Activators usually bind upstream of the-35 sequence of the promoter, where they can make contact with the rna polymerase bound to the promoter. repressors often bind to the promoter region itself, or at least very close to it, and thereby block access by rna polymerase to the promoter Some regulatory proteins can be both repressors and activators depending upon the situation. The n repressor is an example. It represses transcription from the the pi and pr promoters but activates the prM promoter. The binding site on the dna for the regulatory protein often changes when the protein shifts from being an activator to a repressor• Activators usually bind upstream of the -35 sequence of the promoter, where they can make contact with the RNA polymerase bound to the promoter. Repressors often bind to the promoter region itself, or at least very close to it, and thereby block access by RNA polymerase to the promoter. • Some regulatory proteins can be both repressors and activators, depending upon the situation. The λ repressor is an example. It represses transcription from the the pL and pR promoters but activates the pRM promoter. The binding site on the DNA for the regulatory protein often changes when the protein shifts from being an activator to a repressor