scholarly journals Rapid Deadenylation and Poly(A)-Dependent Translational Repression Mediated by the Caenorhabditis elegans tra-2 3′ Untranslated Region in XenopusEmbryos

2000 ◽  
Vol 20 (6) ◽  
pp. 2129-2137 ◽  
Author(s):  
Sunnie R. Thompson ◽  
Elizabeth B. Goodwin ◽  
Marvin Wickens
Keyword(s):  
Caenorhabditis Elegans ◽  
Cell Fate ◽  
Translational Control ◽  
Untranslated Region ◽  
Specific Binding ◽  
Translational Repression ◽  
Female Development ◽  
C Elegans ◽  
Egg Extracts ◽  
Eukaryotic Mrnas

ABSTRACT The 3′ untranslated region (3′UTR) of many eukaryotic mRNAs is essential for their control during early development. Negative translational control elements in 3′UTRs regulate pattern formation, cell fate, and sex determination in a variety of organisms.tra-2 mRNA in Caenorhabditis elegans is required for female development but must be repressed to permit spermatogenesis in hermaphrodites. Translational repression oftra-2 mRNA in C. elegans is mediated by tandemly repeated elements in its 3′UTR; these elements are called TGEs (for tra-2 and GLI element). To examine the mechanism of TGE-mediated repression, we first demonstrate that TGE-mediated translational repression occurs in Xenopus embryos and thatXenopus egg extracts contain a TGE-specific binding factor. Translational repression by the TGEs requires that the mRNA possess a poly(A) tail. We show that in C. elegans, the poly(A) tail of wild-type tra-2 mRNA is shorter than that of a mutant mRNA lacking the TGEs. To determine whether TGEs regulate poly(A) length directly, synthetic tra-2 3′UTRs with and without the TGEs were injected into Xenopus embryos. We find that TGEs accelerate the rate of deadenylation and permit the last 15 adenosines to be removed from the RNA, resulting in the accumulation of fully deadenylated molecules. We conclude that TGE-mediated translational repression involves either interference with poly(A)'s function in translation and/or regulated deadenylation.

scholarly journals Proteolysis in Caenorhabditis elegans sex determination: cleavage of TRA-2A by TRA-3

2000 ◽  
Vol 14 (8) ◽  
pp. 901-906
Author(s):  
Sharon B. Sokol ◽  
Patricia E. Kuwabara
Keyword(s):  
Caenorhabditis Elegans ◽  
Membrane Protein ◽  
Cell Fate ◽  
Calcium Binding ◽  
Female Development ◽  
C Elegans ◽  
Calcium Dependent ◽  
Substrate Cleavage ◽  
Ef Hands

The Caenorhabditis elegans tra-3 gene promotes female development in XX hermaphrodites and encodes an atypical calpain regulatory protease lacking calcium-binding EF hands. We report that despite the absence of EF hands, TRA-3 has calcium-dependent proteolytic activity and its proteolytic domain is essential for in vivo function. We show that the membrane protein TRA-2A, which promotes XX female development by repressing the masculinizing protein FEM-3, is a TRA-3 substrate. Cleavage of TRA-2A by TRA-3 generates a peptide predicted to have feminizing activity. These results indicate that proteolysis regulated by calcium may control some aspects of sexual cell fate in C. elegans.

scholarly journals Interaction of three Caenorhabditis elegans isoforms of translation initiation factor eIF4E with mono- and trimethylated mRNA 5' cap analogues.

2002 ◽  
Vol 49 (3) ◽  
pp. 671-682 ◽  
Author(s):  
Alicja Stachelska ◽  
Zbigniew Wieczorek ◽  
Katarzyna Ruszczyńska ◽  
Ryszard Stolarski ◽  
Monika Pietrzak ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Fluorescence Quenching ◽  
Translation Initiation ◽  
Translational Control ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Iodide Ions ◽  
C Elegans ◽  
Eukaryotic Mrnas ◽  
Mechanism Of Recognition

