Translational control in early development: CPEB, P-bodies and germinal granules

2008 ◽  
Vol 36 (4) ◽  
pp. 671-676 ◽  
Author(s):  
Nancy Standart ◽  
Nicola Minshall
Keyword(s):  
Early Development ◽  
Translational Control ◽  
Binding Proteins ◽  
Rna Binding ◽  
Binding Protein ◽  
Initiation Factor ◽  
Dependent Manner ◽  
Cytoplasmic Polyadenylation ◽  
P Bodies ◽  
Germinal Granules

Selective protein synthesis in oocytes, eggs and early embryos of many organisms drives several critical aspects of early development, including meiotic maturation and entry into mitosis, establishment of embryonic axes and cell fate determination. mRNA-binding proteins which (usually) recognize 3′-UTR (untranslated region) elements in target mRNAs influence the recruitment of the small ribosomal subunit to the 5′ cap. Probably the best studied such protein is CPEB (cytoplasmic polyadenylation element-binding protein), which represses translation in the oocyte in a cap-dependent manner, and activates translation in the meiotically maturing egg, via cytoplasmic polyadenylation. Co-immunoprecipitation and gel-filtration assays revealed that CPEB in Xenopus oocytes is in a very large RNP (ribonucleoprotein) complex and interacts with other RNA-binding proteins including Xp54 RNA helicase, Pat1, RAP55 (RNA-associated protein 55) and FRGY2 (frog germ cell-specific Y-box protein 2), as well as the eIF4E (eukaryotic initiation factor 4E)-binding protein 4E-T (eIF4E-transporter) and an ovary-specific eIF4E1b, which binds the cap weakly. Functional tests which implicate 4E-T and eIF4E1b in translational repression in oocytes led us to propose a model for the specific inhibition of translation of a target mRNA by a weak cap-binding protein. The components of the CPEB RNP complex are common to P-bodies (processing bodies), neuronal granules and germinal granules, suggesting that a highly conserved ‘masking’ complex operates in early development, neurons and somatic cells.

scholarly journals The viral nucleocapsid protein and the human RNA-binding protein Mex3A promote translation of the Andes orthohantavirus small mRNA

2021 ◽  
Vol 17 (9) ◽  
pp. e1009931
Author(s):  
Jorge Vera-Otarola ◽  
Estefania Castillo-Vargas ◽  
Jenniffer Angulo ◽  
Francisco M. Barriga ◽  
Eduard Batlle ◽  
...  
Keyword(s):  
Nucleocapsid Protein ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Initiation Factor ◽  
Cellular Proteins ◽  
Dependent Manner ◽  
The Andes ◽  
Viral Nucleocapsid

The capped Small segment mRNA (SmRNA) of the Andes orthohantavirus (ANDV) lacks a poly(A) tail. In this study, we characterize the mechanism driving ANDV-SmRNA translation. Results show that the ANDV-nucleocapsid protein (ANDV-N) promotes in vitro translation from capped mRNAs without replacing eukaryotic initiation factor (eIF) 4G. Using an RNA affinity chromatography approach followed by mass spectrometry, we identify the human RNA chaperone Mex3A (hMex3A) as a SmRNA-3’UTR binding protein. Results show that hMex3A enhances SmRNA translation in a 3’UTR dependent manner, either alone or when co-expressed with the ANDV-N. The ANDV-N and hMex3A proteins do not interact in cells, but both proteins interact with eIF4G. The hMex3A–eIF4G interaction showed to be independent of ANDV-infection or ANDV-N expression. Together, our observations suggest that translation of the ANDV SmRNA is enhanced by a 5’-3’ end interaction, mediated by both viral and cellular proteins.

scholarly journals Cell type-specific control of protein synthesis and proliferation by FGF-dependent signaling to the translation repressor 4E-BP

2016 ◽  
Vol 113 (27) ◽  
pp. 7545-7550 ◽  
Author(s):  
Rachel Ruoff ◽  
Olga Katsara ◽  
Victoria Kolupaeva
Keyword(s):  
Protein Synthesis ◽  
Translational Control ◽  
Bone Development ◽  
Binding Protein ◽  
Initiation Factor ◽  
Start Codon ◽  
Dependent Manner ◽  
Fgf Signaling ◽  
Cell Type

