351
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Kang H, Jung JW, Kim MK, Chung JH. CK2 is the regulator of SIRT1 substrate-binding affinity, deacetylase activity and cellular response to DNA-damage. PLoS One 2009; 4:e6611. [PMID: 19680552 PMCID: PMC2721681 DOI: 10.1371/journal.pone.0006611] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Accepted: 07/06/2009] [Indexed: 01/01/2023] Open
Abstract
SIRT1, an NAD(+) (nicotinamide adenine dinucleotide)-dependent deacetylase, protects cells from stress-induced apoptosis, and its orthologues delay aging in lower eukaryotes. SIRT1 increases survival in response to stress such as DNA damage by deacetylating a number of substrates including pro-apoptotic protein p53. The molecular mechanism by which DNA-damage activates SIRT1 is not known. By screening a kinase inhibitor library, we identified CK2 as a SIRT1 kinase. CK2 is a pleiotropic kinase with more than 300 substrates and well-known anti-apoptotic and pro-growth activities. We find that CK2 is recruited to SIRT1 after ionizing radiation (IR) and phosphorylates conserved residues Ser 154, 649, 651 and 683 in the N- and C-terminal domains of mouse SIRT1. Phosphorylation of SIRT1 increases its deacetylation rate but not if the four Ser residues are mutated. In addition, phosphorylation of SIRT1 increases its substrate-binding affinity. CK2-mediated phosphorylation increases the ability of SIRT1 to deacetylate p53 and protect cells from apoptosis after DNA damage. Based on these findings, we propose that CK2 protects against IR-induced apoptosis partly by phosphorylating and activating SIRT1. Thus, this work suggests that SIRT1 is a component of the expansive anti-apoptotic network controlled by CK2. Since expression of both CK2 and SIRT1 is upregulated with tumorigenesis and downregulated with senescence, the CK2-SIRT1 link sheds new light on how CK2 may regulate cancer development and aging.
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Affiliation(s)
- Hyeog Kang
- Laboratory of Biochemical Genetics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jae-Won Jung
- Laboratory of Biochemical Genetics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Myung K. Kim
- Laboratory of Biochemical Genetics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jay H. Chung
- Laboratory of Biochemical Genetics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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352
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Finkel T, Deng CX, Mostoslavsky R. Recent progress in the biology and physiology of sirtuins. Nature 2009; 460:587-91. [PMID: 19641587 DOI: 10.1038/nature08197] [Citation(s) in RCA: 1172] [Impact Index Per Article: 78.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The sirtuins are a highly conserved family of NAD(+)-dependent enzymes that regulate lifespan in lower organisms. Recently, the mammalian sirtuins have been connected to an ever widening circle of activities that encompass cellular stress resistance, genomic stability, tumorigenesis and energy metabolism. Here we review the recent progress in sirtuin biology, the role these proteins have in various age-related diseases and the tantalizing notion that the activity of this family of enzymes somehow regulates how long we live.
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Affiliation(s)
- Toren Finkel
- Translational Medicine Branch, National Heart Lung and Blood Institute, US National Institutes of Health, Bethesda, Maryland 20892, USA
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353
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Smith BC, Hallows WC, Denu JM. A continuous microplate assay for sirtuins and nicotinamide-producing enzymes. Anal Biochem 2009; 394:101-9. [PMID: 19615966 DOI: 10.1016/j.ab.2009.07.019] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 07/07/2009] [Accepted: 07/13/2009] [Indexed: 11/28/2022]
Abstract
Nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylases (sirtuins) and other enzymes that produce nicotinamide are integral to many cellular processes. Yet current activity measurements involve expensive and time-consuming assays. Here we present a spectroscopic assay that circumvents many issues of previous methods. This assay permits continuous product monitoring over time, allows determination of steady-state kinetic parameters, and is readily adaptable to high-throughput screening. The methodology uses an enzyme-coupled system in which nicotinamide is converted to nicotinic acid and ammonia by nicotinamidase. The ammonia is transferred to alpha-ketoglutarate via glutamate dehydrogenase, yielding glutamate and the oxidation of NAD(P)H to NAD(P)+, which is measured spectrophotometrically at 340 nm. Using this continuous assay with sirtuin-1 (Sirt1) and the ADP-ribosyl cyclase CD38, the resulting steady-state kinetic parameters are in excellent agreement with values obtained by other published methods. Importantly, this assay permitted determination of k(cat) and K(m) values with the native acetylated substrate acetyl-CoA synthetase-1; measurement of Sirt1, Sirt2, and Sirt3 activities from mammalian cell extracts; and determination of IC(50) values of various Sirt1 inhibitors. This assay is applicable to any nicotinamide-forming enzyme and will be an important tool to address many outstanding questions surrounding their regulation.
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Affiliation(s)
- Brian C Smith
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
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354
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SirT1 knockdown in liver decreases basal hepatic glucose production and increases hepatic insulin responsiveness in diabetic rats. Proc Natl Acad Sci U S A 2009; 106:11288-93. [PMID: 19549853 DOI: 10.1073/pnas.0812931106] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Hepatic gluconeogenesis is a major contributing factor to hyperglycemia in the fasting and postprandial states in type 2 diabetes mellitus (T2DM). Because Sirtuin 1 (SirT1) induces hepatic gluconeogenesis during fasting through the induction of phosphoenolpyruvate carboxylase kinase (PEPCK), fructose-1,6-bisphosphatase (FBPase), and glucose-6-phosphatase (G6Pase) gene transcription, we hypothesized that reducing SirT1, by using an antisense oligonucleotide (ASO), would decrease fasting hyperglycemia in a rat model of T2DM. SirT1 ASO lowered both fasting glucose concentration and hepatic glucose production in the T2DM rat model. Whole body insulin sensitivity was also increased in the SirT1 ASO treated rats as reflected by a 25% increase in the glucose infusion rate required to maintain euglycemia during the hyperinsulinemic-euglycemic clamp and could entirely be attributed to increased suppression of hepatic glucose production by insulin. The reduction in basal and clamped rates of glucose production could in turn be attributed to decreased expression of PEPCK, FBPase, and G6Pase due to increased acetylation of signal transducer and activator of transcription 3 (STAT3), forkhead box O1 (FOXO1), and peroxisome proliferator-activated receptor-gamma coactivator 1alpha (PGC-1alpha), known substrates of SirT1. In addition to the effects on glucose metabolism, SirT1 ASO decreased plasma total cholesterol, which was attributed to increased cholesterol uptake and export from the liver. These results indicate that inhibition of hepatic SirT1 may be an attractive approach for treatment of T2DM.
