Poster abstracts

Poster number 14 submitted by Enrico Caserta

Mutational Analysis of the Bacillus subtilis glyQS T Box Gene

Enrico Caserta (Department of Microbiology, The Ohio State University), Frank J. Grundy (Department of Microbiology, The Ohio State University), Tina M. Henkin (Department of Microbiology, The Ohio State University)

Abstract:
The T box regulatory system in Gram-positive bacteria utilizes a complex set of conserved structural and sequence elements in the 5' untranslated region of the transcript to regulate the expression of a large number of amino-acid related genes through premature termination of transcription. Expression of each gene regulated by this mechanism is induced by a reduction in the aminoacylation level of the cognate tRNA. A purified in vitro transcription system and structural mapping studies have directly demonstrated that binding of the uncharged cognate tRNAGly to the leader region of the Bacillus subtilis glyQS gene (encoding glycyl-tRNA synthetase) stabilizes an antiterminator element that competes with formation of the intrinsic terminator helix. T box RNAs are therefore members of the riboswitch family, since the RNA rearrangement occurs in response to direct binding of the effector molecule. The specificity of the leader RNA-tRNA interaction is determined primarily by base pairing between a single codon in the leader RNA and the tRNA anticodon, and between the antiterminator and the unpaired residues at the acceptor end of the tRNA. However, additional interactions are likely to be required for efficient binding, and little is known about the tertiary structure of the leader RNA and the arrangement of leader RNA domains relative to the tRNA. In this study, a set of variants with alterations in the glyQS glycine codon and corresponding variants with alterations in the tRNAGly anticodon were tested to determine the effect of specific codon-anticodon mismatches on antitermination activity.

Keywords: T box, riboswitch, transcription termination