151
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McLennan AG. Substrate ambiguity among the nudix hydrolases: biologically significant, evolutionary remnant, or both? Cell Mol Life Sci 2013; 70:373-85. [PMID: 23184251 PMCID: PMC11113851 DOI: 10.1007/s00018-012-1210-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 11/01/2012] [Accepted: 11/05/2012] [Indexed: 12/20/2022]
Abstract
Many members of the nudix hydrolase family exhibit considerable substrate multispecificity and ambiguity, which raises significant issues when assessing their functions in vivo and gives rise to errors in database annotation. Several display low antimutator activity when expressed in bacterial tester strains as well as some degree of activity in vitro towards mutagenic, oxidized nucleotides such as 8-oxo-dGTP. However, many of these show greater activity towards other nucleotides such as ADP-ribose or diadenosine tetraphosphate (Ap(4)A). The antimutator activities have tended to gain prominence in the literature, whereas they may in fact represent the residual activity of an ancestral antimutator enzyme that has become secondary to the more recently evolved major activity after gene duplication. Whether any meaningful antimutagenic function has also been retained in vivo requires very careful assessment. Then again, other examples of substrate ambiguity may indicate as yet unexplored regulatory systems. For example, bacterial Ap(4)A hydrolases also efficiently remove pyrophosphate from the 5' termini of mRNAs, suggesting a potential role for Ap(4)A in the control of bacterial mRNA turnover, while the ability of some eukaryotic mRNA decapping enzymes to degrade IDP and dIDP or diphosphoinositol polyphosphates (DIPs) may also be indicative of new regulatory networks in RNA metabolism. DIP phosphohydrolases also degrade diadenosine polyphosphates and inorganic polyphosphates, suggesting further avenues for investigation. This article uses these and other examples to highlight the need for a greater awareness of the possible significance of substrate ambiguity among the nudix hydrolases as well as the need to exert caution when interpreting incomplete analyses.
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Affiliation(s)
- Alexander G McLennan
- Institute of Integrative Biology, University of Liverpool, Biosciences Building, Crown St., Liverpool, L69 7ZB, UK.
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152
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Thran M, Link K, Sonnewald U. The Arabidopsis DCP2 gene is required for proper mRNA turnover and prevents transgene silencing in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 72:368-77. [PMID: 22639932 DOI: 10.1111/j.1365-313x.2012.05066.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Post-transcriptional gene silencing often limits the over-expression of transgenes in transgenic plants. It involves RNA-DEPENDENT RNA POLYMERASE 6 (RDR6), which recognizes aberrant transcripts, such as inaccurately processed or uncapped mRNA, and triggers silencing of target transcripts. Here, we describe the isolation and characterization of an Arabidopsis mutant displaying increased transgene silencing (its1). Reduced accumulation of transgene mRNA in the its1 mutant background was accompanied by accumulation of transgene-specific siRNAs and was overcome by potyvirus infection. We therefore speculated that ITS1 is a suppressor of post-transcriptional gene silencing. Map-based cloning and subsequent complementation revealed that ITS1 encodes DECAPPING 2 (DCP2), which is crucial for decapping, a prerequisite for mRNA degradation. In agreement with the proposed function of DCP2, we found a reduced accumulation of uncapped mRNA in the its1 mutant. Furthermore, silencing in the its1 mutant was dependent on RDR6 function, suggesting that reduced decapping leads to accumulation of aberrant capped mRNA. Hence, we provide evidence for a class of aberrant mRNA that accumulates upon impaired mRNA decapping and triggers post-transcriptional gene silencing in Arabidopsis. As DCP2 knockouts cause post-embryo lethality, we isolated a hypomorphic dcp2 allele, providing insights into mRNA degradation and its interplay with post-transcriptional gene silencing.
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Affiliation(s)
- Moritz Thran
- Department of Biology, Friedrich Alexander University Erlangen-Nuremberg, Staudtstrasse 5, 91058 Erlangen, Germany
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153
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Arif SM, Patil AG, Varshney U, Vijayan M. Crystallization and preliminary X-ray studies of MutT1 (MSMEG_2390) from Mycobacterium smegmatis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2012; 68:1214-6. [PMID: 23027750 PMCID: PMC3497982 DOI: 10.1107/s1744309112035804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 08/14/2012] [Indexed: 11/10/2022]
Abstract
MutT1 (MSMEG_2390) from Mycobacterium smegmatis has been crystallized and the crystals have been characterized using X-ray diffraction. The crystals belonged to space group P2(1)2(1)2(1). The Matthews coefficient suggested the possibility of one protein molecule in the asymmetric unit of the orthorhombic unit cell. Solution of the structure using the known three-dimensional structure of a bacterial MutT1 is anticipated.
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Affiliation(s)
- S. M. Arif
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
| | - A. G. Patil
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560 012, India
| | - U. Varshney
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560 012, India
| | - M. Vijayan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
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154
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Diaz ME, Mayoral JG, Priestap H, Nouzova M, Rivera-Perez C, Noriega FG. Characterization of an isopentenyl diphosphate isomerase involved in the juvenile hormone pathway in Aedes aegypti. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2012; 42:751-7. [PMID: 22782071 PMCID: PMC3438293 DOI: 10.1016/j.ibmb.2012.07.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 05/31/2012] [Accepted: 07/03/2012] [Indexed: 05/21/2023]
Abstract
Isopentenyl diphosphate isomerase (IPPI) is an enzyme involved in the synthesis of juvenile hormone (JH) in the corpora allata (CA) of insects. IPPI catalyzes the conversion of isopentenyl pyrophosphate (IPP) to dimethylallyl pyrophosphate (DMAPP); afterward IPP and DMAPP condense in a head-to-tail manner to produce geranyl diphosphate (GPP), this head-to-tail condensation can be repeated, by the further reaction of GPP with IPP, yielding the JH precursor farnesyl diphosphate. An IPPI expressed sequence tag (EST) was obtained from an Aedes aegypti corpora-allata + corpora cardiaca library. Its full-length cDNA encodes a 244-aa protein that shows a high degree of similarity with type I IPPIs from other organisms, particularly for those residues that have important roles in catalysis, metal coordination and interaction with the diphosphate moiety of the IPP. Heterologous expression produced a recombinant protein that metabolized IPP into DMAPP; treatment of DMAPP with phosphoric acid produced isoprene, a volatile compound that was measured with an assay based on a solid-phase micro extraction protocol and direct analysis by gas chromatography. A. aegypti IPPI (AaIPPI) required Mg(2+) or Mn(2+) but not Zn(2+) for full activity and it was entirely inhibited by iodoacetamide. Real time PCR experiments showed that AaIPPI is highly expressed in the CA. Changes in AaIPPI mRNA levels in the CA in the pupal and adult female mosquito corresponded well with changes in JH synthesis (Li et al., 2003). This is the first molecular and functional characterization of an isopentenyl diphosphate isomerase involved in the production of juvenile hormone in the CA of an insect.
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Affiliation(s)
- Miguel E Diaz
- Department of Biological Sciences, Florida International University, 11200 SW 8th St., Miami, FL 33199, USA
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155
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Synthetic pathway for production of five-carbon alcohols from isopentenyl diphosphate. Appl Environ Microbiol 2012; 78:7849-55. [PMID: 22941086 DOI: 10.1128/aem.01175-12] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Synthetic biological pathways could enhance the development of novel processes to produce chemicals from renewable resources. On the basis of models that describe the evolution of metabolic pathways and enzymes in nature, we developed a framework to rationally identify enzymes able to catalyze reactions on new substrates that overcomes one of the major bottlenecks in the assembly of a synthetic biological pathway. We verified the framework by implementing a pathway with two novel enzymatic reactions to convert isopentenyl diphosphate into 3-methyl-3-butenol, 3-methyl-2-butenol, and 3-methylbutanol. To overcome competition with native pathways that share the same substrate, we engineered two bifunctional enzymes that redirect metabolic flux toward the synthetic pathway. Taken together, our work demonstrates a new approach to the engineering of novel synthetic pathways in the cell.
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156
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Berthelot K, Estevez Y, Deffieux A, Peruch F. Isopentenyl diphosphate isomerase: A checkpoint to isoprenoid biosynthesis. Biochimie 2012; 94:1621-34. [DOI: 10.1016/j.biochi.2012.03.021] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 03/27/2012] [Indexed: 11/25/2022]
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157
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Zhu WW, Wang C, Jipp J, Ferguson L, Lucas SN, Hicks MA, Glasner ME. Residues required for activity in Escherichia coli o-succinylbenzoate synthase (OSBS) are not conserved in all OSBS enzymes. Biochemistry 2012; 51:6171-81. [PMID: 22775324 DOI: 10.1021/bi300753j] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Understanding how enzyme specificity evolves will provide guiding principles for protein engineering and function prediction. The o-succinylbenzoate synthase (OSBS) family is an excellent model system for elucidating these principles because it has many highly divergent amino acid sequences that are <20% identical, and some members have evolved a second function. The OSBS family belongs to the enolase superfamily, members of which use a set of conserved residues to catalyze a wide variety of reactions. These residues are the only conserved residues in the OSBS family, so they are not sufficient to determine reaction specificity. Some enzymes in the OSBS family catalyze another reaction, N-succinylamino acid racemization (NSAR). NSARs cannot be segregated into a separate family because their sequences are highly similar to those of known OSBSs, and many of them have both OSBS and NSAR activities. To determine how such divergent enzymes can catalyze the same reaction and how NSAR activity evolved, we divided the OSBS family into subfamilies and compared the divergence of their active site residues. Correlating sequence conservation with the effects of mutations in Escherichia coli OSBS identified two nonconserved residues (R159 and G288) at which mutations decrease efficiency ≥200-fold. These residues are not conserved in the subfamily that includes NSAR enzymes. The OSBS/NSAR subfamily binds the substrate in a different orientation, eliminating selective pressure to retain arginine and glycine at these positions. This supports the hypothesis that specificity-determining residues have diverged in the OSBS family and provides insight into the sequence changes required for the evolution of NSAR activity.
