Molecular evolution of mammalian lactate dehydrogenase-A genes and pseudogenes: association of a mouse processed pseudogene with a B1 repetitive sequence

A mouse genomic clone containing a lactate dehydrogenase-A (LDH-A) processed pseudogene and a B1 repetitive element was isolated, and a nucleotide sequence of approximately 3 kb was determined. The pseudogene and B1 element are flanked by perfect 13-bp repeats, and the B1 sequence starts at 14 nucleotides 3' to the presumptive polyadenylation signal of the pseudogene. The nucleotide sequences of the LDH-A genes and processed pseudogenes from mouse, rat, and human were compared, and a phylogenetic tree was constructed. The rate and pattern of nucleotide substitutions in the LDH-A pseudogenes are similar to previously reported results (Li et al. 1984). The average rate of nucleotide substitutions in the LDH-A pseudogenes is 4.3 X 10(- 9)/site/year. The substitutions of C----T and G----A are most frequent, and A----G substitutions are relatively high. The rate of synonymous substitutions in the LDH-A genes is 5.3 X 10(-9), which is not significantly higher than the average rate of 4.7 X 10(-9) for 35 mammalian genes. The rate of nonsynonymous substitutions in the LDH-A genes is 0.20 X 10(-9), which is considerably lower than the average rate of 0.88 X 10(-9) for 35 mammalian genes. Thus, the mammalian LDH-A gene appears to be highly conserved in evolution.      

Changes to airborne pollen counts across Europe

A progressive global increase in the burden of allergic diseases has affected the industrialized world over the last half century and has been reported in the literature. The clinical evidence reveals a general increase in both incidence and prevalence of respiratory diseases, such as allergic rhinitis (common hay fever) and asthma. Such phenomena may be related not only to air pollution and changes in lifestyle, but also to an actual increase in airborne quantities of allergenic pollen. Experimental enhancements of carbon dioxide (CO[Formula: see text]) have demonstrated changes in pollen amount and allergenicity, but this has rarely been shown in the wider environment. The present analysis of a continental-scale pollen data set reveals an increasing trend in the yearly amount of airborne pollen for many taxa in Europe, which is more pronounced in urban than semi-rural/rural areas. Climate change may contribute to these changes, however increased temperatures do not appear to be a major influencing factor. Instead, we suggest the anthropogenic rise of atmospheric CO[Formula: see text] levels may be influential.     

The glucose transport system of the hyperthermophilic anaerobic bacterium Thermotoga neapolitana

The glucose transport system of the extremely thermophilic anaerobic bacterium Thermotoga neapolitana was studied with the nonmetabolizable glucose analog 2-deoxy-D-glucose (2-DOG). T. neapolitana accumulated 2-DOG against a concentration gradient in an intracellular free sugar pool that was exchangeable with external source of energy, such as pyruvate, and was inhibited by arsenate and gramicidin D. There was no phosphoenolpyruvate-dependent phosphorylation of glucose, 2-DOG, or fructose by cell extracts or toluene-treated cells, indicating the absence of a phosphoenolpyruvate:sugar phosphotransferase system. These data indicate that D-glucose is taken up by T. neapolitana via an active transport system that is energized by an ion gradient generated by ATP, derived from substrate-level phosphorylation.     

Ustilago maydis Mating Hyphae Orient Their Growth toward Pheromone Sources

Snetselaar, K. M., Bolker, M., and Kahmann, R. 1996. Ustilago maydis mating hyphae orient their growth toward pheromone sources. Fungal Genetics and Biology 20, 299-312. When small drops of Ustilago maydis sporidia were placed 100-200 μm apart on agar surfaces and covered with paraffin oil, sporidia from one drop formed thin hyphae that grew in a zig-zag fashion toward the other drop if it contained sporidia making the appropriate pheromone. For example, a2b2 mating hyphae grew toward a1b1 and a1b2 mating hyphae, and the filaments eventually fused tip to tip. Time-lapse photography indicated that the mating hyphae can rapidly change orientation in response to nearby compatible sporidia. When exposed to pheromone produced by cells in an adjacent drop, haploid sporidia with the a2 allele began elongating before sporidia with the a1 allele. Sporidia without functional pheromone genes responded to pheromone although they did not induce a response, and sporidia without pheromone receptors induced formation of mating hyphae although they did not form mating hyphae. Diploid sporidia heterozygous at b but not at a formed straight, rigid, aerial filaments when exposed to pheromone produced by the appropriate haploid sporidia. Again, the a2a2b1b2 strain formed filaments more quickly than the a1a1b1b2 strain. Taken together, these results suggest that the a2 pheromone diffuses less readily or is degraded more quickly than the a1 pheromone.     

