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Structural morphorism of DNA triplexes and triplet repeat sequences

DNA 三链体和三联体重复序列的结构形态

基本信息

批准号：
10672028
负责人：
SHINDO Heisaburo
金额：
$ 2.05万
依托单位：
Tokyo University of Pharmacy and Life Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

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.

分子间DNA三联体的形成及化学修饰的影响：pH值、温度、序列错配、化学修饰等因素都是导致DNA三联体形成的原因。利用等温量热仪和表面等离子体共振法获得了该化合物的热力学和动力学参数，并对所得参数进行了分析，评价了第三链嘧啶的化学修饰效果。含有dU、RNA和2′- o -甲基的核苷酸的焓变化相似。相比之下，与其他碱基或糖段进行化学修饰的核苷酸相比，由硫代磷取代的磷酸主链在缔合常数方面具有一个数量级的显著不稳定性。结果表明，磷酸主链是控制DNA三联体稳定性最敏感的片段。特定DNA序列对染色质结构的影响：许多特定序列通常导致DNA的高阶结构的形成，即所谓的非b DNA。这种特殊的序列经常在真核细胞中发现，但其生物学作用尚不清楚。我们构建了一个检测系统来检测DNA序列对酵母细胞核小体组织的影响，并证明了长束的聚dA和Z-DNA形成序列完全排除在定位的核小体之外，而三联体形成序列不会破坏染色质组织，但会破坏染色质组织的稳定性。利用这种迷你染色体分析系统，我们研究了三重重复序列（CTG）n和（CGC）n的影响，结果表明前者不影响核小体的结构，而后者破坏核小体的定位。