Molecular Basis for Interaction of let-7 MicroRNAs with Lin28

Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
Cell (Impact Factor: 33.12). 11/2011; 147(5):1080-91. DOI: 10.1016/j.cell.2011.10.020
Source: PubMed

ABSTRACT MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate gene expression. Among these, members of the let-7 miRNA family control many cell-fate determination genes to influence pluripotency, differentiation, and transformation. Lin28 is a specific, posttranscriptional inhibitor of let-7 biogenesis. We report crystal structures of mouse Lin28 in complex with sequences from let-7d, let-7-f1, and let-7 g precursors. The two folded domains of Lin28 recognize two distinct regions of the RNA and are sufficient for inhibition of let-7 in vivo. We also show by NMR spectroscopy that the linker connecting the two folded domains is flexible, accommodating Lin28 binding to diverse let-7 family members. Protein-RNA complex formation imposes specific conformations on both components that could affect downstream recognition by other processing factors. Our data provide a molecular explanation for Lin28 specificity and a model for how it regulates let-7.

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