A mutational study of Cnu reveals attractive forces between Cnu and H-NS

Cnu is a small 71-amino acid protein that complexes with H-NS and binds to a specific sequence in the replication origin of the E. coli chromosome. To understand the mechanism of interaction between Cnu and H-NS, we used bacterial genetics to select and analyze Cnu variants that cannot complex with H-NS. Out of 2,000 colonies, 40 Cnu variants were identified. Most variants (82.5%) had a single mutation, but a few variants (17.5%) had double amino acid changes. An in vitro assay was used to identify Cnu variants that were truly defective in H-NS binding. The changes in these defective variants occurred exclusively at charged amino acids (Asp, Glu, or Lys) on the surface of the protein. We propose that the attractive force that governs the Cnu-H-NS interaction is an ionic bond, unlike the hydrophobic interaction that is the major attractive force in most proteins.     

Genome-Wide Characterization of Nonreference Transposons Reveals Evolutionary Propensities of Transposons in Soybean

Preferential accumulation of transposable elements (TEs), particularly long terminal repeat retrotransposons (LTR-RTs), in recombination-suppressed pericentromeric regions seems to be a general pattern of TE distribution in flowering plants. However, whether such a pattern was formed primarily by preferential TE insertions into pericentromeric regions or by selection against TE insertions into euchromatin remains obscure. We recently investigated TE insertions in 31 resequenced wild and cultivated soybean (Glycine max) genomes and detected 34,154 unique nonreference TE insertions mappable to the reference genome. Our data revealed consistent distribution patterns of the nonreference LTR-RT insertions and those present in the reference genome, whereas the distribution patterns of the nonreference DNA TE insertions and the accumulated ones were significantly different. The densities of the nonreference LTR-RT insertions were found to negatively correlate with the rates of local genetic recombination, but no significant correlation between the densities of nonreference DNA TE insertions and the rates of local genetic recombination was detected. These observations suggest that distinct insertional preferences were primary factors that resulted in different levels of effectiveness of purifying selection, perhaps as an effect of local genomic features, such as recombination rates and gene densities that reshaped the distribution patterns of LTR-RTs and DNA TEs in soybean.     

Chitosan oligomers as drug carriers for renal delivery of zidovudine

Chitosan oligomers (COS) are water soluble and can be a potential drug carrier for renal targeting delivery. Zidovudine (AZT), a FDA approved antiretroviral drug, has a very short half life and is eliminated very quickly in human plasma and kidney after administration. In this study, AZT-COS conjugates were prepared and evaluated in terms of renal targeting. The in vitro release of AZT from AZT-COS conjugates was confirmed in mice plasma and renal homogenate. The pharmacokinetics study indicated longer mean retention time of AZT-COS conjugates with the values of about 1.5 h than 0.59 h of AZT. The AZT-COS conjugates were found accumulated in kidney other than heart, liver, spleen, lung and brain after i.v. administration, in line with the evidence of the fluorescence imaging of FITC labeled COS in 12 h. In conclusion, AZT-COS conjugates have the potential to be developed into a renal-targeting drug delivery system.     

Osteopontin's colocalization with the adhesion molecule CEACAM5 in cytoplasm of carcinoma of tongue and its correlation with the invasion of that diease

ABSTRACT: The purpose of this study was to investigate the expression of carcinoembryonic antigenrelated cell adhesion molecule 5 (CEACAM5) and correlate it with OPN expression and function in squamous carcinoma of tongue. Paraffin were sections of 80 samples with squamous carcinoma of tongue and 40 samples with normal tissue of tongue for benign lesion having undergone surgery. Immunohistochemistry (IHC) was used to study the distribution of CEACAM5 and OPN, and double-labeling immunohistochemistry was used to observe the relationship between CEACAM5 and OPN expression. CEACAM5 and OPN are found in normal tissue of tongue, but with different expression pattern. CEACAM5 expression mainly with membranous staining is restricted on the superficial epithelium. However, OPN expression with mainly cytoplasmic staining is restricted on the deep epithelium. No colocalization of CEACAM5 and OPN have been observed in normal tissue of tongue. In squamous carcinoma of tongue, CEACAM5 expression with cytoplasmic staining is different from normal tongue tissue with membranous staining, and the transformation of CEACAM5 distribution from membrane to cytoplasm is an important incident for the invasion and differentiation of tumor. CEACAM5 and OPN are colocalized in cytoplasm, and a significant correlation was observed between the positive colocalization and the negative colocalization in the depth of invasion and the differentiation of the tumor.     

Structural Understanding of the Glutathione-dependent Reduction Mechanism of Glutathionyl-Hydroquinone Reductases

Glutathionyl-hydroquinone reductases (GS- HQRs) are a newly identified group of glutathione transferases, and they are widely distributed in bacteria, halobacteria, fungi, and plants. GS-HQRs catalyze glutathione (GSH)-dependent reduction of glutathionyl-hydroquinones (GS-hydroquinones) to hydroquinones. GS-hydroquinones can be spontaneously formed from benzoquinones reacting with reduced GSH via Michael addition, and GS-HQRs convert the conjugates to hydroquinones. In this report we have determined the structures of two bacterial GS-HQRs, PcpF of Sphingobium chlorophenolicum and YqjG of Escherichia coli. The two structures and the previously reported structure of a fungal GS-HQR shared many features and displayed complete conservation for all the critical residues. Furthermore, we obtained the binary complex structures with GS-menadione, which in its reduced form, GS-menadiol, is a substrate. The structure revealed a large H-site that could accommodate various substituted hydroquinones and a hydrogen network of three Tyr residues that could provide the proton for reductive deglutathionylation. Mutation of the Tyr residues and the position of two GSH molecules confirmed the proposed mechanism of GS-HQRs. The conservation of GS-HQRs across bacteria, halobacteria, fungi, and plants potentiates the physiological role of these enzymes in quinone metabolism.     

Lipid metabolism and Drosophila sperm development

Lipids are essential membrane structural components and important signal carriers. The major enzymatic metabolisms of various lipids (phospholipid, sphingolipid, cholesterol) are well studied. The developmental function of lipid metabolism has remained, for the most part, elusive. With the help of new techniques and model organisms, the important roles of lipid metabolism in development just start to emerge. Drosophila spermatogenesis is an ideal system for in vivo studies of cytokinesis and membrane remodeling during development. The metabolic regulators of many lipids, including phosphatidylinositol (PI) lipids, fatty acids and cholesterol, are reported to play critical roles in various steps during Drosophila spermatogenesis. In this mini-review, we summarized recent findings supporting a tight link between lipids metabolism and Drosophila sperm development.