Patt1, a novel protein acetyltransferase that is highly expressed in liver and downregulated in hepatocellular carcinoma,enhances apoptosis of hepatoma cells

Protein acetylation is increasingly recognized as an important post-translational modification. Although a lot of protein acetyltransferases have been identified, a few putative acetyltransferases are yet to be studied. In this study, we identified a novel protein acetyltransferase, Patt1, which belongs to GNAT family. Patt1 exhibited histone acetyltransferase activity and auto-acetylation activity. Deletion and mutation analysis of the predicted acetyltransferase domain in Patt1 showed that the conserved Glu139 was an important residue for its protein acetyltransferase activity. Furthermore, we found that Patt1 was highly expressed in liver and significantly downregulated in hepatocellular carcinoma tissues. In addition, we showed that overexpression of Patt1 enhanced the apoptosis of hepatoma cells dependent on its acetyltransferase activity, whereas knockdown of Patt1 significantly protected Chang liver cells from apoptosis. These data suggest that Patt1 might be involved in the development of hepatocellular carcinoma, and could be served as a potential therapy target for hepatocellular carcinoma.     

Investigation of bathymetry and water quality of Lake Nam Co, the largest lake on the central Tibetan Plateau, China

Comprehensive field investigations have been conducted four times on Nam Co, central Tibet, from September 2005 to September 2008. Here, we present the preliminary results focusing on the bathymetric survey and water quality measurements. The isobathic map shows that Nam Co is a high-altitude, deep lake where a flat and large basin lies in the central part with a water depth of more than 90 m. Water depth data from the northwestern bank areas of Nam Co provide unquestionable evidence of rising water levels in the last 3 decades because of the formation of two small islands that were still peninsulas in the 1970s. Water quality measurements taken at 19 stations during three summer field campaigns (2006, 2007 and 2008) covering almost all of the lake areas showed that the temperature, pH, dissolved oxygen and electric conductivity of surface water are on average 11.43°C, 9.21, 8.90 mg l⁻¹ and 1,851 μS cm⁻¹, respectively. The surface water shows no obvious spatial variability among all the stations. Vertical fluctuations of profiles, however, display some differences in thermocline and related parameters, such as pH and dissolved oxygen. According to the vertical variations of water quality parameters, the water column in relatively deep lake areas of Nam Co could be divided into three layers with distinctly various features: the epilimnion is from the surface to about 18–20 m depth in which the parameters are homogeneous with higher temperature and abundant sunlight; the metalimnion ranged from 20–60 m where a thermocline develops; the deepest layer forms a cold and dark hypolimnion.     

布鲁氏菌BP26基因标记疫苗株的构建及鉴别PCR方法的建立

[目的]由于现有的减毒活疫苗仍存在较强的毒力,因抗原与毒株的差异不大而很难区分疫苗免疫和自然感染等缺点,限制了现有布鲁氏菌减毒活疫苗的广泛应用.本文拟对布鲁氏菌的减毒活疫苗株M5进行遗传改造,克服这些缺点.[方法]本研究利用同源重组的方法,用卡那抗性基因替换了布鲁氏菌减毒疫苗株M5的BP26基因,得到了新的标记疫苗株M5△BP26.分别用标记疫苗株和野生株侵染巨噬细胞和感染小鼠,比较分析标记株在细胞内和小鼠体内的存活能力.根据种特异性保守基因dnaK和缺失的BP26基因设计引物,建立双重PCR,用于区分标记株与野生株.[结果]成功构建了.BP26基因标记疫苗株,细胞实验和动物实验结果表明,标记株仍能在胞内和小鼠内存活,具备作为减毒活疫苗的特性.小鼠实验结果显示,感染后两周野生株的细菌数为1022.9 ,而突变株为101.1 (P<0.01),至第3周野生株的细菌数为102.2 ,而突变株未能检出,表明与原疫苗株相比,标记株的感染力进一步减弱.根据DNA序列的差异,建立了能够区分标记疫苗株与野生株的双重PCR方法,标记株因只能扩增出一条带而能与野生株和毒株相区分,从而可以区分自然感染和疫苗免疫.[结论]基因标记疫苗株的构建及鉴别PCR方法的建立,为布鲁氏菌疫苗的进一步研发奠定了基础.     

