801
|
Li L, Roy K, Katyal S, Sun X, Bléoo S, Godbout R. Dynamic nature of cleavage bodies and their spatial relationship to DDX1 bodies, Cajal bodies, and gems. Mol Biol Cell 2005; 17:1126-40. [PMID: 16371507 PMCID: PMC1382303 DOI: 10.1091/mbc.e05-08-0768] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
DDX1 bodies, cleavage bodies, Cajal bodies (CBs), and gems are nuclear suborganelles that contain factors involved in RNA transcription and/or processing. Although all four nuclear bodies can exist as distinct entities, they often colocalize or overlap with each other. To better understand the relationship between these four nuclear bodies, we examined their spatial distribution as a function of the cell cycle. Here, we report that whereas DDX1 bodies, CBs and gems are present throughout interphase, CPSF-100-containing cleavage bodies are predominantly found during S and G2 phases, whereas CstF-64-containing cleavage bodies are primarily observed during S phase. All four nuclear bodies associate with each other during S phase, with cleavage bodies colocalizing with DDX1 bodies, and cleavage bodies/DDX1 bodies residing adjacent to gems and CBs. Although inhibitors of RNA transcription had no effect on DDX1 bodies or cleavage bodies, inhibitors of DNA replication resulted in loss of CstF-64-containing cleavage bodies. A striking effect on nuclear structures was observed with latrunculin B, an inhibitor of actin polymerization, resulting in the formation of needlelike nuclear spicules made up of CstF-64, CPSF-100, RNA, and RNA polymerase II. Our results suggest that cleavage body components are highly dynamic in nature.
Collapse
Affiliation(s)
- Lei Li
- Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada
| | | | | | | | | | | |
Collapse
|
802
|
Elvira G, Wasiak S, Blandford V, Tong XK, Serrano A, Fan X, del Rayo Sánchez-Carbente M, Servant F, Bell AW, Boismenu D, Lacaille JC, McPherson PS, DesGroseillers L, Sossin WS. Characterization of an RNA granule from developing brain. Mol Cell Proteomics 2005; 5:635-51. [PMID: 16352523 DOI: 10.1074/mcp.m500255-mcp200] [Citation(s) in RCA: 224] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In brain, mRNAs are transported from the cell body to the processes, allowing for local protein translation at sites distant from the nucleus. Using subcellular fractionation, we isolated a fraction from rat embryonic day 18 brains enriched for structures that resemble amorphous collections of ribosomes. This fraction was enriched for the mRNA encoding beta-actin, an mRNA that is transported in dendrites and axons of developing neurons. Abundant protein components of this fraction, determined by tandem mass spectrometry, include ribosomal proteins, RNA-binding proteins, microtubule-associated proteins (including the motor protein dynein), and several proteins described only as potential open reading frames. The conjunction of RNA-binding proteins, transported mRNA, ribosomal machinery, and transporting motor proteins defines these structures as RNA granules. Expression of a subset of the identified proteins in cultured hippocampal neurons confirmed that proteins identified in the proteomics were present in neurites associated with ribosomes and mRNAs. Moreover many of the expressed proteins co-localized together. Time lapse video microscopy indicated that complexes containing one of these proteins, the DEAD box 3 helicase, migrated in dendrites of hippocampal neurons at the same speed as that reported for RNA granules. Although the speed of the granules was unchanged by activity or the neurotrophin brain-derived neurotrophic factor, brain-derived neurotrophic factor, but not activity, increased the proportion of moving granules. These studies define the isolation and composition of RNA granules expressed in developing brain.
Collapse
Affiliation(s)
- George Elvira
- Département de Biochimie, Université de Montréal, 2900 Edouard-Montpetit, Montreal, Quebec H3C3J7, Canada
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
803
|
Miki H, Okada Y, Hirokawa N. Analysis of the kinesin superfamily: insights into structure and function. Trends Cell Biol 2005; 15:467-76. [PMID: 16084724 DOI: 10.1016/j.tcb.2005.07.006] [Citation(s) in RCA: 522] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2004] [Revised: 06/13/2005] [Accepted: 07/26/2005] [Indexed: 11/25/2022]
Abstract
Kinesin superfamily proteins (KIFs) are key players or 'hub' proteins in the intracellular transport system, which is essential for cellular function and morphology. The KIF superfamily is also the first large protein family in mammals whose constituents have been completely identified and confirmed both in silico and in vivo. Numerous studies have revealed the structures and functions of individual family members; however, the relationships between members or a perspective of the whole superfamily structure until recently remained elusive. Here, we present a comprehensive summary based on a large, systematic phylogenetic analysis of the kinesin superfamily. All available sequences in public databases, including genomic information from all model organisms, were analyzed to yield the most complete phylogenetic kinesin tree thus far, comprising 14 families. This comprehensive classification builds on the recently proposed standardized nomenclature for kinesins and allows systematic analysis of the structural and functional relationships within the kinesin superfamily.
Collapse
Affiliation(s)
- Harukata Miki
- Department of Cell Biology and Anatomy, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyoku, Tokyo, Japan
| | | | | |
Collapse
|
804
|
Ceccarini M, Torreri P, Lombardi DG, Macchia G, Macioce P, Petrucci TC. Molecular Basis of Dystrobrevin Interaction with Kinesin Heavy Chain: Structural Determinants of their Binding. J Mol Biol 2005; 354:872-82. [PMID: 16288919 DOI: 10.1016/j.jmb.2005.09.069] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Accepted: 09/22/2005] [Indexed: 11/19/2022]
Abstract
Dystrobrevins are a family of widely expressed dystrophin-associated proteins that comprises alpha and beta isoforms and displays significant sequence homology with several protein-binding domains of the dystrophin C-terminal region. The complex distribution of the multiple dystrobrevin isoforms suggests that the variability of their composition may be important in mediating their function. We have recently identified kinesin as a novel dystrobrevin-interacting protein and localized the dystrobrevin-binding site on the cargo-binding domain of neuronal kinesin heavy chain (Kif5A). In the present study, we assessed the kinetics of the dystrobrevin-Kif5A interaction by quantitative pull-down assay and surface plasmon resonance (SPR) analysis and found that beta-dystrobrevin binds to kinesin with high affinity (K(D) approximately 40 nM). Comparison of the sensorgrams obtained with alpha and beta-dystrobrevin at the same concentration of analyte showed a lower affinity of alpha compared to that of beta-dystrobrevin, despite their functional domain homology and about 70% sequence identity. Analysis of the contribution of single dystrobrevin domains to the interaction revealed that the deletion of either the ZZ domain or the coiled-coil region decreased the kinetics of the interaction, suggesting that the tertiary structure of dystrobrevin may play a role in regulating the interaction of dystrobrevin with kinesin. In order to understand if structural changes induced by post-translational modifications could affect dystrobrevin affinity for kinesin, we phosphorylated beta-dystrobrevin in vitro and found that it showed reduced binding capacity towards kinesin. The interaction between the adaptor/scaffolding protein dystrobrevin and the motor protein kinesin may play a role in the transport and targeting of components of the dystrophin-associated protein complex to specific sites in the cell, with the differences in the binding properties of dystrobrevin isoforms reflecting their functional diversity within the same cell type. Phosphorylation events could have a regulatory role in this context.
Collapse
Affiliation(s)
- Marina Ceccarini
- Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
| | | | | | | | | | | |
Collapse
|
805
|
Fujii R, Takumi T. TLS facilitates transport of mRNA encoding an actin-stabilizing protein to dendritic spines. J Cell Sci 2005; 118:5755-65. [PMID: 16317045 DOI: 10.1242/jcs.02692] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
TLS (translocation in liposarcoma), an RNA-binding protein, was originally identified as a heterogeneous ribonuclear protein (hnRNP). Recently, we showed that TLS is localized in neuronal dendrites of mouse hippocampal neurons and is translocated to the spines, where local translation takes place, in an mGluR5 activation-dependent manner. However, the specific role of TLS has not been clarified. TLS-null neurons display abnormal spine morphology, suggesting that TLS-deficiency may impair activity-dependent actin reorganization in spines. To address this issue, we screened for mouse brain transcripts by their in vitro binding to TLS, and identified RNAs that associate with TLS, including mRNAs encoding actin-related proteins such as actin-stabilizing protein Nd1-L. Nd1-L transcripts were increased in the dendrites upon mGluR activation and significantly reduced in TLS-null dendrites. Overexpression of Nd1-L in mouse hippocampal neurons prevented damage to spine structure caused by actin destabilization. Our results demonstrate that TLS associates with mRNA encoding an actin-related protein and may be involved in actin reorganization in spines.
