DOCSLIB.ORG

Myeloid Sirtuin 6 Deficiency Causes Insulin Resistance in High-Fat Diet

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Myeloid Sirtuin 6 Deficiency Causes Insulin Resistance in High-Fat Diet Diabetes Volume 66, October 2017 2659 Myeloid Sirtuin 6 Deficiency Causes Insulin Resistance in High-Fat Diet–Fed Mice by Eliciting Macrophage Polarization Toward an M1 Phenotype Youngyi Lee,1 Sun-O Ka,1 Hye-Na Cha,2 Yu-Na Chae,3 Mi-Kyung Kim,3 So-Young Park,2 Eun Ju Bae,4 and Byung-Hyun Park1 Diabetes 2017;66:2659–2668 | https://doi.org/10.2337/db16-1446 Obesity-related insulin resistance is closely associated in both humans and rodents (1). The increase in with macrophage accumulation and subsequent cytokine adipose tissue macrophages (ATMs) observed with obe- release in local tissues. Sirtuin 6 (Sirt6) is known to exert sity is also accompanied by macrophage phenotype an anti-inflammatory function, but its role in macrophages shifts. Although alternatively activated M2 macrophages 2 in the context of obesity has not been investigated. We (F4/80+CD11b+CD11c ) predominate in lean adipose tis- generated myeloid-specific Sirt6 knockout (mS6KO) mice sue, the balance shifts toward proinflammatory M1 macro- PATHOPHYSIOLOGY and investigated the metabolic characteristics after high- phages (F4/80+CD11b+CD11c+) as obesity develops (2). M1 fat diet (HFD) feeding for 16 weeks. Compared with macrophages secrete a variety of proinflammatory cyto- their wild-type littermates, HFD-fed mS6KO mice exhibited kines and chemokines, including tumor necrosis factor greater increases in body weight, fasting blood glucose (TNF)-a, interleukin-6 (IL-6), and MCP-1 (3). These cyto- and insulin levels, hepatic steatosis, glucose intolerance, kines activate inflammatory signaling pathways such as the and insulin resistance. Gene expression, histology, and flow inhibitor of kB kinase (IKK) and c-Jun NH -terminal kinase cytometric analyses demonstrated that liver and adi- 2 posetissueinflammation were elevated in HFD-fed mS6KO (JNK) pathways, which impair insulin activation of the mice relative to wild type, with a greater accumulation phosphoinositide 3-kinase and Akt pathways (4). Similarly, of F4/80+CD11b+CD11c+ adipose tissue macrophages. activation of resident liver macrophages (Kupffer cells) and Myeloid Sirt6 deletion facilitated proinflammatory M1 po- recruitment of circulating monocytes into the liver have larization of bone marrow macrophages and augmented been observed in animals fed a high-fat diet (HFD) and is the migration potential of macrophages toward adipose- causally implicated in the onset and progression of hepatic derived chemoattractants. Mechanistically, Sirt6 deletion insulin resistance (5). in macrophages promoted the activation of nuclear factor- Sirtuin 6 (Sirt6), one of the seven mammalian sirtuins, kB(NF-kB) and endogenous production of interleukin-6, is a nuclear protein and acts as an ADP-ribosyl transfer- which led to STAT3 activation and the positive feedback ase and NAD+-dependent deacetylase (6). Sirt6 deacetylates circuits for NF-kB stimulation; this cross talk expedited an histoneH3atlysine9(H3K9)andlysine56(H3K56), M1 polarization. We conclude that Sirt6 in macrophages is which results in chromatin condensation and decreased required for the prevention of obesity-associated tissue chromatin accessibility (7,8). Studies have suggested a ben- inflammation and insulin resistance. eficial role for Sirt6 in inflammation and metabolic stress. By deacetylating H3K9 on the promoters of nuclear factor- kB(NF-kB) target genes, Sirt6 alters chromatin structure to Accumulation of macrophages in adipose tissue is positively facilitate NF-kB destabilization at chromatin and termina- correlated with body weight and causes insulin resistance tion of NF-kB signaling (9). Knockdown of Sirt6 in human 1Department of Biochemistry, Chonbuk National University Medical School, This article contains Supplementary Data online at http://diabetes Jeonju, Jeonbuk, Republic of Korea .diabetesjournals.org/lookup/suppl/doi:10.2337/db16-1446/-/DC1. 