Effect on yeast LEU2 expression of upstream activation sequence from yeast ENO2 gene coding for enolase

The upstream activation sequence from ENO2, one of two genes coding for yeast enolase, was inserted into the upstream 405 HpaI site of LEU2, which codes for beta-isopropylmalate dehydrogenase (E.C. 1.1.1.85), utilizing shuttle plasmid YEp13. The effect of the ENO2 upstream activation sequence on expression of yeast LEU2 was studied. Our results revealed a fourfold increase in expression for LEU2 in both orientations after activation by the ENO2 upstream activation sequence. Leucine repressed LEU2 expression. Glucose did not induce the ENO2 upstream activation sequence effect on LEU2 expression. It is possible to construct a high-level expression system in yeast by using the ENO2 upstream activation sequence.