Mono-uridylation of pre-microRNA as a key step in the biogenesis of group II let-7 microRNAs.
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.
Institute for Basic Science, Seoul National University, Seoul 151-742, Korea.
Inha
I
Heo
Minju
M
Ha
Jaechul
J
Lim
Mi-Jeong
MJ
Yoon
Jong-Eun
JE
Park
S Chul
SC
Kwon
Hyeshik
H
Chang
V Narry
VN
Kim
D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D008969:Molecular Sequence Data; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism*; D012316:RNA Nucleotidyltransferases / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D016601:RNA-Binding Proteins / Q000378:metabolism; D014542:Uridine Monophosphate / Q000378:metabolism*; D039221:mRNA Cleavage and Polyadenylation Factors
D004268:DNA-Binding Proteins; C000715187:Lin28A protein, human; D035683:MicroRNAs; D016601:RNA-Binding Proteins; C511130:TUT4 protein, human; D039221:mRNA Cleavage and Polyadenylation Factors; C487931:mirnlet7 microRNA, human; D014542:Uridine Monophosphate; D012316:RNA Nucleotidyltransferases; D011062:Polynucleotide Adenylyltransferase; C550174:TENT2 protein, human; C576505:TUT7 protein, human