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Abstract
Actin is a highly conserved protein in mammals. The actin dynamics is regulated by actin-binding proteins and actin-related proteins. Nuclear actin and these regulatory proteins participate in multiple nuclear processes, including chromosome architecture organization, chromatin remodeling, transcription machinery regulation, and DNA repair. It is well known that the dysfunctions of these processes contribute to the development of cancer. Moreover, emerging evidence has shown that the deregulated actin dynamics is also related to cancer. This chapter discusses how the deregulation of nuclear actin dynamics contributes to tumorigenesis via such various nuclear events.
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Affiliation(s)
- Yuanjian Huang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Department of General Surgery, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
| | - Shengzhe Zhang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Jae-Il Park
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
- Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center and Health Science Center, Houston, TX, USA.
- Program in Genetics and Epigenetics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
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52
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Mahmood SR, El Said NH, Percipalle P. The Role of Nuclear Actin in Genome Organization and Gene Expression Regulation During Differentiation. Results Probl Cell Differ 2022; 70:607-624. [PMID: 36348124 DOI: 10.1007/978-3-031-06573-6_22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
In the cell nucleus, actin participates in numerous essential processes. Actin is involved in chromatin as part of specific ATP-dependent chromatin remodeling complexes and associates with the RNA polymerase machinery to regulate transcription at multiple levels. Emerging evidence has also shown that the nuclear actin pool controls the architecture of the mammalian genome playing an important role in its hierarchical organization into transcriptionally active and repressed compartments, contributing to the clustering of RNA polymerase II into transcriptional hubs. Here, we review the most recent literature and discuss how actin involvement in genome organization impacts the regulation of gene programs that are activated or repressed during differentiation and development. As in the cytoplasm, we propose that nuclear actin is involved in key nuclear tasks in complex with different types of actin-binding proteins that regulate actin function and bridge interactions between actin and various nuclear components.
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Affiliation(s)
- Syed Raza Mahmood
- Center for Genomics and Systems Biology, New York University Abu Dhabi (NYUAD), Abu Dhabi, United Arab Emirates
- Department of Biology, New York University, New York, NY, USA
| | - Nadine Hosny El Said
- Program in Biology, Division of Science and Mathematics, New York University Abu Dhabi (NYUAD), Abu Dhabi, United Arab Emirates
| | - Piergiorgio Percipalle
- Center for Genomics and Systems Biology, New York University Abu Dhabi (NYUAD), Abu Dhabi, United Arab Emirates.
- Department of Biology, New York University, New York, NY, USA.
- Program in Biology, Division of Science and Mathematics, New York University Abu Dhabi (NYUAD), Abu Dhabi, United Arab Emirates.
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53
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Ishikawa-Ankerhold HC, Kurzbach S, Kinali AS, Müller-Taubenberger A. Formation of Cytoplasmic Actin-Cofilin Rods is Triggered by Metabolic Stress and Changes in Cellular pH. Front Cell Dev Biol 2021; 9:742310. [PMID: 34869330 PMCID: PMC8635511 DOI: 10.3389/fcell.2021.742310] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 10/27/2021] [Indexed: 11/13/2022] Open
Abstract
Actin dynamics plays a crucial role in regulating essential cell functions and thereby is largely responsible to a considerable extent for cellular energy consumption. Certain pathological conditions in humans, like neurological disorders such as Alzheimer’s disease or amyotrophic lateral sclerosis (ALS) as well as variants of nemaline myopathy are associated with cytoskeletal abnormalities, so-called actin-cofilin rods. Actin-cofilin rods are aggregates consisting mainly of actin and cofilin, which are formed as a result of cellular stress and thereby help to ensure the survival of cells under unfavorable conditions. We have used Dictyostelium discoideum, an established model system for cytoskeletal research to study formation and principles of cytoplasmic actin rod assembly in response to energy depletion. Experimentally, depletion of ATP was provoked by addition of either sodium azide, dinitrophenol, or 2-deoxy-glucose, and the formation of rod assembly was recorded by live-cell imaging. Furthermore, we show that hyperosmotic shock induces actin-cofilin rods, and that a drop in the intracellular pH accompanies this condition. Our data reveal that acidification of the cytoplasm can induce the formation of actin-cofilin rods to varying degrees and suggest that a local reduction in cellular pH may be a cause for the formation of cytoplasmic rods. We hypothesize that local phase separation mechanistically triggers the assembly of actin-cofilin rods and thereby influences the material properties of actin structures.
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Affiliation(s)
- Hellen C Ishikawa-Ankerhold
- Department of Internal Medicine I, University Hospital, LMU Munich, Munich, Germany.,Walter Brendel Centre of Experimental Medicine, University Hospital, LMU Munich, Munich, Germany
| | - Sophie Kurzbach
- Department of Cell Biology (Anatomy III), Biomedical Center (BMC), LMU Munich, Munich, Germany
| | - Arzu S Kinali
- Walter Brendel Centre of Experimental Medicine, University Hospital, LMU Munich, Munich, Germany
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54
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Ortega P, Gómez-González B, Aguilera A. Heterogeneity of DNA damage incidence and repair in different chromatin contexts. DNA Repair (Amst) 2021; 107:103210. [PMID: 34416542 DOI: 10.1016/j.dnarep.2021.103210] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/02/2021] [Accepted: 08/11/2021] [Indexed: 11/18/2022]
Abstract
It has been long known that some regions of the genome are more susceptible to damage and mutagenicity than others. Recent advances have determined a critical role of chromatin both in the incidence of damage and in its repair. Thus, chromatin arises as a guardian of the stability of the genome, which is altered in cancer cells. In this review, we focus into the mechanisms by which chromatin influences the occurrence and repair of the most cytotoxic DNA lesions, double-strand breaks, in particular at actively transcribed chromatin or related to DNA replication.
