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Dephosphorylation of the pre-initiation complex is critical for origin firing. Mol Cell 2023; 83:12-25.e10. [PMID: 36543171 DOI: 10.1016/j.molcel.2022.12.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 08/13/2022] [Accepted: 11/30/2022] [Indexed: 12/24/2022]
Abstract
In eukaryotes, cyclin-dependent kinase (CDK) ensures that the genome is duplicated exactly once by inhibiting helicase loading factors before activating origin firing. CDK activates origin firing by phosphorylating two substrates, Sld2 and Sld3, forming a transient and limiting intermediate-the pre-initiation complex (pre-IC). Here, we show in the budding yeast Saccharomyces cerevisiae that the CDK phosphorylations of Sld3 and Sld2 are rapidly turned over during S phase by the PP2A and PP4 phosphatases. PP2ARts1 targets Sld3 specifically through an Rts1-interaction motif, and this targeted dephosphorylation is important for origin firing genome-wide, for formation of the pre-IC at origins and for ensuring that Sld3 is dephosphorylated in G1 phase. PP2ARts1 promotes replication in vitro, and we show that targeted Sld3 dephosphorylation is critical for viability. Together, these studies demonstrate that phosphatases enforce the correct ordering of replication factor phosphorylation and in addition to kinases are also key drivers of replication initiation.
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2
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Moyano-Rodríguez Y, Vaquero D, Vilalta-Castany O, Foltman M, Sanchez-Diaz A, Queralt E. PP2A-Cdc55 phosphatase regulates actomyosin ring contraction and septum formation during cytokinesis. Cell Mol Life Sci 2022; 79:165. [PMID: 35230542 PMCID: PMC8888506 DOI: 10.1007/s00018-022-04209-1] [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: 09/01/2021] [Revised: 02/11/2022] [Accepted: 02/13/2022] [Indexed: 11/03/2022]
Abstract
Eukaryotic cells divide and separate all their components after chromosome segregation by a process called cytokinesis to complete cell division. Cytokinesis is highly regulated by the recruitment of the components to the division site and through post-translational modifications such as phosphorylations. The budding yeast mitotic kinases Cdc28-Clb2, Cdc5, and Dbf2-Mob1 phosphorylate several cytokinetic proteins contributing to the regulation of cytokinesis. The PP2A-Cdc55 phosphatase regulates mitosis counteracting Cdk1- and Cdc5-dependent phosphorylation. This prompted us to propose that PP2A-Cdc55 could also be counteracting the mitotic kinases during cytokinesis. Here we show that in the absence of Cdc55, AMR contraction and the primary septum formation occur asymmetrically to one side of the bud neck supporting a role for PP2A-Cdc55 in cytokinesis regulation. In addition, by in vivo and in vitro assays, we show that PP2A-Cdc55 dephosphorylates the chitin synthase II (Chs2 in budding yeast) a component of the Ingression Progression Complexes (IPCs) involved in cytokinesis. Interestingly, the non-phosphorylable version of Chs2 rescues the asymmetric AMR contraction and the defective septa formation observed in cdc55∆ mutant cells. Therefore, timely dephosphorylation of the Chs2 by PP2A-Cdc55 is crucial for proper actomyosin ring contraction. These findings reveal a new mechanism of cytokinesis regulation by the PP2A-Cdc55 phosphatase and extend our knowledge of the involvement of multiple phosphatases during cytokinesis.
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Affiliation(s)
- Yolanda Moyano-Rodríguez
- Cell Cycle Group, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Av. Gran Via de L'Hospitalet 199-203, L'Hospitalet de Llobregat, Barcelona, Spain
| | - David Vaquero
- Cell Cycle Group, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Av. Gran Via de L'Hospitalet 199-203, L'Hospitalet de Llobregat, Barcelona, Spain.,Instituto de Biomedicina de Valencia (IBV-CSIC), C/ Jaume Roig 11, Valencia, Spain
| | - Odena Vilalta-Castany
- Cell Cycle Group, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Av. Gran Via de L'Hospitalet 199-203, L'Hospitalet de Llobregat, Barcelona, Spain
| | - Magdalena Foltman
- Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria, CSIC, Santander, Spain.,Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Santander, Spain
| | - Alberto Sanchez-Diaz
- Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria, CSIC, Santander, Spain.,Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Santander, Spain
| | - Ethel Queralt
- Cell Cycle Group, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Av. Gran Via de L'Hospitalet 199-203, L'Hospitalet de Llobregat, Barcelona, Spain. .,Instituto de Biomedicina de Valencia (IBV-CSIC), C/ Jaume Roig 11, Valencia, Spain.
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3
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Galli M, Diani L, Quadri R, Nespoli A, Galati E, Panigada D, Plevani P, Muzi-Falconi M. Haspin Modulates the G2/M Transition Delay in Response to Polarization Failures in Budding Yeast. Front Cell Dev Biol 2021; 8:625717. [PMID: 33585466 PMCID: PMC7876276 DOI: 10.3389/fcell.2020.625717] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 12/28/2020] [Indexed: 01/25/2023] Open
Abstract
Symmetry breaking by cellular polarization is an exquisite requirement for the cell-cycle of Saccharomyces cerevisiae cells, as it allows bud emergence and growth. This process is based on the formation of polarity clusters at the incipient bud site, first, and the bud tip later in the cell-cycle, that overall promote bud emission and growth. Given the extreme relevance of this process, a surveillance mechanism, known as the morphogenesis checkpoint, has evolved to coordinate the formation of the bud and cell cycle progression, delaying mitosis in the presence of morphogenetic problems. The atypical protein kinase haspin is responsible for histone H3-T3 phosphorylation and, in yeast, for resolution of polarity clusters in mitosis. Here, we report a novel role for haspin in the regulation of the morphogenesis checkpoint in response to polarity insults. Particularly, we show that cells lacking the haspin ortholog Alk1 fail to achieve sustained checkpoint activation and enter mitosis even in the absence of a bud. In alk1Δ cells, we report a reduced phosphorylation of Cdc28-Y19, which stems from a premature activation of the Mih1 phosphatase. Overall, the data presented in this work define yeast haspin as a novel regulator of the morphogenesis checkpoint in Saccharomyces cerevisiae, where it monitors polarity establishment and it couples bud emergence to the G2/M cell cycle transition.
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Affiliation(s)
- Martina Galli
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milano, Italy
| | - Laura Diani
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milano, Italy
| | - Roberto Quadri
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milano, Italy
| | - Alessandro Nespoli
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milano, Italy
| | - Elena Galati
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milano, Italy
| | - Davide Panigada
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milano, Italy
| | - Paolo Plevani
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milano, Italy
| | - Marco Muzi-Falconi
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milano, Italy
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4
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Leitao RM, Jasani A, Talavara RA, Pham A, Okobi QJ, Kellogg DR. A Conserved PP2A Regulatory Subunit Enforces Proportional Relationships Between Cell Size and Growth Rate. Genetics 2019; 213:517-528. [PMID: 31488515 PMCID: PMC6781898 DOI: 10.1534/genetics.119.301012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 08/10/2019] [Indexed: 11/18/2022] Open
Abstract
Cell size is proportional to growth rate. Thus, cells growing rapidly in rich nutrients can be nearly twice the size of cells growing slowly in poor nutrients. This proportional relationship appears to hold across all orders of life, yet the underlying mechanisms are unknown. In budding yeast, most growth occurs during mitosis, and the proportional relationship between cell size and growth rate is therefore enforced primarily by modulating growth in mitosis. When growth is slow, the duration of mitosis is increased to allow more time for growth, yet the amount of growth required to complete mitosis is reduced, which leads to the birth of small daughter cells. Previous studies have found that Rts1, a member of the conserved B56 family of protein phosphatase 2A regulatory subunits, works in a TORC2 signaling network that influences cell size and growth rate. However, it was unclear whether Rts1 influences cell growth and size in mitosis. Here, we show that Rts1 is required for the proportional relationship between cell size and growth rate during mitosis. Moreover, nutrients and Rts1 influence the duration and extent of growth in mitosis via Wee1 and Pds1/securin, two conserved regulators of mitotic progression. Together, the data are consistent with a model in which global signals that set growth rate also set the critical amount of growth required for cell cycle progression, which would provide a simple mechanistic explanation for the proportional relationship between cell size and growth rate.
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Affiliation(s)
- Ricardo M Leitao
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Akshi Jasani
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Rafael A Talavara
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Annie Pham
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Quincy J Okobi
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Douglas R Kellogg
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
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5
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Gihana GM, Musser TR, Thompson O, Lacefield S. Prolonged cyclin-dependent kinase inhibition results in septin perturbations during return to growth and mitosis. J Cell Biol 2018; 217:2429-2443. [PMID: 29743192 PMCID: PMC6028541 DOI: 10.1083/jcb.201708153] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 03/01/2018] [Accepted: 04/16/2018] [Indexed: 11/22/2022] Open
Abstract
By investigating how yeast cells coordinate polarity and division in a special type of cell division called return to growth, Gihana et al. discover that although checkpoints are normally beneficial, prolonged activation of the morphogenesis checkpoint is instead detrimental to the cell. We investigated how Saccharomyces cerevisiae coordinate polarization, budding, and anaphase during a unique developmental program called return to growth (RTG) in which cells in meiosis return to mitosis upon nutrient shift. Cells reentering mitosis from prophase I deviate from the normal cell cycle by budding in G2 instead of G1. We found that cells do not maintain the bipolar budding pattern, a characteristic of diploid cells. Furthermore, strict temporal regulation of M-phase cyclin-dependent kinase (CDK; M-CDK) is important for polarity establishment and morphogenesis. Cells with premature M-CDK activity caused by loss of checkpoint kinase Swe1 failed to polarize and underwent anaphase without budding. Mutants with increased Swe1-dependent M-CDK inhibition showed additional or more penetrant phenotypes in RTG than mitosis, including elongated buds, multiple buds, spindle mispositioning, and septin perturbation. Surprisingly, the enhanced and additional phenotypes were not exclusive to RTG but also occurred with prolonged Swe1-dependent CDK inhibition in mitosis. Our analysis reveals that prolonged activation of the Swe1-dependent checkpoint can be detrimental instead of beneficial.
