Fragile X family members have important and non-overlapping functions

2011 ◽  
Vol 2 (5) ◽  
pp. 343-352 ◽  
Author(s):  
Claudia Winograd ◽  
Stephanie Ceman
Keyword(s):  
Nuclear Export ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Fragile X ◽  
Family Members ◽  
Nuclear Localization Sequence ◽  
Interaction Domain ◽  
Protein Protein Interaction ◽  
Localization Sequence ◽  
Protein Functional Domains

AbstractThe fragile X family of genes encodes a small family of RNA binding proteins including FMRP, FXR1P and FXR2P that were identified in the 1990s. All three members are encoded by 17 exons and show alternative splicing at the 3′ ends of their respective transcripts. They share significant homology in the protein functional domains, including the Tudor domains, the nuclear localization sequence, a protein-protein interaction domain, the KH1 and KH2 domains and the nuclear export sequence. Fragile X family members are found throughout the animal kingdom, although all three members are not consistently present in species outside of mammals: only two family members are present in the avian species examined, Gallus gallus and Taeniopygia guttata, and in the frog Xenopus tropicalis. Although present in many tissues, the functions of the fragile X family members differ, which are particularly evident in knockout studies performed in animals. The fragile X family members play roles in normal neuronal function and in the case of FXR1, in muscle function.

Domain necessary for Drosophila ELAV nuclear localization: function requires nuclear ELAV

1999 ◽  
Vol 112 (24) ◽  
pp. 4501-4512 ◽  
Author(s):  
Y.M. Yannoni ◽  
K. White
Keyword(s):  
Nuclear Localization ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Nuclear Localization Sequence ◽  
Rna Recognition ◽  
Rna Recognition Motifs ◽  
Mutant Proteins ◽  
Localization Sequence ◽  
Recognition Motifs

The neuron specific Drosophila ELAV protein belongs to the ELAV family of RNA binding proteins which are characterized by three highly conserved RNA recognition motifs, an N-terminal domain, and a hinge region between the second and third RNA recognition motifs. Despite their highly conserved RNA recognition motifs the ELAV family members are a group of proteins with diverse posttranscriptional functions including splicing regulation, mRNA stability and translatability and have a variety of subcellular localizations. The role of the ELAV hinge in localization and function was examined using transgenes encoding ELAV hinge deletions, in vivo. Subcellular localization of the hinge mutant proteins revealed that residues between amino acids 333–374 are necessary for nuclear localization. This delineated sequence has no significant homology to classical nuclear localization sequences, but it is similar to the recently characterized nucleocytoplasmic shuttling sequence, the HNS, from a human ELAV family member, HuR. This defined sequence, however, was insufficient for nuclear localization as tested using hinge-GFP fusion proteins. Functional assays revealed that mutant proteins that fail to localize to the nucleus are unable to provide ELAV vital function, but their function is significantly restored when translocated into the nucleus by a heterologous nuclear localization sequence tag.

scholarly journals Fragile X Mental Retardation Protein FMRP Binds mRNAs in the Nucleus

2008 ◽  
Vol 29 (1) ◽  
pp. 214-228 ◽  
Author(s):  
Miri Kim ◽  
Michel Bellini ◽  
Stephanie Ceman
Keyword(s):  
Mental Retardation ◽  
Nuclear Export ◽  
Rna Binding ◽  
Fragile X ◽  
Simian Virus 40 ◽  
Nuclear Localization Sequence ◽  
Dependent Manner ◽  
Nuclear Export Sequence ◽  
Fragile X Mental Retardation ◽  
Mental Retardation Protein

ABSTRACT The fragile X mental retardation protein FMRP is an RNA binding protein that associates with a large collection of mRNAs. Since FMRP was previously shown to be a nucleocytoplasmic shuttling protein, we examined the hypothesis that FMRP binds its cargo mRNAs in the nucleus. The enhanced green fluorescent protein-tagged FMRP construct (EGFP-FMRP) expressed in Cos-7 cells was efficiently exported from the nucleus in the absence of its nuclear export sequence and in the presence of a strong nuclear localization sequence (the simian virus 40 [SV40] NLS), suggesting an efficient mechanism for nuclear export. We hypothesized that nuclear FMRP exits the nucleus through its bound mRNAs. Using silencing RNAs to the bulk mRNA exporter Tap/NXF1, we observed a significantly increased number of cells containing EGFP-FMRP in the nucleus, which was further augmented by removal of FMRP's nuclear export sequence. Nuclear-retained SV40-FMRP could be released upon treatment with RNase. Further, Tap/NXF1 coimmunoprecipitated with EGFP-FMRP in an RNA-dependent manner and contained the FMR1 mRNA. To determine whether FMRP binds pre-mRNAs cotranscriptionally, we expressed hemagglutinin-SV40 FMRP in amphibian oocytes and found it, as well as endogenous Xenopus FMRP, on the active transcription units of lampbrush chromosomes. Collectively, our data provide the first lines of evidence that FMRP binds mRNA in the nucleus.