2 Department of Physiology, College of Medicine, Yeungnam University, Daegu, © 2017 by the American Diabetes Association. Readers may use this article as North Gyeongsang, Republic of Korea long as the work is properly cited, the use is educational and not for profit, and the 3 Research Institute of Dong-A ST, Yongin, Gyeonggi, Republic of Korea work is not altered. More information is available at http://www.diabetesjournals 4 College of Pharmacy, Woosuk University, Wanju, Jeonbuk, Republic of Korea .org/content/license. Corresponding authors: Eun Ju Bae, [email protected], and Byung-Hyun Park, See accompanying article, p. 2535. [email protected]. Received 28 November 2016 and accepted 20 April 2017. 2660 Myeloid Sirt6 Controls Macrophage Polarization Diabetes Volume 66, October 2017 umbilical vein endothelial cells increases the expression of andareexpressedasmilligramsofTGper100mgofliver proinflammatory cytokines (10), whereas overexpression of tissue. Sirt6inmiceisprotectiveagainstmetabolicpathologies caused by diet-induced obesity (11). In contrast, ablation Histology of neural Sirt6 causes obesity (12). Additional evidence for Fixed tissues were embedded in 10% formalin solution. the anti-inflammatory properties of Sirt6 has been provided Tissue sections (5 mmforliverand7mm for adipose tissue) in autoimmune disease and allergic airway inflammation were stained with hematoxylin-eosin (H-E) for light micros- models (13,14). copy. Immunohistochemical staining was performed by us- Weandothershavereportedthatmyeloid-specificSirt1 ing the EnVision system (DAKO, Carpinteria, CA). Sections knockout (KO) mice develop tissue inflammation and insulin were immunostained with antibodies against F4/80, CD11b resistance upon exposure to an HFD (15,16). However, no (Abcam, Cambridge, U.K.), or perilipin (Fitzgerald, Acton, study to our knowledge has investigated whether Sirt6 has MA). Peroxidase activity was detected with 3-amino-9-ethyl a similar impact in macrophages or, more importantly, on carbazole. To assess morphological changes in liver, we used how myeloid Sirt6 affects inflammatory and metabolic re- the nonalcoholic fatty liver disease (NAFLD) activity score sponses in mice under acute and chronic metabolic stress. (NAS), which includes histological features and has been fi – With the aim of evaluating the influence of Sirt6 on macro- de ned as the unweighted sum of scores for steatosis (0 3), fl – – phage infiltration and inflammation in local tissues of mice, lobular in ammation (0 3), and ballooning (0 2) (19). The we generated myeloid-specific Sirt6 KO (mS6KO) mice. After adipocyte area in selected fat tissue sections was measured feeding these mice a normal chow diet (NCD) or an HFD, by using iSolution DT 36 software (Carl Zeiss, Oberkochen, we characterized tissue inflammation and glucose ho- Germany). The number of crown-like structures (CLSs) fi meostasis. In addition, we studied the effects of Sirt6 on was counted in 10 different high-power elds from each macrophage polarization and chemotaxis and their corre- section. sponding signaling pathways in isolated bone marrow mac- Cell Culture and In Vitro Migration Assay rophages (BMMs). BMMs were obtained from bone marrow cells by cultivation for 6 days in a-minimum essential medium supplemented RESEARCH DESIGN AND METHODS with 30% L929 conditioned medium (CM). For M1 or M2 Animal Experiments differentiation, BMMs were treated with lipopolysaccharide fl fl Sirt6 ox/ ox mice (B6;129-Sirt6tm1Ygu/J) were crossed with (LPS) (10 ng/mL) + interferon-g (IFN-g) (50 units/mL) or LysM-Cre (B6.129P2-lyz2tm1(cre)Ifo/J) mice to generate IL-4 (10 ng/mL), respectively. To prepare 3T3-L1 CM for mS6KO mice (Supplementary Fig. 1A). Male