title: Feedback regulation of rRNA and tRNA synthesis and accumulation of free ribosomes after conditional expression of rRNA genes.
abstract: We have constructed a conditional rRNA gene expression system by fusing a plasmid-encoded rrnB operon to the lambda PL promoter/operator. It was thereby possible to study the events that lead to the regulation of chromosomal rRNA and tRNA synthesis after overproduction of rRNA. rRNA induction resulted in a 2-fold increase in 30S and 50S free ribosomal subunits, whereas the polysome fraction was unaffected. Overproduction of rRNA and "free" ribosomes produced a large repression of rRNA and tRNA synthesis from chromosomal genes and a smaller increase in the concentration of guanosine tetraphosphate. These results lend support to the ribosome feedback regulation model: rRNA and tRNA operons are negatively regulated, either directly or through some intermediate, by free, nontranslating ribosomes.
authors.forename: R L
authors.initials: RL
authors.lastname: Gourse
authors.forename: Y
authors.initials: Y
authors.lastname: Takebe
authors.forename: R A
authors.initials: RA
authors.lastname: Sharrock
authors.forename: M
authors.initials: M
authors.lastname: Nomura
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005246:Feedback; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D006159:Guanosine Tetraphosphate / Q000378:metabolism; D009876:Operon; D010957:Plasmids; D012335:RNA, Ribosomal / Q000096:biosynthesis / Q000235:genetics*; D012343:RNA, Transfer / Q000096:biosynthesis*; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D012335:RNA, Ribosomal; D006159:Guanosine Tetraphosphate; D012343:RNA, Transfer