Heterochromatin protein 1 is involved in control of telomere elongation in Drosophila melanogaster

Telomeres of Drosophila melanogaster contain arrays of the retrotransposon-like elements HeT-A and TART. Their transposition to broken chromosome ends has been implicated in chromosome healing and telomere elongation. We have developed a genetic system which enables the determination of the frequency of telomere elongation events and their mechanism. The frequency differs among lines with different genotypes, suggesting that several genes are in control. Here we show that the Su(var)2-5 gene encoding heterochromatin protein 1 (HP1) is involved in regulation of telomere length. Different Su(var)2-5 mutations in the heterozygous state increase the frequency of HeT-A and TART attachment to the broken chromosome end by more than a hundred times. The attachment occurs through either HeT-A/TART transposition or recombination with other telomeres. Terminal DNA elongation by gene conversion is greatly enhanced by Su(var)2-5 mutations only if the template for DNA synthesis is on the same chromosome but not on the homologous chromosome. The Drosophila lines bearing the Su(var)2-5 mutations maintain extremely long telomeres consisting of HeT-A and TART for many generations. Thus, HP1 plays an important role in the control of telomere elongation in D. melanogaster.     

Substrate activation in acetylcholinesterase induced by low pH or mutation in the pi-cation subsite

Substrate inhibition is considered a defining property of acetylcholinesterase (AChE), whereas substrate activation is characteristic of butyrylcholinesterase (BuChE). To understand the mechanism of substrate inhibition, the pH dependence of acetylthiocholine hydrolysis by AChE was studied between pH 5 and 8. Wild-type human AChE and its mutants Y337G and Y337W, as well as wild-type Bungarus fasciatus AChE and its mutants Y333G, Y333A and Y333W were studied. The pH profile results were unexpected. Instead of substrate inhibition, wild-type AChE and all mutants showed substrate activation at low pH. At high pH, there was substrate inhibition for wild-type AChE and for the mutant with tryptophan in the pi-cation subsite, but substrate activation for mutants containing small residues, glycine or alanine. This is particularly apparent in the B. fasciatus AChE. Thus a single amino acid substitution in the pi-cation site, from the aromatic tyrosine of B. fasciatus AChE to the alanine of BuChE, caused AChE to behave like BuChE. Excess substrate binds to the peripheral anionic site (PAS) of AChE. The finding that AChE is activated by excess substrate supports the idea that binding of a second substrate molecule to the PAS induces a conformational change that reorganizes the active site.     

Xylose and cellobiose fermentation to ethanol by the thermotolerant methylotrophic yeast Hansenula polymorpha

Wild-type strains of the thermotolerant methylotrophic yeast Hansenula polymorpha are able to ferment glucose, cellobiose and xylose to ethanol. H. polymorpha most actively fermented sugars to ethanol at 37 degrees C, whereas the well-known xylose-fermenting yeast Pichia stipitis could not effectively ferment carbon substrates at this temperature. H. polymorpha even could ferment both glucose and xylose up to 45 degrees C. This species appeared to be more ethanol tolerant than P. stipitis but more susceptible than Saccharomyces cerevisiae. A riboflavin-deficient mutant of H. polymorpha increased its ethanol productivity from glucose and xylose under suboptimal supply with riboflavin. Mutants of H. polymorpha defective in alcohol dehydrogenase activity produced lower amounts of ethanol from glucose, whereas levels of ethanol production from xylose were identical for the wild-type strain and the alcohol dehydrogenase-defective mutant.     

Regeneration of the visual system in gastropods (Mollusca)

Abstract. The topic of tissue and organ regeneration has been of interest to life scientists ever since the phenomenon was noticed. The reason for this is obvious: if one can learn what drives and controls regeneration, i.e., how lost or damaged structures can be replaced, one not only has a better chance to understand an animal's embryogenesis and evolutionary relationship with other taxa, but one would also be in a better position to treat organ loss or tissue damage in humans. In this context, the possible restitution of individual sensory neurons or nerve projections has been of special interest to us. We identified central visual projections in several gastropod species and found that: (1) projections are very extensive across the brain and (2) they have connections with other systems and organs (including, most likely, non-ocular skin photoreceptors) that may be involved in the integration of signals from different sensors. Investigations of afferent and efferent visual elements at a morphological level should help reveal the neuronal basis of a gastropod's behavioral reactions.     

