1301
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Abstract
The budding yeast Saccharomyces cerevisiae has long served as a model organism for the study of basic cellular processes. Its short generation time, well-established molecular genetics, and fully sequenced genome have made this organism a favorite of researchers in diverse fields. Much of the information obtained has been shown to apply to higher eukaryotes, including humans. Recently, researchers have begun using yeast to tackle one of the outstanding questions in science: How and why do organisms age? The identification of individual genes in yeast that can affect the aging process itself has elevated this single-celled fungus to full contender status in the aging field. In this Perspective, we present two fundamentally different measures of aging in yeast: replicative life-span and stationary phase survival (chronological life-span). We describe the benefits and limitations of each and present models that attempt to explain these "aging" phenomena. Finally, we present compelling evidence that the use of yeast as a model system will ultimately prove beneficial to the study of human aging.
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Affiliation(s)
- M Kaeberlein
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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1302
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Abstract
Long viewed as an insoluble enigma, aging is shedding its cloak of mystery as scientists start to understand why and how we age. Many studies support the theoretical argument that aging occurs because natural selection weakens with age, leaving us vulnerable to harmful, late-acting genes. As for what causes aging, scientists have narrowed the pack of candidates to a handful, including free radicals and reactions between glucose and proteins. In recent decades, many mechanisms for lengthening life in animals have come to light. By extending this research, scientists may be closing in on ways to lengthen the human life-span.
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1303
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Hasty P. The impact energy metabolism and genome maintenance have on longevity and senescence: lessons from yeast to mammals. Mech Ageing Dev 2001; 122:1651-62. [PMID: 11557271 DOI: 10.1016/s0047-6374(01)00294-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The phenomenon that caloric restriction increases life span in a variety of species from yeast to mice has been the focus of much interest. Recent observations suggest that a protein important for heterochromatin formation, Sir2, is central for caloric restriction-induced longevity in lower organisms. Interestingly, Sir2 is also capable of repairing DNA double-strand breaks by nonhomologous end joining which may be important, along with proteins that repair breaks by recombinational repair, for minimizing the age-related deleterious effects of DNA damage induced by oxygen by-products of metabolism. I propose that competition between these two distinct functions could influence longevity and the onset of senescence. In addition, sequence and functional similarities between Sir2 and other chromatin metabolism proteins present the possibility that genetic components for longevity and senescence are conserved from yeast to mammals.
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Affiliation(s)
- P Hasty
- Department of Molecular Medicine, Institute of Biotechnology, The University of Texas, Health Science Center at San Antonio, San Antonio, TX 78245-3207, USA.
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1304
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Aguilaniu H, Gustafsson L, Rigoulet M, Nyström T. Protein oxidation in G0 cells of Saccharomyces cerevisiae depends on the state rather than rate of respiration and is enhanced in pos9 but not yap1 mutants. J Biol Chem 2001; 276:35396-404. [PMID: 11431467 DOI: 10.1074/jbc.m101796200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Immunodetection of protein carbonyl groups demonstrates that growth arrest elicited by carbon or nitrogen starvation causes an increased oxidation of proteins in Saccharomyces cerevisiae. Mutant analysis suggests that the response regulator Pos9p is involved in mitigating self-inflicted oxidative damages in G(0) cells, whereas Yap1p is primarily required in growing cells. The data also suggest that oxidation of target proteins is not a priori an effect of arrest of cell division or nutrient depletion and cannot be explained by the respiratory activity alone nor a high ratio of catabolic/anabolic activity in G(0) cells. Instead, we observed that starvation elicits a transition in the respiratory state (from phosphorylating to nonphosphorylating respiration) and that this transition is associated with a stepwise increase in protein oxidation. During carbon starvation, this transition and increase in oxidation occurs immediately as the carbon source is depleted, growth is arrested, and the respiratory rate falls drastically. In contrast, during nitrogen starvation and excess carbon the respiratory state transition and stepwise increase in protein oxidation are markedly delayed and occur long after the nitrogen source has been depleted and division and growth-arrested. Oxidation in G(0) cells could be enhanced by treating cells with low concentrations of antimycin A and attenuated with myxothiazol, indicating that protein oxidation is intimately linked to reactive oxygen species generated by semiquinones of the Q-cycle. Thus, the work presented suggests that the degree of coupling in the mitochondrial respiratory apparatus rather then the overall rate of respiration affects the degree of protein oxidation in nondividing yeast cells.
