RNA silencing pathways. Long dsRNA and shRNA or miRNA precursors are processed to siRNA or miRNA by the double-stranded RNA binding and RNase III–like enzyme Dicer into 21 to 23 nucleotide dsRNA intermediates. These are subsequently unwound and assembled into the RNA-induced silencing complex (RISC; siRNAs), which directs RNA cleavage, or into an miRNA-effector complex termed miRNP, which directs translational repression (mRNA target identified by the 5′cap, 7 mG, and poly A tail).