Seven temperature-sensitive cell lysis (cy) mutant strains of Saccharomyces cerevisiae were isolated which lyse at the restrictive temperature on hypotonic but not on osmotically supported medium. The seven mutants fell into four complementation groups, CLY12 to CLY15. The wild-type CLY1S gene was isolated by complementation of the clyl5 temperature-sensitive growth defect. Sequence analysis revealed that the complementing DNA fragment encoded a partial PKC1 gene, which has previously been isolated as an S. cerevisiae homolog of mammalian protein kinase C genes (D. E. Levin, F. 0. Fields, R. Kunisawa, J. M. Bishop, and J. Thorner, Cell 62:213-224, 1990 The yeast cell wall is a complex rigid structure, responsible for cell shape, which undergoes a series of significant changes during the mitotic cell cycle (6). For example, bud emergence requires modifications of the cell wall at a precisely localized site and controlled cell wall growth in order to produce a daughter cell. Other cellular processes such as mating and sporulation also involve specific alterations of the cell wall structure.Yeast cell walls are constructed almost entirely of two classes of polysaccharides: polymers of mannose covalently linked to peptides, which are termed mannoproteins, and polymers of glucose, termed glucans. A third sugar polymer of N-acetylglucosamine, chitin, is present in only minor amounts (8). A number of Saccharomyces cerevisiae mutants with defects in the synthesis of cell wall components have been isolated. Defects in agglutination with a 1,3-alinked mannose antiserum define mannoprotein (mnn) mutants (reviewed in Ballou [1]), yeast killer toxin-resistant (kre) mutants display reduced levels of 1,6-,-glucan in the cell wall (2), and chitin synthase mutants are unable to convert exogenous glucosamine to chitin (3,22). The major cell wall-degrading enzyme activities mainly consist of 1,3-,-and

No abstract

This study provides the first clinical evidence that CRTH2 receptors contribute to airflow limitation, symptoms and eosinophilic airway inflammation in asthma. OC000459 shows promise as a novel oral treatment for asthma and related disorders.

An 8-week treatment with the CRTH2-antagonist, OC000459, exerts modest, but significant, anti-eosinophil and beneficial clinical effects in adult patients with active, corticosteroid-dependent or corticosteroid-refractory EoE and is well tolerated.

The high-level expression of HIV-1 Rev in Escherichia coli is described. Protein in crude bacterial extracts was dissociated from bound nucleic acid with urea. A simple purification and renaturation protocol, monitored by circular dichroism, is described which results in high yields of pure protein. The purified protein binds with high affinity to the Rev-responsive element mRNA and has nativelike spectroscopic properties. The protein exhibits concentration-dependent self-association as judged by analytical ultracentrifugation and gel filtration measurements. Purified Rev showed reversible heat-induced aggregation over the temperature range 0-30 degrees C. This hydrophobic-driven and nonspecific protein association was inhibited by low concentrations of sulfate ions. Rev solutions at greater than 80 micrograms/mL, incubated at 0-4 degrees C, slowly polymerized to form long hollow fibers of 20-nm diameter. Filament formation occurs at a lower protein concentration and more rapidly in the presence of Rev-responsive mRNA. The nucleic acid containing filaments are about 8 nm in diameter and up to 0.4 micron in length. On the basis of physical properties of the purified protein, we have suggested that in the nucleus of infected cells, Rev binding to the Rev-responsive region of env mRNA may be followed by helical polymerization of the protein which results in coating of the nucleic acid. Coated nucleic acid could be protected from splicing in the nucleus and exported to the cytoplasm.