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Affiliation(s)
- H Aguilaniu
- Department of Molecular Biotechnology, Chalmers University of Technology, Box 462, SE-405 30 Göteborg, Sweden
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1305
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Lin SS, Manchester JK, Gordon JI. Enhanced gluconeogenesis and increased energy storage as hallmarks of aging in Saccharomyces cerevisiae. J Biol Chem 2001; 276:36000-7. [PMID: 11461906 DOI: 10.1074/jbc.m103509200] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A relationship between life span and cellular glucose metabolism has been inferred from genetic manipulations and caloric restriction of model organisms. In this report, we have used the Snf1p glucose-sensing pathway of Saccharomyces cerevisiae to explore the genetic and biochemical linkages between glucose metabolism and aging. Snf1p is a serine/threonine kinase that regulates cellular responses to glucose deprivation. Loss of Snf4p, an activator of Snf1p, extends generational life span whereas loss of Sip2p, a presumed repressor of the kinase, causes an accelerated aging phenotype. An annotated data base of global age-associated changes in gene expression in isogenic wild-type, sip2Delta, and snf4Delta strains was generated from DNA microarray studies. The transcriptional responses suggested that gluconeogenesis and glucose storage increase as wild-type cells age, that this metabolic evolution is exaggerated in rapidly aging sip2Delta cells, and that it is attenuated in longer-lived snf4Delta cells. To test this hypothesis directly, we applied microanalytic biochemical methods to generation-matched cells from each strain and measured the activities of enzymes and concentrations of metabolites in the gluconeogenic, glycolytic, and glyoxylate pathways, as well as glycogen, ATP, and NAD(+). The sensitivity of the assays allowed comprehensive biochemical profiling to be performed using aliquots of the same cell populations employed for the transcriptional profiling. The results provided additional evidence that aging in S. cerevisiae is associated with a shift away from glycolysis and toward gluconeogenesis and energy storage. They also disclosed that this shift is forestalled by two manipulations that extend life span, caloric restriction and genetic attenuation of the normal age-associated increase in Snf1p activity. Together, these findings indicate that Snf1p activation is not only a marker of aging but also a candidate mediator, because a shift toward energy storage over expenditure could impact myriad aspects of cellular maintenance and repair.
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Affiliation(s)
- S S Lin
- Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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1306
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Mattson MP, Duan W, Lee J, Guo Z, Roth GS, Ingram DK, Lane MA. Progress in the Development of Caloric Restriction Mimetic Dietary Supplements. ACTA ACUST UNITED AC 2001. [DOI: 10.1089/109454501753249993] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Mark P. Mattson
- Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, Baltimore, Maryland and Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Wenzhen Duan
- Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, Baltimore, Maryland
| | - Jaewon Lee
- Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, Baltimore, Maryland
| | - Zhihong Guo
- Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, Baltimore, Maryland
| | - George S. Roth
- Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, Baltimore, Maryland
| | - Donald K. Ingram
- Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, Baltimore, Maryland
| | - Mark A. Lane
- Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, Baltimore, Maryland
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1307
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Affiliation(s)
- Glenn S. Gerhard
- Department of Pathology, Dartmouth Medical School, Hanover, New Hampshire
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1308
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Tsang WY, Sayles LC, Grad LI, Pilgrim DB, Lemire BD. Mitochondrial respiratory chain deficiency in Caenorhabditis elegans results in developmental arrest and increased life span. J Biol Chem 2001; 276:32240-6. [PMID: 11410594 DOI: 10.1074/jbc.m103999200] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The growth and development of Caenorhabditis elegans are energy-dependent and rely on the mitochondrial respiratory chain (MRC) as the major source of ATP. The MRC is composed of approximately 70 nuclear and 12 mitochondrial gene products. Complexes I and V are multisubunit proteins of the MRC. The nuo-1 gene encodes the NADH- and FMN-binding subunit of complex I, the NADH-ubiquinone oxidoreductase. The atp-2 gene encodes the active-site subunit of complex V, the ATP synthase. The nuo-1(ua1) and atp-2(ua2) mutations are both lethal. They result in developmental arrest at the third larval stage (L3), arrest of gonad development at the second larval stage (L2), and impaired mobility, pharyngeal pumping, and defecation. Surprisingly, the nuo-1 and atp-2 mutations significantly lengthen the life spans of the arrested animals. When MRC biogenesis is blocked by chloramphenicol or doxycycline (inhibitors of mitochondrial translation), a quantitative and homogeneous developmental arrest as L3 larvae also results. The common phenotype induced by the mutations and drugs suggests that the L3-to-L4 transition may involve an energy-sensing developmental checkpoint. Since approximately 200 gene products are needed for MRC assembly and mtDNA replication, transcription, and translation, we predict that L3 arrest will be characteristic of mutations in these genes.
