51
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Hume S, Dianov GL, Ramadan K. A unified model for the G1/S cell cycle transition. Nucleic Acids Res 2020; 48:12483-12501. [PMID: 33166394 PMCID: PMC7736809 DOI: 10.1093/nar/gkaa1002] [Citation(s) in RCA: 94] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 10/10/2020] [Accepted: 10/13/2020] [Indexed: 01/01/2023] Open
Abstract
Efficient S phase entry is essential for development, tissue repair, and immune defences. However, hyperactive or expedited S phase entry causes replication stress, DNA damage and oncogenesis, highlighting the need for strict regulation. Recent paradigm shifts and conflicting reports demonstrate the requirement for a discussion of the G1/S transition literature. Here, we review the recent studies, and propose a unified model for the S phase entry decision. In this model, competition between mitogen and DNA damage signalling over the course of the mother cell cycle constitutes the predominant control mechanism for S phase entry of daughter cells. Mitogens and DNA damage have distinct sensing periods, giving rise to three Commitment Points for S phase entry (CP1-3). S phase entry is mitogen-independent in the daughter G1 phase, but remains sensitive to DNA damage, such as single strand breaks, the most frequently-occurring lesions that uniquely threaten DNA replication. To control CP1-3, dedicated hubs integrate the antagonistic mitogenic and DNA damage signals, regulating the stoichiometric cyclin: CDK inhibitor ratio for ultrasensitive control of CDK4/6 and CDK2. This unified model for the G1/S cell cycle transition combines the findings of decades of study, and provides an updated foundation for cell cycle research.
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Affiliation(s)
- Samuel Hume
- Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Grigory L Dianov
- Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
- Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Lavrentieva 10, 630090 Novosibirsk, Russian Federation
- Novosibirsk State University, 630090 Novosibirsk, Russian Federation
| | - Kristijan Ramadan
- Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
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52
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Panagopoulos A, Altmeyer M. The Hammer and the Dance of Cell Cycle Control. Trends Biochem Sci 2020; 46:301-314. [PMID: 33279370 DOI: 10.1016/j.tibs.2020.11.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 10/22/2020] [Accepted: 11/05/2020] [Indexed: 12/14/2022]
Abstract
Cell cycle checkpoints secure ordered progression from one cell cycle phase to the next. They are important to signal cell stress and DNA lesions and to stop cell cycle progression when severe problems occur. Recent work suggests, however, that the cell cycle control machinery responds in more subtle and sophisticated ways when cells are faced with naturally occurring challenges, such as replication impediments associated with endogenous replication stress. Instead of following a stop and go approach, cells use fine-tuned deceleration and brake release mechanisms under the control of ataxia telangiectasia and Rad3-related protein kinase (ATR) and checkpoint kinase 1 (CHK1) to more flexibly adapt their cell cycle program to changing conditions. We highlight emerging examples of such intrinsic cell cycle checkpoint regulation and discuss their physiological and clinical relevance.
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Affiliation(s)
- Andreas Panagopoulos
- Department of Molecular Mechanisms of Disease, University of Zurich, Zurich, Switzerland
| | - Matthias Altmeyer
- Department of Molecular Mechanisms of Disease, University of Zurich, Zurich, Switzerland.
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53
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Johnson C, Belluschi S, Laurenti E. Beyond “to divide or not to divide”: Kinetics matters in hematopoietic stem cells. Exp Hematol 2020; 92:1-10.e2. [DOI: 10.1016/j.exphem.2020.11.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 11/06/2020] [Accepted: 11/07/2020] [Indexed: 01/03/2023]
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54
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Liu C, Konagaya Y, Chung M, Daigh LH, Fan Y, Yang HW, Terai K, Matsuda M, Meyer T. Altered G1 signaling order and commitment point in cells proliferating without CDK4/6 activity. Nat Commun 2020; 11:5305. [PMID: 33082317 PMCID: PMC7576148 DOI: 10.1038/s41467-020-18966-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 09/10/2020] [Indexed: 01/09/2023] Open
Abstract
Cell-cycle entry relies on an orderly progression of signaling events. To start, cells first activate the kinase cyclin D-CDK4/6, which leads to eventual inactivation of the retinoblastoma protein Rb. Hours later, cells inactivate APC/CCDH1 and cross the final commitment point. However, many cells with genetically deleted cyclin Ds, which activate and confer specificity to CDK4/6, can compensate and proliferate. Despite its importance in cancer, how this entry mechanism operates remains poorly characterized, and whether cells use this path under normal conditions remains unknown. Here, using single-cell microscopy, we demonstrate that cells with acutely inhibited CDK4/6 enter the cell cycle with a slowed and fluctuating cyclin E-CDK2 activity increase. Surprisingly, with low CDK4/6 activity, the order of APC/CCDH1 and Rb inactivation is reversed in both cell lines and wild-type mice. Finally, we show that as a consequence of this signaling inversion, Rb inactivation replaces APC/CCDH1 inactivation as the point of no return. Together, we elucidate the molecular steps that enable cell-cycle entry without CDK4/6 activity. Our findings not only have implications in cancer resistance, but also reveal temporal plasticity underlying the G1 regulatory circuit.
