Schematic summary for Rad1–Rad10 and Rad26 in the interplay between Mediator, Rad2, and Pol II. Schematic representation suggests how Rad1–Rad10 and Rad26 findings can be integrated into functional interplay between Mediator, Pol II, and Rad2 that we recently proposed (André et al. 2021). The figure allows us to compare Rad1–Rad10 and Rad26 with Rad2. Our data show similarities between Rad2 and other Rad proteins (Rad26, Rad1–Rad10) in their genomic distribution and physical interactions. They also reveal important differences in their dynamics with respect to Mediator. Activator (Act) is indicated in blue, Rad2 in pink, Pol II in purple, Rad26 in orange, and Rad1–Rad10 dimer in magenta. Mediator subunits are colored according to the modules: in light blue, red, yellow, and green for Mediator tail, head, middle, and Cdk8 kinase modules, respectively. Double-headed arrows indicate interactions between different proteins. (Top) Rad2, Rad1–Rad10, and Rad26 physically interact with Mediator. Moreover, Rad2 and Rad1–Rad10 recruitment to UAS is dependent on Mediator. (Middle) Rad2 was proposed to be transferred to transcribed regions through interactions with Pol II, and a transient Mediator–Pol II intermediate(s) (in brackets), formed at core promoters. A transfer of Rad1–Rad10 between UAS and transcribed regions can be also proposed. (Bottom) A strong correlation was observed between Rad26 and Pol II on transcribed regions. Rad1–Rad10 occupancy was also correlated with Pol II. Chromatin binding of all proteins (Rad1–Rad10, Rad2, and Rad26) was Pol II transcription dependent. Our results suggest that the recruitment mechanisms of Rad26 on UAS and transcribed regions could be independent.
