Figure 55.

Preparation and application of asymmetric mononucleosomes. (a) Synthesis of asymmetrically modified nucleosomes using a tagged, modified copy of H3 and an excess of an unmodified version. (b) The SAGA-complex is stimulated by its own mark. Nucleosomes that can only be acetylated on one H3 tail (tail-less and Lys9,14,18,23Ala) are poor SAGA substrates (gray arrows). Asymmetrically acetylated nucleosomes (right) recruit SAGA (dashed arrow) to promote acetylation of the unmodified H3 tail.