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Islam M, Shen F, Regmi D, Petersen K, Karim MRU, Du D. Tau liquid-liquid phase separation: At the crossroads of tau physiology and tauopathy. J Cell Physiol 2024; 239:e30853. [PMID: 35980344 PMCID: PMC9938090 DOI: 10.1002/jcp.30853] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 07/12/2022] [Accepted: 07/22/2022] [Indexed: 12/14/2022]
Abstract
Abnormal deposition of tau in neurons is a hallmark of Alzheimer's disease and several other neurodegenerative disorders. In the past decades, extensive efforts have been made to explore the mechanistic pathways underlying the development of tauopathies. Recently, the discovery of tau droplet formation by liquid-liquid phase separation (LLPS) has received a great deal of attention. It has been reported that tau condensates have a biological role in promoting and stabilizing microtubule (MT) assembly. Furthermore, it has been hypothesized that the transition of phase-separated tau droplets to a gel-like state and then to fibrils is associated with the pathology of neurodegenerative diseases. In this review, we outline LLPS, the structural disorder that facilitates tau droplet formation, the effects of posttranslational modification of tau on condensate formation, the physiological function of tau droplets, the pathways from droplet to toxic fibrils, and the therapeutic strategies for tauopathies that might evolve from toxic droplets. We expect a deeper understanding of tau LLPS will provide additional insights into tau physiology and tauopathies.
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Affiliation(s)
- Majedul Islam
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, Florida 33431, United States
| | - Fengyun Shen
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, Florida 33431, United States
| | - Deepika Regmi
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, Florida 33431, United States
| | - Katherine Petersen
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, Florida 33431, United States
| | - Md Raza Ul Karim
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, Florida 33431, United States
| | - Deguo Du
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, Florida 33431, United States
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2
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Bregnard TA, Fairchild D, Erlandsen H, Semenova IV, Szczepaniak R, Ahmed A, Weller SK, Korzhnev DM, Bezsonova I. Conformational exchange at a C 2H 2 zinc-binding site facilitates redox sensing by the PML protein. Structure 2023; 31:1086-1099.e6. [PMID: 37473756 PMCID: PMC10528520 DOI: 10.1016/j.str.2023.06.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 05/12/2023] [Accepted: 06/23/2023] [Indexed: 07/22/2023]
Abstract
The promyelocytic leukemia protein, PML, plays a vital role in the cellular response to oxidative stress; however, the molecular mechanism of its action remains poorly understood. Here, we identify redox-sensitive sites of PML. A molecule of PML is cysteine-rich and contains three zinc-binding domains including RING, B-box1, and B-box2. Using in vitro assays, we have compared the sensitivity of the isolated RING and B-box1 domains and shown that B-box1 is more sensitive to oxidation. NMR studies of PML dynamics showed that one of the Zn-coordination sites within the B-box1 undergoes significant conformational exchange, revealing a hotspot for exposure of reactive cysteines. In agreement with the in vitro data, enhancement of the B-box1 Zn-coordination dynamics led to more efficient recruitment of PML into PML nuclear bodies in cells. Overall, our results suggest that the increased sensitivity of B-box1 to oxidative stress makes this domain an important redox-sensing component of PML.
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Affiliation(s)
- Thomas A Bregnard
- Department of Molecular Biology and Biophysics, UCONN Health, Farmington, CT 06032, USA
| | - Daniel Fairchild
- Department of Molecular Biology and Biophysics, UCONN Health, Farmington, CT 06032, USA
| | - Heidi Erlandsen
- Center for Open Research Resources & Equipment, UCONN, Storrs, CT 06269, USA
| | - Irina V Semenova
- Department of Molecular Biology and Biophysics, UCONN Health, Farmington, CT 06032, USA
| | - Renata Szczepaniak
- Department of Molecular Biology and Biophysics, UCONN Health, Farmington, CT 06032, USA
| | - Affrin Ahmed
- Department of Molecular Biology and Biophysics, UCONN Health, Farmington, CT 06032, USA
| | - Sandra K Weller
- Department of Molecular Biology and Biophysics, UCONN Health, Farmington, CT 06032, USA
| | - Dmitry M Korzhnev
- Department of Molecular Biology and Biophysics, UCONN Health, Farmington, CT 06032, USA
| | - Irina Bezsonova
- Department of Molecular Biology and Biophysics, UCONN Health, Farmington, CT 06032, USA.
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3
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Effects of arsenic on the topology and solubility of promyelocytic leukemia (PML)-nuclear bodies. PLoS One 2022; 17:e0268835. [PMID: 35594310 PMCID: PMC9122205 DOI: 10.1371/journal.pone.0268835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 05/09/2022] [Indexed: 11/19/2022] Open
Abstract
Promyelocytic leukemia (PML) proteins are involved in the pathogenesis of acute promyelocytic leukemia (APL). Trivalent arsenic (As3+) is known to cure APL by binding to cysteine residues of PML and enhance the degradation of PML-retinoic acid receptor α (RARα), a t(15;17) gene translocation product in APL cells, and restore PML-nuclear bodies (NBs). The size, number, and shape of PML-NBs vary among cell types and during cell division. However, topological changes of PML-NBs in As3+-exposed cells have not been well-documented. We report that As3+-induced solubility shift underlies rapid SUMOylation of PML and late agglomeration of PML-NBs. Most PML-NBs were toroidal and granular dot-like in GFPPML-transduced CHO-K1 and HEK293 cells, respectively. Exposure to As3+ and antimony (Sb3+) greatly reduced the solubility of PML and enhanced SUMOylation within 2 h in the absence of changes in the number and size of PML-NBs. However, the prolonged exposure to As3+ and Sb3+ resulted in agglomeration of PML-NBs. Exposure to bismuth (Bi3+), another Group 15 element, did not induce any of these changes. ML792, a SUMO activation inhibitor, reduced the number of PML-NBs and increased the size of the NBs, but had little effect on the As3+-induced solubility change of PML. These results warrant the importance of As3+- or Sb3+-induced solubility shift of PML for the regulation intranuclear dynamics of PML-NBs.
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4
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Udagawa O, Kato-Udagawa A, Hirano S. Promyelocytic leukemia nuclear body-like structures can assemble in mouse oocytes. Biol Open 2022; 11:275379. [PMID: 35579421 PMCID: PMC9194678 DOI: 10.1242/bio.059130] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 05/06/2022] [Indexed: 11/29/2022] Open
Abstract
Promyelocytic leukemia (PML) nuclear bodies (PML-NBs), a class of membrane-less cellular organelles, participate in various biological activities. PML-NBs are known as the core-shell-type nuclear body, harboring ‘client’ proteins in their core. Although multiple membrane-less organelles work in the oocyte nucleus, PML-NBs have been predicted to be absent from oocytes. Here, we show that some well-known PML clients (but not endogenous PML) co-localized with small ubiquitin-related modifier (SUMO) protein in the nucleolus and peri-centromeric heterochromatin of maturing oocytes. In oocytes devoid of PML-NBs, endogenous PML protein localized in the vicinity of chromatin. During and after meiotic resumption, PML co-localized with SUMO gathering around chromosomes. To examine the benefit of the PML-NB-free intranuclear milieu in oocytes, we deliberately assembled PML-NBs by microinjecting human PML-encoding plasmids into oocytes. Under conditions of limited SUMO availability, assembled PML-NBs tended to cluster. Upon proteotoxic stress, SUMO delocalized from peri-centromeric heterochromatin and co-localized with SC35 (a marker of nuclear speckles)-positive large compartments, which was disturbed by pre-assembled PML-NBs. These observations suggest that the PML-NB-free intranuclear environment helps reserve SUMO for emergent responses by redirecting the flux of SUMO otherwise needed to maintain PML-NB dynamics. Summary: PML-NB-free intranuclear environment in the oocyte helps reserve SUMO for emergent responses by redirecting the flux of SUMO otherwise needed to maintain PML-NB dynamics.
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Affiliation(s)
- Osamu Udagawa
- Center for Health and Environmental Risk Research, National Institute for Environmental Studies, Japan
| | - Ayaka Kato-Udagawa
- Center for Health and Environmental Risk Research, National Institute for Environmental Studies, Japan
| | - Seishiro Hirano
- Center for Health and Environmental Risk Research, National Institute for Environmental Studies, Japan
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5
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Rubio-Ramos A, Bernabé-Rubio M, Labat-de-Hoz L, Casares-Arias J, Kremer L, Correas I, Alonso MA. MALL, a membrane-tetra-spanning proteolipid overexpressed in cancer, is present in membraneless nuclear biomolecular condensates. Cell Mol Life Sci 2022; 79:236. [PMID: 35399121 PMCID: PMC8995265 DOI: 10.1007/s00018-022-04270-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 03/08/2022] [Accepted: 03/22/2022] [Indexed: 12/04/2022]
Abstract
Proteolipids are proteins with unusual lipid-like properties. It has long been established that PLP and plasmolipin, which are two unrelated membrane-tetra-spanning myelin proteolipids, can be converted in vitro into a water-soluble form with a distinct conformation, raising the question of whether these, or other similar proteolipids, can adopt two different conformations in the cell to adapt their structure to distinct environments. Here, we show that MALL, another proteolipid with a membrane-tetra-spanning structure, distributes in membranes outside the nucleus and, within the nucleus, in membrane-less, liquid-like PML body biomolecular condensates. Detection of MALL in one or other environment was strictly dependent on the method of cell fixation used, suggesting that MALL adopts different conformations depending on its physical environment —lipidic or aqueous— in the cell. The acquisition of the condensate-compatible conformation requires PML expression. Excess MALL perturbed the distribution of the inner nuclear membrane proteins emerin and LAP2β, and that of the DNA-binding protein BAF, leading to the formation of aberrant nuclei. This effect, which is consistent with studies identifying overexpressed MALL as an unfavorable prognostic factor in cancer, could contribute to cell malignancy. Our study establishes a link between proteolipids, membranes and biomolecular condensates, with potential biomedical implications.
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Affiliation(s)
- Armando Rubio-Ramos
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Miguel Bernabé-Rubio
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Leticia Labat-de-Hoz
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Javier Casares-Arias
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Leonor Kremer
- Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, 28049, Madrid, Spain
| | - Isabel Correas
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain
- Department of Molecular Biology, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Miguel A Alonso
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain.
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6
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McPhee MJ, Salsman J, Foster J, Thompson J, Mathavarajah S, Dellaire G, Ridgway ND. Running 'LAPS' Around nLD: Nuclear Lipid Droplet Form and Function. Front Cell Dev Biol 2022; 10:837406. [PMID: 35178392 PMCID: PMC8846306 DOI: 10.3389/fcell.2022.837406] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 01/10/2022] [Indexed: 12/12/2022] Open
Abstract
The nucleus harbours numerous protein subdomains and condensates that regulate chromatin organization, gene expression and genomic stress. A novel nuclear subdomain that is formed following exposure of cells to excess fatty acids is the nuclear lipid droplet (nLD), which is composed of a neutral lipid core surrounded by a phospholipid monolayer and associated regulatory and lipid biosynthetic enzymes. While structurally resembling cytoplasmic LDs, nLDs are formed by distinct but poorly understood mechanisms that involve the emergence of lipid droplets from the lumen of the nucleoplasmic reticulum and de novo lipid synthesis. Luminal lipid droplets that emerge into the nucleoplasm do so at regions of the inner nuclear membrane that become enriched in promyelocytic leukemia (PML) protein. The resulting nLDs that retain PML on their surface are termed lipid-associated PML structures (LAPS), and are distinct from canonical PML nuclear bodies (NB) as they lack key proteins and modifications associated with these NBs. PML is a key regulator of nuclear signaling events and PML NBs are sites of gene regulation and post-translational modification of transcription factors. Therefore, the subfraction of nLDs that form LAPS could regulate lipid stress responses through their recruitment and retention of the PML protein. Both nLDs and LAPS have lipid biosynthetic enzymes on their surface suggesting they are active sites for nuclear phospholipid and triacylglycerol synthesis as well as global lipid regulation. In this review we have summarized the current understanding of nLD and LAPS biogenesis in different cell types, their structure and composition relative to other PML-associated cellular structures, and their role in coordinating a nuclear response to cellular overload of fatty acids.