mS6KO mice in vitro migration assay, fully differentiated 3T3-L1 cells and age-matched littermates .6 weeks of age were fed ad were further cultured in migration media for 2 days, and libitum either an NCD or a 60% HFD (Research Diets, New the supernatants were harvested. For migration assays, Brunswick, NJ) for 16 weeks (Supplementary Table 1). The BMMs from wild-type (WT) or mS6KO mice were pretreated intraperitoneal glucose tolerance test (GTT) (1 g/kg of body with either Bay 11-7802 (Enzo Life Sciences, Farmingdale, weight) and insulin tolerance test (ITT) (0.5 units/kg of NY), Stattic (Santa Cruz Biotechnology, Dallas, TX), or LMT- body weight) were performed after 16 and 6 h of fasting, 28 (a gift from S.S. Hong, Inha University, Incheon, Republic respectively. A hyperinsulinemic-euglycemic clamp study of Korea) for 3 h. Cell migration was analyzed by using trans- (17), indirect calorimetry measurements (18), and stromal well migration assay chambers (BD Life Sciences, Franklin vascular fraction (SVF) isolation and FACS analysis (15) Lakes, NJ) by adding adipocyte CM to the lower chamber. were performed as previously described. All experimen- The DNA binding activity of STAT3 was detected by using a tal procedures were approved by the Institutional Animal TransAM STAT3 Kit (Active Motif, Carlsbad, CA). Care and Use Committees of Chonbuk National University Western Blotting (permit no. CBNU 2015-090) (Jeonbuk, Republic of Korea) Tissues and cells were homogenized in T-PER Tissue Protein and Yeungnam University (permit no. YUMC-AEC2015- Extraction Reagent or M-PER Mammalian Protein Extrac- 021) (Daegu, Republic of Korea). tion Reagent (Thermo Fisher Scientific, Waltham, MA). Biochemical Analysis Homogenates (20 mg of total protein) were separated by Plasma levels of various cytokines and enzymes were mea- SDS-PAGE and transferred to nitrocellulose membranes. sured by using specific ELISA kits (TNF-a,IL-1b,andIL-6 Blots were probed with primary antibodies
Load more

Recommended publications
  • Genetic Determinants Underlying Rare Diseases Identified Using Next-Generation Sequencing Technologies
    Western University Scholarship@Western Electronic Thesis and Dissertation Repository 8-2-2018 1:30 PM Genetic determinants underlying rare diseases identified using next-generation sequencing technologies Rosettia Ho The University of Western Ontario Supervisor Hegele, Robert A. The University of Western Ontario Graduate Program in Biochemistry A thesis submitted in partial fulfillment of the equirr ements for the degree in Master of Science © Rosettia Ho 2018 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Medical Genetics Commons Recommended Citation Ho, Rosettia, "Genetic determinants underlying rare diseases identified using next-generation sequencing technologies" (2018). Electronic Thesis and Dissertation Repository. 5497. https://ir.lib.uwo.ca/etd/5497 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract Rare disorders affect less than one in 2000 individuals, placing a huge burden on individuals, families and the health care system. Gene discovery is the starting point in understanding the molecular mechanisms underlying these diseases. The advent of next- generation sequencing has accelerated discovery of disease-causing genetic variants and is showing numerous benefits for research and medicine. I describe the application of next-generation sequencing, namely LipidSeq™ ‒ a targeted resequencing panel for the identification of dyslipidemia-associated variants ‒ and whole-exome sequencing, to identify genetic determinants of several rare diseases. Utilization of next-generation sequencing plus associated bioinformatics led to the discovery of disease-associated variants for 71 patients with lipodystrophy, two with early-onset obesity, and families with brachydactyly, cerebral atrophy, microcephaly-ichthyosis, and widow’s peak syndrome.
