Cryo-EM of nucleosome core particle interactions in trans

Silvija Bilokapic,Mario Halic,Mike Strauss

doi:10.1038/s41598-018-25429-1

Silvija Bilokapic, Mario Halic + Show 1 more

Open Access

https://doi.org/10.1038/s41598-018-25429-1

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Journal: Scientific Reports	Publication Date: May 4, 2018
Citations: 55	License type: open-access

Affiliation: Ludwig-Maximilians-Universität München

Abstract

Nucleosomes, the basic unit of chromatin, are repetitively spaced along DNA and regulate genome expression and maintenance. The long linear chromatin molecule is extensively condensed to fit DNA inside the nucleus. How distant nucleosomes interact to build tertiary chromatin structure remains elusive. In this study, we used cryo-EM to structurally characterize different states of long range nucleosome core particle (NCP) interactions. Our structures show that NCP pairs can adopt multiple conformations, but, commonly, two NCPs are oriented with the histone octamers facing each other. In this conformation, the dyad of both nucleosome core particles is facing the same direction, however, the NCPs are laterally shifted and tilted. The histone octamer surface and histone tails in trans NCP pairs remain accessible to regulatory proteins. The overall conformational flexibility of the NCP pair suggests that chromatin tertiary structure is dynamic and allows access of various chromatin modifying machineries to nucleosomes.

Highlights

Nucleosomes, the basic unit of chromatin, are repetitively spaced along DNA and regulate genome expression and maintenance
The most common arrangement of two nucleosome core particle (NCP) in the pair was side-by-side packing with two histone octamers facing each other (Fig. 1B)
This packing is related to the nucleosome packing in the putative 30 nm fiber and tetranucleosome structure[5,9,28] and approximately 52 000 NCP (~50%) particles interact in this way (Fig. 1B, red area)

Summary

Introduction

Nucleosomes, the basic unit of chromatin, are repetitively spaced along DNA and regulate genome expression and maintenance. Results Cryo-EM structure of nucleosome core particle pairs. We collected cryo-EM data of nucleosome core particles assembled on a 149 bp long 601 DNA sequence at physiological salt conditions (150 mM NaCl)[26,27].

Results

Conclusion