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Aliases DIO2, 5DII, D2, DIOII, SelY, TXDI2, deiodinase, iodothyronine, type II
External IDs MGI: 1338833 HomoloGene: 621 GeneCards: DIO2
Species Human Mouse
RefSeq (mRNA)


RefSeq (protein)


Location (UCSC) Chr 14: 80.2 – 80.39 Mb Chr 12: 90.72 – 90.74 Mb
PubMed search [1] [2]
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Type II iodothyronine deiodinase (iodothyronine 5'-deiodinase, iodothyronine 5'-monodeiodinase) is an enzyme that in humans is encoded by the DIO2 gene.[3][4][5]


The protein encoded by this gene belongs to the iodothyronine deiodinase family. It activates thyroid hormone by converting the prohormone thyroxine (T4) by outer ring deiodination (ORD) to bioactive 3,3',5-triiodothyronine (T3). It is highly expressed in the thyroid, and may contribute significantly to the relative increase in thyroidal T3 production in patients with Graves' disease and thyroid adenomas. This protein contains selenocysteine (Sec) residues encoded by the UGA codon, which normally signals translation termination. The 3' UTR of Sec-containing genes have a common stem-loop structure, the Sec insertion sequence (SECIS), which is necessary for the recognition of UGA as a Sec codon rather than as a stop signal. Alternative splicing results in multiple transcript variants encoding different isoforms.[5]


DIO2 has been shown to interact with USP33.[6]

See also[edit]


  1. ^ "Human PubMed Reference:". 
  2. ^ "Mouse PubMed Reference:". 
  3. ^ Croteau W, Davey JC, Galton VA, St Germain DL (Sep 1996). "Cloning of the mammalian type II iodothyronine deiodinase. A selenoprotein differentially expressed and regulated in human and rat brain and other tissues". J Clin Invest. 98 (2): 405–417. doi:10.1172/JCI118806. PMC 507444Freely accessible. PMID 8755651. 
  4. ^ Araki O, Murakami M, Morimura T, Kamiya Y, Hosoi Y, Kato Y, Mori M (Jun 1999). "Assignment of type II iodothyronine deiodinase gene (DIO2) to human chromosome band 14q24.2→q24.3 by in situ hybridization". Cytogenet Cell Genet. 84 (1–2): 73–74. doi:10.1159/000015218. PMID 10343107. 
  5. ^ a b "Entrez Gene: DIO2 deiodinase, iodothyronine, type II". 
  6. ^ Curcio-Morelli C, Zavacki AM, Christofollete M, Gereben B, de Freitas BC, Harney JW, Li Z, Wu G, Bianco AC (July 2003). "Deubiquitination of type 2 iodothyronine deiodinase by von Hippel-Lindau protein-interacting deubiquitinating enzymes regulates thyroid hormone activation". J. Clin. Invest. 112 (2): 189–96. doi:10.1172/JCI18348. PMC 164294Freely accessible. PMID 12865408. 

Further reading[edit]