title: Mediator expression profiling epistasis reveals a signal transduction pathway with antagonistic submodules and highly specific downstream targets.
abstract: Mediator is an evolutionarily conserved coregulator of RNA polymerase II transcription. Microarray structure-function analysis of S. cerevisiae Mediator reveals functional antagonism between the cyclin-dependent kinase (Cdk) submodule and components from the Tail (Med15, Med2, Med3), Head (Med20, Med18), and Middle (Med31). Certain genes exhibit increased or decreased expression, depending on which subunit is deleted. Epistasis analysis with expression-profile phenotypes shows that MED2 and MED18 are downstream of CDK8. Strikingly, Cdk8-mediated modification of a single amino acid within Mediator represses the regulon of a single transcription factor, Rcs1/Aft1. Highly specific gene regulation is thought to be determined by activators and combinatorial use of cofactors. Here, subtle modification of the general transcription machinery through one of its own components is shown to determine highly specific expression patterns. Expression profiling can therefore precisely map regulatory cascades, and our findings support a role for Mediator as a direct processor of signaling pathways for determining specificity.
authors.affiliation: Department of Physiological Chemistry, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: van de Peppel
authors.forename: Nienke
authors.initials: N
authors.lastname: Kettelarij
authors.forename: Harm
authors.initials: H
authors.lastname: van Bakel
authors.forename: Thessa T J P
authors.initials: TT
authors.lastname: Kockelkorn
authors.forename: Dik
authors.initials: D
authors.lastname: van Leenen
authors.forename: Frank C P
authors.initials: FC
authors.lastname: Holstege
mesh_terms: D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D056850:Cyclin-Dependent Kinase 8; D018844:Cyclin-Dependent Kinases / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D004843:Epistasis, Genetic; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D056892:Mediator Complex; D010766:Phosphorylation; D012319:RNA Polymerase II / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D002868:Chromosomal Proteins, Non-Histone; C470560:MED2 protein, S cerevisiae; C107274:MED6 protein, S cerevisiae; D056892:Mediator Complex; C501075:RSC1 protein, S cerevisiae; C082149:SRB5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D056850:Cyclin-Dependent Kinase 8; D018844:Cyclin-Dependent Kinases; C498309:SSN3 protein, S cerevisiae; D012319:RNA Polymerase II