The anatomy of transcriptionally active chromatin loops in Drosophila primary spermatocytes using super-resolution microscopy.
The anatomy of transcriptionally active chromatin loops in Drosophila primary spermatocytes using super-resolution microscopy.
复制标题
DOI：
10.1371/journal.pgen.1010654
复制
发表时间：
2023-03
期刊：
影响因子：
4.5
通讯作者：
中科院分区：
文献类型：
--
作者：
虽然基因转录的生物化学已经得到了很好的研究，但我们对这一过程如何在完整的细胞核内以3D方式组织的理解还不太清楚。在这里，我们调查的结构，积极转录的染色质和建筑的相互作用与积极的RNA聚合酶。为了进行这项分析，我们使用超分辨率显微镜对果蝇Y环进行成像，这些Y环代表巨大的，几兆长的单个转录单位。Y环为转录活性染色质提供了一个特别适合的模型系统。我们发现，尽管这些转录的环是解密集的，但它们并没有组织成延伸的10 nm纤维，而是主要由核小体簇的链组成。每个团簇的平均宽度约为50nm。我们发现，活跃的RNA聚合酶的焦点通常位于核小体簇外围的主纤维轴之外。RNA聚合酶和新生转录物的焦点分布在Y环周围，而不是聚集在单个转录工厂中。然而，由于RNA聚合酶灶比核小体簇普遍得多，因此这种活性染色质组织成核小体簇链不太可能由转录Y环的聚合酶的活性决定。这些结果为理解染色质与基因转录过程的拓扑关系提供了基础。转录是一个高度调控的过程，能够在发育过程中产生不同的细胞类型，并能够响应外部信号改变基因表达。当转录调控出错时，它可能导致包括癌症在内的各种疾病状态。在真核生物中，转录作用于染色质，染色质是一种通过将DNA包装在组蛋白周围形成的重复核小体的聚合物。染色质组织与转录调控有关，因为它被认为控制转录机器对DNA的访问。然而，由于细胞核内的致密包装，直接成像染色质传统上是非常困难的。果蝇初级精母细胞有大的细胞核，在Y染色体上有很容易看到的转录活性区域，称为“Y环”。使用超分辨率成像的Y环，我们表明，这种活跃的染色质具有特定的组织作为一个链的核小体簇。我们还发现，积极延长RNA聚合酶是相当少的流行沿着环比集群。我们的结论是，活跃的染色质组织成核小体簇是不太可能引起的转录延长。这一发现是理解染色质结构和转录调控之间复杂拓扑关系的重要一步。
While the biochemistry of gene transcription has been well studied, our understanding of how this process is organised in 3D within the intact nucleus is less well understood. Here we investigate the structure of actively transcribed chromatin and the architecture of its interaction with active RNA polymerase. For this analysis, we have used super-resolution microscopy to image the Drosophila melanogaster Y loops which represent huge, several megabases long, single transcription units. The Y loops provide a particularly amenable model system for transcriptionally active chromatin. We find that, although these transcribed loops are decondensed they are not organised as extended 10nm fibres, but rather they largely consist of chains of nucleosome clusters. The average width of each cluster is around 50nm. We find that foci of active RNA polymerase are generally located off the main fibre axis on the periphery of the nucleosome clusters. Foci of RNA polymerase and nascent transcripts are distributed around the Y loops rather than being clustered in individual transcription factories. However, as the RNA polymerase foci are considerably less prevalent than the nucleosome clusters, the organisation of this active chromatin into chains of nucleosome clusters is unlikely to be determined by the activity of the polymerases transcribing the Y loops. These results provide a foundation for understanding the topological relationship between chromatin and the process of gene transcription. Transcription is a highly regulated process enabling the production of different cell types during development and the ability to change gene expression in response to external signals. When transcription regulation goes wrong it can lead to a variety of disease states including cancer. In eukaryotes, transcription operates on chromatin, a polymer of repeating nucleosomes formed by packaging DNA around histone proteins. Chromatin organisation is linked to transcription regulation, as it is thought to control the access of transcription machinery to the DNA. However, directly imaging chromatin within the nucleus is traditionally very difficult due to the dense packaging. Drosophila primary spermatocytes have large nuclei with easily visualised transcriptionally active regions of the Y chromosome known as ‘Y loops’. Using super-resolution imaging on Y loops, we show that this active chromatin has a specific organisation as a chain of nucleosome clusters. We also find that actively elongating RNA Polymerase is considerably less prevalent along the loops than the clusters. We conclude that the organisation of active chromatin into nucleosome clusters is unlikely to be caused by transcription elongation. This finding is an important step towards understanding the complex topological relationship between chromatin structure and regulation of transcription.
登录
查看更多内容
影响因子：
21.3
作者：
通讯作者：
--
影响因子：
1.6
作者：
HARDY, RW;TOKUYASU, KT;LINDSLEY, DL
通讯作者：
LINDSLEY, DL
影响因子：
14.9
作者：
Castells-Garcia A;Ed-Daoui I;González-Almela E;Vicario C;Ottestrom J;Lakadamyali M;Neguembor MV;Cosma MP
通讯作者：
Cosma MP
DOI：
10.1073/pnas.231484998
发表时间：
2001-11-06
影响因子：
11.1
作者：
Carvalho, AB;Dobo, BA;Clark, AG
通讯作者：
Clark, AG
DOI：
10.1109/34.1000236
发表时间：
2002-05-01
影响因子：
23.6
作者：
Comaniciu, D;Meer, P
通讯作者：
Meer, P