1
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Nakata Y, Ode H, Kubota M, Kasahara T, Matsuoka K, Sugimoto A, Imahashi M, Yokomaku Y, Iwatani Y. Cellular APOBEC3A deaminase drives mutations in the SARS-CoV-2 genome. Nucleic Acids Res 2023; 51:783-795. [PMID: 36610792 PMCID: PMC9881129 DOI: 10.1093/nar/gkac1238] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 12/07/2022] [Accepted: 12/13/2022] [Indexed: 01/09/2023] Open
Abstract
The number of genetic variations in the SARS-CoV-2 genome has been increasing primarily due to continuous viral mutations. Here, we report that the human APOBEC3A (A3A) cytidine deaminase plays a critical role in the induction of C-to-U substitutions in the SARS-CoV-2 genome. Bioinformatic analysis of the chronological genetic changes in a sequence database indicated that the largest UC-to-UU mutation signature, consistent with APOBEC-recognized nucleotide motifs, was predominant in single-stranded RNA regions of the viral genome. In SARS-CoV-2-infected cells, exogenous expression of A3A but not expression of other APOBEC proteins induced UC-to-UU mutations in viral RNA (vRNA). Additionally, the mutated C bases were often located at the tips in bulge or loop regions in the vRNA secondary structure. Interestingly, A3A mRNA expression was drastically increased by interferons (IFNs) and tumour necrosis factor-α (TNF-α) in epithelial cells derived from the respiratory system, a site of efficient SARS-CoV-2 replication. Moreover, the UC-to-UU mutation rate was increased in SARS-CoV-2 produced from lung epithelial cells treated with IFN-ß and TNF-α, but not from CRISPR/Cas9-based A3A knockout cells. Collectively, these findings demonstrate that A3A is a primary host factor that drives mutations in the SARS-CoV-2 RNA genome via RNA editing.
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Affiliation(s)
- Yoshihiro Nakata
- Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Aichi 460-0001, Japan,Department of AIDS Research, Division of Basic Medicine, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Hirotaka Ode
- Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Aichi 460-0001, Japan
| | - Mai Kubota
- Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Aichi 460-0001, Japan
| | - Takaaki Kasahara
- Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Aichi 460-0001, Japan,Department of Respiratory Medicine, Division of Internal Medicine, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Kazuhiro Matsuoka
- Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Aichi 460-0001, Japan
| | - Atsuko Sugimoto
- Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Aichi 460-0001, Japan
| | - Mayumi Imahashi
- Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Aichi 460-0001, Japan
| | - Yoshiyuki Yokomaku
- Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Aichi 460-0001, Japan
| | - Yasumasa Iwatani
- To whom correspondence should be addressed. Tel: +81 52 951 1111; Fax: +81 52 963 3970;
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Nikolaou KC, Vatandaslar H, Meyer C, Schmid MW, Tuschl T, Stoffel M. The RNA-Binding Protein A1CF Regulates Hepatic Fructose and Glycerol Metabolism via Alternative RNA Splicing. Cell Rep 2020; 29:283-300.e8. [PMID: 31597092 DOI: 10.1016/j.celrep.2019.08.100] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 08/09/2019] [Accepted: 08/29/2019] [Indexed: 01/11/2023] Open
Abstract
The regulation of hepatic gene expression has been extensively studied at the transcriptional level; however, the control of metabolism through posttranscriptional gene regulation by RNA-binding proteins in physiological and disease states is less understood. Here, we report a major role for the hormone-sensitive RNA-binding protein (RBP) APOBEC1 complementation factor (A1CF) in the generation of hepatocyte-specific and alternatively spliced transcripts. Among these transcripts are isoforms for the dominant and high-affinity fructose-metabolizing ketohexokinase C and glycerol kinase, two key metabolic enzymes that are linked to hepatic gluconeogenesis and found to be markedly reduced upon hepatic ablation of A1cf. Consequently, mice lacking A1CF exhibit improved glucose tolerance and are protected from fructose-induced hyperglycemia, hepatic steatosis, and development of obesity. Our results identify a previously unreported function of A1CF as a regulator of alternative splicing of a subset of genes influencing hepatic glucose production through fructose and glycerol metabolism.
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Affiliation(s)
- Kostas C Nikolaou
- Institute of Molecular Health Sciences, ETH Zurich, Otto-Stern-Weg 7, 8093 Zürich, Switzerland
| | - Hasan Vatandaslar
- Institute of Molecular Health Sciences, ETH Zurich, Otto-Stern-Weg 7, 8093 Zürich, Switzerland
| | - Cindy Meyer
- Laboratory of RNA Molecular Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
| | - Marc W Schmid
- MWSchmid GmbH, Möhrlistrasse 25, 8006 Zurich, Switzerland
| | - Thomas Tuschl
- Laboratory of RNA Molecular Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
| | - Markus Stoffel
- Institute of Molecular Health Sciences, ETH Zurich, Otto-Stern-Weg 7, 8093 Zürich, Switzerland; Medical Faculty, University of Zurich, 8091 Zurich, Switzerland.
