Alteration of metallothionein mRNA in bay scallop Argopecten irradians under cadmium exposure and bacteria challenge

Metallothionein (MT) is a superfamily of cysteine-rich proteins contributing to metal metabolism, detoxification of heavy metals, and immune response such as protecting against ionizing radiation and antioxidant defense. A metallothionein (designated AiMT2) gene was identified and cloned from bay scallop, Argopecten irradians. The full length cDNA of AiMT2 consisted of an open reading frame (ORF) of 333 bp encoding a protein of 110 amino acids. with nine characteristic Cys-X-Cys, five Cys-X-X-Cys, five Cys-X-X-X-Cys and two Cys-Cys motif arrangements and a conserved structural pattern Cys-x-Cys-x(3)-Cys-Tyr-x(3)Cys-x-Cys-x(3)-Cys-x-Cys-Arg at the C-terminus. The cloned ANT showed about 50% identity in the deduced amino acid sequence with previously published MT sequences of mussels and oysters. The conserved structural pattern and the close phylogenetic relationship of AiMT2 shared with MTs from other mollusc especially bivalves indicated that AiMT2 was a new member of molluscan MT family. The mRNA transcripts in hemolymph of AiMT2 under cadmium (Cd) exposure and bacteria challenge were examined by real-time RT-PCR. The mRNA expression of AiMT2 was up-regulated to 3.99-fold at 2 h after Listonella anguillarum challenge, and increased drastically to 66.12-fold and 126.96-fold at 16 and 32 h post-challenge respectively. Cadmium ion exposure could induce the expression of AiMT2, and the expression level increased 2.56-fold and 6.91-fold in hemolymph respectively after a 10-day exposure of 100 mu g L-1 and 200 mu g L-1 CdCl2. The sensitivity of AiMT2 to bacteria challenge and cadmium stress indicated it was a new Cd-dependent MT in bay scallop and also regulated by an immune challenge. The changes in the expression of AiMT2 could be used as an indicator of exposure to metals in pollution monitoring programs and oxidative stress, and bay scallop as a potential sentinel organism for the cadmium contamination in aquatic environment. (C) 2008 Elsevier Inc. All rights reserved.

Pervasive autocorrelation of the chemical index of alteration in sedimentary profiles and its palaeoenvironmental implications

The chemical index of alteration has been used widely for reconstruction of the palaeoclimate. However, the mechanisms and environmental factors controlling the chemical index of alteration of sediments are not yet fully understood. In this study, autocorrelations of the chemical index of alteration in nine sedimentary profiles, from both the land and the sea, spanning different geological times, are discussed. The sediments of these profiles have different origins (dust, fluvial or ocean sediments) and are from various climate situations and sedimentary environments. Autocorrelations of chemical index of alteration series are ubiquitously evident in all profiles. It is suggested here that autocorrelations may be caused by post-depositional changes such as persistent weathering and diagenesis. As a result, the chemical index of alteration may not reflect climatic conditions during the time of sediment deposition. This study strongly recommends the confirmation of the reliability and veracity of the chemical index of alteration before it is adopted to evaluate the weathering degree of parent rocks and to reconstruct the past climate. Significant autocorrelations in loess profiles were specifically observed, suggesting that the existing understanding of loess deposition in terms of climate conditions requires re-examination, and that previous reconstructions of rapid climate changes (for example, in centennial-millennial scales) should be treated with caution.

Increased Promiscuity of Human Galactokinase Following Alteration of a Single Amino Acid Residue Distant from the Active Site

Galactokinase catalyses the site-and stereospecific phosphorylation of galactose at the expense of ATP. The specificity of bacterial galactokinase enzymes can be broadened by alteration of a tyrosine residue to a histidine. The effects of altering the equivalent residue in human galactokinase (Tyr379) were investigated by testing all 19 possible variants. All of these alterations, except Y379P, resulted in soluble protein on expression in Escherichia coli and all the soluble variants could catalyse the phosphorylation of galactose, except Y379A and Y379E. The variants Y379C, Y379K, Y379R, Y379S and Y379W were all able to catalyse the phosphorylation of a variety of monosaccharides, including ones that are not acted on by the wild-type enzyme. Novel substrates for these variant galactokinases included D-mannose and D-fructose. The latter monosaccharide is presumed to react in the pyranose configuration. Molecular modelling suggested that the alterations do not cause changes to the overall structure of the enzyme. However, alteration of Tyr379 increases the flexibility of the peptide backbone in regions surrounding the active site. Therefore, it is proposed that alteration of Tyr379 affects the substrate specificity by the propagation of changes in flexibility to the active site, permitting a broader range of compounds to be accommodated.

