Analysis of the Bacillus subtilis genome sequence reveals nine new T‐box leaders

• Published in: Molecular microbiology Vol. 29; no. 2; pp. 662 - 664
• Main Authors: Chopin, Alain, Biaudet, Véronique, Ehrlich, S. Dusko
• Format: Journal Article
• Language: English
• Published: Oxford BSL Blackwell Science Ltd, UK 01-07-1998; Blackwell Publishing Ltd; Wiley
• Subjects: Bacillus subtilis - genetics; Base Sequence; Conserved Sequence; Gene Expression Regulation, Bacterial; Genes, Bacterial; Genome, Bacterial; Life Sciences; Microbiology and Parasitology; Transcription, Genetic
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1046/j.1365-2958.1998.00912.x

The T-box family includes some 20 genes of Gram-positive bacteria encoding either aminoacyl-tRNA synthetases or amino acid biosynthesis enzymes. They are preceded by leader regions sharing conserved features and are regulated by a common transcription antitermination mechanism involving interaction of the leader transcript with the cognate uncharged tRNA. All T-box leaders contain a transcription terminator upstream of the coding sequence. The sequence immediately upstream of the terminator, and extending within its 5' part, has the potential to form an alternative, but much less stable, antiterminator structure, in which a sequence, called the T box, is highly conserved. The T-box leader transcripts also have in common other putative stem-loop structures. Most conserved is a complex stem structure, at the 5' end of the transcript, where a loop, close to the basis of the stem, contains a triplet designated the specifier codon. This codon specifies the amino acid expected to regulate the expression of the system. In addition to the conserved sequences involved in the formation of the terminator/antiterminator structures, several short sequences are conserved, with some degeneracy, in almost all leaders. The conservation of these features suggested a regulatory model in which antitermination is mediated by interaction between the leader transcript and uncharged cognate tRNA. This interaction is likely to involve on one hand, the specifier codon and the anticodon, and on the other, the tRNA acceptor arm and the 'anti-acceptor', a 4 nt sequence within the T box as mutations in these regions strongly affect antitermination.