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Affiliation(s)
- Wan Wen Zhu
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA
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158
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Takagi Y, Setoyama D, Ito R, Kamiya H, Yamagata Y, Sekiguchi M. Human MTH3 (NUDT18) protein hydrolyzes oxidized forms of guanosine and deoxyguanosine diphosphates: comparison with MTH1 and MTH2. J Biol Chem 2012; 287:21541-9. [PMID: 22556419 PMCID: PMC3375575 DOI: 10.1074/jbc.m112.363010] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 04/25/2012] [Indexed: 01/25/2023] Open
Abstract
Most of the proteins carrying the 23-residue MutT-related sequence are capable of hydrolyzing compounds with a general structure of nucleoside diphosphate linked to another moiety X and are called the Nudix hydrolases. Among the 22 human Nudix proteins (identified by the sequence signature), some remain uncharacterized as enzymes without a defined substrate. Here, we reveal that the NUDT18 protein, whose substrate was unknown, can degrade 8-oxo-7,8-dihydroguanine (8-oxo-Gua)-containing nucleoside diphosphates to the monophosphates. Because this enzyme is closely related to MTH1 (NUDT1) and MTH2 (NUDT15), we propose that it should be named MTH3. Although these three human proteins resemble each other in their sequences, their substrate specificities differ considerably. MTH1 cleaves 8-oxo-dGTP but not 8-oxo-dGDP, whereas MTH2 can degrade both 8-oxo-dGTP and 8-oxo-dGDP, although the intrinsic enzyme activity of MTH2 is considerably lower than that of MTH1. On the other hand, MTH3 is specifically active against 8-oxo-dGDP and hardly cleaves 8-oxo-dGTP. Other types of oxidized nucleoside diphosphates, 2-hydroxy-dADP and 8-hydroxy-dADP, were also hydrolyzed by MTH3. Another notable feature of the MTH3 enzyme is its action toward the ribonucleotide counterpart. MTH3 can degrade 8-oxo-GDP as efficiently as 8-oxo-dGDP, which is in contrast to the finding that MTH1 and MTH2 show a limited activity against the ribonucleotide counterpart, 8-oxo-GTP. These three enzymes may function together to help maintain the high fidelity of DNA replication and transcription under oxidative stress.
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Affiliation(s)
| | | | - Riyoko Ito
- From the Fukuoka Dental College, Fukuoka 814-0193
| | - Hiroyuki Kamiya
- the Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, and
| | - Yuriko Yamagata
- the Graduate School of Pharmaceutical Science, Kumamoto University, Kumamoto 862-0973, Japan
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159
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Balagopal V, Fluch L, Nissan T. Ways and means of eukaryotic mRNA decay. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1819:593-603. [DOI: 10.1016/j.bbagrm.2012.01.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 12/29/2011] [Accepted: 01/03/2012] [Indexed: 10/14/2022]
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160
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Zhou P, Liu L, Tong H, Dong X. Role of operon aaoSo-mutT in antioxidant defense in Streptococcus oligofermentans. PLoS One 2012; 7:e38133. [PMID: 22666463 PMCID: PMC3364214 DOI: 10.1371/journal.pone.0038133] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Accepted: 05/04/2012] [Indexed: 11/28/2022] Open
Abstract
Previously, we have found that an insertional inactivation of aaoSo, a gene encoding L-amino acid oxidase (LAAO), causes marked repression of the growth of Streptococcus oligofermentans. Here, we found that aaoSo and mutT, a homolog of pyrophosphohydrolase gene of Escherichia coli, constituted an operon. Deletion of either gene did not impair the growth of S. oligofermentans, but double deletion of both aaoSo and mutT was lethal. Quantitative PCR showed that the transcript abundance of mutT was reduced for 13-fold in the aaoSo insertional mutant, indicating that gene polarity derived from the inactivation of aaoSo attenuated the expression of mutT. Enzymatic assays were conducted to determine the biochemical functions of LAAO and MutT of S. oligofermentans. The results indicated that LAAO functioned as an aminoacetone oxidase [47.75 nmol H2O2 (min·mg protein)–1]; and MutT showed the pyrophosphohydrolase activity, which removed mutagens such as 8-oxo-dGTP. Like paraquat, aaoSo mutations increased the expression of SOD, and addition of aminoacetone (final concentration, 5 mM) decreased the mutant’s growth by 11%, indicating that the aaoSo mutants are under ROS stress. HPLC did reveal elevated levels of cytoplasmic aminoacetone in both the deletion and insertional gene mutants of aaoSo. Electron spin resonance spectroscopy showed increased hydroxyl radicals in both types of aaoSo mutant. This demonstrated that inactivation of aaoSo caused the elevation of the prooxidant aminoacetone, resulting the cellular ROS stress. Our study indicates that the presence of both LAAO and MutT can prevent endogenous metabolites-generated ROS and mutagens. In this way, we were able to determine the role of the aaoSo-mutT operon in antioxidant defense in S. oligofermentans.
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Affiliation(s)
- Peng Zhou
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Lei Liu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Huichun Tong
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- * E-mail: (XD); (HT)
| | - Xiuzhu Dong
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- * E-mail: (XD); (HT)
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161
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Kawasaki K, Yoneyama M, Murata-Kamiya N, Harashima H, Kojima C, Ito Y, Kamiya H, Mishima M. ¹H, ¹³C and ¹⁵N NMR assignments of the Escherichia coli Orf135 protein. BIOMOLECULAR NMR ASSIGNMENTS 2012; 6:1-4. [PMID: 21553121 DOI: 10.1007/s12104-011-9312-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2011] [Accepted: 04/21/2011] [Indexed: 05/30/2023]
Abstract
Escherichia coli Orf135 protein is thought to be an enzyme that efficiently hydrolyzes oxidatively damaged nucleotides such as 2-hydroxy-dATP, 8-hydroxy-dGTP and 5-hydroxy-CTP, in addition to 5-methyl-dCTP, dCTP and CTP, thus preventing mutations in cells caused by unfavorable base pairing. Nucleotide pool sanitization by Orf135 is important since organisms are continually subjected to potential damage by reactive oxygen species produced during respiration. It is known that the frequency of spontaneous and H(2)O(2)-induced mutations is two to threefold higher in the orf135(-) strain compared with the wild-type. Orf135 is a member of the Nudix family of proteins which hydrolyze nucleoside diphosphate derivatives. Nudix hydrolases are characterized by the presence of a conserved motif, although they recognize various substrates and possess a variety of substrate binding pockets. We are interested in delineating the mechanism by which Orf135 recognizes oxidatively damaged nucleotides. To this end, we are investigating the tertiary structure of Orf135 and its interaction with substrate using NMR. Herein, we report on the (1)H, (13)C and (15)N resonance assignments of Orf135, which should contribute towards a structural understanding of Orf135 and its interaction with substrate.
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Affiliation(s)
- Kumiko Kawasaki
- Graduate School of Science and Technology, Tokyo Metropolitan University, 1-1 Minamiosawa, Hachioji 192-0397, Japan
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162
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Kawasaki K, Kanaba T, Yoneyama M, Murata-Kamiya N, Kojima C, Ito Y, Kamiya H, Mishima M. Insights into substrate recognition by the Escherichia coli Orf135 protein through its solution structure. Biochem Biophys Res Commun 2012; 420:263-8. [PMID: 22414689 DOI: 10.1016/j.bbrc.2012.02.146] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Accepted: 02/27/2012] [Indexed: 11/28/2022]
Abstract
Escherichia coli Orf135 hydrolyzes oxidatively damaged nucleotides such as 2-hydroxy-dATP, 8-oxo-dGTP and 5-hydroxy-CTP, in addition to 5-methyl-dCTP, dCTP and CTP. Nucleotide pool sanitization by Orf135 is important since nucleotides are continually subjected to potential damage by reactive oxygen species produced during respiration. Orf135 is a member of the Nudix family of proteins which hydrolyze nucleoside diphosphate derivatives. Nudix hydrolases are characterized by the presence of a conserved motif, even though they recognize various substrates and possess a variety of substrate binding pockets. We investigated the tertiary structure of Orf135 and its interaction with a 2-hydroxy-dATP analog using NMR. We report on the solution structure of Orf135, which should contribute towards a structural understanding of Orf135 and its interaction with substrates.
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Affiliation(s)
- Kumiko Kawasaki
- Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minamiosawa, Hachioji 192-0397, Japan
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163
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Interdomain dynamics and coactivation of the mRNA decapping enzyme Dcp2 are mediated by a gatekeeper tryptophan. Proc Natl Acad Sci U S A 2012; 109:2872-7. [PMID: 22323607 DOI: 10.1073/pnas.1113620109] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Conformational dynamics in bilobed enzymes can be used to regulate their activity. One such enzyme, the eukaryotic decapping enzyme Dcp2, controls the half-life of mRNA by cleaving the 5' cap structure, which exposes a monophosphate that is efficiently degraded by exonucleases. Decapping by Dcp2 is thought to be controlled by an open-to-closed transition involving formation of a composite active site with two domains sandwiching substrate, but many details of this process are not understood. Here, using NMR spectroscopy and enzyme kinetics, we show that Trp43 of Schizosaccharomyces pombe Dcp2 is a conserved gatekeeper of this open-to-closed transition. We find that Dcp2 samples multiple conformations in solution on the millisecond-microsecond timescale. Mutation of the gatekeeper tryptophan abolishes the dynamic behavior of Dcp2 and attenuates coactivation by a yeast enhancer of decapping (Edc1). Our results determine the dynamics of the open-to-closed transition in Dcp2, suggest a structural pathway for coactivation, predict that Dcp1 directly contacts the catalytic domain of Dcp2, and show that coactivation of decapping by Dcp2 is linked to formation of the composite active site.
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164
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Pulliainen AT, Dehio C. Persistence of Bartonella spp. stealth pathogens: from subclinical infections to vasoproliferative tumor formation. FEMS Microbiol Rev 2012; 36:563-99. [PMID: 22229763 DOI: 10.1111/j.1574-6976.2012.00324.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 12/13/2011] [Accepted: 12/13/2011] [Indexed: 01/11/2023] Open
Abstract
Bartonella spp. are facultative intracellular bacteria that typically cause a long-lasting intraerythrocytic bacteremia in their mammalian reservoir hosts, thereby favoring transmission by blood-sucking arthropods. In most cases, natural reservoir host infections are subclinical and the relapsing intraerythrocytic bacteremia may last weeks, months, or even years. In this review, we will follow the infection cycle of Bartonella spp. in a reservoir host, which typically starts with an intradermal inoculation of bacteria that are superficially scratched into the skin from arthropod feces and terminates with the pathogen exit by the blood-sucking arthropod. The current knowledge of bacterial countermeasures against mammalian immune response will be presented for each critical step of the pathogenesis. The prevailing models of the still-enigmatic primary niche and the anatomical location where bacteria reside, persist, and are periodically seeded into the bloodstream to cause the typical relapsing Bartonella spp. bacteremia will also be critically discussed. The review will end up with a discussion of the ability of Bartonella spp., namely Bartonella henselae, Bartonella quintana, and Bartonella bacilliformis, to induce tumor-like vascular deformations in humans having compromised immune response such as in patients with AIDS.
