microRNA‐124 inhibits stem‐like properties and enhances radiosensitivity in nasopharyngeal carcinoma cells via direct repression of expression of JAMA

Cancer stem cells (CSCs) are a source of tumour recurrence in patients with nasopharyngeal carcinoma (NPC); however, the function of microRNA‐124 (miR‐124) in NPC CSCs has not been clearly defined. In this study, we investigated the role of miR‐124 in NPC CSCs. qRT‐PCR was performed to measure miR‐124 expression in NPC tissues and cell lines and the effects of miR‐124 on stem‐like properties and radiosensitivity of NPC cells measured. Luciferase reporter assays and rescue experiments were used to investigate the interaction of miR‐124 with the 3′UTR of junctional adhesion molecule A (JAMA). Finally, we examined the effects of miR‐124 in an animal model and clinical samples. Down‐regulation of miR‐124 was detected in cancer tissues and was inversely associated with tumour stage and lymph node metastasis. Overexpression of miR‐124 inhibited stemness properties and enhanced radiosensitivity of NPC cells in vitro and in vivo via targeting JAMA. Up‐regulation of miR‐124 was correlated with superior overall survival of patients with NPC. Our study demonstrates that miR‐124 can inhibit stem‐like properties and enhance radiosensitivity by directly targeting JAMA in NPC. These findings provide novel insights into the molecular mechanisms underlying therapy failure in NPC.     

北柴胡分泌道的超微结构及其挥发油分泌的研究

利用透射电子显微镜技术研究了北柴胡营养器官中分泌道的发育以及挥发油的积累.并重点探讨了挥发油的分泌机制.结果显示.分泌道细胞的质体、细胞基质以及线粒体参与挥发油或其前体物质的合成,而内质网参与挥发油向分泌道腔隙的转运.在分泌道发育的后期,大量小泡与分泌细胞相邻壁的质膜融合,并将其内的物质释放入此部分细胞壁中,与此同时,此部分壁在靠近腔隙的位置结构变得松散.然后围绕腔隙的壁在相邻两分泌细胞相接的位置面向腔隙外突形成许多小泡,并将小泡释放入腔隙中.由此可见.北柴胡分泌道中挥发油主要以胞吐方式被排入分泌道的腔隙中.     

双碳源单细胞蛋白间歇培养及流加培养的动力学模型

应用非结构的逻辑增殖模型研究了两种酵母的单碳源和双碳源单细胞蛋白间歇培养的动力学,用改进的逻辑增殖模型研究了双碳源流加培养过程的动力学,从实验数据拟合了动力学模型参数,模型计算值与实验数据吻合良好。     

The F-box protein SKP2 binds to the phosphorylated threonine 380 in cyclin E and regulates ubiquitin-dependent degradation of cyclin E

Cyclin E is required for S phase entry. The subsequent ubiquitin-dependent degradation of cyclin E contributes to an orderly progression of the S phase. It has been shown that phosphorylation of threonine 380 (Thr380) in cyclin E provides a signal for its ubiquitin-dependent proteolysis. We report that SKP2, an F-box protein and a substrate-targeting component of the SCF(SKP2) ubiquitin E3 ligase complex, mediates cyclin E degradation. In vitro, SKP2 specifically interacted with the cyclin E peptide containing the phosphorylated-Thr380 but not with a cognate nonphosphorylated peptide. In vivo, expression of SKP2 induced cyclin E polyubiquitination and degradation. Conversion of Thr380 into nonphosphorylatable amino acids caused significant resistance of cyclin E to SKP2. The presence of the CDK inhibitor p27(Kip1) also prevented the SKP2-dependent degradation of cyclin E. Our findings suggest that SKP2 regulates cyclin E stability, thus contributing to the control of S phase progression.     

The death effector domain-associated factor plays distinct regulatory roles in the nucleus and cytoplasm

Homophilic interactions of death effector domains (DEDs) are crucial for the signaling pathways of death receptor-mediated apoptosis. The machinery that regulates proper oligomerization and autoactivation of procaspase-8 and/or procaspase-10 during T lymphocyte activation determines whether the cells will undergo caspase-mediated apoptosis or proliferation. We screened a yeast two-hybrid library by using the DEDs contained in the prodomains of procaspase-8 and procaspase-10 and isolated a DED-associated factor (DEDAF) that interacts with several DED-containing proteins but does not itself contain a DED. DEDAF is highly conserved between human and mouse (98% amino acid identity) and is homologous to a nuclear regulatory protein YAF-2. DEDAF is expressed at the highest levels in lymphoid tissues and placenta. DEDAF interacts with FADD, procaspase-8, and procaspase-10 in the cytosol as well as with the DED-containing DNA-binding protein (DEDD) in the nucleus. At the cell membrane, DEDAF augmented the formation of CD95-FADD-caspase-8 complexes and enhanced death receptor- as well as DED-mediated apoptosis. In the nucleus, DEDAF caused the DEDD protein to relocalize from subnuclear structures to a diffuse distribution in the nucleoplasm. Our data therefore suggest that DEDAF may be involved in the regulation of both cytoplasmic and nuclear events of apoptosis.     

Construction of acetate auxotrophs of Neisseria meningitidis to study host-meningococcal endotoxin interactions

To facilitate studies of the molecular determinants of host-meningococcal lipooligosaccharide (endotoxin) interactions at patho-physiologically relevant endotoxin concentrations (i.e. < or =10 ng/ml), we have generated acetate auxotrophs NMBACE1 from encapsulated Neisseria meningitidis (serogroup B, strain NMB) and NMBACE2 from an isogenic bacterial mutant lacking the polysialic acid capsule. Growth of the auxotrophs in medium containing [(14)C]acetate yielded (14)C-lipooligosaccharides containing approximately 600 cpm/ng. Gel sieving resolved 14C-lipooligosaccharide-containing aggregates with an estimated molecular mass of > or =20 x 10(6) Da (peak A) and approximately 1 x 10(6) Da (peak B) from both strains. Lipooligosaccharides in peaks A and B had the same fatty acid composition and SDS-polyacrylamide gel electrophoresis profile. 14C-Labeled capsule copurified with (14)C-lipooligosaccharides in peak B from NMBACE1, whereas the other aggregates contained only 14C-lipooligosaccharide. For all aggregates, lipopolysaccharide-binding protein and soluble CD14-induced delivery of lipooligosaccharides to endothelial cells and cell activation correlated with disaggregation of lipooligosaccharides. These processes were inhibited by the presence of capsule but unaffected by the size of the aggregates. In contrast, endotoxin activation of cells containing membrane CD14 was unaffected by capsule but diminished when endotoxin was presented in larger aggregates. These findings demonstrate that the physical presentation of lipooligosaccharide, including possible interactions with capsule, affect the ability of meningococcal endotoxin to interact with and activate specific host targets.