Figure 1

Cartoon representing the major enzymes involved in the overlapping branches of the siRNA and the miRNA pathways in Drosophila melanogaster. While this cartoon was designed to emphasize the differences between the two pathways, it is important to stress that there is also extensive interaction and overlap between the two branches (some of which are represented by dotted arrows). This latter point is discussed in more detail in the text. [siRISC: RNA Induced Silencing Complex associated with siRNA; miRISC: miRNA associated RISC; miRNP: miRNA associated Ribo-Nucleo Protein complex; Ago: Argonaute (exhibits slicer activity); Dcr: Dicer; Spn-E: Spindle-E protein (involved in assembly of RISC); PIWI (co-purifies with Dcr-1 in Drosophila germline cells); R2D2 (bridges initiator and effector steps of siRNA pathway); ATP: adenosine triphosphate] [11, 12, 46, 51–57].