TP53 gene, encoding tumor protein P53, is frequently inactivated in various types of human cancer, including colorectal, lung, and gastric cancer. Cancer cells with TP53 mutation acquire malignant potentials, such as selective growth advantage, genomic instability, resistance to apoptosis, and promotion of angiogenesis. U33271 partial cDNA isolated from HPV-18 E6/E7 immortalized keratinocytes is derived from one of P53-traget genes. Here, we identified and characterized the TP53I5 (tumor protein P53 inducible protein 5) gene corresponding to U33271 partial cDNA by using bioinformatics. FLJ23270 (AK026923.1) was the representative human TP53I5 cDNA. TP53I5 gene, consisting of 23 exons, was located at human chromosome 11p15.5. TP53I5 mRNA was expressed in human colorectal, lung, and breast cancer. IMAGE5352905 (BC025477.1) and IMAGE6508837 (NM_178381.2) were aberrant mouse Tp53i5 cDNAs with multiple frameshifts due to retention of intronic sequences. Complete coding sequence of mouse Tp53i5 cDNA was determined by assembling nucleotide positions 1-1213, 1293-1740, 1745-2045, and 2071-3088 of BC025477.1. Tp53i5 gene was located at mouse chromosome 7F5. Human TP53I5 (782 aa) and mouse Tp53i5 (747 aa), showing 71.1% total-amino-acid identity, were eight-transmembrane proteins with N- and C-terminal tails facing the cytoplasm. TP53I5 orthologs were homologous to TMEM16A (FLJ10261 or ORAOV2), TMEM16B, TMEM16C, TMEM16D, TMEM16E and TMEM16F with the TM16H1, TM16H2, and TM16H3 domains. TP53I5 was identified as a novel member of the TMEM16 family based on membrane topology and TM16H1-3 domains. This is the first report on the human TP53I5 and mouse Tp53i5 genes.

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