Small RNAs in H9 embryonic stem cells

Non-templated 3'-end oligouridylation of RNA occurs in many species, including humans. Unlike the familiar phenomenon of polyadenylation, non-templated addition of uridines to RNA is poorly characterized in higher eukaryotes. Recent studies have reported non-templated 3'-end oligouridylation of small RNAs and mRNAs. Oligouridylation is involved in many aspects of microRNA biology from biogenesis to turnover of the mature species and it may also mark long mRNAs for degradation by promoting decapping of the protective 5'-cap structure. To determine the prevalence of oligouridylation in higher eukaryotes, we used next-generation sequencing technology to deeply examine the population of small RNAs in human cells. Our data revealed widespread non-templated nucleotide addition to the 3'-ends of many classes of RNA, with short stretches of uridine being the most frequently added nucleotide. Strand-specific RNA-Seq and paired-end sequencing was used to directly analyze the 3'-ends of small RNAs to identify post-transcriptional RNA processing.