miRNA Targeting: Growing beyond the Seed.

miRNAs are small RNAs that guide Argonaute proteins to specific target mRNAs to repress their translation and stability. Canonically, miRNA targeting is reliant on base pairing of the seed region, nucleotides 2-7, of the miRNA to sites in mRNA 3' untranslated regions. Recently, the 3' half of the miRNA has gained attention for newly appreciated roles in regulating target specificity and regulation. In addition, the extent of pairing to the miRNA 3' end can influence the stability of the miRNA itself. These findings highlight the importance of sequences beyond the seed in controlling the function and existence of miRNAs.