Translation initiation factor eIF4E binds the m(7)G cap of eukaryotic mRNAs and mediates recruitment of mRNA to the ribosome during cap-dependent translation initiation. This event is the rate-limiting step of translation and a major target for translational control. In the nematode Caenorhabditis elegans, about 70% of genes express mRNAs with an unusual cap structure containing m(3)(2,2,7)G, which is poorly recognized by mammalian eIF4E. C. elegans expresses five isoforms of eIF4E (IFE-1, IFE-2, etc.). Three of these (IFE-3, IFE-4 and IFE-5) were investigated by means of spectroscopy and structural modelling based on mouse eIF4E bound to m(7)GDP. Intrinsic fluorescence quenching of Trp residues in the IFEs by iodide ions indicated structural differences between the apo and m(7)G cap bound proteins. Fluorescence quenching by selected cap analogues showed that only IFE-5 forms specific complexes with both m(7)G- and m(3)(2,2,7)G-containing caps (K(as) 2 x 10(6) M(-1) to 7 x 10(6) M(-1)) whereas IFE-3 and IFE-4 discriminated strongly in favor of m(7)G-containing caps. These spectroscopic results quantitatively confirm earlier qualitative data derived from affinity chromatography. The dependence of K(as) on pH indicated optimal cap binding of IFE-3, IFE-4 and IFE-5 at pH 7.2, lower by 0.4 pH units than that of eIF4E from human erythrocytes. These results provide insight into the molecular mechanism of recognition of structurally different caps by the highly homologous IFEs.

A genetic pathway for regulation of tra-2 translation

Development ◽  
1997 ◽  
Vol 124 (3) ◽  
pp. 749-758 ◽  
Author(s):  
E.B. Goodwin ◽  
K. Hofstra ◽  
C.A. Hurney ◽  
S. Mango ◽  
J. Kimble
Keyword(s):  
Translational Control ◽  
Direct Repeat ◽  
Postembryonic Development ◽  
Early Embryo ◽  
Translational Repression ◽  
Female Development ◽  
Normal Pattern ◽  
Repeat Elements ◽  
Translation Repression ◽  
Translational Level

In Caenorhabditis elegans, the tra-2 sex-determining gene is regulated at the translational level by two 28 nt direct repeat elements (DREs) located in its 3′ untranslated region (3′UTR). DRF is a factor that binds the DREs and may be a trans-acting translational regulator of tra-2. Here we identify two genes that are required for the normal pattern of translational control. A newly identified gene, called laf-1, is required for translational repression by the tra-2 3′UTR. In addition, the sex-determining gene, tra-3, appears to promote female development by freeing tra-2 from laf-1 repression. Finally, we show that DRF activity correlates with translational repression of tra-2 during development and that tra-3 regulates DRF activity. We suggest that tra-3 may promote female development by releasing tra-2 from translation repression by laf-1 and that translational control is important for proper sex determination--both in the early embryo and during postembryonic development.

scholarly journals Genetic control of programmed cell death in the Caenorhabditis elegans hermaphrodite germline

Development ◽  
1999 ◽  
Vol 126 (5) ◽  
pp. 1011-1022 ◽  
Author(s):  
T.L. Gumienny ◽  
E. Lambie ◽  
E. Hartwieg ◽  
H.R. Horvitz ◽  
M.O. Hengartner
Keyword(s):  
Cell Death ◽  
Caenorhabditis Elegans ◽  
Germ Cell ◽  
Somatic Cell ◽  
Cell Fate ◽  
Germ Cells ◽  
Mapk Pathway ◽  
Apoptotic Cell ◽  
C Elegans ◽  
Pathway Activation

Development of the nematode Caenorhabditis elegans is highly reproducible and the fate of every somatic cell has been reported. We describe here a previously uncharacterized cell fate in C. elegans: we show that germ cells, which in hermaphrodites can differentiate into sperm and oocytes, also undergo apoptotic cell death. In adult hermaphrodites, over 300 germ cells die, using the same apoptotic execution machinery (ced-3, ced-4 and ced-9) as the previously described 131 somatic cell deaths. However, this machinery is activated by a distinct pathway, as loss of egl-1 function, which inhibits somatic cell death, does not affect germ cell apoptosis. Germ cell death requires ras/MAPK pathway activation and is used to maintain germline homeostasis. We suggest that apoptosis eliminates excess germ cells that acted as nurse cells to provide cytoplasmic components to maturing oocytes.

Temporal regulation of the Xenopus FGF receptor in development: a translation inhibitory element in the 3′ untranslated region

Development ◽  
1995 ◽  
Vol 121 (6) ◽  
pp. 1775-1785 ◽  
Author(s):  
E.P. Robbie ◽  
M. Peterson ◽  
E. Amaya ◽  
T.J. Musci
Keyword(s):  
Protein Interactions ◽  
Translational Control ◽  
Untranslated Region ◽  
Rna Stability ◽  
Immature Oocyte ◽  
Translational Repression ◽  
Meiotic Maturation ◽  
Fgf Receptor ◽  
Cis Acting ◽  
Maternal Mrna

