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Kanta Tsumoto

Publications and source records attributed to Kanta Tsumoto.

6 recordsLinked to original sources
PubMed2005

Enhancement and inhibition of DNA transcriptional activity by spermine: a marked difference between linear and circular templates.

We compared the transcriptional activities of the circular and linear forms of short (4kbp) and giant (106kbp) DNA molecules in the presence of a polyamine, spermine (4+). With an increase in the spermine concentration, transcriptional activity was enhanced, followed by an inhibitory effect, and complete inhibition was observed in the sole case of long, linear templates. A difference between the transcriptional properties of circular and linear conformations is found for giant DNA molecules. These results are discussed in relation to DNA conformational transitions.

DNA↗
PubMed2003

Gene expression within cell-sized lipid vesicles.

Functional protein synthesis was observed in cell-sized lipid vesicles following encapsulation of a gene-expression system. Expression of rsGFP (red-shifted green fluorescent protein) within individual vesicles was observed by fluorescence microscopy. Interestingly, at the early stage of the reaction, the expression efficiency inside the vesicle was remarkably higher than that in the solution outside. The synthesized rsGFP in individual vesicles is safe from attack by proteinase K added to the external aqueous solution. Studies on cell-sized vesicles expressing protein should contribute to a fundamental understanding of certain aspects of living systems and will be useful for practical applications, such as the construction of microreactors.

Endopeptidase K↗
PubMed2003

Giant DNA molecules exhibit on/off switching of transcriptional activity through conformational transition.

We found that the transcriptional activity of large DNAs (40 kbp) can be completely inhibited by adding condensing agents, spermine and poly(ethylene glycol), whereas under the same conditions short fragments (140 bp) still show active transcription. Fluorescence microscopic observations of large DNAs revealed clear correlation between the higher-order structure of templates and their transcriptional activity. The steep decrease in transcriptional activity leading to complete inhibition, or on/off switching, is interpreted in terms of conformational transition of the ensemble of DNA molecules.

DNA↗
PubMed2002

Folding transition of large DNA completely inhibits the action of a restriction endonuclease as revealed by single-chain observation.

The biochemical characteristics of lambda DNA chains in folded/unfolded states upon cleavage by the restriction enzyme ApaLI were investigated in the presence of spermine. These characteristics of DNA chains depending on their higher-order structure were studied at the single-molecule level using fluorescence microscopy. With a low concentration of spermine, lambda DNA takes a random coiled conformation and allows digestion by the enzyme, while under a high concentration of spermine, lambda DNA takes a compact folded structure and inhibits such attack. Together with comparative experiments on short oligomeric DNA, our results suggest that the transition in the higher-order structure causes on/off-type switching of sensitivity to the enzyme.

Base Sequence↗
PubMedDate not supplied

NTP concentration switches transcriptional activity by changing the large-scale structure of DNA.

It is becoming clearer that genetic activity is closely associated with the intracellular energy state. However, the mechanisms of this association are still unclear. In this study, we focused on large-scale changes in the structure of DNA to examine the effect of the NTP concentration on the transcription reaction with T7 RNA polymerase and compared the results with long duplex DNA to those with a short persistent-length(1) fragment. The transcriptional activity dramatically changed only for long duplex DNA within a narrow range of NTP concentrations associated with changes in the large-scale structure of DNA. This result suggests that the energy state may play an essential role in regulating ON/OFF switching on transcriptional activity.

Bacteriophages↗