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Affiliation(s)
- W Y Tsang
- Canadian Institutes of Health Research Group in the Molecular Biology of Membrane Proteins, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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1309
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Abstract
Although eukaryotic G-protein coupled receptor (GPCR) systems are well known for their ability to detect and mediate rapid responses to extracellular signals, the full range of stimuli to which they respond may not yet have been identified. Activation of GPCRs by hormones, pheromones, odorants, neurotransmitters, light and different taste compounds is well established. However, the recent discovery of a glucose-sensing GPCR system in Saccharomyces cerevisiae has unexpectedly added common nutrients to this list of stimuli. This GPCR system mediates glucose activation of adenylate cyclase during the switch from respirative/gluconeogenic metabolism to fermentation. The GPCR system involved in pheromone signalling in S. cerevisiae has already served as an important model and tool for the study of GPCR systems in higher eukaryotic cell types. Here, we highlight the similarities and differences between these two signalling systems. We also indicate how the new glucose-sensing system can serve as a model for GPCR function and as a tool with which to screen for heterologous components of signalling pathways as well as for novel ligands in high-throughput assays.
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Affiliation(s)
- M Versele
- Laboratorium voor Moleculaire Celbiologie, Katholieke Universiteit Leuven, Kasteelpark Arenberg 31, B-3001 Leuven-Heverlee, Belgium
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1310
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Affiliation(s)
- J Dworkin
- Department of Molecular and Cellular Biology, The Biological Laboratories, Harvard University, Cambridge, Massachusetts 02138, USA.
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1311
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Abstract
The SIR2 protein family comprises a novel class of nicotinamide-adenine dinucleotide (NAD)-dependent protein deacetylases that function in transcriptional silencing, DNA repair, and life-span extension in Saccharomyces cerevisiae. Two crystal structures of a SIR2 homolog from Archaeoglobus fulgidus complexed with NAD have been determined at 2.1 A and 2.4 A resolutions. The structures reveal that the protein consists of a large domain having a Rossmann fold and a small domain containing a three-stranded zinc ribbon motif. NAD is bound in a pocket between the two domains. A distinct mode of NAD binding and an unusual configuration of the zinc ribbon motif are observed. The structures also provide important insights into the catalytic mechanism of NAD-dependent protein deacetylation by this family of enzymes.
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Affiliation(s)
- J Min
- W. M. Keck Structural Biology Laboratory, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
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1312
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Affiliation(s)
- C Kenyon
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA.
