Pairing probability profiles for miRNA with and without 3′ addition events. (A) Boxplots depict the pairing probabilities, and by extension the double-stranded character, of individual nucleotide positions in miRNA at positions 1–19. Boxplots to the left depict the double-stranded character of the set of miRNA with significant unambiguous A addition conserved across human THP-1, human HeLa, and mouse embryonic stem cells. Boxplots to the right depict double-stranded character of the set of miRNA that never show significant addition across the same cell types. Plots to the top are constructed with the sequences of human miRNA; plots to the bottom are constructed with the sequences of mouse miRNA. (B) P-values of Wilcoxon rank sum test comparing pairing probabilities at nucleotide positions 1–19 across miRNA with addition and without addition are plotted. Red line plotted at P = 0.05, the level of significance. Positions with conserved significance across human and mouse miRNA are highlighted in yellow. (C,D) Same as A, B, but testing the set of miRNAs with conserved unambiguous uridine addition.