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Affiliation(s)
| | | | - Oscar Thompson
- Department of Biology, Indiana University, Bloomington, IN
| | - Soni Lacefield
- Department of Biology, Indiana University, Bloomington, IN
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6
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A Screen for Candidate Targets of Lysine Polyphosphorylation Uncovers a Conserved Network Implicated in Ribosome Biogenesis. Cell Rep 2018; 22:3427-3439. [DOI: 10.1016/j.celrep.2018.02.104] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 01/12/2018] [Accepted: 02/27/2018] [Indexed: 11/22/2022] Open
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Mao Z, Liu C, Lin X, Sun B, Su C. PPP2R5A: A multirole protein phosphatase subunit in regulating cancer development. Cancer Lett 2018; 414:222-229. [DOI: 10.1016/j.canlet.2017.11.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 11/20/2017] [Accepted: 11/21/2017] [Indexed: 12/21/2022]
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8
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Sasi NK, Bhutkar A, Lanning NJ, MacKeigan JP, Weinreich M. DDK Promotes Tumor Chemoresistance and Survival via Multiple Pathways. Neoplasia 2017; 19:439-450. [PMID: 28448802 PMCID: PMC5406526 DOI: 10.1016/j.neo.2017.03.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 03/10/2017] [Accepted: 03/13/2017] [Indexed: 12/12/2022] Open
Abstract
DBF4-dependent kinase (DDK) is a two-subunit kinase required for initiating DNA replication at individual origins and is composed of CDC7 kinase and its regulatory subunit DBF4. Both subunits are highly expressed in many diverse tumor cell lines and primary tumors, and this is correlated with poor prognosis. Inhibiting DDK causes apoptosis of tumor cells, but not normal cells, through a largely unknown mechanism. Firstly, to understand why DDK is often overexpressed in tumors, we identified gene expression signatures that correlate with DDK high- and DDK low-expressing lung adenocarcinomas. We found that increased DDK expression is highly correlated with inactivation of RB1-E2F and p53 tumor suppressor pathways. Both CDC7 and DBF4 promoters bind E2F, suggesting that increased E2F activity in RB1 mutant cancers promotes increased DDK expression. Surprisingly, increased DDK expression levels are also correlated with both increased chemoresistance and genome-wide mutation frequencies. Our data further suggest that high DDK levels directly promote elevated mutation frequencies. Secondly, we performed an RNAi screen to investigate how DDK inhibition causes apoptosis of tumor cells. We identified 23 kinases and phosphatases required for apoptosis when DDK is inhibited. These hits include checkpoint genes, G2/M cell cycle regulators, and known tumor suppressors leading to the hypothesis that inhibiting mitotic progression can protect against DDKi-induced apoptosis. Characterization of one novel hit, the LATS2 tumor suppressor, suggests that it promotes apoptosis independently of the upstream MST1/2 kinases in the Hippo signaling pathway.
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Affiliation(s)
- Nanda Kumar Sasi
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute (VARI), Grand Rapids, MI 49503; Laboratory of Systems Biology, VARI; Graduate Program in Genetics, Michigan State University, East Lansing, MI 48824
| | - Arjun Bhutkar
- David H. Koch Institute for Integrative Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | | | - Michael Weinreich
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute (VARI), Grand Rapids, MI 49503.
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9
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Cui TZ, Peterson TA, Burd CG. A CDC25 family protein phosphatase gates cargo recognition by the Vps26 retromer subunit. eLife 2017; 6. [PMID: 28362258 PMCID: PMC5409824 DOI: 10.7554/elife.24126] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 03/30/2017] [Indexed: 01/14/2023] Open
Abstract
We describe a regulatory mechanism that controls the activity of retromer, an evolutionarily conserved sorting device that orchestrates cargo export from the endosome. A spontaneously arising mutation that activates the yeast (Saccharomyces cerevisiae) CDC25 family phosphatase, Mih1, results in accelerated turnover of a subset of endocytosed plasma membrane proteins due to deficient sorting into a retromer-mediated recycling pathway. Mih1 directly modulates the phosphorylation state of the Vps26 retromer subunit; mutations engineered to mimic these states modulate the binding affinities of Vps26 for a retromer cargo, resulting in corresponding changes in cargo sorting at the endosome. The results suggest that a phosphorylation-based gating mechanism controls cargo selection by yeast retromer, and they establish a functional precedent for CDC25 protein phosphatases that lies outside of their canonical role in regulating cell cycle progression.
