251
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A method to inhibit the growth of Plasmodium falciparum by double-stranded RNA-mediated gene silencing of helicases. Methods Mol Biol 2010. [PMID: 20225164 DOI: 10.1007/978-1-60327-355-8_27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Malaria in human is caused by four Plasmodium species, with Plasmodium falciparum responsible for the most severe form of the disease. Global resistance to multiple antimalarial drugs is becoming a major challenge in worldwide efforts to control malaria. It is essential to identify new targets. One possible target is helicases, which are important ubiquitous unwinding enzymes required for nucleic acid metabolism and the maintenance of genomic stability. Helicases are motor proteins that use the energy derived from their intrinsic nucleic acid-dependent NTPase activity to unwind the duplex nucleic acid substrate. In this chapter, we study the functional role of helicases in malaria parasite by using specific dsRNA against PfH45, one of the parasite helicases. We describe the methods for Plasmodium falciparum culture, the amplification of specific helicase gene, the construction of specific dsRNA, and the analysis of the effect of dsRNA on parasite growth. Using this approach, we show that helicases are indispensable enzymes, which are required for growth and most probably survival of the malaria parasite.
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252
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Gustafson EA, Wessel GM. DEAD-box helicases: posttranslational regulation and function. Biochem Biophys Res Commun 2010; 395:1-6. [PMID: 20206133 DOI: 10.1016/j.bbrc.2010.02.172] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Accepted: 02/26/2010] [Indexed: 12/22/2022]
Affiliation(s)
- Eric A Gustafson
- Providence Institute of Molecular Oogenesis, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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253
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Köhler D, Schmidt-Gattung S, Binder S. The DEAD-box protein PMH2 is required for efficient group II intron splicing in mitochondria of Arabidopsis thaliana. PLANT MOLECULAR BIOLOGY 2010; 72:459-67. [PMID: 19960362 DOI: 10.1007/s11103-009-9584-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Accepted: 11/24/2009] [Indexed: 05/04/2023]
Abstract
In Arabidopsis thaliana the putative mitochondrial RNA helicases PMH1 and PMH2 are members of the large DEAD-box protein family. Our previous characterization of these proteins revealed that PMH1 and/or PMH2 are part of high molecular weight complexes. Now T-DNA insertion lines were established and characterized for each of these genes. Immunodetection analysis of cell suspension cultures established from pmh1-1 and pmh2-1 mutants revealed that indeed both DEAD-box proteins are detectable in large protein complexes with PMH2 being much more abundant than PMH1. In plants the knockout of PMH2 leads to reduced group II intron splicing efficiency. In addition the steady-state levels of several mature mitochondrial mRNAs are decreased while transcription is not influenced. This molecular phenotype suggests that PMH2 acts at the posttranscriptional level with a potential function as RNA chaperone required for formation or maintenance of complex RNA secondary structures of introns rather than a direct role in splicing. In contrast, the investigation of a pmh1-1 knockout line did not reveal any influence of this protein on processing and abundance of mitochondrial transcripts.
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Affiliation(s)
- Daniela Köhler
- Molekulare Botanik, Universität Ulm, Albert-Einstein-Allee 11, 89069, Ulm, Germany
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254
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Choi YW, Dutta S, Fielding BC, Tan YJ. Expression, purification and preliminary crystallographic analysis of recombinant human DEAD-box polypeptide 5. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:192-4. [PMID: 20124720 DOI: 10.1107/s1744309109052956] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Accepted: 12/09/2009] [Indexed: 11/10/2022]
Abstract
The DEAD-box RNA helicase DDX5 is involved in many aspects of RNA processing and has been implicated in a number of cellular processes involving alteration of RNA secondary structure. The N-terminal region of DDX5, which contains the conserved domain 1 of the DEAD-box helicases, has been cloned and expressed in Escherichia coli and purified. Here, the crystallization and preliminary diffraction analysis of this region is reported. X-ray diffraction data were processed to a resolution of 2.7 A. The crystals belonged to space group I222, with unit-cell parameters a = 66.18, b = 73.80, c = 104.00 A, alpha = beta = gamma = 90 degrees .
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Affiliation(s)
- Yook Wah Choi
- Cancer and Developmental Cell Biology Division, Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), 61 Biopolis Drive, Singapore 138673, Singapore
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255
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Hilbert M, Karow AR, Klostermeier D. The mechanism of ATP-dependent RNA unwinding by DEAD box proteins. Biol Chem 2010; 390:1237-50. [PMID: 19747077 DOI: 10.1515/bc.2009.135] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
DEAD box proteins catalyze the ATP-dependent unwinding of double-stranded RNA (dsRNA). In addition, they facilitate protein displacement and remodeling of RNA or RNA/protein complexes. Their hallmark feature is local destabilization of RNA duplexes. Here, we summarize current data on the DEAD box protein mechanism and present a model for RNA unwinding that integrates recent data on the effect of ATP analogs and mutations on DEAD box protein activity. DEAD box proteins share a conserved helicase core with two flexibly linked RecA-like domains that contain all helicase signature motifs. Variable flanking regions contribute to substrate binding and modulate activity. In the presence of ATP and RNA, the helicase core adopts a compact, closed conformation with extensive interdomain contacts and high affinity for RNA. In the closed conformation, the RecA-like domains form a catalytic site for ATP hydrolysis and a continuous RNA binding site. A kink in the backbone of the bound RNA locally destabilizes the duplex. Rearrangement of this initial complex generates a hydrolysis- and unwinding-competent state. From this complex, the first RNA strand can dissociate. After ATP hydrolysis and phosphate release, the DEAD box protein returns to a low-affinity state for RNA. Dissociation of the second RNA strand and reopening of the cleft in the helicase core allow for further catalytic cycles.
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Affiliation(s)
- Manuel Hilbert
- Biozentrum, Biophysical Chemistry, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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256
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Zolotukhin AS, Uranishi H, Lindtner S, Bear J, Pavlakis GN, Felber BK. Nuclear export factor RBM15 facilitates the access of DBP5 to mRNA. Nucleic Acids Res 2010; 37:7151-62. [PMID: 19786495 PMCID: PMC2790900 DOI: 10.1093/nar/gkp782] [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] [Indexed: 01/29/2023] Open
Abstract
The conserved mRNA export receptor NXF1 (Mex67 in yeast) assembles with messenger ribonucleoproteins (mRNP) in the nucleus and guides them through the nuclear pore complex into the cytoplasm. The DEAD family RNA helicase Dbp5 is essential for nuclear export of mRNA and is thought to dissociate Mex67 from mRNP upon translocation, thereby generating directional passage. However, the molecular mechanism by which Dbp5 recognizes Mex67-containing mRNP is not clear. Here we report that the human NXF1-binding protein RBM15 binds specifically to human DBP5 and facilitates its direct contact with mRNA in vivo. We found that RBM15 is targeted to the nuclear envelope, where it colocalizes extensively with DBP5 and NXF1. Gene silencing of RBM15 leads to cytoplasmic depletion and nuclear accumulation of general mRNA as well as individual endogenous transcripts, indicating that RBM15 is required for efficient mRNA export. We propose a model in which RBM15 acts locally at the nuclear pore complex, by facilitating the recognition of NXF1–mRNP complexes by DBP5 during translocation, thereby contributing to efficient mRNA export.
