Interphase nuclear architecture is disrupted and rapidly reformed with each cell division cycle. Successive cell generations exhibit a "memory" of this nuclear architecture, as well as for gene expression. Furthermore, many features of nuclear and mitotic chromosome structure are recognizably species and tissue specific. We wish to know what properties of the underlying chromatin structure may determine these conserved features of nuclear architecture. Employing a particular mouse autoimmune anti-nucleosome monoclonal antibody (PL2-6), combined with deconvolution immunofluorescence microscopy, we present evidence for a unique epitope (involving a ternary complex of histones H2A and H2B and DNA) which is localized only at the exterior chromatin surface of interphase nuclei and mitotic chromosomes in mammalian, invertebrate and plant systems. As only the surface chromatin region is identified with antibody PL2-6, we have assigned it the name "epichromatin". We describe an "epichromatin hypothesis", suggesting that epichromatin may have a unique evolutionary conserved conformation which facilitates interaction with the reforming post-mitotic nuclear envelope and a rapid return of interphase nuclear architecture.

中文翻译：

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表染色质表位：细胞周期的持久性和进化的保守性。

随着每个细胞分裂周期，相间核结构被破坏并迅速重组。连续的细胞世代表现出对这种核结构以及基因表达的“记忆”。此外，核和有丝分裂染色体结构的许多特征是可识别的物种和组织特异性。我们想知道潜在染色质结构的哪些特性可能决定核结构的这些保守特征。采用特定的小鼠自身免疫性抗核小体单克隆抗体 (PL2-6)，结合去卷积免疫荧光显微镜，我们提供了一个独特表位（涉及组蛋白 H2A 和 H2B 和 DNA 的三元复合物）的证据，该表位仅位于外部染色质哺乳动物间期细胞核和有丝分裂染色体的表面，无脊椎动物和植物系统。由于只有表面染色质区域被抗体 PL2-6 识别，我们将其命名为“表染色质”。我们描述了一个“表染色质假说”，表明表染色质可能具有独特的进化保守构象，这有助于与有丝分裂后核膜的改革和间期核结构的快速恢复相互作用。