22 bp cis-acting element is necessary and sufficient for the induction of the yeast KAR2 (BiP) gene by unfolded proteins

• Published in: The EMBO journal 1992-07, Vol.11 (7), p.2583-2593
• Main Authors: Mori, K, Sant, A, Kohno, K, Normington, K, Gething, M.J, Sambrook, J.F
• Format: Article
• Language: English
• Subjects: Base Sequence; beta-Galactosidase - metabolism; binding proteins; Binding Sites; Biological and medical sciences; Blotting, Northern; chaperone protein; DNA, Fungal - metabolism; DNA-binding proteins; endoplasmic reticulum; Fundamental and applied biological sciences. Psychology; Fungal Proteins - genetics; Gene expression; Gene Expression Regulation, Fungal; Genes, Fungal; genetic regulation; heat shock elements; heat stress; Heat-Shock Proteins - genetics; HSP70 Heat-Shock Proteins; messenger RNA; Molecular and cellular biology; molecular conformation; Molecular genetics; Molecular Sequence Data; Mutagenesis, Site-Directed; mutants; nucleotide sequences; Plasmids; promoter regions; Promoter Regions, Genetic; Protein Conformation; RNA, Fungal - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Sequence Homology, Nucleic Acid; structural genes; transcription (genetics); transcription factors; Transcription Factors - metabolism; transposons; unfolded protein-response element; upr element
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1992.tb05323.x

The KAR2 gene of Saccharomyces cerevisiae codes for an essential chaperone protein (BiP) that is localized in the lumen of the endoplasmic reticulum (ER). The high basal rate of transcription of KAR2 is increased transiently by heat shock: prolonged induction occurs when unfolded proteins accumulate in the ER. Three cis-acting elements in the KAR2 promoter control expression of KAR2: (i) a GC-rich region that contributes to the high level of constitutive expression, (ii) a functional heat shock element (HSE) and (iii) an element (UPR) that is involved in the induction of BiP mRNA by unfolded proteins. By analyzing internal deletion mutants of the KAR2 promoter, we demonstrate here that these three elements regulate transcription of KAR2 independently. Furthermore, the 22 bp UPR element causes a heterologous (CYC1) promoter to respond to the presence of unfolded proteins in the ER. Extracts of both stressed and unstressed yeast cells contain proteins that bind specifically to synthetic HSE and UPR elements and retard their migration through gels. Binding proteins specific for the UPR element can be fractionated by ammonium sulfate precipitation. Two of the proteins UPRF-1 and UPRF-2 (which is apparently a proteolytic degradation product of UPRF-1) bind inefficiently to mutant versions of the UPR that are unable to confer responsiveness to unfolded proteins to the (CYC1) promoter. UPRF-1 therefore displays the properties expected of a transcription factor that is involved in the sustained response of the KAR2 promoter to unfolded proteins in the ER. These experiments show that yeast cells can activate a transcription factor that stimulates expression of a nuclear gene in response to the accumulation of unfolded proteins in another cellular compartment.