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Izquierdo JM. Chromatin-transcription interface: The secret of eternal youth? Aging Cell 2023; 22:e13927. [PMID: 37427688 PMCID: PMC10497848 DOI: 10.1111/acel.13927] [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: 04/27/2023] [Revised: 06/27/2023] [Accepted: 06/29/2023] [Indexed: 07/11/2023] Open
Abstract
In their recent study in Nature, Debès et al. report an increase in RNA polymerase II (Pol II)-mediated transcriptional elongation speed associated with chromatin remodeling during aging in four metazoan animals, two human cell lines, and human blood. Their findings might help us understand why we age through evolutionarily conserved essential processes, and open a window to the molecular and physiological mechanisms influencing healthspan, lifespan and/or longevity.
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Affiliation(s)
- José M. Izquierdo
- Centro de Biología Molecular Severo OchoaConsejo Superior de Investigaciones Científicas‐Universidad Autónoma de Madrid (CSIC‐UAM)MadridSpain
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2
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Debès C, Papadakis A, Grönke S, Karalay Ö, Tain LS, Mizi A, Nakamura S, Hahn O, Weigelt C, Josipovic N, Zirkel A, Brusius I, Sofiadis K, Lamprousi M, Lu YX, Huang W, Esmaillie R, Kubacki T, Späth MR, Schermer B, Benzing T, Müller RU, Antebi A, Partridge L, Papantonis A, Beyer A. Ageing-associated changes in transcriptional elongation influence longevity. Nature 2023; 616:814-821. [PMID: 37046086 PMCID: PMC10132977 DOI: 10.1038/s41586-023-05922-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 03/07/2023] [Indexed: 04/14/2023]
Abstract
Physiological homeostasis becomes compromised during ageing, as a result of impairment of cellular processes, including transcription and RNA splicing1-4. However, the molecular mechanisms leading to the loss of transcriptional fidelity are so far elusive, as are ways of preventing it. Here we profiled and analysed genome-wide, ageing-related changes in transcriptional processes across different organisms: nematodes, fruitflies, mice, rats and humans. The average transcriptional elongation speed (RNA polymerase II speed) increased with age in all five species. Along with these changes in elongation speed, we observed changes in splicing, including a reduction of unspliced transcripts and the formation of more circular RNAs. Two lifespan-extending interventions, dietary restriction and lowered insulin-IGF signalling, both reversed most of these ageing-related changes. Genetic variants in RNA polymerase II that reduced its speed in worms5 and flies6 increased their lifespan. Similarly, reducing the speed of RNA polymerase II by overexpressing histone components, to counter age-associated changes in nucleosome positioning, also extended lifespan in flies and the division potential of human cells. Our findings uncover fundamental molecular mechanisms underlying animal ageing and lifespan-extending interventions, and point to possible preventive measures.
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Affiliation(s)
- Cédric Debès
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Antonios Papadakis
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | | | - Özlem Karalay
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Luke S Tain
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Athanasia Mizi
- Institute of Pathology, University Medical Centre Göttingen, Göttingen, Germany
| | - Shuhei Nakamura
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Oliver Hahn
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Carina Weigelt
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Natasa Josipovic
- Institute of Pathology, University Medical Centre Göttingen, Göttingen, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Anne Zirkel
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Isabell Brusius
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Konstantinos Sofiadis
- Institute of Pathology, University Medical Centre Göttingen, Göttingen, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Mantha Lamprousi
- Institute of Pathology, University Medical Centre Göttingen, Göttingen, Germany
| | - Yu-Xuan Lu
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Wenming Huang
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Reza Esmaillie
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
- Department II of Internal Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Torsten Kubacki
- Department II of Internal Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Martin R Späth
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany
- Department II of Internal Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Bernhard Schermer
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany
- Department II of Internal Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Thomas Benzing
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
- Department II of Internal Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Roman-Ulrich Müller
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany
- Department II of Internal Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Adam Antebi
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany.
- Max Planck Institute for Biology of Ageing, Cologne, Germany.
| | - Linda Partridge
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany.
- Max Planck Institute for Biology of Ageing, Cologne, Germany.
- Department of Genetics, Evolution and Environment, Institute of Healthy Ageing, UCL, London, UK.
| | - Argyris Papantonis
- Institute of Pathology, University Medical Centre Göttingen, Göttingen, Germany.
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany.
| | - Andreas Beyer
- Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, Cologne, Germany.
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany.
- Institute for Genetics, Faculty of Mathematics and Natural Sciences, University of Cologne, Cologne, Germany.
