Hennig W
Department of Physiological Chemistry and Pathobiochemistry, Johannes Gutenberg University Mainz, Duesbergweg 6, D-55099 Mainz, Germany.
Chromosoma. 1999 Apr;108(1):1-9. doi: 10.1007/s004120050346.
The properties of heterochromatin are reconsidered in the context of our present understanding of gene silencing, telomeric and centromeric properties, position-effect variegation and X-chromosome inactivation. It is proposed that the chromatin in heterochromatic chromosomal regions is generally similar in its molecular composition to that in silenced chromosomal regions. Heterochromatic appearance hence reflects not a particular quality of the respective chromosomal regions but only a specific kind of chromatin packaging comparable to that required for the inactivation of genes. This packaging may be initiated by particular signals in the DNA but can be propagated over more extended chromosomal regions by the formation of multiprotein complexes that interact with histones and possibly cell-specific additional components (RNA or proteins) that determine the status of the chromosome in a particular cell type.
在我们目前对基因沉默、端粒和着丝粒特性、位置效应斑驳以及X染色体失活的理解背景下，对异染色质的特性进行了重新审视。有人提出，异染色质染色体区域中的染色质在分子组成上通常与沉默染色体区域中的染色质相似。因此，异染色质外观并非反映相应染色体区域的特定性质，而仅仅反映一种特定类型的染色质包装，类似于基因失活所需的包装。这种包装可能由DNA中的特定信号启动，但可以通过与组蛋白相互作用的多蛋白复合物的形成，以及可能与决定特定细胞类型中染色体状态的细胞特异性额外成分（RNA或蛋白质）的相互作用，在更广泛的染色体区域中传播。
