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M Hijikata

Publications and source records attributed to M Hijikata.

At least 37 records · Page 2Linked to original sources
PubMed2000

Identification of a new human DNA virus (TTV-like mini virus, TLMV) intermediately related to TT virus and chicken anemia virus.

TT virus (TTV) is the only known human virus with single-stranded circular DNA, with a possible but yet unclear relationship to chicken anemia virus (CAV) of the family Circoviridae. Here we report a new human virus resembling TTV and CAV, designated TTV-like mini virus (TLMV). This non-enveloped virus was smaller (< 30 nm) but had a similar density (1.31-1.34 g/ml in CsCl) to TTV, when a TLMV/TTV-coinfected plasma was analyzed. Full-length sequencing revealed that the TLMV genome was a circular DNA comprising 2860 nt (isolate CBD231); significantly shorter than TTV (TA278, 3852 nt) but longer than CAV (CAECUX1, 2319 nt). A strand-specific hybridization assay using oligonucleotide-coated beads suggested TLMV was negative-stranded, like TTV and CAV. In genomic organization, TLMV was similar to both TTV and CAV. The untranslated region of TLMV resembled CAV in that both had direct repeats, whereas the sequence homology was more evident between TLMV and TTV. The predicted ORF1 protein of TLMV was rich in R/W/F residues at its amino terminus; the richness in W was shared by TTV, F by CAV, and R by both. ORF2 proteins of the three viruses had a common motif, WX7HX3CXCX5H. Thus, TLMV is an intermediate between the remotely related TTV and CAV. Since CAV differs much from other circoviruses, it may better be classified together with TTV and TLMV under a new family: we would coin the Paracircoviridae.

Amino Acid Sequence↗
PubMed2000

Full-genome nucleotide sequence of a hepatitis C virus variant (isolate name VAT96) representing a new subtype within the genotype 2 (arbitrarily 2k).

Hepatitis C virus (HCV), a single-stranded RNA virus of the family Flaviviridae, has a wide range of genetic heterogeneity: 6-11 genotypes (or 6 clades) have been known and each genotype comprises multiple subtypes. Here we report the entire nucleotide sequence of an HCV isolate from a patient in Moldova with chronic hepatitis (isolate name VAT96). The genetic organization of VAT96 was, from 5' to 3' ends, 5'UTR (341 nt), polyprotein ORF (9099 nt), 3'UTR (38 nt except for the poly-U and poly-pyrimidine stretch), and X-tail (98 nt). Comparison of the polyprotein amino acid sequence of VAT96 with those of known full-genome isolates assigned VAT96 to the genotype 2 (or clade 2), and further phylogenetic analysis based on a 447-nt sequence that covers part of the C and El regions suggested that VAT96 represents a new subtype within the genotype 2, arbitrarily designated "2k" VAT96 was unique in that it possessed a U residue prior to GCC at the 5' end of its genome while all the other full-genome HCV sequences start with GCC or ACC. In addition, the polyprotein ORF of HCV-VAT96, like HCV-BEBE1 of 2c, encoded several additional amino acids in excess, compared to 2a and 2b sequences. Despite these characteristics that may be unique to VAT96, the 98-nt sequence of the X-tail of VAT96 was highly homologous to those of other isolates with different genotypes so far reported.

3' Untranslated Regions↗
PubMed2000

Full or near full length nucleotide sequences of TT virus variants (Types SANBAN and YONBAN) and the TT virus-like mini virus.

