mTORC1-independent translation control in mammalian cells by methionine adenosyltransferase 2A and S-adenosylmethionine

Methionine adenosyltransferase (MAT) catalyzes the synthesis of S-adenosylmethionine (SAM). As the sole methyl-donor for methylation of DNA, RNA, and proteins, SAM levels affect gene expression by changing methylation patterns. Expression of MAT2A, the catalytic subunit of isozyme MAT2, is positively correlated with proliferation of cancer cells; however, how MAT2A promotes cell proliferation is largely unknown. Given that the protein synthesis is induced in proliferating cells and that RNA and protein components of translation machinery are methylated, we tested here whether MAT2 and SAM are coupled with protein synthesis. By measuring ongoing protein translation via puromycin labeling, we revealed that MAT2A depletion or chemical inhibition reduced protein synthesis in HeLa and Hepa1 cells. Furthermore, overexpression of MAT2A enhanced protein synthesis, indicating that SAM is limiting under normal culture conditions. In addition, MAT2 inhibition did not accompany reduction in mechanistic target of rapamycin complex 1 activity but nevertheless reduced polysome formation. Polysome-bound RNA sequencing revealed that MAT2 inhibition decreased translation efficiency of some fraction of mRNAs. MAT2A was also found to interact with the proteins involved in rRNA processing and ribosome biogenesis; depletion or inhibition of MAT2 reduced 18S rRNA processing. Finally, quantitative mass spectrometry revealed that some translation factors were dynamically methylated in response to the activity of MAT2A. These observations suggest that cells possess an mTOR-independent regulatory mechanism that tunes translation in response to the levels of SAM. Such a system may acclimate cells for survival when SAM synthesis is reduced, whereas it may support proliferation when SAM is sufficient.     

Genetic Variability of PRNP in Chinese Indigenous Goats

Polymorphism of the prion protein gene (PRNP) is usually associated with scrapie susceptibility or resistance. To determine the variability of PRNP in Chinese indigenous goat breeds, we isolated genomic DNA from goat blood and amplified and sequenced the coding region of the gene. We identified 10 polymorphic sites that gave rise to 28 haplotypes. Clear frequency differences were found between northern and southern breeds and confirmed by genetic distance analysis, except for the Tangshan dairy goat. Phylogeographic analysis supported the idea that northern and southern breeds might be considered separate clusters, except for the Tangshan dairy goat. The finding of significant differences in allele distribution in northern and southern goats, especially if involved in modulating resistance/susceptibility, needs to be carefully considered for the feasibility of selection plans for resistance to scrapie.     

Invasive alien plant species in China: regional distribution patterns

Plant invasions have been attracting increasing attention from ecologists because of their worldwide environmental impacts and huge economic costs. Research on the characteristics of the recipient regions is essential for understanding the process of plant invasion. However, few previous studies on invasibility of habitats include social factors, although human activities are critical in the process of plant invasion. China is a vast country with high plant species diversity and a long history of introduction of exotic plant species and is particularly vulnerable to invasive plant species. Alien plant species are widespread in the country. Therefore, the study of invasive plants in China is urgent in practice and theoretically important for developing invasion ecology. For the present study, 126 species were selected to represent the major invasive plant species in China. We then collected data on their species richness in 31 provincial administrative units of China and performed Spearman rank correlations between species richness and possible natural and socio‐economic factors. We found that socio‐economic factors, such as human density and GDP, correlated positively with the species richness of invasive plants in China. In conjunction with the natural and socio‐economic correlations in the study of regional distribution pattern of the major invasive plants, we discussed the factors influencing the regional distribution pattern of the major invasive plants in China. We suggest that native plant species richness was mainly determined by the natural conditions of the regions, while invasive species richness was influenced by natural conditions and human disturbance together.     

Inhibition of Filamin-A Reduces Cancer Metastatic Potential

Filamin-A cross-links actin filaments into dynamic orthogonal networks, and interacts with an array of proteins of diverse cellular functions. Because several filamin-A interaction partners are implicated in signaling of cell mobility regulation, we tested the hypothesis that filamin-A plays a role in cancer metastasis. Using four pairs of filamin-A proficient and deficient isogenic cell lines, we found that filamin-A deficiency in cancer cells significantly reduces their migration and invasion. Using a xenograft tumor model with subcutaneous and intracardiac injections of tumor cells, we found that the filamin-A deficiency causes significant reduction of lung, splenic and systemic metastasis in nude mice. We evaluated the expression of filamin-A in breast cancer tissues by immunohistochemical staining, and found that low levels of filamin-A expression in cancer cells of the tumor tissues are associated with a better distant metastasis-free survival than those with normal levels of filamin-A. These data not only validate filamin-A as a prognostic marker for cancer metastasis, but also suggest that inhibition of filamin-A in cancer cells may reduce metastasis and that filamin-A can be used as a therapeutic target for filamin-A positive cancer.     