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1313
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Fabrizio P, Pozza F, Pletcher SD, Gendron CM, Longo VD. Regulation of longevity and stress resistance by Sch9 in yeast. Science 2001; 292:288-90. [PMID: 11292860 DOI: 10.1126/science.1059497] [Citation(s) in RCA: 659] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The protein kinase Akt/protein kinase B (PKB) is implicated in insulin signaling in mammals and functions in a pathway that regulates longevity and stress resistance in Caenorhabditis elegans. We screened for long-lived mutants in nondividing yeast Saccharomyces cerevisiae and identified mutations in adenylate cyclase and SCH9, which is homologous to Akt/PKB, that increase resistance to oxidants and extend life-span by up to threefold. Stress-resistance transcription factors Msn2/Msn4 and protein kinase Rim15 were required for this life-span extension. These results indicate that longevity is associated with increased investment in maintenance and show that highly conserved genes play similar roles in life-span regulation in S. cerevisiae and higher eukaryotes.
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Affiliation(s)
- P Fabrizio
- Division of Biogerontology, Andrus Gerontology Center, and Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-0191, USA
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1314
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Abstract
Ageing can evolve by mutation accumulation and pleiotropy (trade-offs). The relative prevalence of these two mechanisms is important for determining the likelihood that mechanisms of ageing are homologous in distantly related organisms, and hence the relevance of long-lived organisms to general mechanisms of ageing. Experimental work with Drosophila, examining the properties of standing genetic variation and mutations that accumulate in real time, has provided little evidence in favour of a role for mutation accumulation, but considerable support for the importance of trade-offs, particularly between early fertility and the rate of ageing. Evidence for the roles of these two processes in the evolution of long-livedness can be derived from the response to selection, comparative studies of life history traits and testing for potential trade-offs at the mechanistic level.
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Affiliation(s)
- L Partridge
- Department of Biology, University College London, Wolfson House, 4 Stephenson Way, NW1 2HE, London, UK.
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1315
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Abstract
The model organism Saccharomyces cerevisiae is providing new insights into the molecular and cellular changes that are related to aging. The yeast protein Sir2p (Silent Information Regulator 2) is a histone deacetylase involved in transcriptional silencing and the control of genomic stability. Recent results have led to the identification of Sir2p as a crucial determinant of yeast life span. Dosage, intracellular localization, and activity of Sir2p all have important effects on yeast longevity. For instance, calorie restriction apparently increases yeast life span by increasing Sir2p activity. Since Sir2p-related proteins have been identified in many prokaryotic and eukaryotic organisms, the fundamental principles derived from the studies in yeast may prove valuable in directing our future research toward an understanding of the mechanisms of aging in higher eukaryotes. BioEssays 23:327-332, 2001.
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Affiliation(s)
- P A Defossez
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
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1316
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Abstract
Can studying cultured cells inform us about the biology of aging? The idea that this may be was stimulated by the first formal description of replicative senescence. Replicative senescence limits the proliferation of normal human cells in culture, causing them to irreversibly arrest growth and adopt striking changes in cell function. We now know that telomere shortening, which occurs in most somatic cells as a consequence of DNA replication, drives replicative senescence in human cells. However, rodent cells also undergo replicative senescence, despite very long telomeres, and DNA damage, the action of certain oncogenes and changes in chromatin induce a phenotype similar to that of replicatively senescent cells. Thus, replicative senescence is an example of the more general process of cellular senescence, indicating that the telomere hypothesis of aging is a misnomer, Cellular senescence appears to be a response to potentially oncogenic insults, including oxidative stress. The growth arrest almost certainly suppresses tumorigenesis, at least in young organisms, whereas the functional changes may contribute to aging, although this has yet to be critically tested. Thus, cellular senescence may be an example of antagonistic pleiotropy. Cross-species comparisons suggest there is a relationship between the senescence of cells in culture and organismal life span, but the relationship is neither quantitative nor direct.
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Affiliation(s)
- J Campisi
- Life Sciences Division, Lawrence Berkeley National Laboratory, Mailstop 84-171, 1 Cyclotron Road, Berkeley, CA 94720, USA.
