Ortiz-Lombardía M, Cortés A, Huertas D, Eritja R, Azorín F
Department de Biologia Molecular i Cel.lular, Centre d'Investigació i Desenvolupament-CSIC, Jordi Girona Salgado 18-26, Barcelona, 08034, Spain.
J Mol Biol. 1998 Apr 10;277(4):757-62. doi: 10.1006/jmbi.1998.1646.
The centromeric dodeca-satellite of Drosophila forms unusual DNA structures in which its purine-rich strand (GTACGGGACCGA)n folds into very stable intramolecular hairpins. These intramolecular hairpins contain groups of tandem 5'-GA:GA-3' mismatches that, as judged by gel electrophoresis analysis and UV-melting studies, have a determinant contribution to their stability. Duplexes of the dodeca-satellite purine-rich strand, carrying tandem 5'-GA:GA-3' mismatches, are as stable as equivalent fully Watson-Crick duplexes containing tandem 5'-TA:TA-3' Watson-Crick pairs in place of the non-Watson-Crick G.A pairs. On the other hand, duplexes carrying any of the other three possible tandem combinations of purine.purine mismatches, including G.A pairs on the opposite orientation 5'-AG:AG-3', are very unstable. The high stability of the dodeca-satellite hairplus suggests that the tandem G.A pairs are on the sheared configuration although they are found within the less favourable 5'-G-(G-A)-C-3' sequence context. Other centromeres DNA sequences, including the AAGAG satellite of Drosophila and the mammalian CENP-B box sequence, have the potential of forming intramolecular hairpins stabilised by similar purine.purine interactions.
果蝇的着丝粒十二聚体卫星形成异常的DNA结构，其中其富含嘌呤的链（GTACGGGACCGA）n折叠成非常稳定的分子内发夹。这些分子内发夹包含串联的5'-GA:GA-3'错配基团，通过凝胶电泳分析和紫外熔解研究判断，这些错配基团对其稳定性有决定性贡献。携带串联5'-GA:GA-3'错配的十二聚体卫星富含嘌呤链的双链体，与含有串联5'-TA:TA-3'沃森-克里克配对以取代非沃森-克里克G.A配对的等效完全沃森-克里克双链体一样稳定。另一方面，携带嘌呤-嘌呤错配的其他三种可能串联组合中的任何一种的双链体，包括相反方向5'-AG:AG-3'上的G.A配对，都非常不稳定。十二聚体卫星发夹的高稳定性表明，串联的G.A配对处于剪切构型，尽管它们存在于不太有利的5'-G-(G-A)-C-3'序列环境中。其他着丝粒DNA序列，包括果蝇的AAGAG卫星和哺乳动物的CENP-B框序列，具有形成由类似嘌呤-嘌呤相互作用稳定的分子内发夹的潜力。
