Talk abstracts

Talk on Friday 01:30-01:50pm submitted by Jerneja Tomsic

In vivo and in vitro studies of a SAM-binding riboswitch

Jerneja Tomsic (Department of Microbiology, The Ohio State University), Frank J. Grundy (Department of Microbiology, The Ohio State University), Brooke A. McDaniel (Department of Microbiology, The Ohio State University), Tina M. Henkin (Department of Microbiology, The Ohio State University)

Abstract:
A number of systems have recently been discovered in which gene expression is regulated through direct sensing of regulatory signals by nascent RNA transcripts. In systems of this type, the effector molecules directly bind to the target RNA, modulating its structure and affecting the expression of downstream coding sequence(s). In the S-box transcription termination control system, which is used primarily in low G+C Gram positive bacteria, binding of S-adenosylmethionine (SAM) to the leader RNA stabilizes an anti-antiterminator element that prevents formation of the antiterminator element, promoting the formation of the helix of an intrinsic transcriptional terminator. In Smk box RNAs, recently discovered in lactic acid bacteria, binding of SAM causes an RNA structural rearrangement that sequesters the Shine-Dalgarno (SD) sequence, resulting in translational control of gene expression. Each set of SAM-binding riboswitch RNAs exhibits a complex set of conserved sequence and structural elements in the 5’ region of the RNA that are essential for SAM-dependent regulation, but the two classes of RNAs differ markedly in structure. SAM recognition in both of these systems has been shown to be highly specific, but the molecular basis for binding specificity is not yet understood. This study was designed to further characterize the SAM binding properties of the S-box RNA, and to compare the binding properties of different SAM-binding RNAs in vivo and in vitro.

Keywords: S-adenosylmethionine, riboswitch, transcription termination