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3
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Abstract
The current model of replication-dependent (RD) histone biosynthesis posits that RD histone gene expression is coupled to DNA replication, occurring only in S phase of the cell cycle once DNA synthesis has begun. However, several key factors in the RD histone biosynthesis pathway are up-regulated by E2F or phosphorylated by CDK2, suggesting these processes may instead begin much earlier, at the point of cell-cycle commitment. In this study, we use both fixed- and live-cell imaging of human cells to address this question, revealing a hybrid model in which RD histone biosynthesis is first initiated in G1, followed by a strong increase in histone production in S phase of the cell cycle. This suggests a mechanism by which cells that have committed to the cell cycle build up an initial small pool of RD histones to be available for the start of DNA replication, before producing most of the necessary histones required in S phase. Thus, a clear distinction exists at completion of mitosis between cells that are born with the intention of proceeding through the cell cycle and replicating their DNA and cells that have chosen to exit the cell cycle and have no immediate need for histone synthesis.
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4
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Yu R, Sun L, Sun Y, Han X, Qin L, Dang W. Cellular response to moderate chromatin architectural defects promotes longevity. SCIENCE ADVANCES 2019; 5:eaav1165. [PMID: 31309140 PMCID: PMC6620092 DOI: 10.1126/sciadv.aav1165] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 05/30/2019] [Indexed: 05/05/2023]
Abstract
Changes in chromatin organization occur during aging. Overexpression of histones partially alleviates these changes and promotes longevity. We report that deletion of the histone H3-H4 minor locus HHT1-HHF1 extended the replicative life span of Saccharomyces cerevisiae. This longevity effect was mediated through TOR signaling inhibition. We present evidence for evolutionarily conserved transcriptional and phenotypic responses to defects in chromatin structure, collectively termed the chromatin architectural defect (CAD) response. Promoters of the CAD response genes were sensitive to histone dosage, with HHT1-HHF1 deletion, nucleosome occupancy was reduced at these promoters allowing transcriptional activation induced by stress response transcription factors Msn2 and Gis1, both of which were required for the life-span extension of hht1-hhf1Δ. Therefore, we conclude that the CAD response induced by moderate chromatin defects promotes longevity.
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Affiliation(s)
- Ruofan Yu
- Department of Molecular and Human Genetics, and Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030, USA
| | - Luyang Sun
- Department of Molecular and Human Genetics, and Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030, USA
| | - Yu Sun
- Department of Molecular and Human Genetics, and Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030, USA
| | - Xin Han
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Lidong Qin
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Weiwei Dang
- Department of Molecular and Human Genetics, and Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030, USA
- Corresponding author.
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5
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Laville V, Le Clerc S, Ezzedine K, Jdid R, Taing L, Labib T, Coulonges C, Ulveling D, Galan P, Guinot C, Fezeu L, Morizot F, Latreille J, Malvy D, Tschachler E, Zagury J. A genome wide association study identifies new genes potentially associated with eyelid sagging. Exp Dermatol 2018; 28:892-898. [DOI: 10.1111/exd.13559] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/04/2018] [Indexed: 01/06/2023]
Affiliation(s)
- Vincent Laville
- Équipe GénomiqueBioinformatique et ApplicationsChaire de BioinformatiqueConservatoire National des Arts et Métiers Paris France
| | - Sigrid Le Clerc
- Équipe GénomiqueBioinformatique et ApplicationsChaire de BioinformatiqueConservatoire National des Arts et Métiers Paris France
| | - Khaled Ezzedine
- Department of DermatologyHenri Mondor Hospital and EA EpiDermE (Epidémiologie en Dermatologie et Evaluation des Thérapeutiques)UPEC‐Université Paris‐Est Créteil France
| | - Randa Jdid
- Department of Skin Knowledge & Women BeautyChanel R & T Pantin France
| | - Lieng Taing
- Équipe GénomiqueBioinformatique et ApplicationsChaire de BioinformatiqueConservatoire National des Arts et Métiers Paris France
| | - Toufik Labib
