Ferritin is a ubiquitous protein that sequesters iron and protects cells from iron toxicity. Caenorhabditis elegans express two ferritins, FTN-1 and FTN-2, which are transcriptionally regulated by iron. To identify the cis-acting sequences and proteins required for iron-dependent regulation of ftn-1
expression, we generated transcriptional GFP reporters corresponding to 5'' upstream sequences of the ftn-1
genes. We identified a conserved 63-bp sequence, the ''iron-dependent element'' (''IDE''), that is required for iron-dependent regulation of a ftn-1
GFP reporter in intestine. The IDE contains two GATA-binding motifs and three octameric direct repeats. Site-specific mutagenesis of the GATA sequences, singly or in combination, reduces ftn-1
GFP reporter expression in the intestine. In vitro DNA mobility shift assays show that the intestine-specific GATA protein ELT-2 binds to both GATA sequences. Inhibition of ELT-2 function by RNA interference blocks ftn-1
GFP reporter expression in vivo. Insertion of the IDE into the promoter region of a heterologous reporter activates iron-dependent transcription in intestine. These data demonstrate that the activation of ftn-1
transcription by iron requires ELT-2, and that the IDE functions as an iron-dependent enhancer in intestine.