TANDEMLY REPEATED 147 BP ELEMENTS CAUSE STRUCTURAL AND FUNCTIONAL VARIATION IN DIVERGENT MAL PROMOTERS OF SACCHAROMYCES-CEREVISIAE

We have studied four novel MAL promoters isolated from a single strain of bakers' yeast. Within these promoters we have identified up to fiv e tandem 147 bp repeats located between the MAL UAS region and the MAL T TATA box. These repeats strongly reduce MALT (maltose permease) gene expression but only weakly reduce MALS (maltase) gene expression. Ins ertion of the 147 bp elements into the heterologous CYC1 promoter redu ced expression when located between the CYC1 UAS and the TATA box, but not when located upstream of the UAS. We propose that these naturally occurring repeats have evolved as a mechanism to lower the level of M ALT expression relative to MALS expression, thus avoiding possible tox ic effects associated with over-expression from multiple copies of the permease gene. Accession numbers are: WIG1, U86359; WIG3, U86360; WIG 4, U86361; WIG5, U86362. (C) 1997 John Wiley & Sons, Ltd.