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355
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Abstract
The principal tumour-suppressor protein, p53, accumulates in cells in response to DNA damage, oncogene activation and other stresses. It acts as a nuclear transcription factor that transactivates genes involved in apoptosis, cell cycle regulation and numerous other processes. An emerging area of research unravels additional activities of p53 in the cytoplasm, where it triggers apoptosis and inhibits autophagy. These previously unknown functions contribute to the mission of p53 as a tumour suppressor.
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356
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Cha EJ, Noh SJ, Kwon KS, Kim CY, Park BH, Park HS, Lee H, Chung MJ, Kang MJ, Lee DG, Moon WS, Jang KY. Expression of DBC1 and SIRT1 is associated with poor prognosis of gastric carcinoma. Clin Cancer Res 2009; 15:4453-9. [PMID: 19509139 DOI: 10.1158/1078-0432.ccr-08-3329] [Citation(s) in RCA: 157] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE SIRT1 (silent mating-type information regulation 2 homologue 1) expression has been reported to predict poor survival in some cancers. We therefore investigated the expression levels of SIRT1 and its negative regulator, DBC1 (deleted in breast cancer 1), in gastric cancer patients. EXPERIMENTAL DESIGN We evaluated immunohistochemical expression of DBC1, SIRT1, and p53 using 3-mm tumor cores from 177 gastric cancer patients for tissue microarray. RESULTS Positive expressions of DBC1 and SIRT1 were seen in 62% (109 of 177) and in 73% (130 of 177) of patients, respectively. Expression of DBC1 was significantly correlated with tumor stage (P = 0.007), lymph node metastasis (P < 0.001), tumor invasion (P = 0.001), venous invasion (P = 0.001), histologic types (P < 0.001), p53 expression (P < 0.001), and SIRT1 expression (P < 0.001). SIRT1 expression was also significantly correlated with tumor stage (P < 0.001), lymph node metastasis (P < 0.001), tumor invasion (P < 0.001), histologic types (P < 0.001), and p53 expression (P = 0.001). In addition, expression of DBC1 was significantly associated with shorter overall survival and relapse-free survival by univariate analysis (P < 0.001 and P < 0.001, respectively). SIRT1 expression was also significantly associated with shorter overall survival and relapse-free survival by univariate analysis (P = 0.001 and P = 0.001, respectively). Multivariate analysis showed that tumor stage and expression of DBC1 were independent prognostic factors significantly associated with overall survival and relapse-free survival. CONCLUSION This study shows that expression of DBC1 and SIRT1 is a significant prognostic indicator for gastric carcinoma patients.
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Affiliation(s)
- Eun Jung Cha
- Departments of Pathology, Research Institute of Clinical Medicine and Institute for Medical Sciences, Chonbuk National University Medical School, Jeonju, Jeonbuk, Republic of Korea
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357
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Abstract
The traditional view of p53 activation includes three steps-p53 stabilization, DNA binding, and transcriptional activation. However, recent studies indicate that each step of p53 activation is more complex than originally anticipated. Moreover, both genetic studies in mice and in vitro studies with purified components suggest that the classical model may not be sufficient to explain all aspects of p53 activation in vivo. To reconcile these differences, we propose that antirepression, the release of p53 from repression by factors such as Mdm2 and MdmX, is a key step in the physiological activation of p53.
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Affiliation(s)
- Jan-Philipp Kruse
- Institute for Cancer Genetics, College of Physicians and Surgeons, Columbia University, 1130 St. Nicholas Avenue, New York, NY 10032, USA
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358
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Elsheikh SE, Green AR, Rakha EA, Powe DG, Ahmed RA, Collins HM, Soria D, Garibaldi JM, Paish CE, Ammar AA, Grainge MJ, Ball GR, Abdelghany MK, Martinez-Pomares L, Heery DM, Ellis IO. Global histone modifications in breast cancer correlate with tumor phenotypes, prognostic factors, and patient outcome. Cancer Res 2009; 69:3802-9. [PMID: 19366799 DOI: 10.1158/0008-5472.can-08-3907] [Citation(s) in RCA: 310] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Post-translational histone modifications are known to be altered in cancer cells, and loss of selected histone acetylation and methylation marks has recently been shown to predict patient outcome in human carcinoma. Immunohistochemistry was used to detect a series of histone lysine acetylation (H3K9ac, H3K18ac, H4K12ac, and H4K16ac), lysine methylation (H3K4me2 and H4K20me3), and arginine methylation (H4R3me2) marks in a well-characterized series of human breast carcinomas (n = 880). Tissue staining intensities were assessed using blinded semiquantitative scoring. Validation studies were done using immunofluorescence staining and Western blotting. Our analyses revealed low or absent H4K16ac in the majority of breast cancer cases (78.9%), suggesting that this alteration may represent an early sign of breast cancer. There was a highly significant correlation between histone modifications status, tumor biomarker phenotype, and clinical outcome, where high relative levels of global histone acetylation and methylation were associated with a favorable prognosis and detected almost exclusively in luminal-like breast tumors (93%). Moderate to low levels of lysine acetylation (H3K9ac, H3K18ac, and H4K12ac), lysine (H3K4me2 and H4K20me3), and arginine methylation (H4R3me2) were observed in carcinomas of poorer prognostic subtypes, including basal carcinomas and HER-2-positive tumors. Clustering analysis identified three groups of histone displaying distinct pattern in breast cancer, which have distinct relationships to known prognostic factors and clinical outcome. This study identifies the presence of variations in global levels of histone marks in different grades, morphologic types, and phenotype classes of invasive breast cancer and shows that these differences have clinical significance.
