Final answer:
Transcription activators (ACT) bind to enhancer regions on DNA, causing a shape change that enables their interaction with the transcription initiation complex. This interaction enhances the connection between RNA polymerase and the promoter region, predominantly the TATA box, resulting in an increase in transcription initiation rate.
Step-by-step explanation:
The binding of transcription activators (ACT) plays a crucial role in gene expression within a eukaryotic cell. These activators bind to specific DNA sequences known as enhancer regions, which are located at a distance from the actual genes they regulate. By binding to enhancers, transcription activators induce a change in the shape of DNA. This structural change facilitates the interaction between RNA polymerase and the promoter region of a gene, particularly the TATA box and other associated general transcription factors.
Once a transcription activator is bound to the enhancer, it can then interact with other components of the transcription initiation complex. This includes various cofactors and mediator proteins, enabling the reinforcement of the DNA's bend and thus, bringing the enhancer in close proximity to the promoter. This proximity allows activator proteins to enhance the interaction between RNA polymerase and a particular promoter, effectively increasing the rate of transcription initiation and thus, gene expression.
Moreover, the transcription activator's role is not only limited to enhancing transcription but can also involve recruitment of additional molecules necessary for transcription to commence, such as additional transcription factors and RNA polymerase itself. The phosphorylation of RNA polymerase is also a key event that occurs following transcription factor interactions, and it plays a role in activating the transcription initiation complex for the progression of transcription.