Assignment of delta-endotoxin genes of the four lepidoptera-specific Bacillus thuringiensis strains that produce spherical parasporal inclusions

Unique strains of Bacillus thuringiensis, that belong to the four H serogroups (serovar sumiyoshiensis, serovar fukuokaensis, serovar darmstadiensis, and serovar japonensis) and produce spherical parasporal inclusions specifically toxic to lepidopteran larvae, were examined for comparative analysis of the genes encoding delta-endotoxin proteins. Gene analysis revealed that there is no difference between the four strains in nucleotide sequences of the 1, 937-bp DNA segment covering the four conserved regions and a partial sequence of the block 5 region. Surprisingly, the nucleotide sequence of the four strains showed a 100% homology with that of the corresponding region of the cry9D gene encoding a delta-endotoxin protein, which had been reported to be active on the scarabaeid coleopterans. Alignment analysis revealed that the N-terminal half (16-660) amino acid sequence of the four proteins shared relatively high homologies (27.7-35.8%) with those of the Cry9Ba, Cry9Ca, and Cry1Ba proteins, while lower homologies with those of the Cry3Aa, Cry8Ca, and Cry1Aa proteins. The results show that the cry9D gene is retained in multiple heterogeneous H serovars of Lepidoptera-specific B. thuringiensis populations naturally occurring in soil environments of Japan.

Cholesterol sulfate activates transcription of transglutaminase 1 gene in normal human keratinocytes

Cholesterol sulfate and transglutaminase 1 are essential for the process of keratinization. Cholesterol sulfate is formed during keratinization and activates the eta isoform of protein kinase C. Transglutaminase 1 is a key enzyme for formation of the cornified envelope in terminally differentiated keratinocytes. In this study, we demonstrated that cholesterol sulfate acts as a transcriptional activator of the transglutaminase 1 gene in normal human keratinocytes. Growth of normal human keratinocytes was inhibited by cholesterol sulfate, but not by its parental cholesterol. Treatment of normal human keratinocytes with cholesterol sulfate induced activity of transglutaminase 1 in a dose- and time-dependent manner. Activation of transcription of transglutaminase 1 by cholesterol sulfate was demonstrated by northern blotting analysis, whereas that by cholesterol was not. In order to identify a cholesterol sulfate responsive region in the transglutaminase 1 gene, plasmids were constructed containing a luciferase reporter gene ligated to deletion fragments of the 5' upstream region of the tranglutaminase 1 gene and were transfected into normal human keratinocytes. Transfected cells were treated with cholesterol sulfate, the phorbol ester 12-O-tetradecanoylphorbol-13-acetate and a high concentration of Ca2+. Our results indicate that the responsive element(s) for cholesterol sulfate and phorbol ester is located upstream of the human transglutaminase 1 gene at a position(s) between -819 and -549, whereas the responsive element for Ca2+ is located at a position between -79 and -49.

Phorbol ester-induced G1 arrest in BALB/MK-2 mouse keratinocytes is mediated by delta and eta isoforms of protein kinase C

We investigated the possible negative regulation of the cell cycle by protein kinase C (PKC) isoforms in synchronously grown BALB/MK-2 mouse keratinocytes, in which PKC isoforms were overexpressed by using the adenovirus vector Ax. Cells at the G1/S boundary of the cell cycle were the most sensitive to the inhibitory effect of 12-O-tetradecanoylphorbol-13-acetate (TPA), a PKC agonist, resulting in G1 arrest. TPA-induced inhibition of DNA synthesis was augmented by overexpression of the eta and delta isoforms, but rescued by the dominant-negative and antisense eta isoforms. In contrast, the alpha and zeta isoforms showed no effect on DNA synthesis with or without TPA treatment. Immunoblotting indicated cell cycle-dependent expression of the eta isoform, being highest in cells at the G1/S boundary. The present study provides evidence that the eta and delta isoforms of PKC are involved in negative regulation of cell cycle at the G1/S boundary in mouse keratinocytes.

