A new gene (STM1; suppressor of tom1) of Saccharomyces cerevisiae was isolated by the ability to suppress the temperature sensitivity of a tom1 mutant, by increasing its gene dosage. The gene could also suppress the temperature sensitivity of the htr1 disruptant (Kikuchi et al. (1994) Mol. Gen. Genet. 245, 107-116) and was physically mapped in the region near PEP3 on chromosome XII R. The predicted gene product (29,999 Da) is basic and partially homologous to various histone H1. The level of the gene expression increased 2-fold when exposed to mating pheromone.