C. Escude et al., LIGAND-INDUCED FORMATION OF TRIPLE HELICES WITH ANTIPARALLEL 3RD STRANDS CONTAINING G AND T, Biochemistry, 35(18), 1996, pp. 5735-5740
We have examined the effects of benzopyridoindole derivatives on tripl
e helices with antiparallel third strands. Absorption spectroscopy, fo
otprinting, and gel retardation experiments demonstrate that a benzopy
ridoindole derivative (BePI) is able to induce formation of a triple h
elix with an antiparallel (G,T)-containing third strand, which does no
t form in the absence of this ligand. This triple-helical complex is v
ery stable with a half-dissociation temperature as high as 51 degrees
C, and its formation is pH independent. Antiparallel oligonucleotides
containing thymine and guanine bind strongly to double-helical DNA und
er physiological conditions in the presence of only 0.5 mu M BePI. For
mation of a BePI-stabilized triple helix strongly inhibits cleavage of
the target duplex by DNase I.