The Cpx envelope stress response of Escherichia coli regulates and is regulated by the small RNA RprA

• Author / Creator

  Evans, Alexander D

• When bacteria sense changes in their environment, they adapt by altering the expression of their genes in such a way that accommodates the change. To do this, bacterial cells can modulate the activity of their genes at either the level of transcription, or at the post-transcriptional level. Post-transcriptional gene regulation generally involves either a non-coding regulatory RNA element in the transcript of the gene being regulated (i.e. riboswitch), or a small regulatory RNA molecule. The latter type, small regulatory RNAs (sRNAs) have in recent years been shown to be involved in regulating a number of cellular processes (such as iron metabolism, motility, outer membrane porin biogenesis), and be expressed in response to a variety of environmental signals. One such environmental signal is the misfolding of envelope localized proteins, also known as envelope stress, which is detected by the Cpx two-component signal transduction system in the bacterium Escherichia coli. The Cpx envelope stress response consists of the inner membrane bound signal kinase CpxA, its periplasmic inhibitor CpxP, and the response regulator CpxR which acts as a transcription factor when activated. A recent microarray done by our group has suggested that induction of the Cpx envelope stress response leads to the altered expression of the sRNA genes rprA and cyaR which may help alleviate the stress through the regulation of their known targets, many of which encode envelope-localized structures. Here we confirm Cpx regulation of these two genes by showing that Cpx induction modulates activity of transcriptional reporter genes made with promoters of these genes. We also show that overexpression of one of these genes, rprA, promotes the Cpx-related phenotype of amikacin resistance and reduced motility. Furthermore, we show that overexpression of rprA causes repression of the Cpx response, forming a negative feedback loop which likely acts indirectly on response regulator of the Cpx response, CpxR. This inhibition was found not to involve direct translational repression of cpxR but might involve modulation of its activity, which recent experiments have suggested may involve the glutamate-dependent acid stress resistance system (GDAR).

• Subjects / Keywords

  • SRNA
  • Signal transduction
  • Envelope stress
  • Escherichia coli

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R37M04542

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.