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Affiliation(s)
- Andrei S Zolotukhin
- Human Retrovirus Pathogenesis Section, National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA
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257
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Zybailov B, Friso G, Kim J, Rudella A, Rodríguez VR, Asakura Y, Sun Q, van Wijk KJ. Large scale comparative proteomics of a chloroplast Clp protease mutant reveals folding stress, altered protein homeostasis, and feedback regulation of metabolism. Mol Cell Proteomics 2010; 8:1789-1810. [PMID: 19423572 DOI: 10.1074/mcp.m900104-mcp200] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The clpr2-1 mutant is delayed in development due to reduction of the chloroplast ClpPR protease complex. To understand the role of Clp proteases in plastid biogenesis and homeostasis, leaf proteomes of young seedlings of clpr2-1 and wild type were compared using large scale mass spectrometry-based quantification using an LTQ-Orbitrap and spectral counting with significance determined by G-tests. Virtually only chloroplast-localized proteins were significantly affected, indicating that the molecular phenotype was confined to the chloroplast. A comparative chloroplast stromal proteome analysis of fully developed plants was used to complement the data set. Chloroplast unfoldase ClpB3 was strongly up-regulated in both young and mature leaves, suggesting widespread and persistent protein folding stress. The importance of ClpB3 in the clp2-1 mutant was demonstrated by the observation that a CLPR2 and CLPB3 double mutant was seedling-lethal. The observed up-regulation of chloroplast chaperones and protein sorting components further illustrated destabilization of protein homeostasis. Delayed rRNA processing and up-regulation of a chloroplast DEAD box RNA helicase and polynucleotide phosphorylase, but no significant change in accumulation of ribosomal subunits, suggested a bottleneck in ribosome assembly or RNA metabolism. Strong up-regulation of a chloroplast translational regulator TypA/BipA GTPase suggested a specific response in plastid gene expression to the distorted homeostasis. The stromal proteases PreP1,2 were up-regulated, likely constituting compensation for reduced Clp protease activity and possibly shared substrates between the ClpP and PreP protease systems. The thylakoid photosynthetic apparatus was decreased in the seedlings, whereas several structural thylakoid-associated plastoglobular proteins were strongly up-regulated. Two thylakoid-associated reductases involved in isoprenoid and chlorophyll synthesis were up-regulated reflecting feedback from rate-limiting photosynthetic electron transport. We discuss the quantitative proteomics data and the role of Clp proteolysis using a "systems view" of chloroplast homeostasis and metabolism and provide testable hypotheses and putative substrates to further determine the significance of Clp-driven proteolysis.
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Affiliation(s)
- Boris Zybailov
- Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA
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258
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LGP2 is a positive regulator of RIG-I- and MDA5-mediated antiviral responses. Proc Natl Acad Sci U S A 2010; 107:1512-7. [PMID: 20080593 DOI: 10.1073/pnas.0912986107] [Citation(s) in RCA: 480] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
RNA virus infection is recognized by retinoic acid-inducible gene (RIG)-I-like receptors (RLRs), RIG-I, and melanoma differentiation-associated gene 5 (MDA5) in the cytoplasm. RLRs are comprised of N-terminal caspase-recruitment domains (CARDs) and a DExD/H-box helicase domain. The third member of the RLR family, LGP2, lacks any CARDs and was originally identified as a negative regulator of RLR signaling. In the present study, we generated mice lacking LGP2 and found that LGP2 was required for RIG-I- and MDA5-mediated antiviral responses. In particular, LGP2 was essential for type I IFN production in response to picornaviridae infection. Overexpression of the CARDs from RIG-I and MDA5 in Lgp2(-/-) fibroblasts activated the IFN-beta promoter, suggesting that LGP2 acts upstream of RIG-I and MDA5. We further examined the role of the LGP2 helicase domain by generating mice harboring a point mutation of Lys-30 to Ala (Lgp2 (K30A/K30A)) that abrogated the LGP2 ATPase activity. Lgp2 (K30A/K30A) dendritic cells showed impaired IFN-beta productions in response to various RNA viruses to extents similar to those of Lgp2(-/-) cells. Lgp2(-/-) and Lgp2 (K30A/K30A) mice were highly susceptible to encephalomyocarditis virus infection. Nevertheless, LGP2 and its ATPase activity were dispensable for the responses to synthetic RNA ligands for MDA5 and RIG-I. Taken together, the present data suggest that LGP2 facilitates viral RNA recognition by RIG-I and MDA5 through its ATPase domain.
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259
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Abstract
Helicases are essential enzymes involved in all aspects of nucleic acid metabolism including DNA replication, repair, recombination, transcription, ribosome biogenesis and RNA processing, translation, and decay. They occur in vivo as part of molecular complexes that include the components required for each specific step of nucleic acid metabolism. The role of the helicases is to utilize the energy derived from nucleoside triphosphate hydrolysis to translocate along nucleic acid strands, unwind/separate the helical structure of double-stranded nucleic acid, and, in some cases, disrupt protein-nucleic acid interactions. Because of their essential function, helicases are ubiquitous and evolutionary conserved proteins. This chapter briefly highlights helicase structure and activities and provides examples of the helicases involved in nucleic acid metabolism.
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Affiliation(s)
- Mohamed Abdelhaleem
- Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada
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260
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261
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Bohnsack MT, Martin R, Granneman S, Ruprecht M, Schleiff E, Tollervey D. Prp43 bound at different sites on the pre-rRNA performs distinct functions in ribosome synthesis. Mol Cell 2009; 36:583-92. [PMID: 19941819 PMCID: PMC2806949 DOI: 10.1016/j.molcel.2009.09.039] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Revised: 07/17/2009] [Accepted: 09/04/2009] [Indexed: 11/12/2022]
Abstract
Yeast ribosome synthesis requires 19 different RNA helicases, but none of their pre-rRNA-binding sites were previously known, making their precise functions difficult to determine. Here we identify multiple binding sites for the helicase Prp43 in the 18S and 25S rRNA regions of pre-rRNAs, using UV crosslinking. Binding in 18S was predominantly within helix 44, close to the site of 18S 3′ cleavage, in which Prp43 is functionally implicated. Four major binding sites were identified in 25S, including helix 34. In strains depleted of Prp43 or expressing only catalytic point mutants, six snoRNAs that guide modifications close to helix 34 accumulated on preribosomes, implicating Prp43 in their release, whereas other snoRNAs showed reduced preribosome association. Prp43 was crosslinked to snoRNAs that target sequences close to its binding sites, indicating direct interactions. We propose that Prp43 acts on preribosomal regions surrounding each binding site, with distinct functions at different locations.
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Affiliation(s)
- Markus T Bohnsack
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, UK.
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262
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Abstract
RNA interference (RNAi) is a regulatory gene silencing system found in nearly all eukaryotic organisms that employs small RNAs, typically 20-25 nucleotides long, to target complementary sequences found in mRNAs. RNA helicases use ATP to unwind double-stranded RNA (dsRNA), and are known to participate at nearly every level of RNA metabolism. A multitude of RNA helicases have been isolated from screens for essential RNAi factors, and even the earliest models of the RNAi pathway have presumed an RNA helicase to function at the level of small RNA duplex unwinding. However, while many components that function in RNAi have been uncovered and characterized, the exact placement in the pathway and ascription of a specific biochemical function of an RNA helicase in RNAi remains elusive. Recent studies have delved deeper into the precise role of some RNA helicases. Surprisingly, these studies have revealed nontraditional roles, which may not even require the helicase activity. Such findings suggest that RNA helicases regulate gene silencing at nearly every level of the RNAi pathways.
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Affiliation(s)
- Aaron M Ambrus
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
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263
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Tsai-Morris CH, Sheng Y, Gutti RK, Tang PZ, Dufau ML. Gonadotropin-regulated testicular RNA helicase (GRTH/DDX25): a multifunctional protein essential for spermatogenesis. ACTA ACUST UNITED AC 2009; 31:45-52. [PMID: 19875492 DOI: 10.2164/jandrol.109.008219] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Male germ cell maturation is governed by the expression of specific protein(s) in a precise temporal sequence during development. Gonadotropin-regulated testicular RNA helicase (GRTH/DDX25), a member of the Glu-Asp-Ala-Glu (DEAD)-box protein family, is a testis-specific gonadotropin/androgen-regulated RNA helicase that is present in germ cells (meiotic spermatocytes and round spermatids) and Leydig cells. GRTH is essential for completion of spermatogenesis as a posttranscriptional regulator of relevant genes during germ cell development. Male mice lacking GRTH are sterile with spermatogenic arrest due to failure of round spermatids to elongate, where striking structural changes and reduction in size of chromatoid bodies are observed. GRTH also plays a central role in preventing germ cell apoptosis. In addition to its inherent helicase unwinding/adenosine triphosphatase activities, GRTH binds to specific mRNAs as an integral component of ribonuclear protein particles. As a shuttle protein, GRTH transports target mRNAs from nucleus to the cytoplasm for storage in chromatoid bodies of spermatids, where they await translation during spermatogenesis. GRTH is also associated with polyribosomes to regulate target gene translation. The finding of a missense mutation associated with male infertility, where its expression associates with loss of GRTH phosphorylation, supports the relevance of GRTH to human germ cell development. We conclude that the mammalian GRTH/DDX25 is a multifunctional RNA helicase that is an essential regulator of spermatogenesis and is highly relevant for studies of male infertility and contraception.