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Affiliation(s)
- Michael J McPhee
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | - Jayme Salsman
- Department of Pathology, Dalhousie University, Halifax, NS, Canada
| | - Jason Foster
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | - Jordan Thompson
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | | | - Graham Dellaire
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada.,Department of Pathology, Dalhousie University, Halifax, NS, Canada
| | - Neale D Ridgway
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada.,Department of Pediatrics, Dalhousie University, Halifax, NS, Canada
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7
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Abstract
The 14-3-3 family proteins are vital scaffold proteins that ubiquitously expressed in various tissues. They interact with numerous protein targets and mediate many cellular signaling pathways. The 14-3-3 binding motifs are often embedded in intrinsically disordered regions which are closely associated with liquid-liquid phase separation (LLPS). In the past ten years, LLPS has been observed for a variety of proteins and biological processes, indicating that LLPS plays a fundamental role in the formation of membraneless organelles and cellular condensates. While extensive investigations have been performed on 14-3-3 proteins, its involvement in LLPS is overlooked. To date, 14-3-3 proteins have not been reported to undergo LLPS alone or regulate LLPS of their binding partners. To reveal the potential involvement of 14-3-3 proteins in LLPS, in this review, we summarized the LLPS propensity of 14-3-3 binding partners and found that about one half of them may undergo LLPS spontaneously. We further analyzed the phase separation behavior of representative 14-3-3 binders and discussed how 14-3-3 proteins may be involved. By modulating the conformation and valence of interactions and recruiting other molecules, we speculate that 14-3-3 proteins can efficiently regulate the functions of their targets in the context of LLPS. Considering the critical roles of 14-3-3 proteins, there is an urgent need for investigating the involvement of 14-3-3 proteins in the phase separation process of their targets and the underling mechanisms.
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8
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Sołtys K, Ożyhar A. Transcription Regulators and Membraneless Organelles Challenges to Investigate Them. Int J Mol Sci 2021; 22:12758. [PMID: 34884563 PMCID: PMC8657783 DOI: 10.3390/ijms222312758] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/19/2021] [Accepted: 11/23/2021] [Indexed: 12/13/2022] Open
Abstract
Eukaryotic cells are composed of different bio-macromolecules that are divided into compartments called organelles providing optimal microenvironments for many cellular processes. A specific type of organelles is membraneless organelles. They are formed via a process called liquid-liquid phase separation that is driven by weak multivalent interactions between particular bio-macromolecules. In this review, we gather crucial information regarding different classes of transcription regulators with the propensity to undergo liquid-liquid phase separation and stress the role of intrinsically disordered regions in this phenomenon. We also discuss recently developed experimental systems for studying formation and properties of membraneless organelles.
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Affiliation(s)
- Katarzyna Sołtys
- Department of Biochemistry, Molecular Biology and Biotechnology, Faculty of Chemistry, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland;
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9
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Recent Advances in Our Understanding of the Infectious Entry Pathway of Human Papillomavirus Type 16. Microorganisms 2021; 9:microorganisms9102076. [PMID: 34683397 PMCID: PMC8540256 DOI: 10.3390/microorganisms9102076] [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: 09/09/2021] [Accepted: 09/27/2021] [Indexed: 12/31/2022] Open
Abstract
Papillomaviruses are a diverse viral species, but several types such as HPV16 are given special attention due to their contribution towards the pathogenesis of several major cancers. In this review, we will summarize how the knowledge of HPV16 entry has expanded since the last comprehensive HPV16 entry review our lab published in 2017.
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10
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Patra U, Müller S. A Tale of Usurpation and Subversion: SUMO-Dependent Integrity of Promyelocytic Leukemia Nuclear Bodies at the Crossroad of Infection and Immunity. Front Cell Dev Biol 2021; 9:696234. [PMID: 34513832 PMCID: PMC8430037 DOI: 10.3389/fcell.2021.696234] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 07/30/2021] [Indexed: 12/13/2022] Open
Abstract
Promyelocytic leukemia nuclear bodies (PML NBs) are multi-protein assemblies representing distinct sub-nuclear structures. As phase-separated molecular condensates, PML NBs exhibit liquid droplet-like consistency. A key organizer of the assembly and dynamics of PML NBs is the ubiquitin-like SUMO modification system. SUMO is covalently attached to PML and other core components of PML NBs thereby exhibiting a glue-like function by providing multivalent interactions with proteins containing SUMO interacting motifs (SIMs). PML NBs serve as the catalytic center for nuclear SUMOylation and SUMO-SIM interactions are essential for protein assembly within these structures. Importantly, however, formation of SUMO chains on PML and other PML NB-associated proteins triggers ubiquitylation and proteasomal degradation which coincide with disruption of these nuclear condensates. To date, a plethora of nuclear activities such as transcriptional and post-transcriptional regulation of gene expression, apoptosis, senescence, cell cycle control, DNA damage response, and DNA replication have been associated with PML NBs. Not surprisingly, therefore, SUMO-dependent PML NB integrity has been implicated in regulating many physiological processes including tumor suppression, metabolism, drug-resistance, development, cellular stemness, and anti-pathogen immune response. The interplay between PML NBs and viral infection is multifaceted. As a part of the cellular antiviral defense strategy, PML NB components are crucial restriction factors for many viruses and a mutual positive correlation has been found to exist between PML NBs and the interferon response. Viruses, in turn, have developed counterstrategies for disarming PML NB associated immune defense measures. On the other end of the spectrum, certain viruses are known to usurp specific PML NB components for successful replication and disruption of these sub-nuclear foci has recently been linked to the stimulation rather than curtailment of antiviral gene repertoire. Importantly, the ability of invading virions to manipulate the host SUMO modification machinery is essential for this interplay between PML NB integrity and viruses. Moreover, compelling evidence is emerging in favor of bacterial pathogens to negotiate with the SUMO system thereby modulating PML NB-directed intrinsic and innate immunity. In the current context, we will present an updated account of the dynamic intricacies between cellular PML NBs as the nuclear SUMO modification hotspots and immune regulatory mechanisms in response to viral and bacterial pathogens.
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Affiliation(s)
- Upayan Patra
- Institute of Biochemistry II, Faculty of Medicine, Goethe University, Frankfurt, Germany
| | - Stefan Müller
- Institute of Biochemistry II, Faculty of Medicine, Goethe University, Frankfurt, Germany
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11
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Sprunger ML, Jackrel ME. Prion-Like Proteins in Phase Separation and Their Link to Disease. Biomolecules 2021; 11:biom11071014. [PMID: 34356638 PMCID: PMC8301953 DOI: 10.3390/biom11071014] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 06/28/2021] [Accepted: 07/06/2021] [Indexed: 02/01/2023] Open
Abstract
Aberrant protein folding underpins many neurodegenerative diseases as well as certain myopathies and cancers. Protein misfolding can be driven by the presence of distinctive prion and prion-like regions within certain proteins. These prion and prion-like regions have also been found to drive liquid-liquid phase separation. Liquid-liquid phase separation is thought to be an important physiological process, but one that is prone to malfunction. Thus, aberrant liquid-to-solid phase transitions may drive protein aggregation and fibrillization, which could give rise to pathological inclusions. Here, we review prions and prion-like proteins, their roles in phase separation and disease, as well as potential therapeutic approaches to counter aberrant phase transitions.
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12
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Orti F, Navarro AM, Rabinovich A, Wodak SJ, Marino-Buslje C. Insight into membraneless organelles and their associated proteins: Drivers, Clients and Regulators. Comput Struct Biotechnol J 2021; 19:3964-3977. [PMID: 34377363 PMCID: PMC8318826 DOI: 10.1016/j.csbj.2021.06.042] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 06/26/2021] [Accepted: 06/27/2021] [Indexed: 02/06/2023] Open
Abstract
In recent years, attention has been devoted to proteins forming immiscible liquid phases within the liquid intracellular medium, commonly referred to as membraneless organelles (MLO). These organelles enable the spatiotemporal associations of cellular components that exchange dynamically with the cellular milieu. The dysregulation of these liquid-liquid phase separation processes (LLPS) may cause various diseases including neurodegenerative pathologies and cancer, among others. Until very recently, databases containing information on proteins forming MLOs, as well as tools and resources facilitating their analysis, were missing. This has recently changed with the publication of 4 databases that focus on different types of experiments, sets of proteins, inclusion criteria, and levels of annotation or curation. In this study we integrate and analyze the information across these databases, complement their records, and produce a consolidated set of proteins that enables the investigation of the LLPS phenomenon. To gain insight into the features that characterize different types of MLOs and the roles of their associated proteins, they were grouped into categories: High Confidence MLO associated (including Drivers and reviewed proteins), Potential Clients and Regulators, according to their annotated functions. We show that none of the databases taken alone covers the data sufficiently to enable meaningful analysis, validating our integration effort as essential for gaining better understanding of phase separation and laying the foundations for the discovery of new proteins potentially involved in this important cellular process. Lastly, we developed a server, enabling customized selections of different sets of proteins based on MLO location, database, disorder content, among other attributes (https://forti.shinyapps.io/mlos/).
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Affiliation(s)
- Fernando Orti
- Bioinformatics Unit, Fundación Instituto Leloir. Avda. Patricias Argentinas 435, Buenos Aires B1405WE, Argentina
| | - Alvaro M. Navarro
- Bioinformatics Unit, Fundación Instituto Leloir. Avda. Patricias Argentinas 435, Buenos Aires B1405WE, Argentina
| | - Andres Rabinovich
- Bioinformatics Unit, Fundación Instituto Leloir. Avda. Patricias Argentinas 435, Buenos Aires B1405WE, Argentina
| | - Shoshana J. Wodak
- VIB-VUB Center for Structural Biology, Flemish Institute for Biotechnology, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
| | - Cristina Marino-Buslje
- Bioinformatics Unit, Fundación Instituto Leloir. Avda. Patricias Argentinas 435, Buenos Aires B1405WE, Argentina
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13
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Phasing the intranuclear organization of steroid hormone receptors. Biochem J 2021; 478:443-461. [DOI: 10.1042/bcj20200883] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 12/28/2020] [Accepted: 01/07/2021] [Indexed: 12/15/2022]
Abstract
Steroid receptors (SRs) encompass a family of transcription factors that regulate the expression of thousands of genes upon binding to steroid hormones and include the glucocorticoid, androgen, progesterone, estrogen and mineralocorticoid receptors. SRs control key physiological and pathological processes, thus becoming relevant drug targets. As with many other nuclear proteins, hormone-activated SRs concentrate in multiple discrete foci within the cell nucleus. Even though these foci were first observed ∼25 years ago, their exact structure and function remained elusive. In the last years, new imaging methodologies and theoretical frameworks improved our understanding of the intranuclear organization. These studies led to a new paradigm stating that many membraneless nuclear compartments, including transcription-related foci, form through a liquid–liquid phase separation process. These exciting ideas impacted the SR field by raising the hypothesis of SR foci as liquid condensates involved in transcriptional regulation. In this work, we review the current knowledge about SR foci formation under the light of the condensate model, analyzing how these structures may impact SR function. These new ideas, combined with state-of-the-art techniques, may shed light on the biophysical mechanisms governing the formation of SR foci and the biological function of these structures in normal physiology and disease.
