1
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Fernandez MK, Sinha M, Zidan M, Renz M. Nuclear actin filaments - a historical perspective. Nucleus 2024; 15:2320656. [PMID: 38384139 PMCID: PMC10885181 DOI: 10.1080/19491034.2024.2320656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 02/14/2024] [Indexed: 02/23/2024] Open
Abstract
The view on nuclear filaments formed by non-skeletal β-actin has significantly changed over the decades. Initially, filamentous actin was observed in amphibian oocyte nuclei and only under specific cell stress conditions in mammalian cell nuclei. Improved labeling and imaging technologies have permitted insights into a transient but microscopically apparent filament network that is relevant for chromatin organization, biomechanics of the mammalian cell nucleus, gene expression, and DNA damage repair. Here, we will provide a historical perspective on the developing insight into nuclear actin filaments.
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Affiliation(s)
| | - Molika Sinha
- Gynecologic Oncology Division, School of Medicine Stanford University, Palo Alto, CA, USA
| | - Mia Zidan
- Gynecologic Oncology Division, School of Medicine Stanford University, Palo Alto, CA, USA
| | - Malte Renz
- Gynecologic Oncology Division, School of Medicine Stanford University, Palo Alto, CA, USA
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2
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Rios EI, Hunsberger IL, Johnson JL. Insights into Hsp90 mechanism and in vivo functions learned from studies in the yeast, Saccharomyces cerevisiae. Front Mol Biosci 2024; 11:1325590. [PMID: 38389899 PMCID: PMC10881880 DOI: 10.3389/fmolb.2024.1325590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 01/22/2024] [Indexed: 02/24/2024] Open
Abstract
The molecular chaperone Hsp90 (Heat shock protein, 90 kDa) is an abundant and essential cytosolic protein required for the stability and/or folding of hundreds of client proteins. Hsp90, along with helper cochaperone proteins, assists client protein folding in an ATP-dependent pathway. The laboratory of Susan Lindquist, in collaboration with other researchers, was the first to establish the yeast Saccharomyces cerevisiae as a model organism to study the functional interaction between Hsp90 and clients. Important insights from studies in her lab were that Hsp90 is essential, and that Hsp90 functions and cochaperone interactions are highly conserved between yeast and mammalian cells. Here, we describe key mechanistic insights into the Hsp90 folding cycle that were obtained using the yeast system. We highlight the early contributions of the laboratory of Susan Lindquist and extend our analysis into the broader use of the yeast system to analyze the understanding of the conformational cycle of Hsp90 and the impact of altered Hsp90 function on the proteome.
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Affiliation(s)
- Erick I Rios
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, United States
| | - Isabel L Hunsberger
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, United States
| | - Jill L Johnson
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, United States
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3
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Shevelyov YY. Interactions of Chromatin with the Nuclear Lamina and Nuclear Pore Complexes. Int J Mol Sci 2023; 24:15771. [PMID: 37958755 PMCID: PMC10649103 DOI: 10.3390/ijms242115771] [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: 10/06/2023] [Revised: 10/26/2023] [Accepted: 10/29/2023] [Indexed: 11/15/2023] Open
Abstract
Heterochromatin and euchromatin form different spatial compartments in the interphase nucleus, with heterochromatin being localized mainly at the nuclear periphery. The mechanisms responsible for peripheral localization of heterochromatin are still not fully understood. The nuclear lamina and nuclear pore complexes were obvious candidates for the role of heterochromatin binders. This review is focused on recent studies showing that heterochromatin interactions with the nuclear lamina and nuclear pore complexes maintain its peripheral localization. Differences in chromatin interactions with the nuclear envelope in cell populations and in individual cells are also discussed.
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Affiliation(s)
- Yuri Y Shevelyov
- Laboratory of Analysis of Gene Regulation, National Research Centre "Kurchatov Institute", Kurchatov Sq. 2, 123182 Moscow, Russia
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4
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Backe SJ, Mollapour M, Woodford MR. Saccharomyces cerevisiae as a tool for deciphering Hsp90 molecular chaperone function. Essays Biochem 2023; 67:781-795. [PMID: 36912239 PMCID: PMC10497724 DOI: 10.1042/ebc20220224] [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: 12/21/2022] [Revised: 02/01/2023] [Accepted: 02/03/2023] [Indexed: 03/14/2023]
Abstract
Yeast is a valuable model organism for their ease of genetic manipulation, rapid growth rate, and relative similarity to higher eukaryotes. Historically, Saccharomyces cerevisiae has played a major role in discovering the function of complex proteins and pathways that are important for human health and disease. Heat shock protein 90 (Hsp90) is a molecular chaperone responsible for the stabilization and activation of hundreds of integral members of the cellular signaling network. Much important structural and functional work, including many seminal discoveries in Hsp90 biology are the direct result of work carried out in S. cerevisiae. Here, we have provided a brief overview of the S. cerevisiae model system and described how this eukaryotic model organism has been successfully applied to the study of Hsp90 chaperone function.
