Expression of a human tumour-derived p53 His 273 cDNA induced growth arrest in fission yeast Schizosaccharomyces pombe. Based on the p53-induced growth arrest, we cloned an extragenic suppressor, termed tms1, by complementation. The open reading frame of the tms1 gene corresponded to a protein of 347 amino acids with a calculated mass of 37380 Da. The transcriptional start site of the tms1 gene was mapped and, in addition, the corresponding cDNA was isolated and expressed in Escherichia coli. Recombinant tms1 protein served as an antigen to produce specific polyclonal antibodies to aid identification of the tms1-gene-product in total yeast lysates. Comparison of the deduced amino acid sequence of tms1 with available databases revealed significant similarity to dehydrogenases, suggesting that the tms1 protein itself might possess dehydrogenase activity.