    [Show full text]
  • Selection Signatures in Two Oldest Russian Native Cattle Breeds Revealed Using High- Density Single Nucleotide Polymorphism Analysis
    PLOS ONE RESEARCH ARTICLE Selection signatures in two oldest Russian native cattle breeds revealed using high- density single nucleotide polymorphism analysis Natalia Anatolievna Zinovieva1*, Arsen Vladimirovich Dotsev1, Alexander Alexandrovich Sermyagin1, Tatiana Evgenievna Deniskova1, Alexandra 1 1 2 Sergeevna Abdelmanova , Veronika Ruslanovna KharzinovaID , Johann SoÈ lkner , a1111111111 Henry Reyer3, Klaus Wimmers3, Gottfried Brem1,4 a1111111111 a1111111111 1 L.K. Ernst Federal Science Center for Animal Husbandry, Federal Agency of Scientific Organizations, settl. Dubrovitzy, Podolsk Region, Moscow Province, Russia, 2 Division of Livestock Sciences, University of a1111111111 Natural Resources and Life Sciences, Vienna, Austria, 3 Institute of Genome Biology, Leibniz Institute for a1111111111 Farm Animal Biology [FBN], Dummerstorf, Germany, 4 Institute of Animal Breeding and Genetics, University of Veterinary Medicine [VMU], Vienna, Austria * [email protected] OPEN ACCESS Citation: Zinovieva NA, Dotsev AV, Sermyagin AA, Abstract Deniskova TE, Abdelmanova AS, Kharzinova VR, et al. (2020) Selection signatures in two oldest Native cattle breeds can carry specific signatures of selection reflecting their adaptation to Russian native cattle breeds revealed using high- the local environmental conditions and response to the breeding strategy used. In this density single nucleotide polymorphism analysis. study, we comprehensively analysed high-density single nucleotide polymorphism (SNP) PLoS ONE 15(11): e0242200. https://doi.org/ genotypes
    [Show full text]
  • A Review of the Recent Advances Made with SIRT6 and Its Implications on Aging Related Processes, Major Human Diseases, and Possible Therapeutic Targets
    biomolecules Review A Review of the Recent Advances Made with SIRT6 and its Implications on Aging Related Processes, Major Human Diseases, and Possible Therapeutic Targets Rubayat Islam Khan †, Saif Shahriar Rahman Nirzhor † and Raushanara Akter * Department of Pharmacy, BRAC University, 1212 Dhaka, Bangladesh; [email protected] (R.I.K.); [email protected] (S.S.R.N.) * Correspondence: [email protected]; Tel.: +880-179-8321-273 † These authors contributed equally to this work. Received: 10 June 2018; Accepted: 26 June 2018; Published: 29 June 2018 Abstract: Sirtuin 6 (SIRT6) is a nicotinamide adenine dinucleotide+ (NAD+) dependent enzyme and stress response protein that has sparked the curiosity of many researchers in different branches of the biomedical sciences. A unique member of the known Sirtuin family, SIRT6 has several different functions in multiple different molecular pathways related to DNA repair, glycolysis, gluconeogenesis, tumorigenesis, neurodegeneration, cardiac hypertrophic responses, and more. Only in recent times, however, did the potential usefulness of SIRT6 come to light as we learned more about its biochemical activity, regulation, biological roles, and structure Frye (2000). Even until very recently, SIRT6 was known more for chromatin signaling but, being a nascent topic of study, more information has been ascertained and its potential involvement in major human diseases including diabetes, cancer, neurodegenerative diseases, and heart disease. It is pivotal to explore the mechanistic workings
    [Show full text]
  • Cell Migration: How Neutrophils Set Their Compass
    RESEARCH HIGHLIGHTS IN BRIEF CELL MIGRATION How neutrophils set their compass Sustained directionality is an essential component of successful chemotaxis. Here, the authors show that the G protein Gαi and the mammalian homologue of the Drosophila melanogaster polarity protein Inscuteable (known as MINSC) are important for the maintenance of polarity and directionality during neutrophil chemotaxis. They observed that Gαi (which is released from Gβγ following ligand binding) accumulates at the leading edge of the cell. Gαi interacts directly with AGS3 or LGN, which themselves are bound to MINSC, recruiting it to this part of the cell. Moreover, MINSC is bound to the polarity complex PAR3–PAR6– aPKC, and this interaction targets the complex to the leading edge, thus establishing polarity. Notably, MINSC-deficient neutrophils, or neutrophils in which aPKC was blocked, showed normal motility but lacked directionality in their chemotaxis. ORIGINAL RESEARCH PAPER Kamakura, S. et al. The