When it comes to the the miRNA translational repression model, 5’ UTRs have been neglected more than California’s budget deficit in recent years. Despite computational approaches predicting oodles of miRNA docking sites for miRNAs in the 5’ UTR, we haven’t seen that many studies tackle the other side of miRNA repression.
But just a few days ago a team of researchers from University Michigan showed that miRNAs can be bipartisan when it comes to where they target. Actually, not only are some miRNAs happy to dock with 5’ UTRs (as well as 3′), but they also have no problem nabbing both UTRs simultaneously, creating a new target class that the researchers refer to as miBridge.
Using reporter assays, the team took a close look at human miR-34a and the AXIN2 gene, which has miR-34a binding motifs in both UTRs. They found that miR-34a repressed AXIN2 expression when either UTR motifs were available, but tightened its translational choke hold when both 5’ and 3’ UTR motifs were present.
Requiring binding motifs in both UTRs, the miBridge target class can substantially reduce the number of mRNA targets churned out by target prediction algorithms and might provide a way to investigate some less conserved miRNAs too, but that’s just the first course of great work in this paper so check out all the details at: Genome Research, July 2009