A few years back synthetic miRNA decoys, nicknamed “miRNA sponges”, were developed as an innovative new way to inhibit miRNA activity by bumping up the number of miRNA targets to “soak up” a specific miRNA. Now recent reports are popping up showing evidence that naturally occurring miRNA sponges have been around all along, we just didn’t notice them…once again proving that it isn’t easy to outsmart Mother Nature.
A new review article in Current Biology by Margaret Ebert and Phillip Sharp (who introduced the idea of miRNA sponges with their team at MIT) goes over those latest reports and discusses exactly what we know about the endogenous versions of these miRNA ShamWows®, as well as some ideas on what roles they might have. Here’s some of the new data they’re talking about:
- In plants, the non-coding RNA family TPSI contains a highly conserved binding site for miR-399, which seems to tweak the regulation of miR-399’s target PHO2.
- A study of HSV transformed Marmoset T cells found that viral non-coding transcripts called HSURs had targets sites for the miR-27 family, and that the miR-27 target gene FOXO1 gets upregulated when HSURs were around.
- The mammalian psuedogene PTENP1 contains most of the same miRNA binding sites as the full PTEN gene and therefore competes for the miRNA binding which modulates PTEN expression. This psuedogene-as-miRNA-sponge mechanism was demonstrated in prostate cancer cells.
The authors also suggest that other small RNA classes, like siRNAs or piRNAs may also have similar sponge-like, target decoy mechanisms at work. Soak in all of the spongy details in Current Biology, October 2010