cell polarity protein mInsc regulates neutrophil chemotaxis via a noncanonical G protein signaling pathway. Dev. Cell http://dx.doi.org/10.1016/j.devcel.2013.06.008 (2013) DNA DAMAGE Facilitating repair The repair of DNA double-strand breaks (DSBs) can be hindered by the inability of repair factors to access damage sites in the tightly packaged chromatin. This study identifies a key role for the deacetylase sirtuin 6 (SIRT6) in facilitating chromatin relaxation and promoting repair. Toiber et al. observed that SIRT6 is rapidly recruited to DSBs, with much faster kinetics than previously reported. SIRT6 was shown to target the chromatin remodelling factor SNF2H to these sites and accelerate its association with them, as well as to deacetylate histone 3 at Lys56 (H3K56), which was required for SNF2H-mediated chromatin relaxation.
    [Show full text]
  • Dear Author, Here Are the Proofs of Your Article. • You Can Submit Your
    Dear Author, Here are the proofs of your article. • You can submit your corrections online, via e-mail or by fax. • For online submission please insert your corrections in the online correction form. Always indicate the line number to which the correction refers. • You can also insert your corrections in the proof PDF and email the annotated PDF. • For fax submission, please ensure that your corrections are clearly legible. Use a fine black pen and write the correction in the margin, not too close to the edge of the page. • Remember to note the journal title, article number, and your name when sending your response via e-mail or fax. • Check the metadata sheet to make sure that the header information, especially author names and the corresponding affiliations are correctly shown. • Check the questions that may have arisen during copy editing and insert your answers/ corrections. • Check that the text is complete and that all figures, tables and their legends are included. Also check the accuracy of special characters, equations, and electronic supplementary material if applicable. If necessary refer to the Edited manuscript. • The publication of inaccurate data such as dosages and units can have serious consequences. Please take particular care that all such details are correct. • Please do not make changes that involve only matters of style. We have generally introduced forms that follow the journal’s style. Substantial changes in content, e.g., new results, corrected values, title and authorship are not allowed without the approval of the responsible editor. In such a case, please contact the Editorial Office and return his/her consent together with the proof.
    [Show full text]
  • Changes in Human Sirtuin 6 Gene Promoter Methylation During Aging
    574 BIOMEDICAL REPORTS 2: 574-578, 2014 Changes in human sirtuin 6 gene promoter methylation during aging KANIYE SAHIN, SIBEL YILMAZ and NERMIN GOZUKIRMIZI Department of Molecular Biology and Genetics, Faculty of Science, Istanbul University, 34118 Vezneciler, Istanbul, Turkey Received February 25, 2014; Accepted March 26, 2014 DOI: 10.3892/br.2014.266 Abstract. Aging is a natural process during which changes stress (7,8). Knockdown of SIRT6 in human cells renders at the cellular level increase death risk by developing suscep- them prone to chemically induced double-strand breaks (2,9). tibility to a variety of diseases. Sirtuins have been shown to SIRT6 deficiency in mice has been shown to lead to the devel- regulate lifespan in various organisms by deacetylating a opment of an acute degenerative aging-like phenotype (10). number of important transcription factors. Of the 7 identified Although studies on SIRT6 knockout mice reported a strong mammalian sirtuins (SIRT1-7), SIRT6 depletion is associ- correlation between premature aging and the absence of the ated with severe symptoms of premature aging. In this study, SIRT6 protein (10), the reports on the overexpression of sirtuin we investigated the association between human longevity homologues on various model organisms have been controver- and SIRT6 promoter methylation. Genomic DNA from sial, from no effect (11) to expansion of lifespan only in male blood samples of 55 individuals (34 females and 21 males) mice (12). Analyses at the mRNA and protein level revealed was examined to detect methylation levels by quantitative SIRT6 expression in the majority of mouse and human tissues, polymerase chain reaction analysis following bisulfite treat- with particularly high protein levels in the thymus, skeletal ment.