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Affiliation(s)
- Somaia E Elsheikh
- Department of Histopathology, School of Molecular Medical Sciences, University of Nottingham and Nottingham Universities Hospital Trust, University of Nottingham, Nottingham, United Kingdom
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359
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Abstract
PURPOSE OF REVIEW Peroxisome proliferator-activated receptor gamma coactivator-1-alpha (PGC-1alpha) has been extensively described as a master regulator of mitochondrial biogenesis. However, PGC-1alpha activity is not constant and can be finely tuned in response to different metabolic situations. From this point of view, PGC-1alpha could be described as a mediator of the transcriptional outputs triggered by metabolic sensors, providing the idea that these sensors, together with PGC-1alpha, might be weaving a network controlling cellular energy expenditure. In this review, we will focus on how disorders such as type 2 diabetes and the metabolic syndrome might be related to an abnormal and improper function of this network. RECENT FINDINGS Two metabolic sensors, AMP-activated protein kinase (AMPK) and SIRT1 have been described to directly affect PGC-1alpha activity through phosphorylation and deacetylation, respectively. Although the physiological relevance of these modifications and their molecular consequences are still largely unknown, recent insight from different in-vivo transgenic models clearly suggests that AMPK, SIRT1 and PGC-1alpha might act as an orchestrated network to improve metabolic fitness. SUMMARY Metabolic sensors such as AMPK and SIRT1, gatekeepers of the activity of the master regulator of mitochondria, PGC-1alpha, are vital links in a regulatory network for metabolic homeostasis. Together, these players explain many of the beneficial effects of physical activity and dietary interventions in our battle against type 2 diabetes and related metabolic disorders. Hence, understanding the mechanisms by which they act could guide us to identify and improve preventive and therapeutic strategies for metabolic diseases.
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Affiliation(s)
- Carles Cantó
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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360
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Fu J, Jiang J, Li J, Wang S, Shi G, Feng Q, White E, Qin J, Wong J. Deleted in breast cancer 1, a novel androgen receptor (AR) coactivator that promotes AR DNA-binding activity. J Biol Chem 2009; 284:6832-40. [PMID: 19126541 PMCID: PMC2652261 DOI: 10.1074/jbc.m808988200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Revised: 12/29/2008] [Indexed: 01/13/2023] Open
Abstract
Androgen receptor (AR) plays a critical role in development and maintenance of male reproductive functions and the etiology of prostate cancer. As a ligand-regulated transcription factor, identification and characterization of AR coregulators are essential for understanding the molecular mechanisms underlying its diverse biological functions. Here we reported the identification of a novel AR coactivator, deleted in breast cancer 1 (DBC1), through a biochemical approach. DBC1 interacts with AR in a ligand-stimulated manner and facilitates AR transcriptional activation in transfected cells as well as in Xenopus oocytes. In in vitro gel shift experiments, recombinant DBC1 drastically enhanced AR DNA-binding activity. Expression of DBC1 also enhanced the binding of AR to chromatinized template in vivo, whereas knockdown of DBC1 impaired the binding of AR to endogenous prostate-specific antigen (PSA) gene in the prostate cancer cell line LNCaP. Thus, our data identify DBC1 as a novel AR coactivator.
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Affiliation(s)
- Junjiang Fu
- The Institute of Biomedical Sciences, College of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China
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361
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Zhang LJ, Liu X, Gafken PR, Kioussi C, Leid M. A chicken ovalbumin upstream promoter transcription factor I (COUP-TFI) complex represses expression of the gene encoding tumor necrosis factor alpha-induced protein 8 (TNFAIP8). J Biol Chem 2009; 284:6156-68. [PMID: 19112178 PMCID: PMC2649093 DOI: 10.1074/jbc.m807713200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Revised: 12/04/2008] [Indexed: 11/06/2022] Open
Abstract
The orphan nuclear receptor chicken ovalbumin upstream promoter transcription factor I (COUP-TFI) plays key roles in development and homeostasis. A tandem affinity purification procedure revealed that COUP-TFI associated with a number of transcriptional regulatory proteins in HeLa S3 cells, including the nuclear receptor corepressor (NCoR), TIF1beta/KAP-1, HDAC1, and the SWI/SNF family member Brahma. The proapoptotic protein DBC1 was also identified in COUP-TFI complexes. In vitro experiments revealed that COUP-TFI interacted directly with NCoR but in a manner different from that of other nuclear receptors. DBC1 stabilized the interaction between COUP-TFI and NCoR by interacting directly with both proteins. The gene encoding the anti-apoptotic protein TNFAIP8 (tumor necrosis factor alpha (TNFalpha)-induced protein 8) was identified as being repressed by COUP-TFI in a manner that required several of the component proteins of the COUP-TFI complex. Finally, our studies highlight a central role for COUP-TFI in the induction of the TNFAIP8 promoter by TNFalpha. Together, these studies identify a novel COUP-TFI complex that functions as a repressor of transcription and may play a role in the TNFalpha signaling pathways.
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Affiliation(s)
- Ling-juan Zhang
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon 97331, USA
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362
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Liu T, Liu PY, Marshall GM. The critical role of the class III histone deacetylase SIRT1 in cancer. Cancer Res 2009; 69:1702-5. [PMID: 19244112 DOI: 10.1158/0008-5472.can-08-3365] [Citation(s) in RCA: 295] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Gene expression and deacetylase activity of the class III histone deacetylase SIRT1 are up-regulated in cancer cells due to oncogene overexpression or loss of function of tumor suppressor genes. SIRT1 induces histone deacetylation and methylation, promoter CpG island methylation, transcriptional repression, and deacetylation of tumor suppressor proteins. SIRT1 may play a critical role in tumor initiation, progression, and drug resistance by blocking senescence and apoptosis, and promoting cell growth and angiogenesis. SIRT1 inhibitors have shown promising anticancer effects in animal models of cancer. Further screening for more potent SIRT1 inhibitors may lead to compounds suitable for clinical trials in patients.
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Affiliation(s)
- Tao Liu
- Children's Cancer Institute Australia for Medical Research, Sydney, New South Wales, Australia
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363
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Li Z, Chen L, Kabra N, Wang C, Fang J, Chen J. Inhibition of SUV39H1 methyltransferase activity by DBC1. J Biol Chem 2009; 284:10361-6. [PMID: 19218236 DOI: 10.1074/jbc.m900956200] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SUV39H1 is a histone H3K9-specific methyltransferase important for heterochromatin formation, regulation of gene expression, and induction of senescence in premalignant cells. SUV39H1 forms a complex with SirT1, and its activity is stimulated by SirT1 binding. Here we present evidence that the product of the DBC1 (deleted in breast cancer 1) gene disrupts the SUV39H1-SirT1 complex. Furthermore, DBC1 binds to the SUV39H1 catalytic domain and inhibits its ability to methylate histone H3 in vitro and in vivo. Knockdown of endogenous DBC1 increased the level of cellular H3K9 methylation. As expected, DBC1 also binds to SirT1 and inhibits the deacetylase activity of SirT1. These results identify DBC1 as a novel cellular inhibitor of SUV39H1 activity. DBC1 may be an important regulator of heterochromatin formation and genomic stability by disrupting the SUV39H1-SirT1 complex and inactivating both enzymes.
