The positioning of bacterial genes within the cell had previously been proposed to depend on the function of the proteins that they encode — for example, genes encoding membrane proteins would be positioned close to the membrane. This study tests this hypothesis in Escherichia coli, examining the dynamics of two loci carrying genes encoding membrane proteins. The authors found that both the lac (lactose metabolism) locus and an inducible locus carrying the tetracycline efflux pump TetA fused to mCherry (tetA–mCherry) shifted towards the membrane following induction. This relocalization was rapid, occurring within 1–3 minutes of induction for tetA–mCherry, and required ongoing transcription and translation. Moreover, the authors detected repositioning of loci that were 90 kb away from tetA–mCherry, indicating that large regions of the genome relocalize during gene expression. It is therefore likely that membrane protein expression has an integral role in determining the conformation of the bacterial chromosome.
ORIGINAL RESEARCH PAPER
Libby, E. A. et al. Membrane protein expression triggers chromosomal locus repositioning in bacteria. Proc. Natl Acad. Sci. USA 23 Apr 2012 (doi:10.1073/pnas.1109479109)