Histone H2A Ubiquitination Does Not Preclude Histone H1 Binding, but It Facilitates Its Association with the Nucleosome

Laure J.M. Jason,George Lindsey,Ron M. Finn,Juan Ausió

doi:10.1074/jbc.m410203200

Laure J.M. Jason, George Lindsey + Show 2 more

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https://doi.org/10.1074/jbc.m410203200

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Abstract

Histone H2A ubiquitination is a bulky posttranslational modification that occurs at the vicinity of the binding site for linker histones in the nucleosome. Therefore, we took several experimental approaches to investigate the role of ubiquitinated H2A (uH2A) in the binding of linker histones. Our results showed that uH2A was present in situ in histone H1-containing nucleosomes. Notably in vitro experiments using nucleosomes reconstituted onto 167-bp random sequence and 208-bp (5 S rRNA gene) DNA fragments showed that ubiquitination of H2A did not prevent binding of histone H1 but it rather enhanced the binding of this histone to the nucleosome. We also showed that ubiquitination of H2A did not affect the positioning of the histone octamer in the nucleosome in either the absence or the presence of linker histones.

Highlights

Despite the renewed interest in histone H2A/H2B ubiquitination [1,2,3], the functional role of uH2A1 still remains controversial
This structural similarity led to a model in which the primary binding site of linker histones to DNA is comprised of helix III of the globular domain binding to the major groove and binding of the ␤-hairpin to the adjacent minor groove [21, 23]
The DNA from the soluble fraction almost exclusively consisted of 146-bp DNA from nucleosome core particles. As it can be seen in this figure, when a Western blot analysis was performed on an equivalent amount of histones obtained from both the 0.1 M KCl-soluble and -insoluble fractions using a ubiquitin-specific antibody, the intensity of the signal corresponding to ubiquitinated H2A (uH2A) was the same in both fractions (Fig. 1C)

Summary

Introduction

Despite the renewed interest in histone H2A/H2B ubiquitination [1,2,3], the functional role of uH2A1 still remains controversial. The three-helix bundle structure of the globular domain of histone H5 has been reported to resemble that of the bacterial catabolite gene activator protein [22, 23] as well as that of the DNA recognition motif of hepatocyte nuclear factor-3 (HNF-3), a Drosophila transcription factor [22] This structural similarity led to a model in which the primary binding site of linker histones to DNA is comprised of helix III of the globular domain binding to the major groove and binding of the ␤-hairpin to the adjacent minor groove [21, 23]. The precise location of the globular domain on the vicinity of the pseudodyad axis is well established (for reviews, see Refs. 26 and 27)

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