Helix-stabilizing compounds CC-1065 and U-71,184 bind to RNA-DNA and DNA-DNA duplexes containing modified internucleotide linkages and stabilize duplexes against thermal melting.

Abstract

CC-1065 and U-71,184 bind and hyperstabilize DNA duplexes, but little is known about their effects on nucleic acid duplexes of different structure. A 20 mer DNA sequence (5'-TTACTTCAGTTATGAGACCA) containing a drug binding sequence (5'-AGTTA) was selected as the target sequence, and this was duplexed with complementary antisense sequences containing phosphodiester (PO), phosphorothioate (PS), and methylphosphonate (MP) bonds. The duplexes containing PO or PS bound 2 CC-1065 molecules per duplex, presumably at both the target site and at a lower affinity site (5'-AGTAA) on the antisense strand. The duplex containing MP bound only 1 CC-1065, and all duplexes bound only 1 U-71,184. Both CC-1065 and U-71,184 bound to 20 mer duplexes comprised of oligo(dA)-oligo(dT) (2.5 and 2 drugs per duplex, respectively) and poly(rA)-oligo(dT) (1 drug per 20 base pairs). CC-1065 also bound to duplexes between the PO- or PS-based antisense structures and a complementary synthetic 20 mer RNA sequence, with about 1 drug per duplex in each case. CC-1065 increased the Tm for the 20 mer DNA duplexes 17 to 29 degrees C, and the corresponding values for U-71,184 ranged from 7 to 19 degrees C. CC-1065 raised the Tm of oligo(dA)-oligo(dT) and poly(rA)-oligo(dT) 29 degrees C. U71,184 increased the Tm for oligo(dA)-oligo(dT) 30 degrees C but did not significantly elevate the Tm for the corresponding RNA-DNA duplex. The results show that CC-1065 and U-71,184 are capable of binding and stabilizing a variety of nucleic acid duplexes. These agents or their analogs may become useful ligands for antisense oligonucleotide applications.