Structure and regulation of the Salmonella typhimurium rnc-era-recO operon.
The Escherichia coli rnc-era-recO operon encodes ribonuclease III (RNase III; a dsRNA endonuclease involved in rRNA and mRNA processing and decay), Era (an essential G-protein of unknown functions and RecO (involved in the RecF homologous recombination pathway). Expression of the rnc and era genes is negatively autoregulated: RNase III cleaves the rncO 'operator' in the untranslated leader, destabilizing the operon mRNA. As part of a larger effort to understand RNase III and Era structure and function, we characterized rnc operon structure, function and regulation in the closely related bacterium Salmonella typhimurium. Construction of a S typhimurium strain conditionally defective for RNase III and Era expression showed that Era is essential for cell growth. This mutant strain also enabled selection of recombinant clones containing the intact S typhimurium rnc-era-recO operon, whose nucleotide sequence, predicted protein sequence, and predicted rncO RNA secondary structure were all highly conserved with those of E coli. Furthermore, genetic and biochemical analysis revealed that S typhimurium rnc gene expression is negatively autoregulated by a mechanism very similar or identical to that in E coli, and that the cleavage specificities of RNase IIIs.t. and RNase IIIE.c. are indistinguishable with regard to rncO cleavage and S typhimurium 23S rRNA fragmentation in vivo.
Anderson
P E
PE
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095, USA.
Matsunaga
J
J
Simons
E L
EL
Simons
R W
RW
D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D017124:Conserved Sequence; D004269:DNA, Bacterial / Q000737:chemistry; D004722:Endoribonucleases / Q000235:genetics*; D029968:Escherichia coli Proteins; D020558:GTP Phosphohydrolases / Q000096:biosynthesis / Q000235:genetics*; D019204:GTP-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides; D009876:Operon; D010957:Plasmids; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D043244:Ribonuclease III; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D009838:Oligodeoxyribonucleotides; D016601:RNA-Binding Proteins; C081006:RecO protein, E coli; D011993:Recombinant Fusion Proteins; C068027:era protein, E coli; D004722:Endoribonucleases; D043244:Ribonuclease III; C468366:ribonuclease III, E coli; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins