Talk abstracts

Talk on Saturday 11:20-11:35am submitted by Nicholas Green

The T box - Analysis of a Complex RNA Regulatory Element

Nicholas J. Green (Microbiology, The Ohio State University), Frank J. Grundy (Microbiology, The Ohio State University), Tina M. Henkin (Microbiology, The Ohio State University)

Abstract:
Many aminoacyl-tRNA synthetase (aaRS) genes and other amino acid related genes in Gram-positive bacteria are regulated by the T box transcription termination mechanism. In this system, the nascent leader RNA transcript senses the charging ratio of the cognate tRNA through specific base pairing interactions. Expression of an individual gene is induced by limitation for its cognate amino acid, which results in reduced charging of the cognate tRNA. Readthrough of a termination helix in the leader region of the transcript and expression of the downstream gene relies on stabilization of an antiterminator helix through interactions with the uncharged tRNA, preventing the formation of a terminator helix and allowing synthesis of the full length mRNA.

Specific interactions of the anticodon and the acceptor end of the tRNA with the transcribed leader RNA have been well-characterized by genetic and biochemical methods, supporting the structural transition of the terminator helix and the proposed secondary structure model. However, less is known about the tertiary structure of the leader RNA or the functional role of other conserved sequence elements. Chemical and enzymatic mapping of the 5' UTR of the Bacillus subtilis glyQS operon (encoding glycyl-tRNA synthetase) has revealed novel tRNA-induced changes at nucleotides near two of these conserved regions, specifically the AG bulge (AG) and the terminal loop of Stem I (ITL). Mutation of these conserved regions in Stem I is discussed, focusing on mutations in the AG that can functionally compensate for deficiencies caused by mutations in the ITL.

References:
Grundy FJ, Henkin TM. tRNA as a positive regulator of transcription antitermination in B. subtilis. Cell. 1993 Aug 13; 74(3):475-82.

Grundy FJ, Henkin TM. The T box and S box transcription termination control systems. Front Biosci. 2003 Jan 1; 8:d20-31.

Rollins SM, Grundy FJ, Henkin TM. Analysis of cis-acting sequence and structural elements required for antitermination of the Bacillus subtilis tyrS gene. Mol Microbiol. 1997 Jul; 25(2):411-21.

Yousef MR, Grundy FJ, Henkin TM. Structural transitions induced by the interaction between tRNA(Gly) and the Bacillus subtilis glyQS T box leader RNA. J Mol Biol. 2005 Jun 3; 349(2):273-87.

Keywords: RNA Structure, Transcription regulation, Bacteria