NEW EUKARYOTIC TRANSCRIPTIONAL REPRESSORS

TRANSCRIPTIONAL activating sequences have been described1 that are encoded by parts of the genome of Escherichia coli. These acidic peptides, fused to a DNA-binding fragment of the yeast transcriptional activator GAL4, activate transcription of a gene in a wide array of eukaryotes, provided that gene bears GAL4-binding sites nearby2-4. Here we describe an E. coli-encoded sequence that, when attached to the same DNA-binding fragment (GAL4(1-147)), converts that fragment into a repressor. Thus, as assayed in yeast or in vitro in yeast extracts, this molecule represses transcription when bound upstream of a variety of different activators. Two additional repressing regions that work when tethered upstream, a multiple mutant derivative of the original isolate and a synthetic peptide are, like the original isolate, highly basic. At least one activator can be inhibited by the mutant but not by the parental repressing region. These and other findings suggest that these repressing regions interact with and inhibit the activity of activating regions bound nearby on DNA.