scholarly journals Phosphorylation and nuclear transit modulate the balance between normal function and terminal aggregation of the yeast RNA-binding protein Ssd1

2017 ◽  
Vol 28 (22) ◽  
pp. 3057-3069 ◽  
Author(s):  
Cornelia Kurischko ◽  
James R. Broach
Keyword(s):  
Rna Polymerase Ii ◽  
Nuclear Export ◽  
Rna Binding ◽  
Binding Protein ◽  
Neurological Diseases ◽  
Rna Binding Protein ◽  
Normal Function ◽  
Nuclear Localization Sequence ◽  
P Bodies ◽  
Localization Sequence

Yeast Ssd1 is an RNA-binding protein that shuttles between the nucleus and cytoplasm. Ssd1 interacts with its target mRNAs initially during transcription by binding through its N-terminal prion-like domain (PLD) to the C-terminal domain of RNA polymerase II. Ssd1 subsequently targets mRNAs acquired in the nucleus either to daughter cells for translation or to stress granules (SGs) and P-bodies (PBs) for mRNA storage or decay. Here we show that PB components assist in the nuclear export of Ssd1and subsequent targeting of Ssd1 to PB sites in the cytoplasm. In the absence of import into the nucleus, Ssd1 fails to associate with PBs in the cytoplasm but rather is targeted to cytosolic insoluble protein deposits (IPODs). The association of Ssd1 either with IPOD sites or with PB/SG requires the PLD, whose activity is differentially regulated by the Ndr/LATS family kinase, Cbk1: phosphorylation suppresses PB/SG association but enhances IPOD formation. This regulation likely accrues from a phosphorylation-sensitive nuclear localization sequence located in the PLD. The results presented here may inform our understanding of aggregate formation by RBP in certain neurological diseases.

scholarly journals Characterization of dFMR1, a Drosophila melanogaster Homolog of the Fragile X Mental Retardation Protein

2000 ◽  
Vol 20 (22) ◽  
pp. 8536-8547 ◽  
Author(s):  
Lili Wan ◽  
Thomas C. Dockendorff ◽  
Thomas A. Jongens ◽  
Gideon Dreyfuss
Keyword(s):  
Drosophila Melanogaster ◽  
Mental Retardation ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Apoptotic Cell ◽  
Fragile X ◽  
Ribosomal Subunit ◽  
Mutant Form ◽  
Interaction Domain

ABSTRACT Fragile X syndrome is the most common inherited form of mental retardation. It is caused by loss of FMR1 gene activity due to either lack of expression or expression of a mutant form of the protein. In mammals, FMR1 is a member of a small protein family that consists of FMR1, FXR1, and FXR2. All three members bind RNA and contain sequence motifs that are commonly found in RNA-binding proteins, including two KH domains and an RGG box. The FMR1/FXR proteins also contain a 60S ribosomal subunit interaction domain and a protein-protein interaction domain which mediates homomer and heteromer formation with each family member. Nevertheless, the specific molecular functions of FMR1/FXR proteins are unknown. Here we report the cloning and characterization of a Drosophila melanogaster homolog of the mammalian FMR1/FXR gene family. This first invertebrate homolog, termed dfmr1, has a high degree of amino acid sequence identity/similarity with the defined functional domains of the FMR1/FXR proteins. The dfmr1 product binds RNA and is similar in subcellular localization and embryonic expression pattern to the mammalian FMR1/FXR proteins. Overexpression of dfmr1 driven by the UAS-GAL4 system leads to apoptotic cell loss in all adult Drosophila tissues examined. This phenotype is dependent on the activity of the KH domains. The ability to induce a dominant phenotype by overexpressing dfmr1 opens the possibility of using genetic approaches in Drosophila to identify the pathways in which the FMR1/FXR proteins function.

