Three putative binding sites, O-I, O-II, and O-III, were identified in previous studies. Primer extension analysis was performed to measure the effects of deletion mutagenesis on O-I, O-III, and O-I/O-III double mutants. O-II overlaps the -10 region of the promoter and so was not a subject for mutagenesis. DNAse I protection was also performed on each site in iron-variable media, and suspicions that O-I acts as an UP element where supported by footprinting with RNAP. Results indicate the spacing between O-II and O-III is key to derepression under iron limitation, and that O-III is involved in derepression in low-iron while O-II binding in high-iron is speculated to result in repression. O-I was bound in both high-iron and low-iron (when O-II and O-III were bound, respectively).
Regulated genes for each binding site are displayed below. Gene regulation diagrams show binding sites, positively-regulated genes, negatively-regulated genes, both positively and negatively regulated genes, genes with unspecified type of regulation. For each indvidual site, experimental techniques used to determine the site are also given.
| Site sequence | Regulated genes | Gene diagram | Experimental techniques | TF function | TF type |
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