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Affiliation(s)
- Chon-Hwa Tsai-Morris
- Section onMolecular Endocrinology, Program in Developmental Endocrinology and Genetics, Eunice KennedyShriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA.
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264
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Szczesny RJ, Borowski LS, Brzezniak LK, Dmochowska A, Gewartowski K, Bartnik E, Stepien PP. Human mitochondrial RNA turnover caught in flagranti: involvement of hSuv3p helicase in RNA surveillance. Nucleic Acids Res 2009; 38:279-98. [PMID: 19864255 PMCID: PMC2800237 DOI: 10.1093/nar/gkp903] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The mechanism of human mitochondrial RNA turnover and surveillance is still a matter of debate. We have obtained a cellular model for studying the role of hSuv3p helicase in human mitochondria. Expression of a dominant-negative mutant of the hSUV3 gene which encodes a protein with no ATPase or helicase activity results in perturbations of mtRNA metabolism and enables to study the processing and degradation intermediates which otherwise are difficult to detect because of their short half-lives. The hSuv3p activity was found to be necessary in the regulation of stability of mature, properly formed mRNAs and for removal of the noncoding processing intermediates transcribed from both H and L-strands, including mirror RNAs which represent antisense RNAs transcribed from the opposite DNA strand. Lack of hSuv3p function also resulted in accumulation of aberrant RNA species, molecules with extended poly(A) tails and degradation intermediates truncated predominantly at their 3′-ends. Moreover, we present data indicating that hSuv3p co-purifies with PNPase; this may suggest participation of both proteins in mtRNA metabolism.
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Affiliation(s)
- Roman J Szczesny
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
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265
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Translational control during early development. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 90:211-54. [PMID: 20374743 DOI: 10.1016/s1877-1173(09)90006-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Translational control of specific messenger RNAs, which themselves are often asymmetrically localized within the cytoplasm of a cell, underlies many events in germline development, and in embryonic axis specification. This comprehensive, but by no means exhaustive, review attempts to present a picture of the present state of knowledge about mechanisms underlying mRNA localization and translational control of specific mRNAs that are mediated by trans-acting protein factors. While RNA localization and translational control are widespread in evolution and have been studied in many experimental systems, this article will focus mainly on three particularly well-characterized systems: Drosophila, Caenorhabditis elegans, and Xenopus. In keeping with the overall theme of this volume, instances in which translational control factors have been linked to human disease states will also be discussed.
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266
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Del Campo M, Lambowitz AM. Structure of the Yeast DEAD box protein Mss116p reveals two wedges that crimp RNA. Mol Cell 2009; 35:598-609. [PMID: 19748356 DOI: 10.1016/j.molcel.2009.07.032] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Revised: 06/22/2009] [Accepted: 07/16/2009] [Indexed: 11/25/2022]
Abstract
The yeast DEAD box protein Mss116p is a general RNA chaperone that functions in mitochondrial group I and II intron splicing, translational activation, and RNA end processing. Here we determined high-resolution X-ray crystal structures of Mss116p complexed with an RNA oligonucleotide and ATP analogs AMP-PNP, ADP-BeF(3)(-), or ADP-AlF(4)(-). The structures show the entire helicase core acting together with a functionally important C-terminal extension. In all structures, the helicase core is in a closed conformation with a wedge alpha helix bending RNA 3' of the central bound nucleotides, as in previous DEAD box protein structures. Notably, Mss116p's C-terminal extension also bends RNA 5' of the central nucleotides, resulting in RNA crimping. Despite reported functional differences, we observe few structural changes in ternary complexes with different ATP analogs. The structures constrain models of DEAD box protein function and reveal a strand separation mechanism in which a protein uses two wedges to act as a molecular crimper.
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Affiliation(s)
- Mark Del Campo
- Institute for Cellular and Molecular Biology, University of Texas at Austin, 78712, USA
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267
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Markov DA, Savkina M, Anikin M, Del Campo M, Ecker K, Lambowitz AM, De Gnore JP, McAllister WT. Identification of proteins associated with the yeast mitochondrial RNA polymerase by tandem affinity purification. Yeast 2009; 26:423-40. [PMID: 19536766 PMCID: PMC2896726 DOI: 10.1002/yea.1672] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The abundance of mitochondrial (mt) transcripts varies under different conditions, and is thought to depend upon rates of transcription initiation, transcription termination/attenuation and RNA processing/degradation. The requirement to maintain the balance between RNA synthesis and processing may involve coordination between these processes; however, little is known about factors that regulate the activity of mtRNA polymerase (mtRNAP). Recent attempts to identify mtRNAP–protein interactions in yeast by means of a generalized tandem affinity purification (TAP) protocol were not successful, most likely because they involved a C-terminal mtRNAP–TAP fusion (which is incompatible with mtRNAP function) and because of the use of whole-cell solubilization protocols that did not preserve the integrity of mt protein complexes. Based upon the structure of T7 RNAP (to which mtRNAPs show high sequence similarity), we identified positions in yeast mtRNAP that allow insertion of a small affinity tag, confirmed the mature N-terminus, constructed a functional N-terminal TAP–mtRNAP fusion, pulled down associated proteins, and identified them by LC–MS–MS. Among the proteins found in the pull-down were a DEAD-box protein (Mss116p) and an RNA-binding protein (Pet127p). Previous genetic experiments suggested a role for these proteins in linking transcription and RNA degradation, in that a defect in the mt degradadosome could be suppressed by overexpression of either of these proteins or, independently, by mutations in either mtRNAP or its initiation factor Mtf1p. Further, we found that Mss116p inhibits transcription by mtRNAP in vitro in a steady-state reaction. Our results support the hypothesis that Mss116p and Pet127p are involved in modulation of mtRNAP activity. Copyright © 2009 John Wiley & Sons, Ltd.
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Affiliation(s)
- Dmitriy A Markov
- Departments of Cell Biology, University of Medicine and Dentistry of New Jersey, Stratford, USA.
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268
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Mrd1p is required for release of base-paired U3 snoRNA within the preribosomal complex. Mol Cell Biol 2009; 29:5763-74. [PMID: 19704003 DOI: 10.1128/mcb.00428-09] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In eukaryotes, ribosomes are made from precursor rRNA (pre-rRNA) and ribosomal proteins in a maturation process that requires a large number of snoRNPs and processing factors. A fundamental problem is how the coordinated and productive folding of the pre-rRNA and assembly of successive pre-rRNA-protein complexes is achieved cotranscriptionally. The conserved protein Mrd1p, which contains five RNA binding domains (RBDs), is essential for processing events leading to small ribosomal subunit synthesis. We show that full function of Mrd1p requires all five RBDs and that the RBDs are functionally distinct and needed during different steps in processing. Mrd1p mutations trap U3 snoRNA in pre-rRNP complexes both in base-paired and non-base-paired interactions. A single essential RBD, RBD5, is involved in both types of interactions, but its conserved RNP1 motif is not needed for releasing the base-paired interactions. RBD5 is also required for the late pre-rRNP compaction preceding A(2) cleavage. Our results suggest that Mrd1p modulates successive conformational rearrangements within the pre-rRNP that influence snoRNA-pre-rRNA contacts and couple U3 snoRNA-pre-rRNA remodeling and late steps in pre-rRNP compaction that are essential for cleavage at A(0) to A(2). Mrd1p therefore coordinates key events in biosynthesis of small ribosome subunits.
