Mouse Homologue of the Human SART3 Gene Encoding Tumor‐rejection Antigen

We recently isolated a human SART3 (hSART3) gene encoding a tumor‐rejection antigen recognized by HLA‐A2402‐restricted cytotoxic T lymphocytes (CTLs). The hSART3 was also found to exist as an RNA‐binding nuclear protein of unknown biological function. In this study, we cloned and analyzed the homologous mouse SART3 (mSART3) gene in order to understand better the function of hSART3, and to aid in establishing animal models of specific immunotherapy. The cloned 3586‐bp cDNA encoded a 962‐amino acid polypeptide with high homology to hSART3 (80% or 86% identity at the nucleotide or protein level, respectively). Nonapeptides recognized by the HLA‐A2402‐restricted CTLs and all of the RNA‐binding motifs were conserved between hSART3 and mSART3. The mSART3 mRNA was ubiquitously expressed in normal tissues, with low level expression in the liver, heart, and skeletal muscle. It was widely expressed in various organs from as early as day 7 of gestation. mSART3 was mapped to chromosome 5, a syntenic region for human chromosome 12q23–24, and its genomic DNA extended over 28‐kb and consisted of 19 exons. This information should be important for studies of the biological functions of the SART3 protein and for the establishment of animal models of specific cancer immunotherapy.