Collapse
Affiliation(s)
- Ritsuko Fujii
- Osaka Bioscience Institute, Suita, Osaka 565-0874, Japan
| | | |
Collapse
|
806
|
Iijima T, Imai T, Kimura Y, Bernstein A, Okano HJ, Yuzaki M, Okano H. Hzf protein regulates dendritic localization and BDNF-induced translation of type 1 inositol 1,4,5-trisphosphate receptor mRNA. Proc Natl Acad Sci U S A 2005; 102:17190-5. [PMID: 16286649 PMCID: PMC1287977 DOI: 10.1073/pnas.0504684102] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Accepted: 10/10/2005] [Indexed: 11/18/2022] Open
Abstract
The localization of certain mRNAs to dendrites and their local translation in synaptic regions are proposed to be involved in certain aspects of synaptic plasticity. A cis-acting element within the 3' untranslated region (3' UTR) of the targeted mRNAs, which is bound by a trans-acting RNA-binding protein, controls the dendritic mRNA localization. Here, we identified hematopoietic zinc finger (Hzf) as a trans-acting factor that regulates the dendritic mRNA localization of the type 1 inositol 1,4,5-trisphosphate receptor (IP(3)RI), a dendritically localized mRNA in cerebellar Purkinje cells, via binding to the 3' UTR. In Hzf-deficient mice, the dendritic localization of IP(3)RI mRNA and brain-derived neurotrophic factor-induced IP(3)RI protein synthesis in the cerebellum were impaired. These findings suggest that Hzf is an RNA-binding protein that controls the dendritic mRNA localization and activity-dependent translation of IP(3)RI, and may be involved in some aspects of synaptic plasticity.
Collapse
Affiliation(s)
- Takatoshi Iijima
- Department of Physiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | | | | | | | | | | | | |
Collapse
|
807
|
Elvira G, Massie B, DesGroseillers L. The zinc-finger protein ZFR is critical for Staufen 2 isoform specific nucleocytoplasmic shuttling in neurons. J Neurochem 2005; 96:105-17. [PMID: 16277607 DOI: 10.1111/j.1471-4159.2005.03523.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In mammalian neurons, transport and translation of mRNA to individual potentiated synapses is believed to occur via a heterogeneous population of RNA granules. To identify components of Staufen2-containing granules, we used the yeast two-hybrid system. A mouse fetal cDNA library was screened with the N-terminal fragment of Staufen2 as bait. ZFR, a three zinc finger protein, was identified as an interacting protein. Confocal microscopy showed that ZFR, although mainly nuclear, was also found in the somatodendritic compartment of primary hippocampal neurons where it localized as granule-like structures. Co-localization with Staufen2 was observed in several granules. Biochemical analyses (immunoprecipitation, cell fractionation) further confirmed the ZFR/Staufen2 association. ZFR was shown to interact with at least the Staufen2(62) isoform, but not with Staufen1. ZFR also co-fractionated with ribosomes and Staufen2(59) and Staufen2(52) in a sucrose gradient. Interestingly, knockdown expression of ZFR through RNA interference in neurons relocated specifically the Staufen2(62), but not the Staufen2(59), isoform to the nucleus. Our results demonstrate that ZFR is a native component of Staufen2-containing granules and likely plays its role during early steps of RNA transport and localization. They also suggest that one of these roles may be linked to Staufen2(62)-containing RNA granule formation in the nucleus and/or to their nucleo-cytoplasmic shuttling.
Collapse
Affiliation(s)
- George Elvira
- Département de Biochimie, Université de Montréal, Montréal, Québec, Canada
| | | | | |
Collapse
|
808
|
Glanzer J, Miyashiro KY, Sul JY, Barrett L, Belt B, Haydon P, Eberwine J. RNA splicing capability of live neuronal dendrites. Proc Natl Acad Sci U S A 2005; 102:16859-64. [PMID: 16275927 PMCID: PMC1277967 DOI: 10.1073/pnas.0503783102] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dendrites are specialized extensions of the neuronal soma that contain components of the cellular machinery involved in RNA and protein metabolism. Several dendritically localized proteins are associated with the precursor-mRNA (pre-mRNA) splicing complex, or spliceosome. Although some spliceosome-related, RNA-binding proteins are known to subserve separate cytoplasmic functions when moving between the nucleus and cytoplasm, little is known about the pre-mRNA splicing capacity of intact dendrites. Here, we demonstrate the presence and functionality of pre-mRNA-splicing components in dendrites. When isolated dendrites are transfected with a chicken delta-crystallin pre-mRNA or luciferase reporter pre-mRNA, splicing junctions clustered at or near expected splice sites are observed. Additionally, in vitro synaptoneurosome experiments show that this subcellular fraction contains a similar complement of splicing factors that is capable of splicing chicken delta-crystallin pre-mRNA. These observations suggest that pre-mRNA-splicing factors found in the dendroplasm retain the potential to promote pre-mRNA splicing.
Collapse
Affiliation(s)
- J Glanzer
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | | | | | | | | | | | | |
Collapse
|
809
|
Chang WC, Keller CG, Sretavan DW. Isolation of neuronal substructures and precise neural microdissection using a nanocutting device. J Neurosci Methods 2005; 152:83-90. [PMID: 16253341 DOI: 10.1016/j.jneumeth.2005.08.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2005] [Accepted: 08/18/2005] [Indexed: 11/25/2022]
Abstract
We describe a set of microfabricated nanocutting devices with a cutting edge of less than 20 nm radius of curvature that enables high precision microdissection and subcellular isolation of neuronal structures. With these devices, it is possible to isolate functional substructures from neurons in culture such as segments of axons and dendrites, dendritic spines and Nodes of Ranvier. By fine-tuning the mechanical compliance of these devices, they can also act as alternatives to costly laser capture microdissection workstations for harvesting specific neuronal populations from tissue sections for analysis. The small size of the device (1 mm2x100 microm) allows convenient insertion into researcher specific experimental set-ups. Its ease of use and possibility for batch fabrication makes this a highly effective and versatile tool for tissue microdissection and the microanalysis of neuronal function.
Collapse
Affiliation(s)
- Wesley C Chang
- Department of Ophthalmology, Program in Neuroscience, Bioengineering Graduate Program, University of California, 10 Koret Way, K110, Box 0730, San Francisco, CA 94143, USA.
| | | | | |
Collapse
|
810
|
Abstract
Fragile X syndrome (FXS) is caused by the transcriptional silencing of the Fmr1 gene, which encodes a protein (FMRP) that can act as a translational suppressor in dendrites, and is characterized by a preponderance of abnormally long, thin and tortuous dendritic spines. According to a current theory of FXS, the loss of FMRP expression leads to an exaggeration of translation responses linked to group I metabotropic glutamate receptors. Such responses are involved in the consolidation of a form of long-term depression that is enhanced in Fmr1 knockout mice and in the elongation of dendritic spines, resembling synaptic phenotypes over-represented in fragile X brain. These observations place fragile X research at the heart of a long-standing issue in neuroscience. The consolidation of memory, and several distinct forms of synaptic plasticity considered to be substrates of memory, requires mRNA translation and is associated with changes in spine morphology. A recent convergence of research on FXS and on the involvement of translation in various forms of synaptic plasticity has been very informative on this issue and on mechanisms underlying FXS. Evidence suggests a general relationship in which the receptors that induce distinct forms of efficacy change differentially regulate translation to produce unique spine shapes involved in their consolidation. We discuss several potential mechanisms for differential translation and the notion that FXS represents an exaggeration of one 'channel' in a set of translation-dependent consolidation responses.