    [Show full text]
  • Induction of Therapeutic Tissue Tolerance Foxp3 Expression Is
    Downloaded from http://www.jimmunol.org/ by guest on October 2, 2021 is online at: average * The Journal of Immunology , 13 of which you can access for free at: 2012; 189:3947-3956; Prepublished online 17 from submission to initial decision 4 weeks from acceptance to publication September 2012; doi: 10.4049/jimmunol.1200449 http://www.jimmunol.org/content/189/8/3947 Foxp3 Expression Is Required for the Induction of Therapeutic Tissue Tolerance Frederico S. Regateiro, Ye Chen, Adrian R. Kendal, Robert Hilbrands, Elizabeth Adams, Stephen P. Cobbold, Jianbo Ma, Kristian G. Andersen, Alexander G. Betz, Mindy Zhang, Shruti Madhiwalla, Bruce Roberts, Herman Waldmann, Kathleen F. Nolan and Duncan Howie J Immunol cites 35 articles Submit online. Every submission reviewed by practicing scientists ? is published twice each month by Submit copyright permission requests at: http://www.aai.org/About/Publications/JI/copyright.html Receive free email-alerts when new articles cite this article. Sign up at: http://jimmunol.org/alerts http://jimmunol.org/subscription http://www.jimmunol.org/content/suppl/2012/09/17/jimmunol.120044 9.DC1 This article http://www.jimmunol.org/content/189/8/3947.full#ref-list-1 Information about subscribing to The JI No Triage! Fast Publication! Rapid Reviews! 30 days* Why • • • Material References Permissions Email Alerts Subscription Supplementary The Journal of Immunology The American Association of Immunologists, Inc., 1451 Rockville Pike, Suite 650, Rockville, MD 20852 Copyright © 2012 by The American Association of Immunologists, Inc. All rights reserved. Print ISSN: 0022-1767 Online ISSN: 1550-6606. This information is current as of October 2, 2021.
    [Show full text]
  • Boosting ATM Activity Promotes Longevity in Nematodes and Mice
    bioRxiv preprint doi: https://doi.org/10.1101/240606; this version posted December 28, 2017. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. Boosting ATM Activity Promotes Longevity in Nematodes and Mice Minxian Qian,1,2,3,6 Zuojun Liu,1,2,3,6 Linyuan Peng, 1,2,3 Fanbiao Meng,1,2,3 Xiaolong Tang,1,2,3 Ying Ao,1,3 Lei Shi,1,2,5 Mingyan Zhou,1,2,3 Ming Wang,1,2,4 Baoming Qin,4 Xinyue Cao,1,2,3 Zimei Wang,1,3 Zhongjun Zhou,5 Baohua Liu1,2,3* 1Guangdong Key Laboratory of Genome Stability and Human Disease Prevention, 2Medical Research Center, 3Department of Biochemistry & Molecular Biology, Shenzhen University Health Science Center, Shenzhen 518060, China 4South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China 5School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong 6Minxian Qian and Zuojun Liu contributed equally to this work. *Correspondence should be addressed to Dr Baohua Liu ([email protected]). Abstract DNA damage accumulates with age1. However, whether and how robust DNA repair machinery promotes longevity is elusive. Here, we demonstrate that activation of ataxia- telangiectasia mutated (ATM) via low dose of chloroquine (CQ) promotes DNA damage clearance, rescues age-related metabolic shift, and extends lifespan in nematodes and mice. Molecularly, ATM phosphorylates SIRT6 deacetylase and thus prevents MDM2- mediated ubiquitination and proteasomal degradation.
