Non-homologous end joining pathway of the human pathogen Cryptococcus neoformans influences homologous integration efficiency but not virulence

The efficiency of gene targeting by integration through homologous recombination (homologous integration, HI) in the human pathogen Cryptococcus neoformans remains unsatisfactory. In order to achieve a much more efficient gene targeting system in C. neoformans, a new double knockout strain in genes involved in the non-homologous end joining (NHEJ) pathway was constructed. HI frequency was elevated by as much as approximately fivefold in the single or double knockout strains in NHEJ genes, and the frequency depended on the gene targeted. None of the NHEJ gene knockouts showed significant differences in regular growth, sensitivity to DNA-damaging drugs or UV, and virulence compared to the wild-type control, suggesting that the NHEJ pathway does not play a significant role in these biological stresses in C. neoformans. It was also suggested that the genes analyzed in this study are components of a single NHEJ pathway, as the mutants (including the double mutant) displayed the same phenotypes.     

Consecutive monitoring of lifelong production of conidia by individual conidiophores of Blumeria graminis f. sp. hordei on barley leaves by digital microscopic techniques with electrostatic micromanipulation

Conidial formation and secession by living conidiophores of Blumeria graminis f. sp. hordei on barley leaves were consecutively monitored using a high-fidelity digital microscopic technique combined with electrostatic micromanipulation to trap the released conidia. Conidial chains formed on conidiophores through a series of septum-mediated division and growth of generative cells. Apical conidial cells on the conidiophores were abstricted after the conidial chains developed ten conidial cells. The conidia were electrically conductive, and a positive charge was induced in the cells by a negatively polarized insulator probe (ebonite). The electrostatic force between the conidia and the insulator was used to attract the abstricted conidia from the conidiophores on leaves. This conidium movement from the targeted conidiophore to the rod was directly viewed under the digital microscope, and the length of the interval between conidial septation and secession, the total number of the conidia produced by a single conidiophore, and the modes of conidiogenesis were clarified. During the stage of conidial secession, the generative cells pushed new conidial cells upwards by repeated division and growth. The successive release of two apical conidia was synchronized with the successive septation and growth of a generative cell. The release ceased after 4-5 conidia were released without division and growth of the generative cell. Thus, the life of an individual conidiophore (from the erection of the conidiophore to the release of the final conidium) was shown to be 107 h and to produce an average of 33 conidia. To our knowledge, this is the first report on the direct estimation of life-long conidial production by a powdery mildew on host leaves.     

Structure-activity relationship studies on UK-2A, a novel antifungal antibiotic from Streptomyces sp. 517-02. Part 5: Roles of the 9-membered dilactone-ring moiety in respiratory inhibition

Several open-chained analogues of UK-2A, a novel antifungal antibiotic isolated from Streptomyces sp. 517-02, were prepared for structure-activity studies. The in vitro antifungal activities of these compounds against Rhodotorula mucilaginosa IFO 0001 and the inhibition of uncoupler-stimulated respiration in bovine heart submitochondrial particles (SMP) were evaluated. Oxidative potentials were measured by cyclic voltammetry. An analogue prepared from dihexyl L-glutamate showed comparable inhibitory activity as UK-2A.     

Nuphar alkaloids with immediately apoptosis-inducing activity from Nuphar pumilum and their structural requirements for the activity

The methanolic extract and its alkaloid fraction from the rhizomes of Nuphar pumilum showed cytotoxic effects on human leukemia cell (U937), mouse melanoma cell (B16F10), and human fibroblast (HT1080). Dimeric sesquiterpene thioalkaloids with the 6-hydroxyl group (6-hydroxythiobinupharidine, 6,6'-dihydroxythiobinupharidine, 6-hydroxythionuphlutine B) showed substantial cytotoxic activity at a concentration of 10 microM, but dimeric sesquiterpene thioalkaloids lacking the 6-hydroxyl group (thiobinupharidine, thionuphlutine B, 6'-hydroxythionuphlutine B, neothiobinupharidine, thionuphlutine B beta-sulfoxide, and neothiobinupharidine beta-sulfoxide) and monomeric sesquiterpene alkaloids (nupharidine, 7-epideoxynupharidine, and nupharolutine) showed weak activity. Next, apoptosis-inducing activity of a principal active constituent, 6-hydroxythiobinupharidine, on U937 was examined using morphological observation and DNA fragmentation assay (TUNEL method). Apoptosis of U937 was immediately observed within 1 h after treatment of 6-hydroxythiobinupharidine at 2.5-10 microM.     

