Repressors often act by preventing RNA polymerase from forming a productive complex with the transcriptional initiation region (promoter), while activators facilitate formation of a productive complex.
Os represores a miúdo actúan impedindo que a ARN polimerase forme un complexo produtivo coa rexión de iniciación da transcrición (promotor), mentres que os activadores facilitan a formación dun complexo produtivo.