Regulation of protein synthesis plays a vital role in posttranscriptional modulation of gene expression. Translational control most commonly targets the initiation of protein synthesis: loading 40S ribosome complexes onto mRNA and AUG start codon recognition. This step is initiated by eukaryotic initiation factor 4E (eIF4E) (the m7GTP cap-binding protein), whose binding to eIF4G (a scaffolding subunit) and eIF4A (an ATP-dependent RNA helicase) leads to assembly of active eIF4F complex. The ability of eIF4E to recognize the cap is prevented by its binding to eIF4E binding protein (4E-BP), which thereby inhibits cap-dependent translation by sequestering eIF4E. The 4E-BP activity is, in turn, inhibited by mTORC1 [mTOR (the mechanistic target of rapamycin) complex 1] mediated phosphorylation. Here, we define a previously unidentified mechanism of mTOR-independent 4E-BP1 regulation that is used by chondrocytes upon FGF signaling. Chondrocytes are responsible for the formation of the skeleton long bones. Unlike the majority of cell types where FGF signaling triggers proliferation, chondrocytes respond to FGF with inhibition. We establish that FGF specifically suppresses protein synthesis in chondrocytes, but not in any other cells of mesenchymal origin. Furthermore, 4E-BP1 repressor activity is necessary not only for suppression of protein synthesis, but also for FGF-induced cell-cycle arrest. Importantly, FGF-induced changes in the 4E-BP1 activity observed in cell culture are likewise detected in vivo and reflect the action of FGF signaling on downstream targets during bone development. Thus, our findings demonstrate that FGF signaling differentially impacts protein synthesis through either stimulation or repression, in a cell-type–dependent manner, with 4E-BP1 being a key player.

scholarly journals The 36-kilodalton embryonic-type cytoplasmic polyadenylation element-binding protein in Xenopus laevis is ElrA, a member of the ELAV family of RNA-binding proteins.

1997 ◽  
Vol 17 (11) ◽  
pp. 6402-6409 ◽  
Author(s):  
L Wu ◽  
P J Good ◽  
J D Richter
Keyword(s):  
Xenopus Laevis ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Binding Protein ◽  
Dominant Negative ◽  
Cytoplasmic Polyadenylation ◽  
Element Binding Protein

The translational activation of several maternal mRNAs in Xenopus laevis is dependent on cytoplasmic poly(A) elongation. Messages harboring the UUUUUAU-type cytoplasmic polyadenylation element (CPE) in their 3' untranslated regions (UTRs) undergo polyadenylation and translation during oocyte maturation. This CPE is bound by the protein CPEB, which is essential for polyadenylation. mRNAs that have the poly(U)12-27 embryonic-type CPE (eCPE) in their 3' UTRs undergo polyadenylation and translation during the early cleavage and blastula stages. A 36-kDa eCPE-binding protein in oocytes and embryos has been identified by UV cross-linking. We now report that this 36-kDa protein is ElrA, a member of the ELAV family of RNA-binding proteins. The proteins are identical in size, antibody directed against ElrA immunoprecipitates the 36-kDa protein, and the two proteins have the same RNA binding specificity in vitro. C12 and activin receptor mRNAs, both of which contain eCPEs, are detected in immunoprecipitated ElrA-mRNP complexes from eggs and embryos. In addition, this in vivo interaction requires the eCPE. Although a number of experiments failed to define a role for ElrA in cytoplasmic polyadenylation, the expression of a dominant negative ElrA protein in embryos results in an exogastrulation phenotype. The possible functions of ElrA in gastrulation are discussed.

scholarly journals PTBP1 mRNA isoforms and regulation of their translation

2018 ◽  
Author(s):  
Luisa M Arake de Tacca ◽  
Mia C Pulos ◽  
Stephen N Floor ◽  
Jamie Cate
Keyword(s):  
Cell Cycle ◽  
Alternative Splicing ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Translation Initiation Factor ◽  
Protein Isoforms ◽  
Initiation Factor ◽  
Dependent Manner ◽  
Mrna Isoforms

