Fig. 4.

Arp5 interactions with the acidic pocket of the histones H2A-H2B dimer requires Arp8 and Arp4 binding to extranucleosomal DNA. a Locations of the aspartate (D) and glutamate (E) residues constituting the acidic pocket on histone H2A-H2B dimer surface are highlighted in red³¹. The sites of the modified cysteine residues used to map histone interactions of wild type and Arp8ΔN INO80 are shown as black spheres. b–d Phosphorimages of INO80 subunits tagged by crosslinking and [¹²⁵I] radiolabel-transfer. Crosslinked Arp5, Ino80, and Ies2 subunits are indicated on the left. c Crosslinked Arp5 was distinguished from co-migrating Ies1 using INO80 with C-terminally HA-tagged Arp5 (Arp5-HA). d The crosslinking patterns of wild type and Arp8ΔN INO80 are compared. e Plots showing the crosslinking efficiencies of wild type and Arp8ΔN INO80 to the H2A-H2B dimer surface. Values are mean of three experiments, normalized to the Ino80 subunit of wild type at H2B44. Error bars denote ± s.d. f The role of the Arp8 module in regulating INO80 chromatin remodeling in a linker DNA-length dependent manner is illustrated. The Arp8 and Arp5 modules are depicted along with the ATPase domain of Ino80, all as a part of the INO80 complex. As nucleosomes are moved closer together, binding of the Arp8 module to linker DNA is disrupted, which in turn causes the Arp5 module to lift off from the histone dimer surface and the ATPase domains moves away from the core nucleosome. These conformational changes uncouple the ATP hydrolysis from the nucleosome mobilization activitiy of INO80