TT virus (TTV) is a common virus and consists of many genotypes and variants. In addition, there exists a virus which both differs greatly from and retains a considerable resemblance to TTV, such as the TTV-like mini virus (TLMV) as we reported previously. Here we report the near full length genomic sequences of 4 isolates of a new variant of TTV (designated YONBAN) along with the full length sequences of 2 isolates of the TTV-SANBAN lineage and 7 isolates of the TLMV species derived from human sera. The TTV-YONBAN sequences showed only about 50% identity at the nucleotide level to those of the prototype TTV (TA278) and to SANBAN, and even less to TLMV. Moreover, the ORF1 of YONBAN lacked the ATG initiation codon which is shared by all the TTV and TLMV isolates so far identified in humans; instead, YONBAN had a Kozak's rule-compatible ACG codon as the candidate initiation site for the ORF1 translation. Nevertheless, the overall genetic structure and the conserved amino acid motifs within the ORF1 and the ORF2 were well shared among the prototype TTV strains, the SANBAN and YONBAN variants, and TLMV. The most conserved nucleotide sequence was found in the noncoding region just upstream from the ORF2, allowing construction of a phylogenetic tree which implied that the TTV genotypes and variants, the TLMV, and chicken anemia virus could be coclassified under a superfamily for which we proposed the name of 'Paracircoviridae' in our previous report.

Amino Acid Sequence↗
PubMed2000

Identification of a single nucleotide polymorphism in the MxA gene promoter (G/T at nt -88) correlated with the response of hepatitis C patients to interferon.

The interferon (IFN)-inducible MxA protein is known to play an important role in the host defense against certain viruses. We aimed to see if any genetic polymorphism in the promoter region of the MxA gene is associated with the IFN responsiveness of hepatitis C virus (HCV)-infected patients. Initially we sequenced the promoter region of the MxA gene in 12 subjects and found a polymorphic site. We then constructed a specific PCR-RFLP system for this site and subjected 63 samples from chronic hepatitis C patients who were nonresponders (NR) to IFN therapy to it, 52 with sustained response (SR), and 42 healthy controls. Subjects were all Japanese, and unrelated. A single nucleotide polymorphism (SNP) was identified in the MxA promoter region: G/T alleles at nt position -88. Interestingly, this SNP was involved in a genetic element highly homologous to the IFN-stimulated response element consensus sequence, and the G-to-T change there makes this homology a little greater. The rate of G.G homozygosity was 31% in the SR patients, significantly lower than in the NR patients (62%, p = 0.0009), while that of healthy controls was between the two groups (48%). Differences in HCV genotypes did not influence this result. Based on these findings, we propose that the SNP of the MxA promoter at nt -88 identified in this study affects the expression of MxA protein, and may thus be associated with the response of HCV patients to IFN.

Antiviral Agents↗
PubMed1999

Induction of apoptosis of monocyte-macrophage lineage cells by 5-S-GAD.

We found that 5-S-GAD, an insect-derived antibacterial peptide, inhibited murine osteoclast formation in vitro. We examined the specific time point of the inhibitory action of 5-S-GAD on osteoclast formation and found that it mainly suppressed differentiation of osteoclasts in the middle of the culture period. Using HL60 cells that are able to differentiate into multinucleated macrophage-like cells, we found that 5-S-GAD induced apoptosis of HL60 cells by producing H(2)O(2). Thus, the inhibition of osteoclast formation by 5-S-GAD could be, in part, due to apoptosis of the cells of an osteoclast lineage.

Acid Phosphatase↗
PubMed1999

New p73 variants with altered C-terminal structures have varied transcriptional activities.

p73 has been identified as a protein which shares significant homology with the tumor suppressor p53. We found two new types of splicing variant mRNAs for p73 expressed in MCF-7 cells which we named p73gamma and epsilon. Sequence analysis revealed that these mRNAs encode variant p73 proteins bearing distinct carboxy-terminal structures, which are also different from the previously reported variants p73alpha and beta. The mRNAs encoding p73gamma and epsilon as well as alpha and beta were confirmed to be expressed in normal human tissues in varied patterns. All of these splicing variants activated promoter with the p53-binding consensus sequence, but to different degrees. Furthermore, suppressive effects of p73alpha, gamma and epsilon, but not beta, on endogenous p53 activity were observed when transiently expressed in HepG2 and MCF-7 cells. These results suggested that the carboxy-terminal regions of p73 which were altered by alternative splicing affect these transactivation abilities and modulate the functions of p73 molecules.

