A new regulatory circuit in ribosomal protein operons: S2-mediated control of the rpsB-tsf expression in vivo.
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.
Aseev
Leonid V
LV
Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997, Moscow, Russia.
Levandovskaya
Alexandrina A
AA
Tchufistova
Ludmila S
LS
Scaptsova
Nadezda V
NV
Boni
Irina V
IV
D020121:5' Untranslated Regions / Q000737:chemistry / Q000235:genetics; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics*; D025461:Feedback, Physiological; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D009876:Operon; D010445:Peptide Elongation Factors / Q000235:genetics*; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis / Q000235:genetics; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism*; D024363:Transcription Initiation Site; D001616:beta-Galactosidase / Q000235:genetics
D020121:5' Untranslated Regions; D029968:Escherichia coli Proteins; D010445:Peptide Elongation Factors; D012269:Ribosomal Proteins; C023512:elongation factor Ts; C015494:ribosomal protein S1; C030004:ribosomal protein S2; D001616:beta-Galactosidase