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269
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Abstract
The possibility that women produce new oocytes post-natally as part of the normal physiological function of the ovary is currently under investigation. Post-natal production of oocyte-like cells has been detected under experimental conditions in the mouse. Although these cells have many characteristics of oocytes, their potential to mature to fertilization-competence was unproven. Zou et al. (Production of offspring from a germline stem cell line derived from neonatal ovaries. Nat Cell Biol 2009;11:631-636) made use of a striking cell isolation and culture strategy to establish cultures of proliferative germ cells from both newborn and adult ovaries. Their cells, referred to as female germline stem cells (FGSCs), proliferate long-term in culture and accept and maintain expression of a transgenic marker, green fluorescent protein. When delivered to the ovaries of conditioned mice, transgene-bearing FGSC engrafted, were enclosed within follicles, and when host females were mated, transgenic offspring were produced. That proliferative female germ cells capable of giving rise to offspring were detected in adult ovaries poses the question of whether they have a physiological role. Here, we discuss Zou et al.'s data in terms of our current understanding of mouse ovarian physiology, and how this may relate to human reproductive biology and the treatment of ovarian dysfunction.
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270
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Chung E, Cho CW, Yun BH, Choi HK, So HA, Lee SW, Lee JH. Molecular cloning and characterization of the soybean DEAD-box RNA helicase gene induced by low temperature and high salinity stress. Gene 2009; 443:91-9. [PMID: 19463922 DOI: 10.1016/j.gene.2009.05.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 04/24/2009] [Accepted: 05/09/2009] [Indexed: 10/20/2022]
Abstract
A novel gene encoding a DEAD-box RNA helicase designated as GmRH was isolated from soybean. Amino acid sequence alignment and phylogenetic tree analysis revealed a close relationship between GmRH and other orthologous DEAD-box RNA helicases from other plant species. Structural motif analysis revealed that the bipartite lysine rich nuclear localization signal (NLS) is present in the N-terminal variable region of GmRH and that there are ten conserved motifs found in DEAD-box RNA helicase proteins. Southern blot analysis revealed the presence of 2 copies of GmRH in the soybean genome. Northern blot analysis demonstrated that the RNA expression of the GmRH was induced during low temperature or high salinity stress, but not by the exogenous application of abscisic acid or drought stress. Subcellular localization studies showed that GmRH((1-355))-GFP is localized in the nucleus, whereas GmRH((130-355))-GFP is localized both in the cytoplasm and in the nucleus. This provides the evidence that the N-terminal region predicted as NLS is essential for nuclear targeting of the GmRH protein in the plant cell. Purified GST-GmRH recombinant protein was shown to unwind dsRNA independent of ATP in vitro. Here, we propose that GmRH plays an important role in RNA processing during low temperature and high salinity stresses in plants.
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Affiliation(s)
- Eunsook Chung
- BK21 Center for Silver-Bio Industrialization, College of Natural Resources and Life Science, Dong-A University, Busan 604-714, Republic of Korea
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271
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Del Campo M, Lambowitz AM. Crystallization and preliminary X-ray diffraction of the DEAD-box protein Mss116p complexed with an RNA oligonucleotide and AMP-PNP. Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:832-5. [PMID: 19652352 DOI: 10.1107/s1744309109027225] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Accepted: 07/10/2009] [Indexed: 12/13/2022]
Abstract
The Saccharomyces cerevisiae DEAD-box protein Mss116p is a general RNA chaperone which functions in mitochondrial group I and group II intron splicing, translation and RNA-end processing. For crystallization trials, full-length Mss116p and a C-terminally truncated protein (Mss116p/Delta598-664) were overproduced in Escherichia coli and purified to homogeneity. Mss116p exhibited low solubility in standard solutions (< or =1 mg ml(-1)), but its solubility could be increased by adding 50 mM L-arginine plus 50 mM L-glutamate and 50% glycerol to achieve concentrations of approximately 10 mg ml(-1). Initial crystals were obtained by the microbatch method in the presence of a U(10) RNA oligonucleotide and the ATP analog AMP-PNP and were then improved by using seeding and sitting-drop vapor diffusion. A cryocooled crystal of Mss116p/Delta598-664 in complex with AMP-PNP and U(10) belonged to space group P2(1)2(1)2, with unit-cell parameters a = 88.54, b = 126.52, c = 55.52 A, and diffracted X-rays to beyond 1.9 A resolution using synchrotron radiation from sector 21 at the Advanced Photon Source.
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Affiliation(s)
- Mark Del Campo
- Institute for Cellular and Molecular Biology, Department of Chemistry and Biochemistry, and Section of Molecular Genetics and Microbiology, School of Biological Sciences, University of Texas at Austin, Austin, TX 78712, USA
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272
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Tartakoff AM, Tao T. Comparative and evolutionary aspects of macromolecular translocation across membranes. Int J Biochem Cell Biol 2009; 42:214-29. [PMID: 19643202 DOI: 10.1016/j.biocel.2009.07.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 07/21/2009] [Accepted: 07/21/2009] [Indexed: 01/10/2023]
Abstract
Membrane barriers preserve the integrity of organelles of eukaryotic cells, yet the genesis and ongoing functions of the same organelles requires that their limiting membranes allow import and export of selected macromolecules. Multiple distinct mechanisms are used for this purpose, only some of which have been traced to prokaryotes. Some can accommodate both monomeric and also large heterooligomeric cargoes. The best characterized of these is nucleocytoplasmic transport. This synthesis compares the unidirectional and bidirectional mechanisms of macromolecular transport of the endoplasmic reticulum, mitochondria, peroxisomes and the nucleus, calls attention to the powerful experimental approaches which have been used for their elucidation, discusses their regulation and evolutionary origins, and highlights relatively unexplored areas.
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Affiliation(s)
- Alan M Tartakoff
- Department of Pathology & Cell Biology Program, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA.
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273
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Bodzon-Kulakowska A, Suder P, Mak P, Bierczynska-Krzysik A, Lubec G, Walczak B, Kotlinska J, Silberring J. Proteomic analysis of striatal neuronal cell cultures after morphine administration. J Sep Sci 2009; 32:1200-10. [PMID: 19296477 DOI: 10.1002/jssc.200800464] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Using primary neuronal cell culture assays, combined with 2-D gel electrophoresis and capillary LC-MS, we identified differences in proteomes between control and morphine-treated cells. Statistically significant differences were observed among 26 proteins. Nineteen of them were up-regulated, while seven were down-regulated in morphine-treated cell populations. The identified proteins belong to classes involved in energy metabolism, associated with oxidative stress, linked with protein biosynthesis, cytoskeletal ones, and chaperones. The detected proteins demand further detailed studies of their biological roles in morphine addiction. It is crucial to confirm observed processes in vivo in order to reveal the nature and importance of the biological effect of proteome changes after morphine administration. Further investigations may lead to the discovery of new proteome-based effects of morphine on living organisms.
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Affiliation(s)
- Anna Bodzon-Kulakowska
- Neurobiochemistry Department, Faculty of Chemistry, Jagiellonian University, Krakow, Poland
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274
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Identifying concerted evolution and gene conversion in mammalian gene pairs lasting over 100 million years. BMC Evol Biol 2009; 9:156. [PMID: 19583854 PMCID: PMC2720389 DOI: 10.1186/1471-2148-9-156] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Accepted: 07/07/2009] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Concerted evolution occurs in multigene families and is characterized by stretches of homogeneity and higher sequence similarity between paralogues than between orthologues. Here we identify human gene pairs that have undergone concerted evolution, caused by ongoing gene conversion, since at least the human-mouse divergence. Our strategy involved the identification of duplicated genes with greater similarity within a species than between species. These genes were required to be present in multiple mammalian genomes, suggesting duplication early in mammalian divergence. To eliminate genes that have been conserved due to strong purifying selection, our analysis also required at least one intron to have retained high sequence similarity between paralogues. RESULTS We identified three human gene pairs undergoing concerted evolution (BMP8A/B, DDX19A/B, and TUBG1/2). Phylogenetic investigations reveal that in each case the duplication appears to have occurred prior to eutherian mammalian radiation, with exactly two paralogues present in all examined species. This indicates that all three gene duplication events were established over 100 million years ago. CONCLUSION The extended duration of concerted evolution in multiple distant lineages suggests that there has been prolonged homogenization of specific segments within these gene pairs. Although we speculate that selection for homogenization could have been utilized in order to maintain crucial homo- or hetero- binding domains, it remains unclear why gene conversion has persisted for such extended periods of time. Through these analyses, our results demonstrate additional examples of a process that plays a definite, although unspecified, role in molecular evolution.
