I know that the RISC (RNA-induced silencing complex) is one of the primary complexes involved in gene regulation through RNAi. What I want to know is, what role exactly does Dicer play in this complex?
Dicer is an endo-ribonuclease belonging to the RNAse-III class. Dicer is not a part of the RISC. It however helps in the formation of RISC by cleaving dsRNA or the stem of hairpin RNA on two ends which liberates a small dsRNA product. Then one of the strands is loaded into the RISC.
There are several reviews on this topic and there is a video as well which you can find on youtube.