Ferrer N, Azorín F, Villasante A, Gutiérrez C, Abad J P
Department de Biologia Molecular i Cellular, Centre d'Investigació i Desenvolupament-CSIC, Barcelona, Spain.
J Mol Biol. 1995 Jan 6;245(1):8-21. doi: 10.1016/s0022-2836(95)80034-4.
The evolutionarily conserved centromeric dodeca-satellite DNA has an asymmetric distribution of guanine and cytosine residues resulting in one strand being relatively G-rich. This dodeca-satellite G-strand contains a GGGA-tract that is similar to the homopurine tracts found in most telomeric DNA sequences. Here, we show that the dodeca-satellite G-strand forms intramolecular hairpin structures that are stabilized by the formation of non-Watson-Crick G.A pairs as well as regular Watson-Crick G.C pairs. Special stacking interactions are also likely to contribute significantly to the stability of this structure. This hairpin conformation melts at relatively high temperature, around 75 degrees C, and is detected under many different ionic and pH conditions. As judged by electron microscopy visualization, these structures can be formed in a B-DNA environment. Under the same experimental conditions, neither the C-strand nor the double-stranded dodeca-satellite DNA were found to form any unusual DNA structure. A protein activity has been detected that preferentially binds to the single-stranded dodeca-satellite C-strand. The biological relevance of these results is discussed in view of the similarities to telomeric DNA.
进化上保守的着丝粒十二聚体卫星DNA鸟嘌呤和胞嘧啶残基分布不对称，导致一条链相对富含鸟嘌呤。这种十二聚体卫星G链包含一个GGGA序列，类似于大多数端粒DNA序列中发现的同型嘌呤序列。在这里，我们表明十二聚体卫星G链形成分子内发夹结构，该结构通过形成非沃森-克里克G·A碱基对以及常规的沃森-克里克G·C碱基对而得以稳定。特殊的堆积相互作用也可能对该结构的稳定性有显著贡献。这种发夹构象在相对较高的温度（约75摄氏度）下解链，并且在许多不同的离子和pH条件下都能检测到。通过电子显微镜观察判断，这些结构可以在B-DNA环境中形成。在相同的实验条件下，未发现C链或双链十二聚体卫星DNA形成任何异常的DNA结构。已检测到一种优先结合单链十二聚体卫星C链的蛋白质活性。鉴于与端粒DNA的相似性，对这些结果的生物学相关性进行了讨论。