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275
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Spp382p interacts with multiple yeast splicing factors, including possible regulators of Prp43 DExD/H-Box protein function. Genetics 2009; 183:195-206. [PMID: 19581443 DOI: 10.1534/genetics.109.106955] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Prp43p catalyzes essential steps in pre-mRNA splicing and rRNA biogenesis. In splicing, Spp382p stimulates the Prp43p helicase to dissociate the postcatalytic spliceosome and, in some way, to maintain the integrity of the spliceosome assembly. Here we present a dosage interference assay to identify Spp382p-interacting factors by screening for genes that when overexpressed specifically inhibit the growth of a conditional lethal prp38-1 spliceosome assembly mutant in the spp382-1 suppressor background. Identified, among others, are genes encoding the established splicing factors Prp8p, Prp9p, Prp11p, Prp39p, and Yhc1p and two poorly characterized proteins with possible links to splicing, Sqs1p and Cwc23p. Sqs1p copurifies with Prp43p and is shown to bind Prp43p and Spp382p in the two-hybrid assay. Overexpression of Sqs1p blocks pre-mRNA splicing and inhibits Prp43p-dependent steps in rRNA processing. Increased Prp43p levels buffer Sqs1p cytotoxicity, providing strong evidence that the Prp43p DExD/H-box protein is a target of Sqs1p. Cwc23p is the only known yeast splicing factor with a DnaJ motif characteristic of Hsp40-like chaperones. We show that similar to SPP382, CWC23 activity is critical for efficient pre-mRNA splicing and intron metabolism yet, surprisingly, this activity does not require the canonical DnaJ/Hsp40 motif. These and related data establish the value of this dosage interference assay for finding genes that alter cellular splicing and define Sqs1p and Cwc23p as prospective modulators of Spp382p-stimuated Prp43p function.
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276
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Hage R, Tung L, Du H, Stands L, Rosbash M, Chang TH. A targeted bypass screen identifies Ynl187p, Prp42p, Snu71p, and Cbp80p for stable U1 snRNP/Pre-mRNA interaction. Mol Cell Biol 2009; 29:3941-52. [PMID: 19451230 PMCID: PMC2704744 DOI: 10.1128/mcb.00384-09] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 04/22/2009] [Accepted: 05/07/2009] [Indexed: 11/20/2022] Open
Abstract
To understand how DEXD/H-box proteins recognize and interact with their cellular substrates, we have been studying Prp28p, a DEXD/H-box splicing factor required for switching the U1 snRNP with the U6 snRNP at the precursor mRNA (pre-mRNA) 5' splice site. We previously demonstrated that the requirement for Prp28p can be eliminated by mutations that alter either the U1 snRNA or the U1C protein, suggesting that both are targets of Prp28p. Inspired by this finding, we designed a bypass genetic screen to specifically search for additional, novel targets of Prp28p. The screen identified Prp42p, Snu71p, and Cbp80p, all known components of commitment complexes, as well as Ynl187p, a protein of uncertain function. To examine the role of Ynl187p in splicing, we carried out extensive genetic and biochemical analysis, including chromatin immunoprecipitation. Our data suggest that Ynl187p acts in concert with U1C and Cbp80p to help stabilize the U1 snRNP-5' splice site interaction. These findings are discussed in the context of DEXD/H-box proteins and their role in vivo as well as the potential need for more integral U1-snRNP proteins in governing the fungal 5' splice site RNA-RNA interaction compared to the number of U1 snRNP proteins needed by metazoans.
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Affiliation(s)
- Rosemary Hage
- Department of Molecular Genetics, The Ohio State University, 484 West 12th Ave., Columbus, OH 43210, USA
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277
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Dang Y, Low WK, Xu J, Gehring NH, Dietz HC, Romo D, Liu JO. Inhibition of nonsense-mediated mRNA decay by the natural product pateamine A through eukaryotic initiation factor 4AIII. J Biol Chem 2009; 284:23613-21. [PMID: 19570977 DOI: 10.1074/jbc.m109.009985] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Nonsense-mediated mRNA decay (NMD) in mammalian cells is a key mechanism for the removal of mRNA containing premature stop codons and is mediated by the coordinated function of numerous proteins that dynamically associate with the exon junction complex. The information communicated by these interactions and the functional consequences from a mechanistic perspective, however, are not completely documented. Herein, we report that the natural product pateamine A (PatA) is capable of inhibiting NMD through direct interaction with eIF4AIII, which is independent of its inhibition of translation initiation. Furthermore, we have characterized the mechanisms by which PatA and cycloheximide modulate NMD. Unlike CHX, PatA was found to inhibit NMD by a novel mechanism that is independent of the phosphorylation of Up-frameshift protein 1.
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Affiliation(s)
- Yongjun Dang
- Department of Pharmacology, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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278
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Kosowski TR, Keys HR, Quan TK, Ruby SW. DExD/H-box Prp5 protein is in the spliceosome during most of the splicing cycle. RNA (NEW YORK, N.Y.) 2009; 15:1345-62. [PMID: 19451545 PMCID: PMC2704087 DOI: 10.1261/rna.1065209] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The DExD/H-box Prp5 protein (Prp5p) is an essential, RNA-dependent ATPase required for pre-spliceosome formation during nuclear pre-mRNA splicing. In order to understand how this protein functions, we used in vitro, biochemical assays to examine its association with the spliceosome from Saccharomyces cerevisiae. GST-Prp5p in splicing assays pulls down radiolabeled pre-mRNA as well as splicing intermediates and lariat product, but reduced amounts of spliced mRNA. It cosediments with active spliceosomes isolated by glycerol gradient centrifugation. In ATP-depleted extracts, GST-Prp5p associates with pre-mRNA even in the absence of spliceosomal snRNAs. Maximal selection in either the presence or absence of ATP requires a pre-mRNA with a functional intron. Prp5p is present in the commitment complex and functions in subsequent pre-spliceosome formation. Reduced Prp5p levels decrease levels of commitment, pre-spliceosomal and spliceosomal complexes. Thus Prp5p is most likely an integral component of the spliceosome, being among the first splicing factors associating with pre-mRNA and remaining until spliceosome disassembly. The results suggest a model in which Prp5p recruits the U2 snRNP to pre-mRNA in the commitment complex and then hydrolyzes ATP to promote stable association of U2 in the pre-spliceosome. They also suggest that Prp5p could have multiple ATP-independent and ATP-dependent functions at several stages of the splicing cycle.
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Affiliation(s)
- Tomasz R Kosowski
- Department of Molecular Genetics and Microbiology, Albuquerque, New Mexico 87131, USA
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279
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Shen H. UAP56- a key player with surprisingly diverse roles in pre-mRNA splicing and nuclear export. BMB Rep 2009; 42:185-8. [PMID: 19403039 DOI: 10.5483/bmbrep.2009.42.4.185] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcripts contain introns that are usually removed from premessenger RNA (MRNA) in the process of pre-mRNA splicing. After splicing, the mature RNA is exported from the nucleus to the cytoplasm. The splicing and export processes are coupled. UAP56 protein, which is ubiquitously present in organisms from yeasts to humans, is a DExD/H-box family RNA helicase that is an essential splicing factor with various functions in the prespliceosome assembly and mature spliceosome assembly. Collective evidence indicates that UAP56 has an essential role in mRNA nuclear export. This mini-review summarizes recent evidence for the role of UAP56 in pre-mRNA splicing and nuclear export.