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3
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Eberhart T, Schönenberger MJ, Walter KM, Charles KN, Faust PL, Kovacs WJ. Peroxisome-Deficiency and HIF-2α Signaling Are Negative Regulators of Ketohexokinase Expression. Front Cell Dev Biol 2020; 8:566. [PMID: 32733884 PMCID: PMC7360681 DOI: 10.3389/fcell.2020.00566] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 06/15/2020] [Indexed: 12/28/2022] Open
Abstract
Ketohexokinase (KHK) is the first and rate-limiting enzyme of fructose metabolism. Expression of the two alternatively spliced KHK isoforms, KHK-A and KHK-C, is tissue-specific and KHK-C is predominantly expressed in liver, kidney and intestine and responsible for the fructose-catabolizing function. While KHK isoform choice has been linked to the development of disorders such as obesity, diabetes, cardiovascular disease and cancer, little is known about the regulation of total KHK expression. In the present study, we investigated how hypoxic signaling influences fructose metabolism in the liver. Hypoxia or von Hippel-Lindau (VHL) tumor suppressor loss leads to the stabilization of hypoxia-inducible factors alpha (HIF-1α and HIF-2α) and the activation of their signaling to mediate adaptive responses. By studying liver-specific Vhl, Vhl/Hif1a, and Vhl/Epas1 knockout mice, we found that KHK expression is suppressed by HIF-2α (encoded by Epas1) but not by HIF-1α signaling on mRNA and protein levels. Reduced KHK levels were accompanied by downregulation of aldolase B (ALDOB) in the livers of Vhl and Vhl/Hif1a knockout mice, further indicating inhibited fructose metabolism. HIF-1α and HIF-2α have both overlapping and distinct target genes but are differentially regulated depending on the cell type and physiologic or pathologic conditions. HIF-2α activation augments peroxisome degradation in mammalian cells by pexophagy and thereby changes lipid composition reminiscent of peroxisomal disorders. We further demonstrated that fructose metabolism is negatively regulated by peroxisome-deficiency in a Pex2 knockout Zellweger mouse model, which lacks functional peroxisomes and is characterized by widespread metabolic dysfunction. Repression of fructolytic genes in Pex2 knockout mice appeared to be independent of PPARα signaling and nutritional status. Interestingly, our results demonstrate that both HIF-2α and peroxisome-deficiency result in downregulation of Khk independent of splicing as both isoforms, Khka as well as Khkc, are significantly downregulated. Hence, our study offers new and unexpected insights into the general regulation of KHK, and therefore fructolysis. We revealed a novel regulatory function of HIF-2α, suggesting that HIF-1α and HIF-2α have tissue-specific opposing roles in the regulation of Khk expression, isoform choice and fructolysis. In addition, we discovered a previously unknown function of peroxisomes in the regulation of fructose metabolism.
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Affiliation(s)
- Tanja Eberhart
- Institute of Molecular Health Sciences, ETH Zürich, Zurich, Switzerland
| | | | | | - Khanichi N. Charles
- Department of Biology, San Diego State University, San Diego, CA, United States
| | - Phyllis L. Faust
- Department of Pathology and Cell Biology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, United States
| | - Werner J. Kovacs
- Institute of Molecular Health Sciences, ETH Zürich, Zurich, Switzerland
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4
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Blanc V, Xie Y, Kennedy S, Riordan JD, Rubin DC, Madison BB, Mills JC, Nadeau JH, Davidson NO. Apobec1 complementation factor (A1CF) and RBM47 interact in tissue-specific regulation of C to U RNA editing in mouse intestine and liver. RNA (NEW YORK, N.Y.) 2019; 25:70-81. [PMID: 30309881 PMCID: PMC6298562 DOI: 10.1261/rna.068395.118] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 10/07/2018] [Indexed: 05/05/2023]
Abstract
Mammalian C to U RNA is mediated by APOBEC1, the catalytic deaminase, together with RNA binding cofactors (including A1CF and RBM47) whose relative physiological requirements are unresolved. Although A1CF complements APOBEC1 for in vitro RNA editing, A1cf-/- mice exhibited no change in apolipoproteinB (apoB) RNA editing, while Rbm47 mutant mice exhibited impaired intestinal RNA editing of apoB as well as other targets. Here we examined the role of A1CF and RBM47 in adult mouse liver and intestine, following deletion of either one or both gene products and also following forced (liver or intestinal) transgenic A1CF expression. There were minimal changes in hepatic and intestinal apoB RNA editing in A1cf-/- mice and no changes in either liver- or intestine-specific A1CF transgenic mice. Rbm47 liver-specific knockout (Rbm47LKO ) mice demonstrated reduced editing in a subset (11 of 20) of RNA targets, including apoB. By contrast, apoB RNA editing was virtually eliminated (<6% activity) in intestine-specific (Rbm47IKO ) mice with only five of 53 targets exhibiting C-to-U RNA editing. Double knockout of A1cf and Rbm47 in liver (ARLKO ) eliminated apoB RNA editing and reduced editing in the majority of other targets, with no changes following adenoviral APOBEC1 administration. Intestinal double knockout mice (ARIKO ) demonstrated further reduced editing (<10% activity) in four of five of the residual APOBEC1 targets identified in ARIKO mice. These data suggest that A1CF and RBM47 each function independently, yet interact in a tissue-specific manner, to regulate the activity and site selection of APOBEC1 dependent C-to-U RNA editing.
