Gene silencing by RNAi

Dicer cuts dsRNA into 21- to 25-bp siRNA or miRNA segments that are then denatured by RISC. RISC–guide strand complexes can degrade targeted mRNAs, block translation of target mRNAs, or enter the nucleus to modify chromatinDicer cuts dsRNA into 21- to 25-bp siRNA or miRNA segments that are then denatured by RISC. RISC–guide strand complexes can degrade targeted mRNAs, block translation of target mRNAs, or enter the nucleus to modify chromatin

Exogenous dsRNA (e.g., dsRNA virus) W0 Cell membrane Cytoplasm Dicer cuts RNA into 21—25 hp , \ Pre-siRNA RISC denatures Passenger strand RNA degraded) W strand eTranscriptional 1‘ Binds ’0 silencing of mRNA by targeted complementary genes base pairing Transcription of microRNA genes 0 mRNA destroyed or 0 Translation blocked