Jeppesen P
MRC Human Genetics Unit, Western General Hospital, Edinburgh, Scotland, UK.
Bioessays. 1997 Jan;19(1):67-74. doi: 10.1002/bies.950190111.
Immunofluorescent labelling demonstrates that human metaphase chromosomes contain hyperacetylated histone H4. With the exception of the inactive X chromosome in female cells, where the bulk of histone H4 is underacetylated, H4 hyperacetylation is non-uniformly distributed along the chromosomes and clustered in cytologically resolvable chromatin domains that correspond, in general, with the R-bands of conventional staining. The strongest immunolabelling is often found in T-bands, the subset of intense R-bands having the highest GC content. The majority of mapped genes also occurs in R-band regions, with the highest gene density in T-bands. These observations are consistent with a model in which hyperacetylation of histone H4 marks the position of potentially active gene sequences on metaphase chromosomes. Since acetylation is maintained during mitosis, progeny cells receive an imprint of the histone H4 acetylation pattern that was present on the parental chromosomes before cell division. Histone acetylation could provide a mechanism for propagating cell memory, defined as the maintenance of committed states of gene expression through cell lineages.
免疫荧光标记显示人类中期染色体含有高度乙酰化的组蛋白H4。除了女性细胞中的失活X染色体（其中大部分组蛋白H4处于低乙酰化状态）外，H4的高度乙酰化沿染色体分布不均，并聚集在细胞学上可分辨的染色质结构域中，这些结构域通常与传统染色的R带相对应。最强的免疫标记通常见于T带，这是具有最高GC含量的强烈R带的一个子集。大多数已定位的基因也出现在R带区域，T带中的基因密度最高。这些观察结果与一个模型一致，在该模型中，组蛋白H4的高度乙酰化标记了中期染色体上潜在活跃基因序列的位置。由于乙酰化在有丝分裂期间得以维持，子细胞接收了细胞分裂前亲代染色体上存在的组蛋白H4乙酰化模式的印记。组蛋白乙酰化可为传播细胞记忆提供一种机制，细胞记忆定义为通过细胞谱系维持基因表达的特定状态。
