Recently we reported the isolation of tms1, an extragenic multicopy suppressor of a human p53 His273 tumour mutant-induced growth arrest in fission yeast (Wagner et al: Eur J Biochem 217: 731-736, 1993). tms1 encodes a putative dehydrogenase. We demonstrate direct interaction of p53 with the tms1 protein in vivo. Using p53-specific or tms1-specific polyclonal antibodies, coprecipitation of p53 His273 or p53 wild type with tms1 protein could be shown with extracts from transformed yeast cells. Recombinant purified C-terminal peptide of p53 and tms1 protein were used to demonstrate specific complex formation and to map the interaction to the C-terminus of p53 in vitro by west-Western blot and HPLC analysis.