Polypyrimidine tract-binding proteins (PTBPs) are RNA binding proteins that regulate a number of post-transcriptional events. Human PTBP1 transits between the nucleus and cytoplasm and is thought to regulate RNA processes in both. However, information about PTBP1 mRNA isoforms and regulation of PTPB1 expression remain incomplete. Here we mapped the major PTBP1 mRNA isoforms in HEK293T cells, and identified alternative 5' and 3' untranslated regions (5' UTRs, 3' UTRs) as well as alternative splicing patterns in the protein coding region. We also assessed how the observed PTBP1 mRNA isoforms contribute to PTBP1 expression in different phases of the cell cycle. Previously, PTBP1 mRNAs were shown to crosslink to eukaryotic translation initiation factor 3 (eIF3). We find that eIF3 binds differently to each PTBP1 mRNA isoform in a cell cycle-dependent manner. We also observe a strong correlation between eIF3 binding to PTBP1 mRNAs and repression of PTBP1 levels during the S phase of the cell cycle. Our results provide evidence of translational regulation of PTBP1 protein levels during the cell cycle, which may affect downstream regulation of alternative splicing and translation mediated by PTBP1 protein isoforms.

scholarly journals Viral and cellular mRNA-specific activators harness PABP and eIF4G to promote translation initiation downstream of cap binding

2017 ◽  
Vol 114 (24) ◽  
pp. 6310-6315 ◽  
Author(s):  
Richard W. P. Smith ◽  
Ross C. Anderson ◽  
Osmany Larralde ◽  
Joel W. S. Smith ◽  
Barbara Gorgoni ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Control Point ◽  
Ribosomal Subunit ◽  
Mrna Translation ◽  
Initiation Factor ◽  
Dependent Manner ◽  
Translational Activation

Regulation of mRNA translation is a major control point for gene expression and is critical for life. Of central importance is the complex between cap-bound eukaryotic initiation factor 4E (eIF4E), eIF4G, and poly(A) tail-binding protein (PABP) that circularizes mRNAs, promoting translation and stability. This complex is often targeted to regulate overall translation rates, and also by mRNA-specific translational repressors. However, the mechanisms of mRNA-specific translational activation by RNA-binding proteins remain poorly understood. Here, we address this deficit, focusing on a herpes simplex virus-1 protein, ICP27. We reveal a direct interaction with PABP that is sufficient to promote PABP recruitment and necessary for ICP27-mediated activation. PABP binds several translation factors but is primarily considered to activate translation initiation as part of the PABP–eIF4G–eIF4E complex that stimulates the initial cap-binding step. Importantly, we find that ICP27-PABP forms a complex with, and requires the activity of, eIF4G. Surprisingly, ICP27–PABP–eIF4G complexes act independently of the effects of PABP-eIF4G on cap binding to promote small ribosomal subunit recruitment. Moreover, we find that a cellular mRNA-specific regulator, Deleted in Azoospermia-like (Dazl), also employs the PABP–eIF4G interaction in a similar manner. We propose a mechanism whereby diverse RNA-binding proteins directly recruit PABP, in a non–poly(A) tail-dependent manner, to stimulate the small subunit recruitment step. This strategy may be particularly relevant to biological conditions associated with hypoadenylated mRNAs (e.g., germ cells/neurons) and/or limiting cytoplasmic PABP (e.g., viral infection, cell stress). This mechanism adds significant insight into our knowledge of mRNA-specific translational activation and the function of the PABP–eIF4G complex in translation initiation.

scholarly journals The Major RNA-Binding Protein ProQ Impacts Virulence Gene Expression inSalmonella entericaSerovar Typhimurium

mBio ◽  
2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Alexander J. Westermann ◽  
Elisa Venturini ◽  
Mikael E. Sellin ◽  
Konrad U. Förstner ◽  
Wolf-Dietrich Hardt ◽  
...  
Keyword(s):  
Gene Expression ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Enteric Bacteria ◽  
Host Cells ◽  
Dependent Manner ◽  
Control Of Gene Expression

