The Bacterial Transcription Termination Factor Rho Coordinates Mg(2+) Homeostasis with Translational Signals

J Mol Biol. 2015 Dec 4;427(24):3834-49. doi: 10.1016/j.jmb.2015.10.020. Epub 2015 Oct 30.


The bacterial protein Rho triggers transcription termination at the ends of many operons and when transcription and translation become uncoupled. In addition to these genome wide activities, Rho implements regulation of specific genes by dictating whether RNA polymerase terminates transcription within the 5' leader region or continues into the downstream coding region. Here, we report that the Mg(2+) channel gene corA in Salmonella enterica serovar Typhimurium, which was previously thought to be constitutively expressed, is regulated by a Rho-dependent terminator located within its 5' leader region. We demonstrate that the unusually long and highly conserved corA leader mRNA can adopt two mutually exclusive conformations that determine whether or not Rho interacts with a Rho utilization site on the nascent RNA and thereby prevents transcription of the corA coding region. The RNA conformation that promotes Rho-dependent termination is favored by efficient translation of corL, a short open reading frame located within the corA leader. Thus, corA transcription is inversely coupled to corL translation. This mechanism resembles those governing expression of Salmonella's other two Mg(2+) transport genes, suggesting that Rho links Mg(2+) uptake to translational signals.

Keywords: RNA secondary structure; Rho utilization (rut) site; Salmonella; gene regulation; short open reading frame (ORF).

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Untranslated Regions*
  • Amino Acid Sequence
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Gene Expression Regulation, Bacterial*
  • Homeostasis
  • Inverted Repeat Sequences
  • Magnesium / metabolism*
  • Molecular Sequence Data
  • Nucleic Acid Conformation
  • Protein Biosynthesis
  • Rho Factor / physiology*
  • Salmonella typhimurium / genetics
  • Salmonella typhimurium / metabolism*
  • Transcription Initiation Site


  • 5' Untranslated Regions
  • Bacterial Proteins
  • Cation Transport Proteins
  • CorA protein, Salmonella
  • Rho Factor
  • Magnesium