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Affiliation(s)
- Pedro Ortega
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain; Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Belén Gómez-González
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain; Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain.
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain; Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
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55
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Merigliano C, Chiolo I. Multi-scale dynamics of heterochromatin repair. Curr Opin Genet Dev 2021; 71:206-215. [PMID: 34717276 DOI: 10.1016/j.gde.2021.09.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 09/16/2021] [Accepted: 09/27/2021] [Indexed: 10/24/2022]
Abstract
Studies across different organisms show that nuclear architecture and dynamics play central roles in different aspects of homologous recombination (HR) repair. Here we review the most recent discoveries in this field, ranging from directed motions mediating relocalization pathways, to global chromatin mobilization, local DNA looping, and changes in repair focus properties associated with clustering and phase separation. We discuss how these dynamics work in different contexts, including molecular mechanisms and regulatory pathways involved. We specifically highlight how they function in pericentromeric heterochromatin, which presents a unique environment for HR repair given the abundance of repeated DNA sequences prone to aberrant recombination, the 'silent' chromatin state, and the phase separation characterizing this domain.
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Affiliation(s)
- Chiara Merigliano
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA 90089, USA
| | - Irene Chiolo
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA 90089, USA.
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56
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The Sound of Silence: How Silenced Chromatin Orchestrates the Repair of Double-Strand Breaks. Genes (Basel) 2021; 12:genes12091415. [PMID: 34573397 PMCID: PMC8467445 DOI: 10.3390/genes12091415] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/07/2021] [Accepted: 09/13/2021] [Indexed: 12/29/2022] Open
Abstract
The eukaryotic nucleus is continuously being exposed to endogenous and exogenous sources that cause DNA breaks, whose faithful repair requires the activity of dedicated nuclear machineries. DNA is packaged into a variety of chromatin domains, each characterized by specific molecular properties that regulate gene expression and help maintain nuclear structure. These different chromatin environments each demand a tailored response to DNA damage. Silenced chromatin domains in particular present a major challenge to the cell’s DNA repair machinery due to their specific biophysical properties and distinct, often repetitive, DNA content. To this end, we here discuss the interplay between silenced chromatin domains and DNA damage repair, specifically double-strand breaks, and how these processes help maintain genome stability.
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57
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Hurst V, Challa K, Shimada K, Gasser SM. Cytoskeleton integrity influences XRCC1 and PCNA dynamics at DNA damage. Mol Biol Cell 2021; 32:br6. [PMID: 34379448 PMCID: PMC8684753 DOI: 10.1091/mbc.e20-10-0680] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
On induction of DNA damage with 405-nm laser light, proteins involved in base excision repair (BER) are recruited to DNA lesions. We find that the dynamics of factors typical of either short-patch (XRCC1) or long-patch (PCNA) BER are altered by chemicals that perturb actin or tubulin polymerization in human cells. Whereas the destabilization of actin filaments by latrunculin B, cytochalasin B, or Jasplakinolide decreases BER factor accumulation at laser-induced damage, inhibition of tubulin polymerization by nocodazole increases it. We detect no recruitment of actin to sites of laser-induced DNA damage, yet the depolymerization of cytoplasmic actin filaments elevates both actin and tubulin signals in the nucleus. While published evidence suggested a positive role for F-actin in double-strand break repair in mammals, the enrichment of actin in budding yeast nuclei interferes with BER, augmenting sensitivity to Zeocin. Our quantitative imaging results suggest that the depolymerization of cytoplasmic actin may compromise BER efficiency in mammals not only due to elevated levels of nuclear actin but also of tubulin, linking cytoskeletal integrity to BER.
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Affiliation(s)
- Verena Hurst
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland.,Faculty of Natural Sciences, University of Basel, Klingelbergstrasse 90, CH-4056 Basel, Switzerland
| | - Kiran Challa
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
| | - Kenji Shimada
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
| | - Susan M Gasser
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland.,Faculty of Natural Sciences, University of Basel, Klingelbergstrasse 90, CH-4056 Basel, Switzerland
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58
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Sharma PK, Kalia I, Kaushik V, Brünnert D, Quadiri A, Kashif M, Chahar KR, Agrawal A, Singh AP, Goyal P. STK35L1 regulates host cell cycle-related genes and is essential for Plasmodium infection during the liver stage of malaria. Exp Cell Res 2021; 406:112764. [PMID: 34358525 DOI: 10.1016/j.yexcr.2021.112764] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 07/30/2021] [Accepted: 07/31/2021] [Indexed: 11/28/2022]
Abstract
Protein kinases of both the parasite and the host are crucial in parasite invasion and survival and might act as drug targets against drug-resistant malaria. STK35L1 was among the top five hits in kinome-wide screening, suggesting its role in malaria's liver stage. However, the role of host STK35L1 in malaria remains elusive. In this study, we found that STK35L1 was highly upregulated during the infection of Plasmodium berghei (P. berghei) in HepG2 cells and mice liver, and knockdown of STK35L1 remarkably suppressed the sporozoites' infection in HepG2 cells. We showed that STAT3 is upregulated and phosphorylated during P. berghei sporozoites' infection, and STAT3 activation is required for both the upregulation of STK35L1 and STAT3. Furthermore, we found that ten cell cycle genes were upregulated in the sporozoite-infected hepatocytes. Knockdown of STK35L1 inhibited the basal expression of these genes except CDKN3 and GTSE1 in HepG2 cells. Thus, we identified STK35L1 as a host kinase that plays an obligatory role in malaria's liver stage and propose that it may serve as a potential drug target against drug-resistant malaria.
