Caenorhabditis elegans mediator complexes are required for developmental-specific transcriptional activation

Mediator proteins are required for transcriptional regulation of most genes in yeast. Mammalian Mediator homologs also function as transcriptional coa ctivators in vitro; however, their physiological role in gene-specific tran scription is not yet known. To determine the role of Mediator proteins in t he development of complex organisms, we purified putative Mediator complexe s from Caenorhabditis elegans and analyzed their phenotypes in vivo. C. ele gans Mediator homologs were assembled into two multiprotein complexes. RNA interference assays showed that the CeMed6, CeMed7, and CeMed10/CeNut2 gene products are required for the expression of developmentally regulated gene s, but are dispensable for expression of the ubiquitously expressed genes t ested in this study. Therefore, the gene-specific function of Mediator as a n integrator of transcriptional regulatory signals is evolutionarily conser ved and is essential for C. elegans development.