用识别四个GC对的限制酶研究高等担子菌线粒体DNA

本文报道了用识别四个GC对的限制性内切酶HaeⅢ、CofI、MsPI酶切高等担子菌伞菌目（Agaricales）、非褶菌目（Aphyllophorales）12个菌株的总DNA,在琼脂糖凝胶上显现线粒体DNA带谱的结果。通过对带型、累加分子量、酶切片段数和同源性的分析表明,不同种类高等担子菌的线粒体DNA变化较大．研究还显示,以多种识别四个GC对的限制酶分析高等担子菌的线粒体DNA及其它们的RFLP,比只用HaeⅢ更灵敏有效。     

Adenovirus-mediated expression of the C-terminal domain of SARS-CoV spike protein is sufficient to induce apoptosis in Vero E6 cells

The pro-apoptotic properties of severe acute respiratory syndrome coronavirus (SARS-CoV) structural proteins were studied in vitro. By monitoring apoptosis indicators including chromatin condensation, cellular DNA fragmentation and cell membrane asymmetry, we demonstrated that the adenovirus-mediated over-expression of SARS-CoV spike (S) protein and its C-terminal domain (S2) induce apoptosis in Vero E6 cells in a time- and dosage-dependent manner, whereas the expression of its N-terminal domain (S1) and other structural proteins, including envelope (E), membrane (M) and nucleocapsid (N) protein do not. These findings suggest a possible role of S and S2 protein in SARS-CoV induced apoptosis and the molecular pathogenesis of SARS.     

Characterization of humoral responses in mice immunized with plasmid DNAs encoding SARS-CoV spike gene fragments

The immunological characteristics of SARS-CoV spike protein were investigated by administering mice with plasmids encoding various S gene fragments. We showed that the secreting forms of S1, S2 subunits and the N-terminus of S1 subunit (residues 18-495) were capable of eliciting SARS-CoV specific antibodies and the region immediate to N-terminus of matured S1 protein contained an important immunogenic determinant for elicitation of SARS-CoV specific antibodies. In addition, mice immunized with plasmids encoding S1 fragment developed a Th1-mediated antibody isotype switching. Another interesting finding was that mouse antibodies elicited separately by plasmids encoding S1 and S2 subunits cooperatively neutralized SARS-CoV but neither the S1 nor S2 specific antibodies did, suggesting the possible role of both S1 and S2 subunits in host cell docking and entry. These results provide insights into understanding the immunological characteristics of spike protein and the development of subunit vaccines against SARS-CoV.     

Specific requirement for Bax, not Bak, in Myc-induced apoptosis and tumor suppression in vivo

Bax and Bak comprise the mitochondrial gateway for apoptosis induced by diverse stimuli. Loss of both bax and bak is necessary to block cell death induced by such stimuli, indicating a great degree of functional overlap between Bax and Bak. Apoptosis is the major intrinsic pathway that limits the oncogenic potential of Myc. Using a switchable mouse model of Myc-induced apoptosis in pancreatic beta cells, we have shown that Myc induces apoptosis in vivo exclusively through Bax but not Bak. Furthermore, blockade of Myc-induced apoptosis by the inactivation of Bax, but not Bak, eliminates all restraints to the oncogenic potential of Myc, allowing the rapid and synchronous progression of invasive, angiogenic tumors.     

Molecular advances in severe acute respiratory syndrome-associated coronavirus (SARS-CoV)

The sudden outbreak of severe acute respiratory syndrome (SARS) in 2002 prompted the establishment of a global scientific network subsuming most of the traditional rivalries in the competitive field of virology. Within months of the SARS outbreak, collaborative work revealed the identity of the disastrous pathogen as SARS-associated coronavirus (SARS-CoV). However, although the rapid identifi-     

Deficiency for the Cysteine Protease Cathepsin L Impairs Myc-Induced Tumorigenesis in a Mouse Model of Pancreatic Neuroendocrine Cancer

Motivated by the recent implication of cysteine protease cathepsin L as a potential target for anti-cancer drug development, we used a conditional MycER^TAM;Bcl-x_L model of pancreatic neuroendocrine tumorigenesis (PNET) to assess the role of cathepsin L in Myc-induced tumor progression. By employing a cysteine cathepsin activity probe in vivo and in vitro, we first established that cathepsin activity increases during the initial stages of MycER^TAM;Bcl-x_L tumor development. Among the cathepsin family members investigated, only cathepsin L was predominately produced by beta-tumor cells in neoplastic pancreata and, consistent with this, cathepsin L mRNA expression was rapidly upregulated following Myc activation in the beta cell compartment. By contrast, cathepsins B, S and C were highly enriched in tumor-infiltrating leukocytes. Genetic deletion of cathepsin L had no discernible effect on the initiation of neoplastic growth or concordant angiogenesis. However, the tumors that developed in the cathepsin L-deficient background were markedly reduced in size relative to their typical wild-type counterparts, indicative of a role for cathepsin L in enabling expansive tumor growth. Thus, genetic blockade of cathepsin L activity is inferred to retard Myc-driven tumor growth, encouraging the potential utility of pharmacological inhibitors of cysteine cathepsins in treating late stage tumors.     