Alternative Splicing↗
PubMed1999

Caspase-mediated cleavage of eukaryotic translation initiation factor subunit 2alpha.

Eukaryotic translation initiation factor 2alpha (eIF-2alpha), a target molecule of the interferon-inducible double-stranded-RNA-dependent protein kinase (PKR), was cleaved in apoptotic Saos-2 cells on treatment with poly(I).poly(C) or tumour necrosis factor alpha. This cleavage occurred with a time course similar to that of poly(ADP-ribose) polymerase, a well-known caspase substrate. In addition, eIF-2alpha was cleaved by recombinant active caspase-3 in vitro. By site-directed mutagenesis, the cleavage site was mapped to an Ala-Glu-Val-Asp(300) downward arrowGly(301) sequence located in the C-terminal portion of eIF-2alpha. PKR phosphorylates eIF-2alpha on Ser(51), resulting in the suppression of protein synthesis. PKR-mediated translational suppression was repressed when the C-terminally cleaved product of eIF-2alpha was overexpressed in Saos-2 cells, even though PKR can phosphorylate this cleaved product. These results suggest that caspase-3 or related protease(s) can modulate the efficiency of protein synthesis by cleaving the alpha subunit of eIF-2, a key component in the initiation of translation.

Apoptosis↗
PubMed1999

Complete circular DNA genome of a TT virus variant (isolate name SANBAN) and 44 partial ORF2 sequences implicating a great degree of diversity beyond genotypes.

Information on the entire genome of TT virus (TTV) has been scarce. The circular ssDNA genome of a variant (isolate name SANBAN) that we sequenced was only 56.7% homologous to the prototype isolate (TA278), with even lower homology at the amino acid level: 34.2% for ORF1 and 39.7% for ORF2. Regarding the ORF1, SANBAN was only very distantly related to the six major TTV genotypes reported to date. In partial ORF2 sequences determined on 44 isolates taken together, TTV has a broad range of genetic diversity and the SANBAN isolate may represent a new TTV-like viral species or genus and not merely a genotype of TTV.

Amino Acid Sequence↗
PubMed1999

Hepatitis C virus core protein regulates cell growth and signal transduction pathway transmitting growth stimuli.

To investigate the transforming potential of hepatitis C virus (HCV), HCV core protein was produced in BALB/3T3 A31-I-1 cells. The cells expressing HCV core gene cooperatively with the v-H-ras gene showed loss of contact inhibition, morphological alterations, and anchorage-independent and serum-independent growth. The cells producing HCV core protein showed enhanced growth against stimulus of growth factor. In addition, antisense oligodeoxynucleotides against mRNA encoding HCV core protein suppressed the growth of HCV core-producing cells. Furthermore, HCV core protein activated mitogen-activated protein kinase and serum response element, which respond to growth stimuli. From these results, we concluded that HCV core protein is involved in the acquisition of cell growth advantage.

3T3 Cells↗
PubMed1999

Phosphorylation of nonstructural 5A protein of hepatitis C virus: HCV group-specific hyperphosphorylation.

We previously showed that two proteins with molecular weights of 56 and 58 kDa are produced from nonstructural protein 5A (NS5A) derived from hepatitis C virus (HCV)-1b genotype. The 56-kDa protein is phosphorylated at serine residues in NS5A, including those located in the C-terminal region of NS5A, while the 58-kDa protein, the hyperphosphorylated form of the 56-kDa protein, is phosphorylated at serine residues in the central region. This hyperphosphorylation is dependent on the presence of HCV NS4A protein. To clarify whether NS4A-dependent phosphorylation also occurs in other HCV genotypes, phosphorylation of NS5A was analyzed by two-dimensional gel electrophoresis. Here, we report that NS5A from the HCV-2a genotype was phosphorylated. However, hyperphosphorylation of NS5A occurs in the HCV-1b genotype but not in the -2a genotype. This result suggests that modification of NS5A phosphorylation reflects the virological features of HCV and that there are physiological differences in the roles of differently phosphorylated NS5A between HCV genotypes.