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Affiliation(s)
- Phulwanti Kumari Sharma
- Department of Biotechnology, School of Life Sciences, Central University of Rajasthan, Bandarsindri, Kishangarh, Rajasthan, 305 817, India
| | - Inderjeet Kalia
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Vibha Kaushik
- Department of Biotechnology, School of Life Sciences, Central University of Rajasthan, Bandarsindri, Kishangarh, Rajasthan, 305 817, India
| | - Daniela Brünnert
- Experimental Tumor Immunology, Department of Obstetrics and Gynecology, University of Würzburg Medical School, Würzburg, Germany
| | - Afshana Quadiri
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Mohammad Kashif
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Kirti Raj Chahar
- Department of Biotechnology, School of Life Sciences, Central University of Rajasthan, Bandarsindri, Kishangarh, Rajasthan, 305 817, India
| | - Akhil Agrawal
- Department of Microbiology, School of Life Sciences, Central University of Rajasthan, Bandarsindri, Kishangarh, Rajasthan, 305 817, India
| | - Agam Prasad Singh
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India.
| | - Pankaj Goyal
- Department of Biotechnology, School of Life Sciences, Central University of Rajasthan, Bandarsindri, Kishangarh, Rajasthan, 305 817, India.
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59
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Yamazaki S, Ueno Y, Hosoki R, Saito T, Idehara T, Yamaguchi Y, Otani C, Ogawa Y, Harata M, Hoshina H. THz irradiation inhibits cell division by affecting actin dynamics. PLoS One 2021; 16:e0248381. [PMID: 34339441 PMCID: PMC8328307 DOI: 10.1371/journal.pone.0248381] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 07/17/2021] [Indexed: 11/25/2022] Open
Abstract
Biological phenomena induced by terahertz (THz) irradiation are described in recent reports, but underlying mechanisms, structural and dynamical change of specific molecules are still unclear. In this paper, we performed time-lapse morphological analysis of human cells and found that THz irradiation halts cell division at cytokinesis. At the end of cytokinesis, the contractile ring, which consists of filamentous actin (F-actin), needs to disappear; however, it remained for 1 hour under THz irradiation. Induction of the functional structures of F-actin was also observed in interphase cells. Similar phenomena were also observed under chemical treatment (jasplakinolide), indicating that THz irradiation assists actin polymerization. We previously reported that THz irradiation enhances the polymerization of purified actin in vitro; our current work shows that it increases cytoplasmic F-actin in vivo. Thus, we identified one of the key biomechanisms affected by THz waves.
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Affiliation(s)
- Shota Yamazaki
- Terahertz Sensing and Imaging Research Team, RIKEN Center for Advanced Photonics, Sendai, Miyagi, Japan
- * E-mail: (SY); (MH); (HH)
| | - Yuya Ueno
- Laboratory of Molecular Biology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
| | - Ryosuke Hosoki
- Laboratory of Molecular Biology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
| | - Takanori Saito
- Laboratory of Molecular Biology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
| | - Toshitaka Idehara
- Research Center for Development of Far-Infrared Region, University of Fukui (FIR UF), Bunkyo, Fukui, Japan
| | - Yuusuke Yamaguchi
- Research Center for Development of Far-Infrared Region, University of Fukui (FIR UF), Bunkyo, Fukui, Japan
| | - Chiko Otani
- Terahertz Sensing and Imaging Research Team, RIKEN Center for Advanced Photonics, Sendai, Miyagi, Japan
| | - Yuichi Ogawa
- Laboratory of Bio-Sensing Engineering, Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto, Japan
| | - Masahiko Harata
- Laboratory of Molecular Biology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
- * E-mail: (SY); (MH); (HH)
| | - Hiromichi Hoshina
- Terahertz Sensing and Imaging Research Team, RIKEN Center for Advanced Photonics, Sendai, Miyagi, Japan
- * E-mail: (SY); (MH); (HH)
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60
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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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61
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Machida N, Takahashi D, Ueno Y, Nakama Y, Gubeli RJ, Bertoldo D, Harata M. Modulating dynamics and function of nuclear actin with synthetic bicyclic peptides. J Biochem 2021; 169:295-302. [PMID: 33169153 DOI: 10.1093/jb/mvaa130] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 10/26/2020] [Indexed: 12/27/2022] Open
Abstract
Actin exists in monomeric globular (G-) and polymerized filamentous (F-) forms and the dynamics of its polymerization/depolymerization are tightly regulated in both the cytoplasm and the nucleus. Various essential functions of nuclear actin have been identified including regulation of gene expression and involvement in the repair of DNA double-strand breaks (DSB). Small G-actin-binding molecules affect F-actin formation and can be utilized for analysis and manipulation of actin in living cells. However, these G-actin-binding molecules are obtained by extraction from natural sources or through complex chemical synthesis procedures, and therefore, the generation of their derivatives for analytical tools is underdeveloped. In addition, their effects on nuclear actin cannot be separately evaluated from those on cytoplasmic actin. Previously, we have generated synthetic bicyclic peptides, consisting of two macrocyclic rings, which bind to G-actin but not to F-actin. Here, we describe the introduction of these bicyclic peptides into living cells. Furthermore, by conjugation to a nuclear localization signal (NLS), the bicyclic peptides accumulated in the nucleus. The NLS-bicyclic peptides repress the formation of nuclear F-actin, and impair transcriptional regulation and DSB repair. These observations highlight a potential role for NLS-linked bicyclic peptides in the manipulation of dynamics and functions of nuclear actin.