    [Show full text]
  • Sirtuin 6 (SIRT6) Rescues the Decline of Homologous Recombination Repair During Replicative Senescence
    Sirtuin 6 (SIRT6) rescues the decline of homologous recombination repair during replicative senescence Zhiyong Mao, Xiao Tian, Michael Van Meter, Zhonghe Ke, Vera Gorbunova1, and Andrei Seluanov1 Department of Biology, University of Rochester, Rochester, NY 14627 Edited by James E. Cleaver, University of California, San Francisco, CA, and approved June 12, 2012 (received for review January 12, 2012) Genomic instability is a hallmark of aging tissues. Genomic in- (10). SIRT6 has recently been identified as a component of the stability may arise from the inefficient or aberrant function of DNA HR pathway. SIRT6 participates in HR at two steps, by acti- double-stranded break (DSB) repair. DSBs are repaired by homolo- vating PARP1 at the early stages of DSB processing (11) and, gous recombination (HR) and nonhomologous DNA end joining later, by stimulating CtIP (12). (NHEJ). HR is a precise pathway, whereas NHEJ frequently leads to Aging organisms exhibit a diminished capacity to repair DSBs. deletions or insertions at the repair site. Here, we used normal It was shown that the recruitment of DSB repair proteins to human fibroblasts with a chromosomally integrated HR reporter DNA damage sites is delayed in lymphocytes of aged donors (13) cassette to examine the changes in HR efficiency as cells progress to and that cells from aged individuals contain a higher number of replicative senescence. We show that HR declines sharply with DSBs (14, 15). We showed previously that NHEJ declines up to increasing replicative age, with an up to 38-fold decrease in fourfold and becomes more error-prone in senescent cells (16).
    [Show full text]
  • Mahlknecht 17 8 29/12/05 15:21 Page 447
    Mahlknecht 17_8 29/12/05 15:21 Page 447 INTERNATIONAL JOURNAL OF ONCOLOGY 28: 447-456, 2006 447 Chromosomal organization and fluorescence in situ hybridization of the human Sirtuin 6 gene ULRICH MAHLKNECHT1, ANTHONY D. HO1 and SUSANNE VOELTER-MAHLKNECHT2 1Department of Hematology/Oncology, University of Heidelberg Medical Center, Im Neuenheimer Feld 410, D-69120 Heidelberg; 2Department of Occupational, Social and Environmental Medicine, University of Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany Received August 17, 2005; Accepted October 21, 2005 Abstract. Sirtuin 6 (SIRT6) is a member of the sirtuin Introduction deacetylases (sirtuins), which are derivatives of the yeast Silent information regulator 2 (Sir2) protein. SIR2 and its Based on structural and functional similarities, mammalian mammalian derivatives play a central role in epigenetic gene histone deacetylases are grouped into four categories, of silencing, recombination, metabolism, cell differentiation and which three contain non-sirtuin HDACs comprising the yeast in the regulation of aging. In contrast to most sirtuins, SIRT6 histone deacetylases, RPD3 (class I HDACs), HDA1 (class II lacks NAD+-dependent protein deacetylase activity. We have HDACs) and the more recently described HDAC11-related isolated and characterized the human Sirt6 genomic sequence, enzymes (class IV HDACs), while one category consists of which spans a region of 8,427 bp and which has one single sirtuin histone deacetylases (class III HDACs), which are genomic locus. Determination of the exon-intron splice homologs to the yeast Sir2 protein. SIRT1 is the mammalian junctions found the full-length SIRT6 protein to consist of sirtuin that is most closely related to S. cerevisiae SIR2.
