Sequence Analysis of Genes Encoding Rodent Homologues of the Human Tumor‐rejection Antigen SART‐1

Human SART‐1 (hSART‐1) gene encodes a 125 kD protein with a leucine‐zipper motif expressed in the nucleus of all proliferating cells, and a 43 kD protein expressed in the cytosol of most epithelial cancers. In this study, two rodent genes (rSART‐1 and mSART‐1) homologous to hSART‐1 were cloned from cDNA libraries of murine brain and a rat tumor cell line, respectively. mSART‐1 and rSART‐1 were highly homologous to hSART‐1 with 86% and 84% identity at the nucleotide level, and 95% and 91% at the protein level, respectively. The leucine zipper domain and two basic amino acid portions that bind DNA, as well as peptide sequences recognized by human cyto‐toxic T lymphocytes (CTLs), were all conserved in these rodent genes. Nuclear protein homologous to the 125 kD hSART‐1(800) protein, but not to the 43 kD cytosol SART‐1(259) protein, was detectable with specific antibody in the nuclear fractions of rodent tumor cell lines, and normal rodent fetal liver and testis. These rodent genes should be a novel tool for studies on the biological roles of the SART‐1 gene, and also in the construction of animal models of specific immuno‐therapy using SART‐1 gene products.