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Affiliation(s)
- Zhenyu Li
- Department of Molecular Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, USA
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364
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hSirT1-dependent regulation of the PCAF-E2F1-p73 apoptotic pathway in response to DNA damage. Mol Cell Biol 2009; 29:1989-98. [PMID: 19188449 DOI: 10.1128/mcb.00552-08] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The NAD(+)-dependent histone deacetylase hSirT1 regulates cell survival and stress responses by inhibiting p53-, NF-kappaB-, and E2F1-dependent transcription. Here we show that the hSirT1/PCAF interaction controls the E2F1/p73 apoptotic pathway. hSirT1 represses E2F1-dependent P1p73 promoter activity in untreated cells and inhibits its activation in response to DNA damage. hSirT1, PCAF, and E2F1 are corecruited in vivo on theP1p73 promoter. hSirT1 deacetylates PCAF in vitro and modulates PCAF acetylation in vivo. In cells exposed to apoptotic DNA damage, nuclear NAD(+) levels decrease and inactivate hSirT1 without altering the hSirT1 interaction with PCAF and hSirT1 binding to the P1p73 promoter. The reactivation of hSirT1 by pyruvate that increases the [NAD(+)]/[NADH] ratio completely abolished the DNA damage-induced activation of TAp73 expression, thus linking the modulation of chromatin-bound hSirT1 deacetylase activity by the intracellular redox state with P1p73 promoter activity. The release of PCAF from hSirT1 repression favors the assembly of transcriptionally active PCAF/E2F1 complexes onto the P1p73 promoter and p53-independent apoptosis. Our results identify hSirT1 and PCAF as potential targets to modulate tumor cell survival and chemoresistance irrespective of p53 status.
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365
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Abstract
SIRT1 is a multifaceted, NAD(+)-dependent protein deacetylase that is involved in a wide variety of cellular processes from cancer to ageing. The function of SIRT1 in cancer is complex: SIRT1 has been shown to have oncogenic properties by downregulating p53 activity, but recent studies indicate that SIRT1 acts as a tumour suppressor in a mutated p53 background, raising intriguing questions regarding its mechanism of action. Here we discuss the current understanding of how SIRT1 functions in light of recent discoveries and propose that the net outcome of the seemingly opposite oncogenic and tumour-suppressive effects of SIRT1 depends on the status of p53.
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Affiliation(s)
- Christopher L Brooks
- Institute for Cancer Genetics and Department of Pathology and Cell Biology, College of Physicians & Surgeons, Columbia University, 1130 St Nicholas Avenue, New York, New York 10032, USA
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366
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Histone acetylation in drug addiction. Semin Cell Dev Biol 2009; 20:387-94. [PMID: 19560043 DOI: 10.1016/j.semcdb.2009.01.005] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Revised: 01/09/2009] [Accepted: 01/13/2009] [Indexed: 11/22/2022]
Abstract
Regulation of chromatin structure through post-translational modifications of histones (e.g., acetylation) has emerged as an important mechanism to translate a variety of environmental stimuli, including drugs of abuse, into specific changes in gene expression. Since alterations in gene expression are thought to contribute to the development and maintenance of the addicted state, recent efforts are aimed at identifying how drugs of abuse alter chromatin structure and the enzymes which regulate it. This review discusses how drugs of abuse alter histone acetylation in brain reward regions, through which enzymes this occurs, and ultimately what role histone acetylation plays in addiction-related behaviors.
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367
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Deng CX. SIRT1, is it a tumor promoter or tumor suppressor? Int J Biol Sci 2009; 5:147-52. [PMID: 19173036 PMCID: PMC2631220 DOI: 10.7150/ijbs.5.147] [Citation(s) in RCA: 248] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Accepted: 01/20/2009] [Indexed: 12/13/2022] Open
Abstract
SIRT1 has been considered as a tumor promoter because of its increased expression in some types of cancers and its role in inactivating proteins that are involved in tumor suppression and DNA damage repair. However, recent studies demonstrated that SIRT1 levels are reduced in some other types of cancers, and that SIRT1 deficiency results in genetic instability and tumorigenesis, while overexpression of SIRT1 attenuates cancer formation in mice heterozygous for tumor suppressor p53 or APC. Here, I review these recent findings and discuss the possibility that activation of SIRT1 both extends lifespan and inhibits cancer formation.
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Affiliation(s)
- Chu-Xia Deng
- Genetics of Development and Disease Branch, 10/9N105, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, MD 20892, USA.
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368
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Abstract
Aging and cancer both occur as a result of accumulated cellular damage, and both are related to the regulation of specific genes in the damage response. Recent research has unveiled connections between the mechanisms of aging and cancer, but how to prevent the development of cancer and increase longevity remain unknown. SIRT1 (the mammalian Sir2), which has NAD(+)-dependent class III histone deacetylase activity, may be a key gene linking the modulation of cancer and aging. SIRT1 has broad biological functions in growth regulation, stress response, tumorigenesis, endocrine signaling, and extended lifespan. Here, we focus on the current knowledge regarding the role of SIRT1 in aging and cancer, and discuss the implications of SIRT1 as a therapeutic target for the optimal balance between anti-aging and anti-cancer activities.