食用真菌线粒体DNA的直接分析

该文报道了以限制酶HaeIII酶切13个食用菌栽培品种的总DNA,在琼脂糖凝胶上直接显现线粒体DNA带的结果。结合另外两种限制酶CfoI和MSpI的酶切结果和HaeIII在其它真菌中的研究报道,提出了利用识别四个GC对的限制酶酶切真菌总DNA,直接分析线粒体DNA的方法。     

Phylogenetic analysis reveals a correlation between the expansion of very virulent infectious bursal disease virus and reassortment of its genome segment B

Infectious bursal disease virus (IBDV) is a birnavirus causing immunosuppressive disease in chickens. Emergence of the very virulent form of IBDV (vvIBDV) in the late 1980s dramatically changed the epidemiology of the disease. In this study, we investigated the phylogenetic origins of its genome segments and estimated the time of emergence of their most recent common ancestors. Moreover, with recently developed coalescence techniques, we reconstructed the past population dynamics of vvIBDV and timed the onset of its expansion to the late 1980s. Our analysis suggests that genome segment A of vvIBDV emerged at least 20 years before its expansion, which argues against the hypothesis that mutation of genome segment A is the major contributing factor in the emergence and expansion of vvIBDV. Alternatively, the phylogeny of genome segment B suggests a possible reassortment event estimated to have taken place around the mid-1980s, which seems to coincide with its expansion within approximately 5 years. We therefore hypothesize that the reassortment of genome segment B initiated vvIBDV expansion in the late 1980s, possibly by enhancing the virulence of the virus synergistically with its existing genome segment A. This report reveals the possible mechanisms leading to the emergence and expansion of vvIBDV, which would certainly provide insights into the scope of surveillance and prevention efforts regarding the disease.     

Quantitative comparison of the efficiency of antibodies against S1 and S2 subunit of SARS coronavirus spike protein in virus neutralization and blocking of receptor binding: implications for the functional roles of S2 subunit

Neutralizing effects of antibodies targeting the C-terminal stalk (S2) subunit of the spike protein of severe acute respiratory syndrome coronavirus have previously been reported, although its mechanism remained elusive. In this study, high titered mouse antisera against the N-terminal globular (S1) and S2 subunits of the S protein were generated and total immunoglobulin G (IgG) was purified from these antisera. The efficiency of these purified IgGs in virus neutralization and blocking of receptor binding were compared quantitatively using virus neutralization assay and a previously developed cell-based receptor binding assay, respectively. We demonstrated that anti-S1 IgG neutralizes the virus and binds to the membrane associated S protein more efficiently than anti-S2 IgG does. Moreover, both anti-S1 and anti-S2 IgGs were able to abolish the binding between S protein and its cellular receptor(s), although anti-S1 IgG showed a significantly higher blocking efficiency. The unexpected blocking ability of anti-S2 IgG towards the receptor binding implied a possible role of the S2 subunit in virus docking process and argues against the current hypothesis of viral entry. On the other hand, the functional roles of the previously reported neutralizing epitopes within S2 subunit were investigated using an antigen specific antibody depletion assay. Depletion of antibodies against these regions significantly diminished, though not completely abolished, the neutralizing effects of anti-S2 IgG. It suggests the absence of a major neutralizing domain on S2 protein. The possible ways of anti-S2 IgGs to abolish the receptor binding and the factors restricting anti-S2 IgGs to neutralize the virus are discussed.     

Evolutionary and transmission dynamics of reassortant H5N1 influenza virus in Indonesia

H5N1 highly pathogenic avian influenza (HPAI) viruses have seriously affected the Asian poultry industry since their recurrence in 2003. The viruses pose a threat of emergence of a global pandemic influenza through point mutation or reassortment leading to a strain that can effectively transmit among humans. In this study, we present phylogenetic evidences for the interlineage reassortment among H5N1 HPAI viruses isolated from humans, cats, and birds in Indonesia, and identify the potential genetic parents of the reassorted genome segments. Parsimony analyses of viral phylogeography suggest that the reassortant viruses may have originated from greater Jakarta and surroundings, and subsequently spread to other regions in the West Java province. In addition, Bayesian methods were used to elucidate the genetic diversity dynamics of the reassortant strain and one of its genetic parents, which revealed a more rapid initial growth of genetic diversity in the reassortant viruses relative to their genetic parent. These results demonstrate that interlineage exchange of genetic information may play a pivotal role in determining viral genetic diversity in a focal population. Moreover, our study also revealed significantly stronger diversifying selection on the M1 and PB2 genes in the lineages preceding and subsequent to the emergence of the reassortant viruses, respectively. We discuss how the corresponding mutations might drive the adaptation and onward transmission of the newly formed reassortant viruses.