Position-specific chemical modification of siRNAs reduces "off-target" transcript silencing.
Transfected siRNAs regulate numerous transcripts sharing limited complementarity to the RNA duplex. This unintended ("off-target") silencing can hinder the use of RNAi to define gene function. Here we describe position-specific, sequence-independent chemical modifications that reduced silencing of partially complementary transcripts by all siRNAs tested. Silencing of perfectly matched targets was unaffected by these modifications. The chemical modification also reduced off-target phenotypes in growth inhibition studies. Key to the modification was 2'-O-methyl ribosyl substitution at position 2 in the guide strand, which reduced silencing of most off-target transcripts with complementarity to the seed region of the siRNA guide strand. The sharp position dependence of 2'-O-methyl ribosyl modification contrasts with the broader position dependence of base-pair substitutions within the seed region, suggesting a role for position 2 of the guide strand distinct from its effects on pairing to target transcripts.
Jackson
Aimee L
AL
Rosetta Inpharmatics, LLC, Seattle, WA 98109, USA. aimee_jackson@merck.com
Burchard
Julja
J
Leake
Devin
D
Reynolds
Angela
A
Schelter
Janell
J
Guo
Jie
J
Johnson
Jason M
JM
Lim
Lee
L
Karpilow
Jon
J
Nichols
Kim
K
Marshall
William
W
Khvorova
Anastasia
A
Linsley
Peter S
PS