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Affiliation(s)
- Eun-Joo Kim
- Department of Molecular Biology, Dankook University, Gyeonggi-do, Korea
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369
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Garapaty S, Xu CF, Trojer P, Mahajan MA, Neubert TA, Samuels HH. Identification and characterization of a novel nuclear protein complex involved in nuclear hormone receptor-mediated gene regulation. J Biol Chem 2009; 284:7542-52. [PMID: 19131338 DOI: 10.1074/jbc.m805872200] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
NRC/NCoA6 plays an important role in mediating the effects of ligand-bound nuclear hormone receptors as well as other transcription factors. NRC interacting factor 1 (NIF-1) was cloned as a novel factor that interacts in vivo with NRC. Although NIF-1 does not directly interact with nuclear hormone receptors, it enhances activation by nuclear hormone receptors presumably through its interaction with NRC. To further understand the cellular and biological function of NIF-1, we identified NIF-1-associated proteins by in-solution proteolysis followed by mass spectrometry. The identified components revealed factors involved in histone methylation and cell cycle control and include Ash2L, RbBP5, WDR5, HCF-1, DBC-1, and EMSY. Although the NIF-1 complex contains Ash2L, RbBP5, and WDR5, suggesting that the complex might methylate histone H3-Lys-4, we found that the complex contains a H3 methyltransferase activity that modifies a residue other than H3-Lys-4. The identified components form at least two distinctly sized NIF-1 complexes. DBC-1 and EMSY were identified as integral components of an NIF-1 complex of approximately 1.5 MDa and were found to play an important role in the regulation of nuclear receptor-mediated transcription. Stimulation of the Sox9 and HoxA1 genes by retinoic acid receptor-alpha was found to require both DBC-1 and EMSY in addition to NIF-1 for maximal transcriptional activation. Interestingly, NRC was not identified as a component of the NIF-1 complex, suggesting that NIF-1 and NRC do not exist as stable in vitro purified complexes, although the separate NIF-1 and NRC complexes appear to functionally interact in the cell.
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Affiliation(s)
- Shivani Garapaty
- Department of Pharmacology, New York University School of Medicine, New York, New York 10016, USA
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370
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371
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Jiang YY, Wang HJ, Wang J, Tashiro SI, Onodera S, Ikejima T. The Protective Effect of Silibinin Against Mitomycin C–Induced Intrinsic Apoptosis in Human Melanoma A375-S2 Cells. J Pharmacol Sci 2009; 111:137-46. [DOI: 10.1254/jphs.09171fp] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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372
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Opposing effects of sirtuins on neuronal survival: SIRT1-mediated neuroprotection is independent of its deacetylase activity. PLoS One 2008; 3:e4090. [PMID: 19116652 PMCID: PMC2605257 DOI: 10.1371/journal.pone.0004090] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Accepted: 11/27/2008] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Growing evidence suggests that sirtuins, a family of seven distinct NAD-dependent enzymes, are involved in the regulation of neuronal survival. Indeed, SIRT1 has been reported to protect against neuronal death, while SIRT2 promotes neurodegeneration. The effect of SIRTs 3-7 on the regulation of neuronal survival, if any, has yet to be reported. METHODOLOGY AND PRINCIPAL FINDINGS We examined the effect of expressing each of the seven SIRT proteins in healthy cerebellar granule neurons (CGNs) or in neurons induced to die by low potassium (LK) treatment. We report that SIRT1 protects neurons from LK-induced apoptosis, while SIRT2, SIRT3 and SIRT6 induce apoptosis in otherwise healthy neurons. SIRT5 is generally localized to both the nucleus and cytoplasm of CGNs and exerts a protective effect. In a subset of neurons, however, SIRT5 localizes to the mitochondria and in this case it promotes neuronal death. Interestingly, the protective effect of SIRT1 in neurons is not reduced by treatments with nicotinamide or sirtinol, two pharmacological inhibitors of SIRT1. Neuroprotection was also observed with two separate mutant forms of SIRT1, H363Y and H355A, both of which lack deacetylase activity. Furthermore, LK-induced neuronal death was not prevented by resveratrol, a pharmacological activator of SIRT1, at concentrations at which it activates SIRT1. We extended our analysis to HT-22 neuroblastoma cells which can be induced to die by homocysteic acid treatment. While the effects of most of the SIRT proteins were similar to that observed in CGNs, SIRT6 was modestly protective against homocysteic acid toxicity in HT-22 cells. SIRT5 was generally localized in the mitochondria of HT-22 cells and was apoptotic. CONCLUSIONS/SIGNIFICANCE Overall, our study makes three contributions - (a) it represents the first analysis of SIRT3-7 in the regulation of neuronal survival, (b) it shows that neuroprotection by SIRT1 can be mediated by a novel, non-catalytic mechanism, and (c) that subcellular localization may be an important determinant in the effect of SIRT5 on neuronal viability.
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373
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Sasaki T, Maier B, Koclega KD, Chruszcz M, Gluba W, Stukenberg PT, Minor W, Scrable H. Phosphorylation regulates SIRT1 function. PLoS One 2008; 3:e4020. [PMID: 19107194 PMCID: PMC2602979 DOI: 10.1371/journal.pone.0004020] [Citation(s) in RCA: 219] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2008] [Accepted: 11/21/2008] [Indexed: 11/30/2022] Open
Abstract
Background SIR2 is an NAD+-dependent deacetylase [1]–[3] implicated in the regulation of lifespan in species as diverse as yeast [4], worms [5], and flies [6]. We previously reported that the level of SIRT1, the mammalian homologue of SIR2 [7], [8], is coupled to the level of mitotic activity in cells both in vitro and in vivo[9]. Cells from long-lived mice maintained SIRT1 levels of young mice in tissues that undergo continuous cell replacement by proliferating stem cells. Changes in SIRT1 protein level were not associated with changes in mRNA level, suggesting that SIRT1 could be regulated post-transcriptionally. However, other than a recent report on sumoylation [10] and identification of SIRT1 as a nuclear phospho-protein by mass spectrometry [11], post-translational modifications of this important protein have not been reported. Methodology/Principal Findings We identified 13 residues in SIRT1 that are phosphorylated in vivo using mass spectrometry. Dephosphorylation by phosphatases in vitro resulted in decreased NAD+-dependent deacetylase activity. We identified cyclinB/Cdk1 as a cell cycle-dependent kinase that forms a complex with and phosphorylates SIRT1. Mutation of two residues phosphorylated by Cyclin B/Cdk1 (threonine 530 and serine 540) disturbs normal cell cycle progression and fails to rescue proliferation defects in SIRT1-deficient cells [12], [13]. Conclusions/Significance Pharmacological manipulation of SIRT1 activity is currently being tested as a means of extending lifespan in mammals. Treatment of obese mice with resveratrol, a pharmacological activator of SIRT1, modestly but significantly improved longevity and, perhaps more importantly, offered some protection against the development of type 2 diabetes mellitus and metabolic syndrome [14]–[16]. Understanding the endogenous mechanisms that regulate the level and activity of SIRT1, therefore, has obvious relevance to human health and disease. Our results identify phosphorylation by cell cycle dependent kinases as a major mechanism controlling the level and function of this sirtuin and complement recent reports of factors that inhibit [17], [18] and activate [19] SIRT1 by protein-protein interactions.