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Affiliation(s)
- Sarah J. Backe
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
- Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
| | - Mehdi Mollapour
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
- Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
| | - Mark R. Woodford
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
- Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
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5
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Rubio LS, Gross DS. Dynamic coalescence of yeast Heat Shock Protein genes bypasses the requirement for actin. Genetics 2023; 223:iyad006. [PMID: 36659814 PMCID: PMC10319981 DOI: 10.1093/genetics/iyad006] [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: 07/22/2022] [Revised: 07/22/2022] [Accepted: 01/03/2023] [Indexed: 01/21/2023] Open
Abstract
Nuclear actin has been implicated in dynamic chromatin rearrangements in diverse eukaryotes. In mammalian cells, it is required to reposition double-strand DNA breaks to enable homologous recombination repair and to enhance transcription by facilitating RNA Pol II recruitment to gene promoters. In the yeast Saccharomyces cerevisiae, nuclear actin modulates interphase chromosome dynamics and is required to reposition the induced INO1 gene to the nuclear periphery. Here, we have investigated the role of actin in driving intergenic interactions between Heat Shock Factor 1 (Hsf1)-regulated Heat Shock Protein (HSP) genes in budding yeast. These genes, dispersed on multiple chromosomes, dramatically reposition following exposure of cells to acute thermal stress, leading to their clustering within dynamic biomolecular condensates. Using an auxin-induced degradation strategy, we found that conditional depletion of nucleators of either linear or branched F-actin (Bni1/Bnr1 and Arp2, respectively) had little or no effect on heat shock-induced HSP gene coalescence or transcription. In addition, we found that pretreatment of cells with latrunculin A, an inhibitor of both filamentous and monomeric actin, failed to affect intergenic interactions between activated HSP genes and their heat shock-induced intragenic looping and folding. Moreover, latrunculin A pretreatment had little effect on HSP gene expression at either RNA or protein levels. In notable contrast, we confirmed that repositioning of activated INO1 to the nuclear periphery and its proper expression do require actin. Collectively, our work suggests that transcriptional activation and 3D genome restructuring of thermally induced, Hsf1-regulated genes can occur in the absence of actin.
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Affiliation(s)
- Linda S Rubio
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - David S Gross
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
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6
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Gunasekaran S, Miyagawa Y, Miyamoto K. Actin nucleoskeleton in embryonic development and cellular differentiation. Curr Opin Cell Biol 2022; 76:102100. [DOI: 10.1016/j.ceb.2022.102100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 03/28/2022] [Accepted: 04/22/2022] [Indexed: 11/03/2022]
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7
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Yu C, Wang ZG, Ma AX, Liu SL, Pang DW. Uncovering the F-Actin-Based Nuclear Egress Mechanism of Newly Synthesized Influenza A Virus Ribonucleoprotein Complexes by Single-Particle Tracking. Anal Chem 2022; 94:5624-5633. [PMID: 35357801 DOI: 10.1021/acs.analchem.1c05387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nuclear trafficking of viral genome is an essential cellular process in the life cycles of viruses. Despite substantial progress in uncovering a wide variety of complicated mechanisms of virus entry, intracellular transport of viral components, virus assembly, and egress, the temporal and spatial dynamics of viral genes trafficking within the nucleus remains poorly understood. Herein, using single-particle tracking, we explored the real-time dynamic nuclear trafficking of influenza A virus (IAV) genes packaged as the viral ribonucleoprotein complexes (vRNPs) by combining a four-plasmid DNA transfection system for the reconstruction of green fluorescent protein (GFP)-labeled vRNPs and a spinning disk super-resolution fluorescence microscope. We found that IAV infection significantly induced the formation of actin microfilaments (F-actin) in the nucleus. In combination with the fluorescent protein-tagged nuclear F-actin probe, we visualized the directed movement of GFP-labeled vRNPs foci along the nuclear F-actin with a speed of 0.18 μm/s, which is similar to the microfilaments-dependent slow directed motion of IAVs in the cytoplasm. The disruption of nuclear F-actin after treatment with microfilament inhibitors caused a considerable decrease in vRNPs motility and suppressed the nuclear export of newly produced vRNPs, indicating that the slow, directed movement plays a crucial role in facilitating the nuclear egress of vRNPs. Our findings identified a nuclear F-actin-dependent pathway for IAV vRNPs transporting from the nucleus into the cytoplasm, which may in turn uncover a novel target for antiviral treatment.
