Abstract
The DpsA protein plays a dual role in Streptomyces coelicolor, both as part of the stress response and contributing to nucleoid condensation during sporulation. Promoter mapping experiments indicated that dpsA is transcribed from a single, sigB-like dependent promoter. Expression studies implicate SigH and SigB as the sigma factors responsible for dpsA expression while the contribution of other SigB-like factors is indirect by means of controlling sigH expression. The promoter is massively induced in response to osmotic stress, in part due to its sensitivity to changes in DNA supercoiling. In addition, we determined that WhiB is required for dpsA expression, particularly during development. Gel retardation experiments revealed direct interaction between apoWhiB and the dpsA promoter region, providing the first evidence for a direct WhiB target in S. coelicolor.
Highlights
A common mechanism used by bacteria to selectively modulate gene expression in response to stress involves promoter selection by alternative sigma factors
Our initial studies using both Quantitative Real-Time PCR and immunoblots revealed that dpsA expression is strongly up-regulated in response to osmotic up-shift and high temperature [15]
High resolution S1 protection assay experiments performed using total RNA extracted from S. coelicolor M145 grown in MS agar and MS agar containing 250 mM KCl confirmed that dpsA expression is strongly induced by osmotic stress from a single transcription start point (Figure 1A and C), while transcripts are almost undetectable in the non-stressed sample
Summary
A common mechanism used by bacteria to selectively modulate gene expression in response to stress involves promoter selection by alternative sigma factors. Moisture and temperature are only a few of these challenges, leading to the activation of complex regulatory networks controlling a myriad of genes involved in stress responses and allowing adaptation to the harsh surroundings. The response to stress in Streptomyces coelicolor has been extensively studied and a central role for a SigmaB ortholog has been identified [2]. In contrast with B. subtilis, where various stress conditions induce a single regulon under the control of SigmaB, proteomics studies indicate that in S. coelicolor different regulons are activated in response to specific stresses. This led to the interpretation that independent control mechanisms could govern individual stress responses. Numerous stressinduced proteins are developmentally controlled, suggesting a dual role for regulatory elements involved in both stress responses and development [5]
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