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Affiliation(s)
- Haihong Shen
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju, Korea.
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280
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Linder P, Owttrim GW. Plant RNA helicases: linking aberrant and silencing RNA. TRENDS IN PLANT SCIENCE 2009; 14:344-52. [PMID: 19446493 DOI: 10.1016/j.tplants.2009.03.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Revised: 03/11/2009] [Accepted: 03/17/2009] [Indexed: 05/06/2023]
Abstract
RNA helicases are ATPases that are capable of rearranging RNA and ribonucleoprotein (RNP) structure, and they can potentially function in any aspect of RNA metabolism. The RNA helicase gene family of plant genomes is larger and more diverse than genome families observed in other systems and provides an ideal model for investigation of the physiological importance of RNA secondary structure rearrangement in plant development. Numerous plant RNA helicases are associated with a variety of physiological functions, but this review will focus on the thirteen RNA helicases associated with the metabolism of aberrant and silencing RNAs. The results emphasize the crucial role RNA helicase activity has in the regulation of mRNA quality control and gene expression in plant development.
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Affiliation(s)
- Patrick Linder
- Department of Microbiology and Molecular Medicine, CMU, 1 Rue Michel Servet, CH-1211 Geneve 4, Switzerland
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281
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Rosner A, Moiseeva E, Rinkevich Y, Lapidot Z, Rinkevich B. Vasa and the germ line lineage in a colonial urochordate. Dev Biol 2009; 331:113-28. [PMID: 19406116 DOI: 10.1016/j.ydbio.2009.04.025] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 03/22/2009] [Accepted: 04/22/2009] [Indexed: 01/13/2023]
Abstract
Germ cell sequestering in Animalia is enlightened by either, launching true germ line along epigenetic or preformistic modes of development, or by somatic embryogenesis, where no true germ line is set aside. The research on germ line-somatic tissue segregation is of special relevancy to colonial organisms like botryllid ascidians that reconstruct, on a weekly basis, completely new sets of male and female gonads in newly formed somatic tissues. By sequencing and evaluating expression patterns of BS-Vasa, the Botryllus schlosseri orthologue of Vasa, in sexually mature and asexual colonies during blastogenesis, we have demonstrated that the BS-Vasa mRNA and protein are not expressed exclusively in germ cell lineages, but appeared in cells repeatedly emerging de novo in the colony, independently of its sexual state. In addition, we recorded an immediate Vasa response to cellular stress (UV irradiation) indicating additional functions to its germ line assignments. To confirm germ lineage exclusivity, we examined the expression of three more stem cell markers (BS-Pl10, Bl-piwi and Oct4). Vasa co-expression with Pl10 and Oct4 was detected in germ line derivatives and with Bl-piwi in somatic tissues. Presumptive primordial germ cells (PGC-like cells), that are Vasa(+)/Pl10(+)/Oct4(+) and 6-12 microm in diameter, were first detected in wrapped-tail embryos, in oozooids, in sexual/asexual colonies, within a newly identified PGC niche termed as 'budlet niche', and in circulating blood borne cells, indicating epigenetic embryogenesis. Alternatively, BS-Vasa co-expression with piwi orthologue, an omnipresent bona fide stemness flag, in non germ line cell populations, may indicate germ cell neogenesis (somatic embryogenesis) in B. schlosseri. Both alternatives are not necessarily mutually exclusive.
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Affiliation(s)
- Amalia Rosner
- National Institute of Oceanography, Tel Shikmona, Haifa, Israel.
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282
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Tanaka K, Okamoto S, Ishikawa Y, Tamura H, Hara T. DDX1 is required for testicular tumorigenesis, partially through the transcriptional activation of 12p stem cell genes. Oncogene 2009; 28:2142-51. [PMID: 19398953 DOI: 10.1038/onc.2009.89] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cytogenetic analysis has identified 12p gain as the most frequent abnormality in human testicular germ cell tumors (TGCTs). It has been suggested that amplification and overexpression of stem cell-associated genes, including cyclin-D2, on the human chromosome 12p region are involved in germ cell tumorigenesis. By subtractive cDNA analysis, we identified Ddx1, a member of the DEAD-box protein family, as a gene predominantly expressed in the primordial germ cells of mouse embryos. Knockdown of Ddx1 in a mouse spermatogonia-derived cell line, GC-1spg, by short interference RNA repressed the expression of cyclin-D2, CD9 and GDF3 genes. In the mouse cyclin-D2 gene, a genomic DNA region between -348 and -329 was responsible for transcriptional activation by DDX1 based on reporter and gel shift assays. Similarly, DDX1 knockdown in the human TGCT cell line NEC8 repressed the expression of stem cell-associated genes localized on chromosome 12p13.3, including cyclin-D2, CD9 and NANOG. DDX1-knocked-down TGCT cells could not form solid tumors in nude mice. Furthermore, in situ hybridization revealed that DDX1 mRNA was produced in both seminoma and nonseminoma types of human TGCT samples. We conclude that DDX1 is a critical factor for testicular tumorigenesis.
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Affiliation(s)
- K Tanaka
- Stem Cell Project Group, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan.
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283
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Uhlmann-Schiffler H, Kiermayer S, Stahl H. The DEAD box protein Ddx42p modulates the function of ASPP2, a stimulator of apoptosis. Oncogene 2009; 28:2065-73. [PMID: 19377511 DOI: 10.1038/onc.2009.75] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ddx42p is a recently characterized mammalian DEAD box protein with unknown cellular function. We found that in human cells Ddx42p physically interacts with ASPP2, a major apoptosis inducer known to enhance p53 transactivation of proapoptotic genes. The proteins interact via a domain within the carboxy-terminal part of Ddx42p and a mid-amino-terminal sequence as well as the ankyrin-SH3 region of ASPP2. Overexpression of Ddx42p interferes with apoptosis induction by ASPP2, whereas Ddx42p knockdown reduces the survival rate of cultured human cells. In addition, ASPP2 is found in cytoplasm and nucleus at low Ddx42p level, and predominantly in cytoplasm at high concentration of Ddx42p, respectively. Our results show that Ddx42p is capable of modulating ASPP2 function.
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Affiliation(s)
- H Uhlmann-Schiffler
- Department of Medical Biochemistry and Molecular Biology, The Saarland University, Homburg, Germany.
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284
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Rudolph MG, Wittmann JG, Klostermeier D. Crystallization and preliminary characterization of the Thermus thermophilus RNA helicase Hera C-terminal domain. Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:248-52. [PMID: 19255475 DOI: 10.1107/s1744309108043145] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Accepted: 12/18/2008] [Indexed: 11/10/2022]
Abstract
Heat-resistant RNA-dependent ATPase (Hera) from Thermus thermophilus is a DEAD-box RNA helicase. Two constructs encompassing the second RecA-like domain and the C-terminal domain of Hera were overproduced in Escherichia coli and purified to homogeneity. Single crystals of both Hera constructs were obtained in three crystal forms. A tetragonal crystal form belonged to space group P4(1)2(1)2, with unit-cell parameters a = 65.5, c = 153.0 A, and contained one molecule per asymmetric unit. Two orthorhombic forms belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 62.8, b = 70.9, c = 102.3 A (form I) and a = 41.6, b = 67.6, c = 183.5 A (form II). Both orthorhombic forms contained two molecules per asymmetric unit. All crystals diffracted X-rays to beyond 3 A resolution, but the tetragonal data sets displayed high Wilson B values and high mean |E(2) - 1| values, indicating potential disorder and anisotropy. The tetragonal crystal was phased by MAD using a single selenium site.
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Affiliation(s)
- Markus G Rudolph
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, Georg-August-Universität, Göttingen, Germany
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285
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Abstract
In a recent issue of Cell, Pisareva et al. (2008) reveal that DHX29, a previously uncharacterized mammalian DExH-box protein, facilitates translation initiation on mRNAs with structured 5' untranslated regions.
