Isolation and characterization of the 5′-upstream and untranslated regions of the mouse type II iodothyronine deiodinase gene

The type II iodothyronine deiodinase (D2) catalyzes the 5'-deiodinationc of thyroxine to yield the biologically active form, 3,3',5,-tri-iodothyronine, and is a member of the selenoproteins. We isolated a 17.5 kb mouse genomic clone containing the entire coding and 5'-untranslated regions of the D2 gene (mdio2). We also isolated the entire 5'-UTR of the mouse D2 cDNA, which was 753 bp in length and contained five ATG codons. An additional 258 bp ORF from the fourth ATG codon was found in the same reading frame as the coding region reported previously, and this additional ORF contained a TGA codon, which could encode selenocysteine. The proximal promoter of mdio2 contained a TATA box and several potential transcription factor-binding sequences, including CRE, C/EBP and GATA binding sites. The 1.3 kb 5'-upstream region exhibited a promoter activity by reporter assay using Mm5MT and JAR cells, which have a D2 transcript, but not HepG2 cells that have no detectable level of D2 transcript. Published by Elsevier Science Ireland Ltd.