Hochstrasser M, Sedat J W
J Cell Biol. 1987 Jun;104(6):1471-83. doi: 10.1083/jcb.104.6.1471.
In the preceding article we compared the general organization of polytene chromosomes in four different Drosophila melanogaster cell types. Here we describe experiments aimed at testing for a potential role of three-dimensional chromosome folding and positioning in modulating gene expression and examining specific chromosome interactions with different nuclear structures. By charting the configurations of salivary gland chromosomes as the cells undergo functional changes, it is shown that loci are not repositioned within the nucleus when the pattern of transcription changes. Heterologous loci show no evidence of specific physical interactions with one another in any of the cell types. However, a specific subset of chromosomal loci is attached to the nuclear envelope, and this subset is extremely similar in at least two tissues. In contrast, no specific interactions between any locus and the nucleolus are found, but the base of the X chromosome, containing the nucleolar organizer, is closely linked to this organelle. These results are used to evaluate models of gene regulation that involve the specific intranuclear positioning of gene sequences. Finally, data are presented on an unusual class of nuclear envelope structures, filled with large, electron-dense particles, that are usually associated with chromosomes.
在上一篇文章中，我们比较了四种不同果蝇细胞类型中多线染色体的总体结构。在此，我们描述了旨在测试三维染色体折叠和定位在调节基因表达中的潜在作用，以及研究特定染色体与不同核结构相互作用的实验。通过绘制唾液腺染色体在细胞发生功能变化时的构型，结果表明当转录模式改变时，基因座在细胞核内不会重新定位。在任何细胞类型中，异源基因座之间均未显示出特异性物理相互作用的证据。然而，染色体基因座的一个特定子集附着于核膜，并且该子集在至少两种组织中极为相似。相比之下，未发现任何基因座与核仁之间存在特异性相互作用，但含有核仁组织区的X染色体基部与该细胞器紧密相连。这些结果用于评估涉及基因序列在细胞核内特定定位的基因调控模型。最后，展示了一类不同寻常的核膜结构的数据，这些结构充满了通常与染色体相关的大的、电子致密颗粒。
