GCR1-DEPENDENT TRANSCRIPTIONAL ACTIVATION OF YEAST RETROTRANSPOSON TY2-917

Transcription of Saccharomyces cerevisiae Ty2-917 retrotransposon depe nds on regulatory elements both upstream and downstream of the transcr iption initiation site. An upstream activation sequence (UAS) and a do wnstream enhancer stimulate transcription synergistically. Here we sho w that activation by both of these sites depends on the GCR1 product, a transcription factor which also regulates the genes encoding yeast g lycolytic enzymes. Eliminating GCR1 causes a 100-fold decrease in tran scription of Ty2-917. Activation by the isolated Ty2-917 UAS also stro ngly depends on GCR1. Unexpectedly, GCR1-dependent activation by the T y2-917 enhancer is strongly position-dependent. Activation by the enha ncer in its normal position within the transcription unit depended str ongly on GCR1, but eliminating GCR1 reduced activation only three-fold when the enhancer was moved upstream of the transcribed region. Gel m obility shift and DNaseI protection assays indicated that GCR1 binds s pecifically to multiple sites within the Ty2-917 UAS and enhancer regi ons. (C) 1997 by John Wiley & Sons, Ltd.