Perry M, Chalkley R
J Biol Chem. 1982 Jul 10;257(13):7336-47.
The effect of histone acetylation on chromatin solubility has been studied. Nucleosome cores are fairly soluble over a range of Mg2+ and Na+ concentrations. Increasing the amount of Na+ relative to a fixed concentration of Mg2+ leads to increased solubility. Although the effect is not large, acetylated cores are more soluble than control cores, all other factors being equal. Acetylated oligonucleosomes are vastly more soluble than control oligonucleosomes with the greatest differential seen in the presence of Mg2+ at low ionic strengths. Solubility of acetylated oligonucleosomes is favored when the majority of the histones in the nucleosomes are all highly acetylated. Contiguous highly acetylated nucleosomes are enriched in the rapid kinetic form of histone acetylation after short term exposure to butyrate. These observations have been exploited in a fractionation scheme for chromatin based on the levels of hyperacetylation attained after varied times of exposure to sodium butyrate. Essentially all DNA sequences in an unsynchronized cell population are associated with rapidly acetylated histones. Since it is highly unlikely that each cell has its own discrete set of sequences bound to acetylated histone and since the amount of rapidly acetylated histone in a single cell is relatively small (approximately 10% of total histone), we surmise that rapid acetylation migrates throughout much of the chromatin, perhaps in a sequential and highly organized manner. We postulate that the biological role of histone acetylation is to provide a means for sequentially exposing the entire chromatin for surveillance for DNA damage and possibly for recognition of different regions of the DNA by specific (regulatory?) proteins.
组蛋白乙酰化对染色质溶解性的影响已得到研究。核小体核心在一定范围的Mg2+和Na+浓度下相当易溶。相对于固定浓度的Mg2+增加Na+的量会导致溶解性增加。尽管这种影响不大，但在所有其他因素相同的情况下，乙酰化的核心比对照核心更易溶。乙酰化的寡核小体比对照寡核小体的溶解性要高得多，在低离子强度下存在Mg2+时差异最为显著。当核小体中的大多数组蛋白都高度乙酰化时，乙酰化寡核小体的溶解性更有利。短期暴露于丁酸盐后，连续高度乙酰化的核小体富含组蛋白乙酰化的快速动力学形式。基于暴露于丁酸钠不同时间后达到的高乙酰化水平，这些观察结果已被用于染色质的分级分离方案中。在未同步化的细胞群体中，基本上所有的DNA序列都与快速乙酰化的组蛋白相关。由于每个细胞都有自己一套与乙酰化组蛋白结合的离散序列的可能性极小，而且单个细胞中快速乙酰化组蛋白的量相对较少（约占总组蛋白的10%），我们推测快速乙酰化在大部分染色质中迁移，可能是以一种有序且高度有组织的方式。我们假设组蛋白乙酰化的生物学作用是提供一种手段，用于依次暴露整个染色质以监测DNA损伤，并可能用于特定（调节？）蛋白识别DNA的不同区域。
