Activity of siRNAs with 2-thio-2'-O-methyluridine modification in mammalian cells.

In a search to identify chemical modifications to improve the properties of siRNA, we have investigated the effect of the 2 ′-O-methyl-2-thiouridine modification on the biological activity of siRNA. Our results indicate that judicious placement of 2 ′-O-methyl-2-thiouridine residues could lead to modified siRNA with activity in mammalian cells.