Regulation of Rvb1/Rvb2 by a Domain within the INO80 Chromatin Remodeling Complex Implicates the Yeast Rvbs as Protein Assembly Chaperones

Publication date: 6 June 2017
Source:Cell Reports, Volume 19, Issue 10
Author(s): Coral Y. Zhou, Caitlin I. Stoddard, Jonathan B. Johnston, Michael J. Trnka, Ignacia Echeverria, Eugene Palovcak, Andrej Sali, Alma L. Burlingame, Yifan Cheng, Geeta J. Narlikar
The hexameric AAA+ ATPases Rvb1 and Rvb2 (Rvbs) are essential for diverse processes ranging from metabolic signaling to chromatin remodeling, but their functions are unknown. While originally thought to act as helicases, recent proposals suggest that Rvbs act as protein assembly chaperones. However, experimental evidence for chaperone-like behavior is lacking. Here, we identify a potent protein activator of the Rvbs, a domain in the Ino80 ATPase subunit of the INO80 chromatin-remodeling complex, termed Ino80INS. Ino80INS stimulates Rvbs' ATPase activity by 16-fold while concomitantly promoting their dodecamerization. Using mass spectrometry, cryo-EM, and integrative modeling, we find that Ino80INS binds asymmetrically along the dodecamerization interface, resulting in a conformationally flexible dodecamer that collapses into hexamers upon ATP addition. Our results demonstrate the chaperone-like potential of Rvb1/Rvb2 and suggest a model where binding of multiple clients such as Ino80 stimulates ATP-driven cycling between hexamers and dodecamers, providing iterative opportunities for correct subunit assembly.

Graphical abstract

Teaser

Rvb1 and Rvb2 (Rvbs) are AAA+ ATPases that have been hypothesized to assemble multi-subunit protein complexes, though this activity has not been experimentally demonstrated. Zhou et al. find that a domain within the chromatin remodeling Ino80 ATPase is a potent activator of Rvb1/Rvb2, creating a metastable dodecamer of Rvb/1Rvb2 that dissociates upon ATP addition.


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