Activator

Activator domains are modular proteins that stimulate transcription via communicating with the transcription machinery "pre-initation complex" (PIC)^[1].

Activators mechanisms

They work synergistically as it promotes binding of an additional activator. The binding of one activator on a UAS induces the binding of another. Together these two have a greater effect on enhancing transcription than just the total of both acting independently. They bind to an enhancer to facilitate either the recruitment of RNA polymerase II to the promoter region or its elongation^[2] [3].

References

1. ↑ Lodish, H. et al.,2007.Molecular Cell Biology.Sixth Edition.New york:W.H.Freeman & Co Ltd.
2. ↑ http://www.ncbi.nlm.nih.gov/pubmed/22180087
3. ↑ transcriptional activators and mechanisms (http://www.ncbi.nlm.nih.gov/pubmed/22180087)