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1317
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MacLean M, Harris N, Piper PW. Chronological lifespan of stationary phase yeast cells; a model for investigating the factors that might influence the ageing of postmitotic tissues in higher organisms. Yeast 2001; 18:499-509. [PMID: 11284006 DOI: 10.1002/yea.701] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Budding yeast can be considered to have two distinct lifespans: (a) a replicative (budding, non-chronological) lifespan, measured as the number of daughters produced by each actively dividing mother cell; and (ii) a chronological lifespan, measured as the ability of stationary cultures to maintain viability over time. In non-dividing cells, essential components that become damaged cannot be diluted out through cell division but must, of necessity, be turned over and renewed. By elevating stress resistances, many of the activities needed for such renewal should be elevated with commensurate reduction in the steady-state levels of damaged cell components. Therefore, chronological lifespan in particular might be expected to relate to stress resistance. For yeast to attain a full chronological lifespan requires the expression of the general stress response. It is more important, though, that the cells should be efficiently adapted to respiratory maintenance, since it is cultures grown to stationary phase on respiratory media that usually display the longest chronological lifespans. For this reason, respiration-adapted cells potentially provide a better model of chronological ageing than cultures pre-grown on glucose.
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Affiliation(s)
- M MacLean
- Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK
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1318
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Schweiger M, Hennig K, Lerner F, Niere M, Hirsch-Kauffmann M, Specht T, Weise C, Oei SL, Ziegler M. Characterization of recombinant human nicotinamide mononucleotide adenylyl transferase (NMNAT), a nuclear enzyme essential for NAD synthesis. FEBS Lett 2001; 492:95-100. [PMID: 11248244 DOI: 10.1016/s0014-5793(01)02180-9] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Nicotinamide mononucleotide adenylyl transferase (NMNAT) is an essential enzyme in all organisms, because it catalyzes a key step of NAD synthesis. However, little is known about the structure and regulation of this enzyme. In this study we established the primary structure of human NMNAT. The human sequence represents the first report of the primary structure of this enzyme for an organism higher than yeast. The enzyme was purified from human placenta and internal peptide sequences determined. Analysis of human DNA sequence data then permitted the cloning of a cDNA encoding this enzyme. Recombinant NMNAT exhibited catalytic properties similar to the originally purified enzyme. Human NMNAT (molecular weight 31932) consists of 279 amino acids and exhibits substantial structural differences to the enzymes from lower organisms. A putative nuclear localization signal was confirmed by immunofluorescence studies. NMNAT strongly inhibited recombinant human poly(ADP-ribose) polymerase 1, however, NMNAT was not modified by poly(ADP-ribose). NMNAT appears to be a substrate of nuclear kinases and contains at least three potential phosphorylation sites. Endogenous and recombinant NMNAT were phosphorylated in nuclear extracts in the presence of [gamma-(32)P]ATP. We propose that NMNAT's activity or interaction with nuclear proteins are likely to be modulated by phosphorylation.
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Affiliation(s)
- M Schweiger
- Institut für Biochemie, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany
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1319
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Tissenbaum HA, Guarente L. Increased dosage of a sir-2 gene extends lifespan in Caenorhabditis elegans. Nature 2001; 410:227-30. [PMID: 11242085 DOI: 10.1038/35065638] [Citation(s) in RCA: 1416] [Impact Index Per Article: 61.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In Caenorhabditis elegans, mutations that reduce the activity of an insulin-like receptor (daf-2) or a phosphatidylinositol-3-OH kinase (age-1) favour entry into the dauer state during larval development and extend lifespan in adults. Downregulation of this pathway activates a forkhead transcription factor (daf-16), which may regulate targets that promote dauer formation in larvae and stress resistance and longevity in adults. In yeast, the SIR2 gene determines the lifespan of mother cells, and adding an extra copy of SIR2 extends lifespan. Sir2 mediates chromatin silencing through a histone deacetylase activity that depends on NAD (nicotinamide adenine dinucleotide) as a cofactor. We have surveyed the lifespan of C. elegans strains containing duplications of chromosomal regions. Here we report that a duplication containing sir-2.1-the C. elegans gene most homologous to yeast SIR2-confers a lifespan that is extended by up to 50%. Genetic analysis indicates that the sir-2.1 transgene functions upstream of daf-16 in the insulin-like signalling pathway. Our findings suggest that Sir2 proteins may couple longevity to nutrient availability in many eukaryotic organisms.