Collapse
Affiliation(s)
- P W Vanderklish
- Department of Neurobiology, The Scripps Research Institute, La Jolla, CA 92037, USA.
| | | |
Collapse
|
811
|
Wu KY, Hengst U, Cox LJ, Macosko EZ, Jeromin A, Urquhart ER, Jaffrey SR. Local translation of RhoA regulates growth cone collapse. Nature 2005; 436:1020-1024. [PMID: 16107849 PMCID: PMC1317112 DOI: 10.1038/nature03885] [Citation(s) in RCA: 322] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Accepted: 06/06/2005] [Indexed: 11/09/2022]
Abstract
Neuronal development requires highly coordinated regulation of the cytoskeleton within the developing axon. This dynamic regulation manifests itself in axonal branching, turning and pathfinding, presynaptic differentiation, and growth cone collapse and extension. Semaphorin 3A (Sema3A), a secreted guidance cue that primarily functions to repel axons from inappropriate targets, induces cytoskeletal rearrangements that result in growth cone collapse. These effects require intra-axonal messenger RNA translation. Here we show that transcripts for RhoA, a small guanosine triphosphatase (GTPase) that regulates the actin cytoskeleton, are localized to developing axons and growth cones, and this localization is mediated by an axonal targeting element located in the RhoA 3' untranslated region (UTR). Sema3A induces intra-axonal translation of RhoA mRNA, and this local translation of RhoA is necessary and sufficient for Sema3A-mediated growth cone collapse. These studies indicate that local RhoA translation regulates the neuronal cytoskeleton and identify a new mechanism for the regulation of RhoA signalling.
Collapse
Affiliation(s)
- Karen Y Wu
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY 10021, USA
| | - Ulrich Hengst
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY 10021, USA
| | - Llewellyn J Cox
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY 10021, USA
| | - Evan Z Macosko
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY 10021, USA
| | - Andreas Jeromin
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Erica R Urquhart
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY 10021, USA
| | - Samie R Jaffrey
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY 10021, USA
| |
Collapse
|
812
|
Tretyakova I, Zolotukhin AS, Tan W, Bear J, Propst F, Ruthel G, Felber BK. Nuclear Export Factor Family Protein Participates in Cytoplasmic mRNA Trafficking. J Biol Chem 2005; 280:31981-90. [PMID: 16014633 DOI: 10.1074/jbc.m502736200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In eukaryotes, the nuclear export of mRNA is mediated by nuclear export factor 1 (NXF1) receptors. Metazoans encode additional NXF1-related proteins of unknown function, which share homology and domain organization with NXF1. Some mammalian NXF1-related genes are expressed preferentially in the brain and are thought to participate in neuronal mRNA metabolism. To address the roles of NXF1-related factors, we studied the two mouse NXF1 homologues, mNXF2 and mNXF7. In neuronal cells, mNXF2, but not mNXF7, exhibited mRNA export activity similar to that of Tip-associated protein/NXF1. Surprisingly, mNXF7 incorporated into mobile particles in the neurites that contained poly(A) and ribosomal RNA and colocalized with Staufen1-containing transport granules, indicating a role in neuronal mRNA trafficking. Yeast two-hybrid interaction, coimmunoprecipitation, and in vitro binding studies showed that NXF proteins bound to brain-specific microtubule-associated proteins (MAP) such as MAP1B and the WD repeat protein Unrip. Both in vitro and in vivo, MAP1B also bound to NXF export cofactor U2AF as well as to Staufen1 and Unrip. These findings revealed a network of interactions likely coupling the export and cytoplasmic trafficking of mRNA. We propose a model in which MAP1B tethers the NXF-associated mRNA to microtubules and facilitates their translocation along dendrites while Unrip provides a scaffold for the assembly of these transport intermediates.
Collapse
Affiliation(s)
- Irina Tretyakova
- Human Retrovirus Pathogenesis Section, Vaccine Branch, Center for Cancer Research, NCI-Frederick, National Institutes of Health, Frederick, Maryland 21702, USA
| | | | | | | | | | | | | |
Collapse
|
813
|
Dugré-Brisson S, Elvira G, Boulay K, Chatel-Chaix L, Mouland AJ, DesGroseillers L. Interaction of Staufen1 with the 5' end of mRNA facilitates translation of these RNAs. Nucleic Acids Res 2005; 33:4797-812. [PMID: 16126845 PMCID: PMC1193567 DOI: 10.1093/nar/gki794] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Staufen1 is a component of transported ribonucleoprotein complexes. Genetic work in Drosophila has suggested that Staufen plays a role in the de-repression of translation of oskar mRNA following localization. To determine whether Staufen1 can play a similar role in mammals, we studied translation of transcripts in the presence or in the absence of Staufen1. Translationally repressed mRNAs were generated by fusing the structured human immunodeficiency virus type 1 trans-activating response (TAR) element to the 5′ end of a reporter transcript. In rabbit reticulocyte lysates and in mammalian cultured cells, the addition of Staufen1 resulted in the up-regulation of reporter activity when translation was driven by the TAR-bearing RNA. In contrast, Staufen1 had no effect on translation of efficiently translated mRNAs lacking an apparent structured 5′ end, suggesting that Staufen1-binding to the 5′ end is required for enhanced translation. Consistently, Staufen1 RNA-binding activity is necessary for this translational effect. In addition, similar up-regulation of translation was observed when Staufen1 was tethered to the 5′ end of mRNAs via other structured RNAs, the highest level of translational increase being obtained with the bona fide Staufen1-binding site of the Arf1 transcript. The expression of Staufen1 promoted polysomal loading of TAR-luciferase transcripts resulting in enhanced translation. Our results support a model in which the expression of Staufen1 and its interaction with the 5′ end of RNA and ribosomes facilitate translation initiation.
Collapse
Affiliation(s)
| | - George Elvira
- Département de Biochimie, Université de MontréalMontréal, QC, Canada
| | - Karine Boulay
- Département de Biochimie, Université de MontréalMontréal, QC, Canada
| | - Laurent Chatel-Chaix
- Département de Biochimie, Université de MontréalMontréal, QC, Canada
- Lady Davis Institute for Medical Research, McGill UniversityMontréal, Canada H3C 3J7
| | - Andrew J. Mouland
- Lady Davis Institute for Medical Research, McGill UniversityMontréal, Canada H3C 3J7
| | - Luc DesGroseillers
- Département de Biochimie, Université de MontréalMontréal, QC, Canada
- Centre de Recherche en Sciences Neurologiques, Université de MontréalMontréal, QC, Canada
- To whom correspondence should be addressed at Department of Biochemistry, University of Montreal, PO Box 6128, Station Centre Ville, Montreal, QC, Canada H3C 3J7. Tel: +1 514 343 5802; Fax: +1 514 343 2210;
| |
Collapse
|
814
|
Abdelhaleem M. RNA helicases: regulators of differentiation. Clin Biochem 2005; 38:499-503. [PMID: 15885226 DOI: 10.1016/j.clinbiochem.2005.01.010] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Revised: 01/04/2005] [Accepted: 01/17/2005] [Indexed: 11/17/2022]
Abstract
RNA helicases are highly conserved enzymes that utilize the energy derived from NTP hydrolysis to modulate the structure of RNA. RNA helicases participate in all biological processes that involve RNA, including transcription, splicing and translation. Based on the sequence of the helicase domain, they are classified into families, such as DDX and DHX families of human RNA helicases. The specificity of RNA helicases to their targets is likely due to several factors, such as the sequence, interacting molecules, subcellular localization and the expression pattern of the helicases. There are several examples of the involvement of RNA helicases in differentiation. Human DDX3 has two closely related genes designated DDX3Y and DDX3X, which are localized to the Y and X chromosomes, respectively. DDX3Y protein is specifically expressed in germ cells and is essential for spermatogenesis. DDX25 is another RNA helicase which has been shown to be required for spermatogenesis. DDX4 shows specific expression in germ cells. The Drosophila ortholog of DDX4, known as vasa, is required for the formation of germ cells and oogenesis by a mechanism that involves regulating the translation of mRNAs essential for differentiation. Abstrakt is the Drosphila ortholog of DDX41, which has been shown to be involved in visual and CNS system development. DDX5 (p68) and its related DDX17 (p72) have also been implicated in organ/tissue differentiation. The ability of RNA helicases to modulate the structure and thus availability of critical RNA molecules for processing leading to protein expression is the likely mechanism by which RNA helicases contribute to differentiation.
