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Functional importance of the Escherichia coli ribosomal RNA leader box A sequence for post‐transcriptional events
Author(s) -
Theißen G.,
Behrens S. E.,
Wagner R.
Publication year - 1990
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1990.tb00544.x
Subject(s) - biology , ribosomal rna , antitermination , operon , 23s ribosomal rna , ribosome , 50s , 5s ribosomal rna , genetics , rna , microbiology and biotechnology , escherichia coli , gene
Summary To shed more light on the controversial findings concerning the functional participation of the highly conserved nut ‐like leader box A sequence element in ribosomal RNA transcription antitermination we have carried out a mutational study. We have substituted the box A and combined this mutation with several deletions comprising the rRNA leader elements box B, box C and the t L region. The mutations are located within the genuine rrnB operon cloned on multicopy plasmids. We determined the effects of the mutations on cell growth, rRNA accumulation and ribosomal subunit stoichiometry. Cells transformed with the mutated plasmids were affected in their growth rate, and showed a surprising deficiency of the promoter‐proximal 16S compared to the 23S RNA, indicative of a post‐transcriptional degradation event. Accordingly, we could demonstrate a reduced amount of free 305 relative to 50S ribosomal subunits in exponentially growing cells. Similar stoichiometric aberrations in the ribosome pool were detected in conditionally Nus factor‐defective strains. The results show that the leader box A sequence within rRNA operons has important post‐transcriptional functions for 16S RNA stability and ribosomal subunit stoichiometry. A model is proposed, describing the biogenesis and quality control of ribosomes based on rRNA leader and Nus‐factor interactions. It is compatible with the previously observed effects of box A in antitermination.