CONSTRUCTION OF GLUCOSE-REPRESSIBLE YEAST EXPRESSION VECTORS

A set of two episomal yeast expression vectors, pYME1 and pYME2, were constructed. These Saccharomyces cerevisiae-Escherchia coli shuttle ve ctors each contain a modified yeast MAL6S (encoding maltase) promoter that is expressed constitutively, but is subject to carbon catabolite repression by glucose. Expression from this promoter is still dependen t upon the presence of active MALR (regulatory) protein. These express ion vectors are particularly useful because most S. cerevisiae strains are MAL(+), thereby exhibiting a wider host range than GAL-based vect or systems. These pYME1 and pYME2 vectors are capable of expression to levels comparable to GAL-based expression plasmids and much higher th an a variety of other repressible promoter vectors. The vectors are id entical, except that their multiple cloning sites (MCS) are in opposit e orientations, making them convenient for inserting heterologous gene s.