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Affiliation(s)
- Valerie Blanc
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63105, USA
| | - Yan Xie
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63105, USA
| | - Susan Kennedy
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63105, USA
| | - Jesse D Riordan
- Pacific Northwest Research Institute, Seattle, Washington 98122, USA
| | - Deborah C Rubin
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63105, USA
| | - Blair B Madison
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63105, USA
| | - Jason C Mills
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63105, USA
| | - Joseph H Nadeau
- Pacific Northwest Research Institute, Seattle, Washington 98122, USA
| | - Nicholas O Davidson
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63105, USA
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5
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Lerner T, Papavasiliou FN, Pecori R. RNA Editors, Cofactors, and mRNA Targets: An Overview of the C-to-U RNA Editing Machinery and Its Implication in Human Disease. Genes (Basel) 2018; 10:E13. [PMID: 30591678 PMCID: PMC6356216 DOI: 10.3390/genes10010013] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 12/10/2018] [Accepted: 12/20/2018] [Indexed: 12/22/2022] Open
Abstract
One of the most prevalent epitranscriptomic modifications is RNA editing. In higher eukaryotes, RNA editing is catalyzed by one of two classes of deaminases: ADAR family enzymes that catalyze A-to-I (read as G) editing, and AID/APOBEC family enzymes that catalyze C-to-U. ADAR-catalyzed deamination has been studied extensively. Here we focus on AID/APOBEC-catalyzed editing, and review the emergent knowledge regarding C-to-U editing consequences in the context of human disease.
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Affiliation(s)
- Taga Lerner
- Division of Immune Diversity, Program in Cancer Immunology, German Cancer Research Centre, 69120 Heidelberg, Germany.
- Division of Biosciences, Uni Heidelberg, 69120 Heidelberg, Germany.
| | - F Nina Papavasiliou
- Division of Immune Diversity, Program in Cancer Immunology, German Cancer Research Centre, 69120 Heidelberg, Germany.
| | - Riccardo Pecori
- Division of Immune Diversity, Program in Cancer Immunology, German Cancer Research Centre, 69120 Heidelberg, Germany.
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6
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Yan X, Li Q, Ni D, Xie Y, He Q, Wan Q, Liu Y, Lyu Z, Mao Z, Zhou Q. Apobec-1 complementation factor regulates cell migration and apoptosis through Dickkopf1 by acting on its 3′ untranslated region in MCF7 cells. Tumour Biol 2017. [DOI: 10.1177/1010428317706218] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Affiliation(s)
- Xin Yan
- The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
- Division of Molecular Nephrology and the Creative Training Center for Undergraduates, The Ministry of Education Key Laboratory of Laboratory Medical Diagnostics, The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Qianyin Li
- Division of Molecular Nephrology and the Creative Training Center for Undergraduates, The Ministry of Education Key Laboratory of Laboratory Medical Diagnostics, The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Dongsheng Ni
- The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
- Division of Molecular Nephrology and the Creative Training Center for Undergraduates, The Ministry of Education Key Laboratory of Laboratory Medical Diagnostics, The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Yajun Xie
- Division of Molecular Nephrology and the Creative Training Center for Undergraduates, The Ministry of Education Key Laboratory of Laboratory Medical Diagnostics, The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Qingling He
- Division of Molecular Nephrology and the Creative Training Center for Undergraduates, The Ministry of Education Key Laboratory of Laboratory Medical Diagnostics, The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Qianya Wan
- Division of Molecular Nephrology and the Creative Training Center for Undergraduates, The Ministry of Education Key Laboratory of Laboratory Medical Diagnostics, The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Yamin Liu
- Division of Molecular Nephrology and the Creative Training Center for Undergraduates, The Ministry of Education Key Laboratory of Laboratory Medical Diagnostics, The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Zhongshi Lyu
- Division of Molecular Nephrology and the Creative Training Center for Undergraduates, The Ministry of Education Key Laboratory of Laboratory Medical Diagnostics, The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Zhaomin Mao
- Division of Molecular Nephrology and the Creative Training Center for Undergraduates, The Ministry of Education Key Laboratory of Laboratory Medical Diagnostics, The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Qin Zhou
- Division of Molecular Nephrology and the Creative Training Center for Undergraduates, The Ministry of Education Key Laboratory of Laboratory Medical Diagnostics, The College of Laboratory Medicine, Chongqing Medical University, Chongqing, China
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7
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Abstract
Apolipoprotein B mRNA Editing Catalytic Polypeptide-like 1 or APOBEC1 was discovered in 1993 as the zinc-dependent cytidine deaminase responsible for the production of an in frame stop codon in apoB mRNA through modification of cytidine at nucleotide position 6666 to uridine. At the time of this discovery there was much speculation concerning the mechanism of base modification RNA editing which has been rekindled by the discovery of multiple C to U RNA editing events in the 3′ UTRs of mRNAs and the finding that other members of the APOBEC family while able to bind RNA, have the biological function of being DNA mutating enzymes. Current research is addressing the mechanism for these nucleotide modification events that appear not to adhere to the mooring sequence-dependent model for APOBEC1 involving the assembly of a multi protein containing editosome. This review will summarize our current understanding of the structure and function of APOBEC proteins and examine how RNA binding to them may be a regulatory mechanism.