Alkaline Phosphatase↗
PubMed1999

Genotypes of TT virus (TTV) compared between liver disease patients and healthy individuals using a new PCR system capable of differentiating 1a and 1b types from others*.

TT virus (TTV) lacks obvious pathogenicity; almost all of the infected hosts are symptom-free. A possibility remains, however, that certain strains can cause liver disease while most others are non-pathogenic. Genotypes 1 a and 1 b have been proposed to contain such pathogenic strains. To test this possibility, we constructed a PCR system capable of detecting TTV of the 1 a and 1 b genotypes differentially from the other genotypes, and compared the frequencies of these genotypes between patients with liver disease of unknown etiology (n=42) and healthy individuals (n=50). The assay comprised 3 steps: i) PCR to amplify a 3.2-kb fragment using universal primers; ii) 2nd-round PCR, starting from the 3.2-kb amplicon, for a approximately 280-nt fragment by use of genotype 1-specific primers; and iii) digestion of the approximately 280-nt amplicon with MboI and BanI to discriminate between 1 a and 1 b. Eventually, 40 (95%) of the patients and 47 (94%) of the controls were positive for the 3.2-kb amplicon, and the 1 a, 1 b, 1 a+1 b, and non-1 genotypes of TTV were found in 2 (5%) vs 4 (9 percent), 5 (13%) vs 4 (9%), 1 (3%) vs 1 (2%) and 32 (80%) vs 38 (81%) of the 40 patients and 47 controls, respectively: the distribution was almost identical between the two groups. The hypothesis that the genotype 1 of TTV may be more closely associated with liver disease than other genotypes was not supported by this study.

Base Sequence↗
PubMed1999

Replication of GB virus C (hepatitis G virus) in interferon-resistant Daudi cells.

We previously reported that Daudi cells, a Burkitt's lymphoma cell line, were capable of supporting productive infection of hepatitis C virus (HCV). During continual cultivation after HCV infection, the culture became resistant to interferons (IFNs). This resistant cell line, coded as H-903, was used as host cells for replication of GB virus C (GBV-C), also known as hepatitis G virus. GBV-C RNA was detected in the culture by reverse transcription-PCR for more than 130 days after inoculation, while it was detected for 44 days but not later in the parental IFN-sensitive Daudi cells. Productive infection of GBV-C in the H-903 system was confirmed by serially inoculating supernatants from infected cultures into uninfected cells. The viral E2 antigen was detected by immunofluorescence in the cells inoculated with the fifth passage of GBV-C. The presumed capsid-coding region of the viral genome in the inoculum, in the serially passaged virus, or in the virus produced by a long-term culture was only 16 amino acids long, suggesting that the GBV-C with a short core sequence was replication competent.

Amino Acid Sequence↗
PubMed1999

Hepatitis C virus core protein inhibits Fas- and tumor necrosis factor alpha-mediated apoptosis via NF-kappaB activation.

The effects of hepatitis C virus (HCV) proteins on anti-Fas (CD95/APO-1) antibody- and tumor necrosis factor alpha (TNF-alpha)-mediated apoptosis in different human cell lines were investigated by magnetic concentration of cells which transiently produced the exogenous protein. HepG2 cells, which produced whole HCV proteins, became resistant to anti-Fas-induced apoptotic cell death. Furthermore, the core protein among HCV proteins had a key role in protecting the various cells from apoptosis mediated by not only anti-Fas but also TNF-alpha. We also found that the core functioned in the activation of nuclear factor kappaB (NF-kappaB) in all cells examined. Deletion analysis of the core revealed that the region required for NF-kappaB activation was closely correlated with that for its antiapoptotic function. In addition, we revealed in some cases that the antiapoptotic effect of the core was restrained by coproduction of the inhibitor of NF-kappaB, IkappaB-alpha protein. These results demonstrated that the core inhibits Fas- and TNF-alpha-mediated apoptotic cell death via a mechanism dependent on the activation of NF-kappaB in particular cell lines.

