CncRNAs : RNAs with both coding and non-coding roles in development

RNAs are known to regulate diverse biological processes, either as protein-encoding molecules or as non-coding RNAs. However, a third class that comprises RNAs endowed with both protein coding and non-coding functions has recently emerged. Such bi-functional ‘coding and non-coding RNAs’ (cncRNAs) have been shown to play important roles in distinct developmental processes in plants and animals. Here, we discuss key examples of cncRNAs and review their roles, regulation and mechanisms of action during development

Drosophila Ge-1 Promotes P Body Formation and oskar mRNA Localization

mRNA localization coupled with translational control is a widespread and conserved strategy that allows the localized production of proteins within eukaryotic cells. In Drosophila, oskar (osk) mRNA localization and translation at the posterior pole of the oocyte are essential for proper patterning of the embryo. Several P body components are involved in osk mRNA localization and translational repression, suggesting a link between P bodies and osk RNPs. In cultured mammalian cells, Ge-1 protein is required for P body formation. Combining genetic, biochemical and immunohistochemical approaches, we show that, in vivo, Drosophila Ge-1 (dGe-1) is an essential gene encoding a P body component that promotes formation of these structures in the germline. dGe-1 partially colocalizes with osk mRNA and is required for osk RNP integrity. Our analysis reveals that although under normal conditions dGe-1 function is not essential for osk mRNA localization, it becomes critical when other components of the localization machinery, such as staufen, Drosophila decapping protein 1 and barentsz are limiting. Our findings suggest an important role of dGe-1 in optimization of the osk mRNA localization process required for patterning the Drosophila embryo

The Ig cell adhesion molecule Basigin controls compartmentalization and vesicle release at Drosophila melanogaster synapses

Synapses can undergo rapid changes in size as well as in their vesicle release function during both plasticity processes and development. This fundamental property of neuronal cells requires the coordinated rearrangement of synaptic membranes and their associated cytoskeleton, yet remarkably little is known of how this coupling is achieved. In a GFP exon-trap screen, we identified Drosophila melanogaster Basigin (Bsg) as an immunoglobulin domain-containing transmembrane protein accumulating at periactive zones of neuromuscular junctions. Bsg is required pre- and postsynaptically to restrict synaptic bouton size, its juxtamembrane cytoplasmic residues being important for that function. Bsg controls different aspects of synaptic structure, including distribution of synaptic vesicles and organization of the presynaptic cortical actin cytoskeleton. Strikingly, bsg function is also required specifically within the presynaptic terminal to inhibit nonsynchronized evoked vesicle release. We thus propose that Bsg is part of a transsynaptic complex regulating synaptic compartmentalization and strength, and coordinating plasma membrane and cortical organization

Considerations when investigating lncRNA function in vivo

Although a small number of the vast array of animal long non-coding RNAs (lncRNAs) have known effects on cellular processes examined in vitro, the extent of their contributions to normal cell processes throughout development, differentiation and disease for the most part remains less clear. Phenotypes arising from deletion of an entire genomic locus cannot be unequivocally attributed either to the loss of the lncRNA per se or to the associated loss of other overlapping DNA regulatory elements. The distinction between cis- or trans-effects is also often problematic. We discuss the advantages and challenges associated with the current techniques for studying the in vivo function of lncRNAs in the light of different models of lncRNA molecular mechanism, and reflect on the design of experiments to mutate lncRNA loci. These considerations should assist in the further investigation of these transcriptional products of the genome

Gain-of-function screen for genes that affect Drosophila muscle pattern formation.

This article reports the production of an EP-element insertion library with more than 3,700 unique target sites within the Drosophila melanogaster genome and its use to systematically identify genes that affect embryonic muscle pattern formation. We designed a UAS/GAL4 system to drive GAL4-responsive expression of the EP-targeted genes in developing apodeme cells to which migrating myotubes finally attach and in an intrasegmental pattern of cells that serve myotubes as a migration substrate on their way towards the apodemes. The results suggest that misexpression of more than 1.5% of the Drosophila genes can interfere with proper myotube guidance and/or muscle attachment. In addition to factors already known to participate in these processes, we identified a number of enzymes that participate in the synthesis or modification of protein carbohydrate side chains and in Ubiquitin modifications and/or the Ubiquitin-dependent degradation of proteins, suggesting that these processes are relevant for muscle pattern formation

Role of the Single-Stranded DNA–Binding Protein SsbB in Pneumococcal Transformation: Maintenance of a Reservoir for Genetic Plasticity

