Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
Genetics. 2018 Nov;210(3):869-881. doi: 10.1534/genetics.118.301349. Epub 2018 Sep 20.
The FACT (FAcilitates Chromatin Transactions) complex is a conserved complex that maintains chromatin structure on transcriptionally active genes. Consistent with this, FACT is enriched on highly expressed genes, but how it is targeted to these regions is unknown. , FACT binds destabilized nucleosomes, supporting the hypothesis that FACT is targeted to transcribed chromatin through recognition of RNA polymerase (RNAP)-disrupted nucleosomes. In this study, we used high-resolution analysis of FACT occupancy in to test this hypothesis. We demonstrate that FACT interacts with nucleosomes and that its interaction with chromatin is dependent on transcription by any of the three RNAPs. Deep sequencing of micrococcal nuclease-resistant fragments shows that FACT-bound nucleosomes exhibit differing nuclease sensitivity compared to bulk chromatin, consistent with a modified nucleosome structure being the preferred ligand for this complex. Interestingly, a subset of FACT-bound nucleosomes may be "overlapping dinucleosomes," in which one histone octamer invades the ∼147-bp territory normally occupied by the adjacent nucleosome. While the differing nuclease sensitivity of FACT-bound nucleosomes could also be explained by the demonstrated ability of FACT to alter nucleosome structure, transcription inhibition restores nuclease resistance, suggesting that it is not due to FACT interaction alone. Collectively, these results are consistent with a model in which FACT is targeted to transcribed genes through preferential interaction with RNAP-disrupted nucleosomes.
FACT（促进染色质转位）复合物是一种保守的复合物，它维持转录活跃基因的染色质结构。与这一事实一致的是，FACT 在高度表达的基因上富集，但它如何靶向这些区域尚不清楚。 ，FACT 结合不稳定的核小体，支持这样的假设，即 FACT 通过识别 RNA 聚合酶（RNAP）破坏的核小体靶向转录染色质。在这项研究中，我们使用 中 FACT 占据的高分辨率分析来测试这一假设。我们证明 FACT 与核小体相互作用 ，并且其与染色质的相互作用依赖于三种 RNAP 中的任何一种转录。微球菌核酸酶抗性片段的深度测序表明，与大量染色质相比，FACT 结合的核小体表现出不同的核酸酶敏感性，这与修饰的核小体结构是该复合物的首选配体一致。有趣的是，FACT 结合的核小体的一部分可能是“重叠二核小体”，其中一个组蛋白八聚体侵入相邻核小体通常占据的约 147bp 区域。虽然 FACT 结合的核小体的不同核酸酶敏感性也可以用 FACT 改变核小体结构的能力来解释，但转录抑制恢复了核酸酶抗性，这表明这不是由于 FACT 相互作用本身。总的来说，这些结果与这样一种模型一致，即 FACT 通过与 RNAP 破坏的核小体优先相互作用而靶向转录基因。
