A new gene (SMS1; serine-rich multi-copy suppressor) of Saccharomyces cerevisiae was isolated by the ability to suppress the temperature sensitivity of the htrl disruptant (Kikuchi et al. (1994) Mol. Gen. Genetics, in press) by increasing its gene dosage. The predicted gene product contains a serine-rich domain followed by a putative transmembrane region. The SMS1 gene was physically and genetically mapped in the region near cdc3 on chromosome XII R.