Dissecting Mammalian Replication-Independent Chromatin Assembly — Biochemical and Structural Studies on the H3.3-Specific Histone Chaperones Hira and Daxx
type: CreativeWork
description: Histones are architectural proteins that wrap approximately two turns of DNA around their octameric core structure, constituting the fundamental packaging unit of eukaryotic chromatin — the nucleosome. Beyond their structural role, they regulate virtually all processes that act on or depend on DNA, such as replication, gene expression and maintenance of centromeres and telomeres. Despite the high conservation of the four core histones, H3, H4, H2A and H2B, throughout all eukaryotes, histone variants have emerged with variable degree of divergence from their canonical counterparts. These variants are thought to expand the regulatory repertoire of chromatin. The histone replacement variant H3.3 is implicated in the formation and maintenance of specialized chromatin structure in metazoan cells. H3.3-containing nucleosomes are assembled in a replication-independent manner by means of dedicated histone chaperone proteins. By purifying H3.3-containing nuclear complexes from HeLa cells, I have identified proteins that mediate this replicationindependent deposition of H3.3. I have been able to single out the death-associated protein Daxx as an bona fide histone H3.3 chaperone. Furthermore, I show that Daxx cooperates with an ATP-dependent chromatin remodeler, ATRX, in depositing histone H3.3 at telomeres in vivo (Chapter 2). I show that an evolutionary conserved histone binding domain of Daxx interacts directly with variant-specific residues of the H3.3 core. I further identify homologies with the centromere-specific histone chaperone HJURP that hint to a conserved mechanism used across replicationindependent chromatin assembly pathways (Chapter 3). I report crystallization of a complex of the Daxx histone binding domain and histones H3.3-H4 with the aim of solving the cocrystal structure to reveal how Daxx can tell the subtle differences in H3 variants apart. (Chapter 4). Through a more detailed biochemical fractionation and genetic analysis, I found that Daxx constitutes …
abstract: Histones are architectural proteins that wrap approximately two turns of DNA around their octameric core structure, constituting the fundamental packaging unit of eukaryotic chromatin — the nucleosome. Beyond their structural role, they regulate virtually all processes that act on or depend on DNA, such as replication, gene expression and maintenance of centromeres and telomeres. Despite the high conservation of the four core histones, H3, H4, H2A and H2B, throughout all eukaryotes, histone variants have emerged with variable degree of divergence from their canonical counterparts. These variants are thought to expand the regulatory repertoire of chromatin. The histone replacement variant H3.3 is implicated in the formation and maintenance of specialized chromatin structure in metazoan cells. H3.3-containing nucleosomes are assembled in a replication-independent manner by means of dedicated histone chaperone proteins. By purifying H3.3-containing nuclear complexes from HeLa cells, I have identified proteins that mediate this replicationindependent deposition of H3.3. I have been able to single out the death-associated protein Daxx as an bona fide histone H3.3 chaperone. Furthermore, I show that Daxx cooperates with an ATP-dependent chromatin remodeler, ATRX, in depositing histone H3.3 at telomeres in vivo (Chapter 2). I show that an evolutionary conserved histone binding domain of Daxx interacts directly with variant-specific residues of the H3.3 core. I further identify homologies with the centromere-specific histone chaperone HJURP that hint to a conserved mechanism used across replicationindependent chromatin assembly pathways (Chapter 3). I report crystallization of a complex of the Daxx histone binding domain and histones H3.3-H4 with the aim of solving the cocrystal structure to reveal how Daxx can tell the subtle differences in H3 variants apart. (Chapter 4). Through a more detailed biochemical fractionation and genetic analysis, I found that Daxx constitutes …
author: Elsässer, Simon
keywords: histone H3 variants, H3.3, histone chaperones, chromatin, Daxx protein, ATRX (ATP-dependent chromatin remodeler, Life Sciences
date published: 2012-01-01T08:00:00Z
date modified: 2026-07-24T04:11:51Z
provider: Rockefeller
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Rockefeller