Bacteria encode a single-stranded DNA (ssDNA) binding protein (SSB) crucial for genome maintenance. In Bacillus subtilis and Streptococcus pneumoniae, an alternative SSB, SsbB, is expressed uniquely during competence for genetic transformation, but its precise role has been disappointingly obscure. Here, we report our investigations involving comparison of a null mutant (ssbB−) and a C-ter truncation (ssbBΔ7) of SsbB of S. pneumoniae, the latter constructed because SSBs' acidic tail has emerged as a key site for interactions with partner proteins. We provide evidence that SsbB directly protects internalized ssDNA. We show that SsbB is highly abundant, potentially allowing the binding of ∼1.15 Mb ssDNA (half a genome equivalent); that it participates in the processing of ssDNA into recombinants; and that, at high DNA concentration, it is of crucial importance for chromosomal transformation whilst antagonizing plasmid transformation. While the latter observation explains a long-standing observation that plasmid transformation is very inefficient in S. pneumoniae (compared to chromosomal transformation), the former supports our previous suggestion that SsbB creates a reservoir of ssDNA, allowing successive recombination cycles. SsbBΔ7 fulfils the reservoir function, suggesting that SsbB C-ter is not necessary for processing protein(s) to access stored ssDNA. We propose that the evolutionary raison d'être of SsbB and its abundance is maintenance of this reservoir, which contributes to the genetic plasticity of S. pneumoniae by increasing the likelihood of multiple transformation events in the same cell

L'épissage de l'ARN oskar est couplé à sa localisation cytoplasmique

La localisation intracellulaire d'un ARN messager constitue un moyen très efficace de restreindre une activité protéique en un site cellulaire précis. Dans l'ovocyte de Drosophila melanogaster, l'ARNm oskar localise au pôle postérieur et induit la formation du plasme germinal et des structures postérieures de l'embryon. Son transport est réalisé par l'intermédiaire de facteurs en trans, comme Mago nashi, qui forment avec l'ARNm oskar un complexe de localisation ribonucléoprotéique.Nous montrons que la protéine Drosophila Y14 s'associe avec Mago nashi et est essentielle à la localisation de l'ARNm oskar. Chez les vertébrés, les homologues respectifs de Drosophila Y14 et Mago nashi, Y14 et Magoh, appartiennent au complexe de jonction exon-exon (EJC). Ce complexe, recruté par le processus d'excision-épissage, s'assemble 20 à 24 nucléotides en amont des jonctions exon-exon des ARNm, indépendamment de leur séquence.Nous démontrons que l'excision-épissage de l'ARN oskar est couplé à sa localisation cytoplasmique. De plus, nous montrons que la position d'excision-épissage relative à l'ARN oskar est cruciale pour sa localisation cytoplasmique, indiquant que la position de l'EJC est critique pour la formation du complexe de localisation de l'ARNm oskar.Ces résultats mettent en évidence l'existence d'un mécanisme de couplage entre le processus nucléaire d'excision-épissage et la localisation cytoplasmique de l'ARNm oskar. Cette étude révèle une nouvelle fonction de l'excision-épissage : la régulation de la localisation cytoplasmique d'ARNm par l'organisation de complexes ribonucléoprotéiques.Cytoplasmic messenger RNA localization is a powerful strategy for restricting protein activity in a precise cellular location. In the Drosophila melanogaster oocyte, oskar mRNA localizes at the posterior pole to specify the germline and pattern the abdomen of the future embryo. Its transport to the oocyte posterior is mediated by trans factors, such as Mago nashi, that form together with oskar mRNA a ribonucleoproteic localization complex.We show that Drosophila Y14 interacts with Mago nashi and is essential for oskar mRNA localization. In vertebrates, the homologues of Drosophila Y14 and Mago nashi, Y14 and Magoh, are core components of the exon-exon junction complex. This complex is recruited in a splicing-dependent manner and associates with mRNAs 20 to 24 nucleotides upstream of exon-exon junctions, independent of the RNA sequence.We demonstrate that splicing of oskar RNA is coupled to its cytoplasmic localization. Interestingly, we show that the position of splicing on oskar mRNA is crucial for its cytoplasmic localization, thereby indicating that the position of the EJC is critical for the formation of the oskar mRNA localization complex.These results demonstrate a mechanistic coupling between the nuclear process of splicing and the cytoplasmic localization of oskar mRNA. It reveals an important new function for splicing: regulation of messenger ribonucleoprotein complex assembly and organization for mRNA cytoplasmic localization.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Vesicular traffic in axis specification during Drosophila melanogaster oogenisis (a study of rab6 gene function in organization of the egg-chamber and in oskar mRNA localization)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

An Intracellular Transmission Control Protocol: assembly and transport of ribonucleoprotein complexes

International audienc