A characterization of the S. cerevisiae KRE6 and SKN1 gene products extends previous genetic studies on their role in (1-->6)-beta-glucan biosynthesis (Roemer, T., and H. Bussey. 1991. Yeast beta-glucan synthesis: KRE6 encodes a predicted type II membrane protein required for glucan synthesis in vivo and for glucan synthase activity in vitro. Proc. Natl. Acad. Sci. USA. 88:11295-11299; Roemer, T., S. Delaney, and H. Bussey. 1993. SKN1 and KRE6 define a pair of functional homologs encoding putative membrane proteins involved in beta-glucan synthesis. Mol. Cell. Biol. 13:4039-4048). KRE6 and SKN1 are predicted to encode homologous proteins that participate in assembly of the cell wall polymer (1-->6)-beta-glucan. KRE6 and SKN1 encode phosphorylated integral-membrane glycoproteins, with Kre6p likely localized within a Golgi subcompartment. Deletion of both these genes is shown to result in a dramatic disorganization of cell wall ultrastructure. Consistent with their direct role in the assembly of this polymer, both Kre6p and Skn1p possess COOH-terminal domains with significant sequence similarity to two recently identified glucan-binding proteins. Deletion of the yeast protein kinase C homolog, PKC1, leads to a lysis defect (Levin, D. E., and E. Bartlett-Heubusch. 1992. Mutants in the S. cerevisiae PKC1 gene display a cell cycle-specific osmotic stability defect. J. Cell Biol. 116:1221-1229). Kre6p when even mildly overproduced, can suppress this pkc1 lysis defect. When mutated, several KRE pathway genes and members of the PKC1-mediated MAP kinase pathway have synthetic lethal interactions as double mutants. These suppression and synthetic lethal interactions, as well as reduced beta-glucan and mannan levels in the pkc1 null wall, support a role for the PKC1 pathway functioning in cell wall assembly. PKC1 potentially participates in cell wall assembly by regulating the synthesis of cell wall components, including (1-->6)-beta-glucan.

Phosphomannose isomerase (PMI) catalyses the reversible isomerization of fructose-6-phosphate (F6P) and mannose-6-phosphate (M6P). Absence of PMI activity in yeasts causes cell lysis and thus the enzyme is a potential target for inhibition and may be a route to antifungal drugs. The 1.7 A crystal structure of PMI from Candida albicans shows that the enzyme has three distinct domains. The active site lies in the central domain, contains a single essential zinc atom, and forms a deep, open cavity of suitable dimensions to contain M6P or F6P The central domain is flanked by a helical domain on one side and a jelly-roll like domain on the other.

The high-level expression of human interleukin-la in Escherichiu coli is described. The protein contributes about 12% of the total cell protein and is associated with the soluble cytoplasmic fraction of the cell. A method for the purification of the protein is given which is based on anion-and cation-exchange chromatographies. The isolated protein, shown to be homogeneous by several analytical methods, has been characterized by amino acid analysis, N-and C-terminal sequence analysis and analytical centrifugation. The protein is biologically active as demonstrated by two different in vifro assays, namely, the mononuclear cell factor (IL-1/MCF) assay and lymphocyte activating factor (IL-1 /LAF) assay. The specific activities determined with the IL-1/MCF and IL-l/ LAF assays, are 2 x lo7 and 4 x lo7 units mg-', respectively.The term interleukin-1 (IL-1) applies to at least two cytokines which play a role in immunity and in the pathophysiology of inflammation [I -31. Preparations of authentic IL-1 tend to be contaminated with other cytokine mediators which can complicate the interpretation of sensitive IL-1 bioassays (see, for example [4]). The availability of IL-1 produced by recombinant DNA technology would eliminate the problem of potential contamination and provide a reliable source of well characterized cytokine.Recently, the coding sequences for human IL-la and have been cloned from peripheral blood monocytes and their expressed products shown to possess IL-1 activities [5, 61. Using published sequence data we have isolated clones of IL-lP cDNA from a library constructed from mRNA expressed in human histiocytic lymphoma U937 cells. Here we report the expression of the mature IL-la protein in Escherichiu coli, a method for its purification, and the physiochemical and biological properties of the purified protein. MATERIALS AND METHODS Bacterial hosts and plusmids