Balancing transcriptional interference and initiation on the GAL7 promoterof Saccharomyces cerevisiae

Transcriptional termination of the GAL10 gene in Saccharomyces cerevisiae d epends on the efficiency of polyadenylation. Either cis mutations in the po ly(A) signal or trans mutations of mRNA 3' end cleavage factors result in G AL10 read-through transcripts into the adjacent GAL7 gene and inactivation (occlusion) of the GAL7 promoter. Herein. we present a molecular explanatio n of this transcriptional interference phenomenon. In vivo footprinting dat a reveal that GAL7 promoter occlusion is associated with the displacement o f Gal4p transcription factors from the promoter. Interestingly, overexpress ion of Gal4p restores promoter occupancy, activates GAL7 expression, and re scues growth on the otherwise toxic galactose substrate. Our data therefore demonstrate a precise balance between transcriptional interference and ini tiation.