The mammalian RPS6 gene, homolog of the Drosophila air8 tumor suppressor gene: is it an oncosuppressor gene?

The mammalian gene encoding the S6 ribosomal protein is the homolog of the Drosophila air8 tumor suppressor gene. We assigned the rat Rps6 gene to chromosome 5q22-33. The rat 5q22-33 chromosome region, previously shown to bear a malignant transformation suppressor gene, is homologous to the human 9p2l region, frequently deleted in various kinds of cancers and also containing at least one tumor suppressor (oncosuppressor) gene. To test the possibility that the Rps6 gene could be an oncosuppressor gene in mammals, we analysed its sequence and expression in normal and malignantly transformed cells. In mouse hepatoma cells (BWTG3), the Rps6 gene is hemizygously deleted but the remaining copy shows no sequence anomaly in the coding region, indicating that Rps6 is not oncosuppressor and that another gene acting as an oncosuppressor is located in its vicinity. In human tumor cells, the RPS6 gene is retained in cells showing deletion of the near-by gene, IFNB. Our results do not support the possibility that the RPS6 gene acts as an oncosuppressor gene in mammalian cells.