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165
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Brown SD, Babbitt PC. Inference of functional properties from large-scale analysis of enzyme superfamilies. J Biol Chem 2011; 287:35-42. [PMID: 22069325 DOI: 10.1074/jbc.r111.283408] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
As increasingly large amounts of data from genome and other sequencing projects become available, new approaches are needed to determine the functions of the proteins these genes encode. We show how large-scale computational analysis can help to address this challenge by linking functional information to sequence and structural similarities using protein similarity networks. Network analyses using three functionally diverse enzyme superfamilies illustrate the use of these approaches for facile updating and comparison of available structures for a large superfamily, for creation of functional hypotheses for metagenomic sequences, and to summarize the limits of our functional knowledge about even well studied superfamilies.
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Affiliation(s)
- Shoshana D Brown
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, California, 94158-2330
| | - Patricia C Babbitt
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, California, 94158-2330; Pharmaceutical Chemistry, School of Pharmacy; California Institute for Quantitative Biosciences, University of California, San Francisco, California 94158-2330.
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166
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Dong S, Yin W, Kong G, Yang X, Qutob D, Chen Q, Kale SD, Sui Y, Zhang Z, Dou D, Zheng X, Gijzen M, M. Tyler B, Wang Y. Phytophthora sojae avirulence effector Avr3b is a secreted NADH and ADP-ribose pyrophosphorylase that modulates plant immunity. PLoS Pathog 2011; 7:e1002353. [PMID: 22102810 PMCID: PMC3213090 DOI: 10.1371/journal.ppat.1002353] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 09/19/2011] [Indexed: 11/18/2022] Open
Abstract
Plants have evolved pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI) to protect themselves from infection by diverse pathogens. Avirulence (Avr) effectors that trigger plant ETI as a result of recognition by plant resistance (R) gene products have been identified in many plant pathogenic oomycetes and fungi. However, the virulence functions of oomycete and fungal Avr effectors remain largely unknown. Here, we combined bioinformatics and genetics to identify Avr3b, a new Avr gene from Phytophthora sojae, an oomycete pathogen that causes soybean root rot. Avr3b encodes a secreted protein with the RXLR host-targeting motif and C-terminal W and Nudix hydrolase motifs. Some isolates of P. sojae evade perception by the soybean R gene Rps3b through sequence mutation in Avr3b and lowered transcript accumulation. Transient expression of Avr3b in Nicotiana benthamiana increased susceptibility to P. capsici and P. parasitica, with significantly reduced accumulation of reactive oxygen species (ROS) around invasion sites. Biochemical assays confirmed that Avr3b is an ADP-ribose/NADH pyrophosphorylase, as predicted from the Nudix motif. Deletion of the Nudix motif of Avr3b abolished enzyme activity. Mutation of key residues in Nudix motif significantly impaired Avr3b virulence function but not the avirulence activity. Some Nudix hydrolases act as negative regulators of plant immunity, and thus Avr3b might be delivered into host cells as a Nudix hydrolase to impair host immunity. Avr3b homologues are present in several sequenced Phytophthora genomes, suggesting that Phytophthora pathogens might share similar strategies to suppress plant immunity.
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Affiliation(s)
- Suomeng Dong
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Nanjing Agricultural University), Ministry of Education, Nanjing, China
| | - Weixiao Yin
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Guanghui Kong
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Xinyu Yang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Dinah Qutob
- Agriculture and Agri-Food Canada, London, Ontario, Canada
| | - Qinghe Chen
- Virginia Bioinformatics Institute, Blacksburg, Virginia, United States of America
| | - Shiv D. Kale
- Virginia Bioinformatics Institute, Blacksburg, Virginia, United States of America
| | - Yangyang Sui
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Zhengguang Zhang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Nanjing Agricultural University), Ministry of Education, Nanjing, China
| | - Daolong Dou
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Nanjing Agricultural University), Ministry of Education, Nanjing, China
| | - Xiaobo Zheng
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Nanjing Agricultural University), Ministry of Education, Nanjing, China
| | - Mark Gijzen
- Agriculture and Agri-Food Canada, London, Ontario, Canada
| | - Brett M. Tyler
- Virginia Bioinformatics Institute, Blacksburg, Virginia, United States of America
| | - Yuanchao Wang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Nanjing Agricultural University), Ministry of Education, Nanjing, China
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167
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Engelhardt BE, Jordan MI, Srouji JR, Brenner SE. Genome-scale phylogenetic function annotation of large and diverse protein families. Genome Res 2011; 21:1969-80. [PMID: 21784873 PMCID: PMC3205580 DOI: 10.1101/gr.104687.109] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Accepted: 07/11/2011] [Indexed: 11/25/2022]
Abstract
The Statistical Inference of Function Through Evolutionary Relationships (SIFTER) framework uses a statistical graphical model that applies phylogenetic principles to automate precise protein function prediction. Here we present a revised approach (SIFTER version 2.0) that enables annotations on a genomic scale. SIFTER 2.0 produces equivalently precise predictions compared to the earlier version on a carefully studied family and on a collection of 100 protein families. We have added an approximation method to SIFTER 2.0 and show a 500-fold improvement in speed with minimal impact on prediction results in the functionally diverse sulfotransferase protein family. On the Nudix protein family, previously inaccessible to the SIFTER framework because of the 66 possible molecular functions, SIFTER achieved 47.4% accuracy on experimental data (where BLAST achieved 34.0%). Finally, we used SIFTER to annotate all of the Schizosaccharomyces pombe proteins with experimental functional characterizations, based on annotations from proteins in 46 fungal genomes. SIFTER precisely predicted molecular function for 45.5% of the characterized proteins in this genome, as compared with four current function prediction methods that precisely predicted function for 62.6%, 30.6%, 6.0%, and 5.7% of these proteins. We use both precision-recall curves and ROC analyses to compare these genome-scale predictions across the different methods and to assess performance on different types of applications. SIFTER 2.0 is capable of predicting protein molecular function for large and functionally diverse protein families using an approximate statistical model, enabling phylogenetics-based protein function prediction for genome-wide analyses. The code for SIFTER and protein family data are available at http://sifter.berkeley.edu.
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Affiliation(s)
- Barbara E Engelhardt
- Electrical Engineering and Computer Science Department, University of California, Berkeley, California 94720, USA.
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168
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Gene expression signatures and ex vivo drug sensitivity profiles in children with acute lymphoblastic leukemia. J Appl Genet 2011; 53:83-91. [PMID: 22038456 DOI: 10.1007/s13353-011-0073-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Revised: 10/01/2011] [Accepted: 10/03/2011] [Indexed: 01/15/2023]
Abstract
INTRODUCTION Causes of treatment failure in acute lymphoblastic leukemia (ALL) are still poorly understood. Microarray technology gives new possibilities for the analysis of the biology of leukemias. We hypothesize that drug sensitivity in pediatric ALL is driven by specific molecular mechanisms that correlate with gene expression profiles assessed by microarray analysis. OBJECTIVE The aim of the study was to determine the ex vivo resistance profiles of 20 antileukemic drugs and gene expression profiles, with relation to response to initial therapy. PATIENTS AND METHODS Lymphoblasts were analyzed after bone marrow biopsy was obtained from 56 patients. The profile of in vitro resistance to drugs was determined in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) cytotoxicity assay. High-quality total RNA was prepared and hybridized to oligonucleotide arrays HG-U133A 2.0 Chip (Affymetrix). The expression of selected genes was tested by qualitative reverse transcription polymerase chain reaction (qRT-PCR). RESULTS AND CONCLUSIONS The exposure of leukemic blasts to drugs initiates a complex cellular response, which reflects global changes in gene expression. Changes in the expression of several genes are highly correlated with drug resistance.
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169
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Jiang YL, Zhang JW, Yu WL, Cheng W, Zhang CC, Frolet C, Di Guilmi AM, Vernet T, Zhou CZ, Chen Y. Structural and enzymatic characterization of the streptococcal ATP/diadenosine polyphosphate and phosphodiester hydrolase Spr1479/SapH. J Biol Chem 2011; 286:35906-35914. [PMID: 21865160 PMCID: PMC3195627 DOI: 10.1074/jbc.m111.228585] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2011] [Revised: 08/04/2011] [Indexed: 01/07/2023] Open
Abstract
Spr1479 from Streptococcus pneumoniae R6 is a 33-kDa hypothetical protein of unknown function. Here, we determined the crystal structures of its apo-form at 1.90 Å and complex forms with inorganic phosphate and AMP at 2.30 and 2.20 Å, respectively. The core structure of Spr1479 adopts a four-layer αββα-sandwich fold, with Fe(3+) and Mn(2+) coordinated at the binuclear center of the active site (similar to metallophosphoesterases). Enzymatic assays showed that, in addition to phosphodiesterase activity for bis(p-nitrophenyl) phosphate, Spr1479 has hydrolase activity for diadenosine polyphosphate (Ap(n)A) and ATP. Residues that coordinate with the two metals are indispensable for both activities. By contrast, the streptococcus-specific residue Trp-67, which binds to phosphate in the two complex structures, is indispensable for the ATP/Ap(n)A hydrolase activity only. Moreover, the AMP-binding pocket is conserved exclusively in all streptococci. Therefore, we named the protein SapH for streptococcal ATP/Ap(n)A and phosphodiester hydrolase.
