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

Abstract

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.Key words: SART3 -Tumor-rejection antigen -RNA-binding protein -HLA-A2402 -Cytotoxic T lymphocytesOne of the most significant advances in the field of tumor immunology has been the recent identification of genes encoding tumor-rejection antigens that are recognized by HLA-class-I-restricted and tumor-specific cytotoxic T lymphocytes (CTLs).1, 2) The potential application of these findings to the development of cancer vaccines has brought nearer the prospect of specific cancer immunotherapy. Indeed, several peptides encoded by these genes are now under clinical trial as cancer vaccines, and major tumor regression has been observed in some melanoma patients.3, 4) We have recently isolated a human SART3 (hSART3) gene encoding a tumor-rejection antigen from cDNA of a human esophageal cancer cell line. 5) Two SART3-derived peptides, at positions 109-118 and 315-323, that are recognized by HLA-A2402-restricted CTLs, are able to induce HLA-A2402-restricted and tumorspecific CTLs from peripheral blood mononuclear cells (PBMCs) of HLA-A24 positive (HLA-A24 + ) cancer patients. hSART3 encodes a Mr 140 000 protein expressed in both the cytosol of the majority of proliferating cells, including non-tumorous cell lines, and the nucleus of the majority of cancer cells. However, the SART3 protein was undetectable in normal tissues except for the testis and fetal liver, regardless of its ubiquitous expression at the mRNA level.5) There are several motifs in the sequence of the SART3 protein: nuclear localization signals 6) around positions 612-615 and 641-647, a ribonucleoprotein-1 (RNP-1) motif, 7) one of the well-characterized RNA-binding motifs, at positions 746-753 and 841-848, and a tyrosine phosphorylation motif 8) at positions 309-316. The involvement of the SART3 ...

Antitumor effects of systemic and local immunization with a CTL-directed peptide in combination with a local injection of OK-432.

“…We previously identified a mouse homologue of the human SART3 (22). Interestingly, human HLA-A2404 and mouse H-2K d molecules have similar anchor motifs (23,24), and the human SART3 315-323 peptide, which has the potential to induce HLA-A24 -restricted CTLs (21), has the same amino acid sequence as the mouse SART3 (22).…”

“…Interestingly, human HLA-A2404 and mouse H-2K d molecules have similar anchor motifs (23,24), and the human SART3 315-323 peptide, which has the potential to induce HLA-A24 -restricted CTLs (21), has the same amino acid sequence as the mouse SART3 (22). These findings suggest that the human SART3 315-323 peptide could be used to examine the in vivo antitumor effects of peptide vaccine and their mechanisms in H-2 d mice.…”

“…In this study, we attempted to establish a new protocol based on this concept. Because of previous reports suggesting that H-2K d and HLA-A24 molecules have similar binding motifs (23, 24), we used a syngeneic system, BALB/c mice and colon26 carcinoma cells, and the human SART3 315-323 peptide, which has the same amino acid sequence as the mouse SART3 (22). In this study, we confirmed that colon26 cells were positive for SART3 mRNA, and SART3 315-323 peptide -specific CTLs were able to recognize colon26 cells.…”

“…We have identified a 9-mer peptide, SART3 [315][316][317][318][319][320][321][322][323] , that has the potential to induce human leukocyte antigen (HLA)-A24-restricted and tumor-reactive CTLs in HLA-A24 + cancer patients (21). In addition, we identified a mouse homologue, mouse SART3, which has 80% and 86% homology to the human SART3 at the nucleotide and protein levels, respectively (22). Interestingly, human HLA-A2404 and mouse H-2K d molecules have similar anchor motifs (23,24), and the human SART3 [315][316][317][318][319][320][321][322][323] peptide has the same amino acid sequence as the ''mouse'' SART3 316-324 peptide (22).…”

“…In addition, we identified a mouse homologue, mouse SART3, which has 80% and 86% homology to the human SART3 at the nucleotide and protein levels, respectively (22). Interestingly, human HLA-A2404 and mouse H-2K d molecules have similar anchor motifs (23,24), and the human SART3 [315][316][317][318][319][320][321][322][323] peptide has the same amino acid sequence as the ''mouse'' SART3 316-324 peptide (22). These lines of evidence indicate that the human SART3 315-323 peptide could be used in order to examine the in vivo antitumor effects of peptide vaccine and the associated mechanisms of action in H-2 d mice.…”