| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1999: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1998: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
Formation of intermolecular DNA triplexes and the effects of chemical modifications : There are many causes such as pH, temperature, mismatched sequences, chemical modifications and so on. We obtained thermodynamic and kinetic parameters by an isothermal calorimeter and surface plasmon resonance method, and analyzed obtained parameters to evaluate the effects of chemical modifications of the third pyrimidine strands. Entalpy changes are similar among nucleotides with dU, RNA and 2'-O-methyl. By contrast, phosphate backbone substituted by phosphorothioate was dramatically unstable by an order of the magnitude in terms of association constant, compared with other nucleotides with chemically modified bases or sugar moiety. This result shows that backbone phosphate is most sensitive moiety to control the stability of DNA triplexes.
Effects of specific DNA sequences on chromatin structures : Many specific sequences often result in the formation of higher order structures of DNA, so-called non-B DNA. Such specific sequences are frequently found in eucaryotic cells, but their biological roles are not known. We have constructed an assay system to examine effects of DNA sequences on nucleosome organization in yeast cells and demonstrated that long tract of poly dA and Z-DNA forming sequence are completely excluded from a positioned nucleosome, whereas triplex forming sequences do not disrupt but destabilizes chromatin organization. Using this mini chromosome assay system we investigated effects of triplet repeat sequences such as (CTG)n and (CGC)n, showing that the former does not affect the nucleosome structure but the latter disrupts nucleosome positioning.
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