The Presence in tRNA Molecule Sequences of the Double Hairpin,an Evolutionary Stage Through Which the Origin of this Molecule is Thought to have Passed

We analyse 6,810 tRNAs, calculating the free energy of the corresponding double hairpin and ‘cigar’ secondary structures, for which we find a high thermodynamic and statistical significance. We also analyse these tRNAs for similarity and complementarity of their 5′ and 3′ halves or segments of them in intra-and inter-molecular comparisons. We find very clear signs that the two halves of tRNAs had an evident evolutionary relationship, although it is not totally clear whether this was a relationship of homology or complementarity between the 5′ and 3′ halves of tRNAs, even if there is strong evidence in favour of the homology hypothesis. Overall, these data favour models for the origin of the tRNA molecule postulating that a duplication event involving a hairpin structure as a precursor was involved in the origin of this molecule. Moreover, we interpret these results and favour the hypothesis that sees the assembly of two hairpin structures sharing a homology relationship as the intermediate evolutionary stage preceding the appearance of the cloverleaf structure of tRNA.     

Characterization of a novel biosurfactant producing Pseudomonas koreensis lineage that is endemic to Cuatro Ciénegas Basin

The aim of this work is the taxonomic characterization of three biosurfactant-producing bacterial isolates from the Churince system at Cuatro Ciénegas Basin (CCB) in the Mexican State of Coahuila, and the study of the possible role of biosurfactant production in their ecology and evolution. We determined that these isolates belong to a Pseudomonas koreensis lineage endemic to CCB, using standard taxonomical techniques, phylogenetic analysis of three chromosomal loci and phenotypic characterization. This new lineage has the distinct capacity to produce a biosurfactant when compared with previously reported P. koreensis isolates recovered from agricultural soils in Korea. We present evidence suggesting that the biosurfactant secreted by CCB P. koreensis strains is involved in their ability to compete with a CCB Exiguobacterium aurantiacum strain (m5-66) used as a model organism in competition experiments. Furthermore, the ethyl acetate extract of culture supernatant of CCB P. koreensis strains results in growth inhibition not only of E. aurantiacum m5-66, but also of a Bacillus subtilis type strain (ATCC6633). Based on these results we propose that the production of biosurfactant could be of ecological importance and could play a role in the separation of the P. koreensis CCB lineage.     

Immunogenicity of nuclear-encoded LTB:ST fusion protein from Escherichia coli expressed in tobacco plants

Enterotoxigenic Escherichia coli (ETEC) is one of the main causative agents of diarrhea in infants and for travelers. Inclusion of a heat-stable (ST) toxin into vaccine formulations is mandatory as most ETEC strains can produce both heat-labile (LT) and ST enterotoxins. In this study, a genetic fusion gene encoding for an LTB:ST protein has been constructed and transferred into tobacco via Agrobacterium tumefaciens-mediated transformation. Transgenic tobacco plants carrying the LTB:ST gene are then subjected to GM1-ELISA revealing that the LTB:ST has assembled into pentamers and displays antigenic determinants from both LTB and ST. Protein accumulation of up to 0.05% total soluble protein is detected. Subsequently, mucosal and systemic humoral responses are elicited in mice orally dosed with transgenic tobacco leaves. This has suggested that the plant-derived LTB:ST is immunogenic via the oral route. These findings are critical for the development of a plant-based vaccine capable of eliciting broader protection against ETEC and targeting both LTB and ST. Features of this platform in comparison to transplastomic approaches are discussed.     

Ganglioside GM1 mimics: lipophilic substituents improve affinity for cholera toxin

Ganglioside GM1 mimics including (R)-2-hydroxy-3-cyclohexylpropionic acid or (R)-2-hydroxy-3-phenylpropionic acid as replacements for NeuAc are stronger cholera toxin binders than the parent ligand 2, which includes (R)-2-hydroxy-propionic acid.     

The recycling of apolipoprotein E and its amino-terminal 22 kDa fragment: evidence for multiple redundant pathways

A portion of apolipoprotein E (apoE) internalized by hepatocytes is spared degradation and is recycled. To investigate the intracellular routing of recycling apoE, primary hepatocyte cultures from LDL receptor-deficient mice and mice deficient in receptor-associated protein [a model of depressed expression of LDL receptor-related protein (LRP)] were incubated with human VLDL containing 125I-labeled human recombinant apoE3. Approximately 30% of the internalized intact apoE was recycled after 4 h. The N-terminal 22 kDa fragment of apoE was also resecreted, demonstrating that this apoE domain contains sufficient sequence to recycle. The 22 kDa fragment has reduced affinity for lipoproteins, suggesting that apoE recycling is linked to the ability of apoE to bind directly to a recycling receptor. Finally, apoE was found to recycle equally well in the presence of brefeldin A, a drug that blocks transport from the endoplasmic reticulum and leads to collapse of the Golgi stacks. Our studies demonstrate that apoE recycling occurs 1) in the absence of the LDL receptor or under conditions of markedly reduced LRP expression; 2) when apoE lacks the carboxyl-terminal domain, which allows binding to the lipoprotein; and 3) in the absence of an intact Golgi apparatus. We conclude that apoE recycling occurs through multiple redundant pathways.     