Early frog embryogenesis depends on a maternal pool of mRNA to execute critical intercellular signalling events. FGF receptor-1, which is required for normal development, is stored as a stable, untranslated maternal mRNA transcript in the fully grown immature oocyte, but is translationally activated at meiotic maturation. We have identified a short cis-acting element in the FGF receptor 3′ untranslated region that inhibits translation of synthetic mRNA. This inhibitory element is sufficient to inhibit translation of heterologous reporter mRNA in the immature oocyte without changing RNA stability. Deletion of the poly(A) tract or polyadenylation signal sequences does not affect translational inhibition by this element. At meiotic maturation, we observe the reversal of translational repression mediated by the inhibitory element, mimicking that seen with endogenous maternal FGF receptor mRNA at meiosis. In addition, the activation of synthetic transcripts at maturation does not appear to require poly(A) lengthening. We also show that an oocyte cytoplasmic protein specifically binds the 3′ inhibitory element, suggesting that translational repression of Xenopus FGF receptor-1 maternal mRNA in the oocytes is mediated by RNA-protein interactions. These data describe a mechanism of translational control that appears to be independent of poly(A) changes.

Apontic binds the translational repressor Bruno and is implicated in regulation of oskar mRNA translation

Development ◽  
1999 ◽  
Vol 126 (6) ◽  
pp. 1129-1138 ◽  
Author(s):  
Y.S. Lie ◽  
P.M. Macdonald
Keyword(s):  
Translational Control ◽  
Untranslated Region ◽  
Rna Binding ◽  
Mrna Translation ◽  
Posterior Pole ◽  
Translational Repression ◽  
Yeast Two Hybrid ◽  
Functional Interaction ◽  
Translational Repressor ◽  
Two Hybrid

The product of the oskar gene directs posterior patterning in the Drosophila oocyte, where it must be deployed specifically at the posterior pole. Proper expression relies on the coordinated localization and translational control of the oskar mRNA. Translational repression prior to localization of the transcript is mediated, in part, by the Bruno protein, which binds to discrete sites in the 3′ untranslated region of the oskar mRNA. To begin to understand how Bruno acts in translational repression, we performed a yeast two-hybrid screen to identify Bruno-interacting proteins. One interactor, described here, is the product of the apontic gene. Coimmunoprecipitation experiments lend biochemical support to the idea that Bruno and Apontic proteins physically interact in Drosophila. Genetic experiments using mutants defective in apontic and bruno reveal a functional interaction between these genes. Given this interaction, Apontic is likely to act together with Bruno in translational repression of oskar mRNA. Interestingly, Apontic, like Bruno, is an RNA-binding protein and specifically binds certain regions of the oskar mRNA 3′ untranslated region.

scholarly journals Combining single-cell RNA-sequencing with a molecular atlas unveils new markers for Caenorhabditis elegans neuron classes

2020 ◽  
Author(s):  
Ramiro Lorenzo ◽  
Michiho Onizuka ◽  
Matthieu Defrance ◽  
Patrick Laurent
Keyword(s):  
Caenorhabditis Elegans ◽  
Single Cell ◽  
Rna Sequencing ◽  
Cell Fate ◽  
Single Neuron ◽  
Genetic Manipulations ◽  
C Elegans ◽  
Single Cell Rna Sequencing ◽  
Normal Differentiation

Abstract Single-cell RNA-sequencing (scRNA-seq) of the Caenorhabditis elegans nervous system offers the unique opportunity to obtain a partial expression profile for each neuron within a known connectome. Building on recent scRNA-seq data and on a molecular atlas describing the expression pattern of ∼800 genes at the single cell resolution, we designed an iterative clustering analysis aiming to match each cell-cluster to the ∼100 anatomically defined neuron classes of C. elegans. This heuristic approach successfully assigned 97 of the 118 neuron classes to a cluster. Sixty two clusters were assigned to a single neuron class and 15 clusters grouped neuron classes sharing close molecular signatures. Pseudotime analysis revealed a maturation process occurring in some neurons (e.g. PDA) during the L2 stage. Based on the molecular profiles of all identified neurons, we predicted cell fate regulators and experimentally validated unc-86 for the normal differentiation of RMG neurons. Furthermore, we observed that different classes of genes functionally diversify sensory neurons, interneurons and motorneurons. Finally, we designed 15 new neuron class-specific promoters validated in vivo. Amongst them, 10 represent the only specific promoter reported to this day, expanding the list of neurons amenable to genetic manipulations.

scholarly journals hecd-1 Modulates Notch Activity in Caenorhabditis elegans

2015 ◽  
Vol 5 (3) ◽  
pp. 353-359 ◽  
Author(s):  
Yunting Chen ◽  
Iva Greenwald
Keyword(s):  
Quality Control ◽  
Caenorhabditis Elegans ◽  
Cell Fate ◽  
Germ Line ◽  
Notch Pathway ◽  
Cell Fate Decisions ◽  
Notch Activity ◽  
C Elegans ◽  
Somatic Gonad ◽  
Constitutively Active