The Impacts of Household Consumption and Options for Change

This introductory article situates the contributions that comprise this special issue within the field of sustainable consumption and production (SCP) studies. After a brief review of the policy history surrounding SCP, we organize our discussion and the subsequent collection of articles into two groups. The first suite of articles views the environmental impacts associated with household consumption from the perspectives of different consumer groups, income levels, and geographic areas. This work confirms and refines several insights that have been developing over the past several years, namely that food and beverages, mobility, housing, and energy-using products are the most critical consumption domains from the standpoint of environmental sustainability and that higher household income leads to greater (but less than proportional) impacts. The second subset of articles analyzes the potential for mitigating these impacts through behavioral changes and innovation strategies. Although the contributions to this special issue describe several noteworthy examples of information- and team-based initiatives to catalyze behavioral changes, the state of knowledge pertaining to this aspect of the consumption problem is much more inchoate. Research on the formulation and implementation of effective "change management for sustainable consumption" should be treated as an area of priority attention for industrial ecologists.     

Synthesis of 7-benzyl-5-(piperidin-1-yl)-6,7,8,9-tetrahydro-3H-pyrazolo[3,4-c][2,7]naphthyridin-1-ylamine and its analogs as bombesin receptor subtype-3 agonists

The original structure of a high-throughput screening hit obtained from an external vendor was revised based on multiple NMR studies. The active compound was re-synthesized via a novel route and its structure and biological activity as a BRS-3 agonist were unambiguously confirmed. Multi-gram quantities of the hit were prepared for pharmacokinetic and efficacy studies. The synthetic strategy allowed for the preparation of multiple analogs for SAR exploration.     

pH-dependent binding of the Epsin ENTH domain and the AP180 ANTH domain to PI(4,5)P2-containing bilayers

Epsin and AP180 are essential components of the endocytotic machinery, which controls internalization of protein receptors and other macromolecules at the cell surface. Epsin and AP180 are recruited to the plasma membrane by their structurally and functionally related N-terminal ENTH and ANTH domains that specifically recognize PtdIns(4,5)P₂. Here, we show that membrane anchoring of the ENTH and ANTH domains is regulated by the acidic environment. Lowering the pH enhances PtdIns(4,5)P₂ affinity of the ENTH and ANTH domains reinforcing their association with lipid vesicles and monolayers. The pH dependency is due to the conserved histidine residues of the ENTH and ANTH domains, protonation of which is necessary for the strong PtdIns(4,5)P₂ recognition, as revealed by liposome binding, surface plasmon resonance, NMR, monolayer surface tension and mutagenesis experiments. The pH sensitivity of the ENTH and ANTH domains is reminiscent to the pH dependency of the FYVE domain suggesting a common regulatory mechanism of membrane anchoring by a subset of the PI-binding domains.     

Serum soluble Fas ligand (sFasL) in patients with primary squamous cell carcinoma of the esophagus

Esophageal carcinomas have been shown to express Fas ligand (FasL) and down-regulate Fas to escape from host immune surveillance. Circulating soluble FasL (sFasL) has been suggested to provide protection from Fas-mediated apoptosis. The aim of this study was to assess serum sFasL levels in esophageal cancer. The pretreatment levels of sFasL in the serum of 100 patients with esophageal squamous cell cancer and 41 healthy volunteers were determined by ELISA. Probability of survival was calculated according to the method of Kaplan-Meier. The prognostic influence of high and low level of sFasL was analyzed with the log-rank test. The mean serum level of sFasL in patients with esophageal cancer was significantly higher than that in healthy donors (1.567+/-1.786 vs 0.261+/-0.435, p<0.0001). The levels of serum sFasL were significantly higher in advanced stages (II vs IV p<0.034; III vs IV p<0.041; except II vs III p=0.281), patients with lymph node (N0 vs N1 p<0.0389) or distant (M0 vs. M1 p<0.0388) metastases and significantly lower in patients with well differentiated tumors (G1 vs G2 p<0.0272). The serum levels of soluble FasL were not related to gender, age, tumor size, T-stage, tobacco smoking and history of chronic alcohol intake. The survival difference between pretreatment high and low level of sFasL in surgery and chemio- and/or radiotherapy group was not statistically significant (p=0.525; p=0.840). Our results indicate that elevated serum sFasL levels might be associated with a disease progression in patients with esophageal squamous cell carcinoma.     

A tag-based approach for high-throughput analysis of CCWGG methylation

Non-CpG methylation occurring in the context of CNG sequences is found in plants at a large number of genomic loci. However, there is still little information available about non-CpG methylation in mammals. Efficient methods that would allow detection of scarcely localized methylated sites in small quantities of DNA are required to elucidate the biological role of non-CpG methylation in both plants and animals. In this study, we tested a new whole genome approach to identify sites of CCWGG methylation (W is A or T), a particular case of CNG methylation, in genomic DNA. This technique is based on digestion of DNAs with methylation-sensitive restriction endonucleases EcoRII-C and AjnI. Short DNAs flanking methylated CCWGG sites (tags) are selectively purified and assembled in tandem arrays of up to nine tags. This allows high-throughput sequencing of tags, identification of flanking regions, and their exact positions in the genome. In this study, we tested specificity and efficiency of the approach.