Differential control of Bradyrhizobium japonicum iron stimulon genes through variable affinity of the iron response regulator (Irr) for target gene promoters and selective loss of activator function.

ABSTRACT: Bradyrhizobium japonicum Irr is a conditionally stable transcriptional activator and repressor that accumulates in cells under iron-limited, manganese-replete conditions, but degrades in a haem-dependent manner under high iron conditions, manganese limitation or upon exposure to H2 O2 . Here, we identified Irr-regulated genes that were relatively unresponsive to factors that promote Irr degradation. The promoters of those genes bound Irr with at least 200-fold greater affinity than promoters of the responsive genes, resulting in maintenance of promoter occupancy over a wide cellular Irr concentration range. For Irr-repressible genes, promoter occupancy correlated with transcriptional repression, resulting in differential levels of expression based on Irr affinity for target promoters. Howe

SUBMITTER: Jaggavarapu S 

PROVIDER: S-EPMC4040977 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature