(Alternate title: “circRNA censors the RNA censors?”)
When I was a kid, RNA played second fiddle to DNA. RNA was a mere intermediary between the ‘book of life’ (DNA) and the stuff the book coded for (proteins). But in the years since, RNA has shown itself to be a key player in the regulation of gene expression (shut up, DNA!). We now know of lots of kinds of non-coding RNA (ncRNA) that do lots of important things in cells, such as maintaining genomic integrity in the germ line (piRNA) and preventing messenger-RNA from being translated into protein (mi-, si- and lncRNA). Keeping track of these non-coding RNAs is tough (for me at least; I focused on fossils). Now, two in-press reports (Hansen et al., 2013; Memczak et al. 2013) show things aren’t getting any easier – apparently there’s also circular RNA (circRNA; reviewed by Kosik 2013).

Why is circRNA special? Well, for one thing, it’s two ends are joined together, forming a circle; the other types are just plain, boring, open-ended strands. Lame. Also, whereas miRNAs are involved in inhibiting gene expression (e.g., RNA interference) by binding to & helping destroy messenger RNA, circRNAs act as miRNA “sponges,” binding certain miRNA to alter their function. WHAT?!

Dammit, go home RNA; you’re drunk.

Someone smarter explaining it
Kosik, K. (2013). Molecular biology: Circles reshape the RNA world Nature DOI: 10.1038/nature11956

The papers
Hansen, T., Jensen, T., Clausen, B., Bramsen, J., Finsen, B., Damgaard, C., & Kjems, J. (2013). Natural RNA circles function as efficient microRNA sponges Nature DOI: 10.1038/nature11993

Memczak, S., Jens, M., Elefsinioti, A., Torti, F., Krueger, J., Rybak, A., Maier, L., Mackowiak, S., Gregersen, L., Munschauer, M., Loewer, A., Ziebold, U., Landthaler, M., Kocks, C., le Noble, F., & Rajewsky, N. (2013). Circular RNAs are a large class of animal RNAs with regulatory potency Nature DOI: 10.1038/nature11928