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Affiliation(s)
- H A Tissenbaum
- Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA
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1320
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1321
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Mobbs CV, Bray GA, Atkinson RL, Bartke A, Finch CE, Maratos-Flier E, Crawley JN, Nelson JF. Neuroendocrine and pharmacological manipulations to assess how caloric restriction increases life span. J Gerontol A Biol Sci Med Sci 2001; 56 Spec No 1:34-44. [PMID: 12088210 DOI: 10.1093/gerona/56.suppl_1.34] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
As part of an effort to review current understanding of the mechanisms by which caloric restriction (CR) extends maximum life span, the authors of the present review were requested to develop a list of key issues concerning the potential role of neuroendocrine systems in mediating these effects. It has long been hypothesized that failure of specific neuroendocrine functions during aging leads to key age-related systemic and physiological failures, and more recently it has been postulated that physiological neuroendocrine responses to CR may increase life span. However, although the acute neuroendocrine responses to fasting have been well studied, it is not clear that these responses are necessarily identical to those observed in response to the chronic moderate (30% to 50% reduction) CR that increases maximum life span. Therefore the recommendations of this panel fall into two categories. First, further characterization of neuroendocrine responses to CR over the entire life span is needed. Second, rigorous interventional studies are needed to test the extent to which neuroendocrine responses to CR mediate the effects of CR on life span, or alternatively if CR protects the function of essential neuroendocrine cells whose impairment reduces life span. Complementary studies using rodent models, nonhuman primates, and humans will be essential to assess the generality of elucidated mechanisms, and to determine if such mechanisms might apply to humans.
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Affiliation(s)
- C V Mobbs
- Department of Neurobiology, Mt. Sinai School of Medicine, New York City, NY 10029, USA.
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1322
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Abstract
Support for research in basic gerontology in the United States of America is briefly described. The support mechanisms, how to apply for a grant, and priority areas of research are outlined, and recent progress in a few of these priority areas is discussed. In general, government support for biogerontology research has been generous, and as a result considerable progress has been made in understanding the molecular mechanisms of aging in animal model systems. Translation of these findings to humans, and development of interventions to promote healthy aging in humans remain an unfulfilled priority, but new knowledge and development of better technologies and model systems suggest an optimistic future.
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Affiliation(s)
- H R Warner
- Biology of Aging Program, National Institute on Aging, Suite 2C231, 7201 Wisconsin Avenue, Gateway Building, Bethesda, MD 20892, USA.
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1323
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Asher G, Lotem J, Cohen B, Sachs L, Shaul Y. Regulation of p53 stability and p53-dependent apoptosis by NADH quinone oxidoreductase 1. Proc Natl Acad Sci U S A 2001; 98:1188-93. [PMID: 11158615 PMCID: PMC14730 DOI: 10.1073/pnas.98.3.1188] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The tumor suppressor gene wild-type p53 encodes a labile protein that accumulates in cells after different stress signals and can cause either growth arrest or apoptosis. One of the p53 target genes, p53-inducible gene 3 (PIG3), encodes a protein with significant homology to oxidoreductases, enzymes involved in cellular responses to oxidative stress and irradiation. This fact raised the possibility that cellular oxidation-reduction events controlled by such enzymes also may regulate the level of p53. Here we show that NADH quinone oxidoreductase 1 (NQO1) regulates p53 stability. The NQO1 inhibitor dicoumarol caused a reduction in the level of both endogenous and gamma-irradiation-induced p53 in HCT116 human colon carcinoma cells. This reduction was prevented by the proteasome inhibitors MG132 and lactacystin, suggesting enhanced p53 degradation in the presence of dicoumarol. Dicoumarol-induced degradation of p53 also was prevented in the presence of simian virus 40 large T antigen, which is known to bind and to stabilize p53. Cells overexpressing NQO1 were resistant to dicoumarol, and this finding indicates the direct involvement of NQO1 in p53 stabilization. NQO1 inhibition induced p53 degradation and blocked wild-type p53-mediated apoptosis in gamma-irradiated normal thymocytes and in M1 myeloid leukemic cells that overexpress wild-type p53. Dicoumarol also reduced the level of p53 in its mutant form in M1 cells. The results indicate that NQO1 plays an important role in regulating p53 functions by inhibiting its degradation.
