Nucleosome flipping drives kinetic proofreading and processivity by SWR1

DOI: 10.1038/s41586-024-08152-y

Authors: Paul Girvan (Imperial College London; MRC Laboratory of Medical Science) , Adam S. B, Jalal (Imperial College London) , Elizabeth A. Mccormack (Imperial College London) , Michael T. Skehan (Imperial College London) , Carol L. Knight (Imperial College London) , Dale B. Wigley (Imperial College London) , David S. Rueda (MRC Laboratory of Medical Sciences; Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature , VOL 12

State: Published (Approved)
Published: November 2024
Diamond Proposal Number(s): 36390

Abstract: The yeast SWR1 complex catalyses the exchange of histone H2A–H2B dimers in nucleosomes, with Htz1–H2B dimers1,2,3. Here we used single-molecule analysis to demonstrate two-step double exchange of the two H2A–H2B dimers in a canonical yeast nucleosome with Htz1–H2B dimers, and showed that double exchange can be processive without release of the nucleosome from the SWR1 complex. Further analysis showed that bound nucleosomes flip between two states, with each presenting a different face, and hence histone dimer, to SWR1. The bound dwell time is longer when an H2A–H2B dimer is presented for exchange than when presented with an Htz1–H2B dimer. A hexasome intermediate in the reaction is bound to the SWR1 complex in a single orientation with the ‘empty’ site presented for dimer insertion. Cryo-electron microscopy analysis revealed different populations of complexes showing nucleosomes caught ‘flipping’ between different conformations without release, each placing a different dimer into position for exchange, with the Swc2 subunit having a key role in this process. Together, the data reveal a processive mechanism for double dimer exchange that explains how SWR1 can ‘proofread’ the dimer identities within nucleosomes.

Diamond Keywords: Fungi

Subject Areas: Biology and Bio-materials

Diamond Offline Facilities: Electron Bio-Imaging Centre (eBIC)
Instruments: Krios I-Titan Krios I at Diamond , Krios II-Titan Krios II at Diamond

Added On: 27/11/2024 12:22

Discipline Tags:

Structural biology Biophysics Life Sciences & Biotech

Technical Tags:

Microscopy Electron Microscopy (EM) Cryo Electron Microscopy (Cryo EM)