RNA-Binding Proteins and Translation in Neurodegenerative Disease

2020 ◽  
Author(s):  
Kent E. Duncan
Keyword(s):  
Neurodegenerative Diseases ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Fragile X ◽  
Potential Contribution ◽  
Fused In Sarcoma ◽  
Specific Mrnas ◽  
Ataxia Syndrome ◽  
Research Frontiers

Both RNA-binding proteins (RBPs) and translation are increasingly implicated in several neurodegenerative diseases, but their specific roles in promoting disease are not yet fully defined. This chapter critically evaluates the evidence that altered translation of specific mRNAs mediated by RNA-binding proteins plays an important role in driving specific neurodegenerative diseases. First, diseases are discussed where a causal role for RNA-binding proteins in disease appears solid, but whether this involves altered translation is less clear. The main foci here are TAR DNA-binding protein (TDP-43) and fused in sarcoma (FUS) in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Subsequently, diseases are presented where altered translation is believed to contribute, but involvement of RNA-binding proteins is less clear. These include Huntington’s and other repeat expansion disorders such as fragile X tremor/ataxia syndrome (FXTAS), where repeat-induced non-AUG-initiated (RAN) translation is a focus. The potential contribution of both canonical and non-canonical RBPs to altered translation in Parkinson’s disease is discussed. The chapter closes by proposing key research frontiers for the field to explore and outlining methodological advances that could help to address them.

scholarly journals Secondary structural choice of DNA and RNA associated with CGG/CCG trinucleotide repeat expansion rationalizes the RNA misprocessing in FXTAS

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yogeeshwar Ajjugal ◽  
Narendar Kolimi ◽  
Thenmalarchelvi Rathinavelan
Keyword(s):  
Rna Binding ◽  
Trinucleotide Repeat ◽  
Rna Binding Proteins ◽  
Fragile X ◽  
Repeat Expansion ◽  
Mobility Shift ◽  
Cgg Repeat ◽  
Dna And Rna ◽  
Structural Choice ◽  
Sense Strand

AbstractCGG tandem repeat expansion in the 5′-untranslated region of the fragile X mental retardation-1 (FMR1) gene leads to unusual nucleic acid conformations, hence causing genetic instabilities. We show that the number of G…G (in CGG repeat) or C…C (in CCG repeat) mismatches (other than A…T, T…A, C…G and G…C canonical base pairs) dictates the secondary structural choice of the sense and antisense strands of the FMR1 gene and their corresponding transcripts in fragile X-associated tremor/ataxia syndrome (FXTAS). The circular dichroism (CD) spectra and electrophoretic mobility shift assay (EMSA) reveal that CGG DNA (sense strand of the FMR1 gene) and its transcript favor a quadruplex structure. CD, EMSA and molecular dynamics (MD) simulations also show that more than four C…C mismatches cannot be accommodated in the RNA duplex consisting of the CCG repeat (antisense transcript); instead, it favors an i-motif conformational intermediate. Such a preference for unusual secondary structures provides a convincing justification for the RNA foci formation due to the sequestration of RNA-binding proteins to the bidirectional transcripts and the repeat-associated non-AUG translation that are observed in FXTAS. The results presented here also suggest that small molecule modulators that can destabilize FMR1 CGG DNA and RNA quadruplex structures could be promising candidates for treating FXTAS.

scholarly journals Characterization of a beta-actin mRNA zipcode-binding protein.

1997 ◽  
Vol 17 (4) ◽  
pp. 2158-2165 ◽  
Author(s):  
A F Ross ◽  
Y Oleynikov ◽  
E H Kislauskis ◽  
K L Taneja ◽  
R H Singer
Keyword(s):  
Nuclear Export ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Binding Protein ◽  
Affinity Purification ◽  
Nuclear Export Signal ◽  
Degenerate Primers ◽  
Band Shift ◽  
Beta Actin ◽  
Actin Mrna

Localization of beta-actin mRNA to the leading edge of fibroblasts requires the presence of conserved elements in the 3' untranslated region of the mRNA, including a 54-nucleotide element which has been termed the "zipcode" (E. Kislauskis, X. Zhu, and R. H. Singer, J. Cell Biol. 127:441-451, 1994). In order to identify proteins which bind to the zipcode and possibly play a role in localization, we performed band-shift mobility assays, UV cross-linking, and affinity purification experiments. A protein of 68 kDa was identified which binds to the proximal (to the coding region) half of the zipcode with high specificity (ZBP-1). Microsequencing provided unique peptide sequences of approximately 15 residues each. Degenerate primers corresponding to the codons derived from the peptides were synthesized and used for PCR amplification. Screening of a chicken cDNA library resulted in isolation of several clones providing a DNA sequence encoding a 67.7-kDa protein with regions homologous to several RNA-binding proteins, such as hnRNP E1 and E2, and with consensus mRNA recognition motif with RNP1 and 2 motifs and a putative REV-like nuclear export signal. Antipeptide antibodies were raised in rabbits which bound to ZBP-1 and coimmunoprecipitated proteins of 120 and 25 kDa. The 120-kDa protein was also obtained by affinity purification with the RNA zipcode sequence, along with a 53-kDa protein, but the 25-kDa protein appeared only in immunoprecipitations. Mutation of one of the conserved sequences within the zipcode, an ACACCC element in its proximal half, greatly reduced its protein binding and localization properties. These data suggest that the 68-kDa ZBP-1 we have isolated and cloned is an RNA-binding protein that functions within a complex to localize beta-actin mRNA.

