Molecular cloning and characterization of the mouse and human TUSP gene, anovel member of the tubby superfamily

We report here the cloning and characterization of a novel gene belonging t o the tubby superfamily proteins (TUSP) in mouse and human. The mouse Tusp cDNA is 9120 bp in length and encodes a deduced protein of 1547 amino acids , while the human TUSP gene is 11,127 bp and encodes a deduced protein of 1 544 amino acids. The human and mouse genes are 87% identical for their nucl eotide sequences and 85% identical for their amino acid sequences. The prot ein sequences of these genes are 40-48% identical to other tubby family pro teins at the C-terminal conserved 'tubby domain'. In addition, the TUSP pro teins contain a tubby signature motif (FXGRVTQ), two bipartite nuclear loca lization signals (NLSs) at the C-terminal, two proline-rich regions, one WD 40 repeat region and one suppressor of cytokines signaling domain. Transfec tion assay with green fluorescent protein-tagged TUSP expression constructs showed that the complete TUSP protein and the N-terminal portion of TUSP a re localized in the cytoplasm but the C-terminal portion with the two NLSs produced distinct dots or spots localized in the cytoplasm. Northern blotti ng analysis showed that the major transcript with the complete coding seque nce is expressed mainly in the brain, skeletal muscle, testis and kidney. R adiation hybrid mapping localized the mouse gene to chromosome 17q13 and th e human TUSP gene to chromosome 6q25-q26 near the type I diabetes gene IDDM 5. However, association analysis in diabetic families with a polymorphic mi crosatellite marker did not show any evidence for association between TUSP and type I diabetes, The precise biological function of the tubby superfami ly genes is still unknown; the highly conserved tubby domain in different s pecies, however, suggests that these proteins must have fundamental biologi cal functions in a wide range of multi-cellular organisms. (C) 2001 Elsevie r Science B.V. All rights reserved.