Synthesis and properties of double-stranded RNAs (dsRNAs) and small interfering RNAs (siRNAs) containing 4'-C-aminoethyl-2'-deoxy-2'-fluorouridine are described. Thermal denaturation studies showed that incorporation of 4'-C-aminoethyl-2'-fluoro analog improved the thermal stabilities of dsRNAs and siRNAs compared to the corresponding 4'-C-aminoethyl-2'-O-methyl analog. siRNA incorporating eight 4'-aminoethyl-2'-fluoro analogs in the passenger strand showed sufficient RNAi activity at 1 nM concentration, which was similar to that of the unmodified siRNA. Furthermore, the siRNA containing the 4'-C-aminoethyl-2'-fluoro analog exhibited high stability in a buffer containing 20% bovine serum. Forty-eight percent of the siRNA remained intact after 48 h of incubation. Thus, modification of siRNAs by the 4'-C-aminoethyl-2'-fluoro analog would be useful for the development of therapeutic siRNA molecules.
Keywords: 2′-Fluoro substituent; 4′-Aminoalkyl group; Nuclease resistance; RNA interference; Small interfering RNA; Thermal stability.
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