ISOLATION AND IDENTIFICATION OF GENES ACTIVATING UAS2-DEPENDENT ADH2 EXPRESSION IN SACCHAROMYCES-CEREVISIAE

Two cis-acting elements have been identified that act synergistically to regulate expression of the glucose-repressed alcohol dehydrogenase 2 (ADH2) gene. UAS1 is bound by the trans-activator Adr1p. UAS2 is tho ught to be the binding site for an unidentified regulatory protein. A genetic selection based on a UAS2-dependent ADH2 reporter was devised to isolate genes capable of activating UAS2-dependent transcription. O ne set of UAS2-dependent genes contained SPT6/CRE2/SSN20. Multicopy SP T6 caused improper expression of chromosomal ADH2. A second set of UAS 2-dependent clones contained a previously uncharacterized open reading frame designated MEU1 (Multicopy Enhancer of UAS2). A frame shift mut ation in MEU1 abolished its ability to activate UAS2-dependent gene ex pression. Multicopy MEU1 expression suppressed the constitutive ADH2 e xpression caused by cre2-1. Disruption of MEU1 reduced endogenous ADH2 expression about twofold but had no effect on cell viability or growt h. No homologues of MEU1 were identified by low-stringency Southern hy bridization of yeast genomic DNA, and no significant homologues were f ound in the sequence data bases. A MEU1/beta-gal fusion protein was no t localized to a particular region of the cell. MEU1 is linked to PPR1 on chromosome XII.