乙型肝炎病毒转录后调节元件功能及作用机制

乙型肝炎病毒(HBV)转录体上存在与相应的细胞核蛋白结合的特殊序列,参与转录体稳定性和核浆转运等转录后调节过程。更为重要的是,细胞因子介导非细胞损伤抗HBV的主要作用环节也是在转录后水平。因此,对HBV转录后调节机制的研究不仅能加深对HBV生活周期的认识,而且还将为抗HBV治疗提供新的设计思路。

Construction of a fusion protein expression vector MK-EGFP and its subcellular localization in different carcinoma cell lines

AIM： To construct an expression plasmid encoding human wild-type midkine （MK） and enhanced green fluorescence protein （EGFP） fusion protein （MK-EGFP）, and to analyze the subcellular localization of MK in different cardnoma cell lines. METHODS： Two kinds of MK coding sequences with or without signal peptide were cloned into plasmid pEGFP-N2, and the recombinant plasmids constructed were introduced into HepG2, MCF7 and DU145 cells, respectively, by transfection. With the help of laser scanning confocal microscopy, the expression and subcellular localization of MK-GFP fusion protein could be detected. RESULTS： Compared with the GFP control, in which fluorescence was detected diffusely over the entire cell body except in the nucleolus, both kinds of fusion protein MK-GFP were localized exclusively to the nucleus and accumulated in the nucleolus in the three kinds of cancer cell lines. CONCLUSION： This study reveals the specific nucleolar translocation independent of signal peptide, which may be involved in the mechanism that MK works. It provides valuable evidence for further study on the functions of MK in nucleus and its possible mechanisms, in which ribosomal RNA transcription and ribosome assembly are involved.

Nuclear effects of ethanol-induced proteasome inhibition in liver cells

Alcohol ingestion causes alteration in several cellular mechanisms, and leads to inflammation, apoptosis, immunological response defects, and fibrosis. These phenomena are associated with significant changes in the epigenetic mechanisms, and subsequently, to liver cell memory. The ubiquitin-proteasome pathway is one of the vital pathways in the cell that becomes dysfunctionial as a result of chronic ethanol consumption. Inhibition of the proteasome activity in the nucleus causes changes in the turnover of transcriptional factors, histone modifying enzymes, and therefore, affects epigenetic mechanisms. Alcohol consumption has been associated with an increase in histone acetylation and a decrease in histone methylation, which leads to gene expression changes. DNA and histone modifications that result from ethanol-induced proteasome inhibition are key players in regulating gene expression, especially genes involved in the cell cycle, immunological responses, and metabolism of ethanol. The present review highlights the consequences of ethanol-induced proteasome inhibition in the nucleus of liver cells that are chronically exposed to ethanol.

LYSOPHOSPHATIDIC ACID ACTIVATES NUCLEAR NUCLEOSIDE TRIPHOSPHATASE IN RAT HEPATOCYTES

Objectives.To observe if lysophosphatidic acid(LPA)can influence nuclear nucleoside triphos-phatase(NTPase)activity of isolated hepatocyte from rat,and to investigate the possible mechanisms by which LPA affects the NTPase.Method.Isolated and cultured hepatocytes from rat liver were exposed to LPA(1×10 -9 ,1×10 -8 and5×10 -8 mol/L)with or without inhibitors of protein kinase C(PKC)and mitogen activating protein kinase kinase(MAPKK),and the NTPase activity on nuclear envelope was assayed using ATP and GTP as substrate,respectively.Results.Nuclear NTPase activity of rat hepatocytes was potently stimulated by incubation of hepato-cytes with LPA in concentration?and time ?dependent manners.In hepatocytes incubated with LPA,nu-clear NTPase activity was significantly higher than that of the control(P<0.01).In hepatocytes preincu-bated with PKC inhibitor H-7or MAPKK inhibitor PD98059,LPA-stimulated activation of nuclear NT-Pase was obviously attenuated.In addition,direct incubation of isolated hepatic nuclei with LPA had no effect on nuclear NTPase activity.Conclusion.LPA is involved in modulating nuclear NTPase activity in hepatocytes.The stimulating effect of LPA on the nuclear NTPase is mediated at least partly by PKC and MAPK-dependent pathway.

Nuclear proteome profile of C57BL/6J mouse liver

The liver proteome can serve as a reference to better understand both disease mechanisms and possible therapeutics,since the liver is an important organ in the body that performs a large number of tasks.Here we identify the organelle proteome of C57BL/6J mouse liver nuclei as a promising strategy to enrich low abundance proteins,in the sense that analysis of whole liver cells is rather complex for current techniques and may not be suitable for proteins with low abundance.Evaluation of nucleus integrity and purity was performed to demonstrate the effectiveness of the optimized isolation procedure.The extracted nuclear proteins were identified by 2-DE MS analyses,and a total of 748 proteins were identified.Bioinformatic analyses were performed to demonstrate the physicochemical properties,cellular locations and functions of the proteins.