DNA methylation regulated microRNAs in HPV-16-induced head and neck squamous cell carcinoma (HNSCC)

Molecular and Cellular Biochemistry - Epigenetic modifications have been reported to play an important role in regulating gene expression and these modifications become critical when they have a...     

Oxidized kaurene derivatives from leaves of Solidago missouriensis and S. Rigida

Oxidized kaurene derivatives were isolated from the leaves of Solidago missouriensis and S. rigida and identified as kauran-16β-ol, kaur-16-en-19-oic acid and 7β-hydroxykaur-16-en-19-oic acid. The structure of the latter compound was determined by X-ray crystallographic analysis of its methyl ester.     

Intersection of calorie restriction and magnesium in the suppression of genome-destabilizing RNA–DNA hybrids

Dietary calorie restriction is a broadly acting intervention that extends the lifespan of various organisms from yeast to mammals. On another front, magnesium (Mg²⁺) is an essential biological metal critical to fundamental cellular processes and is commonly used as both a dietary supplement and treatment for some clinical conditions. If connections exist between calorie restriction and Mg²⁺ is unknown. Here, we show that Mg²⁺, acting alone or in response to dietary calorie restriction, allows eukaryotic cells to combat genome-destabilizing and lifespan-shortening accumulations of RNA–DNA hybrids, or R-loops. In an R-loop accumulation model of Pbp1-deficient Saccharomyces cerevisiae, magnesium ions guided by cell membrane Mg²⁺ transporters Alr1/2 act via Mg²⁺-sensitive R-loop suppressors Rnh1/201 and Pif1 to restore R-loop suppression, ribosomal DNA stability and cellular lifespan. Similarly, human cells deficient in ATXN2, the human ortholog of Pbp1, exhibit nuclear R-loop accumulations repressible by Mg²⁺ in a process that is dependent on the TRPM7 Mg²⁺ transporter and the RNaseH1 R-loop suppressor. Thus, we identify Mg²⁺ as a biochemical signal of beneficial calorie restriction, reveal an R-loop suppressing function for human ATXN2 and propose that practical magnesium supplementation regimens can be used to combat R-loop accumulation linked to the dysfunction of disease-linked human genes.     

Identification and partial characterization of two species-specific repeat families in the great millet (Sorghum vulgare,Poaceae) genome

The 1.4 kbp Xba I and the 1.3 kbp EcoRI repeat families in great millet were partially characterized with respect to their genomic distribution and their homology with the EcoRI and Xba I families of five other millet DNAs. The digestions of great millet DNA using increasing amounts of the two enzymes show that these two families are disperse in nature. The hybridization of these two families to the genomic digests of great millet indicates that they are arranged in a clustered and scrambled manner. Similarly, the hybridization with the EcoRI and Xba I digests of five other millet DNAs reveals the speciesspecific nature of these two repeat families. The latter also hybridize to the total repetitive fraction of great millet isolated at a highly stringent temperature of 75°C suggesting that the members of these two families are probably largely homogeneous.     

Conductance studies on the interaction of lactose with alkali-metal halides in water and in formamide

The interaction of lactose with alkali-metal halides in solution in water and in formamide has been studied by employing conductance measurements. Conductance data of sodium and potassium halides in water and in formamide saturated with lactose at 50.0 ±0.05° are reported at several temperatures within a range of 25 to 70°. Plots of —log- K against 1/T showed a break at the saturation temperature, where two straight lines intersect one another. Divergence of the pairs of straight lines in these ternary, homogeneous systems has been found to be highly influenced by the structural properties of the solutes. The transitional behavior in the conductance values is explained for the system in terms of solute-solvent interactions involved in the electrolyte-solvent-nonelectrolyte systems.     

Conformational changes in pennisetin using intrinsic fluorescence spectroscopy

Fluorescence spectra of native pennisetin resulted in a single emission peak at 335 nm at excitation wavelength of 274 and 295 nm with quantum yield values for tyrosine and tryptophan as 0.086 and 0.097, respectively. These results indicate the presence of tryptophan residues in a polar environment and quenching of tyrosine residues in the native state of pennisetin. In the presence of an increasing concentration of guanidine hydrochloride (Gdn · HCl), changes such as red shift in emission peak from 335 to 344 nm, decrease in relative fluorescence intensity and increase in quantum yield value were observed, suggesting unfolding of the pennisetin molecule during denaturation. The quenching of tryptophanyl fluorescence by acrylamide and iodide further showed the presence of a single kind of tryptophanyl residue and its polar environment in pennisetin molecule.     

Extracellular invertase from Aspergillus athecius: Isolation and immobilization

Summary A fungal strain isolated from soil and identified asAspergillus athecius, when grown on moistened wheat bran produced large amounts of extracellular invertase. Most of the invertase from the moldy bran was easily extracted by low ionic strength buffer (0.005 M, pH 5.7). The crude invertase immobilized on DEAE cellulose showed not only increased activity (45%) but also greater thermal and storage stability than the free enzyme. The free and the bound enzymes showed a temperature optimum of 50–55°C and a pH optimum of 5.7 and 4.8 respectively. The K_m app. of the bound enzyme was lower than that of the free enzyme.     

Genetic structure, relatedness and helping behaviour in the yellow mongoose in a farmland and a natural habitat

The yellow mongoose Cynictis penicillata is a facultatively social species and provides an opportunity to study the evolution of social behaviour. We examined genetic structure, relatedness and helping behaviour in the yellow mongoose in natural habitat in the Kalahari Desert, where the species lives in small family groups of up to four individuals and shows no cooperative breeding; and in farmland in the Western Cape Province of South Africa, where they live in larger groups of up to 13 individuals, engage in numerous social interactions and show cooperative breeding. The farmland population showed significant inbreeding, and lower genetic variability than the desert population, but there was no evidence of a recent population bottleneck. The genetic relatedness between individuals within social groups and that between future potential helpers and pups were higher in the farmland population than in the desert population. However, based on a limited sample, helping effort (in the farmland population) was not preferentially directed towards kin. Thus, the origin of helping in the farmland population is consistent with kin selection, but in the absence of kin discrimination, future research should investigate whether long-term breeding opportunities or group augmentation contribute to maintaining cooperative breeding in this population.