The Saccharomyces cerevisiae PGK (phosphoglycerate kinase) gene encodes one of the most abundant mRNA and protein species in the cell. To identify the promoter sequences required for the efficient expression of PGK, we undertook a detailed internal deletion analysis of the 5' noncoding region of the gene. Our analysis revealed that PGK has an upstream activation sequence (UASPGK) located between 402 and 479 nucleotides upstream from the initiating ATG sequence which is required for full transcriptional activity. Deletion of this sequence caused a marked reduction in the levels of PGK transcription. We showed that PGK has no requirement for TATA sequences; deletion of one or both potential TATA sequences had no effect on either the levels of PGK expression or the accuracy of transcription initiation. We also showed that the UASPGK functions as efficiently when in the inverted orientation and that it can enhance transcription when placed upstream of a TRPI-IFN fusion gene comprising the promoter of TRPI fused to the coding region of human interferon a-2.In the yeast Saccharomyces cerevisiae the PGK (phosphoglycerate kinase) gene encodes one of the most abundant mRNA and protein species in the cell, accounting for 1 to 5% of the total cellular mRNA and protein (22). The PGK gene has been cloned and characterized (11,21), and the 5' noncoding region has been found to contain sequences which are common to the promoters of all efficiently expressed yeast genes (11). When the PGK gene is present on a high-copy-number plasmid, phosphoglycerate kinase protein makes up approximately 50% of the total cell protein (31, 32). For this reason the promoter region of PGK has been used to construct some of the most powerful expression vectors available. These vectors have been used to direct the efficient synthesis of a number of heterologous gene products in yeasts (9,31,32,49,51). In these systems the promoter used comprises 1,500 base pairs (bp) upstream from the initiating ATG.Previous studies on the promoters of yeast genes have revealed a number of control elements which are required for accurate and efficient transcription. One element, the TATA box, found in the 5'-flanking regions of virtually all protein-encoding eucaryotic genes (see reference 4 for a review), has been shown to be required for setting the site of transcription initiation (16, 17, 27a, 35, 41, 44) and, in some cases, maintaining levels of transcription (16,44). A second element, the upstream activation sequence (UAS), has been found in the 5' noncoding regions of a number of yeast genes, usually several hundred nucleotides upstream from the TATA box (14,16,26,39,44,52). UASs have certain features in common. First, deletion of these sequences causes a marked reduction in levels of transcription. Second, in several cases the role of a UAS in activating transcription is subject to regulation dependent on the physiological condition of the cells (16,50,54). Third, hybrid gene constructions have shown that a UAS can drive transcription of a heterologous gen...