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14
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Double-edged role of PML nuclear bodies during human adenovirus infection. Virus Res 2020; 295:198280. [PMID: 33370557 DOI: 10.1016/j.virusres.2020.198280] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 12/21/2020] [Accepted: 12/23/2020] [Indexed: 01/31/2023]
Abstract
PML nuclear bodies are matrix-bound nuclear structures with a variety of functions in human cells. These nuclear domains are interferon regulated and play an essential role during virus infections involving accumulation of SUMO-dependent host and viral factors. PML-NBs are targeted and subsequently manipulated by adenoviral regulatory proteins, illustrating their crucial role during productive infection and virus-mediated oncogenic transformation. PML-NBs have a longstanding antiviral reputation; however, the genomes of Human Adenoviruses and initial sites of viral transcription/replication are found juxtaposed to these domains, resulting in a double-edged capacity of these nuclear multiprotein/multifunctional complexes. This enigma provides evidence that Human Adenoviruses selectively counteract antiviral responses, and simultaneously benefit from or even depend on proviral PML-NB associated components by active recruitment to PML track-like structures, that are induced during infection. Thereby, a positive microenvironment for adenoviral transcription and replication is created at these nuclear subdomains. Based on the available data, this review aims to provide a detailed overview of the current knowledge of Human Adenovirus crosstalk with nuclear PML body compartments as sites of SUMOylation processes in the host cells, evaluating the currently known principles and molecular mechanisms.
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15
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Corpet A, Kleijwegt C, Roubille S, Juillard F, Jacquet K, Texier P, Lomonte P. PML nuclear bodies and chromatin dynamics: catch me if you can! Nucleic Acids Res 2020; 48:11890-11912. [PMID: 33068409 PMCID: PMC7708061 DOI: 10.1093/nar/gkaa828] [Citation(s) in RCA: 94] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 09/15/2020] [Accepted: 09/18/2020] [Indexed: 12/17/2022] Open
Abstract
Eukaryotic cells compartmentalize their internal milieu in order to achieve specific reactions in time and space. This organization in distinct compartments is essential to allow subcellular processing of regulatory signals and generate specific cellular responses. In the nucleus, genetic information is packaged in the form of chromatin, an organized and repeated nucleoprotein structure that is a source of epigenetic information. In addition, cells organize the distribution of macromolecules via various membrane-less nuclear organelles, which have gathered considerable attention in the last few years. The macromolecular multiprotein complexes known as Promyelocytic Leukemia Nuclear Bodies (PML NBs) are an archetype for nuclear membrane-less organelles. Chromatin interactions with nuclear bodies are important to regulate genome function. In this review, we will focus on the dynamic interplay between PML NBs and chromatin. We report how the structure and formation of PML NBs, which may involve phase separation mechanisms, might impact their functions in the regulation of chromatin dynamics. In particular, we will discuss how PML NBs participate in the chromatinization of viral genomes, as well as in the control of specific cellular chromatin assembly pathways which govern physiological mechanisms such as senescence or telomere maintenance.
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Affiliation(s)
- Armelle Corpet
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U 1217, LabEx DEVweCAN, Institut NeuroMyoGène (INMG), team Chromatin Dynamics, Nuclear Domains, Virus F-69008, Lyon, France
| | - Constance Kleijwegt
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U 1217, LabEx DEVweCAN, Institut NeuroMyoGène (INMG), team Chromatin Dynamics, Nuclear Domains, Virus F-69008, Lyon, France
| | - Simon Roubille
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U 1217, LabEx DEVweCAN, Institut NeuroMyoGène (INMG), team Chromatin Dynamics, Nuclear Domains, Virus F-69008, Lyon, France
| | - Franceline Juillard
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U 1217, LabEx DEVweCAN, Institut NeuroMyoGène (INMG), team Chromatin Dynamics, Nuclear Domains, Virus F-69008, Lyon, France
| | - Karine Jacquet
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U 1217, LabEx DEVweCAN, Institut NeuroMyoGène (INMG), team Chromatin Dynamics, Nuclear Domains, Virus F-69008, Lyon, France
| | - Pascale Texier
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U 1217, LabEx DEVweCAN, Institut NeuroMyoGène (INMG), team Chromatin Dynamics, Nuclear Domains, Virus F-69008, Lyon, France
| | - Patrick Lomonte
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U 1217, LabEx DEVweCAN, Institut NeuroMyoGène (INMG), team Chromatin Dynamics, Nuclear Domains, Virus F-69008, Lyon, France
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16
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Yu C, Shen B, You K, Huang Q, Shi M, Wu C, Chen Y, Zhang C, Li T. Proteome-scale analysis of phase-separated proteins in immunofluorescence images. Brief Bioinform 2020; 22:5900570. [PMID: 34020549 DOI: 10.1093/bib/bbaa187] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 07/16/2020] [Accepted: 07/21/2020] [Indexed: 12/25/2022] Open
Abstract
Phase separation is an important mechanism that mediates the spatial distribution of proteins in different cellular compartments. While phase-separated proteins share certain sequence characteristics, including intrinsically disordered regions (IDRs) and prion-like domains, such characteristics are insufficient for making accurate predictions; thus, a proteome-wide understanding of phase separation is currently lacking. Here, we define phase-separated proteomes based on the systematic analysis of immunofluorescence images of 12 073 proteins in the Human Protein Atlas. The analysis of these proteins reveals that phase-separated candidate proteins exhibit higher IDR contents, higher mean net charge and lower hydropathy and prefer to bind to RNA. Kinases and transcription factors are also enriched among these candidate proteins. Strikingly, both phase-separated kinases and phase-separated transcription factors display significantly reduced substrate specificity. Our work provides the first global view of the phase-separated proteome and suggests that the spatial proximity resulting from phase separation reduces the requirement for motif specificity and expands the repertoire of substrates. The source code and data are available at https://github.com/cheneyyu/deepphase.
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Affiliation(s)
- Chunyu Yu
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Boyan Shen
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Kaiqiang You
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Qi Huang
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Minglei Shi
- MOE Key Laboratory of Bioinformatics; Bioinformatics Division and Center for Synthetic & Systems Biology, TNLIST; School of Medicine, Tsinghua University, Beijing, China
| | - Congying Wu
- Institute of Systems Biomedicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Yang Chen
- MOE Key Laboratory of Bioinformatics; Bioinformatics Division and Center for Synthetic & Systems Biology, TNLIST; School of Medicine, Tsinghua University, Beijing, China
| | - Chaolin Zhang
- Department of Systems Biology, Department of Biochemistry and Molecular Biophysics, Center for Motor Neuron Biology and Disease, Columbia University, New York, USA
| | - Tingting Li
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
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17
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Lee J, Salsman J, Foster J, Dellaire G, Ridgway ND. Lipid-associated PML structures assemble nuclear lipid droplets containing CCTα and Lipin1. Life Sci Alliance 2020; 3:3/8/e202000751. [PMID: 32461215 PMCID: PMC7266991 DOI: 10.26508/lsa.202000751] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 05/13/2020] [Accepted: 05/14/2020] [Indexed: 11/24/2022] Open
Abstract
PML proteins assemble into noncanonical lipid-associated PML structures (LAPS) on nuclear lipid droplets, which recruit CCTα and Lipin1 for the synthesis of phosphatidylcholine and triacylglycerol. Nuclear lipid droplets (nLDs) form on the inner nuclear membrane by a mechanism involving promyelocytic leukemia (PML), the protein scaffold of PML nuclear bodies. We report that PML structures on nLDs in oleate-treated U2OS cells, referred to as lipid-associated PML structures (LAPS), differ from canonical PML nuclear bodies by the relative absence of SUMO1, SP100, and DAXX. These nLDs were also enriched in CTP:phosphocholine cytidylyltransferase α (CCTα), the phosphatidic acid phosphatase Lipin1, and DAG. Translocation of CCTα onto nLDs was mediated by its α-helical M-domain but was not correlated with its activator DAG. High-resolution imaging revealed that CCTα and LAPS occupied distinct polarized regions on nLDs. PML knockout U2OS (PML KO) cells lacking LAPS had a 40–50% reduction in nLDs with associated CCTα, and residual nLDs were almost devoid of Lipin1 and DAG. As a result, phosphatidylcholine and triacylglycerol synthesis was inhibited in PML KO cells. We conclude that in response to excess exogenous fatty acids, LAPS are required to assemble nLDs that are competent to recruit CCTα and Lipin1.
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Affiliation(s)
- Jonghwa Lee
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada
| | - Jayme Salsman
- Department of Pathology, Dalhousie University, Halifax, Canada
| | - Jason Foster
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada
| | - Graham Dellaire
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada .,Department of Pathology, Dalhousie University, Halifax, Canada
| | - Neale D Ridgway
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada .,Department of Pediatrics, Dalhousie University, Halifax, Canada
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18
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Koreski KP, Rieder LE, McLain LM, Chaubal A, Marzluff WF, Duronio RJ. Drosophila histone locus body assembly and function involves multiple interactions. Mol Biol Cell 2020; 31:1525-1537. [PMID: 32401666 PMCID: PMC7359574 DOI: 10.1091/mbc.e20-03-0176] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The histone locus body (HLB) assembles at replication-dependent (RD) histone loci and concentrates factors required for RD histone mRNA biosynthesis. The Drosophila melanogaster genome has a single locus comprised of ∼100 copies of a tandemly arrayed 5-kB repeat unit containing one copy of each of the 5 RD histone genes. To determine sequence elements required for D. melanogaster HLB formation and histone gene expression, we used transgenic gene arrays containing 12 copies of the histone repeat unit that functionally complement loss of the ∼200 endogenous RD histone genes. A 12x histone gene array in which all H3-H4 promoters were replaced with H2a-H2b promoters (12xPR) does not form an HLB or express high levels of RD histone mRNA in the presence of the endogenous histone genes. In contrast, this same transgenic array is active in HLB assembly and RD histone gene expression in the absence of the endogenous RD histone genes and rescues the lethality caused by homozygous deletion of the RD histone locus. The HLB formed in the absence of endogenous RD histone genes on the mutant 12x array contains all known factors present in the wild-type HLB including CLAMP, which normally binds to GAGA repeats in the H3-H4 promoter. These data suggest that multiple protein–protein and/or protein–DNA interactions contribute to HLB formation, and that the large number of endogenous RD histone gene copies sequester available factor(s) from attenuated transgenic arrays, thereby preventing HLB formation and gene expression on these arrays.
