Metallothioneins constitute a class of low-molecular-weight, cysteine-rich metal-binding stress proteins which are biosynthetically regulated at the level of gene transcription in response to metals, hormones, cytokines, and other physiological and environmental stresses. In this report, we demonstrate that the Saccharomyces cerevisiae metallothionein gene, designated CUP), is transcriptionally activated in response to heat shock and glucose starvation through the action of heat shock transcription factor (HSF) and a heat shock element located within the CUP) promoter upstream regulatory region. CUP) gene activation in response to both stresses occurs rapidly; however, heat shock activates CUP) gene expression transiently, whereas glucose starvation activates CUP) gene expression in a sustained manner for at least 2.5 h. Although a carboxylterminal HSF transcriptional activation domain is critical for the activation of CUP) transcription in response to both heat shock stress and glucose starvation, this region is dispensable for transient heat shock activation of at least two genes encoding members of the S. cerevisiae hsp7O family. Furthermore, inactivation of the chromosomal SNFI gene, encoding a serine-threonine protein kinase, or the SNF4 gene, encoding a SNF1 cofactor, abolishes CUPI transcriptional activation in response to glucose starvation without altering heat shock-induced transcription. These studies demonstrate that the S. cerevisiae HSF responds to multiple, distinct stimuli to activate yeast metallothionein gene transcription and that these stimuli elicit responses through nonidentical, genetically separable signalling pathways.The activation of gene transcription plays a vital role in the ability of all organisms to mount a protective response to environmental stresses. Upon exposure to a specific stress, cells activate the transcription of genes encoding proteins which either offer protection from the stress or repair stressinduced cellular damage. Although the precise mechanisms by which cells sense and respond to a specific environmental stress to activate the transcription of appropriate target genes are unknown, a growing number of transcription factors which participate in stress signal transduction pathways have been identified (14,19,28,46). Metallothioneins (MTs) are a class of low-molecular-weight, cysteine-rich metal-binding stress-responsive proteins which are present in bacteria, fungi, plants, and animals (25). Since the discovery of MTs, a number of biological roles have been postulated, including protection from metal toxicity, metal homeostasis, free radical detoxification, and protection from ionizing radiation. Indeed, consistent with these possible roles, MT genes in higher eukaryotic species are transcriptionally induced by a variety of stresses such as metals, glucocorticoid hormones, interferon, interleukins, and other agents involved in the inflammatory response or which generate oxidative stress (6,46