Evolutionary conserved mechanism of transcriptional repression by even-skipped

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.