In this paper,a series of peptide-siRNA conjugates with phosphodiester unit as the linker targeting to Cdc2 gene were synthesized by solid phase stepwise strategy.The conjugation of peptides at either 3’-terminus of siCdc2 bring no change to the classical A-form of RNA duplex,but slightly compromise the thermodynamic stability.Peptide conjugation at the 3’-terminus of sense strand could improve the serum stability obviously,however,the opposite peptide conjugation at the 3’-terminus of antisense strand shows no such influence.According to the results of artificial silencing activity assay system,peptide conjugation at 3’-terminus of antisense strand slightly weakens the silencing activity of siCdc2.But sense strand peptide conjugation exhibits similar silencing activity as native siCdc2,meanwhile,it could mitigate the unwanted off-target effect of sense strand targeting to its own mRNA.
WANG XiaoFengHUANG YeLIU YangCHEN YueJIN HongWeiZHENG YiDU QuanYANG ZhenJunZHANG LiHe
In this study,a series of 5′-phosphorylated siRNAs with D-/L-isonucleotide(isoNA)or locked nucleic acid(LNA)incorporated at the 5′-terminus were synthesized.It was found that after incorporating either isoNA or LNA at the 5′-terminus of the antisense strand or sense strand,the silencing activity of modified strands has been inhibited,which cannot be recovered by phosphorylation at the 5′-terminus;however,the silencing activity of unmodified strand to its own target was increased.This work indicates that the isoNA and LNA modification at 5′-terminus can interfere with the strand selection during the RISC assembling process,and the disturbance of the 5′-phosporylation should not be the only viable mechanism.
A disulfde-modifed nucleoside was designed and synthesized. After loading the modifed nucleoside on controlled pore glass(CPG), solid phase synthesis strategy was used to prepare peptide–oligonucleotide conjugates(N-3') containing disulfde bond unit. The 3'-sense strand peptide–siRNA conjugate(VII) maintained good gene silencing activity, while that of the 3'-antisense strand conjugate decreased somewhat. And the sense strand off-target effect of VII decreased remarkably.
