Replication-independent histone deposition by the HIR complex and Asf1
Program in Gene Function and Expression
Medical Subject Headings
Cell Cycle Proteins; Chromatin Assembly Factor-1; Chromatin Immunoprecipitation; Chromosomal Proteins, Non-Histone; DNA; DNA-Binding Proteins; Electrophoretic Mobility Shift Assay; Histones; Immunoblotting; Mass Spectrometry; Molecular Chaperones; Multiprotein Complexes; Mutation; Nuclear Proteins; Repressor Proteins; Saccharomyces cerevisiae Proteins; Yeasts
Genetics and Genomics
The orderly deposition of histones onto DNA is mediated by conserved assembly complexes, including chromatin assembly factor-1 (CAF-1) and the Hir proteins . CAF-1 and the Hir proteins operate in distinct but functionally overlapping histone deposition pathways in vivo . The Hir proteins and CAF-1 share a common partner, the highly conserved histone H3/H4 binding protein Asf1, which binds the middle subunit of CAF-1 as well as to Hir proteins . Asf1 binds to newly synthesized histones H3/H4 , and this complex stimulates histone deposition by CAF-1 . In yeast, Asf1 is required for the contribution of the Hir proteins to gene silencing . Here, we demonstrate that Hir1, Hir2, Hir3, and Hpc2 comprise the HIR complex, which copurifies with the histone deposition protein Asf1. Together, the HIR complex and Asf1 deposit histones onto DNA in a replication-independent manner. Histone deposition by the HIR complex and Asf1 is impaired by a mutation in Asf1 that inhibits HIR binding. These data indicate that the HIR complex and Asf1 proteins function together as a conserved eukaryotic pathway for histone replacement throughout the cell cycle.
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Citation: Curr Biol. 2005 Nov 22;15(22):2044-9. Link to article on publisher's site