
H1 히스톤은 이종염색질 침입으로부터 유크로마틴 관련 메틸화 경로를 제한한다.


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Silencing pathways prevent transposable element (TE) proliferation and help to maintain genome integrity through cell division. Silenced genomic regions can be classified as either euchromatic or heterochromatic, and are targeted by genetically separable epigenetic pathways. In plants, the RNA-directed DNA methylation (RdDM) pathway targets mostly euchromatic regions, while CMT DNA methyltransferases are mainly associated with heterochromatin. However, many epigenetic features - including DNA methylation patterning - are largely indistinguishable between these regions, so how the functional separation is maintained is unclear. The linker histone H1 is preferentially localized to heterochromatin and has been proposed to restrict RdDM from encroachment. To test this hypothesis, we followed RdDM genomic localization in an h1 mutant by performing ChIP-seq on the largest subunit, NRPE1, of the central RdDM polymerase, Pol V. Loss of H1 resulted in NRPE1 enrichment predominantly in heterochromatic TEs. Increased NRPE1 binding was associated with increased chromatin accessibility in h1 , suggesting that H1 restricts NRPE1 occupancy by compacting chromatin. However, RdDM occupancy did not impact H1 localization, demonstrating that H1 hierarchically restricts RdDM positioning. H1 mutants experience major symmetric (CG and CHG) DNA methylation gains, and by generating an h1/nrpe1 double mutant, we demonstrate these gains are largely independent of RdDM. However, loss of NRPE1 occupancy from a subset of euchromatic regions in h1 corresponded to loss of methylation in all sequence contexts, while at ectopically bound heterochromatic loci, NRPE1 deposition correlated with increased methylation specifically in the CHH context. Additionally, we found that H1 similarly restricts the occupancy of the methylation reader, SUVH1, and polycomb-mediated H3K27me3. Together, the results support a model whereby H1 helps maintain the exclusivity of heterochromatin by preventing encroachment from other competing pathways.

### Competing Interest Statement

The authors have declared no competing interest.

H1 restricts euchromatin-associated methylation pathways from heterochromatic encroachment

h1-히스톤이-이종염색질-침입으로부터-유크로마틴-관련-메틸화-경로를-제한한다


H1 히스톤이 이종염색질 침입으로부터 유크로마틴 관련 메틸화 경로를 제한한다


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SWR1C 크로마틴 리모델링 효소는 ATP 의존적으로 뉴클레오좀 히스톤 H2A를 히스톤 변이체 H2A.Z로 교환하는 반응을 촉매한다. 이 과정에서 SWR1C는 뉴클레오좀의 산성 패치에 결합하여 효소 활성을 활성화시킨다.


The SWR1C chromatin remodeling enzyme catalyzes the ATP-dependent exchange of nucleosomal histone H2A for the histone variant H2A.Z, a key variant involved in a multitude of nuclear functions. How the 14-subunit SWR1C engages the nucleosomal substrate remains largely unknown. Studies on the ISWI, CHD1, and SWI/SNF families of chromatin remodeling enzymes have demonstrated key roles for the nucleosomal acidic patch for remodeling activity, however a role for this nucleosomal epitope in nucleosome editing by SWR1C has not been tested. Here, we employ a variety of biochemical assays to demonstrate an essential role for the acidic patch in the H2A.Z exchange reaction. Utilizing asymmetrically assembled nucleosomes, we demonstrate that the acidic patches on each face of the nucleosome are required for SWR1C-mediated dimer exchange, suggesting SWR1C engages the nucleosome in a “pincer-like” conformation, engaging both patches simultaneously. Loss of a single acidic patch results in loss of high affinity nucleosome binding and nucleosomal stimulation of ATPase activity. We identify a conserved arginine-rich motif within the Swc5 subunit that binds the acidic patch and is key for dimer exchange activity. In addition, our cryoEM structure of a Swc5-nucleosome complex suggests that promoter proximal, histone H2B ubiquitinylation may regulate H2A.Z deposition. Together these findings provide new insights into how SWR1C engages its nucleosomal substrate to promote efficient H2A.Z deposition.

### Competing Interest Statement

The authors have declared no competing interest.

Dual engagement of the nucleosomal acidic patches is essential for deposition of histone H2A.Z by SWR1C

swr1c-효소가-atpase-활성을-통해-뉴클레오좀-산성-패치에-결합하여-h2a-z-침착을-촉매한다


SWR1C 효소가 ATPase 활성을 통해 뉴클레오좀 산성 패치에 결합하여 H2A.Z 침착을 촉매한다



SWR1C 複合体は、ヌクレオソームの両面の酸性パッチと結合することで、効率的に H2A.Z の導入を触媒する。


swr1c-複合体は-h2a-z-の導入を触媒するためにatpase活性を利用し-ヌクレオソームの酸性パッチと結合する


SWR1C 複合体は H2A.Z の導入を触媒するためにATPase活性を利用し、ヌクレオソームの酸性パッチと結合する



The SWR1C chromatin remodeling complex requires engagement of the nucleosomal acidic patch on both faces of the nucleosome to catalyze efficient deposition of the histone variant H2A.Z.


the-essential-role-of-the-nucleosomal-acidic-patch-in-h2a-z-deposition-by-the-swr1c-chromatin-remodeling-complex


The Essential Role of the Nucleosomal Acidic Patch in H2A.Z Deposition by the SWR1C Chromatin Remodeling Complex