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Affiliation(s)
- Harold C Smith
- a University of Rochester, School of Medicine and Dentistry , Department of Biochemistry and Biophysics , Rochester , NY , USA
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8
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Severi F, Conticello SG. Flow-cytometric visualization of C>U mRNA editing reveals the dynamics of the process in live cells. RNA Biol 2016; 12:389-97. [PMID: 25806564 PMCID: PMC4615904 DOI: 10.1080/15476286.2015.1026033] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
APOBEC1 is the catalytic subunit of the complex that edits ApolipoproteinB (ApoB) mRNA, which specifically deaminates cytidine 6666 to uracil in the human transcript. The editing leads to the generation of a stop codon, resulting in the synthesis of a truncated form of ApoB. We have developed a method to quantitatively assay ApoB RNA editing in live cells by using a double fluorescent mCherry-EGFP chimera containing a ∼300bp fragment encompassing the region of ApoB subject to RNA editing. Coexpression of APOBEC1 together with this chimera causes specific RNA editing of the ApoB fragment. The insertion of a stop codon between the mCherry and EGFP thus induces the loss of EGFP fluorescence. Using this method we analyze the dynamics of APOBEC1-dependent RNA editing under various conditions. Namely we show the interplay of APOBEC1 with known interactors (ACF, hnRNP-C1, GRY-RBP) in cells that are RNA editing-proficient (HuH-7) or -deficient (HEK-293T), and the effects of restricted cellular localization of APOBEC1 on the efficiency of the editing. Furthermore, our approach is effective in assaying the induction of RNA editing in Caco-2, a cellular model physiologically capable of ApoB RNA editing.
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Key Words
- ACF, APOBEC1 Complementation Factor
- ADAR, Adenosine Deaminase, RNA-specific
- ADAT, Adenosine Deaminase, tRNA-specific
- AID/APOBECs
- APOBEC1, Apolipoprotein B mRNA editing enzyme, catalytic polypeptide 1
- ApoB, Apolipoprotein B
- EGFP, Enhanced Green Fluorescent Protein
- FACS, Fluorescence activated cell sorting
- FBS, Fetal bovine serum
- GRY-RBP, Glycine-Arginine-Tyrosine-rich RNA-binding protein
- RBM47, RNA binding motif protein 47
- RNA editing
- cds, coding sequence
- cytosine deaminase
- hnRNP-C1, heterogeneous nuclear ribonucleoprotein C1
- lipid metabolism
- mRNA
- post-transcriptional modification
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Affiliation(s)
- Francesco Severi
- a Core Research Laboratory; Istituto Toscano Tumori ; Firenze , Italy
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9
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Prohaska KM, Bennett RP, Salter JD, Smith HC. The multifaceted roles of RNA binding in APOBEC cytidine deaminase functions. WILEY INTERDISCIPLINARY REVIEWS-RNA 2014; 5:493-508. [PMID: 24664896 DOI: 10.1002/wrna.1226] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 02/13/2014] [Accepted: 02/13/2014] [Indexed: 01/06/2023]
Abstract
Cytidine deaminases have important roles in the regulation of nucleoside/deoxynucleoside pools for DNA and RNA synthesis. The APOBEC family of cytidine deaminases (named after the first member of the family that was described, Apolipoprotein B mRNA Editing Catalytic Subunit 1, also known as APOBEC1 or A1) is a fascinating group of mutagenic proteins that use RNA and single-stranded DNA (ssDNA) as substrates for their cytidine or deoxycytidine deaminase activities. APOBEC proteins and base-modification nucleic acid editing have been the subject of numerous publications, reviews, and speculation. These proteins play diverse roles in host cell defense, protecting cells from invading genetic material, enabling the acquired immune response to antigens and changing protein expression at the level of the genetic code in mRNA or DNA. The amazing power these proteins have for interphase cell functions relies on structural and biochemical properties that are beginning to be understood. At the same time, the substrate selectivity of each member in the family and their regulation remains to be elucidated. This review of the APOBEC family will focus on an open question in regulation, namely what role the interactions of these proteins with RNA have in editing substrate recognition or allosteric regulation of DNA mutagenic and host-defense activities.
