A Single Let-7 MicroRNA Bypasses LIN28-Mediated Repression

Cell Rep. 2015 Oct 13;13(2):260-6. doi: 10.1016/j.celrep.2015.08.086. Epub 2015 Oct 1.


Let-7 microRNAs (miRNAs) are critical regulators of animal development, stem cell differentiation, glucose metabolism, and tumorigenesis. Mammalian genomes contain 12 let-7 isoforms that suppress expression of a common set of target mRNAs. LIN28 proteins selectively block let-7 biogenesis in undifferentiated cells and in cancer. The current model for coordinate let-7 repression involves the LIN28 cold-shock domain (CSD) binding the terminal loop and the two CCHC-type zinc fingers recognizing a GGAG sequence motif in precursor let-7 (pre-let-7) RNAs. Here, we perform a systematic analysis of all let-7 miRNAs and find that a single let-7 family member, human let-7a-3 (and its murine ortholog let-7c-2), escapes LIN28-mediated regulation. Mechanistically, we find that the pre-let-7c-2 loop precludes LIN28A binding and regulation. These findings refine the current model of let-7 regulation by LIN28 proteins and have important implications for understanding the LIN28/let-7 axis in development and disease.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Base Sequence
  • HEK293 Cells
  • HeLa Cells
  • Hep G2 Cells
  • Humans
  • Mice
  • MicroRNAs / genetics*
  • Molecular Sequence Data
  • Protein Binding
  • Protein Structure, Tertiary
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / metabolism*


  • Lin28A protein, human
  • MicroRNAs
  • RNA-Binding Proteins
  • mirnlet7 microRNA, human
  • mirnlet7 microRNA, mouse