Prevention of amyloid fibril formation of amyloidogenic chicken cystatin by site-specific glycosylation in yeast

To address the role of glycosylation on fibrillogenicity of amyloidogenic chicken cystatin, the consensus sequence for N-linked glycosylation (Asn106-Ile108 --> Asn106-Thr108) was introduced by site-directed mutagenesis into the wild-type and amyloidogenic chicken cystatins to construct the glycosylated form of chicken cystatins. Both the glycosylated and unglycosylated forms of wild-type and amyloidogenic mutant I66Q cystatin were expressed and secreted in a culture medium of yeast Pichia pastoris transformants. Comparison of the amount of insoluble aggregate, the secondary structure, and fibrillogenicity has shown that the N-linked glycosylation could prevent amyloid fibril formation of amyloidogenic chicken cystatin secreted in yeast cells without affecting its inhibitory activities. Further study showed this glycosylation could inhibit the formation of cystatin dimers. Therefore, our data strongly suggested that the mechanism causing the prevention of amyloidogenic cystation fibril formation may be realized through suppression of the formation of three-dimensional domain-swapped dimers and oligomers of amyloidogenic cystatin by the glycosylated chains at position 106.     

Evaluation of mismatch-binding ligands as inhibitors for Rev-RRE interaction

Drugs targeting the stem-loop IIB of Rev responsible element (RRE) of HIV-1 mRNA are potential therapeutic agents for HIV-1 infection. The stem loop is characterized by an internal loop consist of consecutive G-G and G-A mismatches, which is the single binding site for Rev protein for nuclear export of viral mRNA. We report here that ligands binding to G-G and G-A mismatches in duplex DNA also bind to the internal loop in competition with Rev peptide and lead to the dissociation of pre-formed Rev-RRE complex in a model system.     

Design of multifunctional peptides expressing both antimicrobial activity and shiga toxin neutralization activity

We have designed novel short peptides expressing both antimicrobial and Shiga-toxin (Stx) neutralization activities by combining nuclear localization signal (NLS) peptides (RIRKKLR, PKKKRKV, and PRRRK) tandemly with globotriaoside (Gb3) mimic peptide (WHWTWL). These fusion peptides exhibited excellent antimicrobial activity against both gram-positive and gram-negative bacteria. A peptide WHWTWLRIRKKLR (Trp-His-Trp-Thr-Trp-Leu-Arg-Ile-Arg-Lys-Lys-Leu-Arg), especially, exhibited about 100 times higher activity than the original NLS peptide. SPR analysis demonstrated that the binding of this peptide to both Stxs was strong: K(d) = 6.6 x 10(-6) to Stx-1 and 6.8 x 10(-6) to Stx-2. The in vitro assay against Stx-1 using HeLa cells showed that this peptide increased the survival rate of HeLa cells against the infection of Stx-1. The peptide has been found to maintain high antimicrobial activity, Stx neutralization activity, and no cytotoxicity at its concentration of 7.8-31.3 microg/mL (4.2-16.7 microM). The present peptide design has a prospect of developing potent multifunctional drugs to destroy proteinaceous toxin-producing bacteria and to simultaneously neutralize the toxins released by bacteriolysis.     

MEK�CERK-dependent multiple caspase activation by mitochondrial proapoptotic Bcl-2 family proteins is essential for heavy ion irradiation-induced glioma cell death

Recently developed heavy ion irradiation therapy using a carbon beam (CB) against systemic malignancy has numerous advantages. However, the clinical results of CB therapy against glioblastoma still have room for improvement. Therefore, we tried to clarify the molecular mechanism of CB-induced glioma cell death. T98G and U251 human glioblastoma cell lines were irradiated by CB, and caspase-dependent apoptosis was induced in both cell lines in a dose-dependent manner. Knockdown of Bax (BCL-2-associated X protein) and Bak (BCL-2-associated killer) and overexpression of Bcl-2 or Bcl-xl (B-cell lymphoma-extra large) showed the involvement of Bcl-2 family proteins upstream of caspase activation, including caspase-8, in CB-induced glioma cell death. We also detected the activation of extracellular signal-regulated kinase (ERK) and the knockdown of ERK regulator mitogen-activated protein kinase kinase (MEK)1/2 or overexpression of a dominant-negative (DN) ERK inhibited CB-induced glioma cell death upstream of the mitochondria. In addition, application of MEK-specific inhibitors for defined periods showed that the recovery of activation of ERK between 2 and 36 h after irradiation is essential for CB-induced glioma cell death. Furthermore, MEK inhibitors or overexpression of a DN ERK failed to significantly inhibit X-ray-induced T98G and U251 cell death. These results suggested that the MEK–ERK cascade has a crucial role in CB-induced glioma cell death, which is known to have a limited contribution to X-ray-induced glioma cell death.