RNA interference (RNAi) Question?

[rjm546]

Is this correct?


Most of RNA is single stranded. When a double stranded RNA comes into a cell it's usually a virus. This prompts short interfering RNAs to attack the double stranded RNA (because it knows it's foreign). BUT retroviruses (like HIV) are single stranded. Thus they are not attacked by siRNAs.

Could anyone let me know if that statement was correct/what's wrong with it? RNAi is a hard concept to grasp!! Thank you so much.

[Jon Moulton]

siRNAs are routinely used to cleave mRNA, which are single stranded. The guide strand of RNA on RISC binds to its target on RNA mostly through Watson-Crick base pairing, so it cannot recognize duplexed (double stranded) RNA unless regions of the RNA "open up" and allow access to single a stranded target. During the replication cycle of a dsRNA virus the viral RNA will sometimes be in single-stranded form and is then accessible to RISC.