Final answer:
Activators bind to the activator binding site, and assist in the regulation of gene expression by enhancing the interaction between RNA polymerase and the promoter. In prokaryotic gene regulation, this is often mediated by proteins like the catabolite activator protein (CAP), while in eukaryotic cells, transcriptional activators can bind to enhancer regions to facilitate gene transcription.
Step-by-step explanation:
Activators are regulatory proteins that bind to specific DNA sites adjacent to the genes they control. In the context of prokaryotic gene regulation, activators typically bind to an activator binding site rather than an operator. For example, the catabolite activator protein (CAP) complexes with cyclic AMP (cAMP) and binds to the promoter sequences of operons controlling sugar processing when glucose is not available.
In eukaryotic cells, transcriptional activators can bind to enhancer regions of DNA. These enhancers are not necessarily close to the promoter region in terms of linear distance along the DNA molecule but can interact with the promoter region due to the three-dimensional folding of the DNA. This facilitates the transcription of specific genes by enhancing the interaction between RNA polymerase and the promoter.
Activators function by stabilizing the formation of the transcription initiation complex, through allosteric changes and shape shifting of the DNA, enabling more efficient transcription by RNA polymerase II.