Target mRNAs are repressed as efficiently by microRNA-binding sites in the 5′ UTR as in the 3′ UTR

In animals, microRNAs (miRNAs) bind to the 3' UTRs of their target mRNAs and interfere with translation, although the exact mechanism of inhibition of protein synthesis remains unclear. Functional miRNA-binding sites in the coding regions or 5' UTRs of endogenous mRNAs have not been identified. We studied the effect of introducing miRNA target sites into the 5' UTR of luciferase reporter mRNAs containing internal ribosome entry sites (IRESs), so that potential steric hindrance by a microribonucleoprotein complex would not interfere with the initiation of translation. In human HeLa cells, which express endogenous let-7a miRNA, the translational efficiency of these IRES-containing reporters with 5' let-7…

• HH
  Howard Hughes Medical Institute
• YU
  Yale University
• FM
  Friedrich Miescher Institute for Biomedical Research
• NI
  National Institutes of Health

  Award: GM26154