Abstract: Novel DNA constructs comprising yeast regulatory regions plus the structural coding region for human tumor necrosis factor, are disclosed. These novel constructs are incorporated into a variety of linear and circular plasmids. Such plasmids are used for yeast transformation and ultimately for the production of human tumor necrosis factor by yeast.

Abstract: Yeast strains are transformed with, and selected for, using DNA fragments encoding a gene function not present in the wild-type yeast strains. The invention requires transforming the yeast with DNA fragments which comprise the gene function which the wild-type yeast strain is lacking; regeneration of the transformants on a non-selective regeneration medium; then selection of those colonies which are capable of growth on a carbon and energy source which requires expression of the gene function provided by the DNA fragment. Thus, transformation with such DNA fragments allows for positive selection of transformed strains.