Measuring metals with RNA

Abstract

In a recent issue of Cell, Winkler and coworkers (Dann et al., 2007) describe in atomic detail the structural changes that allow a specific RNA aptamer (the M box) to regulate transcription in response to changing cellular magnesium levels.

Figure 1

Role of the M-box aptamer in the transcriptional regulation of Bacillus subtilis mgtE gene. When Mg(II) levels are sub-optimal, transcription proceeds through the leader region RNA an into the mgtE structural gene. This process involves a stem-loop structure in which an anti-terminator element prevents formation of a transcription terminator. When Mg(II) levels are sufficient, the anti-terminator is instead sequestered into the stably folded structure of the M box aptamer, thereby allowing formation of a transcription terminator. The atomic structure reveals six bound Mg(II) ions in the folded M box aptamer that are implicated in this regulatory transition.