A-to-I editing in mature miRNAs is enriched in seed sequence. (A) 73.33% (44/60) of the A-to-I editing events was found to be localized in the seed sequence of mature miRNAs whereas for C-to-U only 17.86% (10/56) were in the seed sequence. This enrichment is significantly (two-tailed proportional test, p = 6.66 × 10−9) higher for A-to-I compared to C-to-U. (B) Primary y-axis (bars) shows the number of editing events in the seed, the secondary y-axis (line) shows the percentage of adenine in seed sequences of all human mature miRNAs (miRBase20) and the x-axis shows the position within the seed (where position 1–7 corresponds to position 2–8 from the 5′-end of mature miRNAs). 19 out of 44 seed editing was located in the 4th (nine events) and 5th (ten events) positions of the seed (marked by black arrow) without a bias for adenine at that position in human mature miRNAs.