Transcription Termination Control of the S Box System: Direct Measurement of S-Adenosylmethionine by the Leader RNA

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 100; no. 6; pp. 3083 - 3088
• Main Authors: Brooke A. Murphy Mc Daniel, Grundy, Frank J., Artsimovitch, Irina, Henkin, Tina M.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 18-03-2003; National Acad Sciences; The National Academy of Sciences
• Subjects: 5' Untranslated Regions - chemistry; 5' Untranslated Regions - genetics; 5' Untranslated Regions - metabolism; Bacillus subtilis - genetics; Bacillus subtilis - metabolism; Base Sequence; Biological Sciences; DNA; Escherichia coli - genetics; Escherichia coli - metabolism; Genes; Genes, Bacterial; Genetic mutation; Lac Operon; Measurement; Methionine Adenosyltransferase - genetics; Methionine Adenosyltransferase - metabolism; Models, Molecular; Molecular Sequence Data; Nucleic Acid Conformation; Operator regions; Operons; Polymerase chain reaction; Promoter regions; Ribonucleic acid; RNA; RNA, Bacterial - chemistry; RNA, Bacterial - genetics; RNA, Bacterial - metabolism; S-Adenosylmethionine - metabolism; Teeth; Terminator regions; Transcription, Genetic
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0630422100

Modulation of the structure of a leader RNA to control formation of an intrinsic termination signal is a common mechanism for regulation of gene expression in bacteria. Expression of the S box genes in Gram-positive organisms is induced in response to limitation for methionine. We previously postulated that methionine availability is monitored by binding of a regulatory factor to the leader RNA and suggested that methionine or S-adenosylmethionine (SAM) could serve as the metabolic signal. In this study, we show that efficient termination of the S box leader region by bacterial RNA polymerase depends on SAM but not on methionine or other related compounds. We also show that SAM directly binds to and induces a conformational change in the leader RNA. Both binding of SAM and SAM-directed transcription termination were blocked by leader mutations that cause constitutive expression in vivo. Overproduction of SAM synthetase in Bacillus subtilis resulted in delay in induction of S box gene expression in response to methionine starvation, consistent with the hypothesis that SAM is the molecular effector in vivo. These results indicate that SAM concentration is sensed directly by the nascent transcript in the absence of a trans-acting factor.