    [Show full text]
  • Sirtuins in Metabolism, DNA Repair and Cancer Zhen Mei1,2†, Xian Zhang1,2†, Jiarong Yi1,2, Junjie Huang1,2, Jian He1,2 and Yongguang Tao1,2*
    Mei et al. Journal of Experimental & Clinical Cancer Research (2016) 35:182 DOI 10.1186/s13046-016-0461-5 REVIEW Open Access Sirtuins in metabolism, DNA repair and cancer Zhen Mei1,2†, Xian Zhang1,2†, Jiarong Yi1,2, Junjie Huang1,2, Jian He1,2 and Yongguang Tao1,2* Abstract The mammalian sirtuin family has attracted tremendous attention over the past few years as stress adaptors and post-translational modifier. They have involved in diverse cellular processes including DNA repair, energy metabolism, and tumorigenesis. Notably, genomic instability and metabolic reprogramming are two of characteristic hallmarks in cancer. In this review, we summarize current knowledge on the functions of sirtuins mainly regarding DNA repair and energy metabolism, and further discuss the implication of sirtuins in cancer specifically by regulating genome integrity and cancer-related metabolism. Keywords: Sirtuin, DNA damage, Metabolism, Cancer, Post-translation modification Background NAD+ changes, sirtuins are proposed to work as stress Sirtuins, the highly conserved NAD + −dependent en- adaptors. Meanwhile, given their diverse enzymatic ac- zymes, are mammalian homologs of the yeast Sir2 gene tivities, they are described to play critical roles in regu- which has been known to promote replicative life span lating post-translational modifications (PTMs), among and mediate gene silencing in yeast [1]. The sirtuin fam- which acetylation is an important form. Sirtuins deacety- ily comprises seven proteins denoted as SIRT1-SIRT7, late a multitude of targets including histones, transcrip- which share a highly conserved NAD + −binding cata- tion factors, and metabolic enzymes. Taken together, lytic domain but vary in N and C-termini (Fig. 1).
    [Show full text]
  • Microrna-22 Suppresses DNA Repair and Promotes Genomic
    Published OnlineFirst January 27, 2015; DOI: 10.1158/0008-5472.CAN-14-2783 Cancer Molecular and Cellular Pathobiology Research MicroRNA-22 Suppresses DNA Repair and Promotes Genomic Instability through Targeting of MDC1 Jung-Hee Lee1,2, Seon-Joo Park1,3, Seo-Yeon Jeong1, Min-Ji Kim1, Semo Jun1,4, Hyun-Seo Lee1, In-Youb Chang1,5, Sung-Chul Lim6, Sang Pil Yoon7, Jeongsik Yong8, and Ho Jin You1,4 Abstract MDC1 is critical component of the DNA damage response overexpression of constitutively active Akt1, homologous recom- (DDR) machinery and orchestrates the ensuring assembly of the bination was inhibited by miR-22–mediated MDC1 repression. DDR protein at the DNA damage sites, and therefore loss of In addition, during replicative senescence and stress-induced MDC1 results in genomic instability and tumorigenicity. How- premature senescence, MDC1 was downregulated by upregulat- ever, the molecular mechanisms controlling MDC1 expression are ing miR-22 and thereby accumulating DNA damage. Our results currently unknown. Here, we show that miR-22 inhibits MDC1 demonstrate a central role of miR-22 in the physiologic regulation translation via direct binding to its 30 untranslated region, leading of MDC1-dependent DDR and suggest a molecular mechanism to impaired DNA damage repair and genomic instability. We for how aberrant Akt1 activation and senescence lead to increased demonstrated that activated Akt1 and senescence hinder DDR genomic instability, fostering an environment that promotes function of MDC1 by upregulating endogenous miR-22. After tumorigenesis. Cancer Res; 75(7); 1–13. Ó2015 AACR. Introduction DNA double-strand breaks (DSB) activate the DDR by trigger- ing the kinase activity of ataxia telangiectasia mutated (ATM), Repeated exposure to both exogenous and endogenous insults thereby initiating a signaling cascade in which the histone variant challenges the integrity of cellular genomic material.
    [Show full text]