pre-miRNA profiles obtained through application of locked nucleic acids reveals complex 5'/3' arm variation including concomitant cleavage and polyuridylation patterns

Recent research hints at an underappreciated complexity in pre-miRNA processing and regulation. Global profiling of pre-miRNA and its potential to increase understanding of the pre-miRNA landscape is impeded by overlap with highly-expressed classes of other non-coding RNA. Here we present a dataset excluding these RNA before sequencing through locked nucleic acids (LNA), greatly increasing pre-miRNA sequence counts with no discernable effects on pre-miRNA or mature miRNA sequencing. Analysis of profiles generated in total, nuclear, and cytoplasmic cell fractions reveals pre-miRNAs are subject to a wide range of regulatory processes involving loci-specific 3'- and 5'-end variation entailing complex cleavage patterns with co-occurring polyuridylation. Additionally, examination of nuclear-enriched flanking sequences of pre-miRNA, particularly those derived from polycistronic miRNA transcripts, provides insight into miRNA and miRNA-offset (moRNA) production. Our findings point to particularly intricate regulation of the let-7 family, introduce novel and unify known forms of pre-miRNA regulation and processing, and shed new light on the byproducts of miRNA processing pathways. none provided