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.