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Affiliation(s)
- Kaitlin P Koreski
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Leila E Rieder
- Department of Biology, Emory University, Atlanta, GA 30322
| | - Lyndsey M McLain
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Ashlesha Chaubal
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC 27599
| | - William F Marzluff
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599.,Department of Biology, University of North Carolina, Chapel Hill, NC 27599.,Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC 27599.,Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599.,Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599
| | - Robert J Duronio
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599.,Department of Biology, University of North Carolina, Chapel Hill, NC 27599.,Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC 27599.,Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599.,Department of Genetics, University of North Carolina, Chapel Hill, NC 27599
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19
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Paulus C, Harwardt T, Walter B, Marxreiter A, Zenger M, Reuschel E, Nevels MM. Revisiting promyelocytic leukemia protein targeting by human cytomegalovirus immediate-early protein 1. PLoS Pathog 2020; 16:e1008537. [PMID: 32365141 PMCID: PMC7224577 DOI: 10.1371/journal.ppat.1008537] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 05/14/2020] [Accepted: 04/13/2020] [Indexed: 12/18/2022] Open
Abstract
Promyelocytic leukemia (PML) bodies are nuclear organelles implicated in intrinsic and innate antiviral defense. The eponymous PML proteins, central to the self-organization of PML bodies, and other restriction factors found in these organelles are common targets of viral antagonism. The 72-kDa immediate-early protein 1 (IE1) is the principal antagonist of PML bodies encoded by the human cytomegalovirus (hCMV). IE1 is believed to disrupt PML bodies by inhibiting PML SUMOylation, while PML was proposed to act as an E3 ligase for IE1 SUMOylation. PML targeting by IE1 is considered to be crucial for hCMV replication at low multiplicities of infection, in part via counteracting antiviral gene induction linked to the cellular interferon (IFN) response. However, current concepts of IE1-PML interaction are largely derived from mutant IE1 proteins known or predicted to be metabolically unstable and globally misfolded. We performed systematic clustered charge-to-alanine scanning mutagenesis and identified a stable IE1 mutant protein (IE1cc172-176) with wild-type characteristics except for neither interacting with PML proteins nor inhibiting PML SUMOylation. Consequently, IE1cc172-176 does not associate with PML bodies and is selectively impaired for disrupting these organelles. Surprisingly, functional analysis of IE1cc172-176 revealed that the protein is hypermodified by mixed SUMO chains and that IE1 SUMOylation depends on nucleosome rather than PML binding. Furthermore, a mutant hCMV expressing IE1cc172-176 was only slightly attenuated compared to an IE1-null virus even at low multiplicities of infection. Finally, hCMV-induced expression of cytokine and IFN-stimulated genes turned out to be reduced rather than increased in the presence of IE1cc172-176 relative to wild-type IE1. Our findings challenge present views on the relationship of IE1 with PML and the role of PML in hCMV replication. This study also provides initial evidence for the idea that disruption of PML bodies upon viral infection is linked to activation rather than inhibition of innate immunity.
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Affiliation(s)
- Christina Paulus
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews, United Kingdom
| | - Thomas Harwardt
- Institute for Medical Microbiology and Hygiene, University of Regensburg, Regensburg, Germany
| | - Bernadette Walter
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews, United Kingdom
| | - Andrea Marxreiter
- Institute for Medical Microbiology and Hygiene, University of Regensburg, Regensburg, Germany
| | - Marion Zenger
- Institute for Medical Microbiology and Hygiene, University of Regensburg, Regensburg, Germany
| | - Edith Reuschel
- Department of Obstetrics and Gynecology, Clinic St. Hedwig at Hospital Barmherzige Brüder Regensburg, Regensburg, Germany
| | - Michael M. Nevels
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews, United Kingdom
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20
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Guion LG, Sapp M. The Role of Promyelocytic Leukemia Nuclear Bodies During HPV Infection. Front Cell Infect Microbiol 2020; 10:35. [PMID: 32154186 PMCID: PMC7045071 DOI: 10.3389/fcimb.2020.00035] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 01/17/2020] [Indexed: 12/15/2022] Open
Abstract
Promyelocytic leukemia (PML) nuclear bodies (NBs) are highly dynamic subnuclear structures. Their name giving major component, PML protein, is essential for their formation. PML is present in many different isoforms due to differential splicing, which seem to contribute differently to PML NBs function. Sp100 and DAXX are also permanently residing in these structures. PML NBs disassemble in mitosis to form large cytoplasmic aggregates and reassemble after completion of cell division. Posttranslational modifications such as SUMOylation play important roles for protein association with PML NBs. In addition to the factors permanently associated with PML NBs, a large number of proteins may transiently reside in PML NBs dependent on cell stage, type, and condition. PML NBs have been indirectly implicated in a large number of cellular processes including apoptosis, transcriptional regulation, DNA repair and replication. They are considered hot spots for posttranslational modifications and may serve as readily accessible protein depots. However, a precise function has been difficult to assign. Many DNA viruses target PML NBs after entry often resulting in reorganization of these subnuclear structures. Antiviral activity has been assigned to PML NBs partially based on the observation that PML protein is an interferon stimulated gene. In contrast, human papillomavirus (HPV) infection requires the presence of PML protein suggesting that PML NBs may be essential to establish infection. This review will summarize and discuss recent advances in our understanding of the role of PML NBs and individual protein components in the establishment of HPV infection.
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Affiliation(s)
- Lucile G Guion
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, LA, United States.,Feist Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA, United States
| | - Martin Sapp
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, LA, United States.,Feist Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA, United States
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21
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Lång A, Lång E, Bøe SO. PML Bodies in Mitosis. Cells 2019; 8:cells8080893. [PMID: 31416160 PMCID: PMC6721746 DOI: 10.3390/cells8080893] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 08/08/2019] [Accepted: 08/10/2019] [Indexed: 12/14/2022] Open
Abstract
Promyelocytic leukemia (PML) bodies are dynamic intracellular structures that recruit and release a variety of different proteins in response to stress, virus infection, DNA damage and cell cycle progression. While PML bodies primarily are regarded as nuclear compartments, they are forced to travel to the cytoplasm each time a cell divides, due to breakdown of the nuclear membrane at entry into mitosis and subsequent nuclear exclusion of nuclear material at exit from mitosis. Here we review the biochemical and biophysical transitions that occur in PML bodies during mitosis and discuss this in light of post-mitotic nuclear import, cell fate decision and acute promyelocytic leukemia therapy.
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Affiliation(s)
- Anna Lång
- Oslo University Hospital, Department of Molecular Microbiology, Forskningsveien 1, 0373 Oslo, Norway
| | - Emma Lång
- Oslo University Hospital, Department of Molecular Microbiology, Forskningsveien 1, 0373 Oslo, Norway
| | - Stig Ove Bøe
- Oslo University Hospital, Department of Molecular Microbiology, Forskningsveien 1, 0373 Oslo, Norway.
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22
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Ditlev JA, Vega AR, Köster DV, Su X, Tani T, Lakoduk AM, Vale RD, Mayor S, Jaqaman K, Rosen MK. A composition-dependent molecular clutch between T cell signaling condensates and actin. eLife 2019; 8:e42695. [PMID: 31268421 PMCID: PMC6624021 DOI: 10.7554/elife.42695] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 06/14/2019] [Indexed: 01/04/2023] Open
Abstract
During T cell activation, biomolecular condensates form at the immunological synapse (IS) through multivalency-driven phase separation of LAT, Grb2, Sos1, SLP-76, Nck, and WASP. These condensates move radially at the IS, traversing successive radially-oriented and concentric actin networks. To understand this movement, we biochemically reconstituted LAT condensates with actomyosin filaments. We found that basic regions of Nck and N-WASP/WASP promote association and co-movement of LAT condensates with actin, indicating conversion of weak individual affinities to high collective affinity upon phase separation. Condensates lacking these components were propelled differently, without strong actin adhesion. In cells, LAT condensates lost Nck as radial actin transitioned to the concentric network, and engineered condensates constitutively binding actin moved aberrantly. Our data show that Nck and WASP form a clutch between LAT condensates and actin in vitro and suggest that compositional changes may enable condensate movement by distinct actin networks in different regions of the IS.
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Affiliation(s)
- Jonathon A Ditlev
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- Department of BiophysicsHoward Hughes Medical Institute, University of Texas Southwestern Medical CenterDallasUnited States
| | - Anthony R Vega
- Department of BiophysicsUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Darius Vasco Köster
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- National Centre for Biological Sciences, Tata Institute for Fundamental ResearchBangaloreIndia
| | - Xiaolei Su
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- Department of Cellular and Molecular PharmacologyHoward Hughes Medical Institute, University of California, San FranciscoSan FranciscoUnited States
| | - Tomomi Tani
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological LaboratoryWoods HoleUnited States
| | - Ashley M Lakoduk
- Department of Cell BiologyUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Ronald D Vale
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- Department of Cellular and Molecular PharmacologyHoward Hughes Medical Institute, University of California, San FranciscoSan FranciscoUnited States
| | - Satyajit Mayor
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- National Centre for Biological Sciences, Tata Institute for Fundamental ResearchBangaloreIndia
| | - Khuloud Jaqaman
- Department of BiophysicsUniversity of Texas Southwestern Medical CenterDallasUnited States
- Lyda Hill Department of BioinformaticsUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Michael K Rosen
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- Department of BiophysicsHoward Hughes Medical Institute, University of Texas Southwestern Medical CenterDallasUnited States
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23
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Zhang Y, Bertulat B, Tencer AH, Ren X, Wright GM, Black J, Cardoso MC, Kutateladze TG. MORC3 Forms Nuclear Condensates through Phase Separation. iScience 2019; 17:182-189. [PMID: 31284181 PMCID: PMC6614601 DOI: 10.1016/j.isci.2019.06.030] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 06/03/2019] [Accepted: 06/19/2019] [Indexed: 12/27/2022] Open
Abstract
Phase separation can produce local structures with specific functionality in the cell, and in the nucleus, this can lead to chromatin reorganization. Microrchidia 3 (MORC3) is a human ATPase that has been implicated in autoimmune disorders and cancer. Here, we show that MORC3 forms phase-separated condensates with liquid-like properties in the cell nucleus. Fluorescence live-cell imaging reveals that the MORC3 condensates are heterogeneous and undergo dynamic morphological changes during the cell cycle. The ATPase activity of MORC3 drives its phase separation in vitro and requires DNA binding and releasing the MORC3 CW domain-dependent autoinhibition through association with histone H3. Our findings suggest a mechanism by which the ATPase function of MORC3 mediates MORC3 nuclear compartmentalization. MORC3 forms nuclear condensates with liquid-like characteristics Morphology of the MORC3 condensates changes during the cell cycle Phase separation depends on the MORC3 ATPase activity and DNA binding CW impedes the ability of MORC3 to form condensates
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Affiliation(s)
- Yi Zhang
- Department of Pharmacology, University of Colorado School of Medicine, 12801 East 17th Avenue, Aurora, CO 80045, USA
| | - Bianca Bertulat
- Department of Biology, Technische Universität Darmstadt, Darmstadt, 64287, Germany
| | - Adam H Tencer
- Department of Pharmacology, University of Colorado School of Medicine, 12801 East 17th Avenue, Aurora, CO 80045, USA
| | - Xiaojun Ren
- Department of Chemistry, University of Colorado, Denver, CO 80217, USA
| | - Gregory M Wright
- Department of Pharmacology, University of Colorado School of Medicine, 12801 East 17th Avenue, Aurora, CO 80045, USA
| | - Joshua Black
- Department of Pharmacology, University of Colorado School of Medicine, 12801 East 17th Avenue, Aurora, CO 80045, USA
| | - M Cristina Cardoso
- Department of Biology, Technische Universität Darmstadt, Darmstadt, 64287, Germany
| | - Tatiana G Kutateladze
- Department of Pharmacology, University of Colorado School of Medicine, 12801 East 17th Avenue, Aurora, CO 80045, USA.
