Biomedical subjects

H Takaku

Publications and source records attributed to H Takaku.

At least 19 recordsLinked to original sources

PubMed2006

Gene silencing by the tRNA maturase tRNase ZL under the direction of small-guide RNA.

We have been developing a unique system for the downregulation of a gene expression through cutting a specific mRNA by the long form of tRNA 3'-processing endoribonuclease (tRNase Z(L)) under the direction of small-guide RNA (sgRNA). However, the efficacy of this system and the involvement of tRNase Z(L) in the living cells were not clear. Here we show, by targeting the exogenous luciferase gene, that the efficacy of the sgRNA/tRNase Z(L) method can become comparable to that of the RNA interference technology and that the gene silencing is owing to tRNase Z(L) directed by sgRNA not owing to a simple antisense effect. We also show that tRNase Z(L) together with sgRNA can downregulate expression of the endogenous human genes Bcl-2 and glycogen synthase kinase-3beta by degrading their mRNAs in cell culture. Furthermore, we demonstrate that a gene expression in the livers of postnatal mice can be inhibited by an only seven-nucleotide sgRNA. These data suggest that sgRNA might be utilized as therapeutic agents to treat diseases such as cancers and AIDS.

Animals↗

PubMed2006

Gene silencing of virus replication by RNA interference.

Small interfering RNAs (siRNAs) are as effective as long double-stranded RNAs (dsRNAs) at targeting and silencing genes by RNA interference (RNAi). siRNAs are widely used for assessing gene function in cultured mammalian cells or early developing vertebrate embryos. They are also promising reagents for developing gene-specific therapeutics. The specific inhibition of viral replication is particularly well suited to RNAi, as several stages of the viral life cycle and many viral and cellular genes can be targeted. The future success of this approach will depend on the recent advances in siRNA-based clinical trials.

Animals↗

PubMed2003

Specific HIV-1 env gene silencing by small interfering RNAs in human peripheral blood mononuclear cells.

RNA interference (RNAi) is triggered by the presence of a double-stranded RNA (dsRNA) in the cell, and results in the silencing of homologous gene expression by the specific degradation of an mRNA containing the same sequence. dsRNA-mediated RNAi can be used in a wide variety of eucaryotes to induce the sequence-specific inhibition of gene expression. Synthetic 21-23 nucleotide (nt) small interfering RNAs (siRNAs) with 2-nt 3' overhangs were recently found to mediate efficient sequence-specific mRNA degradation in mammalian cells. Here, we show that synthetic siRNAs targeted against the viral structural Env proteins encoded by HIV-1 can specifically suppress the expression of HIV-1 genes. The siRNA-mediated RNAi also had advantages over antisense RNA-mediated inhibition, in terms of both the ease of designing effective antiviral agents and their potency. Especially, our best env-specific siRNAs, E7145 targeted to the central region of the V3 loop and E7490 targeted to the CD4 binding site of conserved regions on gp120, significantly inhibited the HIV-1 gene expression. Furthermore, E7145 and E7490 were effective against HIV-1(NL4-3) replication in PBMCs for a relatively long time (14 days). Therefore, the use of synthetic siRNAs provides a simple, rapid, and cost-effective tool for new anti-HIV-1 gene therapeutics.

Animals↗

PubMed2001

Two basic regions of NCp7 are sufficient for conformational conversion of HIV-1 dimerization initiation site from kissing-loop dimer to extended-duplex dimer.

Nucleocapsid (NC) protein possesses nucleotide-annealing activities, which are used in various processes in retroviral life cycle. As conserved characters, the NC proteins have one or two zinc fingers of CX(2)CX(4)HX(4)C motif surrounded by basic amino acid sequences. Requirement of the zinc fingers for the annealing activities of NC protein remains controversial. In this study, we focused the requirement in the process of maturation of dimeric viral RNA. Discrimination between immature and mature dimers of synthetic RNA corresponding to the dimerization initiation site of human immunodeficiency virus type 1 (HIV-1) genomic RNA was performed based on their Mg(2+)-dependent stability in gel electrophoreses and on their distinct signal pattern from NMR analysis of imino protons. Chaperoning activity of the HIV-1 NC protein, NCp7, and its fragments for maturation of dimeric RNA was investigated using these experimental systems. We found that the two basic regions flanking the N-terminal zinc finger of NCp7, which are connected by two glycine residues instead of the zinc finger, were sufficient, although about 10 times the amounts of peptide were needed in comparison with intact NCp7. Further, it was found that the amount of basic residues rather than the amino acid sequence itself is important for the activity. The zinc fingers may involve the binding affinity and/or such a possible specific binding of NCp7 to dimerization initiation site dimer that leads to the maturation reaction.