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Affiliation(s)
- Nanako Machida
- Laboratory of Molecular Biology, Division of Life Science, Graduate School of Agricultural Science, Tohoku University, 468-1, Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
| | - Daisuke Takahashi
- Laboratory of Molecular Biology, Division of Life Science, Graduate School of Agricultural Science, Tohoku University, 468-1, Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
| | - Yuya Ueno
- Laboratory of Molecular Biology, Division of Life Science, Graduate School of Agricultural Science, Tohoku University, 468-1, Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
| | - Yoshihiro Nakama
- Laboratory of Molecular Biology, Division of Life Science, Graduate School of Agricultural Science, Tohoku University, 468-1, Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
| | - Raphael J Gubeli
- Institute of Chemical Sciences and Engineering, School of Basic Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Davide Bertoldo
- Institute of Chemical Sciences and Engineering, School of Basic Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Masahiko Harata
- Laboratory of Molecular Biology, Division of Life Science, Graduate School of Agricultural Science, Tohoku University, 468-1, Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
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62
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Vodnala M, Choi EB, Fong YW. Low complexity domains, condensates, and stem cell pluripotency. World J Stem Cells 2021; 13:416-438. [PMID: 34136073 PMCID: PMC8176841 DOI: 10.4252/wjsc.v13.i5.416] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 04/20/2021] [Accepted: 04/28/2021] [Indexed: 02/06/2023] Open
Abstract
Biological reactions require self-assembly of factors in the complex cellular milieu. Recent evidence indicates that intrinsically disordered, low-complexity sequence domains (LCDs) found in regulatory factors mediate diverse cellular processes from gene expression to DNA repair to signal transduction, by enriching specific biomolecules in membraneless compartments or hubs that may undergo liquid-liquid phase separation (LLPS). In this review, we discuss how embryonic stem cells take advantage of LCD-driven interactions to promote cell-specific transcription, DNA damage response, and DNA repair. We propose that LCD-mediated interactions play key roles in stem cell maintenance and safeguarding genome integrity.
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Affiliation(s)
- Munender Vodnala
- Department of Medicine, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Eun-Bee Choi
- Department of Medicine, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Yick W Fong
- Department of Medicine, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, United States
- Harvard Stem Cell Institute, Cambridge, MA 02138, United States.
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63
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Qiu GH, Zheng X, Fu M, Huang C, Yang X. The decreased exclusion of nuclear eccDNA: From molecular and subcellular levels to human aging and age-related diseases. Ageing Res Rev 2021; 67:101306. [PMID: 33610814 DOI: 10.1016/j.arr.2021.101306] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 02/15/2021] [Accepted: 02/16/2021] [Indexed: 12/11/2022]
Abstract
Extrachromosomal circular DNA (eccDNA) accumulates within the nucleus of eukaryotic cells during physiological aging and in age-related diseases (ARDs) and the accumulation could be caused by the declined exclusion of nuclear eccDNA in these states. This review focuses on the formation of eccDNA and the roles of some main factors, such as nuclear pore complexes (NPCs), nucleoplasmic reticulum (NR), and nuclear actin, in eccDNA exclusion. eccDNAs are mostly formed from non-coding DNA during DNA damage repair. They move to NPCs along nuclear actin and are excluded out of the nucleus through functional NPCs in young and healthy cells. However, it has been demonstrated that defective NPCs, abnormal NPC components and nuclear actin rods are increased in aged cells, various cancers and certain other ARDs such as cardiovascular diseases, premature aging, neurodegenerative diseases and myopathies. Therefore, mainly resulting from the increase of dysfunctional NPCs, the exclusion of nuclear eccDNAs may be reduced and eccDNAs thus accumulate within the nucleus in aging and the aforementioned ARDs. In addition, the protective function of non-coding DNA in tumorigenesis is further discussed.
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Affiliation(s)
- Guo-Hua Qiu
- Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province Universities, College of Life Sciences, Longyan University, Longyan 364012, People's Republic of China.
| | - Xintian Zheng
- Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province Universities, College of Life Sciences, Longyan University, Longyan 364012, People's Republic of China
| | - Mingjun Fu
- Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province Universities, College of Life Sciences, Longyan University, Longyan 364012, People's Republic of China
| | - Cuiqin Huang
- Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province Universities, College of Life Sciences, Longyan University, Longyan 364012, People's Republic of China
| | - Xiaoyan Yang
- Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province Universities, College of Life Sciences, Longyan University, Longyan 364012, People's Republic of China
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64
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New Insights into Cellular Functions of Nuclear Actin. BIOLOGY 2021; 10:biology10040304. [PMID: 33916969 PMCID: PMC8067577 DOI: 10.3390/biology10040304] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 03/30/2021] [Accepted: 04/01/2021] [Indexed: 12/12/2022]
Abstract
Simple Summary It is well known that actin forms a cytoplasmic network of microfilaments, the part of the cytoskeleton, in the cytoplasm of eukaryotic cells. The presence of nuclear actin was elusive for a very long time. Now, there is a very strong evidence that actin plays many important roles in the nucleus. Here, we discuss the recently discovered functions of the nuclear actin pool. Actin does not have nuclear localization signal (NLS), so its import to the nucleus is facilitated by the NLS-containing proteins. Nuclear actin plays a role in the maintenance of the nuclear structure and the nuclear envelope breakdown. It is also involved in chromatin remodeling, and chromatin and nucleosome movement necessary for DNA recombination, repair, and the initiation of transcription. It also binds RNA polymerases, promoting transcription. Because of the multifaceted role of nuclear actin, the future challenge will be to further define its functions in various cellular processes and diseases. Abstract Actin is one of the most abundant proteins in eukaryotic cells. There are different pools of nuclear actin often undetectable by conventional staining and commercial antibodies used to identify cytoplasmic actin. With the development of more sophisticated imaging and analytical techniques, it became clear that nuclear actin plays a crucial role in shaping the chromatin, genomic, and epigenetic landscape, transcriptional regulation, and DNA repair. This multifaceted role of nuclear actin is not only important for the function of the individual cell but also for the establishment of cell fate, and tissue and organ differentiation during development. Moreover, the changes in the nuclear, chromatin, and genomic architecture are preamble to various diseases. Here, we discuss some of the newly described functions of nuclear actin.