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24
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Guion L, Bienkowska-Haba M, DiGiuseppe S, Florin L, Sapp M. PML nuclear body-residing proteins sequentially associate with HPV genome after infectious nuclear delivery. PLoS Pathog 2019; 15:e1007590. [PMID: 30802273 PMCID: PMC6405170 DOI: 10.1371/journal.ppat.1007590] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 03/07/2019] [Accepted: 01/18/2019] [Indexed: 12/20/2022] Open
Abstract
Subnuclear promyelocytic leukemia (PML) nuclear bodies (NBs) are targeted by many DNA viruses after nuclear delivery. PML protein is essential for formation of PML NBs. Sp100 and Small Ubiquitin-Like Modifier (SUMO) are also permanently residing within PML NBs. Often, large DNA viruses disassemble and reorganize PML NBs to counteract their intrinsic antiviral activity and support establishment of infection. However, human papillomavirus (HPV) requires PML protein to retain incoming viral DNA in the nucleus for subsequent efficient transcription. In contrast, Sp100 was identified as a restriction factor for HPV. These findings suggested that PML NBs are important regulators of early stages of the HPV life cycle. Nuclear delivery of incoming HPV DNA requires mitosis. Viral particles are retained within membrane-bound transport vesicles throughout mitosis. The viral genome is released from transport vesicles by an unknown mechanism several hours after nuclear envelope reformation. The minor capsid protein L2 mediates intracellular transport by becoming transmembranous in the endocytic compartment. Herein, we tested our hypothesis that PML protein is recruited to incoming viral genome prior to egress from transport vesicles. High-resolution microscopy revealed that PML protein, SUMO-1, and Sp100 are recruited to incoming viral genomes, rather than viral genomes being targeted to preformed PML NBs. Differential immunofluorescent staining suggested that PML protein and SUMO-1 associated with transport vesicles containing viral particles prior to egress, implying that recruitment is likely mediated by L2 protein. In contrast, Sp100 recruitment to HPV-harboring PML NBs occurred after release of viral genomes from transport vesicles. The delayed recruitment of Sp100 is specific for HPV-associated PML NBs. These data suggest that the virus continuously resides within a protective environment until the transport vesicle breaks down in late G1 phase and imply that HPV might modulate PML NB assembly to achieve establishment of infection and the shift to viral maintenance.
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Affiliation(s)
- Lucile Guion
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology, Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Malgorzata Bienkowska-Haba
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology, Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Stephen DiGiuseppe
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Luise Florin
- Department of Virology and Research Center for Immunotherapy (FZI), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Martin Sapp
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology, Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
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25
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Ditlev JA, Case LB, Rosen MK. Who's In and Who's Out-Compositional Control of Biomolecular Condensates. J Mol Biol 2018; 430:4666-4684. [PMID: 30099028 PMCID: PMC6204295 DOI: 10.1016/j.jmb.2018.08.003] [Citation(s) in RCA: 205] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 08/01/2018] [Accepted: 08/05/2018] [Indexed: 02/06/2023]
Abstract
Biomolecular condensates are two- and three-dimensional compartments in eukaryotic cells that concentrate specific collections of molecules without an encapsulating membrane. Many condensates behave as dynamic liquids and appear to form through liquid-liquid phase separation driven by weak, multivalent interactions between macromolecules. In this review, we discuss current models and data regarding the control of condensate composition, and we describe our current understanding of the composition of representative condensates including PML nuclear bodies, P-bodies, stress granules, the nucleolus, and two-dimensional membrane localized LAT and nephrin clusters. Specific interactions, such as interactions between modular binding domains, weaker interactions between intrinsically disorder regions and nucleic acid base pairing, and nonspecific interactions, such as electrostatic interactions and hydrophobic interactions, influence condensate composition. Understanding how specific condensate composition is determined is essential to understanding condensates as biochemical entities and ultimately discerning their cellular and organismic functions.
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Affiliation(s)
- Jonathon A Ditlev
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Lindsay B Case
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Michael K Rosen
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Coordinated collective migration and asymmetric cell division in confluent human keratinocytes without wounding. Nat Commun 2018; 9:3665. [PMID: 30202009 PMCID: PMC6131553 DOI: 10.1038/s41467-018-05578-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 07/16/2018] [Indexed: 12/19/2022] Open
Abstract
Epithelial sheet spreading is a fundamental cellular process that must be coordinated with cell division and differentiation to restore tissue integrity. Here we use consecutive serum deprivation and re-stimulation to reconstruct biphasic collective migration and proliferation in cultured sheets of human keratinocytes. In this system, a burst of long-range coordinated locomotion is rapidly generated throughout the cell sheet in the absence of wound edges. Migrating cohorts reach correlation lengths of several millimeters and display dependencies on epidermal growth factor receptor-mediated signaling, self-propelled polarized migration, and a G1/G0 cell cycle environment. The migration phase is temporally and spatially aligned with polarized cell divisions characterized by pre-mitotic nuclear migration to the cell front and asymmetric partitioning of nuclear promyelocytic leukemia bodies and lysosomes to opposite daughter cells. This study investigates underlying mechanisms contributing to the stark contrast between cells in a static quiescent state compared to the long-range coordinated collective migration seen in contact with blood serum. Epithelial sheet migration requires polarized and coordinated cell movement. Here, the authors demonstrate serum-activated collective migration followed by polarized asymmetric cell divisions in otherwise quiescent human keratinocyte monolayers in the absence of wound edges.
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Hoischen C, Monajembashi S, Weisshart K, Hemmerich P. Multimodal Light Microscopy Approaches to Reveal Structural and Functional Properties of Promyelocytic Leukemia Nuclear Bodies. Front Oncol 2018; 8:125. [PMID: 29888200 PMCID: PMC5980967 DOI: 10.3389/fonc.2018.00125] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 04/05/2018] [Indexed: 12/11/2022] Open
Abstract
The promyelocytic leukemia (pml) gene product PML is a tumor suppressor localized mainly in the nucleus of mammalian cells. In the cell nucleus, PML seeds the formation of macromolecular multiprotein complexes, known as PML nuclear bodies (PML NBs). While PML NBs have been implicated in many cellular functions including cell cycle regulation, survival and apoptosis their role as signaling hubs along major genome maintenance pathways emerged more clearly. However, despite extensive research over the past decades, the precise biochemical function of PML in these pathways is still elusive. It remains a big challenge to unify all the different previously suggested cellular functions of PML NBs into one mechanistic model. With the advent of genetically encoded fluorescent proteins it became possible to trace protein function in living specimens. In parallel, a variety of fluorescence fluctuation microscopy (FFM) approaches have been developed which allow precise determination of the biophysical and interaction properties of cellular factors at the single molecule level in living cells. In this report, we summarize the current knowledge on PML nuclear bodies and describe several fluorescence imaging, manipulation, FFM, and super-resolution techniques suitable to analyze PML body assembly and function. These include fluorescence redistribution after photobleaching, fluorescence resonance energy transfer, fluorescence correlation spectroscopy, raster image correlation spectroscopy, ultraviolet laser microbeam-induced DNA damage, erythrocyte-mediated force application, and super-resolution microscopy approaches. Since most if not all of the microscopic equipment to perform these techniques may be available in an institutional or nearby facility, we hope to encourage more researches to exploit sophisticated imaging tools for their research in cancer biology.
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28
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Functions and dys-functions of promyelocytic leukemia protein PML. RENDICONTI LINCEI-SCIENZE FISICHE E NATURALI 2018. [DOI: 10.1007/s12210-018-0714-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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29
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Lång A, Øye A, Eriksson J, Rowe AD, Lång E, Bøe SO. Influence of acute promyelocytic leukemia therapeutic drugs on nuclear pore complex density and integrity. Biochem Biophys Res Commun 2018; 499:570-576. [PMID: 29596829 DOI: 10.1016/j.bbrc.2018.03.191] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 03/25/2018] [Indexed: 11/16/2022]
Abstract
During cell division, a large number of nuclear proteins are released into the cytoplasm due to nuclear envelope breakdown. Timely nuclear import of these proteins following exit from mitosis is critical for establishment of the G1 nuclear environment. Dysregulation of post-mitotic nuclear import may affect the fate of newly divided stem or progenitor cells and may lead to cancer. Acute promyelocytic leukemia (APL) is a malignant disorder that involves a defect in blood cell differentiation at the promyelocytic stage. Recent studies suggest that pharmacological concentrations of the APL therapeutic drugs, all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), affect post-mitotic nuclear import of the APL-associated oncoprotein PML/RARA. In the present study, we have investigated the possibility that ATRA and ATO affect post-mitotic nuclear import through interference with components of the nuclear import machinery. We observe reduced density and impaired integrity of nuclear pore complexes after ATRA and/or ATO exposure. Using a post-mitotic nuclear import assay, we demonstrate distinct import kinetics among different nuclear import pathways while nuclear import rates were similar in the presence or absence of APL therapeutic drugs.
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Affiliation(s)
- Anna Lång
- Department of Medical Biochemistry and Department of Microbiology, Oslo University Hospital, Sognsvannsveien 20, 0372 Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Postboks 1171 Blindern, 0318 Oslo, Norway.
| | - Alexander Øye
- Department of Medical Biochemistry and Department of Microbiology, Oslo University Hospital, Sognsvannsveien 20, 0372 Oslo, Norway.
| | - Jens Eriksson
- Department of Medical Biochemistry and Department of Microbiology, Oslo University Hospital, Sognsvannsveien 20, 0372 Oslo, Norway.
| | - Alexander D Rowe
- Department of Medical Biochemistry and Department of Microbiology, Oslo University Hospital, Sognsvannsveien 20, 0372 Oslo, Norway; Norwegian National Unit for Newborn Screening, Division for Pediatric and Adolescent Medicine, Oslo University Hospital, Sognsvannsveien 20, 0372 Oslo, Norway.
| | - Emma Lång
- Department of Medical Biochemistry and Department of Microbiology, Oslo University Hospital, Sognsvannsveien 20, 0372 Oslo, Norway.
| | - Stig Ove Bøe
- Department of Medical Biochemistry and Department of Microbiology, Oslo University Hospital, Sognsvannsveien 20, 0372 Oslo, Norway.
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Sawyer IA, Hager GL, Dundr M. Specific genomic cues regulate Cajal body assembly. RNA Biol 2017; 14:791-803. [PMID: 27715441 PMCID: PMC5519236 DOI: 10.1080/15476286.2016.1243648] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 09/06/2016] [Accepted: 09/27/2016] [Indexed: 02/07/2023] Open
Abstract
The assembly of specialized sub-nuclear microenvironments known as nuclear bodies (NBs) is important for promoting efficient nuclear function. In particular, the Cajal body (CB), a prominent NB that facilitates spliceosomal snRNP biogenesis, assembles in response to genomic cues. Here, we detail the factors that regulate CB assembly and structural maintenance. These include the importance of transcription at nucleating gene loci, the grouping of these genes on human chromosomes 1, 6 and 17, as well as cell cycle and biochemical regulation of CB protein function. We also speculate on the correlation between CB formation and RNA splicing levels in neurons and cancer. The timing and location of these specific molecular events is critical to CB assembly and its contribution to genome function. However, further work is required to explore the emerging biophysical characteristics of CB assembly and the impact upon subsequent genome reorganization.
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Affiliation(s)
- Iain A. Sawyer
- Department of Cell Biology, Rosalind Franklin University of Medicine & Science, Chicago Medical School, North Chicago, IL, USA
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Gordon L. Hager
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Miroslav Dundr
- Department of Cell Biology, Rosalind Franklin University of Medicine & Science, Chicago Medical School, North Chicago, IL, USA
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31
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Banani SF, Lee HO, Hyman AA, Rosen MK. Biomolecular condensates: organizers of cellular biochemistry. Nat Rev Mol Cell Biol 2017; 18:285-298. [PMID: 28225081 PMCID: PMC7434221 DOI: 10.1038/nrm.2017.7] [Citation(s) in RCA: 3162] [Impact Index Per Article: 451.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Biomolecular condensates are micron-scale compartments in eukaryotic cells that lack surrounding membranes but function to concentrate proteins and nucleic acids. These condensates are involved in diverse processes, including RNA metabolism, ribosome biogenesis, the DNA damage response and signal transduction. Recent studies have shown that liquid-liquid phase separation driven by multivalent macromolecular interactions is an important organizing principle for biomolecular condensates. With this physical framework, it is now possible to explain how the assembly, composition, physical properties and biochemical and cellular functions of these important structures are regulated.