- Équipe GénomiqueBioinformatique et ApplicationsChaire de BioinformatiqueConservatoire National des Arts et Métiers Paris France
| | - Cédric Coulonges
- Équipe GénomiqueBioinformatique et ApplicationsChaire de BioinformatiqueConservatoire National des Arts et Métiers Paris France
| | - Damien Ulveling
- Équipe GénomiqueBioinformatique et ApplicationsChaire de BioinformatiqueConservatoire National des Arts et Métiers Paris France
| | - Pilar Galan
- Université Paris 13Equipe de Recherche en Epidémiologie Nutritionnelle (EREN)Centre d’Epidemiologie et Biostatistiques Sorbonne Paris Cité (CRESS)Inserm U1153, Inra U1125Cnam, COMUE Sorbonne‐Paris‐Cité Bobigny France
| | - Christiane Guinot
- Computer Science LaboratoryUniversity François Rabelais of Tours Tours France
| | - Leopold Fezeu
- Université Paris 13Equipe de Recherche en Epidémiologie Nutritionnelle (EREN)Centre d’Epidemiologie et Biostatistiques Sorbonne Paris Cité (CRESS)Inserm U1153, Inra U1125Cnam, COMUE Sorbonne‐Paris‐Cité Bobigny France
| | | | - Julie Latreille
- Department of Skin Knowledge & Women BeautyChanel R & T Pantin France
| | - Denis Malvy
- Université Paris 13Equipe de Recherche en Epidémiologie Nutritionnelle (EREN)Centre d’Epidemiologie et Biostatistiques Sorbonne Paris Cité (CRESS)Inserm U1153, Inra U1125Cnam, COMUE Sorbonne‐Paris‐Cité Bobigny France
- Department of Internal Medicine and Tropical DiseasesHôpital Saint‐André Bordeaux France
| | - Erwin Tschachler
- Department of DermatologyUniversity of Vienna Medical School Vienna Austria
| | - Jean‐François Zagury
- Équipe GénomiqueBioinformatique et ApplicationsChaire de BioinformatiqueConservatoire National des Arts et Métiers Paris France
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6
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Abstract
Chromatin is organized into higher-order structures that form subcompartments in interphase nuclei. Different categories of specialized enzymes act on chromatin and regulate its compaction and biophysical characteristics in response to physiological conditions. We present an overview of the function of chromatin structure and its dynamic changes in response to genotoxic stress, focusing on both subnuclear organization and the physical mobility of DNA. We review the requirements and mechanisms that cause chromatin relocation, enhanced mobility, and chromatin unfolding as a consequence of genotoxic lesions. An intriguing link has been established recently between enhanced chromatin dynamics and histone loss.
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Affiliation(s)
- Michael H Hauer
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland.,Faculty of Natural Sciences, University of Basel, CH-4056 Basel, Switzerland
| | - Susan M Gasser
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland.,Faculty of Natural Sciences, University of Basel, CH-4056 Basel, Switzerland
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7
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Wang WJ, Cai GY, Chen XM. Cellular senescence, senescence-associated secretory phenotype, and chronic kidney disease. Oncotarget 2017; 8:64520-64533. [PMID: 28969091 PMCID: PMC5610023 DOI: 10.18632/oncotarget.17327] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 03/24/2017] [Indexed: 12/19/2022] Open
Abstract
Chronic kidney disease (CKD) is increasingly being accepted as a type of renal ageing. The kidney undergoes age-related alterations in both structure and function. To date, a comprehensive analysis of cellular senescence and senescence-associated secretory phenotype (SASP) in CKD is lacking. Hence, this review mainly discusses the relationship between the two phenomena to show the striking similarities between SASP and CKD-associated secretory phenotype (CASP). It has been reported that replicative senescence, stress-induced premature ageing, and epigenetic abnormalities participate in the occurrence and development of CKD. Genomic damage and external environmental stimuli cause increased levels of oxidative stress and a chronic inflammatory state as a result of irreversible cell cycle arrest and low doses of SASP. Similar to SASP, CASP factors activate tissue repair by multiple mechanisms. Once tissue repair fails, the accumulated SASP or CASP species aggravate DNA damage response (DDR) and cause the senescent cells to secrete more SASP factors, accelerating the process of cellular ageing and eventually leading to various ageing-related changes. It is concluded that cellular senescence and SASP participate in the pathological process of CKD, and correspondingly CKD accelerated the progression of cell senescence and the secretion of SASP. These results will facilitate the integration of these mechanisms into the care and management of CKD and other age-related diseases.
