title: A 5'-uridine amplifies miRNA/miRNA* asymmetry in Drosophila by promoting RNA-induced silencing complex formation.
abstract: BACKGROUND
  MicroRNA (miRNA) are diverse in sequence and have a single known sequence bias: they tend to start with uridine (U).
  
  
  RESULTS
  Our analyses of fly, worm and mouse miRNA sequence data reveal that the 5'-U is recognized after miRNA production. Only one of the two strands can be assembled into Argonaute protein from a single miRNA/miRNA* molecule: in fly embryo lysate, a 5'-U promotes miRNA loading while decreasing the loading of the miRNA*.
  
  
  CONCLUSIONS
  We suggest that recognition of the 5'-U enhances Argonaute loading by a mechanism distinct from its contribution to weakening base pairing at the 5'-end of the prospective miRNA and, as recently proposed in Arabidopsis and in humans, that it improves miRNA precision by excluding incorrectly processed molecules bearing other 5'-nt.
authors.affiliation: Laboratoire de Biologie Moléculaire Eucaryote, 118 route de Narbonne, Université Toulouse III Paul Sabatier (UPS), F-31000 Toulouse, France. seitz@ibcg.biotoul.fr.
authors.forename: Hervé
authors.initials: H
authors.lastname: Seitz
authors.forename: Jogender S
authors.initials: JS
authors.lastname: Tushir
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Zamore