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Affiliation(s)
- Chad Liu
- Department of Chemical and Systems Biology, Stanford Medicine, Stanford, CA, 94305, United States
| | - Yumi Konagaya
- Department of Chemical and Systems Biology, Stanford Medicine, Stanford, CA, 94305, United States
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, 606-8501, Japan
- Department of Cell and Developmental Biology, Weill Cornell Medicine, 1300 York Ave, New York, NY, 10065, USA
| | - Mingyu Chung
- Department of Chemical and Systems Biology, Stanford Medicine, Stanford, CA, 94305, United States
| | - Leighton H Daigh
- Department of Chemical and Systems Biology, Stanford Medicine, Stanford, CA, 94305, United States
| | - Yilin Fan
- Department of Chemical and Systems Biology, Stanford Medicine, Stanford, CA, 94305, United States
| | - Hee Won Yang
- Department of Chemical and Systems Biology, Stanford Medicine, Stanford, CA, 94305, United States
- Department of Pathology and Cell Biology, Columbia University Medical Center, 630 West 168th Street, New York, NY, 10032, USA
| | - Kenta Terai
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, 606-8501, Japan
| | - Michiyuki Matsuda
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, 606-8501, Japan
- Department of Pathology and Biology of Diseases, Kyoto University, Kyoto, Japan
| | - Tobias Meyer
- Department of Chemical and Systems Biology, Stanford Medicine, Stanford, CA, 94305, United States.
- Department of Cell and Developmental Biology, Weill Cornell Medicine, 1300 York Ave, New York, NY, 10065, USA.
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55
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Integrating Old and New Paradigms of G1/S Control. Mol Cell 2020; 80:183-192. [PMID: 32946743 DOI: 10.1016/j.molcel.2020.08.020] [Citation(s) in RCA: 142] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 08/17/2020] [Accepted: 08/26/2020] [Indexed: 12/13/2022]
Abstract
The Cdk-Rb-E2F pathway integrates external and internal signals to control progression at the G1/S transition of the mammalian cell cycle. Alterations in this pathway are found in most human cancers, and specific cyclin-dependent kinase Cdk4/6 inhibitors are approved or in clinical trials for the treatment of diverse cancers. In the long-standing paradigm for G1/S control, Cdks inactivate the retinoblastoma tumor suppressor protein (Rb) through phosphorylation, which releases E2F transcription factors to drive cell-cycle progression from G1 to S. However, recent observations in the laboratory and clinic challenge central tenets of the current paradigm and demonstrate that our understanding of the Rb pathway and G1/S control is still incomplete. Here, we integrate these new findings with the previous paradigm to synthesize a current molecular and cellular view of the mammalian G1/S transition. A more complete and accurate understanding of G1/S control will lead to improved therapeutic strategies targeting the cell cycle in cancer.
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56
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Quantifying the Landscape and Transition Paths for Proliferation-Quiescence Fate Decisions. J Clin Med 2020; 9:jcm9082582. [PMID: 32784979 PMCID: PMC7466041 DOI: 10.3390/jcm9082582] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Revised: 07/30/2020] [Accepted: 08/03/2020] [Indexed: 12/01/2022] Open
Abstract
The cell cycle, essential for biological functions, experiences delicate spatiotemporal regulation. The transition between G1 and S phase, which is called the proliferation–quiescence decision, is critical to the cell cycle. However, the stability and underlying stochastic dynamical mechanisms of the proliferation–quiescence decision have not been fully understood. To quantify the process of the proliferation–quiescence decision, we constructed its underlying landscape based on the relevant gene regulatory network. We identified three attractors on the landscape corresponding to the G0, G1, and S phases, individually, which are supported by single-cell data. By calculating the transition path, which quantifies the potential barrier, we built expression profiles in temporal order for key regulators in different transitions. We propose that the two saddle points on the landscape characterize restriction point (RP) and G1/S checkpoint, respectively, which provides quantitative and physical explanations for the mechanisms of Rb governing the RP while p21 controlling the G1/S checkpoint. We found that Emi1 inhibits the transition from G0 to G1, while Emi1 in a suitable range facilitates the transition from G1 to S. These results are partially consistent with previous studies, which also suggested new roles of Emi1 in the cell cycle. By global sensitivity analysis, we identified some critical regulatory factors influencing the proliferation–quiescence decision. Our work provides a global view of the stochasticity and dynamics in the proliferation–quiescence decision of the cell cycle.
