page_title: Mediator (coactivator)
section_title: Mouse cells and tissues
hierarchical_section_title: Mediator (coactivator) / MED 1 / Mouse cells and tissues
caption_attribution_description: English: A mediator mutation causes hairy teeth in mice
context_page_description: Mediator is a multiprotein complex that functions as a transcriptional coactivator in all eukaryotes. It was discovered in 1990 in the lab of Roger D. Kornberg, winner of the 2006 Nobel Prize in Chemistry. Mediator complexes interact with transcription factors and RNA polymerase II. The main function of mediator complexes is to transmit signals from the transcription factors to the polymerase.
  Mediator complexes are variable at the evolutionary, compositional and conformational levels. The first image shows only one "snapshot" of what a particular mediator complex might be composed of, but it certainly does not accurately depict the conformation of the complex in vivo. During evolution, mediator has become more complex. The yeast Saccharomyces cerevisiae is thought to have up to 21 subunits in the core mediator, while mammals have up to 26.
  Individual subunits can be absent or replaced by other subunits under different conditions. Also, there are many intrinsically disordered regions in mediator proteins, which may contribute to the conformational flexibility seen both with and without other bound proteins or protein complexes.
context_section_description: Conditional mutations can be produced in mice which affect only specific cells or tissues at specific times, so that the mouse can develop to adulthood and the adult phenotype can be studied. In one case, MED1 was found to participate in controlling the timing of events of meiosis in male mice. Conditional mutants in keratinocytes show differences in skin wound healing. A conditional mutant in mice was found to change dental epithelium into epidermal epithelium, which caused hair to grow associated with the incisors.
caption: A mediator mutation causes hairy teeth in mice
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