title: Promiscuous Histone Mis-Assembly Is Actively Prevented by Chaperones.
abstract: Histone proteins are essential for the organization, expression, and inheritance of genetic material for eukaryotic cells. A centromere-specific H3 histone variant, centromere protein A (CENP-A), shares about 50% amino acid sequence identity with H3. CENP-A is required for packaging the centromere and for the proper separation of chromosomes during mitosis. Despite their distinct biological functions, previously reported crystal structures of the CENP-A/H4 and H3/H4 dimers reveal a high degree of similarity. In this work, we characterize the structural dynamics of CENP-A/H4 and H3/H4 dimers based on a dual-resolution approach, using both microsecond-scale explicit-solvent all-atom and coarse-grained (CG) molecular dynamics (MD) simulations. Our data show that the H4 histone is significantly more rigid compared with the H3 histone and its variant CENP-A, hence, serving as a reinforcing structural element within the histone core. We report that the CENP-A/H4 dimer is significantly more dynamic than its canonical counterpart H3/H4, and our results provide a physical explanation for this flexibility. Further, we observe that the centromere-specific chaperone Holliday Junction Recognition Protein (HJURP) stabilizes the CENP-A/H4 dimer by forming a specific electrostatic interaction network. Finally, replacing CENP-A S68 with E68 disrupts the binding interface between CENP-A and HJURP in all-atom MD simulation, and consistently, in vivo experiments demonstrate that replacing CENP-A S68 with E68 disrupts CENP-A's localization to the centromere. Based on all our results, we propose that, during the CENP-A/H4 deposition process, the chaperone HJURP protects various substructures of the dimer, serving both as a folding and binding chaperone.
authors.affiliation: Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States.
authors.forename: Haiqing
authors.initials: H
authors.lastname: Zhao
authors.forename: David
authors.initials: D
authors.lastname: Winogradoff
authors.affiliation: Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States.
authors.forename: Minh
authors.initials: M
authors.lastname: Bui
authors.affiliation: Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States.
authors.forename: Yamini
authors.initials: Y
authors.lastname: Dalal
authors.forename: Garegin A
authors.initials: GA
authors.lastname: Papoian
mesh_terms: D000076247:Centromere Protein A / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006657:Histones / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D056004:Molecular Dynamics Simulation; D017510:Protein Folding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D013379:Substrate Specificity
chemical_list: D000076247:Centromere Protein A; D004268:DNA-Binding Proteins; C524371:HJURP protein, human; D006657:Histones