FACTORS AFFECTING SACCHAROMYCES-CEREVISIAE ADH2 CHROMATIN REMODELING AND TRANSCRIPTION

The chromatin structure of the Saccharomyces cerevisiae ADH2 gene is m odified during the switch from repressing (high glucose) to derepressi ng (low glucose) conditions of growth. Loss of protection toward micro coccal nuclease cleavage for the nucleosomes covering the TATA box and the RNA initiation sites (-1 and +1, respectively) is the major modif ication taking place and is strictly dependent on the presence of the transcriptional activator ADR1. To identify separate functions involve d in the transition from a repressed to a transcribing promoter, we ha ve analyzed the ADH2 chromatin organization in various genetic backgro unds. Deletion of the CCR4 gene coding for a general transcription fac tor impaired ADH2 expression without affecting chromatin remodeling, G rowing yeast at 37 degrees C also resulted in chromatin remodeling at the ADH2 locus even under glucose repressing conditions. However, alth ough this temperature-induced remodeling was dependent on the ADR1 pro tein, no ADH2 mRNA was observed. In addition, inactivating RNA polymer ase II (and therefore, elongation) was found to have no effect on the ability to reconfigure nucleosomes. Taken together, these data indicat e that chromatin remodeling by itself is insufficient to induce transc ription at the ADH2 promoter.