What is Unique About Superoxide Toxicity as Compared to Other Biological Reductants? — A Hypothesis

Usually the toxicity of superoxide is attributed lo its ability to reduce metal ions and subsequently reoxidation of the metal by hydrogen peroxide yields deleterious oxidizing species. As many other nontoxic biological reductants reduce metal compounds, we suggest that part of the mechanism of superoxide toxicity results from its ability to oxidize metal ions bound to biological targets, which subsequently degrade the target via an intramolecular electron Transfer reaction.     

Functional and molecular analysis of the double-positive stage-specific CD8 enhancer E8III during thymocyte development

Several developmental stage-, subset-, and lineage-specific Cd8 cis-regulatory regions have been identified. These include the E8(III) enhancer, which directs expression in double-positive (DP) thymocytes, and E8(II), which is active in DP cells and CD8(+) T cells. Using a transgenic reporter expression assay, we identified a 285-bp core fragment of the E8(III) enhancer that retains activity in DP thymocytes. In vitro characterization of the core enhancer revealed five regulatory elements that are required for full enhancer activity, suggesting that multiple factors contribute to the developmental stage-specific activity. Furthermore, deletion of E8(III) in the mouse germline showed that this enhancer is required for nonvariegated expression of CD8 in DP thymocytes when E8(II) is also deleted. These results indicate that E8(III) is one of the cis-elements that contribute to the activation of the Cd8a and Cd8b gene complex during T cell development.     

Characterization of E3Histone, a novel testis ubiquitin protein ligase which ubiquitinates histones

During spermatogenesis, a large fraction of cellular proteins is degraded as the spermatids evolve to their elongated mature forms. In particular, histones must be degraded in early elongating spermatids to permit chromatin condensation. Our laboratory previously demonstrated the activation of ubiquitin conjugation during spermatogenesis. This activation is dependent on the ubiquitin-conjugating enzyme (E2) UBC4, and a testis-particular isoform, UBC4-testis, is induced when histones are degraded. Therefore, we tested whether there are UBC4-dependent ubiquitin protein ligases (E3s) that can ubiquitinate histones. Indeed, a novel enzyme, E3Histone, which could conjugate ubiquitin to histones H1, H2A, H2B, H3, and H4 in vitro, was found. Only the UBC4/UBC5 family of E2s supported E3Histone-dependent ubiquitination of histone H2A, and of this family, UBC4-1 and UBC4-testis are the preferred E2s. We purified this ligase activity 3,600-fold to near homogeneity. Mass spectrometry of the final material revealed the presence of a 482-kDa HECT domain-containing protein, which was previously named LASU1. Anti-LASU1 antibodies immunodepleted E3Histone activity. Mass spectrometry and size analysis by gel filtration and glycerol gradient centrifugation suggested that E3Histone is a monomer of LASU1. Our assays also show that this enzyme is the major UBC4-1-dependent histone-ubiquitinating E3. E3Histone is therefore a HECT domain E3 that likely plays an important role in the chromatin condensation that occurs during spermatid maturation.     

家蚕非编码RNA在神经系统中的表达分析

【目的】非编码RNA(non-coding RNA,ncRNA)在家蚕Bombyx mori发育过程中具有重要调控作用。本研究旨在探索ncRNA参与家蚕神经系统发育的分子机理。【方法】采用实时荧光定量PCR技术对22个中等长度的ncRNA及3个ncRNA的邻近编码基因在家蚕幼虫神经系统中的表达水平进行检测。【结果】8个ncRNA(包括1个C/D box snoRNA,4个H/ACA box snoRNA和3个不能归类的ncRNA)在家蚕5龄幼虫神经组织和非神经组织中均有表达,且在胸腹神经中的表达量明显高于头部神经中的表达量。其中,snoRNA Bm-51,Bm-18和Bm-86在胸腹神经中的表达量分别是头部神经中的23,5和4.7倍。进一步研究发现,这3个内含子起源的ncRNA与其宿主基因在家蚕神经系统中的表达趋势一致,宿主基因在胸腹神经中的表达量也明显高于头部神经中的表达量。【结论】本研究筛选到的在家蚕不同神经部位存在差异表达的ncRNA,特别是在胸腹神经中高表达的ncRNA可能协同其邻近编码基因,参与家蚕神经发育或神经活动过程。该结果为研究ncRNA参与家蚕神经系统发育提供了分子依据,为从非编码RNA角度探索鳞翅目害虫防治提供了新的思路。     

东海低氧区及邻近水域浮游植物的季节变化

根据2011年5月、8月、11月在东海低氧区及邻近水域(25°00'—33°30'N,120°00'—127°30'E)进行的多学科综合调查,对东海低氧区及邻近水域浮游植物群落结构特征及季节变化进行了相关研究。经Utermhl方法初步分析共鉴定出浮游植物4门74属248种(含变种、变型,不含未定种),主要由硅藻和甲藻组成,此外还有少量的金藻和蓝藻。春季优势种主要为具齿原甲藻(Prorocentrum dentatum)、柔弱伪菱形藻(Pseudo-nitzschia delicatissim)、骨条藻(Skeletonema sp.)和具槽帕拉藻(Paralia sulcata);夏季主要是中肋骨条藻(Skeletonema costatum)和海链藻(Thalassiosira sp.);秋季主要是具槽帕拉藻、圆筛藻(Coscinodiscus sp.)和柔弱伪菱形藻。调查区浮游植物平均细胞丰度在夏季最高,达到85.002×103个/L,春季次之,秋季最低。在水平方向上,春、夏两季,表层浮游植物细胞丰度在近岸出现高值,由近岸到外海细胞丰度逐渐降低;而在秋季则相反,在调查海域的东北部出现高值,随离岸距离的增加细胞丰度逐渐增加。在垂直方向上,春、夏两季,浮游植物细胞丰度在表层出现最大值,随着深度的增加细胞丰度逐渐降低;而在秋季细胞丰度分布比较均匀,随水深变化不明显。调查区表层浮游植物ShannonWiener多样性指数和Pielou均匀度指数的平面分布基本一致,并且与细胞丰度的分布大致呈镶嵌分布。调查浮游植物群落的演替规律是:从春季的甲藻(具齿原甲藻、微小原甲藻(Prorocentrum minimum)等)为主,硅藻(柔弱伪菱形藻、骨条藻等)为辅;演替至夏季的硅藻(中肋骨条藻、海链藻等)为主,甲藻(主要是梭状角藻(Ceratium fusus)和叉状角藻(Ceratium furca))为辅,到秋季进一步演替为硅藻(具槽帕拉藻、圆筛藻、柔弱伪菱形藻等)为主,铁氏束毛藻(Trichodesmium thiebaultii)为辅。浮游植物物种组成、优势种、细胞丰度及多样性指数均表现出明显的时空变化。低氧区与非低氧区浮游植物群集存在明显差异。