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Affiliation(s)
- Salman F. Banani
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Hyun O. Lee
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Anthony A. Hyman
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Michael K. Rosen
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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32
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Lång A, Eriksson J, Schink KO, Lång E, Blicher P, Połeć A, Brech A, Dalhus B, Bøe SO. Visualization of PML nuclear import complexes reveals FG-repeat nucleoporins at cargo retrieval sites. Nucleus 2017; 8:404-420. [PMID: 28402725 DOI: 10.1080/19491034.2017.1306161] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
Selective nuclear import in eukaryotic cells involves sequential interactions between nuclear import receptors and phenylalanine-glycine (FG)-repeat nucleoporins. Traditionally, binding of cargoes to import receptors is perceived as a nuclear pore complex independent event, while interactions between import complexes and nucleoporins are thought to take place at the nuclear pores. However, studies have shown that nucleoporins are mobile and not static within the nuclear pores, suggesting that they may become engaged in nuclear import before nuclear pore entry. Here we have studied post-mitotic nuclear import of the tumor suppressor protein PML. Since this protein forms nuclear compartments called PML bodies that persist during mitosis, the assembly of putative PML import complexes can be visualized on the surface of these protein aggregates as the cell progress from an import inactive state in mitosis to an import active state in G1. We show that these post-mitotic cytoplasmic PML bodies incorporate a multitude of peripheral nucleoporins, but not scaffold or nuclear basket nucleoporins, in a manner that depends on FG-repeats, the KPNB1 import receptor, and the PML nuclear localization signal. The study suggests that nucleoporins have the ability to target certain nuclear cargo proteins in a nuclear pore-uncoupled state, before nuclear pore entry.
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Affiliation(s)
- Anna Lång
- a Department of Medical Biochemistry , Oslo University Hospital , Oslo , Norway.,b Institute of Clinical Medicine , University of Oslo , Oslo , Norway
| | - Jens Eriksson
- a Department of Medical Biochemistry , Oslo University Hospital , Oslo , Norway
| | - Kay Oliver Schink
- c Department of Molecular Cell Biology, Institute for Cancer Research and Centre for Cancer Biomedicine , Oslo University Hospital , Oslo , Norway
| | - Emma Lång
- a Department of Medical Biochemistry , Oslo University Hospital , Oslo , Norway
| | - Pernille Blicher
- a Department of Medical Biochemistry , Oslo University Hospital , Oslo , Norway
| | - Anna Połeć
- a Department of Medical Biochemistry , Oslo University Hospital , Oslo , Norway
| | - Andreas Brech
- c Department of Molecular Cell Biology, Institute for Cancer Research and Centre for Cancer Biomedicine , Oslo University Hospital , Oslo , Norway
| | - Bjørn Dalhus
- a Department of Medical Biochemistry , Oslo University Hospital , Oslo , Norway
| | - Stig Ove Bøe
- a Department of Medical Biochemistry , Oslo University Hospital , Oslo , Norway
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Bienkowska-Haba M, Luszczek W, Keiffer TR, Guion LGM, DiGiuseppe S, Scott RS, Sapp M. Incoming human papillomavirus 16 genome is lost in PML protein-deficient HaCaT keratinocytes. Cell Microbiol 2017; 19. [PMID: 27860076 DOI: 10.1111/cmi.12708] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 11/10/2016] [Accepted: 11/15/2016] [Indexed: 01/01/2023]
Abstract
Human papillomaviruses (HPVs) target promyelocytic leukemia (PML) nuclear bodies (NBs) during infectious entry and PML protein is important for efficient transcription of incoming viral genome. However, the transcriptional down regulation was shown to be promoter-independent in that heterologous promoters delivered by papillomavirus particles were also affected. To further investigate the role of PML protein in HPV entry, we used small hairpin RNA to knockdown PML protein in HaCaT keratinocytes. Confirming previous findings, PML knockdown in HaCaT cells reduced HPV16 transcript levels significantly following infectious entry without impairing binding and trafficking. However, when we quantified steady-state levels of pseudogenomes in interphase cells, we found strongly reduced genome levels compared with parental HaCaT cells. Because nuclear delivery was comparable in both cell lines, we conclude that viral pseudogenome must be removed after successful nuclear delivery. Transcriptome analysis by gene array revealed that PML knockdown in clonal HaCaT cells was associated with a constitutive interferon response. Abrogation of JAK1/2 signaling prevented genome loss, however, did not restore viral transcription. In contrast, knockdown of PML protein in HeLa cells did not affect HPV genome delivery and transcription. HeLa cells are transformed by HPV18 oncogenes E6 and E7, which have been shown to interfere with the JAK/Stat signaling pathway. Our data imply that PML NBs protect incoming HPV genomes. Furthermore, they provide evidence that PML NBs are key regulators of the innate immune response in keratinocytes. IMPORTANCE Promyelocytic leukemia nuclear bodies (PML NBs) are important for antiviral defense. Many DNA viruses target these subnuclear structures and reorganize them. Reorganization of PML NBs by viral proteins is important for establishment of infection. In contrast, HPVs require the presence of PML protein for efficient transcription of incoming viral genome. Our finding that PML protein prevents the loss of HPV genome following infection implies that the host cell may be able to recognize chromatinized HPV genome or the associated capsid proteins. A constitutively active interferon response in absence of PML protein suggests that PML NBs are key regulators of the innate immune response in keratinocytes.
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Affiliation(s)
- Malgorzata Bienkowska-Haba
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, Louisiana, USA
| | - Wioleta Luszczek
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, Louisiana, USA
| | - Timothy R Keiffer
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, Louisiana, USA
| | - Lucile G M Guion
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, Louisiana, USA
| | - Stephen DiGiuseppe
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, Louisiana, USA
| | - Rona S Scott
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, Louisiana, USA
| | - Martin Sapp
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, Louisiana, USA
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34
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DiGiuseppe S, Bienkowska-Haba M, Guion LG, Sapp M. Cruising the cellular highways: How human papillomavirus travels from the surface to the nucleus. Virus Res 2016; 231:1-9. [PMID: 27984059 DOI: 10.1016/j.virusres.2016.10.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 10/25/2016] [Indexed: 11/17/2022]
Abstract
The non-enveloped human papillomaviruses (HPVs) specifically target epithelial cells of the skin and mucosa. Successful infection requires a lesion in the stratified tissue for access to the basal cells. Herein, we discuss our recent progress in understanding binding, internalization, uncoating, and intracellular trafficking of HPV particles. Our focus will be on HPV type 16, which is the most common HPV type associated with various anogenital and oropharyngeal carcinomas. The study of HPV entry has revealed a number of novel cellular pathways utilized during infection. These include but are not restricted to the following: a previously uncharacterized form of endocytosis, membrane penetration by a capsid protein, the use of retromer complexes for trafficking to the trans-Golgi network, the requirement for nuclear envelope breakdown and microtubule-mediated transport during mitosis for nuclear entry, the existence of membrane-bound intranuclear vesicles harboring HPV genome, and the requirement of PML protein for efficient transcription of incoming viral genome. The continued study of these pathways may reveal new roles in basic biological cellular processes.
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Affiliation(s)
- Stephen DiGiuseppe
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, LA, USA
| | - Malgorzata Bienkowska-Haba
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, LA, USA
| | - Lucile G Guion
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, LA, USA
| | - Martin Sapp
- Department of Microbiology and Immunology, Center for Molecular Tumor Virology, Feist-Weiller Cancer Center, LSU Health Shreveport, Shreveport, LA, USA.
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35
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Banani SF, Rice AM, Peeples WB, Lin Y, Jain S, Parker R, Rosen MK. Compositional Control of Phase-Separated Cellular Bodies. Cell 2016; 166:651-663. [PMID: 27374333 DOI: 10.1016/j.cell.2016.06.010] [Citation(s) in RCA: 771] [Impact Index Per Article: 96.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 03/13/2016] [Accepted: 06/01/2016] [Indexed: 12/12/2022]
Abstract
Cellular bodies such as P bodies and PML nuclear bodies (PML NBs) appear to be phase-separated liquids organized by multivalent interactions among proteins and RNA molecules. Although many components of various cellular bodies are known, general principles that define body composition are lacking. We modeled cellular bodies using several engineered multivalent proteins and RNA. In vitro and in cells, these scaffold molecules form phase-separated liquids that concentrate low valency client proteins. Clients partition differently depending on the ratio of scaffolds, with a sharp switch across the phase diagram diagonal. Composition can switch rapidly through changes in scaffold concentration or valency. Natural PML NBs and P bodies show analogous partitioning behavior, suggesting how their compositions could be controlled by levels of PML SUMOylation or cellular mRNA concentration, respectively. The data suggest a conceptual framework for considering the composition and control thereof of cellular bodies assembled through heterotypic multivalent interactions.
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Affiliation(s)
- Salman F Banani
- Department of Biophysics and Howard Hughes Medical Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Allyson M Rice
- Department of Biophysics and Howard Hughes Medical Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - William B Peeples
- Department of Biophysics and Howard Hughes Medical Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yuan Lin
- Department of Biophysics and Howard Hughes Medical Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Saumya Jain
- Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder, CO 80309, USA
| | - Roy Parker
- Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder, CO 80309, USA
| | - Michael K Rosen
- Department of Biophysics and Howard Hughes Medical Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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36
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SUMO5, a Novel Poly-SUMO Isoform, Regulates PML Nuclear Bodies. Sci Rep 2016; 6:26509. [PMID: 27211601 PMCID: PMC4876461 DOI: 10.1038/srep26509] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 05/04/2016] [Indexed: 12/23/2022] Open
Abstract
Promyelocytic leukemia nuclear bodies (PML-NBs) are PML-based nuclear structures that regulate various cellular processes. SUMOylation, the process of covalently conjugating small ubiquitin-like modifiers (SUMOs), is required for both the formation and the disruption of PML-NBs. However, detailed mechanisms of how SUMOylation regulates these processes remain unknown. Here we report that SUMO5, a novel SUMO variant, mediates the growth and disruption of PML-NBs. PolySUMO5 conjugation of PML at lysine 160 facilitates recruitment of PML-NB components, which enlarges PML-NBs. SUMO5 also increases polySUMO2/3 conjugation of PML, resulting in RNF4-mediated disruption of PML-NBs. The acute promyelocytic leukemia oncoprotein PML-RARα blocks SUMO5 conjugation of PML, causing cytoplasmic displacement of PML and disruption of PML-NBs. Our work not only identifies a new member of the SUMO family but also reveals the mechanistic basis of the PML-NB life cycle in human cells.
