Now, we also have the transcription factor to be, and this is the protein that is needed for the interaction to take place between the RNA polymerase, two protein found on the start side, and the task of binding protein. So that's why we need the transcription factor two B. So we see that the core promoter is where the majority of the proteins actually congregate when they actually bind. Now, what about these other upstream promoters? So these are known as the upstream promoters. What's so special about the upstream promoters?