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Affiliation(s)
- Cong Yu
- College of Chemistry and Molecular Sciences, State Key Laboratory of Virology, The Institute for Advanced Studies, and Wuhan Institute of Biotechnology, Wuhan University, Wuhan 430072, P. R. China
| | - Zhi-Gang Wang
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin 300071, P. R. China
| | - Ai-Xin Ma
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin 300071, P. R. China
| | - Shu-Lin Liu
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin 300071, P. R. China
| | - Dai-Wen Pang
- College of Chemistry and Molecular Sciences, State Key Laboratory of Virology, The Institute for Advanced Studies, and Wuhan Institute of Biotechnology, Wuhan University, Wuhan 430072, P. R. China.,State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin 300071, P. R. China
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8
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Rubin J, van Wijnen AJ, Uzer G. Architectural control of mesenchymal stem cell phenotype through nuclear actin. Nucleus 2022; 13:35-48. [PMID: 35133922 PMCID: PMC8837231 DOI: 10.1080/19491034.2022.2029297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
There is growing appreciation that architectural components of the nucleus regulate gene accessibility by altering chromatin organization. While nuclear membrane connector proteins link the mechanosensitive actin cytoskeleton to the nucleoskeleton, actin’s contribution to the inner architecture of the nucleus remains enigmatic. Control of actin transport into the nucleus, plus the presence of proteins that control actin structure (the actin tool-box) within the nucleus, suggests that nuclear actin may support biomechanical regulation of gene expression. Cellular actin structure is mechanoresponsive: actin cables generated through forces experienced at the plasma membrane transmit force into the nucleus. We posit that dynamic actin remodeling in response to such biomechanical cues provides a novel level of structural control over the epigenetic landscape. We here propose to bring awareness to the fact that mechanical forces can promote actin transfer into the nucleus and control structural arrangements as illustrated in mesenchymal stem cells, thereby modulating lineage commitment.
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Affiliation(s)
- Janet Rubin
- Department of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Andre J van Wijnen
- Department of Biochemistry, University of Vermont Medical School, Burlington, Vt, USA
| | - Gunes Uzer
- Department of Mechanical & Biomedical Engineering, Boise State University, Boise, ID, USA
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9
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Freeman BC. Genome Organization and Dynamics Specialty Grand Challenge. Front Mol Biosci 2022; 8:818707. [PMID: 35036413 PMCID: PMC8758561 DOI: 10.3389/fmolb.2021.818707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 12/06/2021] [Indexed: 11/29/2022] Open
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10
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Hansen JC, Maeshima K, Hendzel MJ. The solid and liquid states of chromatin. Epigenetics Chromatin 2021; 14:50. [PMID: 34717733 PMCID: PMC8557566 DOI: 10.1186/s13072-021-00424-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 10/22/2021] [Indexed: 12/14/2022] Open
Abstract
The review begins with a concise description of the principles of phase separation. This is followed by a comprehensive section on phase separation of chromatin, in which we recount the 60 years history of chromatin aggregation studies, discuss the evidence that chromatin aggregation intrinsically is a physiologically relevant liquid-solid phase separation (LSPS) process driven by chromatin self-interaction, and highlight the recent findings that under specific solution conditions chromatin can undergo liquid-liquid phase separation (LLPS) rather than LSPS. In the next section of the review, we discuss how certain chromatin-associated proteins undergo LLPS in vitro and in vivo. Some chromatin-binding proteins undergo LLPS in purified form in near-physiological ionic strength buffers while others will do so only in the presence of DNA, nucleosomes, or chromatin. The final section of the review evaluates the solid and liquid states of chromatin in the nucleus. While chromatin behaves as an immobile solid on the mesoscale, nucleosomes are mobile on the nanoscale. We discuss how this dual nature of chromatin, which fits well the concept of viscoelasticity, contributes to genome structure, emphasizing the dominant role of chromatin self-interaction.
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Affiliation(s)
- Jeffrey C Hansen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, 80523, USA.
| | - Kazuhiro Maeshima
- Genome Dynamics Laboratory, National Institute of Genetics, and Department of Genetics, Sokendai (Graduate University for Advanced Studies), Mishima, Shizuoka, 411-8540, Japan.
| | - Michael J Hendzel
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
- Department of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
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11
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Belmont AS. Nuclear Compartments: An Incomplete Primer to Nuclear Compartments, Bodies, and Genome Organization Relative to Nuclear Architecture. Cold Spring Harb Perspect Biol 2021; 14:cshperspect.a041268. [PMID: 34400557 PMCID: PMC9248822 DOI: 10.1101/cshperspect.a041268] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This work reviews nuclear compartments, defined broadly to include distinct nuclear structures, bodies, and chromosome domains. It first summarizes original cytological observations before comparing concepts of nuclear compartments emerging from microscopy versus genomic approaches and then introducing new multiplexed imaging approaches that promise in the future to meld both approaches. I discuss how previous models of radial distribution of chromosomes or the binary division of the genome into A and B compartments are now being refined by the recognition of more complex nuclear compartmentalization. The poorly understood question of how these nuclear compartments are established and maintained is then discussed, including through the modern perspective of phase separation, before moving on to address possible functions of nuclear compartments, using the possible role of nuclear speckles in modulating gene expression as an example. Finally, the review concludes with a discussion of future questions for this field.
