SNAP output for PDB entry 6l49 [SNAP web server]

PDB-id

6l49; SNAP-derived features in text and JSON formats; DNAproDB

Class

nuclear protein

Method

cryo-EM (18.9 Å)

Summary

H3-ca-h3 tri-nucleosome with the 22 base-pair linker DNA

Reference

Takizawa Y, Ho CH, Tachiwana H, Matsunami H, Kobayashi W, Suzuki M, Arimura Y, Hori T, Fukagawa T, Ohi MD, Wolf M, Kurumizaka H (2020): "Cryo-EM Structures of Centromeric Tri-nucleosomes Containing a Central CENP-A Nucleosome." Structure, 28, 44. doi: 10.1016/j.str.2019.10.016.

Abstract

The histone H3 variant CENP-A is a crucial epigenetic marker for centromere specification. CENP-A forms a characteristic nucleosome and dictates the higher-order configuration of centromeric chromatin. However, little is known about how the CENP-A nucleosome affects the architecture of centromeric chromatin. In this study, we reconstituted tri-nucleosomes mimicking a centromeric nucleosome arrangement containing the CENP-A nucleosome, and determined their 3D structures by cryoelectron microscopy. The H3-CENP-A-H3 tri-nucleosomes adopt an untwisted architecture, with an outward-facing linker DNA path between nucleosomes. This is distinct from the H3-H3-H3 tri-nucleosome architecture, with an inward-facing DNA path. Intriguingly, the untwisted architecture may allow the CENP-A nucleosome to be exposed to the solvent in the condensed chromatin model. These results provide a structural basis for understanding the 3D configuration of CENP-A-containing chromatin, and may explain how centromeric proteins can specifically target the CENP-A nucleosomes buried in robust amounts of H3 nucleosomes in centromeres.