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21.
In the developing anther, archesporial cells that proliferateby mitotic division are converted into meiotic cells duringthe premeiotic interphase. Experiments with explanted microsporocytesof Lilium and Trillium were made to obtain evidence for theconversion of mitotic to meiotic cells during the premeioticperiod. Explanted premeiotic cells were cultured through thedivision cycle at relatively high division frequencies and showeda variety of division types with respect to chromosomal events.The type of division depended on the premeiotic stage at whichthe cells were explanted. Cells in the G1, S and early G2 phasesunderwent mitotic division and formed a diad or binucleate monad.Cells explanted at the late G2 phase were cultured throughoutthe normal meiotic cycle, which resulted in typical tetrad configuration. In microsporocytes explanted during the main part of the G2interval, centromere behavior was meiotic, but chromosome pairingand chiasma formation were disturbed. Thus, she G2 intervalwas shown to be critical for the commitment of mitotic cellsto meiotic division. Detailed analysis showed that the intracellularchanges that commit the cells to meiosis begin shortly aftercompletion of premeiotic DNA synthesis and that these changesare progressive and cumulative. (Received February 2, 1982; Accepted May 24, 1982) 相似文献
22.
Souichi Nukuzuma Masanori Kameoka Shigeki Sugiura Kazuo Nakamichi Chiyoko Nukuzuma Isao Miyoshi Tsutomu Takegami 《Microbiology and immunology》2009,53(11):621-628
Pathogenic JCV with rearranged regulatory regions (PML-type) causes PML, a demyelinating disease, in the brains of immunocompromised patients. On the other hand, archetype JCV persistently infecting the kidney is thought to be converted to PML-type virus during JCV replication in the infected host under immunosuppressed conditions. In addition, Tat protein, encoded by HIV-1, markedly enhances the expression of a reporter gene under control of the JCV late promoter.
In order to examine the influence of Tat on JCV propagation, we used kidney-derived COS-7 cells, which only permit archetype JCV, and established COS-tat cells, which express HIV-1 Tat stably. We found that the extent of archetype JCV propagation in COS-tat cells is significantly greater than in COS-7 cells. On the other hand, COS-7 cells express SV40 T antigen, which is a strong stimulator of archetype JCV replication. The expression of SV40 T antigen was enhanced by HIV-1 Tat slightly according to real-time RT-PCR, this was not closely related to JCV replication in COS-tat cells. The efficiency of JCV propagation depended on the extent of expression of functional Tat. To our knowledge, this is the first report of increased production of archetype JCV in a culture system using cell lines stably expressing HIV-1 Tat. We propose here that COS-tat cells are a useful tool for studying the role of Tat in archetype JCV replication in the development of PML. 相似文献
In order to examine the influence of Tat on JCV propagation, we used kidney-derived COS-7 cells, which only permit archetype JCV, and established COS-tat cells, which express HIV-1 Tat stably. We found that the extent of archetype JCV propagation in COS-tat cells is significantly greater than in COS-7 cells. On the other hand, COS-7 cells express SV40 T antigen, which is a strong stimulator of archetype JCV replication. The expression of SV40 T antigen was enhanced by HIV-1 Tat slightly according to real-time RT-PCR, this was not closely related to JCV replication in COS-tat cells. The efficiency of JCV propagation depended on the extent of expression of functional Tat. To our knowledge, this is the first report of increased production of archetype JCV in a culture system using cell lines stably expressing HIV-1 Tat. We propose here that COS-tat cells are a useful tool for studying the role of Tat in archetype JCV replication in the development of PML. 相似文献
23.
Nagao A Zhao X Takegami T Nakagawa H Matsui S Matsunaga T Ishigaki Y 《Biochemical and biophysical research communications》2008,370(2):301-305
To improve the efficiency of stable knockdown with short hairpin RNA (shRNA), we inserted multiple shRNA expression sequences into a single plasmid vector. In this study, the DNA repair factor XPA was selected as a target gene since it is not essential for cell viability and it is easy to check the functional knockdown of this gene. The efficiency of knockdown was compared among single and triple expression vectors. The single shRNA-expressing vector caused limited knockdown of the target protein in stable transfectants, however, the multiple expression vectors apparently increased the frequency of knockdown transfectants. There were correlations between the knockdown level and marker expression in multiple-expressing transfectants, whereas poorer correlations were observed in single vector transfectants. Multiple-transfectants exhibited reduced efficiency of repair of UV-induced DNA damage and an increased sensitivity to ultraviolet light-irradiation. We propose that multiple shRNA expression vectors might be a useful strategy for establishing knockdown cells. 相似文献
24.
Hepatitis C virus (HCV) causes a persistent infection, chronic hepatitis, and leads to hepatocellular carcinoma. Nonstructural protein 3 (NS3) of HCV possesses protease, nucleoside triphosphatase, and helicase activities. Using the yeast two hybrid assay, we identified Sm-D1, a host protein that binds to NS3. Sm-D1 is a component of small nuclear ribonucleoprotein (snRNP) complexes which are associated with autoimmune disease. Sm-D1 has Gly-Arg (GR) repeats at the C terminus, which contains dimethylarginine modified by post-translational modification and may constitute an immunoreactive determinant. Deletion mutants revealed that the C-terminal region of Sm-D1 containing the GR repeats was the binding region for NS3, and the expression feature of Sm-D1 was affected by co-expression of NS3. Immunostaining assay demonstrated that NS3 was also present in the nucleus of cells overexpressing Sm-D1, although it was usually found in cytoplasm. The localization of NS3 could change following interaction with Sm-D1 and affect the function of Sm-D1. 相似文献
25.
