MiR-18a regulates the proliferation,migration and invasion of human glioblastoma cell by targeting neogenin

MiR-17-92 cluster has recently been reported as an oncogene in some tumors. However, the association of miR-18a, an important member of this cluster, with glioblastoma remains unknown. Therefore, this study aims to investigate the expression of miR-18a in glioblastoma and its role in biological behavior of U87 and U251 human glioblastoma cell lines. Quantitative RT-PCR results showed that miR-18a was highly expressed in glioblastoma tissues and U87 and U251 cell lines compared with that in human brain tissues and primary normal human astrocytes, and the expression levels were increased along with the rising pathological grades of glioblastoma. Neogenin was identified as the target gene of miR-18a by dual-luciferase reporter assays. RT-PCR and western blot results showed that its expression levels were decreased along with the rising pathological grades of glioblastoma. Inhibition of miR-18a expression was established by transfecting exogenous miR-18a inhibitor into U87 and U251 cells, and its effects on the biological behavior of glioblastoma cells were studied using CCK-8 assay, transwell assay and flow cytometry. Inhibition of miR-18a expression in U87 and U251 cells significantly up-regulated neogenin, and dramatically suppressed the abilities of cell proliferation, migration and invasion, induced cell cycle arrest and promoted cellular apoptosis. Collectively, these results suggest that miR-18a may regulate biological behavior of human glioblastoma cells by targeting neogenin, and miR-18a can serve as a potential target in the treatment of glioblastoma.     

Bayesian and Maximum Likelihood Analyses of Rotifer–Acanthocephalan Relationships

Rotifera is composed of groups with unusual ultrastructural, physiological, and reproductive characters. Our ability to understand the evolution of these features is complicated by the fact that the phylogenetic relationships among the three traditional rotifer groups (Seisonidea, Monogononta, and Bdelloidea) and Acanthocephala remain unresolved. Here, I present maximum likelihood and Bayesian analyses of rotifer–acanthocephalan relationships using both the protein-coding gene hsp82 and a combined data set of hsp82 and ribosomal small subunit (SSU) DNA sequences, using nucleotide and codon based models of evolution. Statistical analysis of the phylogenetic support for any of the likely relationships among rotifer groups suggests that more than a combined hsp82 + SSU data set will be needed to resolve rotifer–acanthocephalan phylogeny with any degree of certainty.     

The Sec1/Munc18 Protein Groove Plays a Conserved Role in Interaction with Sec9p/SNAP‐25

The Sec1/Munc18 (SM) proteins constitute a conserved family with essential functions in SNARE‐mediated membrane fusion. Recently, a new protein–protein interaction site in Sec1p, designated the groove, was proposed. Here, we show that a sec1 groove mutant yeast strain, sec1(w24), displays temperature‐sensitive growth and secretion defects. The yeast Sec1p and mammalian Munc18‐1 grooves were shown to play an important role in the interaction with the SNAREs Sec9p and SNAP‐25b, respectively. Incubation of SNAP‐25b with the Munc18‐1 groove mutant resulted in a lag in the kinetics of SNARE complex assembly in vitro when compared with wild‐type Munc18‐1. The SNARE regulator SRO7 was identified as a multicopy suppressor of sec1(w24) groove mutant and an intact Sec1p groove was required for the plasma membrane targeting of Sro7p–SNARE complexes. Simultaneous inactivation of Sec1p groove and SRO7 resulted in reduced levels of exocytic SNARE complexes. Our results identify the groove as a conserved interaction surface in SM proteins. The results indicate that this structural element is important for interactions with Sec9p/SNAP‐25 and participates, in concert with Sro7p, in the initial steps of SNARE complex assembly.      

