Identification and Analysis of the Transcriptional Regulatory Networks Governing Mechanosensitive Channels in E. coli

Abstract

Mechanosensitive (MS) channels are membrane proteins which are gated by mechanical stress in the cell membrane. Channel opening in response to mechanical stresses makes it possible for molecules to pass through the membrane, allowing an organism to alleviate solute imbalances which place osmotic stress on the membrane and can cause cell lysis and death. Two of the seven known MS channels in E. coli, MscL and MscS, are individually capable of rescuing these bacteria from sudden changes in osmolarity (osmotic shock). If MscL and MscS are both sufficient for ensuring survival under osmotic shock conditions, what is the purpose of the other five MS channels? In the interest of exploring the physiological roles of the various MS channels, we hypothesize that understanding how they are regulated will shed light on their function. Specifically, we investigate the regulatory context of the MS genes by identifying the regulatory architecture and transcription factors responsible for controlling MS gene output. We use a method known as "Sort-Seq" to locate transcription factor binding sites with base pair resolution, and DNA affinity chromatography to determine transcription factor identity. Understanding how the MS genes are regulated will give us clues as to the specific stressors which they defend the cell against. This work provides a specific case study of a method which we think will have much broader reach in mapping out regulatory networks genome-wide.