Collapse
Affiliation(s)
- Mohamed Abdelhaleem
- Division of Haematopathology, Department of Paediatric Laboratory Medicine, Hospital for Sick Children, University of Toronto, Room 3691 Atrium, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8.
| |
Collapse
|
815
|
Delanoue R, Davis I. Dynein anchors its mRNA cargo after apical transport in the Drosophila blastoderm embryo. Cell 2005; 122:97-106. [PMID: 16009136 DOI: 10.1016/j.cell.2005.04.033] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2004] [Revised: 03/04/2005] [Accepted: 04/28/2005] [Indexed: 11/28/2022]
Abstract
Molecular motors actively transport many types of cargo along the cytoskeleton in a wide range of organisms. One class of cargo is localized mRNAs, which are transported by myosin on actin filaments or by kinesin and dynein on microtubules. How the cargo is kept at its final intracellular destination and whether the motors are recycled after completion of transport are poorly understood. Here, we use a new RNA anchoring assay in living Drosophila blastoderm embryos to show that apical anchoring of mRNA after completion of dynein transport does not depend on actin or on continuous active transport by the motor. Instead, apical anchoring of RNA requires microtubules and involves dynein as a static anchor that remains with the cargo at its final destination. We propose a general principle that could also apply to other dynein cargo and to some other molecular motors, whereby cargo transport and anchoring reside in the same molecule.
Collapse
Affiliation(s)
- Renald Delanoue
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, EH9 3JR, United Kingdom
| | | |
Collapse
|
816
|
Zhang A, Liu X, Cogan JG, Fuerst MD, Polikandriotis JA, Kelm RJ, Strauch AR. YB-1 coordinates vascular smooth muscle alpha-actin gene activation by transforming growth factor beta1 and thrombin during differentiation of human pulmonary myofibroblasts. Mol Biol Cell 2005; 16:4931-40. [PMID: 16093352 PMCID: PMC1243245 DOI: 10.1091/mbc.e05-03-0216] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Profibrotic regulatory mechanisms for tissue repair after traumatic injury have developed under strong evolutionary pressure to rapidly stanch blood loss and close open wounds. We have examined the roles played by two profibrotic mediators, transforming growth factor beta1 (TGFbeta1) and thrombin, in directing expression of the vascular smooth muscle alpha-actin (SMalphaA) gene, an important determinant of myofibroblast differentiation and early protein marker for stromal cell response to tissue injury. TGFbeta1 is a well known transcriptional activator of the SMalphaA gene in myofibroblasts. In contrast, thrombin independently elevates SMalphaA expression in human pulmonary myofibroblasts at the posttranscriptional level. A common feature of SMalphaA up-regulation mediated by thrombin and TGFbeta1 is the involvement of the cold shock domain protein YB-1, a potent repressor of SMalphaA gene transcription in human fibroblasts that also binds mRNA and regulates translational efficiency. YB-1 dissociates from SMalphaA enhancer DNA in the presence of TGFbeta1 or its Smad 2, 3, and 4 coregulatory mediators. Thrombin does not effect SMalphaA gene transcription but rather displaces YB-1 from SMalphaA exon 3 coding sequences previously shown to be required for mRNA translational silencing. The release of YB-1 from promoter DNA coupled with its ability to bind RNA and shuttle between the nucleus and cytoplasm is suggestive of a regulatory loop for coordinating SMalphaA gene output in human pulmonary myofibroblasts at both the transcriptional and translational levels. This loop may help restrict organ-destructive remodeling due to excessive myofibroblast differentiation.
Collapse
Affiliation(s)
- Aiwen Zhang
- Department of Physiology and Cell Biology, The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University College of Medicine and Public Health, Columbus, OH 43210, USA
| | | | | | | | | | | | | |
Collapse
|
817
|
Antar LN, Dictenberg JB, Plociniak M, Afroz R, Bassell GJ. Localization of FMRP-associated mRNA granules and requirement of microtubules for activity-dependent trafficking in hippocampal neurons. GENES BRAIN AND BEHAVIOR 2005; 4:350-9. [PMID: 16098134 DOI: 10.1111/j.1601-183x.2005.00128.x] [Citation(s) in RCA: 172] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Fragile X syndrome is caused by the absence of the fragile X mental-retardation protein (FMRP), an mRNA-binding protein, which may play important roles in the regulation of dendritic mRNA localization and/or synaptic protein synthesis. We have recently applied high-resolution fluorescence imaging methods to document the presence, motility and activity-dependent regulation of FMRP granule trafficking in dendrites and spines of cultured hippocampal neurons. In this study, we show that FMRP granules distribute to F-actin-rich compartments, including filopodia, spines and growth cones during the staged development of hippocampal neurons in culture. Fragile X mental-retardation protein granules were shown to colocalize with ribosomes, ribosomal RNA and MAP1B mRNA, a known FMRP target, which encodes a protein important for microtubule and actin stabilization. The levels of FMRP within dendrites were reduced by disruption of microtubule dynamics, but not by disruption of F-actin. Direct measurements of FMRP transport kinetics using fluorescence recovery after photobleaching in living neurons showed that microtubules were required to induce the mGluR-dependent translocation into dendrites. This study provides further characterization of the composition and regulated trafficking of FMRP granules in dendrites of hippocampal neurons.
Collapse
Affiliation(s)
- L N Antar
- Department of Neuroscience, Rose F. Kennedy Center for Mental Retardation, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | | | | | | | | |
Collapse
|
818
|
Zalfa F, Adinolfi S, Napoli I, Kühn-Hölsken E, Urlaub H, Achsel T, Pastore A, Bagni C. Fragile X mental retardation protein (FMRP) binds specifically to the brain cytoplasmic RNAs BC1/BC200 via a novel RNA-binding motif. J Biol Chem 2005; 280:33403-10. [PMID: 16006558 DOI: 10.1074/jbc.m504286200] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fragile X mental retardation protein (FMRP), the protein responsible for the fragile X syndrome, is an RNA-binding protein involved in localization and translation of neuronal mRNAs. One of the RNAs known to interact with FMRP is the dendritic non-translatable brain cytoplasmic RNA 1 BC1 RNA that works as an adaptor molecule linking FMRP and some of its regulated mRNAs. Here, we showed that the N terminus of FMRP binds strongly and specifically to BC1 and to its potential human analog BC200. This region does not contain a motif known to specifically recognize RNA and thus constitutes a new RNA-binding motif. We further demonstrated that FMRP recognition involves the 5' stem loop of BC1 and that this is the region that exhibits complementarity to FMRP target mRNAs, raising the possibility that FMRP plays a direct role in BC1/mRNA annealing.