Amino Acid Sequence↗

PubMed2001

Ray38p, a homolog of a purine motif triple-helical DNA-binding protein, Stm1p, is a ribosome-associated protein and dissociated from ribosomes prior to the induction of cycloheximide resistance in Candida maltosa.

Cycloheximide (CYH) resistance in Candida maltosa is dependent on the induction of a ribosomal protein, Q-type L41, the 56th residue of which is glutamine, not proline as in ordinary P-type L41. We found that a 38-kDa protein in a wild-type C. maltosa ribosomal fraction became undetectable upon CYH treatment but detectable again with the establishment of CYH resistance by the induction of Q-type L41. We cloned a gene coding for this protein and named it RAY38 (ribosome-associated protein of yeast). Ray38p is a homolog of a purine motif triple-helical DNA-binding protein, Stm1p, and has a putative RNA-binding motif RGG. The ribosome-associated Ray38p was phosphorylated at serine and threonine residues, and Ray38p that was dissociated from ribosome by CYH treatment was highly phosphorylated in threonine residues. A ray38 null mutant recovered faster from CYH-caused growth stasis than the wild-type strain, suggesting that the dissociation of Ray38p from ribosome facilitates the induction of CYH resistance in C. maltosa.

Amino Acid Motifs↗

PubMed2001

Synthesis and structure-activity relationship of diarylamide derivatives as selective inhibitors of the proliferation of human coronary artery smooth muscle cells.

A series of diarylamide derivatives were synthesized and evaluated for their inhibitory activities against human coronary artery smooth muscle cells (SMCs) and human coronary artery endothelial cells (ECs). Compound 2w was superior to the lead compound, Tranilast, in terms of the potency of the activity and cell selectivity.

Amides↗

PubMed2001

Inhibition of the human chemokine receptor CXCR4 by antisense phosphorothioate oligodeoxyribonucleotides.

The CXC chemokine receptor CXCR4/fusion, a major coreceptor for the T-cell line T-tropic (X4) HIV-1 virus, plays a critical role in T-tropic virus fusion and entry into permissive cells. In the present study, we describe the effects of an antisense phosphorothioate oligodeoxyribonucleotide (anti-S-ODN) on the inhibition of CXCR4 gene expression in X4 HIV-1 infected HeLa-CD4 cells, to find more efficacious therapeutic possibilities for human immunodeficiency virus type 1 (HIV-1) infection. The naked antisense phosphorothioate oligodeoxyribonucleotide (anti-S-ODN-1), containing the AUG initiation codon at the center of the oligodeoxyribonucleotide, showed a slightly higher inhibitory effect on HIV-1 gag p24 production among all sequences tested. We also examined the concomitant use of a basic peptide transfection reagent, nucleosomal histone proteins (RNP), for the delivery of the anti-S-ODN-1. The anti-S-ODN-1 encapsulated with RNP had higher inhibitory effects on p24 products than the naked anti-S-ODN-1. When the anti-S-ODN-1 encapsulated with RNP was incubated with HeLa-CD4 cells, the surface levels of this chemokine receptor showed high suppression, indicating sequence-specific inhibition. The activities of unmodified oligodeoxyribonucleotide are effectively enhanced by using a basic peptide, RNP.

CD4 Antigens↗

PubMed2001

Influence of organic solvents on the growth of marine microalgae.

