Figure 3.

Acetylation changes the interactions of SWI/SNF with the H3 histone tail. (A) Mononucleosomes coupled to photoreactive I¹²⁵-PEAS at residues 3, 7, 15 or 22 in the H3 tail were acetylated by yGcn5/Ada2/Ada3 SAGA subcomplex (lanes 1–8). Other nucleosomes had I¹²⁵-PEAS coupled to residues 15 or 22 in the H4 tail and were acetylated by Piccolo NuA4 (lanes 9–14). Nucleosomes were analyzed before (odd lanes) and after acetylation (even lanes) on a 4% native PAGE. (B) SWI/SNF subunits labeled by crosslinking at positions 3, 7, 15 and 22 of H3 were separated on 4–12% Bis–Tris SDS–PAGE and visualized by phosphorimaging. The quantification of these profiles are overlaid using Image Quant software (Molecular Dynamics) for non-acetylated and yGcn5/Ada2.Ada3 acetylated nucleosomes as shown along with the positions of the Swi2/Snf2, Snf5, Swp82, SWP73, Arp7/9 and Snf6 subunits of SWI/SNF. (C) The same approach as in (B) was used to determine which SWI/SNF subunits were crosslinked at positions 15 and 22 of H4 in non-acetylated and Piccolo NuA4 acetylated nucleosomes.