NEW EUKARYOTIC TRANSCRIPTIONAL REPRESSORS

TRANSCRIPTIONAL activating sequences have been described1 that are enc oded by parts of the genome of Escherichia coli. These acidic peptides , fused to a DNA-binding fragment of the yeast transcriptional activat or GAL4, activate transcription of a gene in a wide array of eukaryote s, provided that gene bears GAL4-binding sites nearby2-4. Here we desc ribe an E. coli-encoded sequence that, when attached to the same DNA-b inding fragment (GAL4(1-147)), converts that fragment into a repressor . Thus, as assayed in yeast or in vitro in yeast extracts, this molecu le represses transcription when bound upstream of a variety of differe nt activators. Two additional repressing regions that work when tether ed upstream, a multiple mutant derivative of the original isolate and a synthetic peptide are, like the original isolate, highly basic. At l east one activator can be inhibited by the mutant but not by the paren tal repressing region. These and other findings suggest that these rep ressing regions interact with and inhibit the activity of activating r egions bound nearby on DNA.