Figure 6. Identification of protein complexes by ChIP analysis demonstrates cell-specific binding of Sp1 and active RNA polymerase II to the Ccna1 promoter as well as an enrichment of H3K27me3.

Antibodies to Sp1, H3K27me3 or the corresponding IgG control were used to immunoprecipitate protein/DNA complexes from sonicated lysates of indicated cells or a tissue equivalent to 10⁶ cells in each case. After reversing the cross-linking, bound DNA was isolated and PCR was performed using primers that amplify the −290 to -100 bp region of the Ccna1 promoter to detect bound Sp1 and H3K27me3 and the –120 to +90 bp region of the Ccna1 promoter to detect RNA polymerase II binding.