Figure 8. Cbx3 association with mediator components.

A) Cbx3 co-localizes with Mediator at the TSS. Heatmap of Cbx3 and Mediator (Med1 subunit) enrichment in pre-iPSCs for all genes from 5kb upstream to 5kb downstream of the TSS, divided into five groups based on K-means co-clustering, based on ChIP-seq. Blue denotes enrichment in a 100bp bin normalized to 1 million reads subtracted from normalized input values; values were log2 transformed.

B) Cbx3 precipitates more efficiently with Med29 in differentiated cells than ESCs. Immunoprecipitates (IP) of Flag-Med29 from ESCs and differentiated cells (neural precursors differentiated from ESCs) were probed with antibodies to Cbx3 or Med6 by western blotting (WB). 1% of input and 5% of IP are shown. Equal amounts of Cbx3 and Med6 are present in inputs from both cell types.. Cbx3 but not the control Med26 is enriched in the Med29 IP in NPCs.

C) Cbx3 is recruited to the PIC in an activator-dependent manner. Transcriptional preinitiation complexes (PICs) were formed in the presence and absence of a model activator GAL4-VP16 in nuclear extract. Note that Cbx3 was only incorporated in the PIC when the VP16 transcriptional activator was present, similar to Mediator (subunits Med1, Med6, Cdk8) and the Mll complex component Rbbp5. Uncropped scans are available in Figure Supp Fig 5.