The RNase activity of C3PO is required for RISC activation. A Partial multisequence alignment of Translin and Trax. A predicted endonuclease active site specific to trax is highlighted magenta. Residues conserved in both translin and trax are highlighted black. B Modeled structure of Drosophila Trax based on crystal structure of human Translin (PDB ID: 1j1j). The positions of the putative catalytic Asp and Glu residues are indicated by magenta spheres; other highly conserved Glu residues are in black spheres.