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Caught in the Circle

Circular non-coding RNA can bind and block microRNAs, affecting gene expression, according to two studies appearing in the online early version of Nature last week.

"There seems to be a whole new layer of gene regulation," Jørgen Kjems from Aarhus University in Denmark tells LiveScience.

In their paper, Kjems and his Aarhus University colleagues report that a circular RNA found in human and mouse brains binds and holds on to miR-7. This, they add, leads to increased activity of the genes miR-7 usually targets for suppression. Another circRNA, found in the testis, targets a separate microRNA, miR-138, suggesting to the researchers that these "sponge" effects of circular RNA "are a general phenomenon."

Indeed, a separate group of investigators at Max-Delbrück-Center for Molecular Medicine reports similar findings. They report finding a number of stable circRNAs that are commonly expressed in certain tissues or at particular developmental stages. Further, they show in zebrafish that changes to the circRNA or to miR-7 affect brain development. This, they add, provide evidence that circRNA act as post-transcriptional regulators.

"It's yet another terrific example of an important RNA that has flown under the radar," notes Erik Sontheimer from Northwestern University in a Nature News piece. "You just wonder when these surprises are going to stop."