Mono-uridylation of pre-microRNA as a key step in the biogenesis of group II let-7 microRNAs

Cell. 2012 Oct 26;151(3):521-32. doi: 10.1016/j.cell.2012.09.022. Epub 2012 Oct 11.


RNase III Drosha initiates microRNA (miRNA) maturation by cleaving a primary miRNA transcript and releasing a pre-miRNA with a 2 nt 3' overhang. Dicer recognizes the 2 nt 3' overhang structure to selectively process pre-miRNAs. Here, we find that, unlike prototypic pre-miRNAs (group I), group II pre-miRNAs acquire a shorter (1 nt) 3' overhang from Drosha processing and therefore require a 3'-end mono-uridylation for Dicer processing. The majority of let-7 and miR-105 belong to group II. We identify TUT7/ZCCHC6, TUT4/ZCCHC11, and TUT2/PAPD4/GLD2 as the terminal uridylyl transferases responsible for pre-miRNA mono-uridylation. The TUTs act specifically on dsRNAs with a 1 nt 3' overhang, thereby creating a 2 nt 3' overhang. Depletion of TUTs reduces let-7 levels and disrupts let-7 function. Although the let-7 suppressor, Lin28, induces inhibitory oligo-uridylation in embryonic stem cells, mono-uridylation occurs in somatic cells lacking Lin28 to promote let-7 biogenesis. Our study reveals functional duality of uridylation and introduces TUT7/4/2 as components of the miRNA biogenesis pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • DNA-Binding Proteins / metabolism*
  • HeLa Cells
  • Humans
  • MicroRNAs / metabolism*
  • Molecular Sequence Data
  • Polynucleotide Adenylyltransferase / metabolism*
  • RNA Nucleotidyltransferases / metabolism*
  • RNA Processing, Post-Transcriptional*
  • RNA-Binding Proteins / metabolism
  • Uridine Monophosphate / metabolism*
  • mRNA Cleavage and Polyadenylation Factors


  • DNA-Binding Proteins
  • LIN-28 protein, human
  • MicroRNAs
  • RNA-Binding Proteins
  • TUT4 protein, human
  • mRNA Cleavage and Polyadenylation Factors
  • mirnlet7 microRNA, human
  • Uridine Monophosphate
  • RNA Nucleotidyltransferases
  • Polynucleotide Adenylyltransferase
  • TENT2 protein, human
  • TUT7 protein, human

Associated data

  • GEO/GSE40236