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Affiliation(s)
- Andrew S Belmont
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, Illinois 61801, USA
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12
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Record J, Saeed MB, Venit T, Percipalle P, Westerberg LS. Journey to the Center of the Cell: Cytoplasmic and Nuclear Actin in Immune Cell Functions. Front Cell Dev Biol 2021; 9:682294. [PMID: 34422807 PMCID: PMC8375500 DOI: 10.3389/fcell.2021.682294] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 07/06/2021] [Indexed: 12/12/2022] Open
Abstract
Actin cytoskeletal dynamics drive cellular shape changes, linking numerous cell functions to physiological and pathological cues. Mutations in actin regulators that are differentially expressed or enriched in immune cells cause severe human diseases known as primary immunodeficiencies underscoring the importance of efficienct actin remodeling in immune cell homeostasis. Here we discuss recent findings on how immune cells sense the mechanical properties of their environement. Moreover, while the organization and biochemical regulation of cytoplasmic actin have been extensively studied, nuclear actin reorganization is a rapidly emerging field that has only begun to be explored in immune cells. Based on the critical and multifaceted contributions of cytoplasmic actin in immune cell functionality, nuclear actin regulation is anticipated to have a large impact on our understanding of immune cell development and functionality.
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Affiliation(s)
- Julien Record
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institute, Stockholm, Sweden
| | - Mezida B. Saeed
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institute, Stockholm, Sweden
| | - Tomas Venit
- Science Division, Biology Program, New York University Abu Dhabi (NYUAD), Abu Dhabi, United Arab Emirates
| | - Piergiorgio Percipalle
- Science Division, Biology Program, New York University Abu Dhabi (NYUAD), Abu Dhabi, United Arab Emirates
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Lisa S. Westerberg
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institute, Stockholm, Sweden
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13
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Venit T, El Said NH, Mahmood SR, Percipalle P. A dynamic actin-dependent nucleoskeleton and cell identity. J Biochem 2021; 169:243-257. [PMID: 33351909 DOI: 10.1093/jb/mvaa133] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 10/27/2020] [Indexed: 12/19/2022] Open
Abstract
Actin is an essential regulator of cellular functions. In the eukaryotic cell nucleus, actin regulates chromatin as a bona fide component of chromatin remodelling complexes, it associates with nuclear RNA polymerases to regulate transcription and is involved in co-transcriptional assembly of nascent RNAs into ribonucleoprotein complexes. Actin dynamics are, therefore, emerging as a major regulatory factor affecting diverse cellular processes. Importantly, the involvement of actin dynamics in nuclear functions is redefining the concept of nucleoskeleton from a rigid scaffold to a dynamic entity that is likely linked to the three-dimensional organization of the nuclear genome. In this review, we discuss how nuclear actin, by regulating chromatin structure through phase separation may contribute to the architecture of the nuclear genome during cell differentiation and facilitate the expression of specific gene programs. We focus specifically on mitochondrial genes and how their dysregulation in the absence of actin raises important questions about the role of cytoskeletal proteins in regulating chromatin structure. The discovery of a novel pool of mitochondrial actin that serves as 'mitoskeleton' to facilitate organization of mtDNA supports a general role for actin in genome architecture and a possible function of distinct actin pools in the communication between nucleus and mitochondria.
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Affiliation(s)
- Tomas Venit
- Science Division, Biology Program, New York University Abu Dhabi (NYUAD), PO Box 129188, Abu Dhabi United Arab Emirates
| | - Nadine Hosny El Said
- Science Division, Biology Program, New York University Abu Dhabi (NYUAD), PO Box 129188, Abu Dhabi United Arab Emirates
| | - Syed Raza Mahmood
- Science Division, Biology Program, New York University Abu Dhabi (NYUAD), PO Box 129188, Abu Dhabi United Arab Emirates.,Department of Biology, New York University, 100 Washington Square East, 1009 Silver Center, New York, NY 10003, USA
| | - Piergiorgio Percipalle
- Science Division, Biology Program, New York University Abu Dhabi (NYUAD), PO Box 129188, Abu Dhabi United Arab Emirates.,Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Svante Arrhenius väg 20C, 114 18 Stockholm, Sweden
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14
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Shindo T, Ihashi S, Sakamoto Y, Okuno T, Tomikawa J, Miyamoto K. Visualization of endogenous nuclear F-actin in mouse embryos reveals abnormal actin assembly after somatic cell nuclear transfer. J Biochem 2021; 169:303-311. [PMID: 33169144 DOI: 10.1093/jb/mvaa125] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 10/25/2020] [Indexed: 01/13/2023] Open
Abstract
Actin in the nucleus, referred to as nuclear actin, is involved in a variety of nuclear events. Nuclear actin is present as a globular (G-actin) and filamentous form (F-actin), and dynamic assembly/disassembly of nuclear actin profoundly affects nuclear functions. However, it is still challenging to observe endogenous nuclear F-actin. Here, we present a condition to visualize endogenous nuclear F-actin of mouse zygotes using different fixation methods. Zygotes fixed with paraformaldehyde and treated with fluorescently conjugated phalloidin show both short and long actin filaments in their pronuclei. Short nuclear actin filaments are characteristic of phalloidin staining, rather than the consequence of severing actin filaments by the fixation process, since long nuclear actin filaments probed with the nuclear actin chromobody are not disassembled into short filaments after fixation with paraformaldehyde. Furthermore, we find that nuclear actin assembly is impaired after somatic cell nuclear transfer (SCNT), suggesting abnormal nucleoskeleton structures in SCNT embryos. Taken together, our presented method for visualizing nuclear F-actin with phalloidin can be used to observe the states of nuclear actin assembly, and revealed improper reprogramming of actin nucleoskeleton structures in cloned mouse embryos.