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286
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Abstract
DEAD-box proteins, which comprise the largest helicase family, are involved in virtually all aspects of RNA metabolism. DEAD-box proteins catalyze diverse ATP-driven functions including the unwinding of RNA secondary structures. In contrast to many well-studied DNA and viral RNA helicases, DEAD-box proteins do not rely on translocation on one of the nucleic acid strands for duplex unwinding, but directly load onto helical regions and then locally pry the strands apart in an ATP-dependent fashion. In this chapter, we outline substrate design and unwinding protocols for DEAD-box proteins and focus on the quantitative evaluation of their unwinding activity.
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Affiliation(s)
- Eckhard Jankowsky
- Department of Biochemistry & Center for RNA Molecular Biology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
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287
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ATP hydrolysis is required for DEAD-box protein recycling but not for duplex unwinding. Proc Natl Acad Sci U S A 2008; 105:20209-14. [PMID: 19088201 DOI: 10.1073/pnas.0811115106] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
DEAD-box proteins, the largest helicase family, catalyze ATP-dependent remodeling of RNA-protein complexes and the unwinding of RNA duplexes. Because DEAD-box proteins hydrolyze ATP in an RNA-dependent fashion, the energy provided by ATP hydrolysis is commonly assumed to drive the energetically unfavorable duplex unwinding. Here, we show efficient unwinding of stable duplexes by several DEAD-box proteins in the presence of the nonhydrolyzable ATP analog ADP-beryllium fluoride. Another ATP analog, ADP-aluminum fluoride, does not promote unwinding. The findings show that the energy from ATP hydrolysis is dispensable for strand separation. ATP binding, however, appears necessary. ATP hydrolysis is found to be required for fast enzyme release from the RNA and multiple substrate turnovers and thus for enzyme recycling.
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288
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Rajyaguru P, Parker R. CGH-1 and the control of maternal mRNAs. Trends Cell Biol 2008; 19:24-8. [PMID: 19062290 DOI: 10.1016/j.tcb.2008.11.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Revised: 10/30/2008] [Accepted: 11/03/2008] [Indexed: 01/07/2023]
Abstract
Development requires the translation of stored maternal messenger RNAs (mRNAs) in a spatial and temporally specified manner. Maternal mRNAs are often in large RNA-protein (RNP) granules. Recent papers reveal that maternal mRNA granules in Caenorhabditis elegans oocytes and early development are dynamic and related to P-bodies and stress granules, which are conserved RNP granules seen in somatic cells. In addition, a highly conserved putative RNA helicase, termed CGH-1 in C. elegans, is now shown to be important for both for translation repression and the stability of stored mRNAs. The analysis of CGH-1 ortholog functions in somatic cells and its interacting proteins indicate possible mechanisms by which this protein family might stabilize stored maternal mRNAs.
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Affiliation(s)
- Purusharth Rajyaguru
- Department of Molecular and Cellular Biology and Howard Hughes Medical Institute, University of Arizona, Tucson, AZ 85721-0106, USA
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289
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Evolution of MDA-5/RIG-I-dependent innate immunity: independent evolution by domain grafting. Proc Natl Acad Sci U S A 2008; 105:17040-5. [PMID: 18971330 DOI: 10.1073/pnas.0804956105] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Type I Interferons (IFNs) are requisite components in antiviral innate immunity. Classically, a Toll-like receptor-dependent pathway induces type I interferons. However, recent recognition of melanoma differentiation associated gene-5 (MDA-5) and retinoic acid inducible gene-I (RIG-I) as primary sensors of RNA viruses for type I interferon induction highlights a potentially unique pathway for innate immunity. Our present investigation tracing the phylogenetic origin of MDA-5 and RIG-I domain arrangement (CARD1-CARD2-helicase-DEAD/DEAH) indicates that these proteins originated specifically in mammals, firmly linking this family of proteins with interferons in a highly derived evolutionary development of innate immunity. MDA-5, but not RIG-I, orthologs are found in fish, indicating that MDA-5 might have evolved before RIG-I. Our analyses also reveal that the MDA-5 and RIG-I domain arrangement evolved independently by domain grafting and not by a simple gene-duplication event of the entire four-domain arrangement, which may have been initiated by differential sensitivity of these proteins to viral infection.
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290
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Chalupníková K, Lattmann S, Selak N, Iwamoto F, Fujiki Y, Nagamine Y. Recruitment of the RNA helicase RHAU to stress granules via a unique RNA-binding domain. J Biol Chem 2008; 283:35186-98. [PMID: 18854321 DOI: 10.1074/jbc.m804857200] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In response to environmental stress, the translation machinery of cells is reprogrammed. The majority of actively translated mRNAs are released from polysomes and driven to specific cytoplasmic foci called stress granules (SGs) where dynamic changes in protein-RNA interaction determine the subsequent fate of mRNAs. Here we show that the DEAH box RNA helicase RHAU is a novel SG-associated protein. Although RHAU protein was originally identified as an AU-rich element-associated protein involved in urokinase-type plasminogen activator mRNA decay, it was not clear whether RHAU could directly interact with RNA. We have demonstrated that RHAU physically interacts with RNA in vitro and in vivo through a newly identified N-terminal RNA-binding domain, which was found to be both essential and sufficient for RHAU localization in SGs. We have also shown that the ATPase activity of RHAU plays a role in the RNA interaction and in the regulation of protein retention in SGs. Thus, our results show that RHAU is the fourth RNA helicase detected in SGs, after rck/p54, DDX3, and eIF4A, and that its association with SGs is dynamic and mediated by an RHAU-specific RNA-binding domain.
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Affiliation(s)
- Katerina Chalupníková
- Friedrich Miescher Institute for Biomedical Research, Novartis Research Foundation, Maulbeerstrasse 66, 4058 Basel, Switzerland
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291
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Shen H, Zheng X, Shen J, Zhang L, Zhao R, Green MR. Distinct activities of the DExD/H-box splicing factor hUAP56 facilitate stepwise assembly of the spliceosome. Genes Dev 2008; 22:1796-803. [PMID: 18593880 DOI: 10.1101/gad.1657308] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The essential splicing factor human UAP56 (hUAP56) is a DExD/H-box protein known to promote prespliceosome assembly. Here, using a series of hUAP56 mutants that are defective for ATP-binding, ATP hydrolysis, or dsRNA unwindase/helicase activity, we assess the relative contributions of these biochemical functions to pre-mRNA splicing. We show that prespliceosome assembly requires hUAP56's ATP-binding and ATPase activities, which, unexpectedly, are required for hUAP56 to interact with U2AF(65) and be recruited into splicing complexes. Surprisingly, we find that hUAP56 is also required for mature spliceosome assembly, which requires, in addition to the ATP-binding and ATPase activities, hUAP56's dsRNA unwindase/helicase activity. We demonstrate that hUAP56 directly contacts U4 and U6 snRNAs and can promote unwinding of the U4/U6 duplex, and that both these activities are dependent on U2AF(65). Our results indicate that hUAP56 first interacts with U2AF(65) in an ATP-dependent manner, and subsequently with U4/U6 snRNAs to facilitate stepwise assembly of the spliceosome.