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Nair RR, Hsu J, Jacob JT, Pineda CM, Hobbs RP, Coulombe PA. A role for keratin 17 during DNA damage response and tumor initiation. Proc Natl Acad Sci U S A 2021; 118:e2020150118. [PMID: 33762306 PMCID: PMC8020757 DOI: 10.1073/pnas.2020150118] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
High levels of the intermediate filament protein keratin 17 (K17) are associated with poor prognoses for several human carcinomas. Studies in mouse models have shown that K17 expression is positively associated with growth, survival, and inflammation in skin and that lack of K17 delays onset of tumorigenesis. K17 occurs in the nucleus of human and mouse tumor keratinocytes where it impacts chromatin architecture, gene expression, and cell proliferation. We report here that K17 is induced following DNA damage and promotes keratinocyte survival. The presence of nuclear K17 is required at an early stage of the double-stranded break (DSB) arm of the DNA damage and repair (DDR) cascade, consistent with its ability to associate with key DDR effectors, including γ-H2A.X, 53BP1, and DNA-PKcs. Mice lacking K17 or with attenuated K17 nuclear import showed curtailed initiation in a two-step skin carcinogenesis paradigm. The impact of nuclear-localized K17 on DDR and cell survival provides a basis for the link between K17 induction and poor clinical outcomes for several human carcinomas.
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MESH Headings
- 9,10-Dimethyl-1,2-benzanthracene/administration & dosage
- 9,10-Dimethyl-1,2-benzanthracene/toxicity
- Active Transport, Cell Nucleus
- Animals
- Carcinogenesis/chemically induced
- Carcinogenesis/genetics
- Carcinogenesis/pathology
- Carcinoma/chemically induced
- Carcinoma/genetics
- Carcinoma/pathology
- Cell Nucleus/metabolism
- Cell Survival/genetics
- DNA Breaks, Double-Stranded/drug effects
- DNA Repair
- Female
- Gene Knockout Techniques
- HeLa Cells
- Humans
- Intravital Microscopy
- Keratin-17/genetics
- Keratin-17/metabolism
- Keratinocytes
- Keratins/genetics
- Keratins/metabolism
- Male
- Mice, Knockout
- Neoplasms, Experimental/chemically induced
- Neoplasms, Experimental/genetics
- Neoplasms, Experimental/pathology
- Time-Lapse Imaging
- Mice
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Affiliation(s)
- Raji R Nair
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Joshua Hsu
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205
| | - Justin T Jacob
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205
| | - Christopher M Pineda
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Ryan P Hobbs
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205;
| | - Pierre A Coulombe
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109;
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI 48109
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Morrish R, Yim KHW, Pagliara S, Palombo F, Chahwan R, Stone N. Single Cell Label-Free Probing of Chromatin Dynamics During B Lymphocyte Maturation. Front Cell Dev Biol 2021; 9:646616. [PMID: 33842468 PMCID: PMC8033168 DOI: 10.3389/fcell.2021.646616] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Accepted: 03/08/2021] [Indexed: 01/11/2023] Open
Abstract
Large-scale intracellular signaling during developmental growth or in response to environmental alterations are largely orchestrated by chromatin within the cell nuclei. Chemical and conformational modifications of the chromatin architecture are critical steps in the regulation of differential gene expression and ultimately cell fate determination. Therefore, establishing chemical properties of the nucleus could provide key markers for phenotypic characterization of cellular processes on a scale of individual cells. Raman microscopy is a sensitive technique that is capable of probing single cell chemical composition—and sub-cellular regions—in a label-free optical manner. As such, it has great potential in both clinical and basic research. However, perceived limitations of Raman spectroscopy such as low signal intensity and the difficulty in linking alterations in vibrational signals directly with ensuing biological effects have hampered advances in the field. Here we use immune B lymphocyte development as a model to assess chromatin and transcriptional changes using confocal Raman microscopy in combination with microfluidic devices and correlative transcriptomics, thereby linking changes in chemical and structural properties to biological outcomes. Live B lymphocytes were assessed before and after maturation. Multivariate analysis was applied to distinguish cellular components within each cell. The spectral differences between non-activated and activated B lymphocytes were then identified, and their correlation with known intracellular biological changes were assessed in comparison to conventional RNA-seq analysis. Our data shows that spectral analysis provides a powerful tool to study gene activation that can complement conventional molecular biology techniques and opens the way for mapping the dynamics in the biochemical makeup of individual cells.