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10
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Smith HC, Bennett RP, Kizilyer A, McDougall WM, Prohaska KM. Functions and regulation of the APOBEC family of proteins. Semin Cell Dev Biol 2011; 23:258-68. [PMID: 22001110 DOI: 10.1016/j.semcdb.2011.10.004] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 09/30/2011] [Accepted: 10/03/2011] [Indexed: 10/16/2022]
Abstract
APOBEC1 is a cytidine deaminase that edits messenger RNAs and was the first enzyme in the APOBEC family to be functionally characterized. Under appropriate conditions APOBEC1 also deaminates deoxycytidine in single-stranded DNA (ssDNA). The other ten members of the APOBEC family have not been fully characterized however several have deoxycytidine deaminase activity on ssDNAs. Despite the nucleic acid substrate preferences of different APOBEC proteins, a common feature appears to be their intrinsic ability to bind to RNA as well as to ssDNA. RNA binding to APOBEC proteins together with protein-protein interactions, post-translation modifications and subcellular localization serve as biological modulators controlling the DNA mutagenic activity of these potentially genotoxic proteins.
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Affiliation(s)
- Harold C Smith
- Department of Biochemistry and Biophysics, University of Rochester, School of Medicine and Dentistry, Rochester, NY 14642, USA.
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11
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Blanc V, Davidson NO. APOBEC-1-mediated RNA editing. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2011; 2:594-602. [PMID: 20836050 DOI: 10.1002/wsbm.82] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
RNA editing defines a molecular process by which a nucleotide sequence is modified in the RNA transcript and results in an amino acid change in the recoded message from that specified in the gene. We will restrict our attention to the type of RNA editing peculiar to mammals, i.e., nuclear C to U RNA editing. This category of RNA editing contrasts with RNA modifications described in plants, i.e., organellar RNA editing (reviewed in Ref 1). Mammalian RNA editing is genetically and biochemically classified into two groups, namely insertion-deletional and substitutional. Substitutional RNA editing is exclusive to mammals, again with two types reported, namely adenosine to inosine and cytosine to uracil (C to U). This review will examine mammalian C to U RNA editing of apolipoproteinB (apoB) RNA and the role of the catalytic deaminase Apobec-1. We will speculate on the functions of Apobec-1 beyond C to U RNA editing as implied from its ability to bind AU-rich RNAs and discuss evidence that dysregulation of Apobec-1 expression might be associated with carcinogenesis through aberrant RNA editing or altered RNA stability.
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Affiliation(s)
- Valerie Blanc
- Division of Gastroenterology, Washington University School of Medicine, St. Louis, MO 63105, USA
| | - Nicholas O Davidson
- Division of Gastroenterology, Washington University School of Medicine, St. Louis, MO 63105, USA
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12
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Abstract
Substitutional RNA editing represents an important posttranscriptional enzymatic pathway for increasing genetic plasticity by permitting production of different translation products from a single genomically encoded template. One of the best-characterized examples in mammals is C to U deamination of the nuclear apolipoprotein B (apoB) mRNA. ApoB mRNA undergoes a single, site-specific cytidine deamination event yielding an edited transcript that results in tissue-specific translation of two distinct isoforms, referred to as apoB100 and apoB48. Tissue- and site-specific cytidine deamination of apoB mRNA is mediated by an incompletely characterized holoenzyme containing a minimal core complex consisting of an RNA-specific cytidine deaminase, Apobec-1 and a requisite cofactor, apobec-1 complementation factor (ACF). The underlying biochemical and genetic mechanisms regulating tissue-specific apoB mRNA editing have been accelerated through development and characterization of physiological rodent models as well as knockout and transgenic animal strains.
