Sm. Gryaznov et Dh. Lloyd, MODULATION OF OLIGONUCLEOTIDE DUPLEX AND TRIPLEX STABILITY VIA HYDROPHOBIC INTERACTIONS, Nucleic acids research, 21(25), 1993, pp. 5909-5915
Synthetic oligonucleotides have been proposed as a new rationally desi
gned class of pharmaceuticals with a mechanism of action based upon a
Watson - Crick and/or Hoogsteen type of base pairing with RNA or DNA r
egions of interest. Two series of 3'-cholesterol and/or 5'-cholesterol
conjugated oligonucleotides have been synthesized. The primary struct
ure of these compounds was conceived in a way that should allow a hydr
ophobic interaction to take place upon bringing the cholesteryl moieti
es into proximity via a hybridization event. In the first group of com
pounds the cholesteryl group was tethered to the opposite ends of two
oligonucleotides, tandemly addressed to the same complementary strand.
An increase in the Tm of duplexes up to 13.3 degrees C was observed i
n comparison to unmodified oligomers. We observed a higher level of mi
smatch discrimination for the two contiguous oligonucleotide cholester
ol conjugates compared to one continuous oligomer of the same length.
A second group of compounds was synthesized as 5',3'-bischolesterol co
ntaining oligomers, capable of forming 'clamp-shaped' triple-stranded
complexes, where cholesterol groups were attached to the termini of du
plex and tripler forming domains. Stabilization of triplexes by up to
30 degrees C due to inter-cholesteryl interaction was observed. We det
ected no tripler formation with a mismatched target. These data sugges
t that significant stabilization of complexes of nucleic acids could b
e achieved through inter-cholesteryl hydrophobic interaction.