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Affiliation(s)
- Yong-Liang Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jun-Wei Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wei-Li Yu
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wang Cheng
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Chen-Chen Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Cecile Frolet
- Laboratoire d'Ingénierie des Macromolécules, Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075, 41 rue Jules Horowitz, 38027 Grenoble, France
| | - Anne-Marie Di Guilmi
- Laboratoire d'Ingénierie des Macromolécules, Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075, 41 rue Jules Horowitz, 38027 Grenoble, France
| | - Thierry Vernet
- Laboratoire d'Ingénierie des Macromolécules, Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075, 41 rue Jules Horowitz, 38027 Grenoble, France
| | - Cong-Zhao Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Yuxing Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
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170
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Richards J, Liu Q, Pellegrini O, Celesnik H, Yao S, Bechhofer DH, Condon C, Belasco JG. An RNA pyrophosphohydrolase triggers 5'-exonucleolytic degradation of mRNA in Bacillus subtilis. Mol Cell 2011; 43:940-9. [PMID: 21925382 PMCID: PMC3176438 DOI: 10.1016/j.molcel.2011.07.023] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 05/31/2011] [Accepted: 07/14/2011] [Indexed: 11/29/2022]
Abstract
In Escherichia coli, RNA degradation often begins with conversion of the 5'-terminal triphosphate to a monophosphate, creating a better substrate for internal cleavage by RNase E. Remarkably, no homolog of this key endonuclease is present in many bacterial species, such as Bacillus subtilis and various pathogens. Here, we report that the degradation of primary transcripts in B. subtilis can nevertheless be triggered by an analogous process to generate a short-lived, monophosphorylated intermediate. Like its E. coli counterpart, the B. subtilis RNA pyrophosphohydrolase that catalyzes this event is a Nudix protein that prefers unpaired 5' ends. However, in B. subtilis, this modification exposes transcripts to rapid 5' exonucleolytic degradation by RNase J, which is absent in E. coli but present in most bacteria lacking RNase E. This pathway, which closely resembles the mechanism by which deadenylated mRNA is degraded in eukaryotic cells, explains the stabilizing influence of 5'-terminal stem-loops in such bacteria.
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Affiliation(s)
- Jamie Richards
- Kimmel Center for Biology and Medicine at the Skirball Institute and Department of Microbiology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - Quansheng Liu
- Kimmel Center for Biology and Medicine at the Skirball Institute and Department of Microbiology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - Olivier Pellegrini
- CNRS UPR 9073 (affiliated with Université de Paris Diderot, Sorbonne Paris Cité) and Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Helena Celesnik
- Kimmel Center for Biology and Medicine at the Skirball Institute and Department of Microbiology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - Shiyi Yao
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine of New York University, Box 1603, 1 Gustave L. Levy Place, New York, NY 10029, USA
| | - David H. Bechhofer
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine of New York University, Box 1603, 1 Gustave L. Levy Place, New York, NY 10029, USA
| | - Ciarán Condon
- CNRS UPR 9073 (affiliated with Université de Paris Diderot, Sorbonne Paris Cité) and Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Joel G. Belasco
- Kimmel Center for Biology and Medicine at the Skirball Institute and Department of Microbiology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
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171
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Buchko GW, Edwards TE, Abendroth J, Arakaki TL, Law L, Napuli AJ, Hewitt SN, Van Voorhis WC, Stewart LJ, Staker BL, Myler PJ. Structure of a Nudix hydrolase (MutT) in the Mg(2+)-bound state from Bartonella henselae, the bacterium responsible for cat scratch fever. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:1078-83. [PMID: 21904053 PMCID: PMC3169405 DOI: 10.1107/s1744309111011559] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Accepted: 03/28/2011] [Indexed: 05/31/2023]
Abstract
Cat scratch fever (also known as cat scratch disease and bartonellosis) is an infectious disease caused by the proteobacterium Bartonella henselae following a cat scratch. Although the infection usually resolves spontaneously without treatment in healthy adults, bartonellosis may lead to severe complications in young children and immunocompromised patients, and there is new evidence suggesting that B. henselae may be associated with a broader range of clinical symptoms then previously believed. The genome of B. henselae contains genes for two putative Nudix hydrolases, BH02020 and BH01640 (KEGG). Nudix proteins play an important role in regulating the intracellular concentration of nucleotide cofactors and signaling molecules. The amino-acid sequence of BH02020 is similar to that of the prototypical member of the Nudix superfamily, Escherichia coli MutT, a protein that is best known for its ability to neutralize the promutagenic compound 7,8-dihydro-8-oxoguanosine triphosphate. Here, the crystal structure of BH02020 (Bh-MutT) in the Mg(2+)-bound state was determined at 2.1 Å resolution (PDB entry 3hhj). As observed in all Nudix hydrolase structures, the α-helix of the highly conserved `Nudix box' in Bh-MutT is one of two helices that sandwich a four-stranded mixed β-sheet with the central two β-strands parallel to each other. The catalytically essential divalent cation observed in the Bh-MutT structure, Mg(2+), is coordinated to the side chains of Glu57 and Glu61. The structure is not especially robust; a temperature melt obtained using circular dichroism spectroscopy shows that Bh-MutT irreversibly unfolds and precipitates out of solution upon heating, with a T(m) of 333 K.
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Affiliation(s)
- Garry W. Buchko
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Thomas E. Edwards
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Emerald BioStructures, Bainbridge Island, Washington, USA
| | - Jan Abendroth
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Emerald BioStructures, Bainbridge Island, Washington, USA
| | - Tracy L. Arakaki
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Emerald BioStructures, Bainbridge Island, Washington, USA
| | - Laura Law
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Emerald BioStructures, Bainbridge Island, Washington, USA
| | - Alberto J. Napuli
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Stephen N. Hewitt
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Wesley C. Van Voorhis
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Lance J. Stewart
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Emerald BioStructures, Bainbridge Island, Washington, USA
| | - Bart L. Staker
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Emerald BioStructures, Bainbridge Island, Washington, USA
| | - Peter J. Myler
- Seattle Structural Genomics Center for Infectious Disease, http://www.ssgcid.org, USA
- Seattle Biomedical Research Institute, Seattle, Washington, USA
- Department of Medical Education and Biomedical Informatics and Department of Global Health, University of Washington, Seattle, Washington, USA
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172
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Yang Q, Gilmartin GM, Doublié S. The structure of human cleavage factor I(m) hints at functions beyond UGUA-specific RNA binding: a role in alternative polyadenylation and a potential link to 5' capping and splicing. RNA Biol 2011; 8:748-53. [PMID: 21881408 DOI: 10.4161/rna.8.5.16040] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
3'-end cleavage and subsequent polyadenylation are critical steps in mRNA maturation. The precise location where cleavage occurs (referred to as poly(A) site) is determined by a tripartite mechanism in which a A(A/U)UAAA hexamer, GU rich downstream element and UGUA upstream element are recognized by the cleavage and polyadenylation factor (CPSF), cleavage stimulation factor (CstF) and cleavage factor I(m) (CFI(m)), respectively. CFI(m) is composed of a smaller 25 kDa subunit (CFI(m)25) and a larger 59, 68 or 72 kDa subunit. CFI(m)68 interacts with CFI(m)25 through its N-terminal RNA recognition motif (RRM). We recently solved the crystal structures of CFI(m)25 bound to RNA and of a complex of CFI(m)25, the RRM domain of CFI(m)68 and RNA. Our study illustrated the molecular basis for UGUA recognition by the CFI(m) complex, suggested a possible mechanism for CFI(m) mediated alternative polyadenylation, and revealed potential links between CFI(m) and other mRNA processing factors, such as the 20 kDa subunit of the cap binding protein (CBP20), and the splicing regulator U2AF65.
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Affiliation(s)
- Qin Yang
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, University of Vermont, Burlington, VT, USA
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173
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Sanada U, Yonekura SI, Kikuchi M, Hashiguchi K, Nakamura N, Yonei S, Zhang-Akiyama QM. NDX-1 protein hydrolyzes 8-oxo-7, 8-dihydrodeoxyguanosine-5'-diphosphate to sanitize oxidized nucleotides and prevent oxidative stress in Caenorhabditis elegans. J Biochem 2011; 150:649-57. [PMID: 21873335 DOI: 10.1093/jb/mvr107] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
8-oxo-dGTP is generated in the nucleotide pool by direct oxidation of dGTP or phosphorylation of 8-oxo-dGDP. It can be incorporated into DNA during replication, which would result in mutagenic consequences. The frequency of spontaneous mutations remains low in cells owing to the action of enzymes degrading such mutagenic substrates. Escherichia coli MutT and human MTH1 hydrolyze 8-oxo-dGTP to 8-oxo-dGMP. Human NUDT5 as well as human MTH1 hydrolyze 8-oxo-dGDP to 8-oxo-dGMP. These enzymes prevent mutations caused by misincorporation of 8-oxo-dGTP into DNA. In this study, we identified a novel MutT homolog (NDX-1) of Caenorhabditis elegans that hydrolyzes 8-oxo-dGDP to 8-oxo-dGMP. NDX-1 did not hydrolyze 8-oxo-dGTP, 2-hydroxy-dATP or 2-hydroxy-dADP. Expression of NDX-1 significantly reduced spontaneous A:T to C:G transversions and mitigated the sensitivity to a superoxide-generating agent, methyl viologen, in an E. coli mutT mutant. In C. elegans, RNAi of ndx-1 did not affect the lifespan of the worm. However, the sensitivity to methyl viologen and menadione bisulfite of the ndx-1-RNAi worms was enhanced compared with that of the control worms. These facts indicate that NDX-1 is involved in sanitization of 8-oxo-dGDP and plays a critical role in defense against oxidative stress in C. elegans.
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Affiliation(s)
- U Sanada
- Laboratory of Stress Response Biology, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
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174
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Svensson LM, Jemth AS, Desroses M, Loseva O, Helleday T, Högbom M, Stenmark P. Crystal structure of human MTH1 and the 8-oxo-dGMP product complex. FEBS Lett 2011; 585:2617-21. [PMID: 21787772 DOI: 10.1016/j.febslet.2011.07.017] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Revised: 07/04/2011] [Accepted: 07/13/2011] [Indexed: 11/24/2022]
Abstract
MTH1 hydrolyzes oxidized nucleotide triphosphates, thereby preventing them from being incorporated into DNA. We here present the structures of human MTH1 (1.9Å) and its complex with the product 8-oxo-dGMP (1.8Å). Unexpectedly MTH1 binds the nucleotide in the anti conformation with no direct interaction between the 8-oxo group and the protein. We suggest that the specificity depends on the stabilization of an enol tautomer of the 8-oxo form of dGTP. The binding of the product induces no major structural changes. The structures reveal the mode of nucleotide binding in MTH1 and provide the structural basis for inhibitor design.