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Affiliation(s)
- Tsutomu Sasaki
- Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia, United States of America
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia, United States of America
| | - Bernhard Maier
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia, United States of America
| | - Katarzyna D. Koclega
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, Virginia, United States of America
| | - Maksymilian Chruszcz
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, Virginia, United States of America
| | - Wendy Gluba
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia, United States of America
| | - P. Todd Stukenberg
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, United States of America
| | - Wladek Minor
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, Virginia, United States of America
| | - Heidi Scrable
- Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia, United States of America
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia, United States of America
- * E-mail:
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374
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Abstract
Loss of endogenous tumor suppression is a critical step on the road to cancer. In a recent paper in Molecular Cell, Wang and colleagues provide evidence that inactivation of the pivotal BRCA1 tumor suppressor disrupts a safeguard gene network that opposes cell proliferation and cell survival.
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Affiliation(s)
- Jianyuan Luo
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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375
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Smith BC, Hallows WC, Denu JM. Mechanisms and molecular probes of sirtuins. CHEMISTRY & BIOLOGY 2008; 15:1002-13. [PMID: 18940661 PMCID: PMC2626554 DOI: 10.1016/j.chembiol.2008.09.009] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Revised: 09/08/2008] [Accepted: 09/17/2008] [Indexed: 12/12/2022]
Abstract
Sirtuins are critical regulators of many cellular processes, including insulin secretion, the cell cycle, and apoptosis. Sirtuins are associated with a variety of age-associated diseases such as type II diabetes, obesity, and Alzheimer's disease. A thorough understanding of sirtuin chemical mechanisms will aid toward developing novel therapeutics that regulate metabolic disorders and combat associated diseases. In this review, we discuss the unique deacetylase mechanism of sirtuins and how this information might be employed to develop inhibitors and other molecular probes for therapeutic and basic research applications. We also cover physiological regulation of sirtuin activity and how these modes of regulation may be exploited to manipulate sirtuin activity in live cells. Development of molecular probes and drugs that specifically target sirtuins will further understanding of sirtuin biology and potentially afford new treatments of several human diseases.
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Affiliation(s)
- Brian C. Smith
- Department of Biomolecular Chemistry; University of Wisconsin, Medical School; Madison, WI 53706; USA
| | - William C. Hallows
- Department of Biomolecular Chemistry; University of Wisconsin, Medical School; Madison, WI 53706; USA
| | - John M. Denu
- Department of Biomolecular Chemistry; University of Wisconsin, Medical School; Madison, WI 53706; USA
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376
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Abstract
SIRT1 is a nicotinamide adenosine dinucleotide-dependent deacetylase that orchestrates key metabolic adaptations to nutrient deprivation in peripheral tissues. SIRT1 is induced also in the brain by reduced energy intake. However, very little is known about SIRT1 distribution and the biochemical phenotypes of SIRT1-expressing cells in the neuraxis. Unknown are also the brain sites in which SIRT1 is regulated by energy availability and whether these regulations are altered in a genetic model of obesity. To address these issues, we performed in situ hybridization histochemistry analyses and found that Sirt1 mRNA is highly expressed in metabolically relevant sites. These include, but are not limited to, the hypothalamic arcuate, ventromedial, dorsomedial, and paraventricular nuclei and the area postrema and the nucleus of the solitary tract in the hindbrain. Of note, our single-cell reverse transcription-PCR analyses revealed that Sirt1 mRNA is expressed in pro-opiomelanocortin neurons that are critical for normal body weight and glucose homeostasis. We also found that SIRT1 protein levels are restrictedly increased in the hypothalamus in the fasted brain. Of note, we found that this hypothalamic-specific, fasting-induced SIRT1 regulation is altered in leptin-deficient, obese mice. Collectively, our findings establish the distribution of Sirt1 mRNA throughout the neuraxis and suggest a previously unrecognized role of brain SIRT1 in regulating energy homeostasis.
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377
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Wang RH, Sengupta K, Li C, Kim HS, Cao L, Xiao C, Kim S, Xu X, Zheng Y, Chilton B, Jia R, Zheng ZM, Appella E, Wang XW, Ried T, Deng CX. Impaired DNA damage response, genome instability, and tumorigenesis in SIRT1 mutant mice. Cancer Cell 2008; 14:312-23. [PMID: 18835033 PMCID: PMC2643030 DOI: 10.1016/j.ccr.2008.09.001] [Citation(s) in RCA: 606] [Impact Index Per Article: 37.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Revised: 06/13/2008] [Accepted: 09/04/2008] [Indexed: 01/05/2023]
Abstract
In lower eukaryotes, Sir2 serves as a histone deacetylase and is implicated in chromatin silencing, longevity, and genome stability. Here we mutated the Sirt1 gene, a homolog of yeast Sir2, in mice to study its function. We show that a majority of SIRT1 null embryos die between E9.5 and E14.5, displaying altered histone modification, impaired DNA damage response, and reduced ability to repair DNA damage. We demonstrate that Sirt1(+/-);p53(+/-) mice develop tumors in multiple tissues, whereas activation of SIRT1 by resveratrol treatment reduces tumorigenesis. Finally, we show that many human cancers exhibit reduced levels of SIRT1 compared to normal controls. Thus, SIRT1 may act as a tumor suppressor through its role in DNA damage response and genome integrity.
