Determining the conformation of chromatin in cells at the nucleosome level and its relationship to cellular processes has been a central challenge in biology. We show that in quiescent yeast, widespread transcriptional repression coincides with the local compaction of chromatin fibers into structures that are less condensed and more heteromorphic than canonical 30-nanometer forms. Acetylation or substitution of H4 tail residues decompacts fibers and leads to global transcriptional de-repression. Fiber decompaction also increases the rate of loop extrusion by condensin. These findings establish a role for H4 tail-dependent local chromatin fiber folding in regulating transcription and loop extrusion in cells. They also demonstrate the physiological relevance of canonical chromatin fiber folding mechanisms even in the absence of regular 30-nanometer structures.

中文翻译：

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染色质纤维折叠抑制转录和静态细胞中的环挤出。

在核小体水平上确定细胞中染色质的构象及其与细胞过程的关系一直是生物学的主要挑战。我们显示，在静态酵母中，广泛的转录抑制与染色质纤维的局部压实同时发生，与标准的30纳米形式相比，其凝结程度更小，形态更不规则。H4尾部残基的乙酰化或取代使纤维致密化，并导致整体转录抑制。纤维分解也增加了凝集素对毛圈的挤出速度。这些发现建立了H4尾部依赖的局部染色质纤维折叠在调节细胞转录和环挤出中的作用。