Acute outbreak of gnathostomiasis in a fishing community in Sinaloa, Mexico

An increasing number of human cases of gnathostomiasis have been reported in Sinaloa, Mexico, most of whom have a custom of eating of raw fish dishes such as 'cebiche'. Here we report five adult patients, three women and two men, having an acute episode of vomiting and abdominal pain a few minutes after eating a dish of cebiche prepared from a spotted sleeper perch (Eleotris picta) fished from a nearby lake in southern Sinaloa. All five patients experienced acute throat pain, chest and joint pains, headache and fever. One patient, a 55-year-old male, was hospitalized with suspected pancreatitis and pneumonia. By 8-9 days later, all five patients developed between three and 12 edematous, migrating skin lesions on the back, abdomen, upper and lower extremities, face, eye and scalp. By ELISA, all of them were sero-positive to Gnathostoma doloresi antigen and had elevated IgE levels. Eosinophilia was found in two patients. These patients lived in an agricultural and fishing community. In this community we carried out a sero-epidemiological survey and study of living conditions in a random sample of 309 individuals distributed in 74 households. Frequent consumption of raw fish was reported in 36% of households, and 12 individuals had a clinical history of migrating skin lesions. The sero-prevalence to Gnathostoma antigens was 34.95%. Five fish species and four species of ichthyophagous birds collected from three lakes in the village and a nearby estuary were infected with the advanced third-stage larvae of G. binucleatum, a species found in Ecuador and Mexico. The results describe the first known outbreak of acute gnathostomiasis on the American continent.     

Regulated mRNA stability of the Cdk inhibitor Rum1 links nutrient status to cell cycle progression

BACKGROUND: The survival of a cell depends on continuous sensing of the nutritional environment and appropriate coordination of the cell cycle. The fission yeast Schizosaccharomyces pombe is an excellent model system in which to study these processes. In the presence of nutrients, fission yeast cells grow and divide, spending most of their time in G2; when nutrients are limiting, they are promoted into mitosis and arrest the cell cycle in G1. The molecular mechanisms underlying this response are currently unknown.RESULTS: Here, we show that expression of the fission yeast Cdk inhibitor Rum1, a key regulator of Cdc2/cyclin B in G1, is subject to regulated mRNA stability in response to nutrient deprivation. In complete minimal medium, rum1 mRNAs are very unstable. Following nitrogen starvation, rum1 mRNAs are rapidly stabilized, allowing the accumulation of Rum1 protein to delay the G1 phase of the subsequent cell cycle. Instability of rum1 mRNAs in complete minimal medium depends on the presence of AU-rich elements in the 3'UTR. We also show that lack of this mechanism has consequences in the mitotic cell cycle, in meiosis, and in the control of ploidy.CONCLUSION: We propose that mRNA stability is an important mechanism to fine tune the expression of the rum1 gene, in order to allow the production of appropriate levels of Rum1 protein in response to changes in the nutritional environment.     

LIG4 and RAD52 DNA repair genes polymorphisms and systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder with a strong genetic background. Nevertheless, SLE might also be triggered due to environmental factors, such as UV light exposure. DNA double strand breaks (DSBs) may be induced secondarily by UV radiation, increasing DNA immunogenicity and in SLE patients DNA repair is diminished, allowing the accumulation of DSBs and genomic instability. LIG4 and RAD52 genes play important roles in DNA repair mechanisms and a recent microarray analysis showed their differential expression in active SLE patients. In this study we investigated a potential association between LIG4 and RAD52 single nucleotide polymorphisms (SNPs) and SLE predisposition in a Southeast Brazilian population. We assessed four Tag SNPs in LIG4 and three in RAD52 gene region, encompassing most of the gene sequence, in 158 SLE patients and 212 healthy controls. We also performed SNPs analysis considering clinical manifestation, gender and ethnicity in SLE patients. Our data did not show association between LIG4 and RAD52 SNPs and SLE, its clinical manifestations or ethnicity in the tested population. The analysis regarding ethnicity and SLE clinical manifestations indicated Caucasian-derived patients as more susceptible to cutaneous and hematological alterations than the African-derived. To our knowledge, this is the first association study involving LIG4 and RAD52 genes and SLE predisposition.