Evidence for Alteration of EZH2, BMI1, and KDM6A and Epigenetic Reprogramming in Human Papillomavirus Type 16 E6/E7-Expressing Keratinocytes

A number of epigenetic alterations occur in both the virus and host cellular genomes during human papillomavirus (HPV)-associated carcinogenesis, and investigations of such alterations, including changes in chromatin proteins and histone modifications, have the potential to lead to therapeutic epigenetic reversion. We report here that transformed HPV16 E6/E7-expressing primary human foreskin keratinocytes (HFKs) (E6/E7 cells) demonstrate increased expression of the PRC2 methyltransferase EZH2 at both the mRNA and protein levels but do not exhibit the expected increase in trimethylated H3K27 (H3K27me3) compared to normal keratinocytes. In contrast, these cells show a reduction in global H3K27me3 levels in vitro, as well as upregulation of the KDM6A demethylase. We further show for the first time that transformation with the HPV16 E6 and E7 oncogenes also results in an increase in phosphorylated EZH2 serine 21 (P-EZH2-Ser21), mediated by active Akt, and in a downregulation of the PRC1 protein BMI1 in these cells. High-grade squamous cervical intraepithelial lesions also showed a loss of H3K27me3 in the presence of increased expression of EZH2. Correlating with the loss of H3K27me3, E6/E7 cells exhibited derepression of specific EZH2-, KMD6A-, and BMI1-targeted HOX genes. These results suggest that the observed reduction in H3K27me3 may be due to a combination of reduced activities/levels of specific polycomb proteins and increases in demethylases. The dysregulation of multiple chromatin proteins resulting in the loss of global H3K27me3 and the transcriptional reprogramming in HPV16 E6/E7-infected cells could provide an epigenetic signature associated with risk and/or progression of HPV16-associated cancers, as well as the potential for epigenetic reversion in the future.

The alteration of the structural properties and photocatalytic activity of TiO2 following exposure to non-linear irradiation sources

When TiO2 powder was irradiated with a laser light (>0.8 MW peak pulse power (PPP) at 355 nm) a visible change in its colour from white to dark blue was observed. The initial rate of change of the total colour difference was related to the laser light intensity and the longer the irradiation time the more substantial the colour change. The result of X-ray diffraction (XRD) studies showed that the crystal structure of the TiO2 developed a more rutile form after laser exposure. ESR studies indicated that the colour change was associated with the generation of Ti(III) species in the photocatalyst. Electron microscopic studies showed that more spherical shaped particles of TiO2 were observed after laser treatment although the average particle size remained largely unchanged. No significant changes in the band gap or the surface area of the laser modified TiO2 were observed. The laser modified photocatalyst showed no enhancement in activity for the destruction of methylene blue, rhodamine B and stearic acids, indicating that the rutile/anatase ratio is unimportant in the destruction of the test pollutants used in this work, via TiO2 photocatalysis

Analysis of alteration of p75NTR processing and signalling by PS2 mutation and gamma-secretase inhibition

The presenilins (PSs) were identified as causative genes in cases of early-onset familial Alzheimer's disease (AD) and current evidence indicates that PSs are part of the gamma-secretase complex responsible for proteolytic processing of type I membrane proteins. p75NTR, a common neurotrophin receptor, was shown to be subject to gamma-secretase processing. However, it is not clear if the p75NTR downstream signal is altered in response to gamma-secretase cleavage, and further there is a possibility that AD-related PS mutations may affect this cleavage, resulting in pathogenic alterations in signal transduction. In this study, we confirmed that p75NTR downstream signalling is altered by PS2 mutation or gamma-secretase inhibition in SHSY-5Y cells. The activity of the small GTPase RhoA is strongly affected by these treatments. This study demonstrates that gamma-secretase and PS2 play an important role in regulating neurotrophin signal transduction and either mutation of PS2 or inhibition of gamma-secretase disturbs this function.

Pristine Early Eocene Wood Buried Deeply in Kimberlite from Northern Canada

We report exceptional preservation of fossil wood buried deeply in a kimberlite pipe that intruded northwestern Canada's Slave Province 53.3±0.6 million years ago (Ma), revealed during excavation of diamond source rock. The wood originated from forest surrounding the eruption zone and collapsed into the diatreme before resettling in volcaniclastic kimberlite to depths >300 m, where it was mummified in a sterile environment. Anatomy of the unpermineralized wood permits conclusive identification to the genus Metasequoia (Cupressaceae). The wood yields genuine cellulose and occluded amber, both of which have been characterized spectroscopically and isotopically. From cellulose d O and d H measurements, we infer that Early Eocene paleoclimates in the western Canadian subarctic were 12-17°C warmer and four times wetter than present. Canadian kimberlites offer Lagerstätte-quality preservation of wood from a region with limited alternate sources of paleobotanical information. © 2012 Wolfe et al.

Alteration of beta-tubulin in Nicotiana plumbaginifolia confers resistance to amiprophos-methyl

A Nicotiana plumbaginifolia plant (apm5(r)) resistant to amiprophos-methyl (APM), a phosphoroamide herbicide, was isolated from protoplasts prepared from leaves of haploid plants. Genetic analysis revealed that the resistance is coded for by a dominant nuclear mutation and is associated with the increased stability of cortical microtubules. Two-dimensional polyacrylamide-gel electrophoresis, combined with immunoblotting using anti-tubulin monoclonal antibodies, showed that part of the beta-tubulin in the resistant plant possessed lower isoelectric points than the beta-tubulin of susceptible wild-type plants. These results provide evidence that the resistance to APM is associated with a mutation in a beta-tubulin gene. The APM-resistant line showed cross-resistance to trifluralin, a dinitroaniline herbicide, suggesting a common mechanism of resistance between these two classes of herbicides.