[Show abstract][Hide abstract] ABSTRACT: We identified the biosynthetic gene clusters of the siderophore nocobactin NA. The nbt clusters, which were discovered as genes highly homologous to the mycobactin biosynthesis genes by the genomic sequencing of Nocardia farcinica IFM 10152, consist of 10 genes separately located at two genomic regions. The gene organization of the nbt clusters and the predicted functions of the nbt genes, particularly the cyclization and epimerization domains, were in good agreement with the chemical structure of nocobactin NA. Disruptions of the nbtA and nbtE genes, respectively, reduced and abolished the productivity of nocobactin NA. The heterologous expression of the nbtS gene revealed that this gene encoded a salicylate synthase. These results indicate that the nbt clusters are responsible for the biosynthesis of nocobactin NA. We also found putative IdeR-binding sequences upstream of the nbtA, -G, -H, -S, and -T genes, whose expression was more than 10-fold higher in the low-iron condition than in the high-iron condition. These results suggest that nbt genes are regulated coordinately by IdeR protein in an iron-dependent manner. The ΔnbtE mutant was found to be impaired in cytotoxicity against J774A.1 cells, suggesting that nocobactin NA production is required for virulence of N. farcinica.
Journal of bacteriology 01/2011; 193(2):441-8. DOI:10.1128/JB.00897-10 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 8-Amino-2,8-dideoxy-beta-KDO is a well-known inhibitor of CMP-KDO synthetase involved in the biosynthesis of lipopolysaccharide (LPS), an essential component of the outer membrane of gram-negative bacteria. Chemical modification of the hydroxyl groups of 8-amino-2,8-dideoxy- beta-KDO proved that they play a crucial role in CMP-KDO synthetase inhibition.
Letters in Drug Design & Discovery 07/2008; 5(5):336-339. DOI:10.2174/157018008784912117 · 0.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We compared the results of two typing methods for 678 strains of methicillin-resistant Staphylococcus aureus and methicillin-susceptible S. aureus. PCR-restriction fragment length polymorphism typing of the coagulase gene was a more reliable method than coagulase serotyping from the viewpoint of arbekacin resistance.
[Show abstract][Hide abstract] ABSTRACT: We constructed a pair of Nocardia-Escherichia coli shuttle vectors, pNV18 and pNV19, by combining the mycobacterial plasmid pAL5000 with the E. coli vector pK18 or pK19. These vectors have a number of useful features, including small size (4.4 kb), a multiple cloning site, and blue/white selection. To our knowledge, pNV18 and pNV19 are the first cloning vectors for practical use in Nocardia spp.
Japanese journal of infectious diseases 03/2007; 60(1):45-7. · 1.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 3-Deoxy-D-manno-octulosonate cytidyltransferase (CMP-KDO synthetase) is involved in the biosynthesis of lipopolysaccharide (LPS) which is an essential component of the outer membrane of gram-negative bacteria. New CMP-KDO synthetase inhibitors, 8-substituted derivatives of 2-deoxy-beta-KDO (2) have been prepared. Compounds 8, 11, 15 and 16 in which the 8-hydroxyl group of 2 is replaced by guanidine, di(carbamoylethyl)amino, p-methoxy- or p-nitro-benzyloxycarbonylamino, respectively affect moderately the CMP-KDO synthetase activity.
Natural Product Research 05/2006; 20(4):361-70. DOI:10.1080/14756360500183699 · 0.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A total of 472 clinical strains of methicillin-resistant Staphylococcus aureus (MRSA) isolated in Japan between 1979 and 2000 were investigated for resistance to 8 aminoglycosides, 4 aminoglycoside-modifying enzyme gene profiles, and AluI-restriction fragment length polymorphism of the coagulase gene determined by polymerase chain reaction assay. The majority of MRSA strains tested belonged to 4 groups based on coa-RFLP: L21, L22, L31, and M22. About 90% of recent isolates belonged to type L21, indicating the spread of a specific type of MRSA in Japan. Of the type L21 strains, 41.9% included the aac(6')/aph(2") gene, which was one of the risk factors of arbekacin (ABK) resistance, but only 5.5% were resistant to ABK. In contrast, all of the type M22 strains carried aac(6')/aph(2") and 70.1% showed ABK resistance. Among the other types, less than 20% of strains showed ABK resistance. These results suggested that ABK has maintained potent activity. If the predominance of type L21 continues, there will be no progression to ABK resistance in MRSA. However, it may be necessary to monitor the trends in type M22 continuously.
