Polycomb group genes as the key regulators in gene silencing

The Polycomb group （PcG） genes repress gene expression mainly through chromatin modifications and regulation of chromatin structure. At present, at/east four protein complexes of PcG proteins are identified, including Polycomb repressive complex 1 （PRC1）, Polycomb repressive complex 2 （PRC2）, PHO-repressive complex （PhoRC） and Polycomb repressive deubiquitinase （PR-DUB）. In this review, the recent discoveries of the composition of the above complexes, as well as their roles in regulating histone modifications and gene silencing are discussed. We mainly focus on the composition of PRC1 and PRC2 complex and recruitment of PcG to target genes and mechanisms of PRC1 and PRC2-mediated gene silencing. Although much progress has been made in understanding gene silencing mediated by PcG proteins, we also discuss several important questions that still remained unanswered, such as the inheritance of histone modifications during cell division.     

顶坛花椒营养成分及微量元素测试研究

报道了顶坛花椒 (Zanthoxyhum planispinumvar .dingtanensis)果实营养成分分析结果。结果表明该变种含有丰富的芳香油和脂肪酸 ,特别是脂肪酸中不饱和脂肪酸含量极高 ,果实中蛋白质含有人体必需的 8种氨基酸、以及维生素E和生命元素等等 ,表明顶坛花椒是一种养分丰富的优良花椒品种 ,应大力开发利用     

Novel submicroscopic extrachromosomal elements containing amplified genes in human cells

In previous work, several methotrexate (MTX)-resistant variants were isolated frm the human cell line HeLa BU25, which exhibited a high degree of dihydrofolate (DHFR) gene amplification (estimated to be 250- to 300-fold). These variants did not contain any chromosome with a homogeneously staining region (HSR) and exhibited only a small average number of minute chromosomes per cell: these two types of karyotypic abnormalities generally accompany selective gene amplification. We now report that structures containing amplified DHFR genes in one of these variants (HeLa BU25-10B3) can be isolated by pulsed-field gradient or field-inversion gel electrophoresis as homogeneous DNA molecules of approximately 650 kilobases (kb). Electron microscopy of metaphase spreads from these cells reveals chromatin fibres with a similar DNA content, which are probably related to the above elements. These represent a novel type of extrachromosomal structures in mammalian cells.     

利用TRV过表达和沉默系统验证植物油脂合成相关基因的功能

为探究烟草脆裂病毒过表达和沉默系统进行油脂相关基因研究的可能性,该研究克隆了拟南芥的WRI1和FAD2基因,分别构建了TRV过表达和沉默载体. 利用瞬时侵染技术侵染本氏烟草,取材料进行RT-PCR和脂肪酸含量检测. 结果显示在过表达WRI1基因的本氏烟草中,侵染叶和非侵染叶的WRI1基因及其相关参与脂肪酸合成基因ACP1、KAS1和BCCP2等都有明显上调,且脂肪酸含量检测结果显示分别增加16%和28%. 在沉默FDA2基因的本氏烟草植株中,发现多不饱和脂肪酸含量分别减少约25%和24%. 因此,利用TRV系统对油脂相关基因进行研究是可能的.     

Malaria in 2002

The burden of malaria is increasing, especially in sub-Saharan Africa, because of drug and insecticide resistance and social and environmental changes. Thus, there is an urgent need for vaccines, new drugs and insecticides. Parasite, mosquito and human genome projects are helping in the search for new control tools and international donors are developing new funding mechanisms that could make them available to poor countries. But these new tools will achieve their maximum impact only if additional resources are deployed to strengthen malaria research and control communities in countries where the new tools will be used.