Similarities of the RNase III domain (catalytic domains + dsRBM) of the human, mouse, Drosophila and C. elegans RNase III orthologues. Multiple amino acid sequence alignment was performed using the CLUSTALW and Align programs. For the mouse orthologue, the first amino acid shown corresponds to amino acid 892 in the complete sequence (see Additional File 1). Blue: acidic residues; Pink, basic residues; Green, hydrophilic residues; Red, hydrophobic residues. The symbols below the sequence refer to level of conservation: asterisk, completely conserved; colon and period: decreasing levels of conservation.