Pattern recognition analysis to the variation of nasal-pharynx cancer patients' trace element levels in samples of hair,whole blood,and tissue

Pattern recognition has been used in this paper to analyze trace element levels in patients diagnosed with nasal-pharynx cancer (NPC) and in healthy control subjects. Trace elements such as Zn, Cu, Fe, Mn, and Mg have been tested in samples of hair and whole blood. Through Mahalanobis Distance Decision analysis, we have achieved good classification effects in whole blood samples: Efficiency for distinguishing patients is 96% and that of healthy controls is 90%. Classification hair samples is inferior to whole blood: Decision accuracy for patients is 58% and healthy controls is 90%. These results are also shown in a nonlinear mapping figure. At the same time, we have also determined 5 trace element levels in 16 other cancer patients' nonneoplastic and cancerous tissue, with no significant difference between them: Decision accuracy of cancerous tissue is 63%, and in nonneoplastic tissue is 50%, hence, we cannot identify them. It can be inferred that there is no idiosyncratic change of trace elements in cancer patients' neoplastic tissue, the change of a cancerous person may occur in the whole body.     

极端酶的研究进展

极端酶具有超常的生物学稳定性,能够在极端温度、pH、压力和离子强度下表现出生物学活性,因此极端酶为生物催化和生物转化提供了良机.新的极端物种的发现、基因组序列的确定及基因工程技术的应用,加快了发现和制备新酶的进程.蛋白质工程和定向进化技术进一步改善酶的活性和特异性,促进了极端酶的工业应用.对极端酶的研究加深了人们对酶稳定性机制的理解,丰富了分子进化理论.     

海藻多糖抑制白细胞呼吸爆发作用研究

采用ESR、自旋捕集及自旋氧探针技术,研究了海藻硫酸多糖(SPS)对豆蔻酰佛波醇乙酯(PMA)刺激的多形核白细胞(PMN)呼吸爆发的影响.结果表明,SPS能显著抑制PMN呼吸爆发,10 g/L和5 g/L SPS几乎完全清除PMN呼吸爆发产生的自由基,1 g/L SPS可清除53.2%;10 g/L SPS对PMN的耗氧量也有较明显的抑制作用.     

The role of LXRα in goose primary hepatocyte lipogenesis

In this study, we investigate the role of liver X receptor alpha (LXR alpha) in lipogenesis in geese in order to understand the differences in hepatic steatosis mechanisms between mammals and waterfowl. Primary goose hepatocytes were isolated and treated with the LXR alpha agonist T0901317. Triglyceride (TG) accumulation, acetyl-CoA carboxylase alpha (ACC alpha) and fatty acid synthase (FAS) activities, and gene expression levels of LXR alpha, sterol regulatory element-binding proteins-1 (SREBP-1), FAS, ACC alpha and lipoprotein lipase (LPL) were measured in primary hepatocytes. We found a dose-dependent up-regulation of TG accumulation, ACC, and FAS activities and the mRNA levels of LXR alpha, SREBP-1, FAS, ACC alpha, and LPL genes in the presence of To-901317. We also found that binding of nuclear SREBP-1 to ACC alpha SRE sequence was induced by To-901317 (P < 0.05). In conclusion, LXR alpha is involved in the induction of the lipogenic pathway through activation of SREBP-1 and its target genes in goose primary hepatocytes.     

北京城市生态占水研究

在前人研究的基础上,提出了生态占水的概念及计算方法,构建了生态占水驱动因素分析模型,计算各因素对生态占水变动的贡献率,并采用灰色关联分析法对生态占水-水生态因子进行关联分析。以北京市为例计算1999-2009年的生态占水量,结果显示水量型占水和水质型占水均呈现波动式逐年下降趋势,分别由1999年的25.56亿m³和12.55亿m³减少到2009年的15.65亿m³和4.58亿m³;2003-2005年北京市生态占水率明显高于其它时期,达到80%以上,2006年以后逐步下降,但仍然高于50%;水量型占水是过去10 a中最主要的占水类型。生态占水驱动因素分析结果得出,1999-2009年的总体变动中人均消费水平的提高是促使北京市生态占水增加的关键驱动因素,其次是第二产业增加值。占水-水生态因子关联分析显示,地表取水和污水处理率两个因素与水生境因子的变化有着较强的关联性;退水和地下取水与水环境因子有较强的关联性,地下水埋深和人口两大因素与水安全有着较强的关联性。