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57
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Zatulovskiy E, Zhang S, Berenson DF, Topacio BR, Skotheim JM. Cell growth dilutes the cell cycle inhibitor Rb to trigger cell division. Science 2020; 369:466-471. [PMID: 32703881 PMCID: PMC7489475 DOI: 10.1126/science.aaz6213] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 05/19/2020] [Indexed: 12/21/2022]
Abstract
Cell size is fundamental to cell physiology. For example, cell size determines the spatial scale of organelles and intracellular transport and thereby affects biosynthesis. Although some genes that affect mammalian cell size have been identified, the molecular mechanisms through which cell growth drives cell division have remained elusive. We show that cell growth during the G1 phase of the cell division cycle dilutes the cell cycle inhibitor Retinoblastoma protein (Rb) to trigger division in human cells. RB overexpression increased cell size and G1 duration, whereas RB deletion decreased cell size and removed the inverse correlation between cell size at birth and the duration of the G1 phase. Thus, Rb dilution through cell growth in G1 provides one of the long-sought molecular mechanisms that promotes cell size homeostasis.
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Affiliation(s)
| | - Shuyuan Zhang
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | | | | | - Jan M Skotheim
- Department of Biology, Stanford University, Stanford, CA 94305, USA.
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58
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Pennycook BR, Barr AR. Restriction point regulation at the crossroads between quiescence and cell proliferation. FEBS Lett 2020; 594:2046-2060. [PMID: 32564372 DOI: 10.1002/1873-3468.13867] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 06/08/2020] [Accepted: 06/10/2020] [Indexed: 02/11/2024]
Abstract
The coordination of cell proliferation with reversible cell cycle exit into quiescence is crucial for the development of multicellular organisms and for tissue homeostasis in the adult. The decision between quiescence and proliferation occurs at the restriction point, which is widely thought to be located in the G1 phase of the cell cycle, when cells integrate accumulated extracellular and intracellular signals to drive this binary cellular decision. On the molecular level, decision-making is exerted through the activation of cyclin-dependent kinases (CDKs). CDKs phosphorylate the retinoblastoma (Rb) transcriptional repressor to regulate the expression of cell cycle genes. Recently, the classical view of restriction point regulation has been challenged. Here, we review the latest findings on the activation of CDKs, Rb phosphorylation and the nature and position of the restriction point within the cell cycle.
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Affiliation(s)
- Betheney R Pennycook
- Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, UK
- MRC London Institute of Medical Sciences, Imperial College London, London, UK
| | - Alexis R Barr
- Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, UK
- MRC London Institute of Medical Sciences, Imperial College London, London, UK
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59
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Yang HW, Cappell SD, Jaimovich A, Liu C, Chung M, Daigh LH, Pack LR, Fan Y, Regot S, Covert M, Meyer T. Stress-mediated exit to quiescence restricted by increasing persistence in CDK4/6 activation. eLife 2020; 9:44571. [PMID: 32255427 PMCID: PMC7213986 DOI: 10.7554/elife.44571] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 04/02/2020] [Indexed: 01/04/2023] Open
Abstract
Mammalian cells typically start the cell-cycle entry program by activating cyclin-dependent protein kinase 4/6 (CDK4/6). CDK4/6 activity is clinically relevant as mutations, deletions, and amplifications that increase CDK4/6 activity contribute to the progression of many cancers. However, when CDK4/6 is activated relative to CDK2 remained incompletely understood. Here, we developed a reporter system to simultaneously monitor CDK4/6 and CDK2 activities in single cells and found that CDK4/6 activity increases rapidly before CDK2 activity gradually increases, and that CDK4/6 activity can be active after mitosis or inactive for variable time periods. Markedly, stress signals in G1 can rapidly inactivate CDK4/6 to return cells to quiescence but with reduced probability as cells approach S phase. Together, our study reveals a regulation of G1 length by temporary inactivation of CDK4/6 activity after mitosis, and a progressively increasing persistence in CDK4/6 activity that restricts cells from returning to quiescence as cells approach S phase.
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Affiliation(s)
- Hee Won Yang
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States.,Department of Pathology and Cell Biology, Columbia University Medical Center, New York, United States
| | - Steven D Cappell
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States.,Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, Bethesda, United States
| | - Ariel Jaimovich
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States
| | - Chad Liu
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States
| | - Mingyu Chung
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States
| | - Leighton H Daigh
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States
| | - Lindsey R Pack
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States
| | - Yilin Fan
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States
| | - Sergi Regot
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Bioengineering, Stanford University School of Medicine, Stanford, United States
| | - Markus Covert
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States.,Department of Bioengineering, Stanford University School of Medicine, Stanford, United States
| | - Tobias Meyer
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States.,Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, United States
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