7YBF

Crystal structure of inner membrane protein Sad1 in complex with histone H2A-H2B

Summary for 7YBF

• Entry DOI: 10.2210/pdb7ybf/pdb
• Descriptor: Histone H2B-alpha,Histone H2A-beta, Spindle pole body-associated protein sad1 (3 entities in total)
• Functional Keywords: heterochromatin, histone chaperone, histone, phase separation, membrane protein
• Biological source: Schizosaccharomyces pombe (fission yeast); More
• Total number of polymer chains: 3
• Total formula weight: 43442.32

Authors

Sun, W.,Hu, C.,Chen, Y. (deposition date: 2022-06-29, release date: 2024-01-03, Last modification date: 2026-03-04)

Primary citation

Sun, W.,Dong, Q.,Li, X.,Gao, J.,Ye, X.,Hu, C.,Li, F.,Chen, Y.
The SUN-family protein Sad1 mediates heterochromatin spatial organization through interaction with histone H2A-H2B.
Nat Commun, 15:4322-4322, 2024

PubMed Abstract: Heterochromatin is generally associated with the nuclear periphery, but how the spatial organization of heterochromatin is regulated to ensure epigenetic silencing remains unclear. Here we found that Sad1, an inner nuclear membrane SUN-family protein in fission yeast, interacts with histone H2A-H2B but not H3-H4. We solved the crystal structure of the histone binding motif (HBM) of Sad1 in complex with H2A-H2B, revealing the intimate contacts between Sad1 and H2A-H2B. Structure-based mutagenesis studies revealed that the H2A-H2B-binding activity of Sad1 is required for the dynamic distribution of Sad1 throughout the nuclear envelope (NE). The Sad1-H2A-H2B complex mediates tethering telomeres and the mating-type locus to the NE. This complex is also important for heterochromatin silencing. Mechanistically, H2A-H2B enhances the interaction between Sad1 and HDACs, including Clr3 and Sir2, to maintain epigenetic identity of heterochromatin. Interestingly, our results suggest that Sad1 exhibits the histone-enhanced liquid-liquid phase separation property, which helps recruit heterochromatin factors to the NE. Our results uncover an unexpected role of SUN-family proteins in heterochromatin regulation and suggest a nucleosome-independent role of H2A-H2B in regulating Sad1's functionality.

PubMed: 38773107
DOI: 10.1038/s41467-024-48418-7

Experimental method

X-RAY DIFFRACTION (2.15 Å)