Even-skipped (Eve) is a transcriptional repressor involved in segment forma
tion in Drosophila melanogaster, In order to gain further insights into the
mechanism of action of Eve we tested whether it would function as a transc
riptional repressor in mammalian cells. We found that Eve was indeed a pote
nt repressor in two different mammalian cell types and at several promoters
. In vitro transcription assays confirmed that Eve directly represses trans
cription initiation when specifically targeted to a promoter. We also found
that, unlike the case with transcriptional activators, Eve does not repres
s transcription synergistically, Analysis of the effect of Eve on preinitia
tion complex assembly in a crude HeLa cell nuclear extract demonstrated tha
t the Eve repression domain functions by preventing the assembly of TFIID w
ith the promoter. Our data support the hypothesis that Eve contains an acti
ve repression domain that functions specifically to prevent preinitiation c
omplex formation.