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Affiliation(s)
- Linda M Svensson
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
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175
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Duong-Ly KC, Gabelli SB, Xu W, Dunn CA, Schoeffield AJ, Bessman MJ, Amzel LM. The Nudix hydrolase CDP-chase, a CDP-choline pyrophosphatase, is an asymmetric dimer with two distinct enzymatic activities. J Bacteriol 2011; 193:3175-85. [PMID: 21531795 PMCID: PMC3133267 DOI: 10.1128/jb.00089-11] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Accepted: 04/22/2011] [Indexed: 11/20/2022] Open
Abstract
A Nudix enzyme from Bacillus cereus (NCBI RefSeq accession no. NP_831800) catalyzes the hydrolysis of CDP-choline to produce CMP and phosphocholine. Here, we show that in addition, the enzyme has a 3'→5' RNA exonuclease activity. The structure of the free enzyme, determined to a 1.8-Å resolution, shows that the enzyme is an asymmetric dimer. Each monomer consists of two domains, an N-terminal helical domain and a C-terminal Nudix domain. The N-terminal domain is placed relative to the C-terminal domain such as to result in an overall asymmetric arrangement with two distinct catalytic sites: one with an "enclosed" Nudix pyrophosphatase site and the other with a more open, less-defined cavity. Residues that may be important for determining the asymmetry are conserved among a group of uncharacterized Nudix enzymes from Gram-positive bacteria. Our data support a model where CDP-choline hydrolysis is catalyzed by the enclosed Nudix site and RNA exonuclease activity is catalyzed by the open site. CDP-Chase is the first identified member of a novel Nudix family in which structural asymmetry has a profound effect on the recognition of substrates.
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Affiliation(s)
- Krisna C. Duong-Ly
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Sandra B. Gabelli
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - WenLian Xu
- Department of Biology and McCollum-Pratt Institute, Johns Hopkins University, Baltimore, Maryland 21218
| | - Christopher A. Dunn
- Department of Biology and McCollum-Pratt Institute, Johns Hopkins University, Baltimore, Maryland 21218
| | | | - Maurice J. Bessman
- Department of Biology and McCollum-Pratt Institute, Johns Hopkins University, Baltimore, Maryland 21218
| | - L. Mario Amzel
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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176
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Yang Q, Doublié S. Structural biology of poly(A) site definition. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 2:732-47. [PMID: 21823232 DOI: 10.1002/wrna.88] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
3' processing is an essential step in the maturation of all messenger RNAs (mRNAs) and is a tightly coupled two-step reaction: endonucleolytic cleavage at the poly(A) site is followed by the addition of a poly(A) tail, except for metazoan histone mRNAs, which are cleaved but not polyadenylated. The recognition of a poly(A) site is coordinated by the sequence elements in the mRNA 3' UTR and associated protein factors. In mammalian cells, three well-studied sequence elements, UGUA, AAUAAA, and GU-rich, are recognized by three multisubunit factors: cleavage factor I(m) (CFI(m) ), cleavage and polyadenylation specificity factor (CPSF), and cleavage stimulation factor (CstF), respectively. In the yeast Saccharomyces cerevisiae, UA repeats and A-rich sequence elements are recognized by Hrp1p and cleavage factor IA. Structural studies of protein-RNA complexes have helped decipher the mechanisms underlying sequence recognition and shed light on the role of protein factors in poly(A) site selection and 3' processing machinery assembly. In this review we focus on the interactions between the mRNA cis-elements and the protein factors (CFI(m) , CPSF, CstF, and homologous factors from yeast and other eukaryotes) that define the poly(A) site. WIREs RNA 2011 2 732-747 DOI: 10.1002/wrna.88 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Qin Yang
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, USA
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177
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Yonekura SI, Sanada U, Zhang-Akiyama QM. CiMutT, an asidian MutT homologue, has a 7, 8-dihydro-8-oxo-dGTP pyrophosphohydrolase activity responsible for sanitization of oxidized nucleotides in Ciona intestinalis. Genes Genet Syst 2011; 85:287-95. [PMID: 21178309 DOI: 10.1266/ggs.85.287] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The oxidized nucleotide precursors 7, 8-dihydro-8-oxo-dGTP (8-oxo-dGTP) and 1, 2-dihydro-2-oxo-dATP (2-oxo-dATP) are readily incorporated into nascent DNA strands during replication, which would cause base substitution mutations. E. coli MutT and human homologue hMTH1 hydrolyze 8-oxo-dGTP, thereby preventing mutations. In this study, we searched for hMTH1 homologues in the ascidian Ciona intestinalis using the NCBI-BLAST database. Among several candidates, we focused on one open reading frame, designated as CiMutT, because of its high degree of identity (41.7%) and similarity (58.3%) to the overall amino acid sequence of hMTH1, including the Nudix box. CiMutT significantly suppressed the mutator activity of E. coli mutT mutant. Purified CiMutT had a pyrophosphohydrolase activity that hydrolyzed 8-oxo-dGTP to 8-oxo-dGMP and inorganic pyrophosphate. It had a pH optimum of 9.5 and Mg(++) requirement with optimal activity at 5 mM. The activity of CiMutT for 8-oxo-dGTP was comparable to that of hMTH1, while it was 100-fold lower for 2-oxo-dATP than that of hMTH1. These facts indicate that CiMutT is a functional homologue of E. coli MutT. In addition, the enzyme hydrolyzed all four of the unoxidized nucleoside triphosphates, with a preference for dATP. The specific activity for 8-oxo-dGTP was greater than that for unoxidized dATP and dGTP. These results suggest that CiMutT has the potential to prevent mutations by 8-oxo-dGTP in C. intestinalis.
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Affiliation(s)
- Shin-Ichiro Yonekura
- Laboratory of Stress Response Biology, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
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178
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Ito R, Sekiguchi M, Setoyama D, Nakatsu Y, Yamagata Y, Hayakawa H. Cleavage of oxidized guanine nucleotide and ADP sugar by human NUDT5 protein. J Biochem 2011; 149:731-8. [PMID: 21389046 DOI: 10.1093/jb/mvr028] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
MutT-related proteins, including Escherichia coli MutT and the human MTH1 (NUDT1), degrade 8-oxo-7, 8-dihydrodeoxyguanosine triphosphate (8-oxo-dGTP) to 8-oxo-dGMP and thereby prevent mutations caused by the misincorporation of 8-oxoguanine into DNA. The human NUDT5, which has an intrinsic activity to cleave ADP sugars to AMP and sugar phosphate, possesses the ability to degrade 8-oxo-dGDP to the monophosphate. Since 8-oxo-dGDP and 8-oxo-dGTP are interconvertible by cellular enzymes, NUDT5 has the potential to prevent errors during DNA replication. The two activities associated with NUDT5 exhibit different pH dependencies; the optimum for the cleavage of ADP ribose is pH 7-9, while that for 8-oxo-dGDPase is around pH 10. The kinetic parameters for the two types of reactions indicated that ADP ribose is a better substrate for NUDT5 compared with oxidized guanine nucleotides. The 8-oxo-dGDP cleavage was competitively inhibited by ADP ribose and its reaction product, AMP, and in reverse, the cleavage of ADP ribose was inhibited by 8-oxo-dGDP. These results imply that the two types of substrates may share the same binding site for catalysis.
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Affiliation(s)
- Riyoko Ito
- Department of Functional Bioscience and Advanced Science Research Center, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka, Japan.
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179
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Lu G, Zhang J, Li Y, Li Z, Zhang N, Xu X, Wang T, Guan Z, Gao GF, Yan J. hNUDT16: a universal decapping enzyme for small nucleolar RNA and cytoplasmic mRNA. Protein Cell 2011; 2:64-73. [PMID: 21337011 DOI: 10.1007/s13238-011-1009-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 01/19/2011] [Indexed: 11/26/2022] Open
Abstract
Human NUDT16 (hNUDT16) is a decapping enzyme initially identified as the human homolog to the Xenopus laevis X29. As a metalloenzyme, hNUDT16 relies on divalent cations for its cap-hydrolysis activity to remove m⁷GDP and m²²⁷GDP from RNAs. Metal also determines substrate specificity of the enzyme. So far, only U8 small nucleolar RNA (snoRNA) has been identified as the substrate of hNUDT16 in the presence of Mg²(+). Here we demonstrate that besides U8, hNUDT16 can also actively cleave the m⁷GDP cap from mRNAs in the presence of Mg²(+) or Mn²(+). We further show that hNUDT16 does not preferentially recognize U8 or mRNA substrates by our cross-inhibition and quantitative decapping assays. In addition, our mutagenesis analysis identifies several key residues involved in hydrolysis and confirms the key role of the REXXEE motif in catalysis. Finally an investigation into the subcellular localization of hNUDT16 revealed its abundance in both cytoplasm and nucleus. These findings extend the substrate spectrum of hNUDT16 beyond snoRNAs to also include mRNA, demonstrating the pleiotropic decapping activity of hNUDT16.
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Affiliation(s)
- Guangwen Lu
- CAS Key Laboratory of Pathogenic Microbiology and Immunology (CASPMI), Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing, 100101, China
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180
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Borja MS, Piotukh K, Freund C, Gross JD. Dcp1 links coactivators of mRNA decapping to Dcp2 by proline recognition. RNA (NEW YORK, N.Y.) 2011; 17:278-90. [PMID: 21148770 PMCID: PMC3022277 DOI: 10.1261/rna.2382011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Accepted: 11/08/2010] [Indexed: 05/20/2023]
Abstract
Cap hydrolysis is a critical step in several eukaryotic mRNA decay pathways and is carried out by the evolutionarily conserved decapping complex containing Dcp2 at the catalytic core. In yeast, Dcp1 is an essential activator of decapping and coactivators such as Edc1 and Edc2 are thought to enhance activity, though their mechanism remains elusive. Using kinetic analysis we show that a crucial function of Dcp1 is to couple the binding of coactivators of decapping to activation of Dcp2. Edc1 and Edc2 bind Dcp1 via its EVH1 proline recognition site and stimulate decapping by 1000-fold, affecting both the K(M) for mRNA and rate of the catalytic step. The C-terminus of Edc1 is necessary and sufficient to enhance the catalytic step, while the remainder of the protein likely increases mRNA binding to the decapping complex. Lesions in the Dcp1 EVH1 domain or the Edc1 proline-rich sequence are sufficient to block stimulation. These results identify a new role of Dcp1, which is to link the binding of coactivators to substrate recognition and activation of Dcp2.