Collapse
Affiliation(s)
- Francesca Zalfa
- Dipartimento di Biologia, Università Tor Vergata, 00133 Rome, Italy
| | | | | | | | | | | | | | | |
Collapse
|
819
|
Jia Z, Barbier L, Stuart H, Amraei M, Pelech S, Dennis JW, Metalnikov P, O'Donnell P, Nabi IR. Tumor cell pseudopodial protrusions. Localized signaling domains coordinating cytoskeleton remodeling, cell adhesion, glycolysis, RNA translocation, and protein translation. J Biol Chem 2005; 280:30564-73. [PMID: 15985431 DOI: 10.1074/jbc.m501754200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The pseudopodial protrusions of Moloney sarcoma virus (MSV)-Madin-Darby canine kidney (MDCK)-invasive (INV) variant cells were purified on 1-microm pore polycarbonate filters that selectively allow passage of the pseudopodial domains but not the cell body. The purified pseudopodial fraction contains phosphotyrosinated proteins, including Met and FAK, and various signaling proteins, including Raf1, MEK1, ERK2, PKBalpha (Akt1), GSK3alpha, GSK3beta, Rb, and Stat3. Pseudopodial proteins identified by liquid chromatography tandem mass spectrometry included actin and actin-regulatory proteins (ERM, calpain, filamin, myosin, Sra-1, and IQGAP1), tubulin, vimentin, adhesion proteins (vinculin, talin, and beta1 integrin), glycolytic enzymes, proteins associated with protein translation, RNA translocation, and ubiquitin-mediated protein degradation, as well as protein chaperones (HSP90 and HSC70) and signaling proteins (RhoGDI and ROCK). Inhibitors of MEK1 (U0126) and HSP90 (geldanamycin) significantly reduced MSV-MDCK-INV cell motility and pseudopod expression, and geldanamycin treatment inhibited Met phosphorylation and induced the expression of actin stress fibers. ROCK inhibition did not inhibit cell motility but transformed the pseudopodial protrusions of MSV-MDCK-INV cells into extended lamellipodia. Dominant negative Rho disrupted pseudopod expression and, in serum-starved cells, L-alpha-lysophosphatidic acid (oleoyl) activation of Rho induced pseudopodial protrusions or, in the presence of the ROCK inhibitor, extended lamellipodia. RNA was localized to the actin-rich pseudopodial domains of MSV-MDCK-INV cells, but the extent of colocalization with dense actin ruffles was reduced in the extended lamellipodia formed upon ROCK inhibition. Rho/ROCK activation in epithelial tumor cells therefore regulates RNA translocation to a pseudopodial domain that contains proteins involved in signaling, cytoskeleton remodeling, cell adhesion, glycolysis, and protein translation and degradation.
Collapse
Affiliation(s)
- Zongjian Jia
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z3
| | | | | | | | | | | | | | | | | |
Collapse
|
820
|
Etter PD, Narayanan R, Navratilova Z, Patel C, Bohmann D, Jasper H, Ramaswami M. Synaptic and genomic responses to JNK and AP-1 signaling in Drosophila neurons. BMC Neurosci 2005; 6:39. [PMID: 15932641 PMCID: PMC1175850 DOI: 10.1186/1471-2202-6-39] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2005] [Accepted: 06/02/2005] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND The transcription factor AP-1 positively controls synaptic plasticity at the Drosophila neuromuscular junction. Although in motor neurons, JNK has been shown to activate AP-1, a positive regulator of growth and strength at the larval NMJ, the consequences of JNK activation are poorly studied. In addition, the downstream transcriptional targets of JNK and AP-1 signaling in the Drosophila nervous system have yet to be identified. Here, we further investigated the role of JNK signaling at this model synapse employing an activated form of JNK-kinase; and using Serial Analysis of Gene Expression and oligonucleotide microarrays, searched for candidate early targets of JNK or AP-1 dependent transcription in neurons. RESULTS Temporally-controlled JNK induction in postembryonic motor neurons triggers synaptic growth at the NMJ indicating a role in developmental plasticity rather than synaptogenesis. An unexpected observation that JNK activation also causes a reduction in transmitter release is inconsistent with JNK functioning solely through AP-1 and suggests an additional, yet-unidentified pathway for JNK signaling in motor neurons. SAGE profiling of mRNA expression helps define the neural transcriptome in Drosophila. Though many putative AP-1 and JNK target genes arose from the genomic screens, few were confirmed in subsequent validation experiments. One potentially important neuronal AP-1 target discovered, CG6044, was previously implicated in olfactory associative memory. In addition, 5 mRNAs regulated by RU486, a steroid used to trigger conditional gene expression were identified. CONCLUSION This study demonstrates a novel role for JNK signaling at the larval neuromuscular junction and provides a quantitative profile of gene transcription in Drosophila neurons. While identifying potential JNK/AP-1 targets it reveals the limitations of genome-wide analyses using complex tissues like the whole brain.
Collapse
Affiliation(s)
- Paul D Etter
- Department of Molecular & Cellular Biology, University of Arizona, Tucson, USA
| | | | - Zaneta Navratilova
- Department of Molecular & Cellular Biology, University of Arizona, Tucson, USA
| | - Chirag Patel
- Department of Molecular & Cellular Biology, University of Arizona, Tucson, USA
| | - Dirk Bohmann
- Department of Biomedical Genetics, University of Rochester, Rochester, USA
| | - Heinrich Jasper
- Department of Brain and Cognitive Sciences, MIT, Cambridge, USA
| | - Mani Ramaswami
- Department of Molecular & Cellular Biology, University of Arizona, Tucson, USA
- ARL Division of Neurobiology, University of Arizona, Tucson, USA
| |
Collapse
|
821
|
Fang J, Acheampong E, Dave R, Wang F, Mukhtar M, Pomerantz RJ. The RNA helicase DDX1 is involved in restricted HIV-1 Rev function in human astrocytes. Virology 2005; 336:299-307. [PMID: 15892970 DOI: 10.1016/j.virol.2005.03.017] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2005] [Revised: 03/03/2005] [Accepted: 03/12/2005] [Indexed: 11/16/2022]
Abstract
Productive infection by human immunodeficiency virus type I (HIV-1) in the central nervous system (CNS) involves mainly macrophages and microglial cells. A frequency of less than 10% of human astrocytes is estimated to be infectable with HIV-1. Nonetheless, this relatively low percentage of infected astrocytes, but associated with a large total number of astrocytic cells in the CNS, makes human astrocytes a critical part in the analyses of potential HIV-1 reservoirs in vivo. Investigations in astrocytic cell lines and primary human fetal astrocytes revealed that limited HIV-1 replication in these cells resulted from low-level viral entry, transcription, viral protein processing, and virion maturation. Of note, a low ratio of unspliced versus spliced HIV-1-specific RNA was also investigated, as Rev appeared to act aberrantly in astrocytes, via loss of nuclear and/or nucleolar localization and diminished Rev-mediated function. Host cellular machinery enabling Rev function has become critical for elucidation of diminished Rev activity, especially for those factors leading to RNA metabolism. We have recently identified a DEAD-box protein, DDX1, as a Rev cellular co-factor and now have explored its potential importance in astrocytes. Cells were infected with HIV-1 pseudotyped with envelope glycoproteins of amphotropic murine leukemia viruses (MLV). Semi-quantitative reverse transcriptase-polymerase chain reactions (RT-PCR) for unspliced, singly-spliced, and multiply-spliced RNA clearly showed a lower ratio of unspliced/singly-spliced over multiply-spliced HIV-1-specific RNA in human astrocytes as compared to Rev-permissive, non-glial control cells. As well, the cellular localization of Rev in astrocytes was cytoplasmically dominant as compared to that of Rev-permissive, non-glial controls. This endogenous level of DDX1 expression in astrocytes was demonstrated directly to lead to a shift of Rev sub-cellular distribution dominance from nuclear and/or nucleolar to cytoplasmic, as input of exogenous DDX1 significantly altered both Rev sub-cellular localization from cytoplasmic to nuclear predominance and concomitantly increased HIV-1 viral production in these human astrocytes. We conclude that altered DDX1 expression in human astrocytes is, at least in part, responsible for the unfavorable cellular microenvironment for Rev function in these CNS-based cells. Thus, these data suggest a molecular mechanism(s) for restricted replication in astrocytes as a potential low-level site of residual HIV-1 in vivo.
Collapse
Affiliation(s)
- Jianhua Fang
- The Dorrance H. Hamilton Laboratories, Center for Human Virology and Biodefense, Division of Infectious Diseases and Environmental Medicine, Department of Medicine, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | | | | | | | | | | |
Collapse
|
822
|
Bagni C, Greenough WT. From mRNP trafficking to spine dysmorphogenesis: the roots of fragile X syndrome. Nat Rev Neurosci 2005; 6:376-87. [PMID: 15861180 DOI: 10.1038/nrn1667] [Citation(s) in RCA: 368] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The mental retardation protein FMRP is involved in the transport of mRNAs and their translation at synapses. Patients with fragile X syndrome, in whom FMRP is absent or mutated, show deficits in learning and memory that might reflect impairments in the translational regulation of a subset of neuronal mRNAs. The study of FMRP provides important insights into the regulation and functions of local protein synthesis in the neuronal periphery, and increases our understanding of how these functions can produce specific effects at individual synapses.
