3′ miRNA addition across organisms. (A) Proportion of miRNA loci found to have single nucleotide unambiguous addition significantly greater than expected error rate (see Methods) across seven deep-sequenced short RNA libraries in four species. Sets of miRNA loci with adenine addition (B) and uridine addition (C) found to have significant amounts of addition in multiple vertebrate species. miRNA loci shaded in gray have significant addition in three of the four human cell lines; loci shaded in black have significant addition in all four human cell lines. Comparison of the proportion of unambiguous adenine (D) and uridine (E) addition for individual miRNA loci in the four human cell lines; Spearman's correlation and P-values are given in the corners of individual scatterplots.