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Affiliation(s)
- Mark S Borja
- Program in Chemistry and Chemical Biology, University of California, San Francisco, California 94158, USA
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181
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Hasenöhrl D, Konrat R, Bläsi U. Identification of an RNase J ortholog in Sulfolobus solfataricus: implications for 5'-to-3' directional decay and 5'-end protection of mRNA in Crenarchaeota. RNA (NEW YORK, N.Y.) 2011; 17:99-107. [PMID: 21115637 PMCID: PMC3004070 DOI: 10.1261/rna.2418211] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Accepted: 10/07/2010] [Indexed: 05/29/2023]
Abstract
In both Bacteria and Eukaryotes, degradation is known to start at the 5' and at the 3' extremities of mRNAs. Until the recent discovery of 5'-to-3' exoribonucleases in hyperthermophilic Euryarchaeota, the exosome was assumed to be the key enzyme in mRNA degradation in Archaea. By means of zymogram assays and bioinformatics, we have identified a 5'-to-3' exoribonuclease activity in the crenarchaeum Sulfolobus solfataricus (Sso), which is affected by the phosphorylation state of the 5'-end of the mRNA. The protein comprises typical signature motifs of the β-CASP family of metallo-β-lactamases and was termed Sso-RNAse J. Thus, our study provides the first evidence for a 5'-to-3' directional mRNA decay pathway in the crenarchaeal clade of Archaea. In Bacteria the 5'-end of mRNAs is often protected by a tri-phosphorylated 5'-terminus and/or by stem-loop structures, while in Eukaryotes the cap-binding complex is responsible for this task. Here, we show that binding of translation initiation factor a/eIF2(γ) to the 5'-end of mRNA counteracts the 5'-to-3' exoribonucleolytic activity of Sso-RNase J in vitro. Hence, 5'-to-3' directional decay and 5'-end protection appear to be conserved features of mRNA turnover in all kingdoms of life.
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Affiliation(s)
- David Hasenöhrl
- Max F. Perutz Laboratories, Department of Microbiology, Immunobiology and Genetics, University of Vienna, 1030 Vienna, Austria
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182
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Costas MJ, Pinto RM, Cordero PM, Cabezas A, Alves-Pereira I, Cameselle JC, Ribeiro JM. CGDEase, a Pseudomonas fluorescens protein of the PLC/APase superfamily with CDP-ethanolamine and (dihexanoyl)glycerophosphoethanolamine hydrolase activity induced by osmoprotectants under phosphate-deficient conditions. Mol Microbiol 2010; 78:1556-76. [PMID: 21143324 DOI: 10.1111/j.1365-2958.2010.07425.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A novel enzyme, induced by choline, ethanolamine, glycine betaine or dimethylglycine, was released at low temperature and phosphate from Pseudomonas fluorescens (CECT 7229) suspensions at low cell densities. It is a CDP-ethanolamine pyrophosphatase/(dihexanoyl)glycerophosphoethanolamine phosphodiesterase (CGDEase) less active on choline derivatives, and inactive on long-chain phospholipids, CDP-glycerol and other NDP-X compounds. The reaction pattern was typical of phospholipase C (PLC), as either phosphoethanolamine or phosphocholine was produced. Peptide-mass analyses, gene cloning and expression provided a molecular identity for CGDEase. Bioinformatic studies assigned it to the PLC branch of the phospholipase C/acid phosphatase (PLC/APase) superfamily, revealed an irregular phylogenetic distribution of close CGDEase relatives, and suggested their genes are not in operons or conserved contexts. A theoretical CGDEase structure was supported by mutagenesis of two predicted active-site residues, which yielded essentially inactive mutants. Biological relevance is supported by comparisons with CGDEase relatives, induction by osmoprotectants (not by osmotic stress itself) and repression by micromolar phosphate. The low bacterial density requirement was related to phosphate liberation from lysed bacteria in denser populations, rather than to a classical quorum-sensing effect. The results fit better a CGDEase role in phosphate scavenging than in osmoprotection.
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Affiliation(s)
- María Jesús Costas
- Departamento de Bioquímica y Biología Molecular y Genética, Universidad de Extremadura, Badajoz E-06006, Spain
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183
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Abstract
Nucleases cleave the phosphodiester bonds of nucleic acids and may be endo or exo, DNase or RNase, topoisomerases, recombinases, ribozymes, or RNA splicing enzymes. In this review, I survey nuclease activities with known structures and catalytic machinery and classify them by reaction mechanism and metal-ion dependence and by their biological function ranging from DNA replication, recombination, repair, RNA maturation, processing, interference, to defense, nutrient regeneration or cell death. Several general principles emerge from this analysis. There is little correlation between catalytic mechanism and biological function. A single catalytic mechanism can be adapted in a variety of reactions and biological pathways. Conversely, a single biological process can often be accomplished by multiple tertiary and quaternary folds and by more than one catalytic mechanism. Two-metal-ion-dependent nucleases comprise the largest number of different tertiary folds and mediate the most diverse set of biological functions. Metal-ion-dependent cleavage is exclusively associated with exonucleases producing mononucleotides and endonucleases that cleave double- or single-stranded substrates in helical and base-stacked conformations. All metal-ion-independent RNases generate 2',3'-cyclic phosphate products, and all metal-ion-independent DNases form phospho-protein intermediates. I also find several previously unnoted relationships between different nucleases and shared catalytic configurations.
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184
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Metzger LE, Raetz CRH. An alternative route for UDP-diacylglucosamine hydrolysis in bacterial lipid A biosynthesis. Biochemistry 2010; 49:6715-26. [PMID: 20608695 DOI: 10.1021/bi1008744] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The outer leaflet of the outer membranes of Gram-negative bacteria is composed primarily of lipid A, the hydrophobic anchor of lipopolysaccharide. Like Escherichia coli, most Gram-negative bacteria encode one copy of each of the nine genes required for lipid A biosynthesis. An important exception exists in the case of the fourth enzyme, LpxH, a peripheral membrane protein that hydrolyzes UDP-2,3-diacylglucosamine to form 2,3-diacylglucosamine 1-phosphate and UMP by catalyzing the attack of water at the alpha-P atom. Many Gram-negative organisms, including all alpha-proteobacteria and diverse environmental isolates, lack LpxH. Here, we report a distinct UDP-2,3-diacylglucosamine pyrophosphatase, designated LpxI, which has no sequence similarity to LpxH but generates the same products by a different route. LpxI was identified because its structural gene is located between lpxA and lpxB in Caulobacter crescentus. The lpxI gene rescues the conditional lethality of lpxH-deficient E. coli. Lysates of E. coli in which C. crescentus LpxI (CcLpxI) is overexpressed display high levels of UDP-2,3-diacylglucosamine pyrophosphatase activity. CcLpxI was purified to >90% homogeneity. CcLpxI is stimulated by divalent cations and is inhibited by EDTA. Unlike E. coli LpxH, CcLpxI is not inhibited by an increase in the concentration of detergent, and its pH dependency is different. When the CcLpxI reaction is conducted in the presence of H(2)(18)O, the (18)O is incorporated exclusively into the 2,3-diacylglucosamine 1-phosphate product, as judged by mass spectrometry, demonstrating that CcLpxI catalyzes the attack of water on the beta-P atom of UDP-2,3-diacylglucosamine.
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Affiliation(s)
- Louis E Metzger
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA
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185
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Floor SN, Jones BN, Hernandez GA, Gross JD. A split active site couples cap recognition by Dcp2 to activation. Nat Struct Mol Biol 2010; 17:1096-101. [PMID: 20711189 PMCID: PMC2933276 DOI: 10.1038/nsmb.1879] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Accepted: 06/18/2010] [Indexed: 01/25/2023]
Abstract
Decapping by Dcp2 is an essential step in 5'-to-3' mRNA decay. In yeast, decapping requires an open-to-closed transition in Dcp2, though the link between closure and catalysis remains elusive. Here we show using NMR that cap binds conserved residues on both the catalytic and regulatory domains of Dcp2. Lesions in the cap-binding site on the regulatory domain reduce the catalytic step by two orders of magnitude and block the formation of the closed state, whereas Dcp1 enhances the catalytic step by a factor of 10 and promotes closure. We conclude that closure occurs during the rate-limiting catalytic step of decapping, juxtaposing the cap-binding region of each domain to form a composite active site. This work suggests a model for regulation of decapping where coactivators trigger decapping by stabilizing a labile composite active site.
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Affiliation(s)
- Stephen N Floor
- Graduate Group in Biophysics, University of California, San Francisco, California, USA
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186
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Soulière MF, Perreault JP, Bisaillon M. Insights into the molecular determinants involved in cap recognition by the vaccinia virus D10 decapping enzyme. Nucleic Acids Res 2010; 38:7599-610. [PMID: 20639534 PMCID: PMC2995054 DOI: 10.1093/nar/gkq628] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Decapping enzymes are required for the removal of the 5′-end m7GpppN cap of mRNAs to allow their decay in cells. While many cap-binding proteins recognize the cap structure via the stacking of the methylated guanosine ring between two aromatic residues, the precise mechanism of cap recognition by decapping enzymes has yet to be determined. In order to get insights into the interaction of decapping enzymes with the cap structure, we studied the vaccinia virus D10 decapping enzyme as a model to investigate the important features for substrate recognition by the enzyme. We demonstrate that a number of chemically modified purines can competitively inhibit the decapping reaction, highlighting the molecular features of the cap structure that are required for recognition by the enzyme, such as the nature of the moiety at positions 2 and 6 of the guanine base. A 3D structural model of the D10 protein was generated which suggests amino acids implicated in cap binding. Consequently, we expressed 17 mutant proteins with amino acid substitutions in the active site of D10 and found that eight are critical for the decapping activity. These data underscore the functional features involved in the non-canonical cap-recognition by the vaccinia virus D10 decapping enzyme.
