Abstract
Centromeric nucleosomes are composed of the centromere-specific histone H3 variant CENP-A and the core histones H2A, H2B, and H4. To establish a functional kinetochore, histone H4 lysine-20 (H4K20) must be monomethylated, but the underlying mechanism has remained enigmatic. To provide structural insights into H4K20 methylation, we here solve the crystal structure of a nucleosome containing an H3.1-CENP-A chimera, H3.1CATD, which has a CENP-A centromere targeting domain and preserves essential CENP-A functions in vivo. Compared to the canonical H3.1 nucleosome, the H3.1CATD nucleosome exhibits conformational changes in the H4 N-terminal tail leading to a relocation of H4K20. In particular, the H4 N-terminal tail interacts with glutamine-76 and aspartate-77 of canonical H3.1 while these interactions are cancelled in the presence of the CENP-A-specific residues valine-76 and lysine-77. Mutations of valine-76 and lysine-77 impair H4K20 monomethylation both in vitro and in vivo. These findings suggest that a CENP-A-mediated structural polymorphism may explain the preferential H4K20 monomethylation in centromeric nucleosomes.
Highlights
Centromeric nucleosomes are composed of the centromere-specific histone H3 variant CENP-A and the core histones H2A, H2B, and H4
We found that the orientation of the H4 N-terminal tail in the H3.1CATD nucleosome was substantially different from that observed in the canonical H3.1 nucleosome (Fig. 1d, Supplementary Figures 1, 2, and 3)
We named the H4 N-terminal tail conformation found in the H3.1CATD nucleosome as the outward H4-N conformation, and that observed in the H3.1 nucleosome as the inward H4-N conformation (Fig. 1d)
Summary
Centromeric nucleosomes are composed of the centromere-specific histone H3 variant CENP-A and the core histones H2A, H2B, and H4. Mutations of valine-76 and lysine-77 impair H4K20 monomethylation both in vitro and in vivo These findings suggest that a CENP-A-mediated structural polymorphism may explain the preferential H4K20 monomethylation in centromeric nucleosomes. Correct centromere formation and inheritance are crucial for accurate chromosome segregation For these processes, the centromere must be formed in the specific region on a chromosome. CENP-A forms the octameric nucleosome with the core histones H2A, H2B, and H4, as revealed by the crystal structure[12], and creates a foundation to establish centromeric chromatin with the coordination of additional centromere proteins, such as CENP-C4,13–16, CENP-N13,17–20, and the Mis[18] complex[21,22]. Set[7], may associate with centromere proteins, but we did not observe the clear centromere localization of PR-Set[728] As another possibility, in the CENP-A nucleosome, the H4
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
