Tertiary contacts control switching of the SAM-I riboswitch.

ABSTRACT: Riboswitches are non-coding RNAs that control gene expression by sensing small molecules through changes in secondary structure. While secondary structure and ligand interactions are thought to control switching, the exact mechanism of control is unknown. Using a novel two-piece assay that competes the anti-terminator against the aptamer, we directly monitor the process of switching. We find that the stabilization of key tertiary contacts controls both aptamer domain collapse and the switching of the SAM-I riboswitch from the aptamer to the expression platform conformation. Our experiments demonstrate that SAM binding induces structural alterations that indirectly stabilize the aptamer domain, preventing switching toward the expression platform conformer. These results, combined with a var

SUBMITTER: Hennelly SP 

PROVIDER: S-EPMC3064774 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature