Fig. 3.

Features associated with the Dio3 gene. The major fetal and placental isoform of Dio3 is transcribed from a single 2.1 kb exon with a long 3′UTR (gray) containing the SECIS sequence (purple). The sequence containing the coding region of the gene and the 3′UTR is highly conserved in vertebrates (red boxes). Other transcripts have been described in the brain that may arise from alternative promoters (?), but have not yet been mapped. Dio3os is transcribed in the opposite direction to Dio3, and gives rise to at least 5 alternatively spliced transcripts. The 5′ end of these reported transcripts all originate within the same CpG island as the Dio3 promoter (green box). Exon 1 of Dio3os contains a conserved microRNA, mir1247 (orange box). Approximately 5 kb telomeric to the Dio3 promoter there is a conserved enhancer that can drive Dio3 and Dio3os expression in vitro (blue box). In ES cells the Dio3 promoter is decorated with modified histones, H3K27me3 (red bar) and H3K4me3 (blue bar), indicative of a ‘poised’ chromatin state.