The genomic organization of Isopeptidase T-3 (ISOT-3), a new member of the ubiquitin specific protease family (UBP)

A novel Isopeptidase T gene (ISOT-3) has been identified on human chromosome 3q26.2-q26.3. This gene shows 67.3% nucleotide identity and 54.8% amino acid identity to human Isopeptidase T-I (ISOT-1). Northern blot analysis has shown that ISOT-3 is highly expressed in ovary and testes; with low-level expression in six other tissues tested. In contrast, ISOT-1 is expressed at high levels in the brain, and there is no detectable expression in ovary. The exonic organization of these two genes is highly conserved with only one variant intron position. Intron 15 in ISOT-3 is absent in ISOT-1, but there is an alternate splice site at the same location. Although the exon-intron structure has been conserved between the two genes, ISOT-3 has significantly larger intronic regions, and the overall size of this gene is at least 90 kb compared to 15 kb for ISOT-1. These data suggest that both ISOT-1 and ISOT-3 have descended from a common ancestor. In addition, the low overall sequence identity and different expression patterns may reflect differences in substrate specificity. (C) 1998 Elsevier Science B.V. Al rights reserved.