Disruption of the Arabidopsis RAD50 gene leads to plant sterility and MMS sensitivity

The Rad50 protein is involved in the cellular response to DNA-double strand breaks (DSBs), including the detection of damage, activation of cell-cycle checkpoints, and DSB repair via recombination. It is essential for meiosis in yeast, is involved in telomere maintenance, and is essential for cellular viability in mice. Here we present the isolation, sequence and characterization of the Arabidopsis thaliana RAD50 homologue (AtRAD50) and an Arabidopsis mutant of this gene. A single copy of this gene is present in the Arabidopsis genome, located on chromosome II. Northern analysis shows a single 4.3 Kb mRNA species in all plant tissues tested, which is strongly enriched in flowers and other tissues with many dividing cells. The predicted protein presents strong conservation with the other known Rad50 homologues of the amino- and carboxy-terminal regions. Mutant plants present a sterility phenotype which co-segregates with the T-DNA insertion. Molecular analysis of the mutant plants shows that the sterility phenotype is present only in the plants homozygous for the T-DNA insertion. An in vitro mutant cell line, derived from the mutant plant, shows a clear hypersensitivity to the DNA-damaging agent methylmethane sulphonate, suggesting a role of RAD50 in double-strand break repair in plant cells. This is the first report of a plant mutated in a protein of the Rad50-Mre11-Xrs2 complex, as well as the first data suggesting the involvement of the Rad50 homologue protein in meiosis and DNA repair in plants.     

Involvement of HAb18G/CD147 in T cell activation and immunological synapse formation

HAb18G/CD147, a glycoprotein of the immunoglobulin super‐family (IgSF), is a T cell activation‐associated molecule. In this report, we demonstrated that HAb18G/CD147 expression on both activated CD4⁺ and CD8⁺ T cells was up‐regulated. In vitro cross‐linking of T cells with an anti‐HAb18G/CD147 monoclonal antibody (mAb) 5A12 inhibited T cells proliferation upon T cell receptor stimulation. Such co‐stimulation inhibited T cell proliferation by down‐regulating the expression of CD25 and interleukin‐2 (IL‐2), decreased production of IL‐4 but not interferon‐γ. Laser confocal imaging analysis indicated that HAb18G/CD147 was recruited to the immunological synapse (IS) during T cell activation; triggering HAb18G/CD147 on activated T cells by anti‐HAb18G/CD147 mAb 5A12 strongly dispersed the formation of the IS. Further functional studies showed that the ligation of HAb18G/CD147 with mAb 5A12 decreased the tyrosine phosphorylation and intracellular calcium mobilization levels of T cells. Through docking antibody–antigen interactions, we demonstrated that the function of mAb 5A12 is tightly dependent on its specificity of binding to N‐terminal domain I, which plays pivotal role in the oligomerization of HAb18G/CD147. Taken together, we provide evidence that HAb18G/CD147 could act as a co‐stimulatory receptor to negatively regulate T cell activation and is functionally linked to the formation of the IS.     

Mutation strategies for obtaining chitooligosaccharides with longer chains by transglycosylation reaction of family GH18 chitinase

Enhancing the transglycosylation (TG) activity of glycoside hydrolases does not always result in the production of oligosaccharides with longer chains, because the TG products are often decomposed into shorter oligosaccharides. Here, we investigated the mutation strategies for obtaining chitooligosaccharides with longer chains by means of TG reaction catalyzed by family GH18 chitinase A from Vibrio harveyi (VhChiA). HPLC analysis of the TG products from incubation of chitooligosaccharide substrates, GlcNAc_n, with several mutant VhChiAs suggested that mutant W570G (mutation of Trp570 to Gly) and mutant D392N (mutation of Asp392 to Asn) significantly enhanced TG activity, but the TG products were immediately hydrolyzed into shorter GlcNAc_n. On the other hand, the TG products obtained from mutants D313A and D313N (mutations of Asp313 to Ala and Asn, respectively) were not further hydrolyzed, leading to the accumulation of oligosaccharides with longer chains. The data obtained from the mutant VhChiAs suggested that mutations of Asp313, the middle aspartic acid residue of the DxDxE catalytic motif, to Ala and Asn are most effective for obtaining chitooligosaccharides with longer chains.     

