Deep sequencing from hen1 mutants to identify small RNA 3' modifications.

microRNAs (miRNAs) function via targeting of messenger RNAs, suppressing protein levels, and playing important roles in biological processes of plants and animals. The pathway for miRNA biogenesis is well established, but less is known about miRNA turnover, largely because of difficulties in capturing miRNAs during the process of decay, in which they are both rare and ephemeral. The HEN1 protein methylates the 3' terminus of small RNAs (sRNAs), protecting them from poly-urydilation and degradation. Recent progress using deep sequencing to study sRNAs in hen1 reveals the potential for hen1 mutants to serve as a platform for studies of miRNA turnover, with the sequencing data providing unprecedented precision and detail in the characterization of 3' modifications.