Mediator is an intrinsic component of the basal RNA polymerase II machinery in vivo

• Published in: Nucleic acids research Vol. 41; no. 21; pp. 9651 - 9662
• Main Authors: Lacombe, Thierry, Poh, Siew Lay, Barbey, Régine, Kuras, Laurent
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01-11-2013
• Subjects: Cysteine Synthase - genetics; DNA-Binding Proteins - metabolism; Gene Regulation, Chromatin and Epigenetics; Life Sciences; Mediator Complex - metabolism; Mutation; Promoter Regions, Genetic; Regulatory Factor X Transcription Factors; RNA Polymerase II - metabolism; Saccharomyces cerevisiae Proteins - genetics; TATA-Box Binding Protein - metabolism; Transcription Factor TFIIB - metabolism; Transcription Factors - metabolism; Transcription, Genetic; Transcriptional Activation
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gkt701

Mediator is a prominent multisubunit coactivator that functions as a bridge between gene-specific activators and the basal RNA polymerase (Pol) II initiation machinery. Here, we study the poorly documented role of Mediator in basal, or activator-independent, transcription in vivo. We show that Mediator is still present at the promoter when the Pol II machinery is recruited in the absence of an activator, in this case through a direct fusion between a basal transcription factor and a heterologous DNA binding protein bound to the promoter. Moreover, transcription resulting from activator-independent recruitment of the Pol II machinery is impaired by inactivation of the essential Mediator subunit Med17 due to the loss of Pol II from the promoter. Our results strongly support that Mediator is an integral component of the minimal machinery essential in vivo for stable Pol II association with the promoter.