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13
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Galloway CA, Kumar A, Krucinska J, Smith HC. APOBEC-1 complementation factor (ACF) forms RNA-dependent multimers. Biochem Biophys Res Commun 2010; 398:38-43. [PMID: 20541536 DOI: 10.1016/j.bbrc.2010.06.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Accepted: 06/06/2010] [Indexed: 10/19/2022]
Abstract
Limited proteolysis of APOBEC-1 complementation factor (ACF) and computational secondary structure modeling were used to guide the construction of a well-folded, truncation protein spanning residues 1-320 and containing three RNA recognition motifs (RRMs). ACF320 bound preferentially to apoB mRNA and supported APOBEC-1 dependent editing at 40% of the activity of full length ACF. Live cell FRET and immunoprecipitation assays revealed that ACF320 formed homomultimers in situ that were bridged by RNA. Our study predicted that the C to U editosome may be assembled on the mooring sequence of apoB mRNA as a dimer of ACF bound to a dimer of APOBEC-1.
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Affiliation(s)
- C A Galloway
- University of Rochester, School of Medicine and Dentistry, Department of Biochemistry and Biophysics, 601 Elmwood Ave., Rochester, NY 14642, USA
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14
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Galloway CA, Ashton J, Sparks JD, Mooney RA, Smith HC. Metabolic regulation of APOBEC-1 complementation factor trafficking in mouse models of obesity and its positive correlation with the expression of ApoB protein in hepatocytes. Biochim Biophys Acta Mol Basis Dis 2010; 1802:976-85. [PMID: 20541607 DOI: 10.1016/j.bbadis.2010.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 06/03/2010] [Accepted: 06/03/2010] [Indexed: 10/19/2022]
Abstract
APOBEC-1 Complementation Factor (ACF) is an RNA-binding protein that interacts with apoB mRNA to support RNA editing. ACF traffics between the cytoplasm and nucleus. It is retained in the nucleus in response to elevated serum insulin levels where it supports enhanced apoB mRNA editing. In this report we tested whether ACF may have the ability to regulate nuclear export of apoB mRNA to the sites of translation in the cytoplasm. Using mouse models of obesity-induced insulin resistance and primary hepatocyte cultures we demonstrated that both nuclear retention of ACF and apoB mRNA editing were reduced in the livers of hyperinsulinemic obese mice relative to lean controls. Coincident with an increase in the recovery of ACF in the cytoplasm was an increase in the proportion of total cellular apoB mRNA recovered in cytoplasmic extracts. Cytoplasmic ACF from both lean controls and obese mouse livers was enriched in endosomal fractions associated with apoB mRNA translation and ApoB lipoprotein assembly. Inhibition of ACF export to the cytoplasm resulted in nuclear retention of apoB mRNA and reduced both intracellular and secreted ApoB protein in primary hepatocytes. The importance of ACF for modulating ApoB was supported by the finding that RNAi knockdown of ACF reduced ApoB secretion. An additional discovery from this study was the finding that leptin is a suppressor ACF expression. Dyslipidemia is a common pathology associated with insulin resistance that is in part due to the loss of insulin controlled secretion of lipid in ApoB-containing very low density lipoproteins. The data from animal models suggested that loss of insulin regulated ACF trafficking and leptin regulated ACF expression may make an early contribution to the overall pathology associated with very low density lipoprotein secretion from the liver in obese individuals.
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Affiliation(s)
- Chad A Galloway
- University of Rochester, Department of Biochemistry and Biophysics, 601 Elmwood Ave Rochester, NY 14642, USA
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15
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Galloway CA, Smith HC. The expression of apoB mRNA editing factors is not the sole determinant for the induction of editing in differentiating Caco-2 cells. Biochem Biophys Res Commun 2009; 391:659-63. [PMID: 19932086 DOI: 10.1016/j.bbrc.2009.11.116] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Accepted: 11/18/2009] [Indexed: 11/17/2022]
Abstract
Apolipoprotein B mRNA is edited at cytidine 6666 in the enterocytes lining the small intestine of all mammals; converting a CAA codon to a UAA stop codon. The conversion is approximately 80% efficient in this tissue and leads to the expression of the truncated protein, ApoB48, essential for secretion of dietary lipid as chylomicrons. Caco-2 cell raft cultures have been used as an in vitro model for the induction of editing activity during human small intestinal cell differentiation. This induction of apoB mRNA editing has been ascribed to the expression of APOBEC-1. In agreement our data demonstrated differentiation-dependent induction of expression of the editing enzyme APOBEC-1 and in addition we show alternative splicing of the essential auxiliary factor ACF. However, transfection of these editing factors in undifferentiated proliferating Caco-2 cells was not sufficient to induce robust apoB mRNA editing activity. Only differentiation of Caco-2 cells could induce more physiological like levels of apoB mRNA editing. The data suggested that additional regulatory mechanism(s) were induced by differentiation that controlled the functional activity of editing factors.
