An iron enhancer element in the FTN-1 gene directs iron-dependent expression in Caenorhabditis elegans intestine.
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 and ftn-2 expression, we generated transcriptional GFP reporters corresponding to 5 '-upstream sequences of the ftn-1 and ftn-2 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-directed 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 and ftn-2 transcription by iron requires ELT-2 and that the IDE functions as an iron-dependent enhancer in intestine.
Romney
S Joshua
SJ
Eccles Program in Human Molecular Biology and Genetics, University of Utah, Salt Lake City 84112, USA.
Thacker
Colin
C
Leibold
Elizabeth A
EA
D000818:Animals; D001483:Base Sequence; D002107:Caenorhabditis / Q000235:genetics; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000254:growth & development; D017124:Conserved Sequence; D004068:Digestive System Physiological Phenomena; D004742:Enhancer Elements, Genetic; D005293:Ferritins / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter; D005838:Genotype; D007422:Intestines / Q000502:physiology*; D007501:Iron / Q000494:pharmacology*; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics
D020033:Protein Isoforms; D012333:RNA, Messenger; D005293:Ferritins; D007501:Iron