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37
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de Castro IJ, Gokhan E, Vagnarelli P. Resetting a functional G1 nucleus after mitosis. Chromosoma 2016; 125:607-19. [PMID: 26728621 PMCID: PMC5023730 DOI: 10.1007/s00412-015-0561-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 11/13/2015] [Indexed: 12/21/2022]
Abstract
The maintenance of the correct cellular information goes beyond the simple transmission of an intact genetic code from one generation to the next. Epigenetic changes, topological cues and correct protein-protein interactions need to be re-established after each cell division to allow the next cell cycle to resume in the correct regulated manner. This process begins with mitotic exit and re-sets all the changes that occurred during mitosis thus restoring a functional G1 nucleus in preparation for the next cell cycle. Mitotic exit is triggered by inactivation of mitotic kinases and the reversal of their phosphorylation activities on many cellular components, from nuclear lamina to transcription factors and chromatin itself. To reverse all these phosphorylations, phosphatases act during mitotic exit in a timely and spatially controlled manner directing the events that lead to a functional G1 nucleus. In this review, we will summarise the recent developments on the control of phosphatases and their known substrates during mitotic exit, and the key steps that control the restoration of chromatin status, nuclear envelope reassembly and nuclear body re-organisation. Although pivotal work has been conducted in this area in yeast, due to differences between the mitotic exit network between yeast and vertebrates, we will mainly concentrate on the vertebrate system.
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Affiliation(s)
- Ines J de Castro
- College of Health and Life Science, Research Institute of Environment Health and Society, Brunel University London, Uxbridge, UB8 3PH, UK
| | - Ezgi Gokhan
- College of Health and Life Science, Research Institute of Environment Health and Society, Brunel University London, Uxbridge, UB8 3PH, UK
| | - Paola Vagnarelli
- College of Health and Life Science, Research Institute of Environment Health and Society, Brunel University London, Uxbridge, UB8 3PH, UK.
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38
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Pinder J, Salsman J, Dellaire G. Nuclear domain 'knock-in' screen for the evaluation and identification of small molecule enhancers of CRISPR-based genome editing. Nucleic Acids Res 2015; 43:9379-92. [PMID: 26429972 PMCID: PMC4627099 DOI: 10.1093/nar/gkv993] [Citation(s) in RCA: 198] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Accepted: 09/21/2015] [Indexed: 12/31/2022] Open
Abstract
CRISPR is a genome-editing platform that makes use of the bacterially-derived endonuclease Cas9 to introduce DNA double-strand breaks at precise locations in the genome using complementary guide RNAs. We developed a nuclear domain knock-in screen, whereby the insertion of a gene encoding the green fluorescent protein variant Clover is inserted by Cas9-mediated homology directed repair (HDR) within the first exon of genes that are required for the structural integrity of subnuclear domains such as the nuclear lamina and promyelocytic leukemia nuclear bodies (PML NBs). Using this approach, we compared strategies for enhancing CRISPR-mediated HDR, focusing on known genes and small molecules that impact non-homologous end joining (NHEJ) and homologous recombination (HR). Ultimately, we identified the small molecule RS-1 as a potent enhancer of CRISPR-based genome editing, enhancing HDR 3- to 6-fold depending on the locus and transfection method. We also characterized U2OS human osteosarcoma cells expressing Clover-tagged PML and demonstrate that this strategy generates cell lines with PML NBs that are structurally and functionally similar to bodies in the parental cell line. Thus, the nuclear domain knock-in screen that we describe provides a simple means of rapidly evaluating methods and small molecules that have the potential to enhance Cas9-mediated HDR.
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Affiliation(s)
- Jordan Pinder
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Jayme Salsman
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Graham Dellaire
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada Beatrice Hunter Cancer Research Institute, Halifax, Nova Scotia, B3H 4R2, Canada
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39
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Nott TJ, Petsalaki E, Farber P, Jervis D, Fussner E, Plochowietz A, Craggs TD, Bazett-Jones DP, Pawson T, Forman-Kay JD, Baldwin AJ. Phase transition of a disordered nuage protein generates environmentally responsive membraneless organelles. Mol Cell 2015; 57:936-947. [PMID: 25747659 PMCID: PMC4352761 DOI: 10.1016/j.molcel.2015.01.013] [Citation(s) in RCA: 1179] [Impact Index Per Article: 131.0] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 05/12/2014] [Accepted: 12/29/2014] [Indexed: 11/15/2022]
Abstract
Cells chemically isolate molecules in compartments to both facilitate and regulate their interactions. In addition to membrane-encapsulated compartments, cells can form proteinaceous and membraneless organelles, including nucleoli, Cajal and PML bodies, and stress granules. The principles that determine when and why these structures form have remained elusive. Here, we demonstrate that the disordered tails of Ddx4, a primary constituent of nuage or germ granules, form phase-separated organelles both in live cells and in vitro. These bodies are stabilized by patterned electrostatic interactions that are highly sensitive to temperature, ionic strength, arginine methylation, and splicing. Sequence determinants are used to identify proteins found in both membraneless organelles and cell adhesion. Moreover, the bodies provide an alternative solvent environment that can concentrate single-stranded DNA but largely exclude double-stranded DNA. We propose that phase separation of disordered proteins containing weakly interacting blocks is a general mechanism for forming regulated, membraneless organelles. Intrinsically disordered N terminus of Ddx4 forms organelles in cells and in vitro Phase transition to form organelles is driven by electrostatic interactions Methylation, ionic strength, and temperature changes can dissolve the organelles Sequence determinants of formation are common in membraneless organelle proteins
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Affiliation(s)
- Timothy J Nott
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada; Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, UK
| | - Evangelia Petsalaki
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
| | - Patrick Farber
- Research Institute, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Dylan Jervis
- Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7, Canada
| | - Eden Fussner
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
| | | | | | - David P Bazett-Jones
- Research Institute, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada
| | - Tony Pawson
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
| | - Julie D Forman-Kay
- Research Institute, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
| | - Andrew J Baldwin
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, UK.
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Shigella infection interferes with SUMOylation and increases PML-NB number. PLoS One 2015; 10:e0122585. [PMID: 25848798 PMCID: PMC4388590 DOI: 10.1371/journal.pone.0122585] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 02/20/2015] [Indexed: 01/08/2023] Open
Abstract
Shigellosis is a severe diarrheal disease that affects hundreds of thousands of individuals resulting in significant morbidity and mortality worldwide. Shigellosis is caused by Shigella spp., a gram-negative bacterium that uses a Type 3 Secretion System (T3SS) to deliver effector proteins into the cytosol of infected human cells. Shigella infection triggers multiple signaling programs that result in a robust host transcriptional response that includes the induction of multiple proinflammatory cytokines. PML nuclear bodies (PML-NBs) are dynamic subnuclear structures that coordinate immune signaling programs and have a demonstrated role in controlling viral infection. We show that PML-NB number increases upon Shigella infection. We examined the effects of Shigella infection on SUMOylation and found that upon Shigella infection the localization of SUMOylated proteins is altered and the level of SUMOylated proteins decreases. Although Shigella infection does not alter the abundance of SUMO activating enzymes SAE1 or SAE2, it dramatically decreases the level of the SUMO conjugating enzyme Ubc9. All Shigella-induced alterations to the SUMOylation system are dependent upon a T3SS. Thus, we demonstrate that Shigella uses one or more T3SS effectors to influence both PML-NB number and the SUMOylation machinery in human cells.
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41
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Jin G, Gao Y, Lin HK. Cytoplasmic PML: from molecular regulation to biological functions. J Cell Biochem 2014; 115:812-8. [PMID: 24288198 DOI: 10.1002/jcb.24727] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 11/19/2013] [Indexed: 01/18/2023]
Abstract
The tumor suppressor promyelocytic leukemia protein (PML) is predominantly localized in the nucleus, where it is essential for the formation and stabilization of the PML nuclear bodies (PML-NBs). PML-NBs are involved in the regulation of numerous cellular functions, such as tumorigenesis, DNA damage and antiviral responses. Despite its nuclear localization, a small portion of PML has been found in the cytoplasm. A number of studies recently demonstrated that the cytoplasmic PML (cPML) has diverse functions in many cellular processes including tumorigenesis, metabolism, antiviral responses, cell cycle regulation, and laminopothies. In this prospective, we will summarize the current viewpoints on the regulation and biological significance of cPML and discuss the important questions that still need to be further answered.
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Affiliation(s)
- Guoxiang Jin
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, 77030
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JC virus inclusions in progressive multifocal leukoencephalopathy: scaffolding promyelocytic leukemia nuclear bodies grow with cell cycle transition through an S-to-G2-like state in enlarging oligodendrocyte nuclei. J Neuropathol Exp Neurol 2014; 73:442-53. [PMID: 24709678 PMCID: PMC3995394 DOI: 10.1097/nen.0000000000000066] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
In progressive multifocal leukoencephalopathy, JC virus–infected oligodendroglia display 2 distinct patterns of intranuclear viral inclusions: full inclusions in which progeny virions are present throughout enlarged nuclei and dot-shaped inclusions in which virions are clustered in subnuclear domains termed “promyelocytic leukemia nuclear bodies” (PML-NBs). Promyelocytic leukemia nuclear bodies may serve a scaffolding role in viral progeny production. We analyzed the formation process of intranuclear viral inclusions by morphometry and assessed PML-NB alterations in the brains of 2 patients with progressive multifocal leukoencephalopathy. By immunohistochemistry, proliferating cell nuclear antigen was most frequently detected in smaller nuclei; cyclin A was detected in larger nuclei. This suggests an S-to-G2 cell cycle transition in infected cells associated with nuclear enlargement. Sizes of PML-NBs were variable, but they were usually either small speckles 200 to 400 nm in diameter or distinct spherical shells with a diameter of 1 μm or more. By confocal microscopy, JC virus capsid proteins were associated with both small and large PML-NBs, but disruption of large PML-NBs was observed by ground-state depletion fluorescence nanoscopy. Clusters of progeny virions were also detected by electron microscopy. Our data suggest that, in progressive multifocal leukoencephalopathy, JC virus produces progeny virions in enlarging oligodendrocyte nuclei in association with growing PML-NBs and with cell cycle transition through an S-to-G2-like state.
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Palibrk V, Lång E, Lång A, Schink KO, Rowe AD, Bøe SO. Promyelocytic leukemia bodies tether to early endosomes during mitosis. Cell Cycle 2014; 13:1749-55. [PMID: 24675887 DOI: 10.4161/cc.28653] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
During mitosis the nuclear envelope breaks down, leading to potential interactions between cytoplasmic and nuclear components. PML bodies are nuclear structures with tumor suppressor and antiviral functions. Early endosomes, on the other hand, are cytoplasmic vesicles involved in transport and growth factor signaling. Here we demonstrate that PML bodies form stable interactions with early endosomes immediately following entry into mitosis. The 2 compartments remain stably associated throughout mitosis and dissociate in the cytoplasm of newly divided daughter cells. We also show that a minor subset of PML bodies becomes anchored to the mitotic spindle poles during cell division. The study demonstrates a stable mitosis-specific interaction between a cytoplasmic and a nuclear compartment.
