Dynamic DNA Shortening by Telomere-Binding Protein Cdc13.

Telomeres are essential for chromosome maintenance. Cdc13 is a single-stranded telomeric DNA binding protein that caps telomeres and regulates telomerase function in yeast. Although specific binding of Cdc13 to telomeric DNA is critical for telomere protection, the detail mechanism how Cdc13-DNA complex protects telomere is unclear. Using two single-molecule methods, tethered particle motion and atomic force microscopy, we demonstrate that specific binding of Cdc13 on single-stranded telomeric DNA shortens duplex DNA into distinct states differed by ∼70-80 base pairs. DNA shortening by Cdc13 is dynamic and independent of duplex DNA sequences or length. Significantly, we found that Pif1 helicase is incapable of removing Cdc13 from the shortened DNA-Cdc13 complex, suggesting that Cdc13 forms structurally stable complex by shortening of the bound DNA. Together our data identified shortening of DNA by Cdc13 and provided an indication for efficient protection of telomere ends by the shortened DNA-Cdc13 complex.

[Mechanism of Inorganic Nitrogen Transformation and Identification of Nitrogen Sources in Water and Soil].

Nitrogen plays a vital role in biological activities as the basic element of organic molecules and the main nutrient of soil. In the study of nitrogen pollution, the first step is to understand the transformation mechanism of various nitrogen forms. Based on the transformation process and the mechanism of nitrogen in the ecosystem, this review summarizes the research methods of nitrogen source analysis and nitrogen isotope fractionation in soil and water, and categorically reviews the applications of nitrogen source identification in surface water and groundwater. We showed that it is more effective to identify the sources of soil and water nitrogen pollution by combining hydrochemical methods with the multi-isotope approach. The importance of primary nitrogen sources should also be quantified to study groundwater pollution. A new approach to determine the source of oxygen atoms during nitrosation was also presented, and the enrichment principle of δ18O-NO3- during secondary oxidation was explained. Finally, the contribution of primary ammonium nitrogen to groundwater pollution was discussed, and innovative research ideas were provided.

[Effects and mechanism of hypoxia exposure on related genes in brown fat tissue of obese mice based on mRNA expression profile microarray].

OBJECTIVE: This study intended to screen differentially expressed genes and pathways in Brown Adipose Tissue (BAT) of obese mice after the intervention of hypoxia by mRNA expression profile microarray, exploring the mechanism of hypoxia activated BAT. METHODS: Thirty C57BL/6J male mice were divided into the normal diet control group (N, n=8), high-fat diet control group (OB, n=8) and high-fat diet hypoxia group (H, n=8). Group H was intervened by hypoxia exposure in the oxygen concentration of 11.2% of the normal oxygen and hypoxia for 8 h/d, 6 d/w of 4 weeks. Blood lipid and blood glucose were detected after intervention; RNA microarray scan and bioinformation analysis were done of BAT from scapula. Genes significantly (P ≤ 0.05) regulated more than 1.5 fold were chosen to do Gene Ontology and enrichment analysis by KOBAS 2.0, and confirmation of genes participating in key biological process (BP) and pathway was done by real time qPCR. RESULTS: After intervention, the body weight and blood lipid and glucose levels in group H were significantly lower than those of group OB. Comparing with group N, 802 genes were significantly up-regulated and 1 175genes were down-regulated. The BP of these genes mainly concerned with glucose and lipid metabolic process and inflammatory reaction. Comparing with group OB, 297 genes were significantly up-regulated and 228 genes were down-regulated. These genes participated in glucose and lipid metabolic process, lipid transport, muscle system process and cardiovascular system development. The pathways of regulating BAT by hypoxia exposure mainly concentrated on the HIF-1, PI3K-AKT, FoxO and ErbB signaling pathways. CONCLUSIONS: A series of genes and pathways in BAT could be adjusted by hypoxia exposure, so that hypoxia could improve the activity of BAT, promoting obese organism to lose weight.

[Multilevel regression analysis on region cluster and risk factors of hypertension in the Chinese adult population].

OBJECTIVE: To analyze the region cluster and risk factors of hypertension in the Chinese adult population and to explore the application of multilevel regression model in the risk factors of hypertension. METHODS: Multi-stage random sampling technique was used to choose 15,540 individuals aged 35-74 years from 10 regions in China. Two-level logistic regression models were fitted under MLwiN 2.02 software. RESULTS: The region cluster of hypertension existed and variance portion coefficient was 3.1%. After adjusting for the age and gender, overall obese people (BMI> or =28 kg/m2) were 4.50 (95% CI: 4.00-5.06) times, overweight people (BMI=24-27.9 kg/m2) were 2.26 (95% CI: 2.07-2.46) times more likely to be hypertensive as compared with those of normal BMI (18.5-23.9 kg/m2), and those centrally obesive people (Waist circumference > or =85 cm in male or 80 cm in female) were 2.62 (95% CI: 2.42-2.83) times more likely to be hypertensive as compared with those of normal WC. The age-and gender-adjusted odds ratios (ORs) of triglyceride (TG), serum total cholesterol (TC), glucose, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and drinking alcohol were 2.10 (95% CI: 1.89-2.33), 2.08 (95% CI: 1.84-2.35), 1.85 (95% CI: 1.60-2.14), 1.58 (95% CI: 1.38-1.81), 1.49 (95% CI: 1.32-1.69) and 1.15 (95% CI: 1.05-1.27), respectively. CONCLUSION: The prevalence of hypertension was not only affected by individual risk factors, such as obesity, drinking alcohol, abnormal glucose and serum lipids profile, but also affected by the geographic environment where people resided in. Population-and risk factors targeted strategies, proved a promising way to reduce individual risk of hypertension in the primary prevention of hypertension.