The budding yeast proteins Spc24p and Spc25p interact with Ndc80p and Nuf2p at the kinetochore and are important for kinetochore clustering and checkpoint control

Here, we show that the budding yeast proteins Ndc80p, Nuf2p, Spc24p and Spc25p interact at the kinetochore. Consistently, Ndc80p, Nuf2p, Spc24p and Spc25p associate with centromere DNA in chromatin immunoprecipitation experiments, and SPC24 interacts genetically with MCM21 encoding a kinetochore component. Moreover, although conditional lethal spc24-2 and spc25-7 cells form a mitotic spindle, the kinetochores remain in the mother cell body and fail to segregate the chromosomes. Despite this defect in chromosome segregation, spc24-2 and spc25-7 cells do not arrest in metaphase in response to checkpoint control. Furthermore, spc24-2 cells showed a mitotic checkpoint defect when microtubules were depolymerized with nocodazole, indicating that Spc24p has a function in checkpoint control. Since Ndc80p, Nuf2p and Spc24p are conserved proteins, it is likely that similar complexes are part of the kinetochore in other organisms.     

Analysis of a 2,4,6-trichlorophenol-dehalogenating enrichment culture and isolation of the dehalogenating member Desulfitobacterium frappieri strain TCP-A

An anaerobic, 2,4,6-trichlorophenol ortho-dehalogenating mixed culture was enriched from sediment of the river Saale (Germany). Two isolated dechlorinating colonies (MK1 and MK2) consisted of rods of different lengths and thicknesses, indicating heterogeneity. Following subcultivation with thiosulfate as alternative electron acceptor and cocultivation with Clostridium celerecrescensT, the 2,4,6-trichlorophenol-dehalogenating bacterium Desulfitobacterium frappieri strain TCP-A was isolated and characterized regarding its taxonomic properties and the spectrum of chlorophenols that it dehalogenated. Four other bacterial strains were coenriched and identified as organisms with closest phylogenetic relatedness to the Clostridium type strains C. indolis, C. glycolicum, C. hydroxybenzoicum and C. sporosphaeroides (16S rDNA sequence identities of 99.5, 99.2, 94.4, and 93.5%, respectively). Amplified ribosomal DNA restriction analysis of the original dehalogenating cultures MK1 and MK2 (when not exposed to thiosulfate) confirmed the microbial heterogeneity and revealed the presence of two additional species related to the type strains of C. celerecrescens and Clostridium propionicum. Only one copy of the 16S rRNA genes of Desulfitobacterium frappieri in each of the clone libraries of MK1 and MK2 (containing 136 and 56 clones, respectively) was found by dot-blot hybridization, suggesting a relatively low number of the dehalogenating bacterium within the enrichment culture.     

The joys of HexNAc. The synthesis and function of N-andO-glycan branches

This review covers discoveries made over the past 30–35 years that were important to our understanding of the synthetic pathway required for initiation of the antennae or branches on complex N-glycans and O-glycans. The review deals primarily with the author's contributions but the relevant work of other laboratories is also discussed. The focus of the review is almost entirely on the glycosyltransferases involved in the process. The following topics are discussed. (1) The localization of the synthesis of complex N-glycan antennae to the Golgi apparatus. (2) The evolutionary boundary at the stage in N-glycan processing where there is a change from oligomannose to complex N-glycans; this switch correlates with the appearance of multicellular organisms. (3) The discovery of the three enzymes which play a key role in this switch, N-acetylglucosaminyltransferases I and II and mannosidase II. (4) The yellow brick road which leads from oligomannose to highly branched complex N-glycans with emphasis on the enzymes involved in the process and the factors which control the routes of synthesis. (5) A short discussion of the characteristics of the enzymes involved and of the genes that encode them. (6) The role of complex N-glycans in mammalian and Caenorhabditis elegans development. (7) The crystal structure of N-acetylglucosaminyltransferase I. (8) The discovery of the enzymes which synthesize O-glycan cores 1, 2, 3 and 4 and their elongation.     

Full flexibility genotyping of single nucleotide polymorphisms by the GOOD assay

Recently a facile method for genotyping single nucleotide polymorphisms (SNPs) using MALDI mass spectrometry, termed the GOOD assay, was developed. It does not require any purification and is performed with simple liquid handling, thermal incubation and cycling steps. Although this method is well suited to automation and high-throughput analysis of SNPs, it did not allow full flexibility due to lack of certain reagents. A complete set of β-cyanoethyl phosphoramidites is presented herein that give this SNP genotyping method full sequence and multiplex capabilities. Applications to SNP genotyping in the prion protein gene, the β-2-adrenergic receptor gene and the angiotensin converting enzyme gene using the GOOD assay are demonstrated. Because SNP genotyping technologies are generally very sensitive to varying DNA quality, the GOOD assay has been stabilised and optimised for low quality DNA. A template extraction method is introduced that allows genotyping from tissue that was taken while placing an ear tag on an animal. This dramatically facilitates the application of genotyping to animal agricultural applications, as it demonstrates that expensive and cumbersome DNA extraction procedures prior to genotyping can be avoided.     

