Ubiquitin Specific Peptidase 13 (USP13)

Isopeptidase T (ISOT) is a deubiquitinating enzyme and a member of the family of ubiquitin-binding proteins (UBPs). UBPs contain a catalytic core of approximately 300 amino acids located between conserved cysteine and histidine boxes.

The predicted ISOT3 protein contains the conserved UBP catalytic sites and is 55% identical to ISOT. Northern blot analysis revealed that ISOT3 was expressed as 8.5-, 5.5-, and 3.5-kb mRNAs in all tissues tested, with the highest levels of expression observed in testis and ovary. The ISOT3 gene contains 20 exons and spans at least 90 kb. Since the exonic organization of ISOT and ISOT3 is highly conserved, with only 1 variant intron, the authors suggested that these 2 genes descended from a common ancestor.