[25] Vectors for expression of cloned genes in yeast: Regulation, overproduction, and underproduction

It is necessary to separate a gene from its own promoter to control expression of its product in different conditions or to produce the product to a greater or lesser degree than normal. This chapter discusses the yeast transcription cassettes of several types used for the expression of cloned genes. The first type includes vectors with regulatable promoters; GAL, PGK, and ADH1 respond to the carbon source, and PH05 responds to the inorganic phosphate concentration. These vectors allow the expression of the cloned gene to be turned on and off by changes in the growth medium. Another class creates a protein fusion to an amino-terminal signal sequence so that the protein are secreted from the cell. A third kind of cassette makes protein fusions of the cloned gene to the coding region for another protein, such as β-galactosidase, or to a small antigenic epitope. Therefore, proteins for which there is no antibody or convenient assay available can be tagged with a heterologous enzymatic activity or antigen.