Polypyrimidine Tract Binding Protein Prevents Activity of an Intronic Regulatory Element That Promotes Usage of a Composite 3��-Terminal Exon

Alternative splicing of 3′-terminal exons plays a critical role in gene expression by producing mRNA with distinct 3′-untranslated regions that regulate their fate and their expression. The Xenopus α-tropomyosin pre-mRNA possesses a composite internal/3′-terminal exon (exon 9A9′) that is differentially processed depending on the embryonic tissue. Exon 9A9′ is repressed in non-muscle tissue by the polypyrimidine tract binding protein, whereas it is selected as a 3′-terminal or internal exon in myotomal cells and adult striated muscles, respectively. We report here the identification of an intronic regulatory element, designated the upstream terminal exon enhancer (UTE), that is required for the specific usage of exon 9A9′ as a 3′-terminal exon in the myotome. We demonstrate that polypyrimidine tract binding protein prevents the activity of UTE in non-muscle cells, whereas a subclass of serine/arginine rich (SR) proteins promotes the selection of exon 9A9′ in a UTE-dependent way. Morpholino-targeted blocking of UTE in the embryo strongly reduced the inclusion of exon 9A9′ as a 3′-terminal exon in the endogenous mRNA, demonstrating the function of UTE under physiological circumstances. This strategy allowed us to reveal a splicing pathway that generates a mRNA with no in frame stop codon and whose steady-state level is translation-dependent. This result suggests that a non-stop decay mechanism participates in the strict control of the 3′-end processing of the α-tropomyosin pre-mRNA.     

The CR3 motif of Rrp44p is important for interaction with the core exosome and exosome function

The 10-subunit RNA exosome is involved in a large number of diverse RNA processing and degradation events in eukaryotes. These reactions are carried out by the single catalytic subunit, Rrp44p/Dis3p, which is composed of three parts that are conserved throughout eukaryotes. The exosome is named for the 3′ to 5′ exoribonuclease activity provided by a large C-terminal region of the Rrp44p subunit that resembles other exoribonucleases. Rrp44p also contains an endoribonuclease domain. Finally, the very N-terminus of Rrp44p contains three Cys residues (CR3 motif) that are conserved in many eukaryotes but have no known function. These three conserved Cys residues cluster with a previously unrecognized conserved His residue in what resembles a metal-ion-binding site. Genetic and biochemical data show that this CR3 motif affects both endo- and exonuclease activity in vivo and both the nuclear and cytoplasmic exosome, as well as the ability of Rrp44p to associate with the other exosome subunits. These data provide the first direct evidence that the exosome-Rrp44p interaction is functionally important and also provides a molecular explanation for the functional defects when the conserved Cys residues are mutated.     

Quantitative trait loci for foliar terpenes in a global eucalypt species

Terpenes are a diverse group of plant secondary metabolites that mediate a plethora of ecological interactions in many plant species. Despite increasing research into the genetic control of important adaptive traits in some plant species, the genetic control of terpenes in forest tree species is still relatively poorly studied. In this study, we use quantitative genetic and quantitative trait loci (QTL) analysis to investigate the genetic control of foliar terpenes in an ecologically and commercially important eucalypt species, Eucalyptus globulus. We show a moderate to high within-family broad-sense heritability and significant genetic basis to the variation in 14 of the 16 terpenes assayed. This is the first report of QTL for terpenes in this species. Eleven QTL influenced the terpenes overall. One QTL on linkage group 6 affected six of the seven different sesquiterpenes assayed (plus one monoterpene), which, in combination with highly significant correlations between these compounds, argues that their variation is influenced by a QTL with pleiotropic effect early in the biosynthetic pathway. We examine the homology of these QTL to those found in a closely related eucalypt, Eucalyptus nitens, and provide evidence that both common and unique QTL influence terpene levels.     

