AU-Rich Element-Mediated mRNA Decay Can Occur Independently of the miRNA Machinery in Mouse Embryonic Fibroblasts and Drosophila S2-Cells

AU-rich elements (AREs) are regulatory sequences located in the 3′ untranslated region of many short-lived mRNAs. AREs are recognized by ARE-binding proteins and cause rapid mRNA degradation. Recent reports claimed that the function of AREs may be – at least in part – relayed through the miRNA pathway. We have revisited this hypothesis using dicer knock-out mouse embryonic fibroblasts and cultured Drosophila cells. In contrast to the published results, we find no evidence for a general requirement of the miRNA pathway in the function of AREs. Endogenous ier3 mRNA, which is known to contain a functional ARE, was degraded rapidly at indistinguishable rates in wild type and dicer knock-out mouse embryonic fibroblasts. In cultured Drosophila cells, both ARE-containing GFP reporter mRNAs and the endogenous cecA1 mRNA were resistant to depletion of the mi/siRNA factors dcr-1, dcr-2, ago1 and ago2. Furthermore, the Drosophila miRNA originally proposed to recognize AU-rich elements, miR-289, is not detectably expressed in flies or cultured S2 cells. Even our attempts to overexpress this miRNA from its genomic hairpin sequence failed. Thus, this sequence cannot serve as link between the miRNA and the AU-rich element mediated silencing pathways. Taken together, our studies in mammalian and Drosophila cells strongly argue that AREs can function independently of miRNAs

Genome-Wide Assessment of AU-Rich Elements by the AREScore Algorithm

In mammalian cells, AU-rich elements (AREs) are well known regulatory sequences located in the 3′ untranslated region (UTR) of many short-lived mRNAs. AREs cause mRNAs to be degraded rapidly and thereby suppress gene expression at the posttranscriptional level. Based on the number of AUUUA pentamers, their proximity, and surrounding AU-rich regions, we generated an algorithm termed AREScore that identifies AREs and provides a numerical assessment of their strength. By analyzing the AREScore distribution in the transcriptomes of 14 metazoan species, we provide evidence that AREs were selected for in several vertebrates and Drosophila melanogaster. We then measured mRNA expression levels genome-wide to address the importance of AREs in SL2 cells derived from D. melanogaster hemocytes. Tis11, a zinc finger RNA–binding protein homologous to mammalian tristetraprolin, was found to target ARE–containing reporter mRNAs for rapid degradation in SL2 cells. Drosophila mRNAs whose expression is elevated upon knock down of Tis11 were found to have higher AREScores. Moreover high AREScores correlate with reduced mRNA expression levels on a genome-wide scale. The precise measurement of degradation rates for 26 Drosophila mRNAs revealed that the AREScore is a very good predictor of short-lived mRNAs. Taken together, this study introduces AREScore as a simple tool to identify ARE–containing mRNAs and provides compelling evidence that AREs are widespread regulatory elements in Drosophila

The Fatty Acid Profile Of Sparus Aurata Larvae Is Correlated To The Composition Of The Enrichment Diets Of Brachionus Plicatilis And Artemia sp

El objetivo del presente estudio fue determinar el efecto del enriquecimiento de rotíferos (Brachionus plicatilis) y camarones de salina (Artemia sp.) con diferentes emulsiones comerciales y microalgas sobre la composición de los ácidos grasos poliinsaturados (PUFA) de larvas de pargo dorado, Sparus aurata. Se alimentaron los rotíferos con cuatro dietas de enriquecimiento (Chlorella sp. marino y tres emulsiones comerciales: Algal RotíferoMR, FrippakMR Booster y SelcoMR). Se realizó el enriquecimiento de Artemiu sp. (Artemia SystemsMR, tipo AF) con nauplios instar I a una densidad de 250-300 nauplios/ml en estanques cónicos de 20 l, usando dos emulsiones comerciales (TrofficMR y SelcoMR) y una microalga (Chlorella sp.). A pesar de que el método de enriquecimiento parece ser eficiente para incorporar el tratamiento de ácidos grasos en las larvas, los resultados muestran que las presas enriquecidas tuvieron una deficiencia de PUPA n-3 y que posiblemente no aportan los requisitos alimenticios de las larvas de pargo dorado. The objective of the present work was to determine the effect of the enrichment of rotifers (Brachionus plicatilis) and brine shrimp (Artemia sp.) with different commercial emulsions and microalgae on polyunsaturated fatty acid (PUFA) composition of gilthead sea bream larvae. Sparus aurata. Rotifers were fed four enrichment diets (marine Chlorella sp., and three commercial emulsions: Algal RotíferoTM, FrippakrTM booster and SelcoTM). The enrichment of Artemia sp. (Artemia SystemsTM, AF type) was carried out with instar 1 nauplii at a density of 250-300 nauplii/ml in 20-l conical tanks, using two commercial emulsions (TrofficTM and SelcoTM) and a microalgae (Chlorelia sp.). The results showed that enriched preys were deficient in PUFA n-3 and may not provide the nutritional requirements of sea bream larvae, although the enrichment methodology seems to be efficient in order to incorporate in the larvae the fatty acid treatment

