Genome-wide occupancy profile of mediator and the srb8-11 module reveals interactions with coding regions.

Genome wide interaction of mediator Keywords: Genome wide interaction of mediator The Mediator complex is involved in preinitiation complex formation and required for the regulated expression of many genes. Mediator exists in two distinct forms, a free form, which contains the Med12, Med13, CDK8, and CycC subunits (Srb8-11), and a smaller form, which lacks these four subunits and associates with RNA polymerase II to form a holoenzyme. Here we use chromatin immuno-precipitation and DNA microarrays to investigate the genome wide localization of Mediator and the Srb8-11 module in fission yeast. Mediator and the Srb8-11 module display very similar genome-wide binding patterns and the Srb8-11 module remains present also at highly transcribed genes. The occupancy profile of Mediator and the Srb8-11 module is distinct from both Pol II and general transcription factors. Unexpectedly, Mediator binds not only to promoters and upstream activating sequences, but also to the downstream coding regions of many genes. Codon region binding does not correlate significantly with transcription activity, but increased Mediator occupancy can be observed after induction of some highly transcribed genes.