A new regulatory circuit in ribosomal protein operons: S2-mediated control of the rpsB-tsf expression in vivo

• Published in: RNA (Cambridge) 2008-09, Vol.14 (9), p.1882-1894
• Main Authors: Aseev, Leonid V, Levandovskaya, Alexandrina A, Tchufistova, Ludmila S, Scaptsova, Nadezda V, Boni, Irina V
• Format: Article
• Language: English
• Subjects: 5' Untranslated Regions - chemistry; 5' Untranslated Regions - genetics; Base Sequence; beta-Galactosidase - genetics; Escherichia coli - genetics; Escherichia coli Proteins - genetics; Feedback, Physiological; Gene Expression Regulation, Bacterial; Molecular Sequence Data; Mutation; Operon; Peptide Elongation Factors - genetics; Phylogeny; Promoter Regions, Genetic; Protein Biosynthesis - genetics; Ribosomal Proteins - genetics; Ribosomal Proteins - metabolism; Transcription Initiation Site
• ISSN: 1355-8382; 1469-9001; 1469-9001
• DOI: 10.1261/rna.1099108

Autogenous regulation is a general strategy of balancing ribosomal protein synthesis in bacteria. Control mechanisms have been studied in detail for most of ribosomal protein operons, except for rpsB-tsf encoding essential r-protein S2 and elongation factor Ts, where even the promoter has remained unknown. By using single-copy translational fusions with the chromosomal lacZ gene and Western-blot analysis, we demonstrate here that S2 serves as a negative regulator of both rpsB and tsf expression in vivo, acting at a single target within the rpsB 5'-untranslated region (5'-UTR). As determined by primer extension, transcription of the Escherichia coli rpsB-tsf operon starts 162 nucleotides upstream of the rpsB initiation codon at a single promoter TGTGGTATAAA belonging to the extended -10 promoter class. Both the promoter signature and the 5'-UTR structure of the rpsB gene appear to be highly conserved in gamma-proteobacteria. Deletion analysis of the rpsB 5'-UTR within rpsB'-'lacZ fusions has revealed that an operator region involved in the S2 autoregulation comprises conserved structural elements located upstream of the rpsB ribosome binding site. The S2-mediated autogenous control is impaired in rpsB mutants and, more surprisingly, in the rpsA mutant producing decreased amounts of truncated r-protein S1 (rpsAIS10), indicating that S2 might act as a repressor in cooperation with S1.