In Vitro Bioavailability of Calcium,Magnesium, Iron,Zinc, and Copper from Gluten-Free Breads Supplemented with Natural Additives

The aim of this study was to measure the content of calcium, magnesium, iron, zinc, and copper and determine the bioavailability of these ingredients in gluten-free breads fortified with milk and selected seeds. Due to the increasing prevalence of celiac disease and mineral deficiencies, it has become necessary to produce food with higher nutritional values which maintains the appropriate product characteristics. This study was designed for gluten-free breads fortified with milk and seeds such as flax, poppy, sunflower seeds, pumpkin seeds or nuts, and flour with amaranth. Subsequently, digestion was performed in vitro and the potential bioavailability of the minerals was measured. In the case of calcium, magnesium, iron, and copper, higher bioavailability was observed in rice bread, and, in the case of copper and zinc, in buckwheat bread. This demonstrated a clear increase in bioavailability of all the minerals when the bread were enriched. However, satisfactory results are obtained only for the individual micronutrients.     

The N-terminus of Drosophila SU(VAR)3-9 mediates dimerization and regulates its methyltransferase activity

In most eukaryotes, the histone methyltransferase SU(VAR)3-9 and its orthologues play a major role in the function of centromeric heterochromatin. Although the methyltransferase domain is required for the formation of a fully functional centromere, mutations within other regions of the gene such as the N-terminus also have a strong impact on its in vivo function. To analyze the contribution of the N-terminus on the methyltransferase activity, we have expressed the full-length Drosophila SU(VAR)3-9 (dSU(VAR)3-9) together with various N-terminal deletions in Escherichia coli and analyzed the structural and enzymatic properties of the purified recombinant enzymes. Full-length dSU(VAR)3-9 specifically methylates lysine 9 within histone H3 on peptides, on intact histones, and, to a lesser extent, on nucleosomes. A detailed analysis of the reaction products shows that dSU(VAR)3-9 adds two methyl groups to an unmethylated H3 tail peptide in a nonprocessive manner. The full-length enzyme elutes with an apparent molecular weight of 160 kDa from a gel filtration column, which indicates the formation of a dimer. This property is dependent on an intact N-terminus. In contrast to the full-length enzymes, proteins lacking the N-terminus fail to dimerize, and show a 10-fold lower specific activity and a linear dependence of methyltransferase activity on enzyme concentration. A N-terminal peptide containing amino acids 1-152 of dSU(VAR)3-9 is sufficient to mediate this interaction in vitro. The dimerization of dSU(VAR)3-9 and the subsequent increase of its methyltransferase activity provide a starting point to understand the molecular details of the formation of heterochromatic structures in vivo.     

Arg538 to Cys mutation in a CpG dinucleotide of the human biotinidase gene is the second most common cause of profound biotinidase deficiency in symptomatic children

Biotinidase deficiency is an autosomal recessively inherited disorder in the recycling of the vitamin biotin. The most common mutation that causes profound biotinidase deficiency in symptomatic individuals is a deletion/insertion (G₉₈:d7i3) that occurs in exon B of the biotinidase gene. We now report the second most common mutation, a C-to-T substitution (position 1612) in a CpG dinucleotide in exon D of the biotinidase gene. This mutation results in the substitution of a cysteine for arginine538 (designated R538C) and was found in 10 of 30 symptomatic children with profound biotinidase deficiency, 5 of whom also have the G₉₈:d7i3 mutation. This mutation was not found in DNA samples from 32 individuals with normal biotinidase activity, but was found in one individual with enzyme activity in the heterozygous range. This mutation was not detected in 371 randomly selected, normal individuals using allele-specific oligonucleotide hybridization analysis. Aberrant biotinidase protein was not detectable in extracts of fibroblasts from a child who is homozygous for the R538C mutation, but was present in less than normal concentration in identical extracts treated with β-mercaptoethanol. Because there is no detectable biotinidase protein in sera of children who are homozygous for the R538C mutation and in combination with the deletion/insertion mutation, the R538C mutation likely results in inappropriate intra- or intermolecular disulfide bond formation, more rapid degradation of the aberrant enzyme, and failure to secrete the residual aberrant enzyme from the cells into blood. Received: 13 August 1996 / Revised: 13 November 1996