Figure 6.

miRNA abundance and architecture of the target site determine mRNA silencing. (top) Extensive complementarity (paired 3′) between a miRNA and a target site allows for efficient and specific silencing, independently of the miRNA level and the presence of imperfections in the seed match. (middle) Abundant miRNAs can silence targets carrying a perfect seed match or a nearly-perfect seed match (e.g. a peripheral G:U wobble), even in the absence of complementarity to the sequence outside the seed. A ‘central mismatch’ repels poorly complementary miRNAs. (bottom) Lowly abundant and poorly complementary miRNAs can silence targets carrying a perfect seed match, but not the ones carrying a seed match imperfection (e.g. peripheral G:U or central bulge). Green shading: functional site; pink shading: nonfunctional site. Magenta: seed/seed match