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Affiliation(s)
- Chad A Galloway
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine, 601 Elmwood Ave, Rochester, NY 14642, USA
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16
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Romani B, Engelbrecht S, Glashoff RH. Antiviral roles of APOBEC proteins against HIV-1 and suppression by Vif. Arch Virol 2009; 154:1579-88. [DOI: 10.1007/s00705-009-0481-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Accepted: 07/22/2009] [Indexed: 01/18/2023]
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17
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Li H, Chen W, Zhou Y, Abidi P, Sharpe O, Robinson WH, Kraemer FB, Liu J. Identification of mRNA binding proteins that regulate the stability of LDL receptor mRNA through AU-rich elements. J Lipid Res 2009; 50:820-31. [PMID: 19141871 DOI: 10.1194/jlr.m800375-jlr200] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 3'untranslated region (UTR) of human LDL receptor (LDLR) mRNA contains three AU-rich elements (AREs) responsible for rapid mRNA turnover and mediates the stabilization induced by berberine (BBR). However, the identities of the specific RNA binding proteins involved in the regulation of LDLR mRNA stability at the steady state level or upon BBR treatment are unknown. By conducting small interfering RNA library screenings, biotinylated RNA pull-down, mass spectrometry analysis, and functional assays, we now identify heterogeneous nuclear ribonucleoprotein D (hnRNP D), hnRNP I, and KH-type splicing regulatory protein (KSRP) as key modulators of LDLR mRNA stability in liver cells. We show that hnRNP D, I, and KSRP interact with AREs of the LDLR 3'UTR with sequence specificity. Silencing the expression of these proteins increased LDLR mRNA and protein levels. We further demonstrate that BBR-induced mRNA stabilization involves hnRNP I and KSRP, as their cellular depletions abolished the BBR effect and BBR treatment reduced the binding of hnRNP I and KSRP to the LDLR mRNA 3'UTR. These new findings demonstrate that LDLR mRNA stability is controlled by a group of ARE binding proteins, including hnRNP D, hnRNP I, and KSRP. Our results suggest that interference with the ability of destabilizing ARE binding proteins to interact with LDLR-ARE motifs is likely a mechanism for regulating LDLR expression by compounds such as BBR and perhaps others.
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Affiliation(s)
- Hai Li
- Department of Veterans Affairs, Palo Alto Health Care System, Palo Alto, CA 94304, USA
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18
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Mattick JS, Mehler MF. RNA editing, DNA recoding and the evolution of human cognition. Trends Neurosci 2008; 31:227-33. [PMID: 18395806 DOI: 10.1016/j.tins.2008.02.003] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 02/10/2008] [Accepted: 02/12/2008] [Indexed: 01/09/2023]
Abstract
RNA editing appears to be the major mechanism by which environmental signals overwrite encoded genetic information to modify gene function and regulation, particularly in the brain. We suggest that the predominance of Alu elements in the human genome is the result of their evolutionary co-adaptation as a modular substrate for RNA editing, driven by selection for higher-order cognitive function. We show that RNA editing alters transcripts from loci encoding proteins involved in neural cell identity, maturation and function, as well as in DNA repair, implying a role for RNA editing not only in neural transmission and network plasticity but also in brain development, and suggesting that communication of productive changes back to the genome might constitute the molecular basis of long-term memory and higher-order cognition.
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Affiliation(s)
- John S Mattick
- ARC Special Research Centre for Functional and Applied Genomics, Institute for Molecular Bioscience, University of Queensland, St. Lucia, QLD 4072, Australia
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19
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Gaston KW, Rubio MAT, Spears JL, Pastar I, Papavasiliou FN, Alfonzo JD. C to U editing at position 32 of the anticodon loop precedes tRNA 5' leader removal in trypanosomatids. Nucleic Acids Res 2007; 35:6740-9. [PMID: 17916576 PMCID: PMC2175311 DOI: 10.1093/nar/gkm745] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In all organisms, precursor tRNAs are processed into mature functional units by post-transcriptional changes. These involve 5′ and 3′ end trimming as well as the addition of a significant number of chemical modifications, including RNA editing. The only known example of non-organellar C to U editing of tRNAs occurs in trypanosomatids. In this system, editing at position 32 of the anticodon loop of tRNAThr(AGU) stimulates, but is not required for, the subsequent formation of inosine at position 34. In the present work, we expand the number of C to U edited tRNAs to include all the threonyl tRNA isoacceptors. Notably, the absence of a naturally encoded adenosine, at position 34, in two of these isoacceptors demonstrates that A to I is not required for C to U editing. We also show that C to U editing is a nuclear event while A to I is cytoplasmic, where C to U editing at position 32 occurs in the precursor tRNA prior to 5′ leader removal. Our data supports the view that C to U editing is more widespread than previously thought and is part of a stepwise process in the maturation of tRNAs in these organisms.