Purification and substrate specificities of two alpha-L-arabinofuranosidases from Aspergillus awamori IFO 4033

alpha-L-Arabinofuranosidases I and II were purified from the culture filtrate of Aspergillus awamori IFO 4033 and had molecular weights of 81,000 and 62,000 and pIs of 3.3 and 3.6, respectively. Both enzymes had an optimum pH of 4.0 and an optimum temperature of 60 degreesC and exhibited stability at pH values from 3 to 7 and at temperatures up to 60 degrees C. The enzymes released arabinose from p-nitrophenyl-alpha-L-arabinofuranoside, O-alpha-L-arabinofuranosyl-(1-->3)-O-beta-D-xylopyranosyl-(1-->4)-D-x ylopyranose, and arabinose-containing polysaccharides but not from O-beta-D-xylopyranosyl-(1-->2)-O-alpha-L-arabinofuranosyl-(1-->3)-O-b eta-D-xylopyranosyl-(1-->4)-O-beta-D-xylopyranosyl-(1-->4)-D-xylopyra nose. alpha-L-Arabinofuranosidase I also released arabinose from O-beta-D-xylopy-ranosyl-(1-->4)-[O-alpha-L-arabinofuranosyl- (1-->3)]- O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose. However, alpha-L-arabinofuranosidase II did not readily catalyze this hydrolysis reaction. alpha-L-Arabinofuranosidase I hydrolyzed all linkages that can occur between two alpha-L-arabinofuranosyl residues in the following order: (1-->5) linkage > (1-->3) linkage > (1-->2) linkage. alpha-L-Arabinofuranosidase II hydrolyzed the linkages in the following order: (1-->5) linkage > (1-->2) linkage > (1-->3) linkage. alpha-L-Arabinofuranosidase I preferentially hydrolyzed the (1-->5) linkage of branched arabinotrisaccharide. On the other hand, alpha-L-arabinofuranosidase II preferentially hydrolyzed the (1-->3) linkage in the same substrate. alpha-L-Arabinofuranosidase I released arabinose from the nonreducing terminus of arabinan, whereas alpha-L-arabinofuranosidase II preferentially hydrolyzed the arabinosyl side chain linkage of arabinan.

Cavity adaptation of resin composite in canine cavity in vivo

The efficacy of four commercial and two experimental dentin bonding systems was examined by observing the cavity adaptation of commercial light-cured resin composites restored in the dogs scheduled to be sacrificed after a medical experiment. Before being sacrificed, a cylindrical class V cavity was prepared in each canine, and the cavity wall was treated with one of four commercial dentin bonding systems according to the manufacturers instructions followed by resin composite filling. The maximum contraction gap widths at the occlusal, gingival and axial cavity wall were measured on the cavity section 30 min after the polymerization of the resin composite under a light microscope. Contraction gap formation was completely prevented in only one of the experimental groups in which the cavity wall was primed with 35 vol% glyceryl mono-methacrylate (GM). In addition, observation of cavity adaptation in the canine in vivo was useful to estimate consistently the efficacy of the bonding systems.

Induction of differentiation in normal human keratinocytes by adenovirus-mediated introduction of the eta and delta isoforms of protein kinase C

Protein kinase C (PKC) plays a crucial role(s) in regulation of growth and differentiation of cells. In the present study, we examined possible roles of the alpha, delta, eta, and zeta isoforms of PKC in squamous differentiation by overexpressing these genes in normal human keratinocytes. Because of the difficulty of introducing foreign genes into keratinocytes, we used an adenovirus vector system, Ax, which allows expression of these genes at a high level in almost all the cells infected for at least 72 h. Increased kinase activity was demonstrated in the cells overexpressing the alpha, delta, and eta isoforms. Overexpression of the eta isoform inhibited the growth of keratinocytes of humans and mice in a dose (multiplicity of infection [MOI])-dependent manner, leading to G1 arrest. The eta-overexpressing cells became enlarged and flattened, showing squamous cell phenotypes. Expression and activity of transglutaminase 1, a key enzyme of squamous cell differentiation, were induced in the eta-overexpressing cells in dose (MOI)- and time-dependent manners. The inhibition of growth and the induction of transglutaminase 1 activity were found only in the cells that express the eta isoform endogenously, i.e., in human and mouse keratinocytes but not in human and mouse fibroblasts or COS1 cells. A dominant-negative eta isoform counteracted the induction of transglutaminase 1 by differentiation inducers such as a phorbol ester, 1alpha,25-dihydroxyvitamin D3, and a high concentration of Ca2+. Among the isoforms examined, the delta isoform also inhibited the growth of keratinocytes and induced transglutaminase 1, but the alpha and zeta isoforms did not. These findings indicate that the eta and delta isoforms of PKC are involved crucially in squamous cell differentiation.

