Inhibitory effect of high-level transcription of the bacteriophage lambda nutL region on transcription of rRNA in Escherichia coli

Abstract

Transcription of the bacteriophage X nutL region from the pL promoter on a multicopy plasmid in Escherichia coli causes a reduction in growth rate and in transcription of rRNA relative both to total transcription and to transcription of tRNAs that are not encoded in rRNA operons. These observations support the hypothesis, previously based on nut site DNA sequence homology, that the phage X and rRNA antitermination systems are related.

Control of rRNA transcription in Escherichia coli.

“…The sequence requirements for rrn antitermination suggest that this system may share some of the factors required for lambda antitermination. Consistent with this idea, overproduction of the lambda nutL sequence inhibits rRNA production in vivo (293), presumably by titrating out some of the factors required for rrn antitermination. The first demonstration that some of the Nus factors might specifically be required for rrn antitermination also came from an experiment by Sharrock et al (292), which showed that premature termination occurred within rrn operons in nusB5 mutants and a cold-sensitive nusA mutant.…”

SuhB Associates with Nus Factors To Facilitate 30S Ribosome Biogenesis in Escherichia coli

“…Two lines of evidence support our observation that the function of Nus factors at rRNA is not antitermination. First, although early studies reported an increase in 16S relative to 23S rRNA in strains with mutant or titrated Nus factors ( 23 , 24 ), the probe used to detect 16S rRNA was found to hybridize to a sequence beginning >1,000 nt downstream of BoxA. This is inconsistent with antitermination by Nus factors, since Rho would be expected to terminate transcription much further upstream ( 55 ).…”

“…Second, nusB and nusA mutants exhibit polarity within the rRNA, having a significantly higher 16S:23S rRNA ratio (30S:50S) than wild-type cells ( 22 , 23 ). Third, high-level transcription of RNA containing λ NutL titrates Nus factors, thereby decreasing rRNA expression and increasing the 16S:23S rRNA ratio ( 24 ). Fourth, mutation of boxA results in a significant reduction in rRNA synthesis from an rRNA operon carried on a plasmid ( 25 , 26 ).…”

Specific Binding of Escherichia coli Ribosomal Protein S1 to boxA Transcriptional Antiterminator RNA

“…Moreover, rrn boxA RNA has been shown to bind a heterodimer of NusB and S10 (14,20). NusB was further implicated in rrn antitermination by experiments showing that NusB is important for rRNA synthesis in vivo (23) and that a NusB-depleted extract is unable to support antitermination in vitro (25). However, antitermination in the rrn operons is known to differ from N-mediated antitermination in three major ways: first, the bacteriophage N protein is not involved in rrn antitermination; second, rrn boxA is capable of supporting antitermination in the absence of boxB or any other RNA sequence (2); third, an unidentified factor(s) is required for antitermination in vitro in the rrn system but not in the system (25).…”