Collapse
Affiliation(s)
- Claudia Bagni
- Dipartimento di Biologia, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma, Italy.
| | | |
Collapse
|
823
|
Abstract
mRNA localization is a common mechanism for targeting proteins to regions of the cell where they are required. It has an essential role in localizing cytoplasmic determinants, controlling the direction of protein secretion and allowing the local control of protein synthesis in neurons. New methods for in vivo labelling have revealed that several mRNAs are transported by motor proteins, but how most mRNAs are coupled to these proteins remains obscure.
Collapse
Affiliation(s)
- Daniel St Johnston
- The Gurdon Institute and The Department of Genetics, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK.
| |
Collapse
|
824
|
Kim HK, Kim YB, Kim EG, Schuman E. Measurement of dendritic mRNA transport using ribosomal markers. Biochem Biophys Res Commun 2005; 328:895-900. [PMID: 15707962 DOI: 10.1016/j.bbrc.2005.01.041] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2004] [Indexed: 11/29/2022]
Abstract
mRNA is transported to the dendritic regions by forming RNA granules, an aggregate of mRNA, ribosomal proteins, rRNA, and RNA-binding proteins such as Staufen. In this study, the dendritic transport of RNA granules was measured using the individual antibodies to ribosome-specific markers such as ribosomal L4 or S6 protein, and Y10B, a monoclonal antibody specific to rRNA. All the markers showed significant immunoreactivity in the dendritic regions of the hippocampal neurons. In addition, a GFP-tagged Staufen, a marker protein of the RNA granules, was colocalized with the Y10B and S6 signals in the dendrites. The S6 signals were also colocalized with the Y10B signals in the dendrites. Consistent with previous studies, the depolarization induced by KCl stimulation increased the ribosomal level, revealed by the S6 or Y10B immunostaining in the distal dendrites. These results demonstrate the utility of ribosomal markers for detecting the RNA granules or mRNA transport in dendrites.
Collapse
Affiliation(s)
- Hyong Kyu Kim
- Department of Medicine and Microbiology, College of Medicine and Medical Research Institute, Chungbuk National University, Cheongju 361-768, Republic of Korea.
| | | | | | | |
Collapse
|
825
|
Kim YK, Furic L, Desgroseillers L, Maquat LE. Mammalian Staufen1 recruits Upf1 to specific mRNA 3'UTRs so as to elicit mRNA decay. Cell 2005; 120:195-208. [PMID: 15680326 DOI: 10.1016/j.cell.2004.11.050] [Citation(s) in RCA: 399] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2004] [Revised: 11/11/2004] [Accepted: 11/24/2004] [Indexed: 10/25/2022]
Abstract
Mammalian Staufen (Stau)1 is an RNA binding protein that is thought to function in mRNA transport and translational control. Nonsense-mediated mRNA decay (NMD) degrades abnormal and natural mRNAs that terminate translation sufficiently upstream of a splicing-generated exon-exon junction. Here we describe an mRNA decay mechanism that involves Stau1, the NMD factor Upf1, and a termination codon. Unlike NMD, this mechanism does not involve pre-mRNA splicing and occurs when Upf2 or Upf3X is downregulated. Stau1 binds directly to Upf1 and elicits mRNA decay when tethered downstream of a termination codon. Stau1 also interacts with the 3'-untranslated region of ADP-ribosylation factor (Arf)1 mRNA. Accordingly, downregulating either Stau1 or Upf1 increases Arf1 mRNA stability. These findings suggest that Arf1 mRNA is a natural target for Stau1-mediated decay, and data indicate that other mRNAs are also natural targets. We discuss this pathway as a means for cells to downregulate the expression of Stau1 binding transcripts.
Collapse
Affiliation(s)
- Yoon Ki Kim
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, 601 Elmwood Avenue, Box 712, University of Rochester, Rochester, NY 14642, USA
| | | | | | | |
Collapse
|
826
|
Fujii R, Okabe S, Urushido T, Inoue K, Yoshimura A, Tachibana T, Nishikawa T, Hicks GG, Takumi T. The RNA Binding Protein TLS Is Translocated to Dendritic Spines by mGluR5 Activation and Regulates Spine Morphology. Curr Biol 2005; 15:587-93. [PMID: 15797031 DOI: 10.1016/j.cub.2005.01.058] [Citation(s) in RCA: 253] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 01/05/2005] [Accepted: 01/05/2005] [Indexed: 11/17/2022]
Abstract
Neuronal dendrites, together with dendritic spines, exhibit enormously diverse structure. Selective targeting and local translation of mRNAs in dendritic spines have been implicated in synapse remodeling or synaptic plasticity. The mechanism of mRNA transport to the postsynaptic site is a fundamental question in local dendritic translation. TLS (translocated in liposarcoma), previously identified as a component of hnRNP complexes, unexpectedly showed somatodendritic localization in mature hippocampal pyramidal neurons. In the present study, TLS was translocated to dendrites and was recruited to dendrites not only via microtubules but also via actin filaments. In mature hippocampal pyramidal neurons, TLS accumulated in the spines at excitatory postsynapses upon mGluR5 activation, which was accompanied by an increased RNA content in dendrites. Consistent with the in vitro studies, TLS-null hippocampal pyramidal neurons exhibited abnormal spine morphology and lower spine density. Our results indicate that TLS participates in mRNA sorting to the dendritic spines induced by mGluR5 activation and regulates spine morphology to stabilize the synaptic structure.
Collapse
Affiliation(s)
- Ritsuko Fujii
- Osaka Bioscience Institute, Suita, Osaka 565-0874, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
827
|
Hirokawa N, Takemura R. Molecular motors and mechanisms of directional transport in neurons. Nat Rev Neurosci 2005; 6:201-14. [PMID: 15711600 DOI: 10.1038/nrn1624] [Citation(s) in RCA: 612] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Intracellular transport is fundamental for neuronal morphogenesis, function and survival. Many proteins are selectively transported to either axons or dendrites. In addition, some specific mRNAs are transported to dendrites for local translation. Proteins of the kinesin superfamily participate in selective transport by using adaptor or scaffolding proteins to recognize and bind cargoes. The molecular components of RNA-transporting granules have been identified, and it is becoming clear how cargoes are directed to axons and dendrites by kinesin superfamily proteins. Here we discuss the molecular mechanisms of directional axonal and dendritic transport with specific emphasis on the role of motor proteins and their mechanisms of cargo recognition.
Collapse
Affiliation(s)
- Nobutaka Hirokawa
- Department of Cell Biology and Anatomy, Graduate School of Medicine, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
| | | |
Collapse
|
828
|
Aschrafi A, Cunningham BA, Edelman GM, Vanderklish PW. The fragile X mental retardation protein and group I metabotropic glutamate receptors regulate levels of mRNA granules in brain. Proc Natl Acad Sci U S A 2005; 102:2180-5. [PMID: 15684045 PMCID: PMC548595 DOI: 10.1073/pnas.0409803102] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Fragile X syndrome results from the transcriptional silencing of a gene, Fmr1, that codes for an mRNA-binding protein (fragile X mental retardation protein, FMRP) present in neuronal dendrites. FMRP can act as a translational suppressor, and its own translation in dendrites is regulated by group I metabotropic glutamate receptors (mGluRs). Multiple lines of evidence suggest that mGluR-induced translation is exaggerated in Fragile X syndrome because of a lack of translational inhibition normally provided by FMRP. We characterized the role of FMRP in the regulation of mRNA granules, which sediment as a heavy peak after polysomes on sucrose gradients. In WT mouse brain, FMRP distributed with polysomes and granules. EM and biochemical analyses suggested that the granule fraction itself contained clusters of polysomes. In Fmr1 knockout brain, we observed a significant decrease in the amount of mRNA granules relative to WT mice. This difference appeared to be due to a role of FMRP in regulating the activation of granules during mGluR-induced translation; in vivo administration of the mGluR5 antagonist 2-methyl-6-(phenylethynyl)pyridine increased granule content in Fmr1 knockout mouse brain to levels comparable with those seen in WT brain. In accord with a role of mGluR5 in the regulation of ongoing translation in vivo, we observed that the phosphorylation of several initiation factors in response to application of the mGluR1/5 agonist S-3,5-dihydroxyphenylglycine in vitro was blocked by methyl-6-(phenylethynyl)pyridine. Together, these data suggest that although large, polysome-containing granules can form in the absence of FMRP, their use in response to mGluR-induced translation is exaggerated.
