Biomedical subjects

Hidehiro Takahashi

Publications and source records attributed to Hidehiro Takahashi.

23 records · Page 2Linked to original sources

PubMed2002

Binding and dissociation of human topoisomerase I with hairpin-loop RNAs: implications for the regulation of HIV-1 replication.

Cellular topoisomerase I has been reported to be present in retroviral particles and to enhance viral cDNA synthesis; however, the mechanisms involved remain unknown. In the present study, it has been demonstrated that human topoisomerase I combines with a stem-loop RNA and that the bound topoisomerase I can be dissociated from RNA substrates in the presence of ATP. In addition, in vitro cleaved synthetic RNA bound by topoisomerase I is subsequently relegated when the topoisomerase I is dissociated by ATP. A mechanism is proposed in which human topoisomerase I is carried into virions and regulates the repair of genomic RNA by its ligation activity.

Adenosine Triphosphate↗

PubMed2002

Topoisomerase I and ATP activate cDNA synthesis of human immunodeficiency virus type 1.

Replication of human immunodeficiency virus type 1 (HIV-1) is regulated at reverse transcription. Cellular topoisomerase I has been reported to be carried into HIV-1 virions and enhance cDNA synthesis in vitro, suggesting that topoisomerase I expressed in virus producer cells regulates reverse transcription. Here, by employing both indicator cell assay and endogenous reverse transcription (ERT) assay, we show that topoisomerase I and adenosine triphosphate (ATP) enhanced cDNA synthesis of HIV-1. In addition, topoisomerase I mutants, R488A and K532A, lacking enzymatic activity, attenuated the efficiency of cDNA synthesis and resulted in inhibition of the infectivity of HIV-1, suggesting that the activity of topoisomerase I lacking in these mutants is indispensable for the cDNA synthesis in the HIV-1 replication process. Furthermore, ATP could dissociate topoisomerase I from the topoisomerase I-RNA complex and enhance cDNA synthesis in vitro. These findings suggest that cellular topoisomerase I and ATP play a pivotal role in the synthesis of cDNA of HIV-1.

Adenosine Diphosphate↗

PubMed2002

Expression of JC virus agnoprotein in progressive multifocal leukoencephalopathy brain.

To examine the function of JC virus (JCV) agnoprotein, we examined the brains of cases of progressive multifocal leukoencephalopathy (PML), which is caused by JCV infection, using a newly generated antibody. The antibody reacted with 8 kDa protein specific for JCV agnoprotein by Western blotting. In vitro analyses showed that JCV capsid protein VP1 and large T antigen (T-Ag) were localized in the nuclei, but that agnoprotein was mainly detected in the cytoplasm of JCV-infected cells with an occasional nuclear staining. In the PML brain, an immunoreactive signal for agnoprotein was distributed in the perinuclear areas and cytoplasmic processes with occasional punctate staining in demyelinating lesions as well as adjacent myelinated areas. Agnoprotein presented mostly in the infected oligodendrocytes and partly in the astrocytes. Using double immunostaining, agnoprotein was seen to be expressed in the cytoplasmic processes of the cells, the nuclei of which were labeled with VP1 and T-Ag, where virus particles existed. Thus, JCV agnoprotein was mostly expressed in the infected oligodendrocytes and mainly localized in the cytoplasmic processes apart from virus particles in the demyelinated lesions.

Adult↗

PubMed2002

Reconstitution of cleavage of human immunodeficiency virus type-1 (HIV-1) RNAs.

A human immunodeficiency virus type 1 (HIV-1) particle contains approximately 1200 molecules of gag proteins and two copies of a 9.2-kb genomic RNA which has been reported to be dimerized and rapidly cleaved and to form a complex with a nucleocapsid protein, p7 (NCp7), during viral budding. These suggest that the cleavage can be reconstituted with gag proteins in vitro. Here we show that the p15(gag) coding region of viral RNA is fragmented in viral particles and that in vitro-synthesized RNA transcripts of HIV-1 undergo cleavage which is activated by NCp7 and other factors. Single-stranded oligoribonucleotides were cleaved between C and A or U and A, leaving 2',3'-cyclic phosphate and 5'-hydroxyl termini. These findings might explain the rapid degradation of genomic RNAs in HIV-1 particles.

Base Sequence↗

PubMed2002

Persistent infection of influenza virus in irradiated mice and its prevention by intranasal vaccination.

Effects of intranasal administration of influenza vaccine on persistent viral infection in gamma-ray irradiated mice were examined. BALB/c mice were exposed to a sub-lethal dose of gamma-ray (7Gy) and infected intranasally with non-lethal A/PR/8/34 (PR8, H1N1) viruses. The mice irradiated on days 0 or +2 of infection showed a significant weight loss with a slight decrease in survival rate 3 weeks after infection. These mice kept infective viruses in the nasal and/or lung sites even 3 weeks after infection (persistent viral infection) without IgA or IgG antibodies (Abs), although non-irradiated infected mice cleared the virus completely within 2 weeks. On the other hand, the pretreatment with the nasal adjuvant-combined vaccine (3 days before irradiation) prevented the persistent viral infection with the Abs. These results demonstrate that the exacerbation of influenza is induced by the irradiation during early days of infection (0-2 days) and that the exacerbation is prevented by the intranasal vaccination at least 3 days before irradiation.

Administration, Intranasal↗