Cloning and functional analysis of human p51, which structurally and functionally resembles p53

The p53 tumor suppressor gene, which is induced by DNA damage and/or stress stimuli, causes cells to undergo G1-arrest or apoptotic death; thus it plays an essential role in human carcinogenesis. We have searched for p53-related genes by using degenerate PCR, and have identified two cDNA fragments similar to but distinct from p53: one previously reported, p73, and the other new. We cloned two major splicing variants of the latter gene and named these p51A and p51B (a human homologue of rat Ket). The p51A gene encodes a 448-amino-acid protein with a molecular weight of 50.9 kDa; and p51B, a 641-amino-acid protein with a molecular weight of 71.9 kDa. In contrast with the ubiquitous expression of p53, expression of p51 mRNA was found in a limited number of tissues, including skeletal muscle, placenta, mammary gland, prostate, trachea, thymus, salivary gland, uterus, heart and lung. In p53-deficient cells, p51A induced growth-suppression and apoptosis, and upregulated p21waf-1 through p53 regulatory elements. Mutations in p51 were found in some human epidermal tumors.

A novel class of mosquitocidal delta-endotoxin, Cry19B, encoded by a Bacillus thuringiensis serovar higo gene

Partially digested HincII fragments of DNA from a mosquitocidal strain of Bacillus thuringiensis serovar higo were cloned into pBluescript II SK(+) and propagated in Escherichia coli. Recombinant cells were screened immunologically for the production of parasporal inclusion antigens. One E. coli clone harboring a recombinant plasmid exhibited larvicidal activity to Culex pipiens molestus, but not to Anopheles stephensi. Hybridization experiments revealed that the gene of the toxin protein is located on a 110 kb plasmid of B. thuringiensis serovar higo. Sequence analysis detected an open reading frame of 2046 nucleotides encoding a polypeptide of 682 amino acid residues with a predicted molecular weight of 78,467. The gene encoded five block regions commonly conserved in the insecticidal protein genes of B. thuringiensis. Amino acid sequence of the 78 kDa protein shared 49% identity and 56% similarity with that of the Cry19A protein from B. thuringiensis serovar jegathesan. A new class of delta-endotoxin protein, designated Cry19B, was established on the basis of this protein.

Characterization of mosquito larvicidal parasporal inclusions of a Bacillus thuringiensis serovar higo strain

The parasporal inclusion proteins of the type strain of Bacillus thuringiensis serovar higo (H44), that have moderate mosquitocidal activity, were characterized. The purified parasporal inclusions, spherical in shape, were examined for activity against the two mosquito species, Culex pipiens molestus and Anopheles stephensi and the moth-fly, Telmatoscopus albipunctatus. The LC50 values of the inclusion for the two mosquitoes were 3.41 and 0.15 microgram.ml-1, respectively. No mortality was shown for T. albipunctatus larvae by the inclusions at concentrations up to 1 mg ml-1. Solubilized parasporal inclusions exhibited no haemolytic activity against sheep erythrocytes. Parasporal inclusions consisted of eight proteins with molecular masses of 98, 91, 71, 63, 59, 50, 44 and 27 kDa. Of these, the 50 and 44 kDa proteins were the major components. Analysis with immunoblotting revealed that, among several inclusion proteins of B. thuringiensis serovar israelensis, only two proteins of 130 kDa and 110 kDa reacted weakly with antibodies against higo proteins. N-terminal amino acid sequences of the 98, 91, and 71 kDa proteins showed 85-100% identity to those of the two established Cry protein classes, Cry4A and Cry10A.

delta-Endotoxin proteins associated with spherical parasporal inclusions of the four Lepidoptera-specific Bacillus thuringiensis strains

