Although some reports have suggested that smaller RNAs derived from snoRNAs can have alternative, even miRNA-like functions, a Swiss research team now says that’s pretty darn rare. Did we mention the research team resides in the land of neutrality? So we naturally trust the data.
Of course, snoRNAs (small nucleolar RNAs) guide modifications onto other ncRNAs (non-coding RNAs), like rRNAs, snRNAs, and tRNAs. But how are snoRNAs processed? And can smaller RNAs that result from that processing function as miRNAs? The team decided to find out.
They performed PAR-CLIP, the slick combo of crosslinking and immunoprecipitation, to see which RNAs associated with proteins like fibrillarin, NOP56, and NOP58, which are in the ribonucleoprotein (RNP) complex of C/D box snoRNAs, and dyskerin, which is in the RNP complex of H/ACA snoRNAs.
“One of the interesting things we have learned is that high-throughput sequencing allows us to look deeper than we expected into the kinetics of some cellular processes. We can capture all sorts of intermediate processing products that we need to put into a coherent, dynamical picture,” shared author, Dr. Mihaela Zavolan.
Here’s some of the specifics of what the team learned:
- PAR-CLIP captured both snoRNAs and their targets.
- In their experiments, they found new C/D box and H/ACA snoRNAs.
- The researchers also found “C/D box-like” snoRNAs. These are expressed at very low levels, and some of them (“mini-snoRNAs”) are very short.
- Some mRNAs were crosslinked with the snoRNAs and their proteins, suggesting that snoRNAs could have a role in mRNA processing.
- Like other ncRNAs, snoRNAs are processed into smaller RNA fragments, which are abundant in cells. But unlike those other ncRNAs, these smaller RNAs don’t often associate with Argonaute proteins to act like miRNAs.
“We thus conclude that a microRNA-like function of snoRNA-derived small RNAs is an exception rather than a rule,” says the team.
Read more about the study at Genome Biology, May 2013.