Small RNA profiles following TUT knock-down in HeLa

The precise control of microRNA (miRNA) biogenesis is important for various cellular functions, and its dysregulation is often associated with human diseases. We previously reported that Terminal uridylyl transferase 4 (TUT4) down-regulates let-7 miRNA biogenesis by oligo-uridylating let-7 precursor (pre-let-7) in mouse embryonic stem cells and that a pluripotency marker Lin28 promotes a processivity of TUT4. Here we find that TUT4 positively controls let-7 biogenesis by adding a uridine residue to the 3' end of pre-let-7 in the absence of Lin28. Such mono-uridylation enhances Dicer processing by generating an optimal end structure of pre-let-7 for Dicer recognition and may protect pre-miRNA from trimming. Moreover, TUT7, TUT4 and TUT2 redundantly regulate pre-let-7 processing and simultaneous knock down of these TUTs leads to the decrease of mature let-7 and the accumulation of pre-let-7 in cells. This study provides a novel regulation mechanism of miRNA biogenesis, which may function in development and tumorigenesis. Overall design: HeLa cells were transfected with siRNA two times over a 4~5 day period.