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Affiliation(s)
- Taiki Shindo
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama 649-6493, Japan
| | - Shunya Ihashi
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama 649-6493, Japan
| | - Yuko Sakamoto
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama 649-6493, Japan
| | - Tomomi Okuno
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama 649-6493, Japan
| | - Junko Tomikawa
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama 649-6493, Japan
| | - Kei Miyamoto
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama 649-6493, Japan
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15
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Shi K, Yang L, Du X, Guo D, Xue L. Molecular chaperone Hsp90 protects KCBP from degradation by proteasome in Dunaliella salina cells. Folia Microbiol (Praha) 2021; 66:949-957. [PMID: 34240332 DOI: 10.1007/s12223-021-00897-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 07/01/2021] [Indexed: 11/26/2022]
Abstract
Kinesin-like calmodulin-binding protein (KCBP) is a unique kinesin with half kinesin and half myosin, with kinesin motor domain at C-terminus and myosin tail homology region 4 (MyTH4) and band 4.1, ezrin, radixin, moesin (FERM) domains at N-terminus. The special structure endows KCBP multi-intracellular functions, including cell division, trichome morphogenesis in plants, and flagellar function in algae. However, little is known about the molecular mechanism underlying these functions. Here, we identified a molecular chaperone Hsp90 as a novel binding partner with KCBP in Dunaliella salina using a yeast two-hybrid screen. Further analysis showed that Hsp90 interacted with both the N-terminal and C-terminal of DsKCBP. Since Hsp90 was involved in the stability and proteolytic turnover of numerous proteins, whether Hsp90 regulated the degradation of DsKCBP was investigated. Our results showed that both Hsp90 and DsKCBP presented in the purified proteasome, and the interaction of DsKCBP-Hsp90 was inhibited upon Hsp90 inhibitor geldanamycin treatment. The level of DsKCBP proteins was diminished remarkably indicating that the disassociation of DsKCBP from Hsp90 accelerated the degradation of the former. Furthermore, immunofluorescence results showed that the localization of DsKCBP at basal body and flagella was disappeared by Hsp90 inhibition. The increased mRNA level of DsKCBP during flagellar assembly was not obvious by geldanamycin treatment. These data provided evidence that Hsp90 protected DsKCBP from degradation by proteasome and was involved in the role of DsKCBP in flagellar assembly.
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Affiliation(s)
- Ke Shi
- Department of Biochemistry and Molecular Biology, Henan Medical College, Zhengzhou, Henan, China.
- Laboratory for Cell Biology, the First Affiliated Hospital, Zhengzhou University, Zhengzhou, Henan, China.
| | - Liang Yang
- Department of Microbiology and Immunology and Medicine, Henan Medical College, Zhengzhou, Henan, China
| | - Xiuhong Du
- Department of Biochemistry and Molecular Biology, Henan Medical College, Zhengzhou, Henan, China
| | - Dan Guo
- Department of Biochemistry and Molecular Biology, Henan Medical College, Zhengzhou, Henan, China
| | - Lexun Xue
- Laboratory for Cell Biology, the First Affiliated Hospital, Zhengzhou University, Zhengzhou, Henan, China.
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16
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Lamm N, Rogers S, Cesare AJ. Chromatin mobility and relocation in DNA repair. Trends Cell Biol 2021; 31:843-855. [PMID: 34183232 DOI: 10.1016/j.tcb.2021.06.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 06/02/2021] [Accepted: 06/03/2021] [Indexed: 01/17/2023]
Abstract
The nucleus is a dynamic environment containing chromatin, membraneless organelles, and specialized molecular structures at the nuclear membrane. Within the spectrum of DNA repair activities are observations of increased mobility of damaged chromatin and the displacement of DNA lesions to specific nuclear environments. Here, we focus on the role that nuclear-specific filamentous actin plays in mobilizing damaged chromatin in response to DNA double-strand breaks and replication stress. We also examine nuclear pore complexes and promyelocytic leukemia-nuclear bodies as specialized platforms for homology-directed repair. The literature suggests an emerging model where specific types of DNA lesions are subjected to nuclear-derived forces that mobilize damaged chromatin and promote interaction with repair hubs to facilitate specialized repair reactions.
