Sigma(I) from Bacillus subtilis: Impact on Gene Expression and Characterization of sigma(I)-Dependent Transcription That Requires New Types of Promoters with Extended-35 and-10 Elements
Abstract
The I sigma factor from Bacillus subtilis is a factor associated with RNA polymerase (RNAP) that was previously implicated in adaptation of the cell to elevated temperature. Here, we provide a comprehensive characterization of this transcriptional regulator.
By transcriptome sequencing (RNA-seq) of wild-type (wt) and I-null strains at 37°C and 52°C, we identified 130 genes affected by the absence of I. Further analysis revealed that the majority of these genes were affected indirectly by I.
The I regulon, i.e., the genes directly regulated by I, consists of 16 genes, of which eight (the dhb and yku operons) are involved in iron metabolism. The involvement of I in iron metabolism was confirmed phenotypically.
Next, we set up an in vitro transcription system and defined and experimentally validated the promoter sequence logo that, in addition to 35 and 10 regions, also contains extended 35 and 10 motifs. Thus, I-dependent promoters are relatively information rich in comparison with most other promoters.
In summary, this study supplies information about the least-explored factor from the industrially important model organism B. subtilis.