Efficient Pre-mRNA Cleavage Prevents Replication-Stress-Associated Genome Instability

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Interactions among morphotype,nutrition, and temperature impact fitness of an invasive fly

Invasive animals depend on finding a balanced nutritional intake to colonize, survive, and reproduce in new environments. This can be especially challenging during situations of fluctuating cold temperatures and food scarcity, but phenotypic plasticity may offer an adaptive advantage during these periods. We examined how lifespan, fecundity, pre‐oviposition periods, and body nutrient contents were affected by dietary protein and carbohydrate (P:C) ratios at variable low temperatures in two morphs (winter morphs WM and summer morphs SM) of an invasive fly, Drosophila suzukii. The experimental conditions simulated early spring after overwintering and autumn, crucial periods for survival. At lower temperatures, post‐overwintering WM lived longer on carbohydrate‐only diets and had higher fecundity on low‐protein diets, but there was no difference in lifespan or fecundity among diets for SM. As temperatures increased, low‐protein diets resulted in higher fecundity without compromising lifespan, while high‐protein diets reduced lifespan and fecundity for both WM and SM. Both SM and WM receiving high‐protein diets had lower sugar, lipid, and glycogen (but similar protein) body contents compared to flies receiving low‐protein and carbohydrate‐only diets. This suggests that flies spend energy excreting excess dietary protein, thereby affecting lifespan and fecundity. Despite having to recover from nutrient depletion after an overwintering period, WM exhibited longer lifespan and higher fecundity than SM in favorable diets and temperatures. WM exposed to favorable low‐protein diet had higher body sugar, lipid, and protein body contents than SM, which is possibly linked to better performance. Although protein is essential for oogenesis, WM and SM flies receiving low‐protein diets did not have shorter pre‐oviposition periods compared to flies on carbohydrate‐only diets. Finding adequate carbohydrate sources to compensate protein intake is essential for the successful persistence of D. suzukii WM and SM populations during suboptimal temperatures.     

Involvement of the Adhesion GPCRs Latrophilins in the Regulation of Insulin Release

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Continuous fluorescence microphotolysis and correlation spectroscopy using 4Pi microscopy

Continuous fluorescence microphotolysis (CFM) and fluorescence correlation spectroscopy (FCS) permit measurement of molecular mobility and association reactions in single living cells. CFM and FCS complement each other ideally and can be realized using identical equipment. So far, the spatial resolution of CFM and FCS was restricted by the resolution of the light microscope to the micrometer scale. However, cellular functions generally occur on the nanometer scale. Here, we develop the theoretical and computational framework for CFM and FCS experiments using 4Pi microscopy, which features an axial resolution of ∼100 nm. The framework, taking the actual 4Pi point spread function of the instrument into account, was validated by measurements on model systems, employing 4Pi conditions or normal confocal conditions together with either single- or two-photon excitation. In all cases experimental data could be well fitted by computed curves for expected diffusion coefficients, even when the signal/noise ratio was small due to the small number of fluorophores involved.     

Impact of an extruded nucleotide on cleavage activity and dynamic catalytic core conformation of the hepatitis delta virus ribozyme

The self-cleaving hepatitis delta virus (HDV) ribozyme is essential for the replication of HDV, a liver disease causing pathogen in humans. The catalytically critical nucleotide C75 of the ribozyme is buttressed by a trefoil turn pivoting around an extruded G76. In all available crystal structures, the conformation of G76 is restricted by stacking with G76 of a neighboring molecule. To test whether this crystal contact introduces a structural perturbation into the catalytic core, we have analyzed approximately 200 ns of molecular dynamics (MD) simulations. In the absence of crystal packing, the simulated G76 fluctuates between several conformations, including one wherein G76 establishes a perpendicular base quadruplet in the major groove of the adjacent P1 stem. Second-site mutagenesis experiments suggest that the identity of the nucleotide in position 76 (N76) indeed contributes to the catalytic activity of a trans-acting HDV ribozyme through its capacity for hydrogen bonding with P1. By contrast, in the cis-cleaving genomic ribozyme the functional relevance of N76 is less pronounced and not correlated with the P1 sequence. Terbium(III) footprinting and additional MD show that the activity differences between N76 mutants of this ribozyme are related instead to changes in average conformation and modified cross-correlations in the trefoil turn.     

Comparison of element levels in minimal and complex yeast media

The cellular functions are strongly influenced by the composition of the environment. In particular, phenotypes of microbial strains are modulated by concentrations of ions in the culture medium, and differences in element levels may be responsible for a phenotypic variability observed when microbial strains are grown on synthetic versus complex media. In this report, we analyzed the levels of nine elements (magnesium, potassium, sodium, calcium, iron, copper, manganese, zinc, and phosphorus) and sulphate ions in commercially available peptone and yeast extract and compared them with those in yeast nitrogen base routinely used for preparation of synthetic minimal media. We observed that whereas some elements are present at similar levels, the levels of others differ by a factor as high as 20. The observed differences should be taken into account when interpreting different phenotypes observed for microbial strains grown on synthetic versus complex media.     

Genetic basis for the biosynthesis of methylglucose lipopolysaccharides in Mycobacterium tuberculosis

Mycobacteria produce two unusual polymethylated polysaccharides, the 6-O-methylglucosyl-containing lipopolysaccharides (MGLP) and the 3-O-methylmannose polysaccharides, which have been shown to regulate fatty acid biosynthesis in vitro. A cluster of genes dedicated to the synthesis of MGLP was identified in Mycobacterium tuberculosis and Mycobacterium smegmatis. Overexpression of the putative glycosyltransferase gene Rv3032 in M. smegmatis greatly stimulated MGLP production, whereas the targeted disruption of Rv3032 in M. tuberculosis and that of the putative methyltransferase gene MSMEG2349 in M. smegmatis resulted in a dramatic reduction in the amounts of MGLP synthesized and in the accumulation of precursors of these molecules. Disruption of Rv3032 also led to a significant decrease in the glycogen content of the tubercle bacillus, indicating that the product of this gene is likely to be involved in the elongation of more than one alpha-(1-->4)-glucan in this bacterium. Results thus suggest that Rv3032 encodes the alpha-(1-->4)-glucosyltransferase responsible for the elongation of MGLP, whereas MSMEG2349 encodes the O-methyltransferase required for the 6-O-methylation of these compounds.     

The platinum-olefin binding energy in series of (PH<Subscript>3</Subscript>)<Subscript>2</Subscript>Pt(olefin) complexes - a theoretical study

Theoretical investigation of Pt(0)-olefin organometallic complexes containing tertiary phosphine ligands was focused on the strength of platinum-olefin electronic interaction. DFT theoretical study of electronic effects in a substantial number of ethylene derivatives was evaluated in terms of the Pt-olefin binding energy using MP2 correlation theory. Organometallics bearing coordinated olefins with general formula (R¹R²C = CR³R⁴)Pt(PH₃)₂ [R = various substituents] had been selected, including olefins containing both electron-donor substituents as well as electron-withdrawing groups. The stability of the corresponding complexes increases with a strengthening electron-withdrawal ability of the olefin substituents. Figure Representation of (CH₂ = CHR)Pt(PPh₃)₂ and the stability chart