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Affiliation(s)
- Marie F Soulière
- RNA Group, Département de Biochimie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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187
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Structural basis of UGUA recognition by the Nudix protein CFI(m)25 and implications for a regulatory role in mRNA 3' processing. Proc Natl Acad Sci U S A 2010; 107:10062-7. [PMID: 20479262 DOI: 10.1073/pnas.1000848107] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Human Cleavage Factor Im (CFI(m)) is an essential component of the pre-mRNA 3' processing complex that functions in the regulation of poly(A) site selection through the recognition of UGUA sequences upstream of the poly(A) site. Although the highly conserved 25 kDa subunit (CFI(m)25) of the CFI(m) complex possesses a characteristic alpha/beta/alpha Nudix fold, CFI(m)25 has no detectable hydrolase activity. Here we report the crystal structures of the human CFI(m)25 homodimer in complex with UGUAAA and UUGUAU RNA sequences. CFI(m)25 is the first Nudix protein to be reported to bind RNA in a sequence-specific manner. The UGUA sequence contributes to binding specificity through an intramolecular G:A Watson-Crick/sugar-edge base interaction, an unusual pairing previously found to be involved in the binding specificity of the SAM-III riboswitch. The structures, together with mutational data, suggest a novel mechanism for the simultaneous sequence-specific recognition of two UGUA elements within the pre-mRNA. Furthermore, the mutually exclusive binding of RNA and the signaling molecule Ap(4)A (diadenosine tetraphosphate) by CFI(m)25 suggests a potential role for small molecules in the regulation of mRNA 3' processing.
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188
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Joye IJ, Beliën T, Delcour JA. The first characterised wheat (Triticum aestivum L.) member of the nudix hydrolase family shows specificity for NAD(P)(H) and FAD. J Cereal Sci 2010. [DOI: 10.1016/j.jcs.2010.01.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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189
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Jeyakanthan J, Kanaujia SP, Nishida Y, Nakagawa N, Praveen S, Shinkai A, Kuramitsu S, Yokoyama S, Sekar K. Free and ATP-bound structures of Ap4A hydrolase from Aquifex aeolicus V5. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2010; 66:116-24. [PMID: 20124691 DOI: 10.1107/s0907444909047064] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Accepted: 11/07/2009] [Indexed: 11/10/2022]
Abstract
Asymmetric diadenosine tetraphosphate (Ap(4)A) hydrolases degrade the metabolite Ap(4)A back into ATP and AMP. The three-dimensional crystal structure of Ap(4)A hydrolase (16 kDa) from Aquifex aeolicus has been determined in free and ATP-bound forms at 1.8 and 1.95 A resolution, respectively. The overall three-dimensional crystal structure of the enzyme shows an alphabetaalpha-sandwich architecture with a characteristic loop adjacent to the catalytic site of the protein molecule. The ATP molecule is bound in the primary active site and the adenine moiety of the nucleotide binds in a ring-stacking arrangement equivalent to that observed in the X-ray structure of Ap(4)A hydrolase from Caenorhabditis elegans. Binding of ATP in the active site induces local conformational changes which may have important implications in the mechanism of substrate recognition in this class of enzymes. Furthermore, two invariant water molecules have been identified and their possible structural and/or functional roles are discussed. In addition, modelling of the substrate molecule at the primary active site of the enzyme suggests a possible path for entry and/or exit of the substrate and/or product molecule.
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Affiliation(s)
- Jeyaraman Jeyakanthan
- Life Science Group, National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan
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190
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Nakamura T, Meshitsuka S, Kitagawa S, Abe N, Yamada J, Ishino T, Nakano H, Tsuzuki T, Doi T, Kobayashi Y, Fujii S, Sekiguchi M, Yamagata Y. Structural and dynamic features of the MutT protein in the recognition of nucleotides with the mutagenic 8-oxoguanine base. J Biol Chem 2010; 285:444-52. [PMID: 19864691 PMCID: PMC2804192 DOI: 10.1074/jbc.m109.066373] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 10/14/2009] [Indexed: 11/06/2022] Open
Abstract
Escherichia coli MutT hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP, an event that can prevent the misincorporation of 8-oxoguanine opposite adenine in DNA. Of the several enzymes that recognize 8-oxoguanine, MutT exhibits high substrate specificity for 8-oxoguanine nucleotides; however, the structural basis for this specificity is unknown. The crystal structures of MutT in the apo and holo forms and in the binary and ternary forms complexed with the product 8-oxo-dGMP and 8-oxo-dGMP plus Mn(2+), respectively, were determined. MutT strictly recognizes the overall conformation of 8-oxo-dGMP through a number of hydrogen bonds. This recognition mode revealed that 8-oxoguanine nucleotides are discriminated from guanine nucleotides by not only the hydrogen bond between the N7-H and Odelta (N119) atoms but also by the syn glycosidic conformation that 8-oxoguanine nucleotides prefer. Nevertheless, these discrimination factors cannot by themselves explain the roughly 34,000-fold difference between the affinity of MutT for 8-oxo-dGMP and dGMP. When the binary complex of MutT with 8-oxo-dGMP is compared with the ligand-free form, ordering and considerable movement of the flexible loops surrounding 8-oxo-dGMP in the binary complex are observed. These results indicate that MutT specifically recognizes 8-oxoguanine nucleotides by the ligand-induced conformational change.
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Affiliation(s)
- Teruya Nakamura
- From the Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973
| | - Sachiko Meshitsuka
- the Graduate School of Pharmaceutical Sciences, Osaka University, Suita 565-0871
| | - Seiju Kitagawa
- the Graduate School of Pharmaceutical Sciences, Osaka University, Suita 565-0871
| | - Nanase Abe
- the Graduate School of Pharmaceutical Sciences, Osaka University, Suita 565-0871
| | - Junichi Yamada
- the Graduate School of Pharmaceutical Sciences, Osaka University, Suita 565-0871
| | - Tetsuya Ishino
- the Graduate School of Pharmaceutical Sciences, Osaka University, Suita 565-0871
| | - Hiroaki Nakano
- the Graduate School of Pharmaceutical Sciences, Osaka University, Suita 565-0871
| | - Teruhisa Tsuzuki
- the Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582
| | - Takefumi Doi
- the Graduate School of Pharmaceutical Sciences, Osaka University, Suita 565-0871
| | - Yuji Kobayashi
- the Graduate School of Pharmaceutical Sciences, Osaka University, Suita 565-0871
| | - Satoshi Fujii
- the School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, and
| | | | - Yuriko Yamagata
- From the Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973
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191
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Heyen CA, Tagliabracci VS, Zhai L, Roach PJ. Characterization of mouse UDP-glucose pyrophosphatase, a Nudix hydrolase encoded by the Nudt14 gene. Biochem Biophys Res Commun 2009; 390:1414-8. [PMID: 19896456 PMCID: PMC2798163 DOI: 10.1016/j.bbrc.2009.11.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Accepted: 11/01/2009] [Indexed: 11/16/2022]
Abstract
Recombinant mouse UDP-glucose pyrophosphatase (UGPPase), encoded by the Nudt14 gene, was produced in Escherichia coli and purified close to homogeneity. The enzyme catalyzed the conversion of [beta-(32)P]UDP-glucose to [(32)P]glucose-1-P and UMP, confirming that it hydrolyzed the pyrophosphate of the nucleoside diphosphate sugar to generate glucose-1-P and UMP. The enzyme was also active toward ADP-ribose. Activity is dependent on the presence of Mg(2+) and was greatest at alkaline pH above 8. Kinetic analysis indicated a K(m) of approximately 4mM for UDP-glucose and approximately 0.3mM for ADP-ribose. Based on V(max)/K(m) values, the enzyme was approximately 20-fold more active toward ADP-ribose. UGPPase behaves as a dimer in solution and can be cross-linked to generate a species of M(r) 54,000 from a monomer of 30,000 as judged by SDS-PAGE. The dimerization was not affected by the presence of glucose-1-P or UDP-glucose. Using antibodies raised against the recombinant protein, Western analysis indicated that UGPPase was widely expressed in mouse tissues, including skeletal muscle, liver, kidney, heart, lung, fat, heart and pancreas with a lower level in brain. It was generally present as a doublet when analyzed by SDS-PAGE, suggesting the occurrence of some form of post-translational modification. Efforts to interconvert the species by adding or inhibiting phosphatase activity were unsuccessful, leaving the nature of the modification unknown. Sequence alignments and database searches revealed related proteins in species as distant as Drosophila melanogaster and Caenorhabditis elegans.
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Affiliation(s)
| | | | - Lanmin Zhai
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine
| | - Peter J. Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine
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192
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Gonçalves AMD, Fioravanti E, Stelter M, McSweeney S. Structure of an N-terminally truncated Nudix hydrolase DR2204 from Deinococcus radiodurans. Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:1083-7. [PMID: 19923723 PMCID: PMC2777031 DOI: 10.1107/s1744309109037191] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2009] [Accepted: 09/14/2009] [Indexed: 01/02/2023]
Abstract
Nudix pyrophosphatases are a well represented protein family in the Deinococcus radiodurans genome. These hydrolases, which are known to be enzymatically active towards nucleoside diphosphate derivatives, play a role in cleansing the cell pool of potentially deleterious damage products. Here, the structure of DR2204, the only ADP-ribose pyrophosphatase in the D. radiodurans genome that is known to be active towards flavin adenosine dinucleotide (FAD), is presented at 2.0 angstrom resolution.
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Affiliation(s)
- A. M. D. Gonçalves
- Macromolecular Crystallography Group, European Synchrotron Radiation Facility, BP 220, 6 Rue Jules Horowitz, F-38043 Grenoble, France
| | - E. Fioravanti
- Macromolecular Crystallography Group, European Synchrotron Radiation Facility, BP 220, 6 Rue Jules Horowitz, F-38043 Grenoble, France
| | - M. Stelter
- Macromolecular Crystallography Group, European Synchrotron Radiation Facility, BP 220, 6 Rue Jules Horowitz, F-38043 Grenoble, France
| | - S. McSweeney
- Macromolecular Crystallography Group, European Synchrotron Radiation Facility, BP 220, 6 Rue Jules Horowitz, F-38043 Grenoble, France
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193
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Parrish S, Hurchalla M, Liu SW, Moss B. The African swine fever virus g5R protein possesses mRNA decapping activity. Virology 2009; 393:177-82. [PMID: 19695654 PMCID: PMC3392020 DOI: 10.1016/j.virol.2009.07.026] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 07/23/2009] [Indexed: 01/29/2023]
Abstract
The African Swine Fever Virus (ASFV) encodes a single Nudix enzyme in its genome, termed the g5R protein (g5Rp). Nudix phosphohydrolases cleave a variety of substrates, such as nucleotides and diphosphoinositol polyphosphates. Previously, ASFV g5Rp was shown to hydrolyze diphosphoinositol polyphosphates and GTP, but was unable to cleave methylated mRNA cap analogues. In vaccinia virus (VACV), a distant relative of ASFV, the D9 and D10 Nudix enzymes were shown to cleave the mRNA cap, but only when the cap was attached to an RNA body. Here, we show that recombinant ASFV g5Rp hydrolyzes the mRNA cap when tethered to an RNA moiety, liberating m(7)GDP as a product. Mutations in the Nudix motif abolished mRNA decapping activity, confirming that g5Rp was responsible for cap cleavage. The decapping activity of g5Rp was potently inhibited by excess uncapped RNA but not by methylated cap analogues, suggesting that substrate recognition occurs by RNA binding.