The Parkinson’s disease kinase LRRK2 autophosphorylates its GTPase domain at multiple sites

Mutations in leucine-rich repeat kinase 2 (LRRK2) are a common cause of inherited Parkinson’s disease (PD). The protein is large and complex, but pathogenic mutations cluster in a region containing GTPase and kinase domains. LRRK2 can autophosphorylate in vitro within a dimer pair, although the significance of this reaction is unclear. Here, we mapped the sites of autophosphorylation within LRRK2 and found several potential phosphorylation sites within the GTPase domain. Using mass spectrometry, we found that Thr1343 is phosphorylated and, using kinase dead versions of LRRK2, show that this is an autophosphorylation site. However, we also find evidence for additional sites in the GTPase domain and in other regions of the protein suggesting that there may be multiple autophosphorylation sites within LRRK2. These data suggest that the kinase and GTPase activities of LRRK2 may exhibit complex autoregulatory interdependence.     

PRC1 Cooperates with CLASP1 to Organize Central Spindle Plasticity in Mitosis

During cell division, chromosome segregation is governed by the interaction of spindle microtubules with the kinetochore. A dramatic remodeling of interpolar microtubules into an organized central spindle between the separating chromatids is required for the initiation and execution of cytokinesis. Central spindle organization requires mitotic kinesins, microtubule-bundling protein PRC1, and Aurora B kinase complex. However, the precise role of PRC1 in central spindle organization has remained elusive. Here we show that PRC1 recruits CLASP1 to the central spindle at early anaphase onset. CLASP1 belongs to a conserved microtubule-binding protein family that mediates the stabilization of overlapping microtubules of the central spindle. PRC1 physically interacts with CLASP1 and specifies its localization to the central spindle. Repression of CLASP1 leads to sister-chromatid bridges and depolymerization of spindle midzone microtubules. Disruption of PRC1-CLASP1 interaction by a membrane-permeable peptide abrogates accurate chromosome segregation, resulting in sister chromatid bridges. These findings reveal a key role for the PRC1-CLASP1 interaction in achieving a stable anti-parallel microtubule organization essential for faithful chromosome segregation. We propose that PRC1 forms a link between stabilization of CLASP1 association with central spindle microtubules and anti-parallel microtubule elongation.To ensure that each daughter cell receives the full complement of the genome in each cell division, chromosomes move poleward, and non-kinetochore fibers become bundled at the onset of anaphase, initiating assembly of the central spindle, a set of anti-parallel microtubules that serves to concentrate key regulators of cytokinesis (1–3). Chromosomal passengers are a group of evolutionarily conserved proteins that orchestrates chromosome segregation and central spindle plasticity (4, 5). This protein complex containing Aurora B, Survivin, INCENP, and Borealin is relocated from the kinetochore to the central spindle upon anaphase onset (5–9). Perturbation of their function results in defects in metaphase chromosome alignment, chromosome segregation, and cytokinesis (10).Among the central spindle maintenance components, only two have been reported to mediate the microtubule bundling in the central spindle. One is centralspindlin, a heterotetramer containing CeMKLP1/ZEN-4 and RhoGAP/CYK-4 (11), and the other one is an evolutionarily conserved protein, PRC1 (also named Feo in fruit fry, Ase1 in yeast, and MAP65 in plant cells). PRC1 is a non-motor microtubule-binding and -bundling protein in human cells originally identified as a Cdc2 substrate essential for cytokinesis (12, 13). Similar microtubule regulatory activities have been reported in yeast, fruit fly, and plant cells. It is well known that overexpression of wild type PRC1 in HeLa cells can result in thick microtubule bundles in cells at interphase (13). Bundling activity of PRC1, as well as centralspindlin, is required for the organization of the central spindle as well as for the successful progression of cytokinesis. PRC1 molecules accumulate on the midline of a central spindle with the cell cycle progression to anaphase. As a non-motor microtubule-binding protein, transportation of PRC1 to the midline is promoted by its association to kinesin, KIF4A, and timing of this progression is controlled by the dephosphorylation of Thr-481 on PRC1 when the cell exits metaphase by phosphatase Cdc14 (14). Our recent study shows that prevention of the phosphorylation of PRC1 at Thr-470 causes an inhibition in PRC1 oligomerization in vitro and an aberrant organization of central spindle in vivo, suggesting that this phosphorylation-dependent PRC1 oligomerization ensures that central spindle assembly occurs at the appropriate time in the cell cycle (15).Spatiotemporal regulation of microtubule organization and dynamics is responsible for the mitotic apparatus such as the central spindle. However, it has remained elusive as to how the central spindle microtubule organization and dynamics are regulated. There are large varieties of microtubule-associated proteins responsible for regulation of the dynamic behavior of microtubules and microtubule-mediated transport. Among these, proteins that associate with the tips of microtubules are called +TIPs, for “plus-end tracking proteins.” These proteins have been shown to be important in different organisms and cellular systems (16). Using yeast two-hybrid assay, CLASPs were identified as interacting partners of the CLIPs and characterized as new +TIP proteins (17).The microtubule-binding protein CLASP is emerging as an important microtubule regulator in the formation of the mitotic apparatus (18–22). CLASP is required for promoting plus-end growth of spindle microtubules in prometaphase (23). Although the molecular mechanisms underlying its regulation of microtubule dynamics remain elusive, it is generally believed that CLASP orchestrates microtubule dynamics via its physical interacting with EB1, CLIP170, and microtubules (17, 24).To delineate the molecular function of PRC1 in central spindle organization and spatiotemporal regulation, we carried out a new search for PRC1-interacting proteins. Our studies show that PRC1 physically interacts with CLASP1, and the two proteins cooperate in the organization of the central spindle. Our studies provide a novel regulatory mechanism in which the PRC1 complex operates central spindle organization in mitosis.     

