Has anyone seen target mRNA increasing after RNAi? - (Apr/11/2006 )
I am using dsRNA in Drosophila S2 cells to do RNAi knockdown. For tow genes, I detected increased mRNA using RT-PCR. I used full-length cDNA of the two gene to generate dsRNA. I wonder if anyone has seen this happening? BTW,four other similar experiments resulted in decreased mRNA.
At least two people in this forum have mentioned that they got enhanced expression of siRNA target genes. Although the situation may differ, but some possibilities are:
1) an interferon response triggered by siRNA or shRNA
2) siRNA mistargets another gene that in turn activate the true target gene
3) squence-specific gene activation by unknown mechanisms (this is possible!!!)
We have such experience in RNAi for plants and also learn a case from a friend, he said it might be many people found such change but nobody said that in paper yet...
by the way, you mentioned that you are using full-length cDNA of the two gene to generate dsRNA, although I am not sure the detail, but is there any chance that the transcript of the full-length cDNA has been detected by RT-PCR?
I have encountered the same problem. Can anyone give me a possible explaination?
I also had this problem last year. I found a very large mRNA expression enhancement, but thought it was a mistake. Just used a different siRNA sequence ...
I am glad someone else had the same problem. Just wondering what is it about. Could be a not known process?
Maybe the target gene has a negative feedback loop which is interrupted with the siRNA, so the gene finally is overexpressed ...
try this citation
Small dsRNAs induce transcriptional activation in human cells Hideki Enokida, and Rajvir Dahiya
Long-Cheng Li, Steven T. Okino, Hong Zhao, Deepa Pookot, Robert F. Place, Shinji Urakami,
PNAS published online Nov 3, 2006;
siRNA enahnced transcription in a sequence specific way. Interesting!