Foreign transcriptional enhancers in yeast. I. Interactions of papovavirus transcriptional enhancers and a quiescent pseudopromoter on supercoiled plasmids.

We have constructed simple test-plasmids to study transcriptional enhancers in yeast. In this paper the reporter-gene is a plasmid borne deletion-substitution derivative (his-del4) of the Saccharomyces cerevisiae HIS3 gene in which the native promoter has been replaced by a dormant, susceptible pseudopromoter. We investigate the function in yeast of foreign control elements, the polyomavirus enhancer and some of its derivatives, inserted in either orientation at the 3' or 5' ends of the reporter gene. The polyoma enhancer (and, although less thoroughly studied, the SV40 enhancer) will strongly activate transcription from latent start sites within the pseudo-promoter sequence. The rules we draw for the polyoma enhancer effect in yeast are, with a few interesting exceptions, remarkably similar to those discovered by experimentation in mammalian cells.