In Vivo Requirement of Activator-Specific Binding Targets of Mediator

Abstract

There has been no unequivocal demonstration that the activator binding targets identified in vitro play a key role in transcriptional activation in vivo. To examine whether activator-Mediator interactions are required for gene transcription under physiological conditions, we performed functional analyses with Mediator components that interact specifically with natural yeast activators. Different activators interact with Mediator via distinct binding targets. Deletion of a distinct activator binding region of Mediator completely compromised gene activation in vivo by some, but not all, transcriptional activators. These demonstrate that the activator-specific targets in Mediator are essential for transcriptional activation in living cells, but their requirement was affected by the nature of the activator-DNA interaction and the existence of a postrecruitment activation process.

ACKNOWLEDGMENTS

We thank Alan Hinnebusch, Randall Morse, Toshio Fukasawa, Hiroshi Sakurai, Masafumi Nishizawa, Richard Reese, Richard Young, Andrés Aguilera, and Roger Kornberg for yeast strains, plasmids, and antibodies; Kelly LaMarco for careful reading of the manuscript; and our colleagues in the Kim lab for helpful discussion.

This work was supported by the Creative Research Initiatives Program and the Molecular Medicine Research Group Program (98-J03-01-01-A-05) from the Korean Ministry of Science and Technology to Y.-J.K.