ABSTRACTFinO domain proteins such as ProQ of the model pathogenSalmonella entericahave emerged as a new class of major RNA-binding proteins in bacteria. ProQ has been shown to target hundreds of transcripts, including mRNAs from many virulence regions, but its role, if any, in bacterial pathogenesis has not been studied. Here, using a Dual RNA-seq approach to profile ProQ-dependent gene expression changes asSalmonellainfects human cells, we reveal dysregulation of bacterial motility, chemotaxis, and virulence genes which is accompanied by altered MAPK (mitogen-activated protein kinase) signaling in the host. Comparison with the other major RNA chaperone inSalmonella, Hfq, reinforces the notion that these two global RNA-binding proteins work in parallel to ensure full virulence. Of newly discovered infection-associated ProQ-bound small noncoding RNAs (sRNAs), we show that the 3′UTR-derived sRNA STnc540 is capable of repressing an infection-induced magnesium transporter mRNA in a ProQ-dependent manner. Together, this comprehensive study uncovers the relevance of ProQ forSalmonellapathogenesis and highlights the importance of RNA-binding proteins in regulating bacterial virulence programs.IMPORTANCEThe protein ProQ has recently been discovered as the centerpiece of a previously overlooked “third domain” of small RNA-mediated control of gene expression in bacteria. Asin vitrowork continues to reveal molecular mechanisms, it is also important to understand how ProQ affects the life cycle of bacterial pathogens as these pathogens infect eukaryotic cells. Here, we have determined how ProQ shapesSalmonellavirulence and how the activities of this RNA-binding protein compare with those of Hfq, another central protein in RNA-based gene regulation in this and other bacteria. To this end, we apply global transcriptomics of pathogen and host cells during infection. In doing so, we reveal ProQ-dependent transcript changes in key virulence and host immune pathways. Moreover, we differentiate the roles of ProQ from those of Hfq during infection, for both coding and noncoding transcripts, and provide an important resource for those interested in ProQ-dependent small RNAs in enteric bacteria.

scholarly journals Translational Control by Neuroguidin, a Eukaryotic Initiation Factor 4E and CPEB Binding Protein

2006 ◽  
Vol 26 (11) ◽  
pp. 4277-4287 ◽  
Author(s):  
Mi-Young Jung ◽  
Lori Lorenz ◽  
Joel D. Richter
Keyword(s):  
Neural Crest ◽  
Neural Tube ◽  
Neural Development ◽  
Translational Control ◽  
Binding Protein ◽  
Neural Tube Closure ◽  
Initiation Factor ◽  
Dependent Manner ◽  
Eukaryotic Initiation Factor ◽  
Eukaryotic Initiation Factor 4E

ABSTRACT CPEB-mediated translation is important in early development and neuronal synaptic plasticity. Here, we describe a new eukaryotic initiation factor 4E (eIF4E) binding protein, Neuroguidin (Ngd), and its interaction with CPEB. In the mammalian nervous system, Ngd is detected as puncta in axons and dendrites and in growth cones and filopodia. Ngd contains three motifs that resemble those present in eIF4G, 4EBP, Cup, and Maskin, all of which are eIF4E binding proteins. Ngd binds eIF4E directly, and all three motifs must be deleted to abrogate the interaction between these two proteins. In injected Xenopus oocytes, Ngd binds CPEB and, most importantly, represses translation in a cytoplasmic polyadenylation element (CPE)-dependent manner. In Xenopus embryos, Ngd is found in both neural tube and neural crest cells. The injection of morpholino-containing antisense oligonucleotides directed against ngd mRNA disrupts neural tube closure and neural crest migration; however, the wild-type phenotype is restored by the injection of a rescuing ngd mRNA. These data suggest that Ngd guides neural development by regulating the translation of CPE-containing mRNAs.

scholarly journals Phosphorylation of the RNA-binding protein Dazl by MAPKAP kinase 2 regulates spermatogenesis

2016 ◽  
Vol 27 (15) ◽  
pp. 2341-2350 ◽  
Author(s):  
Patrick A. Williams ◽  
Michael S. Krug ◽  
Emily A. McMillan ◽  
Jasmine D. Peake ◽  
Tara L. Davis ◽  
...  
Keyword(s):  
Translational Control ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Negative Regulator ◽  
Transgenic Expression ◽  
Male Germline ◽  
Deleted In Azoospermia

Developing male germ cells are exquisitely sensitive to environmental insults such as heat and oxidative stress. An additional characteristic of these cells is their unique dependence on RNA-binding proteins for regulating posttranscriptional gene expression and translational control. Here we provide a mechanistic link unifying these two features. We show that the germ cell–specific RNA-binding protein deleted in azoospermia-like (Dazl) is phosphorylated by MAPKAP kinase 2 (MK2), a stress-induced protein kinase activated downstream of p38 MAPK. We demonstrate that phosphorylation of Dazl by MK2 on an evolutionarily conserved serine residue inhibits its interaction with poly(A)-binding protein, resulting in reduced translation of Dazl-regulated target RNAs. We further show that transgenic expression of wild-type human Dazl but not a phosphomimetic form in the Drosophila male germline can restore fertility to flies deficient in boule, the Drosophila orthologue of human Dazl. These results illuminate a novel role for MK2 in spermatogenesis, expand the repertoire of RNA-binding proteins phosphorylated by this kinase, and suggest that signaling by the p38-MK2 pathway is a negative regulator of spermatogenesis via phosphorylation of Dazl.