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Affiliation(s)
- Kirk W Gaston
- Department of Microbiology, The Ohio State RNA Group, The Ohio State University, Columbus, Ohio 43210, USA
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20
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Abstract
RNA editing is a process through which the nucleotide sequence specified in the genomic template is modified to produce a different nucleotide sequence in the transcript. RNA editing is an important mechanism of genetic regulation that amplifies genetic plasticity by allowing the production of alternative protein products from a single gene. There are two generic classes of RNA editing in nuclei, involving enzymatic deamination of either C-to-U or A-to-I nucleotides. The best characterized example of C-to-U RNA editing is that of apolipoprotein B (apoB), which is mediated by a holoenzyme that contains a minimal core composed of an RNA-specific cytidine deaminase apobec-1, and its cofactor apobec-1 complementation factor (ACF). C-to-U editing of apoB RNA generates two different isoforms--apoB100 and apoB48--from a single transcript. Both are important regulators of lipid transport and metabolism, and are functionally distinct. C-to-U apoB RNA editing is regulated by a range of factors including developmental, nutritional, environmental, and metabolic stimuli. Rodent models have provided a tractable system in which to study the effects of such stimuli on lipid metabolism. In addition, both transgenic and gene knockout experiments have provided important insights into gain and loss of function approaches for studying C-to-U RNA editing in a murine background.
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Affiliation(s)
- Soo-Jin Cho
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
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21
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Smith HC. Measuring editing activity and identifying cytidine-to-uridine mRNA editing factors in cells and biochemical isolates. Methods Enzymol 2007; 424:389-416. [PMID: 17662851 DOI: 10.1016/s0076-6879(07)24018-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cytidine deaminases with the capacity to act on nucleic acids play a critical role in regulating the proteome through diversification of expressed sequence beyond that encoded in the genome. A family of these enzymes, known as the APOBEC family of cytidine deaminases, has been identified in mammalian cells. APOBEC-1 edits messenger RNA, whereas other family members affect mRNA coding capacity by editing single-stranded DNA in expressed regions of the genomes. Biochemical isolation and analysis of APOBEC proteins and their interacting factors have led to an understanding of the diverse cellular processes including lipoprotein metabolism, antibody production, viral infectivity, and cancer. Practical approaches will be described for the measurement of editing activity and the analysis of proteins involved in C-to-U and dC-to-dU editing.
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Affiliation(s)
- Harold C Smith
- Department of Biochemistry, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
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Lehmann DM, Galloway CA, MacElrevey C, Sowden MP, Wedekind JE, Smith HC. Functional characterization of APOBEC-1 complementation factor phosphorylation sites. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1773:408-18. [PMID: 17229474 PMCID: PMC1847399 DOI: 10.1016/j.bbamcr.2006.11.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2006] [Revised: 11/13/2006] [Accepted: 11/27/2006] [Indexed: 11/17/2022]
Abstract
ApoB mRNA editing involves site-specific deamination of cytidine 6666 producing an in-frame translation stop codon. Editing minimally requires APOBEC-1 and APOBEC-1 complementation factor (ACF). Metabolic stimulation of apoB mRNA editing in hepatocytes is associated with serine phosphorylation of ACF localized to editing competent, nuclear 27S editosomes. We demonstrate that activation of protein kinase C (PKC) stimulated editing and enhanced ACF phosphorylation in rat primary hepatocytes. Conversely, activation of protein kinase A (PKA) had no effect on editing. Recombinant PKC efficiently phosphorylated purified ACF64 protein in vitro, whereas PKA did not. Mutagenesis of predicted PKC phosphorylation sites S154 and S368 to alanine inhibited ethanol-stimulated induction of editing suggesting that these sites function in the metabolic regulation of editing. Consistent with this interpretation, substitution of S154 and S368 with aspartic acid stimulated editing to levels comparable to ethanol treatment in control McArdle RH7777 cells. These data suggest that phosphorylation of ACF by PKC may be a key regulatory mechanism of apoB mRNA editing in rat hepatocytes.
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Affiliation(s)
- David M. Lehmann
- Department of Toxicology, University of Rochester, Rochester, New York 14642
- Environmental Health Sciences Center, University of Rochester, Rochester, New York 14642
| | - Chad A. Galloway
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642
| | - Celeste MacElrevey
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642
| | - Mark P. Sowden
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642
- Department of Pathology and Laboratory Medicine, University of Rochester, Rochester, New York 14642
| | - Joseph E. Wedekind
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642
| | - Harold C. Smith
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642
- Department of Pathology and Laboratory Medicine, University of Rochester, Rochester, New York 14642
- Department of Toxicology, University of Rochester, Rochester, New York 14642
- Environmental Health Sciences Center, University of Rochester, Rochester, New York 14642
- James P. Wilmot Cancer Center, University of Rochester, Rochester, New York 14642
- * Corresponding author: Department of Biochemistry and Biophysics, University of Rochester, 601 Elmwood Ave., Rochester, NY 14642 Tel.: 585-275-4267 FAX: 585-275-6007 E-mail:
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