) also participates in the mitotic proliferation/meiotic entry decision, presumably controlling the stability of meiotic promoting factors in the mitotic zone of the germline. Finally, CRL2(LRR-1) inhibits the first steps of meiotic prophase by targeting in mitotic germ cells degradation of the HORMA domain-containing protein HTP-3, required for loading synaptonemal complex components onto meiotic chromosomes. Given its widespread evolutionary conservation, CUL-2 may similarly regulate germline development in other organisms as well.
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28
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Sloan RS, Swanson CI, Gavilano L, Smith KN, Malek PY, Snow-Smith M, Duronio RJ, Key SCS. Characterization of null and hypomorphic alleles of the Drosophila l(2)dtl/cdt2 gene: Larval lethality and male fertility. Fly (Austin) 2012; 6:173-83. [PMID: 22722696 DOI: 10.4161/fly.20247] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The Drosophila lethal(2)denticleless (l(2)dtl) gene was originally reported as essential for embryogenesis and formation of the rows of tiny hairs on the larval ventral cuticle known as denticle belts. It is now well-established that l(2)dtl (also called cdt2) encodes a subunit of a Cullin 4-based E3 ubiquitin ligase complex that targets a number of key cell cycle regulatory proteins, including p21, Cdt1, E2F1 and Set8, to prevent replication defects and maintain cell cycle control. To investigate the role of l(2)dtl/cdt2 during development, we characterized existing l(2)dtl/cdt2 mutants and generated new deletion alleles, using P-element excision mutagenesis. Surprisingly, homozygous l(2)dtl/cdt2 mutant embryos developed beyond embryogenesis, had intact denticle belts, and lacked an observable embryonic replication defect. These mutants died during larval stages, affirming that loss of l(2)dtl/cdt2 function is lethal. Our data show that L(2)dtl/Cdt2 is maternally deposited, remains nuclear throughout the cell cycle, and has a previously unreported, elevated expression in the developing gonads. We also find that E2f1 regulates l(2)dtl/cdt2 expression during embryogenesis, possibly via several highly conserved putative E2f1 binding sites near the l(2)dtl/cdt2 promoter. Finally, hypomorphic allele combinations of the l(2)dtl/cdt2 gene result in a novel phenotype: viable, low-fertility males. We conclude that "denticleless" is a misnomer, but that l(2)dtl/cdt2 is an essential gene for Drosophila development.
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Affiliation(s)
- Roketa S Sloan
- Department of Biology, North Carolina Central University, Durham, NC USA
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29
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Jia L, Bickel JS, Wu J, Morgan MA, Li H, Yang J, Yu X, Chan RC, Sun Y. RBX1 (RING box protein 1) E3 ubiquitin ligase is required for genomic integrity by modulating DNA replication licensing proteins. J Biol Chem 2010; 286:3379-86. [PMID: 21115485 DOI: 10.1074/jbc.m110.188425] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
RBX1 (RING box protein 1), also known as ROC1 (Regulator of Cullin 1), is an essential component of SCF (Skp1/Cullins/F-box) E3 ubiquitin ligases, which target diverse proteins for proteasome-mediated degradation. Our recent study showed that RBX1 silencing triggered a DNA damage response (DDR) leading to G(2)-M arrest, senescence, and apoptosis, with the mechanism remaining elusive. Here, we show that, in human cancer cells, RBX1 silencing causes the accumulation of DNA replication licensing proteins CDT1 and ORC1, leading to DNA double-strand breaks, DDR, G(2) arrest, and, eventually, aneuploidy. Whereas CHK1 activation by RBX1 silencing is responsible for the G(2) arrest, enhanced DNA damage renders cancer cells more sensitive to radiation. In Caenorhabditis elegans, RBX-1 silencing causes CDT-1 accumulation, triggering DDR in intestinal cells, which is largely abrogated by simultaneous CDT-1 silencing. RBX-1 silencing also induces lethality during development of embryos and in adulthood. Thus, RBX1 E3 ligase is essential for the maintenance of mammalian genome integrity and the proper development and viability in C. elegans.
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Affiliation(s)
- Lijun Jia
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109, USA.
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30
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Merlet J, Burger J, Tavernier N, Richaudeau B, Gomes JE, Pintard L. The CRL2LRR-1 ubiquitin ligase regulates cell cycle progression during C. elegans development. J Cell Sci 2010. [DOI: 10.1242/jcs.083006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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