Molecular dynamics simulations and MM–PBSA calculations of the lectin from snowdrop (Galanthus nivalis)

Galanthus nivalis agglutinin (GNA), a mannose-specific lectin from snowdrop bulbs, is a member of the monocot mannose-specific lectin family and exhibits antiviral activity toward HIV. In the present study, molecular dynamics (MD) simulations were performed to study the interaction between GNA and its carbohydrate ligand over a specific time span. By analysis of the secondary structures, it was observed that the GNA conformation maintains rather stable along the trajectories and the high fluctuations were only centered on the carbohydrate recognition domains. Our MD simulations also reproduced most of the hydrogen bonds observed in the x-ray crystal structure. Furthermore, the obtained MD trajectories were used to estimate the binding free energy of the complex using the molecular mechanics/Poisson Boltzmann surface area (MM-PBSA) method. It was revealed by the inspection of the binding free energy components that the major contributions to the complex stability arose from electrostatic interactions.     

Further Daphniphyllum Alkaloids with Insecticidal Activity from the Bark of Daphniphyllum macropodum Miq.

Two new Daphniphyllum alkaloids, macropodumines J and K ( 1 and 2 , resp.), together with six known structurally related alkaloids, 3 – 8 , were isolated from the bark of Daphniphyllum macropodum Miq . The structures of the new compounds 1 and 2 were elucidated on the basis of a comprehensive analysis of their spectroscopic and chemical data. Macropodumine J ( 1 ) contains a CN group which is relatively rare in naturally occurring alkaloids. All isolated compounds were tested for their insecticidal activities against a number of insect species. Daphtenidine C ( 5 ) is the most active compound against Plutella xylostella. This is the first report of insecticidal properties of Daphniphyllum alkaloids.     

突发性公共卫生事件中法医工作者的角色探究

突发性公共卫生事件已经成为当前人类社会面临的一项重大难题和挑战。在应对和处置各类突发性公共卫生事件法医工作者被社会和国家赋予了重要的义务和责任。本文对法医工作者在解决各类突发性公共卫生事件中的角色定位进行了探讨,阐明法医工作者在应对和处置突发性公共卫生事件中发挥的重要作用。同时,针对现在和未来突发性公共卫生事件的发生发展趋势,对法医工作者在应对和处置这些事件中的角色作用提出了展望,并对法医工作者如何来提高自身的综合业务能力和素质,以便更好地来扮演好在突发性公共卫生事件中的角色。