FTIR study of a nonclassical dT10*dA10-dT10 intramolecular triple helix.
Many early investigations on triple helices have been devoted to the study of the triplex formed by dT*dA-dT base triplets in which the third strand is oriented parallel to the dA strand. We now describe an intramolecular triple helix with dT*dA-dT base triplets in which the pyrimidine third strand is oriented antiparallel, formed by folding back twice the tridecamer dT10-linker-dA10-linker-dT10 (linker = pO(CH2CH2O)3p). Third-strand base pairing to the target strand, sugar conformation, and thermal denaturation of the triplex have been studied by Fourier transform infrared spectroscopy. Our results confirm than when the third-strand orientation is reversed from parallel to antiparallel with respect to the target strand, the third-strand hydrogen-bonding scheme is changed from Hoogsteen to reverse Hoogsteen. The sugar conformation in this triple helix is of the S type (C2'endo/anti, B family form) from all strands. Our results are discussed with respect to models for triplexes proposed as intermediates in homologous recombination [Zhurkin, V.B., Raghunathan, G., Ulyanov, N.B., Camerini-Otero, R.D., & Jernigan, R.L. (1994) J. Mol. Biol. 239, 181-200].
Dagneaux
C
C
Laboratoire de Spectroscopie Biomoléculaire, URA CNRS 1430, UFR de Médecine, Université Paris XIII, Bobigny, France.
Liquier
J
J
Taillandier
E
E
D000818:Animals; D001482:Base Composition; D004247:DNA / Q000737:chemistry*; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D011061:Poly A / Q000737:chemistry*; D011071:Poly T / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013696:Temperature
C051802:triplex DNA; D011061:Poly A; D011071:Poly T; C015465:poly(dA); D004247:DNA