[Mediator complexes in gene transcription]

Major progresses have been made in recent years in understanding of the molecular mechanism involved in gene transcriptional regulation; these include the cloning and identification as well as functional analysis of mediator complexes. Mediator complexes, which consist of more than 20 protein subunits, have been found in a variety of eukaryotes including yeast, mouse and human. Mediators are capable of interacting with both transcription factors and RNA polymerase II, and thus are believed to participate in the transcription process by bridging specific transcription factors and the basal transcriptional machinery. The functional consequences of mediator complexes in gene regulation could be either positive or negative. This review is focused on recent findings regarding the composition, the structure and the function of mediator complexes.