Tandem 5'-GA:GA-3' mismatches account for the high stability of the fold-back structures formed by the centromeric Drosophila dodeca-satellite.
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.
Ortiz-Lombardía
M
M
Department de Biologia Molecular i Cel.lular, Centre d'Investigació i Desenvolupament-CSIC, Jordi Girona Salgado 18-26, Barcelona, 08034, Spain.
Cortés
A
A
Huertas
D
D
Eritja
R
R
Azorín
F
F
D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D002503:Centromere / Q000235:genetics; D004276:DNA, Satellite / Q000737:chemistry* / Q000235:genetics* / Q000528:radiation effects; D004330:Drosophila / Q000235:genetics*; D004355:Drug Stability; D009690:Nucleic Acid Conformation / Q000528:radiation effects; D009691:Nucleic Acid Denaturation / Q000528:radiation effects; D012091:Repetitive Sequences, Nucleic Acid; D014466:Ultraviolet Rays
D004276:DNA, Satellite