Collapse
Affiliation(s)
- Armaz Aschrafi
- Department of Neurobiology, The Scripps Research Institute, and The Skaggs Institute for Chemical Biology, 10550 North Torrey Pines Road, SBR-14, La Jolla, CA 92037, USA
| | | | | | | |
Collapse
|
829
|
Belly A, Moreau-Gachelin F, Sadoul R, Goldberg Y. Delocalization of the multifunctional RNA splicing factor TLS/FUS in hippocampal neurones: exclusion from the nucleus and accumulation in dendritic granules and spine heads. Neurosci Lett 2005; 379:152-7. [PMID: 15843054 DOI: 10.1016/j.neulet.2004.12.071] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2004] [Revised: 12/08/2004] [Accepted: 12/22/2004] [Indexed: 11/28/2022]
Abstract
Long-term synaptic change in the cortex and the hippocampus is believed to require the highly localized delivery and translation of mRNAs in the dendritic shafts and spines. The molecular interactions that underlie local signalling between synapses and mRNAs are still largely undefined. After purification from total brain extracts, the NMDA receptor is known to be associated with numerous proteins, including the multifunctional RNA-binding factor TLS (also called FUS). In non-neural tissue, TLS is a vital nuclear protein with roles in DNA repair, homologous recombination, transcriptional regulation and pre-mRNA processing. We have examined the distribution of TLS in hippocampal neurones, both in the adult brain and in mature primary cultures, using subcellular fractionation and immunofluorescence techniques. TLS immunoreactivity is largely excluded from the neuronal nucleus and is found in the cytosol and in somatodendritic particles. In some of these particles, TLS colocalizes with Sam68, a nuclear RNA-binding protein that we previously showed is incorporated into dendritic RNA granules. Some of the TLS clusters also colocalize with NMDA receptor clusters. Finally, TLS clusters are occasionally seen within spine heads. The apparent removal of TLS from the nucleus might result in specific patterns of mRNA transcription or splicing in hippocampal neurones. TLS may also contribute to steering, anchoring or regulating mRNAs at synaptic sites.
Collapse
Affiliation(s)
- Agnès Belly
- Laboratoire Neurodégénérescence et Plasticité, Université Joseph Fourier and INSERM EMI 0108, Pavillon de Neurologie, Centre Hospitalier Universitaire, F-38043 Grenoble cedex 9, France
| | | | | | | |
Collapse
|
830
|
Klann E, Dever TE. Biochemical mechanisms for translational regulation in synaptic plasticity. Nat Rev Neurosci 2005; 5:931-42. [PMID: 15550948 DOI: 10.1038/nrn1557] [Citation(s) in RCA: 315] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Changes in gene expression are required for long-lasting synaptic plasticity and long-term memory in both invertebrates and vertebrates. Regulation of local protein synthesis allows synapses to control synaptic strength independently of messenger RNA synthesis in the cell body. Recent reports indicate that several biochemical signalling cascades couple neurotransmitter and neurotrophin receptors to translational regulatory factors in protein synthesis-dependent forms of synaptic plasticity and memory. In this review, we highlight these translational regulatory mechanisms and the signalling pathways that govern the expression of synaptic plasticity in response to specific types of neuronal stimulation.
Collapse
Affiliation(s)
- Eric Klann
- Departments of Molecular Physiology and Biophysics and Neuroscience, Baylor College of Medicine, One Baylor Plaza BCM 335, Houston, TX 77030, USA.
| | | |
Collapse
|
831
|
Colby GP, Sung YJ, Ambron RT. mRNAs encoding theAplysia homologues of fasciclin-I and β-thymosin are expressed only in the second phase of nerve injury and are differentially segregated in axons regenerating in vitro and in vivo. J Neurosci Res 2005; 82:484-98. [PMID: 16237720 DOI: 10.1002/jnr.20645] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Studies using Aplysia californica have demonstrated that transcription after nerve injury occurs during a rapid, transient first phase and a delayed, prolonged second phase. Although the second phase is especially important for regeneration, the mRNAs produced during this phase have not been identified. We characterized two such mRNAs following axotomy. One encodes a novel fasciclin-I homologue, Aplysia fasciclin-like protein (apFasP), and the other encodes Aplysia beta-thymosin (apbetaT). In addition to mRNA synthesis, proteins required for regeneration must be available at the site of growth, and the transport and local translation of certain extrasomatic mRNAs aids in this process. We found apbetaT and apFasP proteins and mRNA at growth cones in vitro. However, only the mRNA for apbetaT was present in regenerating axons in vivo. This implies that the membrane protein apFasP is supplied by rapid transport from the soma, whereas the soluble apbetaT is synthesized locally.
Collapse
MESH Headings
- Animals
- Aplysia
- Axons/metabolism
- Blotting, Northern/methods
- Blotting, Western/methods
- Cell Adhesion Molecules, Neuronal/genetics
- Cell Adhesion Molecules, Neuronal/metabolism
- Cell Count/methods
- Cloning, Molecular
- Functional Laterality
- Ganglia, Invertebrate/pathology
- Gene Expression/physiology
- Gene Expression Regulation/physiology
- Immunohistochemistry/methods
- In Situ Hybridization/methods
- In Vitro Techniques
- Models, Neurological
- Nerve Crush/methods
- Nerve Regeneration/physiology
- Neurons/metabolism
- Neurons/pathology
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Sequence Analysis, Protein
- Sequence Homology
- Thymosin/genetics
- Thymosin/metabolism
- Time Factors
- Trauma, Nervous System/metabolism
Collapse
Affiliation(s)
- Geoffrey P Colby
- Department of Anatomy and Cell Biology, Columbia University, New York, NY 10032, USA
| | | | | |
Collapse
|
832
|
Hirokawa N, Takemura R. Kinesin superfamily proteins and their various functions and dynamics. Exp Cell Res 2004; 301:50-9. [PMID: 15501445 DOI: 10.1016/j.yexcr.2004.08.010] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2004] [Indexed: 11/19/2022]
Abstract
Kinesin superfamily proteins (KIFs) are motor proteins that transport membranous organelles and macromolecules fundamental for cellular functions along microtubules. Their roles in transport in axons and dendrites have been studied extensively, but KIFs are also used in intracellular transport in general. Recent findings have revealed that in many cases, the specific interaction of cargoes and motors is mediated via adaptor/scaffolding proteins. Cargoes are sorted to precise destinations, such as axons or dendrites. KIFs also participate in polarized transport in epithelial cells as shown in the apical transport of annexin XIIIb-containing vesicles by KIFC3. KIFs play important roles in higher order neuronal activity; transgenic mice overexpressing KIF17, which transports N-methyl-d-asp (NMDA) receptors to dendrites, show enhanced memory and learning. KIFs also play significant roles in neuronal development and brain wiring: KIF2A suppresses elongation of axon collaterals by its unique microtubule-depolymerizing activity. X-ray crystallography has revealed the structural uniqueness of KIF2 underlying the microtubule-depolymerizing activity. In addition, single molecule biophysics and optical trapping have shown that the motility of monomeric KIF1A is caused by biased Brownian movement, and X-ray crystallography has shown how the conformational changes occur for KIF1A to move during ATP hydrolysis. These multiple approaches in analyzing KIF functions will illuminate many basic mechanisms underlying intracellular events and will be a very promising and fruitful area for future studies.