Theiler's murine encephalomyelitis virus subgroup strain-specific infection in a murine macrophage-like cell line. 总被引:3,自引:3,他引:0
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We compared infection of a murine macrophage-like cell line, J774-1, with two Theiler's murine encephalomyelitis virus subgroup strains. The GDVII strain, which is highly virulent and produces acute polioencephalomyelitis in mice, did not actively replicate in J774-1 cells, although there was a significant inhibition in cellular protein synthesis. In contrast, the DA strain, which is less virulent and causes demyelination with a persistent virus infection, productively infected J774-1 cells; however, there was less virus produced than in BHK-21 cells, and there was little if any cellular protein shutoff. These in vitro data may provide some explanation for the biological activities that are observed between both subgroup strains. 相似文献
26.
Clinical evidence suggests that hepatitis C virus (HCV) is etiologically involved in hepatic cancer and liver cirrhosis. To investigate whether the HCV nonstructural protein NS3 has oncogenic activity, NIH 3T3 cells were transfected with an expression vector containing cDNA for the 5'- or 3'-half sequence of the HCV genome segment encoding NS3. Only cells transfected with the 5'-half cDNA rapidly proliferated, lost contact inhibition, grew anchorage independently in soft agar, and formed tumors in nude mice. PCR analysis confirmed the presence of the 5'-half DNA in the transfectants. These results suggest that the 5' region of the HCV genome segment encoding NS3 is involved in cell transformation. 相似文献
27.
Tsutom Takegami Kazuo Yoshida 《Biochemical and biophysical research communications》1975,67(2):782-789
Cytokinin binding protein from tobacco leaves was isolated and purified to a single protein by means of affinity chromatography on benzyladenine-linked Sepharose column combined with polyacrylamide gel electrophoresis. In vitro binding of this protein to [14C] benzyladenine was inhibited remarkably by cold benzyladenine and kinetin and slightly by adenine, but not adenosine. The molecular weight of the protein was determined to be about 4,000 daltons by gel filtration and SDS polyacrylamide gel electrophoresis. 相似文献
28.
Souichi Nukuzuma Chiyoko Nukuzuma Masanori Kameoka Shigeki Sugiura Kazuo Nakamichi Takafumi Tasaki Koushi Hidaka Tsutomu Takegami 《Microbiology and immunology》2018,62(8):524-530
29.
Dengue-1 (D1) Mochizuki strain was examined for its nucleotide and amino acid sequences of genomic RNA and the data obtained were compared with those of other selected virus strains reported previously. Genomic regions corresponding to C, preM and M proteins were the major subjects of study. Parts of E protein were additionally examined. Among the D1 viruses investigated, the Mochizuki virus which was isolated in 1943 in Japan was shown to be close to Philippine 836-1 strain isolated in 1984 and Nauru Island strain isolated in 1974 at the respective places, in contrast with Thai AHF 82-80 strain isolated in 1980 and Caribbean CV1636/77 strain isolated in 1977. At the same time, a difference was noted between the Mochizuki and Philippine/Nauru strains at the cleavage site of preM/M junction: Mochizuki possessed RRGKR/S sequence whereas the Philippine/Nauru had RRDKR/S. The glycosylation site in preM and hydrophobic regions at the carboxyl termini of M and E were well conserved. Significances of the data are discussed in connection with viral epidemiology and variation. 相似文献
30.
Miki T Takegami Y Okawa K Muraguchi T Noda M Takahashi C 《The Journal of biological chemistry》2007,282(16):12341-12352
The reversion-inducing cysteine-rich protein with Kazal motifs (RECK) is anchored to the cell surface via glycosylphosphatidylinositol. This molecule antagonizes the function of membrane type 1 matrix metalloproteinase (MT1-MMP) to promote proMMP-2 maturation. Here, we attempt to clarify the mechanism underlying RECK functions. First, we found that RECK forms a complex with MT1-MMP and inhibits its proteolytic activity. Notably, RECK increases the amount of MT1-MMP that associates with detergent-resistant membranes during sucrose gradient ultracentrifugation. Furthermore, perturbation of membrane cholesterol significantly affected the function of RECK in suppressing MT1-MMP function. These findings indicate that RECK possibly regulates MT1-MMP function by modulating its behavior on the cell surface as well as by enzymatic action; this prompted us to find another molecule whose behavior in detergent-resistant membranes is influenced by RECK. Subsequently, we found that RECK interacts with CD13/aminopeptidase N. Further, we found that RECK inhibits the proteolytic activity of CD13 in a cholesterol perturbation-sensitive manner. Finally, we examined whether RECK influences the behavior of MT1-MMP and CD13 during their internalization from the cell surface. In the absence of RECK, MT1-MMP and CD13 were internalized along with the markers of clathrin- or caveolae-dependent endocytosis. However, interestingly, in the presence of RECK these molecules were internalized preferentially with an endocytic marker that is neither clathrinnor caveolae-dependent, indicating that RECK modulates endocytic pathways of MT1-MMP and CD13. This modulation was correlated with the accelerated internalization and decay of MT1-MMP and CD13. This study unveils the novel function and target molecules of RECK. 相似文献