Four Lepidoptera-specific reference strains of Bacillus thuringiensis, belonging to serovars sumiyoshiensis (H3a:3d), fukuokaensis (H3a:3d:3e), darmstadiensis (H10a:10b) and japonensis (H23), which produce spherical parasporal inclusions, were examined for comparative characterization of delta-endotoxins. SDS-PAGE profiles of the alkali-solubilized parasporal inclusions revealed the presence of single major protein bands of 130 kDa in the four strains. Chymotrypsin and trypsin treatment of the proteins gave profiles different from those of the strains HD-1 (serovar kurstaki, H3a:3b:3c) and T84 A1 (serovar sotto, H4a:4b). Also, minor variations were observed in proteolysis profiles among the four strains. The LC50 values of purified parasporal inclusions for the silkworm (Bombyx mori) larvae were 7.35, 6.45, 3.08 and 2.63 micrograms g-1 diet, respectively, showing that their toxicity levels were 5-15 times lower than that of the strain HD-1 (0.49 microgram g-1 diet). Analysis by immunodiffusion and immunoblotting with polyclonal antisera revealed that parasporal inclusion proteins of the four strains are highly related, whereas they shared few or no common antigens with those of the strains HD-1, T84 A1 and Buibui (serovar japonensis).

2-HEMA-free dentin bonding system to prevent contraction gap

The effects of 2-hydroxyethyl methacrylate (2-HEMA) both in the primer and in the commercial dentin bonding agent on the efficacy of the dentin bonding system was evaluated by measuring the polymerization contraction gap width of a commercial resin composite restored in a cylindrical dentin cavity prepared in an extracted human molar. Contraction gap formation was prevented in the group of the EDTA-conditioning followed by glyceryl mono-methacrylate, ethylene glycol and 1,6-hexanediol priming regardless of the 2-HEMA content in the dentin bonding agent containing 10-methacryloxydecyl dihydrogen phosphate. However, gap formation could not be prevented completely by the 2-HEMA priming. Therefore, it was possible to conclude that 2-HEMA was neither essential in the primer nor in the dentin bonding agent because of its low bonding efficacy and the resulting side effects on skin tissue as a delayed allergic reaction.

A novel isolate of Bacillus thuringiensis serovar leesis that specifically exhibits larvicidal activity against the moth-fly, Telmatoscopus albipunctatus

A soil isolate designated 88-KO-14-45, belonging to Bacillus thuringiensis serovar leesis (H33), exhibited larvicidal activity against the moth-fly, Telmatoscopus albipunctatus (Diptera: Psychodidae), but not for larvae of the culicine and aedine mosquitoes and Lepidoptera. Purified parasporal inclusions had an LC50 value of 5.78 micrograms/ml for the larval moth-fly, but gave no mortality against larvae of Culex pipiens molestus (Diptera: Culicidae) at protein concentrations up to 10 mg/ml. Electron microscopic observations revealed that the parasporal inclusions are homogeneous round-shaped bodies enclosed with thick, electron dense envelopes. Haemolytic activity against sheep erythrocytes was not detected in the solubilized inclusions. SDS-PAGE showed that the inclusions are composed of 72, 68, 56 and 30 kDa proteins. Immunologically, these proteins were unrelated to the inclusion proteins of B. thuringiensis serovar israelensis, while a 70 kDa protein of the strain 73-E-10-2 (B. thuringiensis serovar darmstadiensis) was seroactive to antibodies against proteins of 88-KO-14-45.

Purification and characterization of an isomaltotriose-producing endo-dextranase from a Fusarium sp

An isomaltotriose-producing endo-dextranase was simply purified from cell-free culture broth of a Fusarium sp. by ethanol fractionation and consecutive column chromatographies using DEAE-Toyopearl and Bio-Gel P-100. The purified enzyme was judged to be homogeneous on PAGE and SDS-PAGE as well as isoelectric focusing. The molecular mass of the enzyme was estimated to be about 69 kDa by SDS-PAGE. The enzyme is an acidic protein with a pI of 4.6. The optimum pH and temperature were pH 6.5 and 35 degrees C, respectively. The enzyme was completely stable over the range of pH 4.5-11.8 at 4 degrees C for 24 h and at temperatures below 45 degrees C. Inactivation of the enzyme was found to be partial with 5 mM Cu2+, being about 70% inhibition and complete with 5 mM of Fe3+, Hg2+, Ag+ or NBS. The enzyme split dextran in an endo-lytic action to produce a large amount of isomaltotriose and a slight amount of isomaltose and glucose. The anomeric configurations of the reaction products formed by the enzyme were alpha-form, indicating that the alpha-glycoside linkages in the substrate are retained. The final yield of isomaltotriose from dextran T-2000 was about 62%.