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MESH Headings
- Animals
- Anticarcinogenic Agents/pharmacology
- Cell Cycle/genetics
- Cell Transformation, Neoplastic/drug effects
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- Cell Transformation, Neoplastic/radiation effects
- Cells, Cultured
- Chromosomal Instability
- DNA Damage
- DNA Repair
- Down-Regulation
- Embryo, Mammalian/metabolism
- Embryo, Mammalian/pathology
- Female
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Neoplastic
- Genomic Instability
- Gestational Age
- Heterochromatin/metabolism
- Histones/metabolism
- Humans
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mitosis/genetics
- Mutation
- Neoplasms/enzymology
- Neoplasms/genetics
- Neoplasms/prevention & control
- Resveratrol
- Sirtuin 1
- Sirtuins/analysis
- Sirtuins/deficiency
- Sirtuins/genetics
- Sirtuins/metabolism
- Stilbenes/pharmacology
- Time Factors
- Tumor Suppressor Proteins/deficiency
- Tumor Suppressor Proteins/genetics
- Tumor Suppressor Proteins/metabolism
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Affiliation(s)
- Rui-Hong Wang
- Genetics of Development and Disease Branch, 10/9N105, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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378
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Necdin regulates p53 acetylation via Sirtuin1 to modulate DNA damage response in cortical neurons. J Neurosci 2008; 28:8772-84. [PMID: 18753379 DOI: 10.1523/jneurosci.3052-08.2008] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Sirtuin1 (Sirt1), a mammalian homolog of yeast Sir2, deacetylates the tumor suppressor protein p53 and attenuates p53-mediated cell death. Necdin, a p53-interacting protein expressed predominantly in postmitotic neurons, is a melanoma antigen family protein that promotes neuronal differentiation and survival. In mammals, the necdin gene (Ndn) is maternally imprinted, and mutant mice carrying mutated paternal Ndn show abnormalities of neuronal development. Here we report that necdin regulates the acetylation status of p53 via Sirt1 to suppress p53-dependent apoptosis in postmitotic neurons. Double-immunostaining analysis demonstrated that necdin colocalizes with Sirt1 in postmitotic neurons of mouse embryonic forebrain in vivo. Coimmunoprecipitation and in vitro binding analyses revealed that necdin interacts with both p53 and Sirt1 to potentiate Sirt1-mediated p53 deacetylation by facilitating their association. Primary cortical neurons prepared from paternal Ndn-deficient mice have high p53 acetylation levels and are sensitive to the DNA-damaging compounds camptothecin and hydrogen peroxide. Moreover, DNA transfection per se increases p53 acetylation and apoptosis in paternal Ndn-deficient neurons, whereas small interfering RNA-mediated p53 knockdown completely blocks these changes. However, Sirt1 knockdown increases both acetylated p53 level and apoptosis in wild-type neurons but fails to affect them in paternal Ndn-deficient neurons. In organotypic forebrain slice cultures treated with hydrogen peroxide, p53 is accumulated and colocalized with necdin and Sirt1 in cortical neurons. These results suggest that necdin downregulates p53 acetylation levels by forming a stable complex with p53 and Sirt1 to protect neurons from DNA damage-induced apoptosis.
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379
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Kwon HS, Ott M. The ups and downs of SIRT1. Trends Biochem Sci 2008; 33:517-25. [PMID: 18805010 DOI: 10.1016/j.tibs.2008.08.001] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Revised: 08/13/2008] [Accepted: 08/14/2008] [Indexed: 10/21/2022]
Abstract
Reversible acetylation has emerged as a key post-translational modification of proteins. Although the number of acetylated proteins is rapidly growing, the ways in which protein acetyltransferases and deacetylases connect with extracellular stimuli remain unclear. Recently, a regulatory network has emerged that controls the expression and activity of SIRT1, a mammalian class-III protein deacetylase. SIRT1 is an important regulator of metabolism, senescence, cancer and, possibly, longevity and is connected with crucial stress-responsive signal-transduction pathways. These connections provide important clues about how protein acetylation and deacetylation mediate cellular adaptations to extrinsic stress.
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Affiliation(s)
- Hye-Sook Kwon
- Gladstone Institute of Virology and Immunology, University of California, San Francisco, CA 94158, USA
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380
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Zschoernig B, Mahlknecht U. SIRTUIN 1: regulating the regulator. Biochem Biophys Res Commun 2008; 376:251-5. [PMID: 18774777 DOI: 10.1016/j.bbrc.2008.08.137] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Accepted: 08/26/2008] [Indexed: 10/21/2022]
Abstract
Earlier analyses on the sirtuin family of histone deacetylases and its well-known member SIRT1 had their primary focus mostly on the identification of cellular targets exploring molecular mechanisms and functional networks in the control of metabolic homeostasis, differentiation, apoptosis and cell survival. However, only little is known about the regulation of SIRT1 itself, so far. Presently, SIRT1 is gaining increasing importance in the development of innovative treatment strategies for cancer, neurodegenerative disorders and metabolic disease. Based on differences in their catalytic activities, SIRT1 and the sirtuins in general, are insensitive to the classical class I and II HDAC inhibitors which are increasingly becoming part of treatment regimens for solid tumors and hematological malignancies. In this review we outline recent research advances on the regulation of SIRT1 which may provide the basis for the development of therapeutic inhibitors with improved specificity.
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Affiliation(s)
- Barbara Zschoernig
- Saarland University Medical Center, Department of Internal Medicine, Division of Immunotherapy and Gene Therapy, José Carreras Center for Immunotherapy and Gene Therapy, Kirrberger Strasse, Building 40, D-66421 Homburg/Saar, Germany
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381
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Metoyer CF, Pruitt K. The role of sirtuin proteins in obesity. PATHOPHYSIOLOGY 2008; 15:103-8. [DOI: 10.1016/j.pathophys.2008.04.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Revised: 04/28/2008] [Accepted: 04/29/2008] [Indexed: 01/06/2023] Open
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382
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Tang Y, Zhao W, Chen Y, Zhao Y, Gu W. Acetylation is indispensable for p53 activation. Cell 2008; 133:612-26. [PMID: 18485870 DOI: 10.1016/j.cell.2008.03.025] [Citation(s) in RCA: 642] [Impact Index Per Article: 40.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Revised: 12/24/2007] [Accepted: 03/14/2008] [Indexed: 01/14/2023]
Abstract
The activation of the tumor suppressor p53 facilitates the cellular response to genotoxic stress; however, the p53 response can only be executed if its interaction with its inhibitor Mdm2 is abolished. There have been conflicting reports on the question of whether p53 posttranslational modifications, such as phosphorylation or acetylation, are essential or only play a subtle, fine-tuning role in the p53 response. Thus, it remains unclear whether p53 modification is absolutely required for its activation. We have now identified all major acetylation sites of p53. Although unacetylated p53 retains its ability to induce the p53-Mdm2 feedback loop, loss of acetylation completely abolishes p53-dependent growth arrest and apoptosis. Notably, acetylation of p53 abrogates Mdm2-mediated repression by blocking the recruitment of Mdm2 to p53-responsive promoters, which leads to p53 activation independent of its phosphorylation status. Our study identifies p53 acetylation as an indispensable event that destabilizes the p53-Mdm2 interaction and enables the p53-mediated stress response.