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Affiliation(s)
- Wen-Juan Wang
- Department of Nephrology, Chinese PLA General Hospital, Chinese PLA Institute of Nephrology, State Key Laboratory of Kidney Diseases, National Clinical Research Center for Kidney Diseases, Beijing 100853, China
- Department of Nephrology, Beijing Changping Hospital, Beijing 102200, China
| | - Guang-Yan Cai
- Department of Nephrology, Chinese PLA General Hospital, Chinese PLA Institute of Nephrology, State Key Laboratory of Kidney Diseases, National Clinical Research Center for Kidney Diseases, Beijing 100853, China
| | - Xiang-Mei Chen
- Department of Nephrology, Chinese PLA General Hospital, Chinese PLA Institute of Nephrology, State Key Laboratory of Kidney Diseases, National Clinical Research Center for Kidney Diseases, Beijing 100853, China
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8
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Lee N, Ryu HG, Kwon JH, Kim DK, Kim SR, Wang HJ, Kim KT, Choi KY. SIRT6 Depletion Suppresses Tumor Growth by Promoting Cellular Senescence Induced by DNA Damage in HCC. PLoS One 2016; 11:e0165835. [PMID: 27824900 PMCID: PMC5100879 DOI: 10.1371/journal.pone.0165835] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 10/18/2016] [Indexed: 12/12/2022] Open
Abstract
The role of Sirtuin 6 (SIRT6) as a tumor suppressor or oncogene in liver cancer remains controversial. Thus, we identified the specific role of SIRT6 in the progression of hepatocellular carcinoma (HCC). SIRT6 expression was significantly higher in HCC cell lines and HCC tissues from 138 patients than in an immortalized hepatocyte cell line, THLE-2 and non-tumor tissues, respectively. SIRT6 knockdown by shRNA suppressed the growth of HCC cells and inhibited HCC tumor growth in vivo. In addition, SIRT6 silencing significantly prevented the growth of HCC cell lines by inducing cellular senescence in the p16/Rb- and p53/p21-pathway independent manners. Microarray analysis revealed that the expression of genes involved in nucleosome assembly was apparently altered in SIRT6-depleted Hep3B cells. SIRT6 knockdown promoted G2/M phase arrest and downregulation of genes encoding histone variants associated with nucleosome assembly, which could be attributed to DNA damage. Taken together, our findings suggest that SIRT6 acts as a tumor promoter by preventing DNA damage and cellular senescence, indicating that SIRT6 represents a potential therapeutic target for the treatment of HCC.
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Affiliation(s)
- Namgyu Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
| | - Hye Guk Ryu
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
| | | | - Dae-Kyum Kim
- Donnelly Centre, Departments of Molecular Genetics and Computer Science, University of Toronto, Toronto, Ontario, Canada
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Sae Rom Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
| | - Hee Jung Wang
- Department of Surgery, Ajou University School of Medicine, Suwon, Korea
| | - Kyong-Tai Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
- Division of Integrative Biosciences & Biotechnology, Pohang University of Science and Technology, Pohang, Gyeongbuk, Republic of Korea
| | - Kwan Yong Choi
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
- Division of Integrative Biosciences & Biotechnology, Pohang University of Science and Technology, Pohang, Gyeongbuk, Republic of Korea
- * E-mail:
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9
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Pang B, Qiao X, Janssen L, Velds A, Groothuis T, Kerkhoven R, Nieuwland M, Ovaa H, Rottenberg S, van Tellingen O, Janssen J, Huijgens P, Zwart W, Neefjes J. Drug-induced histone eviction from open chromatin contributes to the chemotherapeutic effects of doxorubicin. Nat Commun 2013; 4:1908. [PMID: 23715267 PMCID: PMC3674280 DOI: 10.1038/ncomms2921] [Citation(s) in RCA: 275] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 04/19/2013] [Indexed: 12/24/2022] Open
Abstract
DNA topoisomerase II inhibitors are a major class of cancer chemotherapeutics, which are thought to eliminate cancer cells by inducing DNA double-strand breaks. Here we identify a novel activity for the anthracycline class of DNA topoisomerase II inhibitors: histone eviction from open chromosomal areas. We show that anthracyclines promote histone eviction irrespective of their ability to induce DNA double-strand breaks. The histone variant H2AX, which is a key component of the DNA damage response, is also evicted by anthracyclines, and H2AX eviction is associated with attenuated DNA repair. Histone eviction deregulates the transcriptome in cancer cells and organs such as the heart, and can drive apoptosis of topoisomerase-negative acute myeloid leukaemia blasts in patients. We define a novel mechanism of action of anthracycline anticancer drugs doxorubicin and daunorubicin on chromatin biology, with important consequences for DNA damage responses, epigenetics, transcription, side effects and cancer therapy. Anthracycline-based drugs can kill cancer cells by inhibiting topoisomerase II and promoting DNA double-strand breaks. Pang et al. show that anthracyclines also induce eviction of histones from open chromatin regions and, in doing so, modulate DNA repair and apoptosis in human cancer cells.
