In diverse conditions, intrinsic chromatin condensates have liquid-like material properties.
In diverse conditions, intrinsic chromatin condensates have liquid-like material properties.
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DOI：
10.1073/pnas.2218085120
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发表时间：
2023-05-02
影响因子：
11.1
通讯作者：
Rosen, Michael K.
中科院分区：
文献类型：
--
作者：
Gibson, Bryan A.;Blaukopf, Claudia;Lou, Tracy;Chen, Lifeng;Doolittle, Lynda K.;Finkelstein, Ilya;Narlikar, Geeta J.;Gerlich, Daniel W.;Rosen, Michael K.
真核生物染色质的组织在许多核过程中是重要的。最近的研究表明，染色质片段可以在体外盐的存在下通过相分离自组装成微米级的结构。关于这些结构通常是否具有液体样或固体样行为存在差异，这是考虑细胞中如何通过环挤出进行转录和染色体重塑等过程的重要区别。在这里，我们解决冲突的报告，证明染色质凝聚物在不同的溶液条件下具有液体样的行为和描述方面的样品处理，可能会导致人为的固体样的行为。我们的数据表明，染色质如何在短尺度上是动态的，但在长尺度上受到限制，正如在细胞中观察到的那样。真核生物的核DNA包裹在组蛋白周围，在染色质纤维上形成核小体。染色质纤维动态折叠成环和染色质致密程度的变化调节基本过程，如转录、重组和有丝分裂染色体分离。我们对染色质的物理性质的理解是有限的，即使在高度紧凑的状态下，染色质也可以动态重塑。以前，我们报道了染色质具有相分离和形成动态液体样凝聚物的内在能力，这可以由细胞因子调节[B。a.吉布森等人，Cell 179，470 - 484.e421（2019）]。最近的一些相互矛盾的报告声称，凝结物的流动性需要一组特定的溶液条件，否则凝结物将是固体[J。汉森，K. Maeshima，M. J. Hendzel，表观遗传学染色质14，50（2021）; H. Strickfaden等人，Cell 183，1772 - 1784.e1713（2020）]。我们试图解决这些差异，因为我们有信心将这些生物物理观察转化为细胞的能力需要它们的精确表征。此外，染色质组装是动态的还是静态的影响了转录、环挤出和重塑等过程如何在细胞内参与它们。在这里，我们表明在不同的条件下，没有特定的缓冲成分，染色质片段形成相分离的液体在体外。我们还探讨了样品制备和成像如何影响染色质凝聚动力学的实验观察。最后，我们描述了液体样的体外行为可以转化为局部动态，但在细胞中观察到的全局约束的染色质运动。
The organization of eukaryotic chromatin is important in many nuclear processes. Recent studies have shown that chromatin fragments can self-assemble by phase separation into micron-scale structures in the presence of salt in vitro. There are discrepancies regarding whether these structures generally have liquid-like or solid-like behaviors, an important distinction in considering how processes such as transcription and chromosome remodeling by loop extrusion can occur in cells. Here, we resolve conflicting reports by demonstrating that chromatin condensates have liquid-like behaviors in diverse solution conditions and describing aspects of sample handling that can lead to artifactual solid-like behaviors. Our data suggest how chromatin can be dynamic on short length scales but restrained on long length scales, as observed in cells. Nuclear DNA in eukaryotes is wrapped around histone proteins to form nucleosomes on a chromatin fiber. Dynamic folding of the chromatin fiber into loops and variations in the degree of chromatin compaction regulate essential processes such as transcription, recombination, and mitotic chromosome segregation. Our understanding of the physical properties that allow chromatin to be dynamically remodeled even in highly compacted states is limited. Previously, we reported that chromatin has an intrinsic capacity to phase separate and form dynamic liquid-like condensates, which can be regulated by cellular factors [B. A. Gibson et al., Cell 179, 470–484.e421 (2019)]. Recent contradictory reports claim that a specific set of solution conditions is required for fluidity in condensates that would otherwise be solid [J. C. Hansen, K. Maeshima, M. J. Hendzel, Epigenetics Chromatin 14, 50 (2021); H. Strickfaden et al., Cell 183, 1772–1784.e1713 (2020)]. We sought to resolve these discrepancies, as our ability to translate with confidence these biophysical observations to cells requires their precise characterization. Moreover, whether chromatin assemblies are dynamic or static affects how processes such as transcription, loop extrusion, and remodeling will engage them inside cells. Here, we show in diverse conditions and without specific buffering components that chromatin fragments form phase separated fluids in vitro. We also explore how sample preparation and imaging affect the experimental observation of chromatin condensate dynamics. Last, we describe how liquid-like in vitro behaviors can translate to the locally dynamic but globally constrained chromatin movement observed in cells.
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影响因子：
64.8
作者：
Brogaard, Kristin;Xi, Liqun;Wang, Ji-Ping;Widom, Jonathan
通讯作者：
Widom, Jonathan
影响因子：
64.5
作者：
Dekker J;Mirny L
通讯作者：
Mirny L
影响因子：
4.6
作者：
Elie A;Prezel E;Guérin C;Denarier E;Ramirez-Rios S;Serre L;Andrieux A;Fourest-Lieuvin A;Blanchoin L;Arnal I
通讯作者：
Arnal I
影响因子：
8.8
作者：
Gómez-García PA;Portillo-Ledesma S;Neguembor MV;Pesaresi M;Oweis W;Rohrlich T;Wieser S;Meshorer E;Schlick T;Cosma MP;Lakadamyali M
通讯作者：
Lakadamyali M
影响因子：
3.9
作者：
Hansen JC;Maeshima K;Hendzel MJ
通讯作者：
Hendzel MJ