The Mediator complex stimulates the cooperative assembly of a pre-initiation complex (PIC) and recruitment of RNA Polymerase II (Pol II) for gene activation. The core Mediator complex is organized into head, middle, and tail modules, and in budding yeast (Saccharomyces cerevisiae), Mediator recruitment has generally been ascribed to sequence-specific activators engaging the tail module triad of Med2-Med3-Med15 at upstream activating sequences (UASs). We show that yeast lacking Med2-Med3-Med15 are viable and that Mediator and PolII are recruited to promoters genome-wide in these cells, albeit at reduced levels. To test whether Mediator might alternatively be recruited via interactions with the PIC, we examined Mediator association genome-wide after depleting PIC components. We found that depletion of Taf1, Rpb3, and TBP profoundly affected Mediator association at active gene promoters, with TBP being critical for transit of Mediator from UAS to promoter, while Pol II and Taf1 stabilize Mediator association at proximal promoters.
Data from ChIP-seq and RNA-seq experiments have been deposited at the NCBI Short Read Archive under project number PRJNA413080.
Data from ChIP-seq and RNA-seq experimentsShort Read Archive, PRJNA413080.
- Elisabeth R Knoll
- Debasish Sarkar
- Randall H Morse
- Z Iris Zhu
- David Landsman
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Alan G Hinnebusch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, United States
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