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Affiliation(s)
- G Asher
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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1324
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1325
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Regulation of p53 stability and p53-dependent apoptosis by NADH quinone oxidoreductase 1. Proc Natl Acad Sci U S A 2001. [PMID: 11158615 PMCID: PMC14730 DOI: 10.1073/pnas.021558898] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The tumor suppressor gene wild-type p53 encodes a labile protein that accumulates in cells after different stress signals and can cause either growth arrest or apoptosis. One of the p53 target genes, p53-inducible gene 3 (PIG3), encodes a protein with significant homology to oxidoreductases, enzymes involved in cellular responses to oxidative stress and irradiation. This fact raised the possibility that cellular oxidation-reduction events controlled by such enzymes also may regulate the level of p53. Here we show that NADH quinone oxidoreductase 1 (NQO1) regulates p53 stability. The NQO1 inhibitor dicoumarol caused a reduction in the level of both endogenous and gamma-irradiation-induced p53 in HCT116 human colon carcinoma cells. This reduction was prevented by the proteasome inhibitors MG132 and lactacystin, suggesting enhanced p53 degradation in the presence of dicoumarol. Dicoumarol-induced degradation of p53 also was prevented in the presence of simian virus 40 large T antigen, which is known to bind and to stabilize p53. Cells overexpressing NQO1 were resistant to dicoumarol, and this finding indicates the direct involvement of NQO1 in p53 stabilization. NQO1 inhibition induced p53 degradation and blocked wild-type p53-mediated apoptosis in gamma-irradiated normal thymocytes and in M1 myeloid leukemic cells that overexpress wild-type p53. Dicoumarol also reduced the level of p53 in its mutant form in M1 cells. The results indicate that NQO1 plays an important role in regulating p53 functions by inhibiting its degradation.
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1326
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Foley PA, Luckinbill LS. THE EFFECTS OF SELECTION FOR LARVAL BEHAVIOR ON ADULT LIFE-HISTORY FEATURES IN DROSOPHILA MELANOGASTER. Evolution 2001. [DOI: 10.1554/0014-3820(2001)055[2493:teosfl]2.0.co;2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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1327
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Metzler DE, Metzler CM, Sauke DJ. Growth and Development. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50035-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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1328
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Shore D. The Sir2 protein family: A novel deacetylase for gene silencing and more. Proc Natl Acad Sci U S A 2000; 97:14030-2. [PMID: 11114164 PMCID: PMC34090 DOI: 10.1073/pnas.011506198] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- D Shore
- Department of Molecular Biology, University of Geneva, CH-1211 Geneva, Switzerland
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1329
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Tanner KG, Landry J, Sternglanz R, Denu JM. Silent information regulator 2 family of NAD- dependent histone/protein deacetylases generates a unique product, 1-O-acetyl-ADP-ribose. Proc Natl Acad Sci U S A 2000; 97:14178-82. [PMID: 11106374 PMCID: PMC18891 DOI: 10.1073/pnas.250422697] [Citation(s) in RCA: 437] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Conflicting reports have suggested that the silent information regulator 2 (SIR2) protein family employs NAD(+) to ADP-ribosylate histones [Tanny, J. C., Dowd, G. J., Huang, J., Hilz, H. & Moazed, D. (1999) Cell 99, 735-745; Frye, R. A. (1999) Biochem. Biophys. Res. Commun. 260, 273-279], deacetylate histones [Landry, J., Sutton, A., Tafrov, S. T., Heller, R. C., Stebbins, J., Pillus, L. & Sternglanz, R. (2000) Proc. Natl. Acad. Sci. USA 97, 5807-5811; Smith, J. S., Brachmann, C. B., Celic, I., Kenna, M. A., Muhammad, S., Starai, V. J., Avalos, J. L., Escalante-Semerena, J. C., Grubmeyer, C., Wolberger, C. & Boeke, J. D. (2000) Proc. Natl. Acad. Sci. USA 97, 6658-6663], or both [Imai, S., Armstrong, C. M., Kaeberlein, M. & Guarente, L. (2000) Nature (London) 403, 795-800]. Uncovering the true enzymatic function of SIR2 is critical to the basic understanding of its cellular function. Therefore, we set out to authenticate the reaction products and to determine the intrinsic catalytic mechanism. We provide direct evidence that the efficient histone/protein deacetylase reaction is tightly coupled to the formation of a previously unidentified acetyl-ADP-ribose product (1-O-acetyl-ADP ribose). One molecule of NAD(+) and one molecule of acetyl-lysine are readily catalyzed to one molecule of deacetylated lysine, nicotinamide, and 1-O-acetyl-ADP-ribose. A unique reaction mechanism involving the attack of enzyme-bound acetate or the direct attack of acetyl-lysine on an oxocarbenium ADP-ribose intermediate is proposed. We suggest that the reported histone/protein ADP-ribosyltransferase activity is a low-efficiency side reaction that can be explained through the partial uncoupling of the intrinsic deacetylation and acetate transfer to ADP-ribose.
