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Updated: Aug 16, 2026

Using Human Differentially Expressed Gene Lists to Perform Downstream Pathway Enrichment Analysis and Target Prioritization
Published on: October 3, 2025
Mediator expression profiling epistasis reveals a signal transduction pathway with antagonistic submodules and highly
Jeroen van de Peppel1, Nienke Kettelarij, Harm van Bakel
1Department of Physiological Chemistry, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
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.
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