Abstract Notch is a receptor that mediates cell–cell interactions that specify binary cell fate decisions in development and tissue homeostasis. Inappropriate Notch signaling is associated with cancer, and mutations in Notch pathway components have been associated with developmental diseases and syndromes. In Caenorhabditis elegans, suppressors of phenotypes associated with constitutively active LIN-12/Notch have identified many conserved core components and direct or indirect modulators. Here, we molecularly identify sel(ar584), originally isolated as a suppressor of a constitutively active allele of lin-12. We show that sel(ar584) is an allele of hecd-1, the ortholog of human HECDT1, a ubiquitin ligase that has been implicated in several different mammalian developmental events. We studied interactions of hecd-1 with lin-12 in the somatic gonad and with the other C. elegans Notch gene, glp-1, in the germ line. We found that hecd-1 acts as a positive modulator of lin-12/Notch activity in a somatic gonad context—the original basis for its isolation—but acts autonomously as a negative modulator of glp-1/Notch activity in the germ line. As the yeast ortholog of HECD-1, Ufd4p, has been shown to function in quality control, and C. elegans  HECD-1 has been shown to affect mitochondrial maintenance, we propose that the different genetic interactions between hecd-1 and Notch genes we observed in different cell contexts may reflect differences in quality control regulatory mechanisms or in cellular metabolism.

scholarly journals mRNA localization is linked to translation regulation in the Caenorhabditis elegans germ lineage

2020 ◽  
Author(s):  
Dylan M. Parker ◽  
Lindsay P. Winkenbach ◽  
Samuel P. Boyson ◽  
Matthew N. Saxton ◽  
Camryn Daidone ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Regulatory Control ◽  
Translational Repression ◽  
Translation Regulation ◽  
Germline Development ◽  
P Granules ◽  
C Elegans ◽  
Early Embryos

AbstractCaenorhabditis elegans early embryos generate cell-specific transcriptomes despite lacking active transcription. This presents an opportunity to study mechanisms of post-transcriptional regulatory control. In seeking the mechanisms behind this patterning, we discovered that some cell-specific mRNAs accumulate non-homogenously within cells, localizing to membranes, P granules (associated with progenitor germ cells in the P lineage), and P-bodies (associated with RNA processing). Transcripts differed in their dependence on 3’UTRs and RNA Binding Proteins, suggesting diverse regulatory mechanisms. Notably, we found strong but imperfect correlations between low translational status and P granule localization within the progenitor germ lineage. By uncoupling these, we untangled a long-standing question: Are mRNAs directed to P granules for translational repression or do they accumulate there as a downstream step? We found translational repression preceded P granule localization and could occur independent of it. Further, disruption of translation was sufficient to send homogenously distributed mRNAs to P granules. Overall, we show transcripts important for germline development are directed to P granules by translational repression, and this, in turn, directs their accumulation in the progenitor germ lineage where their repression can ultimately be relieved.SummaryMaternally loaded mRNAs localize non-homogeneously within C. elegans early embryos correlating with their translational status and lineage-specific fates.

scholarly journals Biology of the Caenorhabditis elegans Germline Stem Cell System

Genetics ◽  
2019 ◽  
Vol 213 (4) ◽  
pp. 1145-1188 ◽  
Author(s):  
E. Jane Albert Hubbard ◽  
Tim Schedl
Keyword(s):  
Stem Cell ◽  
Caenorhabditis Elegans ◽  
Cell Fate ◽  
Control Cell ◽  
Cell System ◽  
Germline Stem Cell ◽  
Cell Systems ◽  
Stem Cell Fate ◽  
C Elegans ◽  
Stem Cell System

Stem cell systems regulate tissue development and maintenance. The germline stem cell system is essential for animal reproduction, controlling both the timing and number of progeny through its influence on gamete production. In this review, we first draw general comparisons to stem cell systems in other organisms, and then present our current understanding of the germline stem cell system in Caenorhabditis elegans. In contrast to stereotypic somatic development and cell number stasis of adult somatic cells in C. elegans, the germline stem cell system has a variable division pattern, and the system differs between larval development, early adult peak reproduction and age-related decline. We discuss the cell and developmental biology of the stem cell system and the Notch regulated genetic network that controls the key decision between the stem cell fate and meiotic development, as it occurs under optimal laboratory conditions in adult and larval stages. We then discuss alterations of the stem cell system in response to environmental perturbations and aging. A recurring distinction is between processes that control stem cell fate and those that control cell cycle regulation. C. elegans is a powerful model for understanding germline stem cells and stem cell biology.

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