Identification of RNA-binding proteins specific to Xenopus Eg maternal mRNAs: association with the portion of Eg2 mRNA that promotes deadenylation in embryos

Development ◽  
1992 ◽  
Vol 116 (4) ◽  
pp. 1193-1202
Author(s):  
V. Legagneux ◽  
P. Bouvet ◽  
F. Omilli ◽  
S. Chevalier ◽  
H.B. Osborne
Keyword(s):  
Untranslated Region ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Binding Protein ◽  
Untranslated Regions ◽  
Cytoplasmic Polyadenylation ◽  
Element Binding Protein ◽  
Maternal Mrnas ◽  
Post Transcriptional Regulation

Maternal Xenopus Eg mRNAs have been previously identified as transcripts that are specifically deadenylated after fertilization and degraded after the mid blastula transition. Destabilizing cis sequences were previously localised in the 3′ untranslated region of Eg2 mRNA. In order to characterize possible trans-acting factors which are involved in the post-transcriptional regulation of Eg mRNAs, gel-shift and u.v. cross-linking experiments were performed, which allowed the identification of a p53-p55 RNA-binding protein doublet specific for the 3′ untranslated regions of Eg mRNAs. These p53-p55 proteins do not bind to the 3′ untranslated regions of either ornithine decarboxylase or phosphatase 2Ac mRNAs, which remain polyadenylated in embryos. These novel RNA-binding proteins are distinct from the cytoplasmic polyadenylation element-binding protein that controls the polyadenylation of maternal mRNAs in maturing Xenopus oocytes, and from previously identified thermoresistant RNA-binding proteins present in oocyte mRNP storage particles. The p53-p55 bind a portion of the Eg2 mRNA 3′ untranslated region, distinct from the previously identified destabilizing region, that is able to confer the postfertilization deadenylation of CAT-coding chimeric mRNAs. This suggests that the p53-p55 RNA-binding proteins are good candidates for trans-acting factors involved in the deadenylation of Eg mRNAs in Xenopus embryos.

scholarly journals CPB-3 and CGH-1 localize to motile particles within dendrites in C. elegans PVD sensory neurons

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Kathrin Spendier ◽  
Eugenia C. Olesnicky ◽  
Daniel Forand ◽  
Margaret Wolf ◽  
Darrell J. Killian
Keyword(s):  
Translational Control ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Rna Helicases ◽  
Cytoplasmic Polyadenylation ◽  
C Elegans ◽  
Mrna Targets ◽  
Dead Box ◽  
Dendrite Development

Abstract Objective RNA-binding proteins (RBPs) are important regulators of gene expression that influence mRNA splicing, stability, localization, transport, and translational control. In particular, RBPs play an important role in neurons, which have a complex morphology. Previously, we showed that there are many RBPs that play a conserved role in dendrite development in Drosophila dendritic arborization neurons and Caenorhabditis elegans (C. elegans) PVD neurons including the cytoplasmic polyadenylation element binding proteins (CPEBs), Orb in Drosophila and CPB-3 in C. elegans, and the DEAD box RNA helicases, Me31B in Drosophila and CGH-1 in C. elegans. During these studies, we observed that fluorescently-labeled CPB-3 and CGH-1 localize to cytoplasmic particles that are motile, and our research aims to further characterize these RBP-containing particles in live neurons. Results Here we extend on previous work to show that CPB-3 and CGH-1 localize to motile particles within dendrites that move at a speed consistent with microtubule-based transport. This is consistent with a model in which CPB-3 and CGH-1 influence dendrite development through the transport and localization of their mRNA targets. Moreover, CPB-3 and CGH-1 rarely localize to the same particles suggesting that these RBPs function in discrete ribonucleoprotein particles (RNPs) that may regulate distinct mRNAs.

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