Synthesis, structure and thermodynamic properties of 8-methylguanine-containing oligonucleotides: Z-DNA under physiological salt conditions

Hiroshi Sugiyama, Kiyohiko Kawai, Atsushi Matsunaga, Kenzo Fujimoto, Isao Saito, Howard Robinson, Andrew H.J. Wang

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87 Citations (Scopus)

Abstract

Various oligonucleotides containing 8-methylguanine (m8G) have been synthesized and their structures and thermodynamic properties investigated. Introduction of m8G into DNA sequences markedly stabilizes the Z conformation under low salt conditions. The hexamer d(CGC[m8G]CG)2 exhibits a CD spectrum characteristic of the Z conformation under physiological salt conditions. The NOE-restrained refinement unequivocally demonstrated that d(CGC[m8G]CG)2 adopts a Z structure with all guanines in the syn conformation. The refined NMR structure is very similar to the Z form crystal structure of d(CGCGCG)2, with a root mean square deviation of 0.6 between the two structures. The contribution of m8G to the stabilization of Z-DNA has been estimated from the mid-point NaCl concentrations for the B-Z transition of various m8G-containing oligomers. The presence of m8G in d(CGC[m8G]CG)2 stabilizes the Z conformation by at least ΔG = -0.8 kcal/mol relative to the unmodified hexamer. The Z conformation was further stabilized by increasing the number of m8Gs incorporated and destabilized by incorporating syn-A or syn-T, found respectively in the (A,T)-containing alternating and non-alternating pyrimidine-purine sequences. The results suggest that the chemically less reactive m8G base is a useful agent for studying molecular interactions of Z-DNA or other DNA structures that incorporate syn-G conformation.

Original languageEnglish
Pages (from-to)1272-1278
Number of pages7
JournalNucleic Acids Research
Volume24
Issue number7
DOIs
Publication statusPublished - 1996
Externally publishedYes

ASJC Scopus subject areas

  • Genetics

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