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Affiliation(s)
- Baoxu Pang
- Division of Cell Biology, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066CX, The Netherlands
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10
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Sustained activation of Akt elicits mitochondrial dysfunction to block Plasmodium falciparum infection in the mosquito host. PLoS Pathog 2013; 9:e1003180. [PMID: 23468624 PMCID: PMC3585164 DOI: 10.1371/journal.ppat.1003180] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 12/17/2012] [Indexed: 12/20/2022] Open
Abstract
The overexpression of activated, myristoylated Akt in the midgut of female transgenic Anopheles stephensi results in resistance to infection with the human malaria parasite Plasmodium falciparum but also decreased lifespan. In the present study, the understanding of mitochondria-dependent midgut homeostasis has been expanded to explain this apparent paradox in an insect of major medical importance. Given that Akt signaling is essential for cell growth and survival, we hypothesized that sustained Akt activation in the mosquito midgut would alter the balance of critical pathways that control mitochondrial dynamics to enhance parasite killing at some cost to survivorship. Toxic reactive oxygen and nitrogen species (RNOS) rise to high levels in the midgut after blood feeding, due to a combination of high NO production and a decline in FOXO-dependent antioxidants. Despite an apparent increase in mitochondrial biogenesis in young females (3 d), energy deficiencies were apparent as decreased oxidative phosphorylation and increased [AMP]/[ATP] ratios. In addition, mitochondrial mass was lower and accompanied by the presence of stalled autophagosomes in the posterior midgut, a critical site for blood digestion and stem cell-mediated epithelial maintenance and repair, and by functional degradation of the epithelial barrier. By 18 d, the age at which An. stephensi would transmit P. falciparum to human hosts, mitochondrial dysfunction coupled to Akt-mediated repression of autophagy/mitophagy was more evident and midgut epithelial structure was markedly compromised. Inhibition of RNOS by co-feeding of the nitric-oxide synthase inhibitor L-NAME at infection abrogated Akt-dependent killing of P. falciparum that begins within 18 h of infection in 3–5 d old mosquitoes. Hence, Akt-induced changes in mitochondrial dynamics perturb midgut homeostasis to enhance parasite resistance and decrease mosquito infective lifespan. Further, quality control of mitochondrial function in the midgut is necessary for the maintenance of midgut health as reflected in energy homeostasis and tissue repair and renewal. Malaria is a major public health problem in the world and various strategies are under development for control, including vaccines and transgenic mosquitoes that block parasite transmission. We previously reported that overexpression of the major signaling protein Akt in the midgut of female Anopheles stephensi mosquitoes could impart resistance to infection with the most important human malaria parasite and also reduce the duration of mosquito infectivity to human hosts. However, to use this strategy for malaria transmission control in endemic areas, we must understand the mechanism by which parasites are killed to ensure that transmission of other human pathogens (e.g., viruses, nematodes) is not unexpectedly enhanced and to allow the design of rational, preventive interventions. Here, we report that overexpression of a constitutively active Akt in the mosquito midgut alters important cellular, and in particular, mitochondrial processes – in a manner similar to Akt control of these processes in mammalian cells – to generate high levels of toxic compounds that kill parasites within hours after infection. However, the same alterations in mitochondrial processes that result in parasite killing ultimately reduce mosquito infective lifespan for transmission, indicating that mitochondrial dynamics in the mosquito midgut could be targeted for multi-faceted genetic control of mosquito biology to reduce malaria transmission.
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11
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Shi L, Oberdoerffer P. Chromatin dynamics in DNA double-strand break repair. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1819:811-9. [PMID: 22285574 DOI: 10.1016/j.bbagrm.2012.01.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 12/28/2011] [Accepted: 01/05/2012] [Indexed: 12/29/2022]
Abstract
DNA double-strand breaks (DSBs) occur in the context of a highly organized chromatin environment and are, thus, a significant threat to the epigenomic integrity of eukaryotic cells. Changes in break-proximal chromatin structure are thought to be a prerequisite for efficient DNA repair and may help protect the structural integrity of the nucleus. Unlike most bona fide DNA repair factors, chromatin influences the repair process at several levels: the existing chromatin context at the site of damage directly affects the access and kinetics of the repair machinery; DSB induced chromatin modifications influence the choice of repair factors, thereby modulating repair outcome; lastly, DNA damage can have a significant impact on chromatin beyond the site of damage. We will discuss recent findings that highlight both the complexity and importance of dynamic and tightly orchestrated chromatin reorganization to ensure efficient DSB repair and nuclear integrity. This article is part of a Special Issue entitled: Chromatin in time and space.
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Affiliation(s)
- Lei Shi
- Mouse Cancer Genetics Program, NCI- Frederick, NIH, Frederick, MD 21702, USA
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