A new type of IRES within gag coding region recruits three initiation complexes on HIV-2 genomic RNA

Genomic RNA of primate lentiviruses serves both as an mRNA that encodes Gag and Gag-Pol polyproteins and as a propagated genome. Translation of this RNA is initiated by standard cap dependant mechanism or by internal entry of the ribosome. Two regions of the genomic RNA are able to attract initiation complexes, the 5′ untranslated region and the gag coding region itself. Relying on probing data and a phylogenetic study, we have modelled the secondary structure of HIV-1, HIV-2 and SIV_Mac coding region. This approach brings to light conserved secondary-structure elements that were shown by mutations to be required for internal entry of the ribosome. No structural homologies with other described viral or cellular IRES can be identified and lentiviral IRESes show many peculiar properties. Most notably, the IRES present in HIV-2 gag coding region is endowed with the unique ability to recruit up to three initiation complexes on a single RNA molecule. The structural and functional properties of gag coding sequence define a new type of IRES. Although its precise role is unknown, the conservation of the IRES among fast evolving lentiviruses suggests an important physiological role.     

In situ mapping of nitrifiers and anammox bacteria in microbial aggregates by means of confocal resonance Raman microscopy

In the present work the exploration of microbial communities by confocal resonance Raman microscopy (CRRM) is reported. Using the resonance Raman effect of cytochrome c (Cyt c) we were able to record the microbial distribution of nitrifiers and anammox bacteria directly in their natural environment without the need of sample preparation. For this new non-invasive investigation a reference database of bacteria assumed to be found in microbial aggregates obtained from biological wastewater treatment was created. Reference spectra of enriched cultures of the interesting bacteria were taken by means of optical tweezers. Significant spectra were achieved in less than 1 s (excitation wavelength 532 nm, laser power 9 mW) due to the resonance Raman effect. In addition, the impact of different parameters on the reference spectra, such as integration time and culture conditions, was analysed. We successfully demonstrate the grouping of bacteria down to strain level based on the heterogeneity of the resonance Raman spectra of the heme protein Cyt c.     

FT-IR and 1H NMR spectroscopic evidence of sugar ring conformational change in NH4GpG on complexation to form cis-[Pt(NH3)2(GpG)]+

The conformational change of the ribose ring in NH₄GpG and cis-[Pt(NH₃)₂(GpG)]⁺ was confirmed by FT-IR spectroscopic evidence as being C2′-endo, C3′-endo, anti, gg sugar ring pucker in the solid state. These results were compared with ¹H NMR spectral data in aqueous solution. The FT-IR spectrum of NH₄GpG shows marker bands at 802 cm^?1 and 797 cm^?1 which are assigned to the C3′-endo, anti, gg sugar-phosphate vibrations of ribose (?pG) and ribose (Gp?), respectively. The FT-IR spectrum of cis-[Pt(NH₃)₂(GpG)]⁺ (with N7N7 chelation in the GpG sequence) shows a marker band at 800 cm^?1 which is assigned to the C3′-endo, and a new shoulder band at 820 cm^?1 related to a C2′-endo ring pucker. The ribose conformation of (?pG) moiety in NH₄-GpG, C3′-endo, anti, gg changes into C2′-endo, anti, gg when a platinum atom is chelated to N7N7 in the GpG sequence.     

Uses, management, and economic potential ofDacryodes edulis (Burseraceae) in the Humid Lowlands of Cameroon

Dacryodes edulis is one of the most preferred tree species by farmers in the humid lowlands of Cameroon. The fruit of the species figures prominently in cross-boundary trade between Cameroon, Nigeria and Gabon. Although there exist empirical data on the volume of trade of the fruit at this level, no data are available at the farm level. A field survey was undertaken to identify uses, management, and farmers’ improvement objectives and to quantify, at the farm-level, the economic potential of the species. The results of the survey indicate thatD. edulis is widely planted and found mainly in tree crop fields and in home gardens. The fruit is highly consumed and traded. The farm-level value of fruit production reaches $US161 a year per grower or collector. The dead branches of the species are used as firewood and its bark is used as medicine. Desired improvement objectives include increased fruit size, good tasting fruit, high yield and reduced time to bearing.     