Environmental factors associated with fish distribution in an urban neotropical river (Upper Tiet�� River Basin, S?o Paulo, Brazil)

The rivers and streams of the large urban centers in Southeast Brazil are increasingly being degraded, demanding expanded conservation efforts. This study was conducted in the Grande River, one of the main tributaries of the Billings Complex, a reservoir that is a strategic fresh water resource for the S?o Paulo metropolitan region. Water quality, habitat features and fish fauna were investigated at seven sites along the longitudinal gradient with the aim of identifying the distribution patterns and relative contributions of the environmental factors. The water samples and environmental characteristics were recorded, and fish were collected during the rainy (January to March) and dry seasons (July and August) of 2009. The water quality varied along the river, with higher values of conductivity, fecal coliforms and total phosphorus in the lower reach, indicating a strong influence of the urban area. Twenty-two fish species were recorded, two of which are considered endangered. A canonical correspondence analysis (CCA) indicated marked differences in species composition between the river??s upper and lower reaches, which was mainly attributed to vegetation cover and the presence of different meso-habitats, such as riffles and pools. Trychomycterus spp. and Astyanax paranae were associated with the upper reaches, while Astyanax fasciatus and Astyanax bockmanni, Cyphocharax modestus, Hoplias malabaricus and Hypostomus ancistroides occurred in the lower reaches. Despite the disturbance in water quality and riparian vegetation in the lower river section, no detectable changes in community structure were observed. However, the presence of some tolerant species, such as Astyanax fasciatus, Hoplosternum littorale and Hypostomus ancistroides, may indicate that the community is experiencing initial stages of disturbance.     

Physicochemical properties and antiproliferative activity of recombinant Yersinia pseudotuberculosis L-asparaginase

The physicochemical, catalytic, and antiproliferative activity of a recombinant L-asparaginase from Yersinia pseudotuberculosis (YpA) have been studied. The following results were obtained: the K _M value for L-asparagine is 17 ± 0.9 ??M, the optimal temperature is 60°C, pH is 8.0, pI is 5.4 ± 0.3, the L-glutaminase activity is no more than 5?C6% of the L-asparaginase activity, and the antiproliferative activity on the Fisher L5178y lymphadenosis cell line comprised T/C = 136% (p < 0.001) at a 15% recovery rate. The described characteristic allows one to regard YpA as an antitumor enzyme with biological features similar to the L-asparaginase of E. coli.     

Involvement of virulence properties and antibiotic resistance in Escherichia coli strains causing pyelonephritis in children

A total of 145 Escherichia coli strains causing pyelonephritis in children were investigated for the prevalence of genes encoding the following virulence factors (VFs): P fimbria (67.6?%), S fimbria (53.8?%), AFA adhesins (2.8?%), cytotoxic necrotizing factor 1 (37.9?%), ??-hemolysin (41.4?%), and aerobactin (71.7?%). One hundred and thirty-six (93.8?%) isolates harbored at least one of the virulence genes detected in the present study. Statistically significant co-occurrent presence of two VF genes was found for ??-hly?Ccnf1, ??-hly?Csfa, cnf1?Csfa (p?<?0.001), and ??-hly?Cpap (p?=?0.001). Twenty-six profiles of VF genes were detected in this study. The combinations of aer?Cpap and aer?Cpap?Csfa?C??-hly?Ccnf1 were presented with the highest frequency??both of them in 28 isolates (19.3?%). All E. coli strains included in the study were susceptible to meropenem, amikacin, and tobramycin; the highest frequency resistance was found toward ampicillin (43.4?%), piperacillin (31.7?%), tetracycline (15.9?%), and trimethoprim/sulfamethoxazole (11.7?%). The resistance to the other tested antimicrobial drugs did not exceed 3?% incidence. Overall, 55.9?% strains were susceptible to all tested anti-infective agents. Antimicrobial resistance of E. coli strains toward trimethoprim/sulfamethoxazole statistically significantly correlated with the presence of ??-hly (p?<?0.001), sfa (p?<?0.01), and cnf1 (p?<?0.05).