748 research outputs found
Modulating role of RNA structure in alternative splicing of a critical exon in the spinal muscular atrophy genes
Humans have two nearly identical copies of the survival motor neuron (SMN ) gene, SMN1 and SMN2. Homozygous loss of SMN1 causes spinal muscular atrophy (SMA). SMN2 is unable to prevent the disease due to skipping of exon 7. Using a systematic approach of in vivo selection, we have previously demonstrated that a weak 5′ splice site (ss) serves as the major cause of skipping of SMN2 exon 7. Here we show the inhibitory impact of RNA structure on the weak 5′ ss of exon 7. We call this structure terminal stem–loop 2 (TSL2). Confirming the inhibitory nature of TSL2, point mutations that destabilize TSL2 promote exon 7 inclusion in SMN2, whereas strengthening of TSL2 promotes exon 7 skipping even in SMN1. We also demonstrate that TSL2 negatively affects the recruitment of U1snRNP at the 5′ ss of exon 7. Using enzymatic structure probing, we confirm that the sequence at the junction of exon 7/intron 7 folds into TSL2 and show that mutations in TSL2 cause predicted structural changes in this region. Our findings reveal for the first time the critical role of RNA structure in regulation of alternative splicing of human SMN
Filamentous Soil Fungi from Ny-Ă…lesund, Spitsbergen, and Screening for Extracellular Enzymes
Soil filamentous fungi from Ny-Ă…lesund, Spitsbergen, were studied. A total of 30 fungal isolates were identified by morpho-taxonomy, and the identity of some morpho-taxonomically complex isolates was authenticated by ITS1-5.8S and ITS2 rDNA domain sequence similarity. The isolates belonged to 19 species under 14 genera (Acremonium, Arthrinium, Aspergillus, Cladosporium, Corynespora, Emericella, Geomyces, Mortierella, Mucor, Myrothecium, Penicillium, Phialophora, Preussia, Xylaria). To the best of our knowledge, Acremonium roseolum, Aspergillus aculeatus, Emericella nidulans, and Preussia sp. are the first northernmost records from Arctic soils. The viable fungal count in different soil samples varied from 0.5 • 104 to 2.0 • 105 g-1. Species richness in different soil samples was also calculated. Mortierella was one of the most dominant genera in Arctic soils. A temperature tolerance study was carried out for all the isolates, and representative species were screened for their extracellular enzyme activity (amylase, cellulase, phosphatase, and pectinase) at 4ËšC and 20ËšC. Among the 30 isolates, seven showed cellulolytic activity, two were phosphate solubilizers, three had amylolytic activity, and only one showed pectinolytic activity on solid media. CMCase (β1, 4-endoglucanase) activity was quantified in seven isolates that exhibited positive activity during preliminary screening. The records of enzyme activity for amylases, pectinases, and cellulases are the first from the fungi of Spitsbergen. The present study indicates the dominance in Ny-Ă…lesund of cellulolytic strains, which may serve as potent decomposers in Arctic tundra. These isolates may be used to facilitate the mineralization of cellulolytic wastes generated by human activities in colder hilly areas across the world, including the Himalayas in India.Nous avons Ă©tudiĂ© des champignons telluriques filamenteux de Ny-Ă…lesund, Spitzberg. Grâce Ă la morpho-taxonomie, nous avons identifiĂ© 30 isolats fongiques, et l’identitĂ© de certains complexes d’isolats morpho-taxonomiques a Ă©tĂ© authentifiĂ©e au moyen des similaritĂ©s des sĂ©quences de domaines ITS1-5.8S et ITS2 DNAr. Les isolats relevaient de 19 espèces faisant partie de 14 genres (Acremonium, Arthrinium, Aspergillus, Cladosporium, Corynespora, Emericella, Geomyces, Mortierella, Mucor, Myrothecium, Penicillium, Phialophora, Preussia, Xylaria). Au meilleur de nos connaisÂsances, Acremonium roseolum, Aspergillus aculeatus, Emericella nidulans et Preussia sp. constituent les premiers enregisÂtrements aussi nordiques des sols arctiques. Le dĂ©nombrement viable de champignons dans diffĂ©rents Ă©chantillons de sol variait de 0,5 • 104 Ă 2,0 • 105 g-1. Nous avons Ă©galement calculĂ© la diversitĂ© des espèces prĂ©levĂ©es dans diffĂ©rents Ă©chantillons de sol. Le genre Mortierella Ă©tait l’un des plus dominants des sols arctiques. Nous avons Ă©tudiĂ© la tolĂ©rance Ă la tempĂ©rature de tous les isolats, et des espèces reprĂ©sentatives ont Ă©tĂ© examinĂ©es du point de vue de l’activitĂ© enzymatique extracellulaire (amylase, cellulase, phosphatase et pectinase) Ă 4 ËšC et 20 ËšC. Parmi les 30 isolats, sept prĂ©sentaient de l’activitĂ© cellulolytique, deux Ă©taient des solubilisants du phosphate, trois prĂ©sentaient de l’activitĂ© amylolytique et seulement un prĂ©sentait de l’activitĂ© pectolytique dans le cas des solides. L’activitĂ© CMCase (β1, 4-endoglucanase) a Ă©tĂ© quantifiĂ©e dans sept isolats qui affichaient une activitĂ© positive au cours de l’examen prĂ©liminaire. Il s’agissait de la première fois que de l’activitĂ© enzymatique pour les amylases, pectinases et cellulases a Ă©tĂ© dĂ©tectĂ©e dans les champignons de Spitzberg. Cette Ă©tude indique la dominance de souches cellulolytiques Ă Ny-Ă…lesund, souches qui peuvent servir de dĂ©composeurs puissants dans la toundra arctique. Ces isolats peuvent servir Ă faciliter la minĂ©ralisation des dĂ©chets cellulolytiques Ă©manant des activitĂ©s humaines dans les rĂ©gions montagneuses plus froides du monde entier, y compris l’Himalaya, en Inde
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