The EZH2 SANT1 Domain is a Histone Reader Providing Sensitivity to the Modification State of the H4 Tail

Tyler M Weaver,Jiachen Liu,Katelyn E Connelly,Chris Coble,Katayoun Varzavand,Emily C Dykhuizen,Catherine A Musselman

doi:10.1016/j.bpj.2017.11.2463

Tyler M Weaver, Jiachen Liu + Show 5 more

Open Access

https://doi.org/10.1016/j.bpj.2017.11.2463

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Abstract

SANT domains are found in a number of chromatin regulators. They contain approximately 50 amino acids and have high similarity to the DNA binding domain of Myb related proteins. Though some SANT domains associate with DNA others have been found to bind unmodified histone tails. There are two SANT domains in Enhancer of Zeste 2 (EZH2), the catalytic subunit of the Polycomb Repressive Complex 2 (PRC2), of unknown function. Here we show that the first SANT domain (SANT1) of EZH2 is a histone binding domain with specificity for the histone H4 N-terminal tail. Using NMR spectroscopy, mutagenesis, and molecular modeling we structurally characterize the SANT1 domain and determine the molecular mechanism of binding to the H4 tail. Though not important for histone binding, we find that the adjacent stimulation response motif (SRM) stabilizes SANT1 and transiently samples its active form in solution. Acetylation of H4K16 (H4K16ac) or acetylation or methylation of H4K20 (H4K20ac and H4K20me3) are seen to abrogate binding of SANT1 to H4, which is consistent with these modifications being anti-correlated with H3K27me3 in-vivo. Our results provide significant insight into this important regulatory region of EZH2 and the first characterization of the molecular mechanism of SANT domain histone binding.

Highlights

2206-Pos Board B222 Phase Separation of Mitochondrial DNA in the Premature Aging Disease Hutchinson-Gilford Progeria Syndrome Marina Mahynski, Tom Misteli
We investigated whether the heterochromatin domain is similar to other membraneless cellular compartments like nucleoli in that it is formed via phase separation
We used Fluorescence Correlation Spectroscopyderived imaging methods to observe bulk movement of Heterochromatin Protein 1a (HP1a) at the heteroeuchromatin interface, and found that proteins exhibit specific dynamic properties associated with phase interfaces, indicating they are held in the heterochromatin domain by surface tension

Summary

Introduction

2206-Pos Board B222 Phase Separation of Mitochondrial DNA in the Premature Aging Disease Hutchinson-Gilford Progeria Syndrome Marina Mahynski, Tom Misteli. We propose that any realistic model of these and other large-scale features of nuclear architecture must account for ATP-fueled non-equilibrium activity, associated with transcriptional processes that are inhomogeneous within and across chromosomes. The model predicts the statistics of the shapes, positioning, and contact maps of individual chromosomes, with the differential positioning of the inactive and active X chromosomes in female (XX), cells emerging as a natural consequence, and our results compare favorably to a broad spectrum of experimental data.

Results

Conclusion