双壳纲动物核糖体RNA 18S-ITS1序列及其在分子系统发育研究中的应用

测定了双壳纲不同科、属、种及种内共11个个体的核糖体RNA 18S-ITS1序列。结果表明,该序列在种间存在很高的多态性,长度从558bp到784bp不等,碱基差异百分比在10．7％～61．7％之间,ITS1序列同源性很低,有片段的插入与缺失。种间18S部分序列碱基差异百分比在0．9％～23．7％之间,变化主要是碱基的转换。用邻接法(NJ)构建了8个种的18S部分序列(约240bp)的系统发育树,与传统形态学分类结果相符。马氏珠母贝(Pinctada martrtensi)4个不同地域个体间的序列差异百分比在0．6％～1．9％之间。分析指出：18S基因可以作为双壳纲动物高阶元系统发育的分子标记;ITS1序列种间变化很大,可以应用于该纲物种的分类及鉴别．在亲缘关系相近种及种内变异相对较小,但核苷酸变异位点信息量丰富,可用于属内种间、亚种和群体间的遗传多样性研究。     

Enhanced expression of Hab18g/CD147 and activation of integrin pathway in HCC cells under 3-D co-culture conditions

CD147 is reported to be correlated with the malignancy of some cancers, and its overexpression affects the progression of tumor. In the present study, we investigated the function of HAb18G/CD147, a member of CD147 family, on hepatocellular carcinoma (HCC) adhesion, invasion and metastasis in 3-dimensional (3-D) cell co-culture model. The results showed that the extracellular microenvironment could determine the cellular phenotypes and then affected the cellular functions. The expressions of HAb18G/CD147 in HCC cells and fibroblasts were both obviously elevated in 3-D co-culture model. The overexpression of HAb18G/CD147 increased MMPs' (MMP-2 and MMP-9) production (P < 0.01), and was obviously accompanied with enhanced expressions of paxillin, FAK and p-FAK in 3-D cell co-culture model. All the results suggest that HAb18G/CD147 plays an important role in HCC adhesion, invasion and metastasis mainly via modulating synthesis of MMPs and activating integrin signal pathways in fibroblasts and tumor cells themselves under the 3-D co-culture conditions.     

黑河中游春玉米叶片水δD和δ18O的富集过程和影响因素

植物水的稳定同位素分馏过程是水在土壤-植物-大气连续体中循环的重要环节。以往研究由于叶片水¹⁸O同位素比值(δ¹⁸O _l,b)和氘(D)同位素比值(δD_l,b)(合称δ_l,b)实测数量少只能作为模型验证数据, 导致δ_l,b富集机制研究多集中于模型研究, 缺乏基于野外试验条件的δ_l,b富集的控制机制研究。叶片水δD_l,b和δ¹⁸O _l,b的富集程度(ΔD_l,b和Δ¹⁸O _l,b, 合称Δ_l,b)通常表示为δ_l,b与茎秆水D同位素比值(δD_x)和¹⁸O同位素比值(δ¹⁸O_x) (合称δ_x)之差, 即Δ_l,b = δ_l,b - δ_x。该研究以黑河中游沙漠绿洲春玉米(Zea mays)生态系统为研究对象, 重点采集和分析了季节和日尺度δ_l,b和δ_x数据, 配套开展了大气水汽δ¹⁸O和δD (合称δ_v)等辅助变量的原位连续观测, 探讨了季节和日尺度上的δ_l,b富集特征及其影响因素。结果表明: 叶片水δ_l,b和Δ_l,b的季节变化趋势不明显, 而受蒸腾作用影响表现出白天富集夜间贫化的单峰日变化特征。对于D来说, 无论季节尺度上还是日尺度上, 大气水汽δ_v和相对湿度是δD_l,b和ΔD_l,b的主要环境控制因素; 而对于¹⁸O来说, 无论季节尺度上还是日尺度上, 相对湿度是δ¹⁸O _l,b和Δ¹⁸O _l,b的主要环境控制因素。由于D和¹⁸O在热力学平衡分馏上有约8倍差异, 直接分析叶片水ΔD_l,b和Δ¹⁸O_l,b与影响因素的差异性, 有助于理解叶片水δD和δ¹⁸O富集过程以及对模型发展有一定的指导意义。