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Affiliation(s)
- Vuk Palibrk
- Department of Microbiology and Department of Medical Biochemistry; Oslo University Hospital and University of Oslo; Oslo, Norway
| | - Emma Lång
- Department of Microbiology and Department of Medical Biochemistry; Oslo University Hospital and University of Oslo; Oslo, Norway
| | - Anna Lång
- Department of Microbiology and Department of Medical Biochemistry; Oslo University Hospital and University of Oslo; Oslo, Norway
| | - Kay Oliver Schink
- Department of Biochemistry; Institute for Cancer Research; The Norwegian Radium Hospital; Oslo University Hospital; Oslo, Norway
| | - Alexander D Rowe
- Department of Microbiology and Department of Medical Biochemistry; Oslo University Hospital and University of Oslo; Oslo, Norway
| | - Stig Ove Bøe
- Department of Microbiology and Department of Medical Biochemistry; Oslo University Hospital and University of Oslo; Oslo, Norway
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44
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Bernardi R, Pandolfi PP. A Dialog on the First 20 Years of PML Research and the Next 20 Ahead. Front Oncol 2014; 4:23. [PMID: 24575390 PMCID: PMC3919016 DOI: 10.3389/fonc.2014.00023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 01/27/2014] [Indexed: 11/21/2022] Open
Abstract
This introductory article has been written in the form of a conversation between Pier Paolo Pandolfi, Director of the Cancer Center of Beth Israel Deaconess Medical Center in Boston, and Rosa Bernardi, a former post-doctoral fellow in the laboratory of Dr. Pandolfi, now principal investigator at San Raffaele Scientific Institute in Milan, Italy. We have chosen this atypical review format because we want to offer to our readers a more direct and personal perspective on the first 20 years of research over the promyelocytic leukemia gene. This article begins as an interview, but soon transforms into a dialog where we exchange our thoughts on a number of issues around the past, present, and future research over the biology of PML. We were particularly keen on emphasizing the aspects that we find most interesting or challenging, therefore, we warn our readers that this will not be a comprehensive essay but rather a very personal view of what has been, is, and will be exciting and interesting in the PML world, in our opinion.
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Affiliation(s)
- Rosa Bernardi
- Division of Molecular Oncology, San Raffaele Scientific Institute , Milano , Italy
| | - Pier Paolo Pandolfi
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School , Boston, MA , USA
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45
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Stepp WH, Meyers JM, McBride AA. Sp100 provides intrinsic immunity against human papillomavirus infection. mBio 2013; 4:e00845-13. [PMID: 24194542 PMCID: PMC3892783 DOI: 10.1128/mbio.00845-13] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 10/10/2013] [Indexed: 02/07/2023] Open
Abstract
UNLABELLED Most DNA viruses associate with, and reorganize, nuclear domain 10 (ND10) bodies upon entry into the host nucleus. In this study, we examine the roles of the ND10 components PML, Sp100, and Daxx in the establishment of human papillomavirus type 18 (HPV18) infection of primary human keratinocytes. HPV18 DNA or HPV18 quasivirus was introduced into primary human keratinocytes depleted of each ND10 protein by small interfering RNA technology, and genome establishment was determined by using a quantitative immortalization assay and measurements of viral transcription and DNA replication. Keratinocyte depletion of Sp100 resulted in a substantial increase in the number of HPV18-immortalized colonies and a corresponding increase in viral transcription and DNA replication. However, Sp100 repressed viral transcription and replication only during the initial stages of viral establishment, suggesting that Sp100 acts as a repressor of incoming HPV DNA. IMPORTANCE The intrinsic immune system provides a first-line defense against invading pathogens. Host cells contain nuclear bodies (ND10) that are important for antiviral defense, yet many DNA viruses localize here upon cell entry. However, viruses also disrupt, reorganize, and modify individual components of the bodies. In this study, we show that one of the ND10 components, Sp100, limits the infection of human skin cells by human papillomavirus (HPV). HPVs are important pathogens that cause many types of infection of the cutaneous and mucosal epithelium and are the causative agents of several human cancers. Understanding how host cells counteract HPV infection could provide insight into antimicrobial therapies that could limit initial infection.
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Affiliation(s)
| | - Jordan M. Meyers
- Laboratory of Viral Diseases, NIAID, NIH, Bethesda, Maryland, USA
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46
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Buchberger E, El Harchi M, Payrhuber D, Zommer A, Schauer D, Simonitsch-Klupp I, Bilban M, Brostjan C. Overexpression of the transcriptional repressor complex BCL-6/BCoR leads to nuclear aggregates distinct from classical aggresomes. PLoS One 2013; 8:e76845. [PMID: 24146931 PMCID: PMC3795655 DOI: 10.1371/journal.pone.0076845] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2013] [Accepted: 08/30/2013] [Indexed: 01/27/2023] Open
Abstract
Nuclear inclusions of aggregated proteins have primarily been characterized for molecules with aberrant poly-glutamine repeats and for mutated or structurally altered proteins. They were termed “nuclear aggresomes” and misfolding was shown to promote association with molecular chaperones and proteasomes. Here, we report that two components of a transcriptional repressor complex (BCL-6 and BCoR) of wildtype amino acid sequence can independently or jointly induce the formation of nuclear aggregates when overexpressed. The observation that the majority of cells rapidly downregulate BCL-6/BCoR levels, supports the notion that expression of these proteins is under tight control. The inclusions occur when BCL-6/BCoR expression exceeds 150-fold of endogenous levels. They preferentially develop in the nucleus by a gradual increase in aggregate size to form large, spheroid structures which are not associated with heat shock proteins or marked by ubiquitin. In contrast, we find the close association of BCL-6/BCoR inclusions with PML bodies and a reduction in aggregation upon the concomitant overexpression of histone deacetylases or heat shock protein 70. In summary, our data offer a perspective on nuclear aggregates distinct from classical “nuclear aggresomes”: Large complexes of spheroid structure can evolve in the nucleus without being marked by the cellular machinery for protein refolding and degradation. However, nuclear proteostasis can be restored by balancing the levels of chaperones.
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Affiliation(s)
- Elisabeth Buchberger
- Department of Surgery, Medical University of Vienna, Vienna General Hospital, Vienna, Austria
| | - Miriam El Harchi
- Department of Surgery, Medical University of Vienna, Vienna General Hospital, Vienna, Austria
| | - Dietmar Payrhuber
- Department of Surgery, Medical University of Vienna, Vienna General Hospital, Vienna, Austria
| | - Anna Zommer
- Department of Surgery, Medical University of Vienna, Vienna General Hospital, Vienna, Austria
| | - Dominic Schauer
- Department of Surgery, Medical University of Vienna, Vienna General Hospital, Vienna, Austria
| | - Ingrid Simonitsch-Klupp
- Clinical Institute of Pathology, Medical University of Vienna, Vienna General Hospital, Vienna, Austria
| | - Martin Bilban
- Core Facility Genomics, Medical University of Vienna, Vienna General Hospital, Vienna, Austria
| | - Christine Brostjan
- Department of Surgery, Medical University of Vienna, Vienna General Hospital, Vienna, Austria
- * E-mail:
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47
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Jin G, Wang YJ, Lin HK. Emerging Cellular Functions of Cytoplasmic PML. Front Oncol 2013; 3:147. [PMID: 23761861 PMCID: PMC3674320 DOI: 10.3389/fonc.2013.00147] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 05/21/2013] [Indexed: 11/23/2022] Open
Abstract
The tumor suppressor promyelocytic leukemia protein (PML) is located primarily in the nucleus, where it is the scaffold component of the PML nuclear bodies (PML-NBs). PML-NBs regulate multiple cellular functions, such as apoptosis, senescence, DNA damage response, and resistance to viral infection. Despite its nuclear localization, a small portion of PML has been identified in the cytoplasm. The cytoplasmic PML (cPML) could be originally derived from the retention of exported nuclear PML (nPML). In addition, bona fide cPML isoforms devoid of nuclear localization signal (NLS) have also been identified. Recently, emerging evidence showed that cPML performs its specific cellular functions in tumorigenesis, glycolysis, antiviral responses, laminopothies, and cell cycle regulation. In this review, we will summarize the emerging roles of cPML in cellular functions.
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Affiliation(s)
- Guoxiang Jin
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center , Houston, TX , USA
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48
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Schmitz ML, Grishina I. Regulation of the tumor suppressor PML by sequential post-translational modifications. Front Oncol 2012; 2:204. [PMID: 23293771 PMCID: PMC3533183 DOI: 10.3389/fonc.2012.00204] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Accepted: 12/11/2012] [Indexed: 01/08/2023] Open
Abstract
Post-translational modifications (PTMs) regulate multiple biological functions of the promyelocytic leukemia (PML) protein and also the fission, disassembly, and rebuilding of PML nuclear bodies (PML-NBs) during the cell cycle. Pathway-specific PML modification patterns ensure proper signal output from PML-NBs that suit the specific functional requirements. Here we comprehensively review the signaling pathways and enzymes that modify PML and also the oncogenic PML-RARα fusion protein. Many PTMs occur in a hierarchical and timely organized fashion. Phosphorylation or acetylation constitutes typical starting points for many PML modifying events, while degradative ubiquitination is an irreversible end point of the modification cascade. As this hierarchical organization of PTMs frequently turns phosphorylation events as primordial events, kinases or phosphatases regulating PML phosphorylation may be interesting drug targets to manipulate the downstream modifications and thus the stability and function of PML or PML-RARα.
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Affiliation(s)
- M Lienhard Schmitz
- Department of Biochemistry, Medical Faculty, Justus Liebig University, German Center for Lung Research Giessen, Germany
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49
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Kwan PS, Lau CC, Chiu YT, Man C, Liu J, Tang KD, Wong YC, Ling MT. Daxx regulates mitotic progression and prostate cancer predisposition. Carcinogenesis 2012; 34:750-9. [PMID: 23239745 DOI: 10.1093/carcin/bgs391] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Mitotic progression of mammalian cells is tightly regulated by the E3 ubiquitin ligase anaphase promoting complex (APC)/C. Deregulation of APC/C is frequently observed in cancer cells and is suggested to contribute to chromosome instability and cancer predisposition. In this study, we identified Daxx as a novel APC/C inhibitor frequently overexpressed in prostate cancer. Daxx interacts with the APC/C coactivators Cdc20 and Cdh1 in vivo, with the binding of Cdc20 dependent on the consensus destruction boxes near the N-terminal of the Daxx protein. Ectopic expression of Daxx, but not the D-box deleted mutant (DaxxΔD-box), inhibited the degradation of APC/Cdc20 and APC/Cdh1 substrates, leading to a transient delay in mitotic progression. Daxx is frequently upregulated in prostate cancer tissues; the expression level positively correlated with the Gleason score and disease metastasis (P = 0.027 and 0.032, respectively). Furthermore, ectopic expression of Daxx in a non-malignant prostate epithelial cell line induced polyploidy under mitotic stress. Our data suggest that Daxx may function as a novel APC/C inhibitor, which promotes chromosome instability during prostate cancer development.
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Affiliation(s)
- Pak Shing Kwan
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Qld, Australia
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50
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The arsenic-based cure of acute promyelocytic leukemia promotes cytoplasmic sequestration of PML and PML/RARA through inhibition of PML body recycling. Blood 2012; 120:847-57. [DOI: 10.1182/blood-2011-10-388496] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Arsenic in the form of arsenic trioxide (ATO) is used as a therapeutic drug for treatment of acute promyelocytic leukemia (APL). The mechanism by which this agent cures this disease was previously shown to involve direct interactions between ATO and the promyelocytic leukemia protein (PML), as well as accelerated degradation of the APL-associated fusion oncoprotein PML/retinoic acid receptor α (RARA). Here we investigated the fate of PML-generated nuclear structures called PML bodies in ATO-treated cells. We found that ATO inhibits formation of progeny PML bodies while it stabilizes cytoplasmic precursor compartments, referred to as cytoplasmic assemblies of PML and nucleoporins (CyPNs), after cell division. This block in PML body recycling is readily detected at pharmacologic relevant ATO concentrations (0.02-0.5μM) that do not cause detectable cell-cycle defects, and it does not require modification of PML by SUMOylation. In addition, PML and PML/RARA carrying mutations previously identified in ATO-resistant APL patients are impeded in their ability to become sequestered within CyPNs. Thus, ATO may inhibit nuclear activities of PML and PML/RARA in postmitotic cells through CyPN-dependent cytoplasmic sequestration.
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