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221.
Tada S Kundu LR Enomoto T 《BioEssays : news and reviews in molecular, cellular and developmental biology》2008,30(3):208-211
Although initiation of DNA replication is considered to be highly coordinated through multiple protein-DNA and protein-protein interactions, it is poorly understood how particular locations within the eukaryotic chromosome are selected as origins of DNA replication. Here, we discuss recent reports that present structural information on the interaction characteristics of the archaeal orthologues of the eukaryotic origin recognition complex with their cognate binding sequences. Since the archaeal replication system is postulated as a simplified version of the one in eukaryotes, by analogy, these works provide insights into the functions of the eukaryotic initiator proteins. 相似文献
222.
Germline transformation of the silkworm Bombyx mori L. using a piggyBac transposon-derived vector 总被引:21,自引:0,他引:21
Tamura T Thibert C Royer C Kanda T Abraham E Kamba M Komoto N Thomas JL Mauchamp B Chavancy G Shirk P Fraser M Prudhomme JC Couble P Toshiki T Chantal T Corinne R Toshio K Eappen A Mari K Natuo K Jean-Luc T Bernard M Gérard C Paul S Malcolm F Jean-Claude P Pierre C 《Nature biotechnology》2000,18(1):81-84
We have developed a system for stable germline transformation in the silkworm Bombyx mori L. using piggyBac, a transposon discovered in the lepidopteran Trichoplusia ni. The transformation constructs consist of the piggyBac inverted terminal repeats flanking a fusion of the B. mori cytoplasmic actin gene BmA3 promoter and the green fluorescent protein (GFP). A nonautonomous helper plasmid encodes the piggyBac transposase. The reporter gene construct was coinjected into preblastoderm eggs of two strains of B. mori. Approximately 2% of the individuals in the G1 broods expressed GFP. DNA analyses of GFP-positive G1 silkworms revealed that multiple independent insertions occurred frequently. The transgene was stably transferred to the next generation through normal Mendelian inheritance. The presence of the inverted terminal repeats of piggyBac and the characteristic TTAA sequence at the borders of all the analyzed inserts confirmed that transformation resulted from precise transposition events. This efficient method of stable gene transfer in a lepidopteran insect opens the way for promising basic research and biotechnological applications. 相似文献
223.
Protective effect of cAMP on tumor promoter-mediated inhibition of cell-cell communication 总被引:3,自引:0,他引:3
The formation and maintenance of electrical cell coupling is inhibited by 100 ng/ml 12-O-tetradecanoylphorbol-13-acetate (TPA). This inhibition could be prevented by db-cAMP and aminophylline when added together with TPA, though they did not restore the cell coupling once it had already been blocked by TPA. It is suggested that db-cAMP affects the early membrane effects of TPA in FL cells. 相似文献
224.
Journal of Ethology - Agonistic encounters of juvenile male crickets were analyzed behaviourally. In a pairing between adult and juvenile male crickets, the juvenile crickets were usually beaten by... 相似文献
225.
226.
The relation between ESR-detectable Cu(II) and Cu,Zn-superoxide dismutase activity was examined. The Cu(II) spin numbers per one unit of SOD were 6.26 X 10(12) (+/- 0.51 X 10(12] spins in several preparations of recombinant human Cu,Zn-SOD, native placental, and erythrocyte SOD. Measurement could be performed over a wide range of pH (4.0-10.0), preferably at temperatures below -40 degrees C. The data obtained by this method correlated well to the results obtained by the method of Fridovich et al. using the xanthine-xanthine oxidase system (correlation coefficient 0.995). The specific activity of SOD was proportional to the Cu(II) content measured by ESR, but not to the total Cu content measured by atomic absorption. This indicates that it is important to measure the Cu(II) content for determining Cu,Zn-SOD activity. 相似文献
227.