Larvicidal toxicity of Japanese Bacillus thuringiensis against the mosquito Anopheles stephensi

Japanese isolates of Bacillus thuringiensis were screened for larvicidal activity against the mosquito Anopheles stephensi, the urban malaria vector of the Indian subcontinent. Among more than 30 strains identified, larvicidal activity causing > 80% mortality in 72 h was demonstrated for 41/1449 (2.8%) isolates. The majority of strains and isolates (97.2%) exhibited little or no larvicidal activity. Anopheles-active strains belonged to more than 12 H serotypes, especially H3ade (serovar fukuokaensis) and H44 (serovar higo). SDS-PAGE profiles of inclusion proteins showed 4 distinct types among 6 active strains examined. The most active Japanese isolates were H20 strain 89-T-34-14 (LC50 4.4 micrograms/ml) and H44 serovar higo strain 74-E-45-24 (LC50 7.6 micrograms/ml), respectively, 13-fold and 23-fold less active than the international standard H14 serovar israelensis (LC50 0.33 microgram/ml).

Investigation of mosquito-specific larvicidal activity of a soil isolate of Bacillus thuringiensis serovar canadensis

The LC50 value of alkali-solubilized parasporal inclusion proteins of a Diptera-specific strain, belonging to Bacillus thuringiensis serovar canadensis, was 2.4 microg/ml for larvae of the mosquito, Aedes aegypti. A significant loss in larvicidal activity occurred when solubilized inclusion proteins were treated with A. aegypti larval gut extract, silkworm (Bombyx mori) larval gut juice, and the proteinase K. Approximately 90% of the larvicidal activity was destroyed upon treatment with proteases in 30 min. The parasporal inclusion was composed of major proteins of 65, 53, and 28 kDa and some other minor proteins. Proteolysis profiles showed that the 65-kDa major protein is highly sensitive to proteases. Purification experiments with DEAE-Toyopearl column chromatography revealed that the 65-kDa protein is responsible for the mosquitocidal activity of this strain. The LC50 value of the purified protein was 5.4 microg/ml.

Modulation of intracellular protein degradation by SSB1-SIS1 chaperon system in yeast S. cerevisiae

In prokaryotes, DnaK-DnaJ chaperon is involved in the protein degradation catalyzed by proteases La and ClpA/B complex as shown in E. coli. To extend this into eukaryotic cells, we examined the effects of hsp70 genes, SSA1 and SSB1, and DnaJ genes, SIS1 and YDJ1, on the growth of proteasome subunit mutants of the yeast S. cerevisiae. The results identified SSB1 and SIS1 as a pair of chaperon genes specifically involved in efficient protein turnover in the yeast, whose overexpression suppressed the growth defects caused by the proteasome mutations. Moreover, a single amino acid substitution in the putative peptide-binding site of SSB1 protein profoundly enhanced the suppression activity, indicating that the activity is mediated by the peptide-binding activity of this chaperon. Thus SSB1, with its partner DnaJ, SIS1, modulates the efficiency of protein turnover through its chaperon activity.

A high homology exists in N-terminal amino acid sequences of delta-endotoxins between Lepidoptera-specific and Coleoptera-specific Bacillus thuringiensis strains

The 130 kDa parasporal inclusion proteins of the Lepidoptera-specific Bacillus thuringiensis reference strains for four H serovars were examined for sequences of 14 N-terminal amino acids. The four sequences fell into a single category, MNRNNQNEYEVIDA, and were dissimilar to any of the established sequences for Lepidoptera- and/or Diptera-killing crystal proteins. They were highly related to the reported sequence of the 130 kDa protein of the strain Buibui (serovar japonensis), which is specific for scarabaeid coleopterans.

Identification of flagellar (H) antigenic subfactors in Bacillus thuringiensis H serotypes 10, 18 and 24 isolated in Japan

A total of 95 Bacillus thuringiensis strains isolated from Japan and belonging to H serotypes 10, 18 and 24, were examined for their H antigenic subfactors. Of 84 H serotype 10 isolates, 83 were identified as the H serotype 10a: 10b (serovar darmstadiensis) and only one isolate was assigned to the H serotype 10a: 10c (serovar londrina). Among five isolates belonging to the H serotype 18, three were allocated to the H serotype 18a: 18b (serovar kumamotoensis), while two isolates did not react to antisera against the two known H antigenic subfactors, 18b and 18c. All of the six H serotype 24 isolates were assigned to the H serotype 24a: 24b (serovar neoleonensis).

