RNAi and interferon induction - (Jul/24/2007 )

Hello:

Being relatively new to RNAi...

What's the bottom line on interferon induction? It seems that length <30 per se does not eliminate the possibility based on the literature. However, what do the commercial sources say -- are their chemically-modified RNAs incapable of inducing interferon, or does it still remain a possibility, or does length of the RNA matter? What's the deal?

Thanks.

I strongly disagree with published data saying that synthetic siRNA can induce interferon response. We did the same type of experiments and found none.

With invitro stuff, we did look for interferon but failed to find any. Then we found that the cells lacked the receptors or something related to initiate the response.

We tried shRNA in AAV invivo. Even after a year, we didnt find a hint of any interferon response.

The first paper reporting siRNA initiated interferon response did not give their siRNA sequences in the paper or supplementary. It is ridiculous that for such a potentially important observation no sequence was given. I wrote to and called the senior author asking for the sequences, he simply ignored my request.

well... Here are some references that may be useful for you, underlying siRNA ant interferon pathway.

*Activation of the interferon system by short-interfering RNAs., *nat cell bio, par Sledz et al.
http://www.ncbi.nlm.nih.gov/entrez/query.f...l=pubmed_docsum

*RNA interference and double-stranded-RNA-activated pathways.*
http://www.ncbi.nlm.nih.gov/entrez/query.f...l=pubmed_docsum

The STAT 1 protein is also a central protein involved in the interferon patway. According to Wen and al. (Cell 82:241-50), STAT 1 can be phosphorylated on 2 particular aminoacid residues, the tyr 701 and the ser 727. But this article shows that this is the phosphorylation on the Tyr 701 which is the tough point.

i'm dealing with in vivo assays with siRNA. Recently i tested successfully the phospho stat 1. My positive controlshowed a signal but non on the negaive control or in my samples...

Thanks for your responses.

I understand that the papers showing IFN induction may have had problems: some were transcribed with T7 Pol and others with Pol III (with an aberrant dinucleotide initiation).

My question is regarding synthetic oligos -- is it safe to assume that they do not induce IFN? Does this depend on length (e.g. <30bp no worries?). Has there been published induction of IFN with synthetic oligos at all?