DNA helicase and nucleoside-5'-triphosphatase activities of polyoma virus large tumor antigen 总被引:15,自引:0,他引:15
Polyoma virus large tumor antigen (PyV T antigen) has been purified to near homogeneity by immunoaffinity column chromatography. We have detected DNA helicase and ATPase (nucleoside-5'-triphosphatase) activities in the purified PyV T antigen fraction and characterized these activities. The ATPase activity was stimulated about 2-fold by poly(dT), which was the most effective stimulator among the synthetic polynucleotides tested. Natural nucleic acids, such as calf thymus native and heat-denatured DNA, and single-stranded circular fd DNA were also effective, but the degree of stimulation was less than 1.5-fold. The basal and poly(dT)-stimulated ATPase activities showed similar preference for nucleoside 5'-triphosphates, requirement for divalent cations, and pH optima. The preference for nucleoside 5'-triphosphates was ATP, dATP greater than CTP, UTP much greater than GTP. The only difference observed between the two activities was salt sensitivity. The basal ATPase activity was resistant to KC1 up to 300 mM. In contrast, poly-(dT)-stimulated activity was reduced to the level of basal activity at 300 mM KC1. DNA helicase activity required divalent cations and was dependent on hydrolysis of ATP. The activity showed similar preference for nucleoside 5'-triphosphates, requirement for divalent cations, and pH optimum as the two ATPase activities, and the salt sensitivity of DNA helicase activity was similar to that of poly(dT)-stimulated ATPase activity. The helicase activity was inhibited competitively by the addition of single-stranded or double-stranded DNA, and a relatively high inhibitory activity was observed with poly [d(A-T)]. The PyV T antigen helicase was found to migrate in the 3' to 5' direction along the DNA strand to which the protein bound. 相似文献
228.
Adsorption of Lithocholic Acid to Fusarium equiseti M41 as an Essential Process in Its Conversion to Ursodeoxycholic Acid
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Takuya Nihira Toshiki Nishino Masao Maehara Songsri Kulprecha Toshiomi Yoshida Hisaharu Taguchi 《Applied microbiology》1988,54(3):670-675
Fusarium equiseti M41 converts lithocholic acid to ursodeoxycholic acid. Adsorption of lithocholic acid particles to mycelia of F. equiseti M41 is essential in the conversion of lithocholic acid to ursodeoxycholic acid. Production of ursodeoxycholic acid was negligible when particles of lithocholic acid were absent. As the concentration of lithocholic acid particles increased, both the amount of mycelium-bound lithocholic acid and the production of ursodeoxycholic acid increased hyperbolically (K1/2 = 1.9 g/liter and Kmapparent = 1.9 g/liter. A fluorescent lithocholic acid derivative was used to confirm that insoluble particles of lithocholic acid attached to the surface of the mycelia. The hydrophobic nature of this binding was estimated from the close relationship observed between the hydrophobicity of bile acids and their binding capacity to the mycelia. By repeated washing with 30% dimethyl sulfoxide, two binding modes of lithocholic acid were distinguished, i.e., surface binding (59% of bound lithocholic acid) and tight binding (41% of bound lithocholic acid). From the amount of tightly bound lithocholic acid, the intracellular concentration of lithocholic acid was calculated to be 1,433-fold higher than its saturating concentration in the reaction mixture, thus promoting effective conversion to ursodeoxycholic acid in the mycelia. Several lines of evidence indicated that glycoproteins of the cell wall participated in the binding of lithocholic acid. 相似文献
229.
T. Motegi M. Ohuchi C. Ohtaki K. Fujiwara S. Enomoto T. Hasegawa K. Kishi H. Hayakawa 《Human genetics》1985,71(2):160-162
Summary A tiny interstitial delection of 7p was found in a 5-month-old boy with a craniosynostosis and many anomalies. His karyotype was 46,XY,del(7)(p15.3p21.3). Here we present not only further evidence of an association between craniosynostosis and 7p monosomy, but also deletion mapping to indicate that the critical segment for craniosynostosis lies in the mid-portion of 7p21, that is at 7p21.2 or the proximal part of 7p21.3. 相似文献
230.
Naoki Kinoshita Hiroshi Oguchi Toshiki Adachi Hiroki Shioura Hirohiko Kimura 《Reports of Practical Oncology and Radiotherapy》2018,23(3):199-206