Larvicidal activity of Bacillus thuringiensis natural isolates; indigenous to Japan, against two nematoceran insect pests occurring in urban sewage environments

A total of 1449 Bacillus thuringiensis strains, indigenous to Japan, were screened for larvicidal activity against two nematoceran insect pests, the mosquito, Culex pipiens molestus (Culicidae), and the moth-fly, Telmatoscopus albipunctatus (Psychodidae). Mosquito specific strains were abundant in H serotypes 3abc (serovar kurstaki), 3ade (fukuokaensis), 4ac (kenyae), 7 (aizawai), 11ac (kyushuensis) and 29 (amagiensis), while moth-fly specific strains were predominantly found in H serotype 17 (tohokuensis). Strains toxic to both insects were most frequently detected in H serotypes 10 (darmstadiensis) and 17/27. Seven selected B. thuringiensis strains were highly toxic to Culex and/or Telmatoscopus. There was a diversity in SDS-PAGE profiles of inclusion proteins of these strains.

CDNA cloning of p112, the largest regulatory subunit of the human 26s proteasome, and functional analysis of its yeast homologue, sen3p

The 26S proteasome is a large multisubunit protease complex, the largest regulatory subunit of which is a component named p112. Molecular cloning of cDNA encoding human p112 revealed a polypeptide predicted to have 953 amino acid residues and a molecular mass of 105,865. The human p112 gene was mapped to the q37.1-q37.2 region of chromosome 2. Computer analysis showed that p112 has strong similarity to the Saccharomyces cerevisiae Sen3p, which has been listed in a gene bank as a factor affecting tRNA splicing endonuclease. The SEN3 also was identified in a synthetic lethal screen with the nin1-1 mutant, a temperature-sensitive mutant of NIN1. NIN1 encodes p31, another regulatory subunit of the 26S proteasome, which is necessary for activation of Cdc28p kinase. Disruption of the SEN3 did not affect cell viability, but led to temperature-sensitive growth. The human p112 cDNA suppressed the growth defect at high temperature in a SEN3 disruptant, indicating that p112 is a functional homologue of the yeast Sen3p. Maintenance of SEN3 disruptant cells at the restrictive temperature resulted in a variety of cellular dysfunctions, including defects in proteolysis mediated by the ubiquitin pathway, in the N-end rule system, in the stress response upon cadmium exposure, and in nuclear protein transportation. The functional abnormality induced by SEN3 disruption differs considerably from various phenotypes shown by the nin1-1 mutation, suggesting that these two regulatory subunits of the 26S proteasome play distinct roles in the various processes mediated by the 26S proteasome.

Functional activation of the egr-1 (early growth response-1) gene by hydrogen peroxide

The redox-based regulation of gene expression is one of the fundamental mechanisms of cellular functions, and hydrogen peroxide seems to act as an intracellular second messenger of signal transduction of cytokines. Hydrogen peroxide at non-toxic doses induced the accumulation of mRNA for the early growth response-1 (egr-1) gene in mouse osteoblastic cells. The Egr-1 protein is a transcription factor that binds the GCGGGGGCG sequence and contains a zinc-finger structure that is essential for DNA binding. Egr-1 protein is sensitive to oxidative stress and loses specific DNA-binding activity when exposed to high levels of oxidative stress. Incubating cells with hydrogen peroxide at about 50 microM, however, increased the accumulation of Egr-1 protein, and the Egr-1 product seemed to be functional, judging by its binding activity to the GCGGGGGCG sequence and its ability to activate the chloramphenicol acetyltransferase reporter gene under the control of the human thymidine kinase enhancer containing the Egr-1 binding sequence. It was reported that the activity of Egr-1 protein as a transcription factor was negatively regulated by active oxygens. However, with appropriate concentrations of active oxygen, its capacity to bind a specific DNA sequence and to enhance the transcriptional activity of target genes is thought to be elevated.