Dynamically Acetylated Histone Association with Transcriptionally Active and Competent Genes in the Avian Adult β-Globin Gene Domain

Virginia A Spencer,James R Davie

doi:10.1074/jbc.m104886200

Abstract

In chicken immature erythrocytes, class 1 acetylated histones are rapidly tri- and tetra-acetylated and rapidly deacetylated. Class 2 acetylated H3 and H4 are rapidly acetylated to mono- and di-acetylated isoforms and slowly deacetylated. Our previous studies suggested that class 1 acetylated histones were primarily associated with transcriptionally active DNA (beta(A)-globin) but not competent DNA (epsilon-globin). Chromatin salt solubility (chromatin fiber oligomerization) is directly influenced by hyperacetylation. In this study we investigated the association of class 1 histones with beta(A)- and epsilon-globin DNA by measuring their loss of solubility rates in 150 mm NaCl and 3 mm MgCl(2) as a function of hyperacetylated histone deacetylation. Expressed and competent chromatin was associated with class 1 acetylated histones. As most active chromatin and hyperacetylated histones are associated with the low salt-insoluble residual nuclear material containing the nuclear matrix, we investigated whether hyperacetylated histones are bound to the beta(A)- and epsilon-globin DNA in this fraction. In chromatin immunoprecipitation assays, we found that the beta(A)- and epsilon-globin coding regions are bound to hyperacetylated H3 and H4. Our observations are consistent with a model in which nuclear matrix-associated histone acetyltransferases and deacetylases mediate a dynamic attachment between active and competent chromatin and the nuclear matrix.

Highlights

Histone acetylation is a dynamic process catalyzed by histone acetyltransferases and histone deacetylases
As most active chromatin and hyperacetylated histones are associated with the low salt-insoluble residual nuclear material containing the nuclear matrix, we investigated whether hyperacetylated histones are bound to the ␤A- and ⑀-globin DNA in this fraction
Chromatin fractionation studies have shown that chicken immature erythrocyte chromatin fragments soluble in 3 mM MgCl2 or 0.15 M NaCl are enriched in transcriptionally active DNA sequences and class 1, dynamically hyperacetylated histones [5, 6]

Summary

Introduction

Histone acetylation is a dynamic process catalyzed by histone acetyltransferases and histone deacetylases. Chromatin fractionation studies have shown that chicken immature erythrocyte chromatin fragments soluble in 3 mM MgCl2 or 0.15 M NaCl are enriched in transcriptionally active DNA sequences and class 1, dynamically hyperacetylated histones [5, 6]. The level of histone acetylation was shown to be the primary determinant for the resistance of transcriptionally active/competent DNA fragments to H1-induced salt precipitation In support of these findings, the treatment of mouse fibroblast cells with trichostatin A, a histone deacetylase inhibitor, induces histone hyperacetylation and increases the rate of exchange of a mobile fraction of H1 [8]. This study analyzed only the steady state levels of acetylated core histones along ␤-globin domain DNA sequences in soluble chromatin fragments; low salt-insoluble chromatin fragments, which contain most of the dynamically acetylated histones and transcriptionally active ␤-globin DNA sequences, were excluded from analysis. The antibody used to map the distribution of acetylated histones recognized acetylated histone and acetylated non-histone chromosomal proteins [13]

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Results

Conclusion