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Affiliation(s)
- Noa Lamm
- Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, 2145, Australia
| | - Samuel Rogers
- Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, 2145, Australia
| | - Anthony J Cesare
- Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, 2145, Australia.
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17
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Sumner MC, Torrisi SB, Brickner DG, Brickner JH. Random sub-diffusion and capture of genes by the nuclear pore reduces dynamics and coordinates inter-chromosomal movement. eLife 2021; 10:66238. [PMID: 34002694 PMCID: PMC8195609 DOI: 10.7554/elife.66238] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 05/17/2021] [Indexed: 11/13/2022] Open
Abstract
Hundreds of genes interact with the yeast nuclear pore complex (NPC), localizing at the nuclear periphery and clustering with co-regulated genes. Dynamic tracking of peripheral genes shows that they cycle on and off the NPC and that interaction with the NPC slows their sub-diffusive movement. Furthermore, NPC-dependent inter-chromosomal clustering leads to coordinated movement of pairs of loci separated by hundreds of nanometers. We developed fractional Brownian motion simulations for chromosomal loci in the nucleoplasm and interacting with NPCs. These simulations predict the rate and nature of random sub-diffusion during repositioning from nucleoplasm to periphery and match measurements from two different experimental models, arguing that recruitment to the nuclear periphery is due to random sub-diffusion and transient capture by NPCs. Finally, the simulations do not lead to inter-chromosomal clustering or coordinated movement, suggesting that interaction with the NPC is necessary, but not sufficient, to cause clustering.
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Affiliation(s)
- Michael Chas Sumner
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
| | - Steven B Torrisi
- Department of Physics, Harvard University, Cambridge, United States
| | - Donna G Brickner
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
| | - Jason H Brickner
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
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18
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Casas-Tintó S, Ferrús A. The haplolethality paradox of the wupA gene in Drosophila. PLoS Genet 2021; 17:e1009108. [PMID: 33739971 PMCID: PMC8011728 DOI: 10.1371/journal.pgen.1009108] [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: 09/07/2020] [Revised: 03/31/2021] [Accepted: 02/15/2021] [Indexed: 11/18/2022] Open
Abstract
Haplolethals (HL) are regions of diploid genomes that in one dose are fatal for the organism. Their biological meaning is obscure because heterozygous loss-of-function mutations result in dominant lethality (DL) and, consequently, should be under strong negative selection. We report an in depth study of the HL associated to the gene wings up A (wupA). It encodes 13 transcripts (A-M) that yield 11 protein isoforms (A-K) of Troponin I (TnI). They are functionally diverse in their control of muscle contraction, cell polarity and cell proliferation. Isoform K transfers to the nucleus where it increases transcription of the cell proliferation related genes CDK2, CDK4, Rap and Rab5. The nuclear translocation of isoform K is prevented by the co-expression of A or B isoforms, which illustrates isoform interactions. The corresponding DL mutations are, either DNA rearrangements clustered towards the gene 3’ end, thus affecting the genomic organization of all transcripts, or CRISPR-induced mutations in one of the two ATG sites which eliminate a subset of wupA products. The joint elimination of isoforms C, F, G and H, however, do not cause DL phenotypes. Genetically driven expression of single isoforms rescue neither DL nor any of the mutants known in the gene, suggesting that normal function requires properly regulated expression of specific combinations, rather than single, TnI isoforms. We conclude that the wupA associated HL results from the combined haploinsufficiency of a large set of TnI isoforms. The qualitative and quantitative normal expression of which, requires the chromosomal integrity of the wupA genomic region. Since all fly TnI isoforms are encoded in the same gene, its HL condition becomes unavoidable. These wupA features are comparable to those of dpp, the only other HL studied to some extent, and reveal a scenario of strict dosage dependence with implications for gene expression regulation and splitting. Most species contain two copies of their genetic endowment, each received from each progenitor. If one of the duplicated genes is non-functional, the remaining copy may supply enough product as to cover the requirements for normal function or, alternatively, may reflect the insufficiency through a visible phenotype. In rare occasions, however, having one copy is so deleterious that causes lethality. These so called “haplolethal regions”, exist across species and represent an evolutionary paradox since they should have been subject to intense negative selection. The inherent difficulties to study haplolethals have precluded their study so far. Here, we analyzed the case of one of the five haplolethal regions of Drosophila, the one associated to the Troponin I encoding gene wupA, by measuring the transcriptional effects of mutations and chromosomal rearrangements affecting this gene. The data show that this haplolethality results from the combined insufficiency of a large number of Troponin I isoforms, which are functionally specialized, show interference and require the integrity of the native chromatin structure for their quantitatively regulated expression. These features unveil novel aspects of gene expression and, possibly, on evolutionary gene splitting. Also, haplolethals underscore the biological significance of protein dosage, in particular for functionally related products.