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Affiliation(s)
- Yi Tang
- Institute for Cancer Genetics, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA
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383
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Abstract
The activation of the tumor suppressor p53 facilitates the cellular response to genotoxic stress; however, the p53 response can only be executed if its interaction with its inhibitor Mdm2 is abolished. There have been conflicting reports on the question of whether p53 posttranslational modifications, such as phosphorylation or acetylation, are essential or only play a subtle, fine-tuning role in the p53 response. Thus, it remains unclear whether p53 modification is absolutely required for its activation. We have now identified all major acetylation sites of p53. Although unacetylated p53 retains its ability to induce the p53-Mdm2 feedback loop, loss of acetylation completely abolishes p53-dependent growth arrest and apoptosis. Notably, acetylation of p53 abrogates Mdm2-mediated repression by blocking the recruitment of Mdm2 to p53-responsive promoters, which leads to p53 activation independent of its phosphorylation status. Our study identifies p53 acetylation as an indispensable event that destabilizes the p53-Mdm2 interaction and enables the p53-mediated stress response.
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384
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Transcriptional targets of sirtuins in the coordination of mammalian physiology. Curr Opin Cell Biol 2008; 20:303-9. [PMID: 18468877 DOI: 10.1016/j.ceb.2008.03.012] [Citation(s) in RCA: 167] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 03/20/2008] [Indexed: 01/01/2023]
Abstract
Sirtuins (Sirts) compose a family of NAD(+)-dependent deacetylases and/or ADP-ribosyltransferases, which have been implicated in aging, metabolism, and tolerance to oxidative stress. Many of the biological processes regulated by Sirts result from the adaptation of complex gene-expression programs to the energetic state of the cell, sensed through NAD(+) levels. To that respect, Sirts, and particularly the founding member of the family Sirt1, have emerged as important regulators of transcription, which they modulate both positively and negatively by targeting histones and transcriptional complex regulatory proteins. This review will focus on recent advances that have started deciphering how mammalian Sirts regulate transcriptional networks and thereby control physiology.
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385
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Nerurkar PV, Nerurkar VR. Respected Sir(2): magic target for diabetes. CELLSCIENCE 2008; 4:82-96. [PMID: 20577646 PMCID: PMC2890243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The endless quest for the 'fountain of youth' has led to the discovery of a family of molecules known as sirtuins in humans, or silent mating type information regulator 2 (Sir2) in yeast, which are associated with longevity in yeast, nematodes, drosophila and rodents. Although sirtuins have yet to be proven to delay aging and promote longevity in humans, they promise 'healthy aging', an ideal of modern society. This review emphasizes the role of various sirtuins in maintaining glucose homeostasis, the therapeutic potential of sirtuin modulators in the prevention and treatment of diabetes, and the emerging associations of SIRT genetic polymorphisms with human longevity.
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Affiliation(s)
- Pratibha V Nerurkar
- Laboratory of Metabolic Disorders and Alternative Medicine, Dept. of Molecular Biosciences and Bioengineering (MBBE), CTAHR, University of Hawaii, Honolulu, Hawaii
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386
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Nerurkar PV, Nerurkar VR. Can Sir(2) regulate cancer? CELLSCIENCE 2008; 4:50-56. [PMID: 19750026 PMCID: PMC2741025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Sirtuin activators, including small molecules such as polyphenols and resveratrol, are much desired due to their potential to ameliorate metabolic disorder and delay or prevent aging. In contrast, recent studies demonstrate that targeted silencing of sirtuin 1 (SIRT1) expression or activity by the deleted in breast cancer 1 (DBC1) may be beneficial by promoting p53-induced apoptosis in cancer cells, and by sensitizing cancerous cells to radiation therapy. Negative SIRT1 regulation also alleviates gene-repression associated with fragile X mental retardation syndrome. The targeted activation or inhibition of SIRT1 activity therefore emerges as a critical point of regulation in disease pathogenesis.
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Affiliation(s)
- Pratibha V Nerurkar
- Laboratory of Metabolic Disorders and Alternative Medicine, Dept. of Molecular Biosciences and Bioengineering (MBBE), CTAHR, , University of Hawaii, Honolulu
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387
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Anantharaman V, Aravind L. Analysis of DBC1 and its homologs suggests a potential mechanism for regulation of sirtuin domain deacetylases by NAD metabolites. Cell Cycle 2008; 7:1467-72. [PMID: 18418069 DOI: 10.4161/cc.7.10.5883] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Deleted in Breast Cancer-1 (DBC1) and its paralog CARP-1 are large multi-domain proteins, with a nuclear or perinuclear localization, and a role in promoting apoptosis upon processing by caspases. Recent studies on human DBC1 show that it is a specific inhibitor of the sirtuin-type deacetylase, Sirt1, which deacetylates histones and p53. Using sensitive sequence profile searches and HMM-HMM comparisons we show that the central conserved globular domain present in the DBC1 and it homologs from diverse eukaryotes is a catalytically inactive version of the Nudix hydrolase (MutT) domain. Given that Nudix domains are known to bind nucleoside diphosphate sugars and NAD, we predict that this domain in DBC1 and its homologs binds NAD metabolites such as ADP-ribose. Hence, we propose that DBC1 and its homologs are likely to regulate the activity of SIRT1 or related deacetylases by sensing the soluble products or substrates of the NAD-dependent deacetylation reaction. The complex domain architectures of the members of the DBC1 family, which include fusions to the RNA-binding S1-like domain, the DNA-binding SAP domain and EF-hand domains, suggest that they are likely to function as integrators of distinct regulatory signals including chromatin protein modification, soluble compounds in NAD metabolism, apoptotic stimuli and RNA recognition.
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Affiliation(s)
- Vivek Anantharaman
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20894, USA
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