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Affiliation(s)
- Rikke Morrish
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom.,Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Kevin Ho Wai Yim
- Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland
| | - Stefano Pagliara
- Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Francesca Palombo
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| | - Richard Chahwan
- Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland
| | - Nicholas Stone
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
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dos Santos Á, Toseland CP. Regulation of Nuclear Mechanics and the Impact on DNA Damage. Int J Mol Sci 2021; 22:3178. [PMID: 33804722 PMCID: PMC8003950 DOI: 10.3390/ijms22063178] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 03/15/2021] [Accepted: 03/18/2021] [Indexed: 02/06/2023] Open
Abstract
In eukaryotic cells, the nucleus houses the genomic material of the cell. The physical properties of the nucleus and its ability to sense external mechanical cues are tightly linked to the regulation of cellular events, such as gene expression. Nuclear mechanics and morphology are altered in many diseases such as cancer and premature ageing syndromes. Therefore, it is important to understand how different components contribute to nuclear processes, organisation and mechanics, and how they are misregulated in disease. Although, over the years, studies have focused on the nuclear lamina-a mesh of intermediate filament proteins residing between the chromatin and the nuclear membrane-there is growing evidence that chromatin structure and factors that regulate chromatin organisation are essential contributors to the physical properties of the nucleus. Here, we review the main structural components that contribute to the mechanical properties of the nucleus, with particular emphasis on chromatin structure. We also provide an example of how nuclear stiffness can both impact and be affected by cellular processes such as DNA damage and repair.
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Affiliation(s)
- Ália dos Santos
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
| | - Christopher P. Toseland
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
- Insigneo Institute for in Silico Medicine, University of Sheffield, Sheffield S10 2RX, UK
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68
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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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69
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Chronic exposure of humans to high level natural background radiation leads to robust expression of protective stress response proteins. Sci Rep 2021; 11:1777. [PMID: 33469066 PMCID: PMC7815775 DOI: 10.1038/s41598-020-80405-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 12/21/2020] [Indexed: 12/13/2022] Open
Abstract
Understanding exposures to low doses of ionizing radiation are relevant since most environmental, diagnostic radiology and occupational exposures lie in this region. However, the molecular mechanisms that drive cellular responses at these doses, and the subsequent health outcomes, remain unclear. A local monazite-rich high level natural radiation area (HLNRA) in the state of Kerala on the south-west coast of Indian subcontinent show radiation doses extending from ≤ 1 to ≥ 45 mGy/y and thus, serve as a model resource to understand low dose mechanisms directly on healthy humans. We performed quantitative discovery proteomics based on multiplexed isobaric tags (iTRAQ) coupled with LC–MS/MS on human peripheral blood mononuclear cells from HLNRA individuals. Several proteins involved in diverse biological processes such as DNA repair, RNA processing, chromatin modifications and cytoskeletal organization showed distinct expression in HLNRA individuals, suggestive of both recovery and adaptation to low dose radiation. In protein–protein interaction (PPI) networks, YWHAZ (14-3-3ζ) emerged as the top-most hub protein that may direct phosphorylation driven pro-survival cellular processes against radiation stress. PPI networks also identified an integral role for the cytoskeletal protein ACTB, signaling protein PRKACA; and the molecular chaperone HSPA8. The data will allow better integration of radiation biology and epidemiology for risk assessment [Data are available via ProteomeXchange with identifier PXD022380].
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70
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See C, Arya D, Lin E, Chiolo I. Live Cell Imaging of Nuclear Actin Filaments and Heterochromatic Repair foci in Drosophila and Mouse Cells. Methods Mol Biol 2021; 2153:459-482. [PMID: 32840799 DOI: 10.1007/978-1-0716-0644-5_32] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Pericentromeric heterochromatin is mostly composed of repeated DNA sequences, which are prone to aberrant recombination during double-strand break (DSB) repair. Studies in Drosophila and mouse cells revealed that 'safe' homologous recombination (HR) repair of these sequences relies on the relocalization of repair sites to outside the heterochromatin domain before Rad51 recruitment. Relocalization requires a striking network of nuclear actin filaments (F-actin) and myosins that drive directed motions. Understanding this pathway requires the detection of nuclear actin filaments that are significantly less abundant than those in the cytoplasm, and the imaging and tracking of repair sites for long time periods. Here, we describe an optimized protocol for live cell imaging of nuclear F-actin in Drosophila cells, and for repair focus tracking in mouse cells, including: imaging setup, image processing approaches, and analysis methods. We emphasize approaches that can be applied to identify the most effective fluorescent markers for live cell imaging, strategies to minimize photobleaching and phototoxicity with a DeltaVision deconvolution microscope, and image processing and analysis methods using SoftWoRx and Imaris software. These approaches enable a deeper understanding of the spatial and temporal dynamics of heterochromatin repair and have broad applicability in the fields of nuclear architecture, nuclear dynamics, and DNA repair.
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Affiliation(s)
- Colby See
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA
| | - Deepak Arya
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA
| | - Emily Lin
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA
| | - Irene Chiolo
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA.
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71
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A M, Latario CJ, Pickrell LE, Higgs HN. Lysine acetylation of cytoskeletal proteins: Emergence of an actin code. J Biophys Biochem Cytol 2020; 219:211455. [PMID: 33044556 PMCID: PMC7555357 DOI: 10.1083/jcb.202006151] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/26/2020] [Accepted: 09/02/2020] [Indexed: 02/06/2023] Open
Abstract
Reversible lysine acetylation of nuclear proteins such as histones is a long-established important regulatory mechanism for chromatin remodeling and transcription. In the cytoplasm, acetylation of a number of cytoskeletal proteins, including tubulin, cortactin, and the formin mDia2, regulates both cytoskeletal assembly and stability. More recently, acetylation of actin itself was revealed to regulate cytoplasmic actin polymerization through the formin INF2, with downstream effects on ER-to-mitochondrial calcium transfer, mitochondrial fission, and vesicle transport. This finding raises the possibility that actin acetylation, along with other post-translational modifications to actin, might constitute an "actin code," similar to the "histone code" or "tubulin code," controlling functional shifts to these central cellular proteins. Given the multiple roles of actin in nuclear functions, its modifications might also have important roles in gene expression.
