Relationship between Methylation and Acetylation of Arginine-Rich Histones in Cycling and Arrested HeLa Cells

Abstract

In the following report the relationship between histone methylation and histone acetylation has been examined in HeLa cells to better define the distribution of these two modifications. By labeling methylated histones in the presence or absence of sodium butyrate, we have found that the methylation of H3 is much more targeted to rapidly acetylated chromatin than is the methylation of H4, which largely involves the unacetylated subtype even in the presence of butyrate. Newly methylated H3 is highly likely to be complexed in nucleosomes that contain acetylated H4, as determined by immunoprecipitating radiolabeled chromatin with antibodies specific for acetylated H4 isoforms. In contrast, dynamically methylated H4 is underrepresented in acetylated chromatin, relative to newly methylated H3. The preferential methylation of acetylated H3 continues after pretreatment of cells with cycloheximide, indicating that not all acetylation-related methylation is associated with histone synthesis. This was confirmed by analyzing histone methylation in cells arrested at the G1/S boundary, in which histone synthesis was sharply lowered (relative to randomly cycling cells): under these conditions H3 methylation declined only approximately 4-fold, although ongoing methylation of H4 decreased approximately 20-fold. The continuing methylation of H3 in arrested cells included all H3 sequence variants, was selective for acetylated H3, and coincided with methyl group turnover that could not be ascribed to histone replacement synthesis. Most newly methylated H3 in arrested cells was complexed with acetylated H4 in chromatin.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamic acetylation of all lysine-4 trimethylated histone H3 is evolutionarily conserved and mediated by p300/CBP

“…5). However, radiolabeling studies (6,7) and genetic experiments in yeast (8,9) show acetylation is highly dynamic and heterogeneous, with different populations of histones characterized by distinct rates of acetylation and deacetylation (5,10). We have shown that all detectable K4-trimethylated histone H3 (H3K4me3) across murine nuclei, irrespective of location or association, is subject to dynamic acetylation at multiple lysine residues, becoming maximally acetylated within 10-30 min of treatment with trichostatin A (TSA) (11).…”

Catalytic Function of the PR-Set7 Histone H4 Lysine 20 Monomethyltransferase Is Essential for Mitotic Entry and Genomic Stability

“…One of the first histone modifications to be identified nearly forty-five years ago was the methylation of histone H4 lysine 20 (H4K20) 4 (2). Earlier biochemical studies linked H4K20 methylation to diverse biological events including transcriptional regulation, chromatin compaction, cell division, and the formation of heterochromatin (3)(4)(5)(6)(7)(8)(9). Importantly, it was also found that H4K20 is differentially methylated in vivo and therefore can be either mono-, di-, or trimethylated (10).…”

Structure et dynamique de la particule cœur de nucléosome

“…Par exemple, l'acétylation de la lysine 16 de H4 en concomitance avec la phosphorylation de la sérine 10 de H3 amplifie l'activité transcriptionnelle du chromosome X masculin [17]. De même, H3 et H4 sont des cibles privilégiées pour la méthylation lorsqu'elles sont acétylées [22]. Enfin, des modifications post-traductionnelles de même nature peuvent entraîner des effets opposés.…”

“…Des études récentes montrent que la structure des NCP n'est pas figée et qu'il est possible d'observer, notamment in vitro, des mouvements rapides d'ouverture et de fermeture de L'ADN nucléosomal par FRET (fluorescence resonance energy transfer) ou FCS (fluorescence correlation spectroscopy) [20][21][22]. Les nucléosomes restent bien enroulés pendant 250 ms puis l'ADN s'ouvre pendant des intervalles de temps variant de 10 à 50 ms, assez longs pour rendre l'ADN accessible à des protéines et à des enzymes [24].…”