Collapse
Affiliation(s)
- Nobutaka Hirokawa
- Department of Cell Biology and Anatomy, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
| | | |
Collapse
|
833
|
Ling SC, Fahrner PS, Greenough WT, Gelfand VI. Transport of Drosophila fragile X mental retardation protein-containing ribonucleoprotein granules by kinesin-1 and cytoplasmic dynein. Proc Natl Acad Sci U S A 2004; 101:17428-33. [PMID: 15583137 PMCID: PMC536039 DOI: 10.1073/pnas.0408114101] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Transport and translation of mRNA are tightly coupled to ensure strict temporal and spatial expression of nascent proteins. Fragile X mental retardation protein (FMRP) has been shown to be involved in translational regulation and is found in ribonucleoprotein (RNP) granules that travel along dendrites of neurons. In this study, GFP-tagged Drosophila homologue of FMRP (dFMR) was used to visualize RNP granule movement in Drosophila S2 cells. GFP-dFMR form granules that contain both endogenous dFMR and mRNA. Live fluorescence microscopy revealed that dFMR-containing RNP granules move bidirectionally in thin processes formed by S2 cells in the presence of cytochalasin D. Knocking down the heavy chains of either kinesin-1 (kinesin heavy chain) or cytoplasmic dynein (dynein heavy chain) by RNA interference blocks the movement of the dFMR granules. In contrast, knockdown of kinesin light chain (KLC), which is typically necessary for movement of membrane organelles by kinesin-1, had no effect on the dFMR granule translocation. In immunoprecipitation assays, dFMR associates with both kinesin heavy chain and dynein heavy chain, but not KLC. Based on these findings, we conclude that dFMR-containing RNP granules are moved by both kinesin-1 and cytoplasmic dynein and that KLC is not essential and is likely missing from RNP-transporting kinesin-1.
Collapse
Affiliation(s)
- Shuo-Chien Ling
- Neuroscience Program, Department of Cell Biology, University of Illinois at Urbana-Champaign, 601 South Goodwin Avenue, Urbana, IL 61801, USA
| | | | | | | |
Collapse
|
834
|
Bannai H, Fukatsu K, Mizutani A, Natsume T, Iemura SI, Ikegami T, Inoue T, Mikoshiba K. An RNA-interacting Protein, SYNCRIP (Heterogeneous Nuclear Ribonuclear Protein Q1/NSAP1) Is a Component of mRNA Granule Transported with Inositol 1,4,5-Trisphosphate Receptor Type 1 mRNA in Neuronal Dendrites. J Biol Chem 2004; 279:53427-34. [PMID: 15475564 DOI: 10.1074/jbc.m409732200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
mRNA transport and local translation in the neuronal dendrite is implicated in the induction of synaptic plasticity. Recently, we cloned an RNA-interacting protein, SYNCRIP (heterogeneous nuclear ribonuclear protein Q1/NSAP1), that is suggested to be important for the stabilization of mRNA. We report here that SYNCRIP is a component of mRNA granules in rat hippocampal neurons. SYNCRIP was mainly found at cell bodies, but punctate expression patterns in the proximal dendrite were also seen. Time-lapse analysis in living neurons revealed that the granules labeled with fluorescent protein-tagged SYNCRIP were transported bi-directionally within the dendrite at approximately 0.05 microm/s. Treatment of neurons with nocodazole significantly inhibited the movement of green fluorescent protein-SYNCRIP-positive granules, indicating that the transport of SYNCRIP-containing granules is dependent on microtubules. The distribution of SYNCRIP-containing granules overlapped with that of dendritic RNAs and elongation factor 1alpha. SYNCRIP was also found to be co-transported with green fluorescent protein-tagged human staufen1 and the 3'-untranslated region of inositol 1,4,5-trisphosphate receptor type 1 mRNA. These results suggest that SYNCRIP is transported within the dendrite as a component of mRNA granules and raise the possibility that mRNA turnover in mRNA granules and the regulation of local protein synthesis in neuronal dendrites may involve SYNCRIP.
Collapse
Affiliation(s)
- Hiroko Bannai
- Laboratory for Developmental Neurobiology, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | | | | | | | | | | | | | | |
Collapse
|
835
|
Thomas MG, Martinez Tosar LJ, Loschi M, Pasquini JM, Correale J, Kindler S, Boccaccio GL. Staufen recruitment into stress granules does not affect early mRNA transport in oligodendrocytes. Mol Biol Cell 2004; 16:405-20. [PMID: 15525674 PMCID: PMC539183 DOI: 10.1091/mbc.e04-06-0516] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Staufen is a conserved double-stranded RNA-binding protein required for mRNA localization in Drosophila oocytes and embryos. The mammalian homologues Staufen 1 and Staufen 2 have been implicated in dendritic RNA targeting in neurons. Here we show that in rodent oligodendrocytes, these two proteins are present in two independent sets of RNA granules located at the distal myelinating processes. A third kind of RNA granules lacks Staufen and contains major myelin mRNAs. Myelin Staufen granules associate with microfilaments and microtubules, and their subcellular distribution is affected by polysome-disrupting drugs. Under oxidative stress, both Staufen 1 and Staufen 2 are recruited into stress granules (SGs), which are stress-induced organelles containing transiently silenced messengers. Staufen SGs contain the poly(A)-binding protein (PABP), the RNA-binding proteins HuR and TIAR, and small but not large ribosomal subunits. Staufen recruitment into perinuclear SGs is paralleled by a similar change in the overall localization of polyadenylated RNA. Under the same conditions, the distribution of recently transcribed and exported mRNAs is not affected. Our results indicate that Staufen 1 and Staufen 2 are novel and ubiquitous SG components and suggest that Staufen RNPs are involved in repositioning of most polysomal mRNAs, but not of recently synthesized transcripts, during the stress response.
Collapse
MESH Headings
- Actin Cytoskeleton/metabolism
- Alternative Splicing
- Animals
- Animals, Newborn
- Biological Transport
- Blotting, Western
- Brain/metabolism
- Cloning, Molecular
- Computer Simulation
- Cytoplasm/metabolism
- In Situ Hybridization, Fluorescence
- Microscopy, Confocal
- Microscopy, Fluorescence
- Microtubules/metabolism
- Models, Genetic
- Myelin Sheath/metabolism
- Oligodendroglia/metabolism
- Oxidative Stress
- Polyribosomes/metabolism
- Protein Structure, Tertiary
- RNA/metabolism
- RNA, Double-Stranded/chemistry
- RNA, Messenger/metabolism
- RNA-Binding Proteins/biosynthesis
- RNA-Binding Proteins/chemistry
- RNA-Binding Proteins/physiology
- Rats
- Rats, Sprague-Dawley
- Ribonucleases/metabolism
- Ribosomes/metabolism
Collapse
Affiliation(s)
- María G Thomas
- Fundación Instituto Leloir, IIB Facultad de Ciencias Exactas y Naturales, University of Buenos Aires, IIBBA-CONICET, Buenos Aires, Argentina
| | | | | | | | | | | | | |
Collapse
|
836
|
Abstract
Fragile X syndrome is caused by the loss of an RNA-binding protein called FMRP (for fragile X mental retardation protein). FMRP seems to influence synaptic plasticity through its role in mRNA transport and translational regulation. Recent advances include the identification of mRNA ligands, FMRP-mediated mRNA transport and the neuronal consequence of FMRP deficiency. FMRP was also recently linked to the microRNA pathway. These advances provide mechanistic insight into this disorder, and into learning and memory in general.
Collapse
Affiliation(s)
- Peng Jin
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | | | | |
Collapse
|
837
|
Abstract
Nucleo-cytoplasmic transport of RNA is one of many cellular pathways whose illumination has progressed hand in hand with understanding of retroviral mechanisms. A recent paper in Cell reports the involvement of an RNA helicase in the pathway by which HIV exports partially spliced and unspliced RNA out of the nucleus. This suggests the ubiquity of RNA helicases in RNA export from the nucleus, and has novel mechanistic implications.
Collapse
Affiliation(s)
- Andrew I Dayton
- Center for Biologics Evaluation and Research, Food and Drug Administration, USA.
| |
Collapse
|
838
|
Abstract
Specific mRNAs are transported to dendrites where their translation may modify synaptic plasticity. In this issue of Neuron, Kanai et al. use affinity chromatography and mass spectrometry to identify a large number of new factors that associate with kinesin, a molecular motor, and employ siRNA technology to demonstrate their importance for RNA transport in neurons.
Collapse
Affiliation(s)
- Joel D Richter
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| |
Collapse
|