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72
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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: 307] [Impact Index Per Article: 76.8] [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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73
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Krippner S, Winkelmeier J, Knerr J, Brandt DT, Virant D, Schwan C, Endesfelder U, Grosse R. Postmitotic expansion of cell nuclei requires nuclear actin filament bundling by α-actinin 4. EMBO Rep 2020; 21:e50758. [PMID: 32959960 PMCID: PMC7645226 DOI: 10.15252/embr.202050758] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 08/18/2020] [Accepted: 08/20/2020] [Indexed: 12/13/2022] Open
Abstract
The actin cytoskeleton operates in a multitude of cellular processes including cell shape and migration, mechanoregulation, and membrane or organelle dynamics. However, its filamentous properties and functions inside the mammalian cell nucleus are less well explored. We previously described transient actin assembly at mitotic exit that promotes nuclear expansion during chromatin decondensation. Here, we identify non‐muscle α‐actinin 4 (ACTN4) as a critical regulator to facilitate F‐actin reorganization and bundling during postmitotic nuclear expansion. ACTN4 binds to nuclear actin filament structures, and ACTN4 clusters associate with nuclear F‐actin in a highly dynamic fashion. ACTN4 but not ACTN1 is required for proper postmitotic nuclear volume expansion, mediated by its actin‐binding domain. Using super‐resolution imaging to quantify actin filament numbers and widths in individual nuclei, we find that ACTN4 is necessary for postmitotic nuclear actin reorganization and actin filament bundling. Our findings uncover a nuclear cytoskeletal function for ACTN4 to control nuclear size and chromatin organization during mitotic cell division.
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Affiliation(s)
- Sylvia Krippner
- Institute of Pharmacology, University of Freiburg, Freiburg, Germany
| | - Jannik Winkelmeier
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology and LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
| | - Julian Knerr
- Institute of Pharmacology, University of Freiburg, Freiburg, Germany
| | | | - David Virant
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology and LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
| | - Carsten Schwan
- Institute of Pharmacology, University of Freiburg, Freiburg, Germany
| | - Ulrike Endesfelder
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology and LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
| | - Robert Grosse
- Institute of Pharmacology, University of Freiburg, Freiburg, Germany.,Centre for Integrative Biological Signalling Studies, Freiburg, Germany
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Cornelio-Parra DV, Goswami R, Costanzo K, Morales-Sosa P, Mohan RD. Function and regulation of the Spt-Ada-Gcn5-Acetyltransferase (SAGA) deubiquitinase module. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2020; 1864:194630. [PMID: 32911111 DOI: 10.1016/j.bbagrm.2020.194630] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 08/31/2020] [Accepted: 09/01/2020] [Indexed: 12/27/2022]
Abstract
The Spt-Ada-Gcn5 Acetyltransferase (SAGA) chromatin modifying complex is a critical regulator of gene expression and is highly conserved across species. Subunits of SAGA arrange into discrete modules with lysine aceyltransferase and deubiquitinase activities housed separately. Mutation of the SAGA deubiquitinase module can lead to substantial biological misfunction and diseases such as cancer, neurodegeneration, and blindness. Here, we review the structure and functions of the SAGA deubiquitinase module and regulatory mechanisms acting to control these.
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75
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Miné-Hattab J, Chiolo I. Complex Chromatin Motions for DNA Repair. Front Genet 2020; 11:800. [PMID: 33061931 PMCID: PMC7481375 DOI: 10.3389/fgene.2020.00800] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 07/06/2020] [Indexed: 12/26/2022] Open
Abstract
A number of studies across different model systems revealed that chromatin undergoes significant changes in dynamics in response to DNA damage. These include local motion changes at damage sites, increased nuclear exploration of both damaged and undamaged loci, and directed motions to new nuclear locations associated with certain repair pathways. These studies also revealed the need for new analytical methods to identify directed motions in a context of mixed trajectories, and the importance of investigating nuclear dynamics over different time scales to identify diffusion regimes. Here we provide an overview of the current understanding of this field, including imaging and analytical methods developed to investigate nuclear dynamics in different contexts. These dynamics are essential for genome integrity. Identifying the molecular mechanisms responsible for these movements is key to understanding how their misregulation contributes to cancer and other genome instability disorders.
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Affiliation(s)
- Judith Miné-Hattab
- UMR 3664, CNRS, Institut Curie, PSL Research University, Paris, France
- UMR 3664, CNRS, Institut Curie, Sorbonne Université, Paris, France
| | - Irene Chiolo
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, United States
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Lawrimore CJ, Lawrimore J, He Y, Chavez S, Bloom K. Polymer perspective of genome mobilization. Mutat Res 2020; 821:111706. [PMID: 32516654 DOI: 10.1016/j.mrfmmm.2020.111706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/30/2020] [Accepted: 05/06/2020] [Indexed: 02/07/2023]
Abstract
Chromosome motion is an intrinsic feature of all DNA-based metabolic processes and is a particularly well-documented response to both DNA damage and repair. By using both biological and polymer physics approaches, many of the contributing factors of chromatin motility have been elucidated. These include the intrinsic properties of chromatin, such as stiffness, as well as the loop modulators condensin and cohesin. Various biological factors such as external tethering to nuclear domains, ATP-dependent processes, and nucleofilaments further impact chromatin motion. DNA damaging agents that induce double-stranded breaks also cause increased chromatin motion that is modulated by recruitment of repair and checkpoint proteins. Approaches that integrate biological experimentation in conjunction with models from polymer physics provide mechanistic insights into the role of chromatin dynamics in biological function. In this review we discuss the polymer models and the effects of both DNA damage and repair on chromatin motion as well as mechanisms that may underlie these effects.