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Affiliation(s)
- K G Tanner
- Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland, OR 97201-3098, USA
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1330
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Bernstein BE, Tong JK, Schreiber SL. Genomewide studies of histone deacetylase function in yeast. Proc Natl Acad Sci U S A 2000; 97:13708-13. [PMID: 11095743 PMCID: PMC17640 DOI: 10.1073/pnas.250477697] [Citation(s) in RCA: 342] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The trichostatin A (TSA)-sensitive histone deacetylase (HDAC) Rpd3p exists in a complex with Sin3p and Sap30p in yeast that is recruited to target promoters by transcription factors including Ume6p. Sir2p is a TSA-resistant HDAC that mediates yeast silencing. The transcription profile of rpd3 is similar to the profiles of sin3, sap30, ume6, and TSA-treated wild-type yeast. A Ume6p-binding site was identified in the promoters of genes up-regulated in the sin3 strain. Two genes appear to participate in feedback loops that modulate HDAC activity: ZRT1 encodes a zinc transporter and is repressed by RPD3 (Rpd3p is zinc-dependent); BNA1 encodes a nicotinamide adenine dinucleotide (NAD)-biosynthesis enzyme and is repressed by SIR2 (Sir2p is NAD-dependent). Although HDACs are transcriptional repressors, deletion of RPD3 down-regulates certain genes. Many of these are down-regulated rapidly by TSA, indicating that Rpd3p may also activate transcription. Deletion of RPD3 previously has been shown to repress ("silence") reporter genes inserted near telomeres. The profiles demonstrate that 40% of endogenous genes located within 20 kb of telomeres are down-regulated by RPD3 deletion. Rpd3p appears to activate telomeric genes sensitive to histone depletion indirectly by repressing transcription of histone genes. Rpd3p also appears to activate telomeric genes repressed by the silent information regulator (SIR) proteins directly, possibly by deacetylating lysine 12 of histone H4. Finally, bioinformatic analyses indicate that the yeast HDACs RPD3, SIR2, and HDA1 play distinct roles in regulating genes involved in cell cycle progression, amino acid biosynthesis, and carbohydrate transport and utilization, respectively.
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Affiliation(s)
- B E Bernstein
- Howard Hughes Medical Institute, Department of Chemistry and Chemical Biology and Center for Genomics Research, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
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1331
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Abstract
Searches for genes involved in the ageing process have been made in genetically tractable model organisms such as yeast, the nematode Caenorhabditis elegans, Drosophila melanogaster fruitflies and mice. These genetic studies have established that ageing is indeed regulated by specific genes, and have allowed an analysis of the pathways involved, linking physiology, signal transduction and gene regulation. Intriguing similarities in the phenotypes of many of these mutants indicate that the mutations may also perturb regulatory systems that control ageing in higher organisms.
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Affiliation(s)
- L Guarente
- Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA
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