scholarly journals RNA-binding proteins of the NXF (nuclear export factor) family and their connection with the cytoskeleton

Cytoskeleton ◽  
2017 ◽  
Vol 74 (4) ◽  
pp. 161-169 ◽  
Author(s):  
L. A. Mamon ◽  
V. R. Ginanova ◽  
S. F. Kliver ◽  
A. O. Yakimova ◽  
A. A. Atsapkina ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins

scholarly journals Matrin3: Disorder and ALS Pathogenesis

2022 ◽  
Vol 8 ◽  
Author(s):  
Ahmed Salem ◽  
Carter J. Wilson ◽  
Benjamin S. Rutledge ◽  
Allison Dilliott ◽  
Sali Farhan ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Binding Proteins ◽  
Rna Binding ◽  
Nuclear Dna ◽  
Neurodegenerative Disorder ◽  
Rna Binding Proteins ◽  
Binding Protein ◽  
Intrinsically Disordered ◽  
Intrinsically Disordered Regions ◽  
Disordered Regions

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by the degeneration of both upper and lower motor neurons in the brain and spinal cord. ALS is associated with protein misfolding and inclusion formation involving RNA-binding proteins, including TAR DNA-binding protein (TDP-43) and fused in sarcoma (FUS). The 125-kDa Matrin3 is a highly conserved nuclear DNA/RNA-binding protein that is implicated in many cellular processes, including binding and stabilizing mRNA, regulating mRNA nuclear export, modulating alternative splicing, and managing chromosomal distribution. Mutations in MATR3, the gene encoding Matrin3, have been identified as causal in familial ALS (fALS). Matrin3 lacks a prion-like domain that characterizes many other ALS-associated RNA-binding proteins, including TDP-43 and FUS, however, our bioinformatics analyses and preliminary studies document that Matrin3 contains long intrinsically disordered regions that may facilitate promiscuous interactions with many proteins and may contribute to its misfolding. In addition, these disordered regions in Matrin3 undergo numerous post-translational modifications, including phosphorylation, ubiquitination and acetylation that modulate the function and misfolding of the protein. Here we discuss the disordered nature of Matrin3 and review the factors that may promote its misfolding and aggregation, two elements that might explain its role in ALS pathogenesis.

scholarly journals SAM68: Signal Transduction and RNA Metabolism in Human Cancer

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Paola Frisone ◽  
Davide Pradella ◽  
Anna Di Matteo ◽  
Elisa Belloni ◽  
Claudia Ghigna ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Signal Transduction ◽  
Nuclear Export ◽  
Cell Biology ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Splice Variants ◽  
Human Cancer ◽  
Rna Metabolism ◽  
Regulatory Sequences

Alterations in expression and/or activity of splicing factors as well as mutations incis-acting splicing regulatory sequences contribute to cancer phenotypes. Genome-wide studies have revealed more than 15,000 tumor-associated splice variants derived from genes involved in almost every aspect of cancer cell biology, including proliferation, differentiation, cell cycle control, metabolism, apoptosis, motility, invasion, and angiogenesis. In the past decades, several RNA binding proteins (RBPs) have been implicated in tumorigenesis. SAM68 (SRC associated in mitosis of 68 kDa) belongs to the STAR (signal transduction and activation of RNA metabolism) family of RBPs. SAM68 is involved in several steps of mRNA metabolism, from transcription to alternative splicing and then to nuclear export. Moreover, SAM68 participates in signaling pathways associated with cell response to stimuli, cell cycle transitions, and viral infections. Recent evidence has linked this RBP to the onset and progression of different tumors, highlighting misregulation of SAM68-regulated splicing events as a key step in neoplastic transformation and tumor progression. Here we review recent studies on the role of SAM68 in splicing regulation and we discuss its contribution to aberrant pre-mRNA processing in cancer.

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