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Affiliation(s)
- Colleen J Lawrimore
- Department of Biology, 623 Fordham Hall CB#3280, University of North Carolina, Chapel Hill, NC 27599-3280, United States
| | - Josh Lawrimore
- Department of Biology, 623 Fordham Hall CB#3280, University of North Carolina, Chapel Hill, NC 27599-3280, United States
| | - Yunyan He
- Department of Biology, 623 Fordham Hall CB#3280, University of North Carolina, Chapel Hill, NC 27599-3280, United States
| | - Sergio Chavez
- Department of Biology, 623 Fordham Hall CB#3280, University of North Carolina, Chapel Hill, NC 27599-3280, United States
| | - Kerry Bloom
- Department of Biology, 623 Fordham Hall CB#3280, University of North Carolina, Chapel Hill, NC 27599-3280, United States.
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The Actin-Family Protein Arp4 Is a Novel Suppressor for the Formation and Functions of Nuclear F-Actin. Cells 2020; 9:cells9030758. [PMID: 32204557 PMCID: PMC7140684 DOI: 10.3390/cells9030758] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 03/06/2020] [Accepted: 03/17/2020] [Indexed: 12/20/2022] Open
Abstract
The crosstalk between actin and actin-related proteins (Arps), namely Arp2 and Arp3, plays a central role in facilitating actin polymerization in the cytoplasm and also in the nucleus. Nuclear F-actin is required for transcriptional regulation, double-strand break repair, and nuclear organization. The formation of nuclear F-actin is highly dynamic, suggesting the involvement of positive and negative regulators for nuclear actin polymerization. While actin assembly factors for nuclear F-actin have been recently described, information about inhibitory factors is still limited. The actin-related protein Arp4 which is predominantly localized in the nucleus, has been previously identified as an integral subunit of multiple chromatin modulation complexes, where it forms a heterodimer with monomeric actin. Therefore, we tested whether Arp4 functions as a suppressor of nuclear F-actin formation. The knockdown of Arp4 (Arp4 KD) led to an increase in nuclear F-actin formation in NIH3T3 cells, and purified Arp4 potently inhibited F-actin formation in mouse nuclei transplanted into Xenopus laevis oocytes. Consistently, Arp4 KD facilitated F-actin-inducible gene expression (e.g., OCT4) and DNA damage repair. Our results suggest that Arp4 has a critical role in the formation and functions of nuclear F-actin.
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78
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Oshidari R, Mekhail K, Seeber A. Mobility and Repair of Damaged DNA: Random or Directed? Trends Cell Biol 2020; 30:144-156. [DOI: 10.1016/j.tcb.2019.11.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 11/14/2019] [Accepted: 11/15/2019] [Indexed: 12/24/2022]
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Dialynas G, Delabaere L, Chiolo I. Arp2/3 and Unc45 maintain heterochromatin stability in Drosophila polytene chromosomes. Exp Biol Med (Maywood) 2019; 244:1362-1371. [PMID: 31364400 PMCID: PMC6880141 DOI: 10.1177/1535370219862282] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 06/18/2019] [Indexed: 12/31/2022] Open
Abstract
Repairing DNA double-strand breaks is particularly challenging in pericentromeric heterochromatin, where the abundance of repeated sequences exacerbates the risk of ectopic recombination. In Drosophila Kc cells, accurate homologous recombination repair of heterochromatic double-strand breaks relies on the relocalization of repair sites to the nuclear periphery before Rad51 recruitment and strand invasion. This movement is driven by Arp2/3-dependent nuclear actin filaments and myosins’ ability to walk along them. Conserved mechanisms enable the relocalization of heterochromatic repair sites in mouse cells, and defects in these pathways lead to massive ectopic recombination in heterochromatin and chromosome rearrangements. In Drosophila polytene chromosomes, extensive DNA movement is blocked by a stiff structure of chromosome bundles. Repair pathways in this context are poorly characterized, and whether heterochromatic double-strand breaks relocalize in these cells is unknown. Here, we show that damage in heterochromatin results in relaxation of the heterochromatic chromocenter, consistent with a dynamic response. Arp2/3, the Arp2/3 activator Scar, and the myosin activator Unc45, are required for heterochromatin stability in polytene cells, suggesting that relocalization enables heterochromatin repair also in this tissue. Together, these studies reveal critical roles for actin polymerization and myosin motors in heterochromatin repair and genome stability across different organisms and tissue types.
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Affiliation(s)
- George Dialynas
- Department of Molecular and Computational Biology,
University
of Southern California, Los Angeles
90089, USA
| | - Laetitia Delabaere
- Department of Molecular and Computational Biology,
University
of Southern California, Los Angeles
90089, USA
| | - Irene Chiolo
- Department of Molecular and Computational Biology,
University
of Southern California, Los Angeles
90089, USA
| |
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Abstract
DNA double-strand breaks (DSBs) are particularly challenging to repair in pericentromeric heterochromatin because of the increased risk of aberrant recombination in highly repetitive sequences. Recent studies have identified specialized mechanisms enabling 'safe' homologous recombination (HR) repair in heterochromatin. These include striking nuclear actin filaments (F-actin) and myosins that drive the directed motion of repair sites to the nuclear periphery for 'safe' repair. Here, we summarize our current understanding of the mechanisms involved, and propose how they might operate in the context of a phase-separated environment.
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