sentences:  For example, after binding the enhancer and core promoter, the mediator complex undergoes a compositional change in which the kinase module dissociates from the complex to allow association with RNA polymerase II and transcriptional activation.The yeast mediator complex is approximately as massive as a small subunit of a eukaryotic ribosome.The yeast mediator is composed of 25 subunits, while the mammalian mediator complexes are slightly larger.