The Lyon and the LINE hypothesis

X-chromosome inactivation (XCI) was first suggested as an explanation for the variegated phenotypes in mice heterozygous for X-linked colour genes or for X-autosome translocations involving autosomal coat colour genes. The effects seen in X-autosome translocations led to the suggestion of an X-inactivation centre (Xic) from which the inactivation was initiated, and this suggestion has led to major advances in understanding. Another feature of X-autosome translocations is incomplete inactivation of the attached autosomal segment, implying that the X-chromosome is enriched in features favouring inactivation. Interspersed repeat elements, and in particular long interspersed elements (LINEs), have been suggested as the relevant enriching features. Recent evidence concerning this hypothesis is discussed.     

Hepatocyte growth factor/scatter factor and its interaction with heparan sulphate and dermatan sulphate

Hepatocyte growth factor (HGF)/scatter factor (SF) is a unique growth factor, in that it binds both heparan sulphate (HS) and dermatan sulphate (DS). The sequences in HS and DS that specifically interact with and modulate HGF/SF activity have not yet been fully identified. Ascidian DS, which uniquely possesses O-sulphation at C-6 (and not C-4) of its N -acetylgalactosamine unit, was analysed for HGF/SF-binding activity in the biosensor. The kinetic analysis revealed a strong, biologically relevant interaction with an equilibrium dissociation constant ( K (d)) of approx. 1 nM. An Erk activation assay also demonstrated stimulation of the MAP kinase pathway downstream of the Met receptor following addition of both HGF/SF and ascidian DS to the glycosaminoglycan-deficient CHO-745 mutant cell line. Furthermore, the activation of Met and the MAP kinase pathway by HGF/SF and ascidian DS leads to a cellular response in the form of migration.     

The C. elegans apoptotic nuclease NUC-1 is related in sequence and activity to mammalian DNase II

The Caenorhabditis elegans nuc-1 gene has previously been implicated in programmed cell death due to the presence of persistent undegraded apoptotic DNA in nuc-1 mutant animals. In this report, we describe the cloning and characterization of nuc-1, which encodes an acidic nuclease with significant sequence similarity to mammalian DNase II. Database searches performed with human DNase II protein sequence revealed a significant similarity with the predicted C. elegans C07B5.5 ORF. Subsequent analysis of crude C. elegans protein extracts revealed that wild-type animals contained a potent endonuclease activity with a cleavage preference similar to DNase II, while nuc-1 mutant worms demonstrated a marked reduction in this nuclease activity. Sequence analysis of C07B5.5 DNA and mRNA also revealed that nuc-1(e1392), but not wild-type animals contained a nonsense mutation within the CO7B5.5 coding region. Furthermore, nuc-1 transgenic lines carrying the wild-type C07B5.5 locus demonstrated a complete complementation of the nuc-1 mutant phenotype. Our results therefore provide compelling evidence that the C07B5.5 gene encodes the NUC-1 apoptotic nuclease and that this nuclease is related in sequence and activity to DNase II.     

556例多发伤患者的急诊救治临床分析

目的探讨多发伤患者的救治策略。方法回顾分析我科2000年1月至2008年5月急诊抢救的556例多发伤患者的临床资料。结果 16例患者经抢救无效死亡,死亡率2.88%;其余患者均经紧急抢救及行必要实验室检查,病情稳定,好转率达97.12%。平均抢救时间为(1.37±1.05)h。结论强化多发伤的急诊科早期救治,树立创伤急救"黄金1 h"观念,是提高多发伤患者生存率及降低死亡率的关键。     

The structure of eukaryotic translation initiation factor-4E from wheat reveals a novel disulfide bond

Eukaryotic translation initiation factor-4E (eIF4E) recognizes and binds the m(7) guanosine nucleotide at the 5' end of eukaryotic messenger RNAs; this protein-RNA interaction is an essential step in the initiation of protein synthesis. The structure of eIF4E from wheat (Triticum aestivum) was investigated using a combination of x-ray crystallography and nuclear magnetic resonance (NMR) methods. The overall fold of the crystallized protein was similar to eIF4E from other species, with eight beta-strands, three alpha-helices, and three extended loops. Surprisingly, the wild-type protein did not crystallize with m(7)GTP in its binding site, despite the ligand being present in solution; conformational changes in the cap-binding loops created a large cavity at the usual cap-binding site. The eIF4E crystallized in a dimeric form with one of the cap-binding loops of one monomer inserted into the cavity of the other. The protein also contained an intramolecular disulfide bridge between two cysteines (Cys) that are conserved only in plants. A Cys-to-serine mutant of wheat eIF4E, which lacked the ability to form the disulfide, crystallized with m(7)GDP in its binding pocket, with a structure similar to that of the eIF4E-cap complex of other species. NMR spectroscopy was used to show that the Cys that form the disulfide in the crystal are reduced in solution but can be induced to form the disulfide under oxidizing conditions. The observation that the disulfide-forming Cys are conserved in plants raises the possibility that their oxidation state may have a role in regulating protein function. NMR provided evidence that in oxidized eIF4E, the loop that is open in the ligand-free crystal dimer is relatively flexible in solution. An NMR-based binding assay showed that the reduced wheat eIF4E, the oxidized form with the disulfide, and the Cys-to-serine mutant protein each bind m(7)GTP in a similar and labile manner, with dissociation rates in the range of 20 to 100 s(-1).     

