E. coli bacteria express the rpoS gene when subject to stress. RpoS is responsible for activating hundreds of genes which make E. coli dormant and capable of surviving harsh conditions. This gene is post-transcriptionally regulated by several small noncoding RNAs (sRNAs). An overexpression screen was carried out to identify novel regulators of rpoS. It was discovered a region between the GlnS gene and the ChiP genes that down-regulated rpoS when overexpressed as measured by Western blot and RpoS’-‘LacZ fusions. Data from additional reporter fusions (a short rpoS’-‘LacZ translation fusion and an rpoS -LacZ+ operon fusion) indicated that this region decreased rpoS translation but not transcription. Sequence analysis and data from previously published RNA-seq studies suggested that there are two potentially interesting sequences in this region. One is a transcript that is expressed independently of any other gene; we have named this transcript TsiR (Translational Inhibitor of rpoS). The other one contains the 5’ UTR (Untranslated Region) of the ChiP gene which is known to bind to the sRNA ChiX, potentially titrating the sRNA chaperone Hfq through this interaction. Current work is aimed at determining which part of the sequence (TsiR or the 5’ UTR of ChiP) is responsible for downregulating rpoS levels. More Western blots and Betagalactosidase assays will be carried out to determine the rpoS levels in different E. coli strains including ChiX-deletion E. coli strains.

Determining which part of the region between the GlnS and ChiP genes downregulates rpoS in Escherichia coli, TsiR or the 5’ UTR of ChiP

253rd National Meeting (2017)

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