Ninety-six-hour toxicity tests of five organic solvents (methanol, ethanol, acetone, N,N-dimethylformamide [DMF], and dimethyl sulfoxide [DMSO]) on nine species of marine microalgae (Bacillariophyceae; Skeletonema costatum, and Chaetoceros calcitrans, Prasinophyceae; Tetraselmis tetrathele, Haptophyceae; Isochrysis galbana and Pavlova lutheri, Dinophyceae; Prorocentrum minimum, Raphidophyceae; Heterosigma akashiwo, Euglenophyceae; Eutreptiella sp., Chlorophyceae; Dunaliella tertiolecta) were conducted. For D. tertiolecta, T. tetrathele, I. galbana, and P. lutheri, methanol was the least toxic solvent. For S. costatum, C. calcitrans and Eutreptiella sp., DMSO was the least toxic solvent. For Heterosigma akashiwo, DMF was the least toxic solvent. In general, solvent toxicity was ethanol > methanol or acetone > DMF > DMSO. In relation to sensitivity of the microalgae to solvents, D. tertiolecta and T. tetrathele were lower in sensitivity, and Eutreptiella sp. and H. akashiwo were higher in sensitivity than the other species. The no observed effect concentration (NOEC) of acetone, DMF, and DMSO were higher than for ethanol and methanol. Acetone, DMF, and DMSO were suitable for carrier solvents used in toxicity test of water-insoluble chemicals. Excellent regression between logEC(50) and logNOEC was obtained (logNOEC = 1.09 x logEC(50) - 0.84, R(2) = 0.91). This equation indicated that higher toxicity was higher application factor (EC(50)/NOEC) than lower toxicity. All application factors were higher than 0.1.

Dose-Response Relationship, Drug↗

PubMed2001

Antisense therapy of influenza.

The liposomally encapsulated and the free antisense phosphorothioate oligonucleotides (S-ODNs) with four target sites (PB1, PB2, PA, and NP) were tested for their abilities to inhibit virus-induced cytopathogenic effects by a MTT assay using MDCK cells. The liposomally encapsulated S-ODN complementary to the sites of the PB2-AUG initiation codon showed highly inhibitory effects. On the other hand, the inhibitory effect of the liposomally encapsulated S-ODN targeted to PB1 was considerably decreased in comparison with those directed to the PB2 target sites. The liposomally encapsulated antisense phosphorothioate oligonucleotides exhibited higher inhibitory activities than the free oligonucleotides, and showed sequence-specific inhibition, whereas the free antisense phosphorothioate oligonucleotides were observed to inhibit viral absorption to MDCK cells. Therefore, the antiviral effects of S-ODN-PB2-AUG and PA-AUG were examined in a mouse model of influenza virus A infection. Balb/c mice exposed to the influenza virus A (A/PR/8/34) strain at dose of 100 LD(50)s were treated i.v. with various doses (5-40 mg/kg) of liposomally (Tfx-10) encapsulated PB2-AUG or PA-AUG before virus infection and 1 and 3 days postinfection. PB2-AUG oligomer treated i.v. significantly prolonged the mean survival time in days (MDS) and increased the survival rates with a dose-dependent manner. We demonstrate the first successful in vivo antiviral activity of antisense administered i.v. in experimental respiratory tract infections induced with influenza virus A.

Animals↗

PubMed2001

Anti-HIV-1 activity of an antisense phosphorothioate oligonucleotide bearing imidazole and primary amine groups.

We have previously shown that RNA cleaving reagents with imidazole and primary amine groups on the 5'-end of antisense oligodeoxyribonucleotides could site-specifically cleave CpA as the target sequence of the substrate tRNA in vitro. In this study, a RNA cleaving reagent, composed of imidazole and primary amine groups on an antisense phosphorothioate oligonucleotide (Im-anti-s-ODN), was synthesized and evaluated for anti-HIV-1 activity in MT-4 cells. The sequence of the Im-anti-s-ODN was designed to be complementary to the HIV-1 gag-mRNA and to bind adjacent to the CpA cleavage site position. Im-anti-s-ODN encapsulated with the transfection reagent, DMRIE-C, had higher anti-HIV-1 activity than the unmodified antisense phosphorothioate oligonucleotide (anti-s-ODN) at a 2 microM concentration. Furthermore, the Im-anti-ODN encapsulated with DMRIE-C conferred sequence-specific inhibition.

Amines↗

PubMed2001

Inhibition of HIV-1 replication by 5'LTR decoy RNA.