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Affiliation(s)
- Sergio Casas-Tintó
- Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Alberto Ferrús
- Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- * E-mail:
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19
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Ulferts S, Prajapati B, Grosse R, Vartiainen MK. Emerging Properties and Functions of Actin and Actin Filaments Inside the Nucleus. Cold Spring Harb Perspect Biol 2021; 13:cshperspect.a040121. [PMID: 33288541 PMCID: PMC7919393 DOI: 10.1101/cshperspect.a040121] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent years have provided considerable insights into the dynamic nature of the cell nucleus, which is constantly reorganizing its genome, controlling its size and shape, as well as spatiotemporally orchestrating chromatin remodeling and transcription. Remarkably, it has become clear that the ancient and highly conserved cytoskeletal protein actin plays a crucial part in these processes. However, the underlying mechanisms, regulations, and properties of actin functions inside the nucleus are still not well understood. Here we summarize the diverse and distinct roles of monomeric and filamentous actin as well as the emerging roles for actin dynamics inside the nuclear compartment for genome organization and nuclear architecture.
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Affiliation(s)
- Svenja Ulferts
- Institute for Clinical and Experimental Pharmacology and Toxicology I, University of Freiburg, 79104 Freiburg, Germany
| | - Bina Prajapati
- Institute of Biotechnology, Helsinki Institute for Life Science, University of Helsinki, 00014 Helsinki, Finland
| | - Robert Grosse
- Institute for Clinical and Experimental Pharmacology and Toxicology I, University of Freiburg, 79104 Freiburg, Germany,Centre for Integrative Biological Signalling Studies (CIBSS), 79104 Freiburg, Germany
| | - Maria K. Vartiainen
- Institute of Biotechnology, Helsinki Institute for Life Science, University of Helsinki, 00014 Helsinki, Finland
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20
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Peng AYT, Kolhe JA, Behrens LD, Freeman BC. Genome organization: Tag it, move it, place it. Curr Opin Cell Biol 2020; 68:90-97. [PMID: 33166737 DOI: 10.1016/j.ceb.2020.10.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 09/28/2020] [Accepted: 10/08/2020] [Indexed: 12/14/2022]
Abstract
Chromosomes are selectively organized within the nuclei of interphase cells reflecting the current fate of each cell and are reorganized in response to various physiological cues to maintain homeostasis. Although substantial progress is being made to establish the various patterns of genome architecture, less is understood on how chromosome folding/positioning is achieved. Here, we discuss recent insights into the cellular mechanisms dictating chromatin movements including the use of epigenetic modifications and allosterically regulated transcription factors, as well as a nucleoskeleton system comprised of actin, myosin, and actin-binding proteins. Together, these nuclear factors help coordinate the positioning of both general and cell-specific genomic architectural features.
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Affiliation(s)
- Audrey Yi Tyan Peng
- University of Illinois, Urbana-Champaign, Department of Cell and Developmental Biology, Urbana, IL, 61801, USA
| | - Janhavi A Kolhe
- University of Illinois, Urbana-Champaign, Department of Cell and Developmental Biology, Urbana, IL, 61801, USA
| | - Lindsey D Behrens
- University of Illinois, Urbana-Champaign, Department of Cell and Developmental Biology, Urbana, IL, 61801, USA
| | - Brian C Freeman
- University of Illinois, Urbana-Champaign, Department of Cell and Developmental Biology, Urbana, IL, 61801, USA.
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21
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Misteli T. The Self-Organizing Genome: Principles of Genome Architecture and Function. Cell 2020; 183:28-45. [PMID: 32976797 PMCID: PMC7541718 DOI: 10.1016/j.cell.2020.09.014] [Citation(s) in RCA: 287] [Impact Index Per Article: 71.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 08/03/2020] [Accepted: 09/02/2020] [Indexed: 01/17/2023]
Abstract
Genomes have complex three-dimensional architectures. The recent convergence of genetic, biochemical, biophysical, and cell biological methods has uncovered several fundamental principles of genome organization. They highlight that genome function is a major driver of genome architecture and that structural features of chromatin act as modulators, rather than binary determinants, of genome activity. The interplay of these principles in the context of self-organization can account for the emergence of structural chromatin features, the diversity and single-cell heterogeneity of nuclear architecture in cell types and tissues, and explains evolutionarily conserved functional features of genomes, including plasticity and robustness.