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Affiliation(s)
- Haihong Shen
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
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292
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Bifano AL, Caprara MG. A DExH/D-box protein coordinates the two steps of splicing in a group I intron. J Mol Biol 2008; 383:667-82. [PMID: 18789947 DOI: 10.1016/j.jmb.2008.08.070] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Revised: 08/22/2008] [Accepted: 08/22/2008] [Indexed: 01/26/2023]
Abstract
Proteins of the DExH/D family are ATPases that can unwind duplex RNA in vitro. Individual members of this family coordinate many steps in ribonucleoprotein enzyme assembly and catalysis in vivo, but it is largely unknown how the action of these co-factors is specified and precisely timed. As a first step to address this question biochemically, we describe the development of a new protein-dependent group I intron splicing system that requires such an ATPase for coordinating successive steps in splicing. While genetic analysis in yeast has shown that at least five nuclear-encoded proteins are required for splicing of the mitochondrial aI5beta group I intron, we show that efficient in vitro splicing of aI5beta occurs with only two of these co-factors and, furthermore, they fulfill distinct functions in vitro. The Mrs1p protein stabilizes RNA structure and promotes the first step in splicing. In contrast, a DExH/D protein, Mss116p, acts after the first step and, utilizing ATP hydrolysis, specifically enhances the efficiency of exon ligation. An analysis of Mss116p variants with mutations that impair its RNA-stimulated ATP hydrolysis activity or reduce its ability to unwind duplexes show that the efficiency of ATP hydrolysis is a major determinant in promoting exon ligation. These observations suggest that Mss116p acts in aI5beta splicing by catalyzing changes in the structure of the RNA/protein splicing intermediate that promote the second step. More broadly, these observations are consistent with a model in which the "functional-timing" of DExH/D-box protein action can be specified by a specific conformation of its substrate due to the "upstream" activity of other co-factors.
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Affiliation(s)
- Abby L Bifano
- Center for RNA Molecular Biology, Department of Biochemistry, Case Western Reserve University, School of Medicine, Cleveland, OH 44106-4960, USA
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293
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Konishi T, Uodome N, Sugimoto A. TheCaenorhabditis elegansDDX-23, a homolog of yeast splicing factor PRP28, is required for the sperm-oocyte switch and differentiation of various cell types. Dev Dyn 2008; 237:2367-77. [DOI: 10.1002/dvdy.21649] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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294
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Mercorelli B, Sinigalia E, Loregian A, Palù G. Human cytomegalovirus DNA replication: antiviral targets and drugs. Rev Med Virol 2008; 18:177-210. [PMID: 18027349 DOI: 10.1002/rmv.558] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Human cytomegalovirus (HCMV) infection is associated with severe morbidity and mortality in immunocompromised individuals, in particular transplant recipients and AIDS patients, and is the most frequent congenital viral infection in humans. There are currently five drugs approved for HCMV treatment: ganciclovir and its prodrug valganciclovir, foscarnet, cidofovir and fomivirsen. These drugs have provided a major advance in HCMV disease management, but they suffer from poor bioavailability, significant toxicity and limited effectiveness, mainly due to the development of drug resistance. Fortunately, there are several novel and potentially very effective new compounds which are under pre-clinical and clinical evaluation and may address these limitations. This review focuses on HCMV proteins that are directly or indirectly involved in viral DNA replication and represent already established or potential novel antiviral targets, and describes both currently available drugs and new compounds against such protein targets.
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Affiliation(s)
- Beatrice Mercorelli
- Department of Histology, Microbiology and Medical Biotechnologies, University of Padua, 35121 Padua, Italy
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295
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Abstract
DEAD box proteins are a family of putative RNA helicases associated with all aspects of cellular metabolism involving the modification of RNA secondary structure. DDX1 is a member of the DEAD box protein family that is overexpressed in a subset of retinoblastoma and neuroblastoma cell lines and tumors. DDX1 is found primarily in the nucleus, where it forms two to four large aggregates called DDX1 bodies. Here, we report a rapid redistribution of DDX1 in cells exposed to ionizing radiation, resulting in the formation of numerous foci that colocalize with gamma-H2AX and phosphorylated ATM foci at sites of DNA double-strand breaks (DSBs). The formation of DDX1 ionizing-radiation-induced foci (IRIF) is dependent on ATM, which was shown to phosphorylate DDX1 both in vitro and in vivo. The treatment of cells with RNase H prevented the formation of DDX1 IRIF, suggesting that DDX1 is recruited to sites of DNA damage containing RNA-DNA structures. We have shown that DDX1 has RNase activity toward single-stranded RNA, as well as ADP-dependent RNA-DNA- and RNA-RNA-unwinding activities. We propose that DDX1 plays an RNA clearance role at DSB sites, thereby facilitating the template-guided repair of transcriptionally active regions of the genome.
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296
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Isolation and characterization of Plasmodium falciparum UAP56 homolog: evidence for the coupling of RNA binding and splicing activity by site-directed mutations. Arch Biochem Biophys 2008; 478:143-53. [PMID: 18722339 DOI: 10.1016/j.abb.2008.07.027] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 07/30/2008] [Accepted: 07/31/2008] [Indexed: 01/25/2023]
Abstract
UAP56 (U2AF65 associated protein) is a member of the DEAD-box helicase family. Helicases are essential enzymes generally involved in the metabolism of nucleic acids. The gene encoding a member of DEAD-box family was cloned and characterized from the human malaria parasite Plasmodium falciparum. PfU52 is homologous to UAP56 and contains the RNA-dependent ATPase, RNA helicase and RNA binding activities. Using the parasite extract we report that PfU52 is involved in splicing reaction. Site-directed mutagenesis studies indicate that the conserved residues glycine 181, isoleucine 182 and arginine 206 are involved in RNA binding and this activity is required for the enzymatic activities of PfU52. PfU52 is expressed in all the intraerythrocytic developmental stages of the parasite. In the present study we have reported the detailed characterization of PfU52 from P. falciparum and these results advance the knowledge regarding the function of UAP56 in general.
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297
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Pradhan A, Hussain EM, Tuteja R. Characterization of replication fork and phosphorylation stimulated Plasmodium falciparum helicase 45. Gene 2008; 420:66-75. [DOI: 10.1016/j.gene.2008.05.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Revised: 04/29/2008] [Accepted: 05/01/2008] [Indexed: 12/14/2022]
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298
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Abstract
Helicases and remodeling enzymes are ATP-dependent motor proteins that play a critical role in every aspect of RNA and DNA metabolism. Most RNA-remodeling enzymes are members of helicase superfamily 2 (SF2), which includes many DNA helicase enzymes that display similar structural and mechanistic features. Although SF2 enzymes are typically called helicases, many of them display other types of functions, including single-strand translocation, strand annealing, and protein displacement. There are two mechanisms by which RNA helicase enzymes unwind RNA: The nonprocessive DEAD group catalyzes local unwinding of short duplexes adjacent to their binding sites. Members of the processive DExH group often translocate along single-stranded RNA and displace paired strands (or proteins) in their path. In the latter case, unwinding is likely to occur by an active mechanism that involves Brownian motor function and stepwise translocation along RNA. Through structural and single-molecule investigations, researchers are developing coherent models to explain the functions and dynamic motions of helicase enzymes.
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Affiliation(s)
- Anna Marie Pyle
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute and Yale University, New Haven, Connecticut 06520, USA.
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299
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Abstract
The DEAD-box protein Dbp5 was thought to remodel ribonucleoproteins and displace proteins from these complexes in an ATP-dependent fashion to allow for mRNA export from the nucleus. A recent study on Dbp5 shows, however, that its ADP-bound form may also perform an important function in displacing export factors from mRNA.
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300
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The DEAD-box helicase DDX3X is a critical component of the TANK-binding kinase 1-dependent innate immune response. EMBO J 2008; 27:2135-46. [PMID: 18583960 PMCID: PMC2453059 DOI: 10.1038/emboj.2008.126] [Citation(s) in RCA: 234] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Accepted: 06/04/2008] [Indexed: 12/23/2022] Open
Abstract
TANK-binding kinase 1 (TBK1) is of central importance for the induction of type-I interferon (IFN) in response to pathogens. We identified the DEAD-box helicase DDX3X as an interaction partner of TBK1. TBK1 and DDX3X acted synergistically in their ability to stimulate the IFN promoter, whereas RNAi-mediated reduction of DDX3X expression led to an impairment of IFN production. Chromatin immunoprecipitation indicated that DDX3X is recruited to the IFN promoter upon infection with Listeria monocytogenes, suggesting a transcriptional mechanism of action. DDX3X was found to be a TBK1 substrate in vitro and in vivo. Phosphorylation-deficient mutants of DDX3X failed to synergize with TBK1 in their ability to stimulate the IFN promoter. Overall, our data imply that DDX3X is a critical effector of TBK1 that is necessary for type I IFN induction.
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