The Journal of Antibiotics 05/2006; 59(4):229-33. DOI:10.1038/ja.2006.32 · 1.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A clinical isolate (designated PRC104) of methicillin-resistant Staphylococcus aureus was discovered with a novel aminoglycoside resistance profile, including unusually high resistance (MIC 128 microg/ml) to arbekacin (an effective anti-MRSA drug in Japan). We characterized the activity and gene of its bifunctional aminoglycoside-modifying enzyme, AAC(6')/APH(2"), in comparison with those of a regular one that has been known as the critical resistance basis to both gentamicin and arbekacin in methicillin-resistant Staphylococcus aureus. The aac(6')/aph(2") gene of strain PRC104 contained a single base alteration at a novel site (G1126A) resulting in one amino acid substitution (S376N) in the phosphorylation catalytic motif. The phosphorylation activity of the PRC104 enzyme was enhanced for arbekacin and reduced for gentamicin. Both strain PRC104 and S. aureus RN4220 containing the cloned gene were identical in terms of the substrate specificity of the enzyme as well as the aminoglycoside resistance profile, although both mRNA and aminoglycoside resistance levels were markedly high in strain PRC104. Therefore, the cloned aac(6')/aph(2") gene may represent the molecular basis for the novel aminoglycoside modification capability as well as novel aminoglycoside resistance profile of S. aureus PRC104.
The Journal of Antibiotics 11/2004; 57(10):679-86. DOI:10.7164/antibiotics.57.679 · 1.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We found that 12-O-tetradecanoylphorbol-13-acetate (TPA) promoted anchorage-independent growth but did not affect anchorage-dependent growth of MIA PaCa-2 human pancreatic carcinoma cells. TPA markedly activated mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase in an anchorage-independent manner. Two protein kinase C (PKC) isoforms, conventional PKC (cPKC) and novel PKC (nPKC), but not apical PKC, translocated from the cytosolic to the particulate fraction upon TPA treatment. To identify the PKC isoforms involved in the regulation of anchorage-independent growth, four PKC isoforms (alpha, delta, epsilon, and zeta) were forced to be expressed in MIA PaCa-2 cells with an adenovirus vector. Overexpression of nPKCdelta or nPKC epsilon activated MAPK and promoted anchorage-independent growth. Overexpression of cPKCalpha alone did not influence anchorage-independent growth but lowered the concentration of TPA that was required to enhance such growth. Expression of constitutively active MAPK kinase-1 (MEK1) also promoted anchorage-independent growth. Furthermore, PKC inhibitors or an MEK inhibitor completely suppressed both TPA-induced activation of MAPK and promotion of anchorage-independent growth, but a cPKC-selective inhibitor partially suppressed TPA-induced promotion of the growth. Based on these results, we suggest that MAPK activation, mediated by certain isoforms of PKC, plays a part in oncogenic growth of MIA PaCa-2 cells. In summary, our data indicated that specific inhibitors of the cPKC and nPKC signaling pathway might be selective anti-oncogenic growth agents for some types of human pancreatic cancer.
[Show abstract][Hide abstract] ABSTRACT: PKC is activated on the cell membrane by phospholipids, thereby transducing signals to intracellular pathways. We provide here another function of PKC, namely, regulating cell cycle by interaction with the cyclin E/cdk2/p21 complex. Among the 10 isoforms of PKC, PKCeta is predominantly expressed in squamous cell epithelia and induces terminal differentiation of keratinocytes. PKCeta that is endogenously expressed or overexpressed was found to associate with the cyclin E/cdk2/p21 complex in keratinocytes of mice and humans. Requirement of a possible adaptor protein to the binding was suggested by the reconstitution of PKCeta and the cyclin E/cdk2/p21 complex which were prepared from human keratinocytes or Sf9 insect cells. Colocalization of PKCeta with cdk2 and cyclin E was observed in the cytoplasm, particularly in the perinuclear region. p21 was phosphorylated in the complex in a PKC-activator dependent manner. Association of PKCeta with cdk2 resulted in marked inhibition of cdk2-kinase activity when measured by phosphorylation of Rb. Dominant negative PKCeta associated with the cyclin E/cdk2/p21 complex, but caused a little inhibition of cdk2 kinase activity. Among the known regulatory mechanisms of cdk2 activity, dephosphorylation of Thr160 was demonstrated. Oncogene (2000) 19, 6334 - 6341.