New alkamide and ent-kaurane diterpenoid derivatives from Senecio erechtitoides (Asteraceae)

Fractionation of a MeOH/CH₂Cl₂ (1/1) extract of the aerial parts of Senecio erechtitoides led to the isolation of six compounds including the hitherto unknown N-phenethylamide derivative named N-(p-hydroxyphenethyl)pentacosanamide (1), and a kauranoid derivative named derivative named ent-7-oxo-16α,17-dihydroxykauran-19-oic acid (2), as well as four known compounds, ent-Kaur-16-en-19-oic acid (3), ent-7β-hydroxykaur-16-en-19-oic acid (4), ent-7-oxokaur-16-en-19-oic acid (5), steppogenin 4′-O-β-d-glucoside (6). Their structures and relative configurations were elucidated on the basis of spectroscopic methods, chemical reactions, and comparison with previously known analogs. All isolates were evaluated for their antimicrobial activity and only diterpenoids were found to possess a potent inhibitor effect against the range of microorganism.     

Sensitivity and Specificity of a Prototype Rapid Diagnostic Test for the Detection of Trypanosoma brucei gambiense Infection: A Multi-centric Prospective Study

Background

A major challenge in the control of human African trypanosomiasis (HAT) is lack of reliable diagnostic tests that are rapid and easy to use in remote areas where the disease occurs. In Trypanosoma brucei gambiense HAT, the Card Agglutination Test for Trypanosomiasis (CATT) has been the reference screening test since 1978, usually on whole blood, but also in a 1/8 dilution (CATT 1/8) to enhance specificity. However, the CATT is not available in a single format, requires a cold chain for storage, and uses equipment that requires electricity. A solution to these challenges has been provided by rapid diagnostic tests (RDT), which have recently become available. A prototype immunochromatographic test, the SD BIOLINE HAT, based on two native trypanosomal antigens (VSG LiTat 1.3 and VSG LiTat 1.5) has been developed. We carried out a non-inferiority study comparing this prototype to the CATT 1/8 in field settings.

Methodology/Principal Findings

The prototype SD BIOLINE HAT, the CATT Whole Blood and CATT 1/8 were systematically applied on fresh blood samples obtained from 14,818 subjects, who were prospectively enrolled through active and passive screening in clinical studies in three endemic countries of central Africa: Angola, the Democratic Republic of the Congo and the Central African Republic. One hundred and forty nine HAT cases were confirmed by parasitology. The sensitivity and specificity of the prototype SD BIOLINE HAT was 89.26% (95% confidence interval (CI) = 83.27–93.28) and 94.58% (95% CI = 94.20–94.94) respectively. The sensitivity and specificity of the CATT on whole blood were 93.96% (95% CI = 88.92–96.79) and 95.91% (95% CI = 95.58–96.22), and of the CATT 1/8 were 89.26% (95% CI = 83.27–93.28) and 98.88% (95% CI = 98.70–99.04) respectively.

Conclusion/Significance

After further optimization, the prototype SD BIOLINE HAT could become an alternative to current screening methods in primary healthcare settings in remote, resource-limited regions where HAT typically occurs.     

The coordinated replication of Vibrio cholerae’s two chromosomes required the acquisition of a unique domain by the RctB initiator

Vibrio cholerae, the pathogenic bacterium that causes cholera, has two chromosomes (Chr1, Chr2) that replicate in a well-orchestrated sequence. Chr2 initiation is triggered only after the replication of the crtS site on Chr1. The initiator of Chr2 replication, RctB, displays activities corresponding with its different binding sites: initiator at the iteron sites, repressor at the 39m sites, and trigger at the crtS site. The mechanism by which RctB relays the signal to initiate Chr2 replication from crtS is not well-understood. In this study, we provide new insights into how Chr2 replication initiation is regulated by crtS via RctB. We show that crtS (on Chr1) acts as an anti-inhibitory site by preventing 39m sites (on Chr2) from repressing initiation. The competition between these two sites for RctB binding is explained by the fact that RctB interacts with crtS and 39m via the same DNA-binding surface. We further show that the extreme C-terminal tail of RctB, essential for RctB self-interaction, is crucial for the control exerted by crtS. This subregion of RctB is conserved in all Vibrio, but absent in other Rep-like initiators. Hence, the coordinated replication of both chromosomes likely results from the acquisition of this unique domain by RctB.     

Gene-dosage mapping of 30 DNA markers on chromosome 21.

Using a slot-blot method for the dosage of single-copy sequences, the copy numbers of 30 chromosome 21 markers were assessed in the blood DNA of 11 patients with partial trisomy or monosomy 21 and in the DNA of a patient-derived human-hamster hybrid cell line carrying a microduplication of chromosome 21. The physical order of these markers on chromosome 21 was thereby determined.