Structural basis of instability of the nucleosome containing a testis-specific histone variant, human H3T

Abstract

A histone H3 variant, H3T, is highly expressed in the testis, suggesting that it may play an important role in the chromatin reorganization required for meiosis and/or spermatogenesis. In the present study, we found that the nucleosome containing human H3T is significantly unstable both in vitro and in vivo, as compared to the conventional nucleosome containing H3.1. The crystal structure of the H3T nucleosome revealed structural differences in the H3T regions on both ends of the central α2 helix, as compared to those of H3.1. The H3T-specific residues (Met71 and Val111) are the source of the structural differences observed between H3T and H3.1. A mutational analysis revealed that these residues are responsible for the reduced stability of the H3T-containing nucleosome. These physical and structural properties of the H3T-containing nucleosome may provide the basis of chromatin reorganization during spermatogenesis.

Structure of the CENP-A nucleosome and its implications for centromeric chromatin architecture

“…1), as in the canonical human H3 nucleosomes (Tsunaka et al, 2005;Tachiwana et al, 2010Tachiwana et al, , 2011bIwasaki et al, 2011). This is consistent with the octasome model for the CENP-A nucleosome.…”

Structure of human nucleosome containing the testis-specific histone variant TSH2B

“…After the sample was dialyzed against 10 mM Tris-HCl buffer (pH 7.5) containing 1 mM EDTA, 2 M KCl, 1 mM DTT, and the KCl concentration was gradually decreased to 0.25 M during dialysis. The 146 base-pair DNA was derived from a palindromic human -satellite DNA fragment (Luger et al, 1997), which was previously used for structural studies of human nucleosomes containing canonical histone H2B (Tsunaka et al, 2005;Tachiwana et al, 2010Tachiwana et al, , 2011. To remove the nonspecific histone-DNA aggregates, the samples were incubated at 328 K for 2 h. The TSH2B nucleosome was further purified by nondenaturing polyacrylamide gel electrophoresis using a Prep Cell apparatus (Bio-Rad) (Figs.…”

“…The structure of the TSH2B nucleosome was determined by molecular replacement with Phaser ( A close-up view of the structure around amino-acid residue Ser85 in TSH2B. (a) A close-up view around the canonical H2B Asn84 residue, which corresponds to the TSH2B Ser85 residue in the nucleosome (PDB entry 3afa; Tachiwana et al, 2010). The H2B and H4 molecules are coloured yellow and pale cyan, respectively, and the side chains around the H2B Asn84 and H4 Arg78 residues are shown.…”

“…2007), using the coordinates of the human nucleosome structure (Tachiwana et al, 2010; PDB entry 3afa) as the search model. All refinements were performed using CNS (Brü nger et al, 1998).…”

Feux croisés sur le nucléosome

“…Malgré la description détaillée des étapes qui mènent au remplacement des histones et à l'invalidation des gènes codant pour les PT et les H2AL1/2 chez l'homme est l'histone connue sous le nom de H2A.bbd, qui, elle aussi, peut induire une instabilité du nucléosome [10]. Chez les mammifères, il existe également un variant de H3 -connu sous le nom de tH3 (H3.1t) -dont le profil d'expression est restreint à la lignée germinale mâle, et qui est capable d'induire une instabilité du nucléosome lorsqu'il remplace H3 [11]. Malheureusement, du fait de l'absence d'anticorps spécifique, le profil d'expression spatiotemporel de ce variant d'H3 au cours de la spermatogenèse n'est pas connu.…”