[Show abstract][Hide abstract] ABSTRACT: The introduction and expression of a foreign gene provide a powerful tool for investigating functions and regulation of a gene of interest; however, keratinocytes have a major drawback in that foreign genes are hardly transfected by conventional methods and stable transformants are most difficult to establish in normal keratinocytes with a limited short life span. To overcome these problems, we used an adenovirus vector, Ax, developed by Saito et al, which yields desired recombinant viruses at an efficiency about 100-fold that of conventional methods, and by which genes are expressed at a high level under the control of a composite CAG promoter. We established Ax vectors carrying various isoforms of protein kinase C (PKC). Using these vectors, we found that the eta and delta isoforms of PKC, but not the alpha and zeta isoforms, mediate terminal differentiation in normal human keratinocytes. These Ax-vectors are also applicable to organ culture of mouse embryos. Advantages and disadvantages of adenovirus vectors and their use for keratinocyte biology are reviewed.
[Show abstract][Hide abstract] ABSTRACT: 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.
Japanese journal of cancer research: Gann 12/1998; 89(11):1126-33. DOI:10.1111/j.1349-7006.1998.tb00507.x
[Show abstract][Hide abstract] ABSTRACT: 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 α, δ, η, and ζ 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 α, δ, and η isoforms. Overexpression of the η isoform inhibited the growth of keratinocytes of humans and mice in a dose (multiplicity of infection [MOI])-dependent manner, leading to G
arrest. The η-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 η-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 η isoform endogenously, i.e., in human and mouse keratinocytes but not in human and mouse fibroblasts or COS1 cells. A dominant-negative η isoform counteracted the induction of transglutaminase 1 by differentiation inducers such as a phorbol ester, 1α,25-dihydroxyvitamin D
, and a high concentration of Ca
. Among the isoforms examined, the δ isoform also inhibited the growth of keratinocytes and induced transglutaminase 1, but the α and ζ isoforms did not. These findings indicate that the η and δ isoforms of PKC are involved crucially in squamous cell differentiation.
[Show abstract][Hide abstract] ABSTRACT: We found that dimethyl-sulfoxide (DMSO) at concentrations of 2.5% induced apoptosis in SV40-immortalized human keratinocytes, while normal keratinocytes were arrested at the boundary of G1/S phase under the same conditions. DMSO-induced apoptosis in SV-40 immortalized keratinocytes was not associated with change in phosphorylated state of the retinoblastoma susceptibility gene. When SV40-immortalized cells were treated with 2.5% DMSO, dissociation of the complex was observed by immunoblotting of SV40 T antigen from immunoprecipitated p53 protein fraction.
Cancer Letters 12/1996; 108(2):185-93. DOI:10.1016/S0304-3835(96)04408-4 · 5.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have found that the growth of normal human keratinocytes, grown in serum-free medium, was significantly stimulated by the antisense oligonucleotide of retinoblastoma susceptibility gene (Rb). Normal human keratinocytes were exposed to phosphorothionate oligonucleotides which were complementary to translation initiation codon of Rb gene. The growth of keratinocytes was enhanced by the antisense, but not the sense, oligonucleotide of Rb gene in a dose-dependent manner from 1 to 10 microM. The Rb antisense oligonucleotide, however, did not result in any appreciable change in transcription of the gene when examined by reverse-transcription polymerase chain reaction (RT-PCR) analysis or in the protein expression and the phosphorylation pattern when examined by immunoprecipitation and Western blotting.
[Show abstract][Hide abstract] ABSTRACT: We found that transforming growth factor beta 1 (TGF-beta 1) and TGF-beta 2 inhibited the growth of normal human keratinocytes and their SV40-transformed counterpart in a dose dependent manner. Both normal and SV-40 transformed keratinocytes accumulated in G1 when treated with TGF-beta s. The hyperphosphorylated form of Rb gene product (RB) was reduced by TGF-beta s in normal keratinocytes. In contrast, phosphorylation of RB was not essentially affected in SV-40 transformed cells. This uncoupling of growth kinetics and phosphorylation states of RB in SV-40 transformed keratinocytes suggests that RB is not the primary target of action for TGF-beta s and that additional factors or pathways may be involved in mechanisms of the growth inhibition.
Biochemical and Biophysical Research Communications 07/1994; 201(2):673-81. DOI:10.1006/bbrc.1994.1753 · 2.30 Impact Factor