The association of microRNAs with Argonaute proteins (AGOs) yields complexes regulating gene expression. Although bacterial and archaeal miRNAs show no sequence preference at their 5′ ends, eukaryotic miRNAs tend to have a 5′ U or A. Here the structure of the human AGO2 MID domain complexed with ribonucleotide monophosphates is solved, revealing specific interaction of UMP and AMP with a loop that discriminates against CMP or GMP, and explaining the observed preference.
- Filipp Frank
- Nahum Sonenberg
- Bhushan Nagar