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Affiliation(s)
- Tie-Zhong Cui
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Tabitha A Peterson
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States
| | - Christopher G Burd
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
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10
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Promotion of Cell Viability and Histone Gene Expression by the Acetyltransferase Gcn5 and the Protein Phosphatase PP2A in Saccharomyces cerevisiae. Genetics 2016; 203:1693-707. [PMID: 27317677 DOI: 10.1534/genetics.116.189506] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 05/27/2016] [Indexed: 01/23/2023] Open
Abstract
Histone modifications direct chromatin-templated events in the genome and regulate access to DNA sequence information. There are multiple types of modifications, and a common feature is their dynamic nature. An essential step for understanding their regulation, therefore, lies in characterizing the enzymes responsible for adding and removing histone modifications. Starting with a dosage-suppressor screen in Saccharomyces cerevisiae, we have discovered a functional interaction between the acetyltransferase Gcn5 and the protein phosphatase 2A (PP2A) complex, two factors that regulate post-translational modifications. We find that RTS1, one of two genes encoding PP2A regulatory subunits, is a robust and specific high-copy suppressor of temperature sensitivity of gcn5∆ and a subset of other gcn5∆ phenotypes. Conversely, loss of both PP2A(Rts1) and Gcn5 function in the SAGA and SLIK/SALSA complexes is lethal. RTS1 does not restore global transcriptional defects in gcn5∆; however, histone gene expression is restored, suggesting that the mechanism of RTS1 rescue includes restoration of specific cell cycle transcripts. Pointing to new mechanisms of acetylation-phosphorylation cross-talk, RTS1 high-copy rescue of gcn5∆ growth requires two residues of H2B that are phosphorylated in human cells. These data highlight the potential significance of dynamic phosphorylation and dephosphorylation of these deeply conserved histone residues for cell viability.
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11
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Finnigan GC, Sterling SM, Duvalyan A, Liao EN, Sargsyan A, Garcia G, Nogales E, Thorner J. Coordinate action of distinct sequence elements localizes checkpoint kinase Hsl1 to the septin collar at the bud neck in Saccharomyces cerevisiae. Mol Biol Cell 2016; 27:2213-33. [PMID: 27193302 PMCID: PMC4945140 DOI: 10.1091/mbc.e16-03-0177] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 05/13/2016] [Indexed: 01/05/2023] Open
Abstract
A long-standing conundrum is resolved about the underlying sequence determinants and molecular mechanism responsible for the recruitment of the protein kinase Hsl1 (an indispensable component of the so-called “morphogenesis checkpoint”) exclusively to the septin collar at the bud neck. Passage through the eukaryotic cell cycle requires processes that are tightly regulated both spatially and temporally. Surveillance mechanisms (checkpoints) exert quality control and impose order on the timing and organization of downstream events by impeding cell cycle progression until the necessary components are available and undamaged and have acted in the proper sequence. In budding yeast, a checkpoint exists that does not allow timely execution of the G2/M transition unless and until a collar of septin filaments has properly assembled at the bud neck, which is the site where subsequent cytokinesis will occur. An essential component of this checkpoint is the large (1518-residue) protein kinase Hsl1, which localizes to the bud neck only if the septin collar has been correctly formed. Hsl1 reportedly interacts with particular septins; however, the precise molecular determinants in Hsl1 responsible for its recruitment to this cellular location during G2 have not been elucidated. We performed a comprehensive mutational dissection and accompanying image analysis to identify the sequence elements within Hsl1 responsible for its localization to the septins at the bud neck. Unexpectedly, we found that this targeting is multipartite. A segment of the central region of Hsl1 (residues 611–950), composed of two tandem, semiredundant but distinct septin-associating elements, is necessary and sufficient for binding to septin filaments both in vitro and in vivo. However, in addition to 611–950, efficient localization of Hsl1 to the septin collar in the cell obligatorily requires generalized targeting to the cytosolic face of the plasma membrane, a function normally provided by the C-terminal phosphatidylserine-binding KA1 domain (residues 1379–1518) in Hsl1 but that can be replaced by other, heterologous phosphatidylserine-binding sequences.
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Affiliation(s)
- Gregory C Finnigan
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Sarah M Sterling
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Angela Duvalyan
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Elizabeth N Liao
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Aspram Sargsyan
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Galo Garcia
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Eva Nogales
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720 Life Sciences Division, Lawrence Berkeley National Laboratory, and Howard Hughes Medical Institute, Berkeley, CA 94720
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
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