Long terminal repeats (5'-LTR) contain essential enhancer and promoter elements that act as targets for cellular and viral regulatory proteins. The interplay of these cis-acting sequences with specific transcription factors (NF kappa B, Ap1, and Sp1) present in infected cells determines the rate of transcription initiation from the 5'-LTR promoter element, and thus strongly influences the level of viral replication. Furthermore, Tat functions to enhance transcriptional elongation by binding to the trans-activation response element (TAR). These transcriptional factors enhance the transcriptional elongation from the HIV-1 promoter. HIV-1 genomic RNA packaging is a highly specific process involving interactions between the viral Gag precursor and cis acting packaging signals in the 5' leader sequence of HIV-1 genomic RNA. We examined the suppression effect of HIV-1 expression by the decoy RNAs targeted to these HIV-1 transcriptional and packaging regulatory regions. HIV-1 expression was inhibited by the 5'-LTR decoy RNA, and measured by the amount of HIV-1 gag p24 protein, but no inhibition of HIV-1 packaging could be detected.

Animals↗

PubMed2001

Conformational change of dimerization initiation site of HIV-1 genomic RNA by NCp7 or heat treatment.

Dimerization initiation site (DIS) of the human immunodeficiency virus type 1 (HIV-1) genome has been identified as a primary sequence that can form a stem-loop structure with a self-complementary sequence in the loop and a bulge in the stem. A DIS RNA fragment spontaneously forms a kissing dimer and is converted into an extended-duplex dimer by supplement of nucleocapsid protein NCp7. This two-step dimerization reaction can be also executed by a heat treatment instead of the binding proteins. However, it has not identified whether mechanisms of the conformational conversion by two different treatments are identical or not. In the present study, we used a series of DIS RNA oligonucleotides and the conformations of two extended-duplex dimers produced by the two different treatments were compared by the analysis of NMR spectra in the imino proton region. It was found that the effects of the two kinds of treatments are quite similar and the conformations of the two extended-duplex dimers are identical. These findings suggest that the conversion mechanisms DIS RNA by NCp7 and heat treatments are similar.

Base Sequence↗

PubMed2001

Effective inhibition of HIV-1 replication in cultured cells by external guide sequences and ribonuclease.

We examined the suppression effect of HIV-1 expression by cleavage of the HIV-1 RNA gene, using the catalytic RNA subunit RNase P and the 3'-half tRNA [External Guide Sequence (EGS)] in vivo. The vectors were designed to express an anti-HIV EGS, U5, which targets the 5' leader sequence. We constructed an EGS expression vector, that used the tRNA(met) or U6 promoter as an expression cassette for EGS. RNase P cleaves the targeted HIV-1 mRNA when they are in a complex with the EGS. To test the antiviral efficacy of these EGS vectors, we have cotransfected into COS cells with the HIV-1 proviral DNA (pNL4-3 Luc) and the plasmid expressing the EGS from the tRNA(met) or U6 promoter. HIV-1 expression was inhibited by the tRNA-EGS-1 and U6-EGS-1 from the tRNA(met) and U6 promoters, respectively. No difference in the inhibitory effects on HIV-1 expression between the tRNA(met) and U6 promoters could be detected.

Animals↗

PubMed2001

Specific inhibition of HIV-1 gene expression by double-stranded RNA.

RNA interference (RNAi) is phenomenon in which introduced double-stranded RNAs (ds-RNAs) silence gene expression through specific degradation of their cognate mRNAs. RNAi has been observed in a wide variety of organisms and is considered to be a feature of nearly all eukaryotes. The mediators of sequence specific messenger RNA degradation are 21-23 nucleotide small interfering RNAs generated by ribonucleaseIII cleavage from longer dsRNAs. To investigate the potential of dsRNA to interfere with the function of HIV-1 genes, we have designed six longer dsRNAs containing the HIV-1 gag and env genes. Double-stranded RNAs were tested for inhibitory effects using monkey COS cells. In these anti-HIV-1 activity tests, the dsRNAs targeted to the HIV-1 env sequence showed more than 90% anti-HIV-1 efficiency. Our results show that dsRNA interference can be used as a powerful method for the inhibition of HIV-1 gene expression.

Animals↗

PubMed2001

Reverse transcriptional mutagenesis induced by ribonucleoside triphosphate analogue, PTP and its availability for anti-HIV-1 therapy.

