shRNA versus siRNA - (Jan/30/2007 )

Hi hi,

I was wondering what the difference between using shRNA and siRNA really is. I have they both use the same mechanism for silencing except that shRNA contains an extra hairpin structure, but is that all? What is the advantage of using shRNA rather than siRNA? I read that shRNA is better for stable transfections but I thought siRNA can be used for stable transfections as well? What's the difference? Thankssss

for siRNA, if u want to continuosly see a silencing effect, u have to transfect it constantly, as siRNA gets degraded in the cells after a few days. (The level drops after 4-5 days). This is because siRNA does not get passed down after cell division.
For shRNA, its basis is the same as plasmid DNA. After stable transfection, the plasmid gets randomly integrated into the genome and gets passed down after replication (although u need to check it just to be sure. there are times, where it just gets "lost" after many passages)
hope it helps

same as sharonpek's explnantion.

O i see,

Does that mean that siRNA can only be used for transient transfections and shRNA for stable transfections?

siRNA:
you control the ratio: moles of duplex/ number of cells
less of-targets (non desired silenced targets)

shRNA:
You have less problem in transfecting, but you have more in the design of the vector,
you have to establish a stable cell line and test it for the silencing, but then as soon as you have it you have very reproducible results (in theory )
gives more off-targets because you don't control the promoter strength even if you can select a line of cell that only has one vector inside.