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Affiliation(s)
- Tom Misteli
- National Cancer Institute, NIH, Bethesda, MD 20892, USA.
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22
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Capelson M. How Genes Move: Spatial Repositioning of Activated Genes Is Driven by Nuclear Actin-Based Pathway. Dev Cell 2020; 52:252-254. [PMID: 32049034 DOI: 10.1016/j.devcel.2020.01.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Spatial repositioning of genes in nuclear space has been extensively linked to regulation of gene expression, but the mechanisms behind this directed movement have remained uncertain. In this issue of Developmental Cell, Wang et al. (2020) describe a nuclear actin-myosin-based pathway driving the movement of activated genes to the nuclear periphery.
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Affiliation(s)
- Maya Capelson
- Department of Cell and Developmental Biology, Penn Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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23
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Backe SJ, Sager RA, Woodford MR, Makedon AM, Mollapour M. Post-translational modifications of Hsp90 and translating the chaperone code. J Biol Chem 2020; 295:11099-11117. [PMID: 32527727 DOI: 10.1074/jbc.rev120.011833] [Citation(s) in RCA: 102] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 06/11/2020] [Indexed: 12/12/2022] Open
Abstract
Cells have a remarkable ability to synthesize large amounts of protein in a very short period of time. Under these conditions, many hydrophobic surfaces on proteins may be transiently exposed, and the likelihood of deleterious interactions is quite high. To counter this threat to cell viability, molecular chaperones have evolved to help nascent polypeptides fold correctly and multimeric protein complexes assemble productively, while minimizing the danger of protein aggregation. Heat shock protein 90 (Hsp90) is an evolutionarily conserved molecular chaperone that is involved in the stability and activation of at least 300 proteins, also known as clients, under normal cellular conditions. The Hsp90 clients participate in the full breadth of cellular processes, including cell growth and cell cycle control, signal transduction, DNA repair, transcription, and many others. Hsp90 chaperone function is coupled to its ability to bind and hydrolyze ATP, which is tightly regulated both by co-chaperone proteins and post-translational modifications (PTMs). Many reported PTMs of Hsp90 alter chaperone function and consequently affect myriad cellular processes. Here, we review the contributions of PTMs, such as phosphorylation, acetylation, SUMOylation, methylation, O-GlcNAcylation, ubiquitination, and others, toward regulation of Hsp90 function. We also discuss how the Hsp90 modification state affects cellular sensitivity to Hsp90-targeted therapeutics that specifically bind and inhibit its chaperone activity. The ultimate challenge is to decipher the comprehensive and combinatorial array of PTMs that modulate Hsp90 chaperone function, a phenomenon termed the "chaperone code."
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Affiliation(s)
- Sarah J Backe
- Department of Urology, SUNY Upstate Medical University, Syracuse, New York, USA.,Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.,Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Rebecca A Sager
- Department of Urology, SUNY Upstate Medical University, Syracuse, New York, USA.,Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.,Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, New York, USA.,College of Medicine, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Mark R Woodford
- Department of Urology, SUNY Upstate Medical University, Syracuse, New York, USA.,Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.,Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Alan M Makedon
- Department of Urology, SUNY Upstate Medical University, Syracuse, New York, USA.,Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Mehdi Mollapour
- Department of Urology, SUNY Upstate Medical University, Syracuse, New York, USA .,Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.,Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, New York, USA
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24
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Tortora MMC, Salari H, Jost D. Chromosome dynamics during interphase: a biophysical perspective. Curr Opin Genet Dev 2020; 61:37-43. [DOI: 10.1016/j.gde.2020.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 02/24/2020] [Accepted: 03/02/2020] [Indexed: 12/29/2022]
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25
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Job Opening for Nucleosome Mechanic: Flexibility Required. Cells 2020; 9:cells9030580. [PMID: 32121488 PMCID: PMC7140402 DOI: 10.3390/cells9030580] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 02/25/2020] [Accepted: 02/26/2020] [Indexed: 12/21/2022] Open
Abstract
The nucleus has been studied for well over 100 years, and chromatin has been the intense focus of experiments for decades. In this review, we focus on an understudied aspect of chromatin biology, namely the chromatin fiber polymer’s mechanical properties. In recent years, innovative work deploying interdisciplinary approaches including computational modeling, in vitro manipulations of purified and native chromatin have resulted in deep mechanistic insights into how the mechanics of chromatin might contribute to its function. The picture that emerges is one of a nucleus that is shaped as much by external forces pressing down upon it, as internal forces pushing outwards from the chromatin. These properties may have evolved to afford the cell a dynamic and reversible force-induced communication highway which allows rapid coordination between external cues and internal genomic function.
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26
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Venit T, Mahmood SR, Endara-Coll M, Percipalle P. Nuclear actin and myosin in chromatin regulation and maintenance of genome integrity. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2020; 355:67-108. [DOI: 10.1016/bs.ircmb.2020.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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