The bicyclic pyrimidine analogue, 3,4-dihydro-6H,8H-pyrimido[4,5-c][1,2]oxazin-7-one (P) can base pair with both A and G. The riboside 5'-triphsophate of P (PTP) efficiently induces mutation during in vitro transcription and reverse transcription cycles using a phage promoter. In the present study, we have constructed an in vitro transcription system promoted by the human immunodeficiency virus type 1 (HIV-1) 5'-long terminal repeat (LTR) using HeLa nuclear extract supplemented with HIV-1 Tat protein. Using this system, the effects of mutagenic ribonucleotide analogues were studied.

Anti-HIV Agents↗

PubMed2001

Mutations of p53 in morphologically non-neoplastic mucosa of long-standing ulcerative colitis.

Two cases of ulcerative colitis (UC)-associated carcinoma or dysplasia and morphologically non-neoplastic mucosa with p53 protein overexpression (MNNM-p53OE) were selected. DNA was extracted from the paraffin blocks of these lesions and exons 5 - 8 of the p53 gene were analyzed by PCR and direct sequencing. In addition, mutations in K-ras codon 12 were analyzed by PCR-RFLP methods. MNNM-p53OE was located surrounding and adjoining a coexisting carcinoma and / or dysplasia. A p53 mutation was detected in 12 / 22 (54.5%) MNNM-p53OE samples, 4 / 8 (50%) dysplasia samples and 8 / 8 (100%) carcinoma samples. The p53 mutations detected in MNNM-p53OE were identical to those demonstrated in the adjoining carcinoma and / or dysplasia. No K-ras codon 12 mutation was detected in any of the samples. These results indicate that MNNM-p53OE may share an identical clonal linkage with a coexisting carcinoma and / or dysplasia, and may be an initial and submorphological form of UC-associated neoplasia. Recognition of MNNM-p53OE in biopsy specimens may help to identify patients with UC at risk of developing colorectal carcinoma.

Adult↗

PubMed2001

Heterogeneity of p53 mutational status in intramucosal carcinoma of the colorectum.

The aim of this study was to elucidate whether or not p53 genetic heterogeneity would occur while colorectal carcinoma was limited to the mucosa. Eight cases of endoscopically resected colorectal intramucosal carcinomas were analyzed to determine the p53 gene sequence (exons 5 to 8). Six out of 8 cases showed p53 gene mutations, and in all of them, the mutational status was heterogeneous. In 4 cases, mutated codons were heterogeneous as well. These data indicate that p53 gene alterations in colorectal carcinomas occur and diverge at the stage of intramucosal carcinoma, supporting our previously proposed hypothesis that colorectal carcinomas can be composed of various subclones as regards p53 gene mutation, while the carcinoma is limited to the mucosa, and one of these subclones commences invasion to the submucosa after clonal selection, thus generating a monoclonal invasive carcinoma.

Carcinoma↗

PubMed2001

Inhibitory effect of modified 5'-capped short RNA fragments on influenza virus RNA polymerase gene expression.

We have shown previously that the 5'-capped short phosphodiester RNA fragments, Cap decoy, (Gm 12 nt) are potent inhibitors of influenza virus RNA polymerase gene expression. Here we investigate the modified capped RNA derivative containing phosphorothioate oligonucleotides (Cap decoy) as a potential influenza virus RNA polymerase inhibitor. The modified 5'-capped short phosphorothioate RNA fragments (Gms 12-15 nt) with the 5'-capped structure (m7GpppGm) were synthesized by T7 RNA polymerase. The 5'-capped short RNA fragments (Gms 12-15 nt) were encapsulated in liposome particulates and tested for their inhibitory effects on influenza virus RNA polymerase gene expression in the clone 76 cells. The 12-15 nt long Gms RNA fragments showed highly inhibitory effects. By contrast, the inhibitory effects of the 13 nt long short RNA fragments (Gm 13 nt) were considerably less in comparison with the 5'-capped short phosphorothioate RNA fragments (Gms 12-15 nt). In particular, the various Gms RNA chain lengths showed no significant differences in the inhibition of influenza virus RNA polymerase gene expression. Furthermore, the capped RNA with a phosphorothioate backbone was resistant to nuclease activity. These phosphorothioate RNA fragments exhibited higher inhibitory activity than the 5'-capped short RNA fragments (Gm 12 nt). These decoys may prove to be useful in anti-influenza virus therapeutics.

Animals↗