DAXX envelops an H3.3-H4 dimer for H3.3-specific recognition
ABSTRACT Histone chaperones represent a structurally and functionally diverse family of histone-binding proteins that prevent promiscuous interactions of histones before their assembly into chromatin. DAXX is a metazoan histone chaperone specific to the evolutionarily conserved histone variant H3.3. Here we report the crystal structures of the DAXX histone-binding domain with a histone H3.3-H4 dimer, including mutants within DAXX and H3.3, together with in vitro and in vivo functional studies that elucidate the principles underlying H3.3 recognition specificity. Occupying 40% of the histone surface-accessible area, DAXX wraps around the H3.3-H4 dimer, with complex formation accompanied by structural transitions in the H3.3-H4 histone fold. DAXX uses an extended α-helical conformation to compete with major inter-histone, DNA and ASF1 interaction sites. Our structural studies identify recognition elements that read out H3.3-specific residues, and functional studies address the contributions of Gly 90 in H3.3 and Glu 225 in DAXX to chaperone-mediated H3.3 variant recognition specificity.
- SourceAvailable from: Jingjun Hong
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- "Swr1 Is a Chaperone for the H2A.Z-H2B Dimer 2008], Scm3 [Zhou et al., 2011], Daxx [Elsä sser et al., 2012; Liu et al., 2012], HJURP [Hu et al., 2011], and FACT [Hondele et al., 2013]). Using a previous assay for chaperone function of FACT on H2A-H2B (Hondele et al., 2013), we performed gel-shift experiments in order to examine the chaperone function of the Swr1-Z domain. "
ABSTRACT: Histone variant H2A.Z-containing nucleosomes exist at most eukaryotic promoters and play important roles in gene transcription and genome stability. The multisubunit nucleosome-remodeling enzyme complex SWR1, conserved from yeast to mammals, catalyzes the ATP-dependent replacement of histone H2A in canonical nucleosomes with H2A.Z. How SWR1 catalyzes the replacement reaction is largely unknown. Here, we determined the crystal structure of the N-terminal region (599-627) of the catalytic subunit Swr1, termed Swr1-Z domain, in complex with the H2A.Z-H2B dimer at 1.78 Å resolution. The Swr1-Z domain forms a 310 helix and an irregular chain. A conserved LxxLF motif in the Swr1-Z 310 helix specifically recognizes the αC helix of H2A.Z. Our results show that the Swr1-Z domain can deliver the H2A.Z-H2B dimer to the DNA-(H3-H4)2 tetrasome to form the nucleosome by a histone chaperone mechanism.Molecular cell 02/2014; 53(3):498-505. DOI:10.1016/j.molcel.2014.01.010 · 14.46 Impact Factor
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- "Through its association with (H3–H4) dimers (Elsasser et al. 2012) and disruption of (H3–H4) 2 tetramers in vitro (English et al. 2005; Natsume et al. 2007), ASF1A may facilitate the formation of (H3.3–H4) dimers that can be recruited by DAXX. This scenario is compatible with the H3.3 binding motifs for ASF1A and DAXX being distinct (English et al. 2005; Natsume et al. 2007) and with the exclusive association of (H3.3–H4) with ASF1 or DAXX recently explained by crystallography studies (Elsasser et al. 2012). ASF1A is not found in the same H3.3-containing "
ABSTRACT: Replication-independent chromatin deposition of histone variant H3.3 is mediated by several chaperones. We report a multi-step targeting of newly synthesized epitope-tagged H3.3 to chromatin via PML bodies. H3.3 is recruited to PML bodies in a DAXX--dependent manner, a process facilitated by ASF1A. DAXX is required for enrichment of ATRX, but not ASF1A or HIRA, with PML. Nonetheless, the chaperones co-localize with H3.3 at PML bodies and are found in one or more complexes with PML. Both DAXX and PML are necessary to prevent accumulation of a soluble, non-incorporated, pool of H3.3. H3.3 targeting to PML is enhanced with an (H3.3-H4)2 tetramerization mutant of H3.3, suggesting H3.3 recruitment to PML as an (H3.3-H4) dimer rather than as a tetramer. Our data support a model of DAXX-mediated recruitment of (H3.3-H4) dimers to PML bodies, which may function as triage centers for H3.3 deposition into chromatin by distinct chaperones.Genome Research 12/2012; 23(3). DOI:10.1101/gr.142703.112 · 13.85 Impact Factor
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ABSTRACT: The SWI/SNF-like chromatin remodeler ATRX has recently garnered renewed attention. ATRX mutations were first identified in patients bearing the syndrome after which it is named, alpha thalassemia/mental retardation, X-linked. While ATRX has long been implicated in transcriptional regulation through multiple mechanisms, recent studies have identified a role for ATRX in the regulation of histone variant deposition. In addition, current reports describe ATRX to be mutated at high percentages in multiple tumor types, suggestive of a potential 'driver' role in cancer. Here we discuss the numerous and seemingly diverse roles for ATRX in transcriptional regulation and histone deposition and suggest that ATRX's effects are mediated by its regulation of histones within the chromatin template.Epigenetics: official journal of the DNA Methylation Society 12/2012; 8(1). DOI:10.4161/epi.23271 · 5.11 Impact Factor