Vorlicková M, Kejnovská I, Kovanda J, Kypr J
Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, CZ-612 65 Brno, Czech Republic.
Nucleic Acids Res. 1998 Mar 15;26(6):1509-14. doi: 10.1093/nar/26.6.1509.
CD spectroscopy and PAGE were used to cooperatively analyze melting conformers of DNA strands containing GA and TA dinucleotide repeats. The 20mer (GA)10 formed a homoduplex in neutral solutions containing physiological concentrations of salts and this homoduplex was not destabilized even in the terminal (GA)3 hexamers of (GA)3(TA)4(GA)3, although the central (TA)4 portion of this oligonucleotide preserved the conformation adopted by (TA)10. This observation demonstrates that homoduplexes of alternating GA and TA sequences can co-exist in a single DNA molecule. Another 20mer, (GATA)5, adopted as a whole either the AT duplex, like (TA)10, or the GA duplex, like (GA)10, and switched between them reversibly. The concentration of salt controlled the conformational switching. Hence, guanine and thymine share significant properties regarding complementarity to adenine, while the TA and GA sequences can stack in at least two mutually compatible ways within the DNA duplexes analyzed here. These properties extend our knowledge of non-canonical structures of DNA.
圆二色光谱法（CD光谱法）和聚丙烯酰胺凝胶电泳（PAGE）被用于协同分析含有GA和TA二核苷酸重复序列的DNA链的解链构象。20聚体（GA）10在含有生理浓度盐的中性溶液中形成同源双链体，即使在（GA）3（TA）4（GA）3的末端（GA）3六聚体中，这种同源双链体也不会解链，尽管该寡核苷酸的中央（TA）4部分保留了（TA）10所采用的构象。这一观察结果表明，交替的GA和TA序列的同源双链体可以在单个DNA分子中共存。另一个20聚体（GATA）5整体上要么采用像（TA）10那样的AT双链体，要么采用像（GA）10那样的GA双链体，并在它们之间可逆地切换。盐的浓度控制着构象转换。因此，鸟嘌呤和胸腺嘧啶在与腺嘌呤互补方面具有显著特性，而在此处分析的DNA双链体中TA和GA序列可以以至少两种相互兼容的方式堆积。这些特性扩展了我们对DNA非经典结构的认识。