Radiation-induced lung adenocarcinoma is associated with increased frequency of genes inactivated by promoter hypermethylation

Epigenetic inactivation of genes by promoter hypermethylation, a major mechanism in the initiation and progression of tobacco-induced cancer, has also been associated with lung cancer induced through environmental and occupational exposures. Our previous study of gene methylation in workers from the MAYAK nuclear enterprise identified a significantly higher prevalence for methylation of the p16 gene (CDKN2A) in adenocarcinomas from workers compared to tumors from non-worker controls. The purpose of this investigation was to determine whether genes in addition to p16 are "targeted" for silencing and whether overall gene methylation was more common in radiation-induced adenocarcinoma. A significant increase in the prevalence of methylation of GATA5 was seen in tumors from workers compared to tumors from controls. The prevalence for methylation of PAX5 beta and H-cadherin did not differ in tumors from workers and controls. Evaluating the frequency for methylation of a five-gene panel revealed that 93% of adenocarcinomas from workers compared to 66% of tumors from controls were methylated for at least one gene. Moreover, a twofold increase was seen in the number of tumors methylated for three or more genes for tumors from workers compared to controls. Increased frequency for inactivation of genes by promoter hypermethylation and targeting of tumor suppressor genes such as GATA5 may be factors that contribute to the increased risk for lung cancer associated with radiation exposure.     

Impact of plant density and microbial composition on water quality from a free water surface constructed wetland

AIMS: To correlate microbial community composition and water quality changes within wetland cells containing varying plant densities and composition in a free water surface (FWS) constructed wetland. METHODS AND RESULTS: Water chemistry was monitored weekly for nitrate, orthophosphate, and suspended solids, at various sites throughout the wetland for 6 months. Treatment ponds with 50% plant cover had about a 96.3% nitrate removal. The average change between the influent and effluent was 50-60% nitrate removal and 40-50% orthophosphate removal. Community profile of total DNA, generated by using denaturing gradient gel electrophoresis (DGGE), was used to determine the major microbial composition associated with the wetland sediment, rhizosphere, and surface water. Bacterial cloned libraries were constructed, and 300 clones were analysed by amplified ribosomal DNA restriction analysis (ARDRA) and grouped into operational taxonomic units (OTUs). A total of 35, 31, and 36 different OTU were obtained from sediment, rhizosphere, and surface water, respectively. The bacterial members within the dominant group of our clone library belonged to unclassified taxa, while the second predominant group consisted of members of the phylum Proteobacteria. The dominant organisms within the class were in the gamma, beta, and delta classes. CONCLUSION: Microbial diversity as determined by Shannon-Weaver index (H) was higher in the wetland cells with 50% plant density than the 100%. This was in agreement with the most efficient wetland contaminant removal units. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides evidence that wetlands with 50% plant cover may promote the growth of diverse microbial communities that facilitate decomposition of chemical pollutants in surface water, and improve water quality.     

Endogenous retroviral insertion in Cryge in the mouse No3 cataract mutant

No3 (nuclear opacity 3) is a novel congenital nuclear cataract in mice. Microsatellite mapping placed the No3 locus on chromosome 1 between D1Mit480 (32cM) and D1Mit7 (41cM), a region containing seven crystallin genes; Cryba2 and the Cryga-Crygf cluster. Although polymorphic variants were observed, no candidate mutations were found for six of the genes. However, DNA walking identified a murine endogenous retrovirus (IAPLTR1: ERVK) insertion in exon 3 of Cryge, disrupting the coding sequence for gammaE-crystallin. Recombinant protein for the mutant gammaE was completely insoluble. The No3 cataract is mild compared with the effects of similar mutations of gammaE. Quantitative RT-PCR showed that gammaE/F mRNA levels are reduced in No3, suggesting that the relatively mild phenotype results from suppression of gammaE levels due to ERVK insertion. However, the severity of cataract is also strain dependent suggesting that genetic background modifiers also play a role in the development of opacity.