Systemic comparison of repression activity for miRNA and siRNA associated with different types of target sequences

► We did systemic comparison of repression activity for miRNA and siRNA associated with different types of target sequences. ► The level of repression could be ordered as follows: perfect-matched target ≫ dimeric targets ≫ monomeric targets. ► Fold repression of 8mer + 7mer-1A lay between 2 × 8mer and 2 × 7mer-1A. ► A mismatch in one seed dramatically decreasing repressive activity of the dimer indicating cooperation of two monomers. ► Strong repression of miR-155 and siRNA-155 (siRNA carrying miR-155 sequence) with perfectly matched target was due primarily to translational attenuation.