Why do cytotoxic T lymphocytes fail to eliminate hepatitis C virus? Lessons from studies using major histocompatibility complex class I peptide tetramers.

Hepatitis C virus (HCV) infection is a major public health problem, affecting an estimated 3% of the world's population, and over 10% in some countries. Infection in most cases becomes persistent, and can lead to hepatic inflammation, fibrosis and liver failure. The T lymphocyte reponse, in particular that mediated by cytotoxic T lymphocytes (CTLs), is likely to be involved in determining the outcome of infection, although its overall role is not clear. The use of major histocompatibility complex (MHC) class I peptide tetrameric complexes (tetramers) to study antiviral CTL responses has revolutionized our approach to the study of human infection. We have used a panel of MHC class I tetramers to analyse immune responses in HCV-infected individuals at various stages of disease. We find that the CTL response against HCV is vigorous in its early phases but dwindles over time both in terms of lymphocyte number and function. A number of potential explanations for this 'CTL failure' are discussed.     

Differential expression of cell-cell adhesion proteins and cyclin D in MEK1-transdifferentiated MDCK cells

Overexpression of aconstitutively active mutant of the mitogen-activated protein kinasekinase MEK1 (caMEK1) in epithelial Madin-Darby canine kidney (MDCK)-C7cells disrupts morphogenesis, induces an invasive phenotype, and isassociated with a reduced rate of cell proliferation. The role ofcell-cell adhesion molecules and cell cycle proteins in theseprocesses, however, has not been investigated. We now report loss ofE-cadherin expression as well as a marked reduction of - and-catenin expression in transdifferentiated MDCK-C7 cells stablyexpressing caMEK1 (C7caMEK1) compared with epithelial mock-transfectedMDCK-C7 (C7Mock1) cells. At least part of the remaining -catenin wascoimmunoprecipitated with -catenin, whereas no E-cadherin wasdetected in -catenin immunoprecipitates. In both cell types, theproteasome-specific protease inhibitors N-acetyl-Leu-Leu-norleucinal (ALLN) and lactacystin led to atime-dependent accumulation of -catenin, including the appearance ofhigh-molecular-weight -catenin species. Quiescent as well asserum-stimulated C7caMEK1 cells showed a higher cyclin D expressionthan epithelial C7Mock1 cells. The MEK inhibitor U-0126 inhibitedextracellular signal-regulated kinase phosphorylation and cyclin Dexpression in C7caMEK1 cells and almost abolished their already reducedcell proliferation rate. We conclude that the transdifferentiated andinvasive phenotype of C7caMEK1 cells is associated with a diminishedexpression of proteins involved in cell-cell adhesion. Although-catenin expression is reduced, C7caMEK1 cells show a higherexpression of U-0126-sensitive cyclin D protein.

     

Hepatocyte growth factor stimulates the growth and activates mitogen-activated protein kinase in human hepatoma cells

Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes and various epithelial cells. Unexpectedly, it has been reported to inhibit the growth of hepatoma cells in vitro. To clarify this phenomenon, we examined the effects of recombinant baculovirus-expressed HGF on the growth of 6 human hepatoma cell lines. The growth of Hep3B and HepG2 cells was markedly stimulated to 1.8- and 1.7-fold, respectively, PLC/PRF/5 to 1.4-fold, and SK-Hep-1 to 1.2-fold in a dose-dependent manner under HGF concentrations below 20 ng/ml. Neither HuH-7 nor HCC36 were affected. None of these cells were inhibited. All these cells expressed c-Met, the membrane receptor for HGF, and their c-Met would be activated to be phosphorylated upon addition of HGF. They also contained the ERK2 subgroup of mitogen-activated protein kinases (MAPKs). When HGF was added, their ERK2 would also be phosphorylated. The extent of ERK2 phosphorylation was partially correlated to their growth response to HGF. In conclusion, HGF could stimulate the growth of certain human hepatoma cells, probably through activation of c-Met and MAPKs.     

Experimental vaccine strategies for cancer immunotherapy

Recently, cancer immunotherapy has emerged as a therapeutic option for the management of cancer patients. This is based on the fact that our immune system, once activated, is capable of developing specific immunity against neoplastic but not normal cells. Increasing evidence suggests that cell-mediated immunity, particularly T-cell-mediated immunity, is important for the control of tumor cells. Several experimental vaccine strategies have been developed to enhance cell-mediated immunity against tumors. Some of these tumor vaccines have generated promising results in murine tumor systems. In addition, several phase I/II clinical trials using these vaccine strategies have shown extremely encouraging results in patients. In this review, we will discuss many of these promising cancer vaccine strategies. We will pay particular attention to the strategies employing dendritic cells, the central player for tumor vaccine development.