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 chro mosome 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 bl ot analysis has shown that ISOT-3 is highly expressed in ovary and tes tes; with low-level expression in six other tissues tested. In contras t, ISOT-1 is expressed at high levels in the brain, and there is no de tectable expression in ovary. The exonic organization of these two gen es is highly conserved with only one variant intron position. Intron 1 5 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 con served 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 h ave descended from a common ancestor. In addition, the low overall seq uence identity and different expression patterns may reflect differenc es in substrate specificity. (C) 1998 Elsevier Science B.V. Al rights reserved.