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Affiliation(s)
- Susan Parrish
- McDaniel College, 2 College Hill, Eaton Hall, Room 212, Westminster, MD 21157, USA.
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194
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Doroshenk KA, Crofts AJ, Morris RT, Wyrick JJ, Okita TW. Proteomic Analysis of Cytoskeleton-Associated RNA Binding Proteins in Developing Rice Seed. J Proteome Res 2009; 8:4641-53. [DOI: 10.1021/pr900537p] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Kelly A. Doroshenk
- Institute of Biological Chemistry, School of Molecular Biosciences, Washington State University, Pullman, Washington 99164 and Department of Natural Sciences, Akita International University, 193-2 Okutsubakidai, Tsubakigawa, Yuwa Akita-city, Akita 010-1211, Japan
| | - Andrew J. Crofts
- Institute of Biological Chemistry, School of Molecular Biosciences, Washington State University, Pullman, Washington 99164 and Department of Natural Sciences, Akita International University, 193-2 Okutsubakidai, Tsubakigawa, Yuwa Akita-city, Akita 010-1211, Japan
| | - Robert T. Morris
- Institute of Biological Chemistry, School of Molecular Biosciences, Washington State University, Pullman, Washington 99164 and Department of Natural Sciences, Akita International University, 193-2 Okutsubakidai, Tsubakigawa, Yuwa Akita-city, Akita 010-1211, Japan
| | - John J. Wyrick
- Institute of Biological Chemistry, School of Molecular Biosciences, Washington State University, Pullman, Washington 99164 and Department of Natural Sciences, Akita International University, 193-2 Okutsubakidai, Tsubakigawa, Yuwa Akita-city, Akita 010-1211, Japan
| | - Thomas W. Okita
- Institute of Biological Chemistry, School of Molecular Biosciences, Washington State University, Pullman, Washington 99164 and Department of Natural Sciences, Akita International University, 193-2 Okutsubakidai, Tsubakigawa, Yuwa Akita-city, Akita 010-1211, Japan
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195
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Garza JA, Ilangovan U, Hinck AP, Barnes LD. Kinetic, dynamic, ligand binding properties, and structural models of a dual-substrate specific nudix hydrolase from Schizosaccharomyces pombe. Biochemistry 2009; 48:6224-39. [PMID: 19462967 DOI: 10.1021/bi802266g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Schizosaccharomyces pombe Aps1 is a nudix hydrolase that catalyzes the hydrolysis of both diadenosine 5',5'''-P(1),P(n)-oligophosphates and diphosphoinositol polyphosphates in vitro. Nudix hydrolases act upon a wide variety of substrates, despite having a common 23 amino acid catalytic motif; hence, the residues responsible for substrate specificity are considered to reside outside the common catalytic nudix motif. The specific residues involved in binding each substrate of S. pombe Aps1 are unknown. In this study, we have conducted mutational and kinetic studies in combination with structural homology modeling and NMR spectroscopic analyses to identify potential residues involved in binding each class of substrates. This study demonstrates several major findings with regard to Aps1. First, the determination of the kinetic parameters of K(m) and k(cat) indicated that the initial 31 residues of Aps1 are not involved in substrate binding or catalysis with respect to Ap(6)A. Second, NMR spectroscopic analyses revealed the secondary structure and three dynamic backbone regions, one of which corresponds to a large insert in Aps1 as compared to other putative fungal orthologues. Third, two structural models of Aps1Delta2-19, based on the crystal structures of human DIPP1 and T. thermophilus Ndx1, were generated using homology modeling. The structural models were in excellent agreement with the NMR-derived secondary structure of Aps1Delta2-19. Fourth, NMR chemical shift mapping in conjunction with structural homology models indicated several residues outside the catalytic nudix motif that are involved in specific binding of diphosphoinositol polyphosphate or diadenosine oligophosphate ligands.
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Affiliation(s)
- John A Garza
- Department of Biochemistry, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, USA
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196
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Gunawardana D, Likic VA, Gayler KR. A comprehensive bioinformatics analysis of the Nudix superfamily in Arabidopsis thaliana. Comp Funct Genomics 2009; 2009:820381. [PMID: 19590748 PMCID: PMC2707057 DOI: 10.1155/2009/820381] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2008] [Accepted: 04/16/2009] [Indexed: 11/17/2022] Open
Abstract
Nudix enzymes are a superfamily with a conserved common reaction mechanism that provides the capacity for the hydrolysis of a broad spectrum of metabolites. We used hidden Markov models based on Nudix sequences from the PFAM and PROSITE databases to identify Nudix hydrolases encoded by the Arabidopsis genome. 25 Nudix hydrolases were identified and classified into 11 individual families by pairwise sequence alignments. Intron phases were strikingly conserved in each family. Phylogenetic analysis showed that all multimember families formed monophyletic clusters. Conserved familial sequence motifs were identified with the MEME motif analysis algorithm. One motif (motif 4) was found in three diverse families. All proteins containing motif 4 demonstrated a degree of preference for substrates containing an ADP moiety. We conclude that HMM model-based genome scanning and MEME motif analysis, respectively, can significantly improve the identification and assignment of function of new members of this mechanistically-diverse protein superfamily.
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Affiliation(s)
- D. Gunawardana
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
- School of Biological Sciences, University of Sydney, New South Wales 2006, Australia
| | - V. A. Likic
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - K. R. Gayler
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
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197
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Bi Y, Li H, Fan S, Xia B, Jin C. 1H, 13C and 15N resonance assignments of RNA pyrophosphohydrolase RppH from Escherichia coli. BIOMOLECULAR NMR ASSIGNMENTS 2009; 3:149-151. [PMID: 19636968 DOI: 10.1007/s12104-009-9162-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Accepted: 04/22/2009] [Indexed: 05/28/2023]
Abstract
The mRNA degradation is an important regulatory mechanism which controls gene expression by limiting the number of translation times. Previous studies demonstrated that this process is essential for organisms. Escherichia coli RNA pyrophosphohydrolase (RppH) is an enzyme that triggers mRNA degradation by removing the 5' pyrophosphate, which is a rate-determining step. In order to understand the molecular mechanism of the biological function, the structural information of RppH is required. Herein, we report the resonance assignments of (1)H, (15)N, (13)C atoms of the E. coli RppH.
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Affiliation(s)
- Yunchen Bi
- Beijing Nuclear Magnetic Resonance Center, Peking University, 100871, Beijing, China
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198
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Thorsell AG, Persson C, Gräslund S, Hammarström M, Busam RD, Hallberg BM. Crystal structure of human diphosphoinositol phosphatase 1. Proteins 2009; 77:242-6. [DOI: 10.1002/prot.22489] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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199
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Structure and biological function of the RNA pyrophosphohydrolase BdRppH from Bdellovibrio bacteriovorus. Structure 2009; 17:472-81. [PMID: 19278661 DOI: 10.1016/j.str.2008.12.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 12/08/2008] [Accepted: 12/29/2008] [Indexed: 11/22/2022]
Abstract
Until recently, the mechanism of mRNA decay in bacteria was thought to be different from that of eukaryotes. This paradigm changed with the discovery that RppH (ORF176/NudH/YgdP), an Escherichia coli enzyme that belongs to the Nudix superfamily, is an RNA pyrophosphohydrolase that initiates mRNA decay by cleaving pyrophosphate from the 5'-triphosphate. Here we report the 1.9 Angstroms resolution structure of the Nudix hydrolase BdRppH from Bdellovibrio bacteriovorus, a bacterium that feeds on other Gram-negative bacteria. Based on the structure of the enzyme alone and in complex with GTP-Mg2+, we propose a mode of RNA binding similar to that of the nuclear decapping enzyme from Xenopus laevis, X29. In additional experiments, we show that BdRppH can indeed function in vitro and in vivo as an RNA pyrophosphohydrolase. These findings set the basis for the identification of possible decapping enzymes in other bacteria.
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200
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Characterization of the vaccinia virus D10 decapping enzyme provides evidence for a two-metal-ion mechanism. Biochem J 2009; 420:27-35. [PMID: 19210265 DOI: 10.1042/bj20082296] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Decapping enzymes are required for the removal of the 5'-end cap of mRNAs. These enzymes exhibit a specific hydrolase activity, resulting in cleavage between the alpha- and beta-phosphates of the m7GpppN cap to generate both m7GDP and monophosphorylated RNA products. Decapping enzymes have been found in humans, plants and yeasts, and have been discovered more recently in vaccinia virus (D10 protein). Although experimental evidences are lacking, three-metal- and two-metal-ion mechanisms have been proposed so far for the decapping enzymes. In the present study, we performed a biochemical characterization of the interaction of bivalent cations with the vaccinia virus D10 protein. Synergistic activation of the enzyme was observed in the presence of Mg2+ and Mn2+ ions, suggesting the existence of two metal-ion-binding sites on the D10 protein. Moreover, dual-ligand titration experiments using fluorescence spectroscopy demonstrated the presence of two metal-ion-binding sites on the enzyme. A three-dimensional structural model of the active site of the enzyme was generated which highlighted the importance of three glutamate residues involved in the co-ordination of two metal ions and a water molecule. Mutational analyses confirmed the role of two glutamate residues for the binding of metal ions. We demonstrate that one metal ion is co-ordinated by Glu132, while the second metal ion is co-ordinated by Glu145. Taken together, these results support the proposed two-metal-ion mechanistic model for the D10 decapping enzyme.
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