Human let-7 stem-loop precursors harbor features of RNase III cleavage products.
The bidentate RNase III Dicer cleaves microRNA precursors to generate the 21-23 nt long mature RNAs. These precursors are 60-80 nt long, they fold into a characteristic stem-loop structure and they are generated by an unknown mechanism. To gain insights into the biogenesis of microRNAs, we have characterized the precise 5' and 3' ends of the let-7 precursors in human cells. We show that they harbor a 5'-phosphate and a 3'-OH and that, remarkably, they contain a 1-4 nt 3' overhang. These features are characteristic of RNase III cleavage products. Since these precursors are present in both the nucleus and the cytoplasm of human cells, our results suggest that they are generated in the nucleus by the nuclear RNase III. Additionally, these precursors fit the minihelix export motif and are thus likely exported by this pathway.
Basyuk
Eugenia
E
IGMM-CNRS UMR 5535, IFR 24, 1919 Route de Mende, F-34293 Montpellier Cedex, France.
Suavet
Florence
F
Doglio
Alain
A
Bordonné
Rémy
R
Bertrand
Edouard
E
D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012322:RNA Precursors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D043244:Ribonuclease III / Q000378:metabolism*
D035683:MicroRNAs; D012322:RNA Precursors; D043244:Ribonuclease III