Apoptosis↗
PubMed1999

Different inhibitory effects of 5-S-glutathionyl-beta-alanyl-L-dopa (5-S-GA-L-D) analogues on autophosphorylation and substrate phosphorylation of Src protein tyrosine kinase.

Starting with 5-S-glutathionyl-beta-alanyl-L-dopa (1) and 5-S-glutathionyl-beta-alanyl-dopamine (2), a series of analogues with truncated glutathionyl and beta-alanyl-dopa moieties were synthesized, and their inhibitory effects on autophosphorylation and substrate phosphorylation reaction by c-Src and by epidermal growth factor receptor (EGFR) were evaluated. When the glutamyl residue was removed, the inhibitory effects on v-Src autophosphorylation decreased about 4- to 5-fold, and concomitant removal of the glutamyl and beta-alanyl residues resulted in a 40- to 60-fold decrease in the inhibition of v-Src autophosphorylation. On the other hand, these modifications had little effect on the inhibitory activity of substrate (Raytide) phosphorylation by c-Src. Interestingly, 5-S-cysteinyl dopamine inhibited the Src substrate phosphorylation reaction with comparable potency to that of genistein. Nonpeptide lipophilic derivatives had a similar inhibition on v-Src autophosphorylation but decreased inhibitory effects on substrate phosphorylation when compared to the lead compounds. Most compounds showed little effect on substrate phosphorylation by EGFR.

Dopamine↗
PubMed1998

Hepatitis C virus infection and mutations of mannose-binding lectin gene MBL.

We assessed the genetic polymorphism of mannose-binding lectin (MBL) in 93 patients with chronic hepatitis C (45 responders and 48 nonresponders to interferon) and 218 healthy controls. Mutant allele was identified only at codon 54 (Gly-->Asp), leading to three genotypes (54 m/m, 54 W/m, and 54 W/W). Frequency of 54 m/m was significantly lower in interferon-responders (2.2%), compared to those in nonresponders (14.6%) and controls (10.6%): p < 0.05. Our results suggest that homozygous carriage of the variant allele of codon 54 of MBL may predict poor response to interferon in chronic hepatitis C patients.

Adult↗
PubMed1998

Association of mannose-binding lectin gene haplotype LXPA and LYPB with interferon-resistant hepatitis C virus infection in Japanese patients.

BACKGROUND/AIMS: Mannose-binding lectin, a key factor of the innate immune system, has genetic polymorphism, and individuals who carry certain genotypes of mannose-binding lectin are known to be more prone to severe or prolonged infectious diseases. We aimed to find any relevance of mannose-binding lectin polymorphism to hepatitis C virus infection. METHODS: We determined the mannose-binding lectin genotypes by sequence specific priming-polymerase chain reaction in 159 hepatitis C virus-infected chronic hepatitis patients and 218 healthy controls in Japan by looking at 4 polymorphic loci: 2 (H/L and X/Y) within the promoter region and 2 (P/Q and A/B) within exon-1 of the mannose-binding lectin gene. RESULTS: A group of mannose-binding lectin genotypes designated "XB-type" (containing LXPA or LYPB haplotype at least heterozygously) was less frequently found in interferon-responsive patients (38.5%) than in interferon-resistant patients (60.7%, p=0.008) and controls (57.3%, p=0.014). Individuals with the "XB-type" had lower serum concentrations of mannose-binding lectin, compared to those with "YA-type", which is defined by homozygous carriage of both Y and A alleles: 0.63+/-0.61 vs 2.06+/-1.17 mg/l, p<0.001. CONCLUSIONS: Our results suggest that the mannose-binding lectin-related innate immune system plays an important role in elimination of hepatitis C virus during interferon therapy. Determining mannose-binding lectin genotypes may help in selecting the hepatitis C virus-infected patients to be treated with interferon.

Antiviral Agents↗