Anticonvulsant and GABA uptake inhibition properties of venom fractions from the spiders Parawixia bistriata and Scaptocosa raptoria

In this article we describe an in vivo anticonvulsant effect from denatured crude venom and partially isolated fractions from two spiders: Parawixia bistriata and Scaptocosa raptoria. Intracerebroventricular injections of these venoms and fractions abolished rat convulsive tonic-clonic seizures induced by picrotoxin, bicuculline and pentylenetetrazole, and also, inhibited GABA uptake in synaptosomes of rat cerebral cortex. the venoms described in this work seems to be promising tools for the study of the GABAergic system, and may be a potential source for new anticonvulsant drugs.Univ São Paulo, Lab Neurobiol & Peconhas, Dept Biol, Fac Filosofia,Ciencias & Letras Ribeirao Preto, BR-14049901 São Paulo, BrazilUniv São Paulo, Fac Med Ribeirao Preto, Lab Neuroquim, Dept Bioquim, BR-14049901 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biofis, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biofis, São Paulo, BrazilWeb of Scienc

Drosophila processing bodies in oogenesis

Processing bodies (P-bodies) have emerged as important subcellular structures that are involved in mRNA metabolism. To date, a detailed description of P-bodies in Drosophila oogenesis is lacking. To this end, we first demonstrate that Drosophila decapping protein 2 (dDcp2) contains intrinsic decapping activity and its enzymatic activity was not detectably enhanced by Drosophila decapping protein 1 (dDcp1). dDcp1-containing bodies in the nurse cell cytoplasm can associate with the 5' to 3' exoribonuclease, Pacman in addition to dDcp2 and Me31B. The size and number of dDcp1 bodies are dynamic and dramatically increased in dDcp2 and pacman mutant backgrounds supporting the conclusion that dDcp1 bodies in nurse cell cytoplasm are Drosophila P-bodies. In stage 2-6 oocytes, dDcp1 bodies appear to be distinct from previously characterized P-bodies since they are insensitive to cycloheximide and RNase A treatments. Curiously, dDcp2 and Pacman do not colocalize with dDcp1 at the posterior end of the oocyte in stage 9-10 oocytes. This suggests that dDcp1 bodies are in a developmentally distinct state separate from the 5' end mRNA degradation enzymes at later stages in the oocyte. Interestingly, re-formation of maternally expressed dDcp1 with dDcp2 and Pacman was observed in early embryogenesis. With respect to developmental switching, the maternal dDcp1 is proposed to serve as a marker for the re-formation of P-bodies in early embryos. This also suggests that a regulated conversion occurs between maternal RNA granules and P-bodies from oogenesis to embryogenesis

A Masked PY-NLS in Drosophila TIS11 and Its Mammalian Homolog Tristetraprolin.

Many RNA-binding proteins (RBPs) dynamically shuttle between the nucleus and the cytoplasm, often exerting different functions in each compartment. Therefore, the nucleo-cytoplasmic distribution of RBPs has a strong impact on their activity. Here we describe the localization and the shuttling properties of the tandem zinc finger RBP dTIS11, which is the Drosophila homolog of mammalian TIS11 proteins. Drosophila and mammalian TIS11 proteins act as destabilizing factors in ARE-mediated decay. At equilibrium, dTIS11 is concentrated mainly in the cytoplasm. We show that dTIS11 is a nucleo-cytoplasmic shuttling protein whose nuclear export is mediated by the exportin CRM1 through the recognition of a nuclear export signal (NES) located in a different region comparatively to its mammalian homologs. We also identify a cryptic Transportin-dependent PY nuclear localization signal (PY-NLS) in the tandem zinc finger region of dTIS11 and show that it is conserved across the TIS11 protein family. This NLS partially overlaps the second zinc finger ZnF2. Importantly, mutations disrupting the capacity of the ZnF2 to coordinate a Zinc ion unmask dTIS11 and TTP NLS and promote nuclear import. All together, our results indicate that the nuclear export of TIS11 proteins is mediated by CRM1 through diverging NESs, while their nuclear import mechanism may rely on a highly conserved PY-NLS whose activity is negatively regulated by ZnF2 folding.Journal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe