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Global repositioning of transcription start sites in a plant-fermenting bacterium.

Nature communications (2016-12-17)
Magali Boutard, Laurence Ettwiller, Tristan Cerisy, Adriana Alberti, Karine Labadie, Marcel Salanoubat, Ira Schildkraut, Andrew C Tolonen
ABSTRACT

Bacteria respond to their environment by regulating mRNA synthesis, often by altering the genomic sites at which RNA polymerase initiates transcription. Here, we investigate genome-wide changes in transcription start site (TSS) usage by Clostridium phytofermentans, a model bacterium for fermentation of lignocellulosic biomass. We quantify expression of nearly 10,000 TSS at single base resolution by Capp-Switch sequencing, which combines capture of synthetically capped 5' mRNA fragments with template-switching reverse transcription. We find the locations and expression levels of TSS for hundreds of genes change during metabolism of different plant substrates. We show that TSS reveals riboswitches, non-coding RNA and novel transcription units. We identify sequence motifs associated with carbon source-specific TSS and use them for regulon discovery, implicating a LacI/GalR protein in control of pectin metabolism. We discuss how the high resolution and specificity of Capp-Switch enables study of condition-specific changes in transcription initiation in bacteria.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
D-(+)-Xylose, BioXtra, ≥99%
Supelco
Avicel® PH-101, ~50 μm particle size
Roche
5′/3′ RACE Kit, 2nd Generation, sufficient for 10 reactions