The histone chaperone sNASP binds a conserved peptide motif within the globular core of histone H3 through its TPR repeats.

Andrew Bowman,Daria Zinne,Hari R Singh,Lukas Lercher,Teresa Carlomagno,Andreas G Ladurner,Gyula Timinszky

doi:10.1093/nar/gkv1372

Abstract

Eukaryotic chromatin is a complex yet dynamic structure, which is regulated in part by the assembly and disassembly of nucleosomes. Key to this process is a group of proteins termed histone chaperones that guide the thermodynamic assembly of nucleosomes by interacting with soluble histones. Here we investigate the interaction between the histone chaperone sNASP and its histone H3 substrate. We find that sNASP binds with nanomolar affinity to a conserved heptapeptide motif in the globular domain of H3, close to the C-terminus. Through functional analysis of sNASP homologues we identified point mutations in surface residues within the TPR domain of sNASP that disrupt H3 peptide interaction, but do not completely disrupt binding to full length H3 in cells, suggesting that sNASP interacts with H3 through additional contacts. Furthermore, chemical shift perturbations from 1H-15N HSQC experiments show that H3 peptide binding maps to the helical groove formed by the stacked TPR motifs of sNASP. Our findings reveal a new mode of interaction between a TPR repeat domain and an evolutionarily conserved peptide motif found in canonical H3 and in all histone H3 variants, including CenpA and have implications for the mechanism of histone chaperoning within the cell.

Highlights

Our findings reveal a new mode of interaction between a tetratricopeptide repeat motif (TPR) repeat domain and an evolutionarily conserved peptide motif found in canonical H3 and in all histone H3 variants, including CenpA and have implications for the mechanism of histone chaperoning within the cell
We have presented multiple lines of evidence that the TPR motif containing family of histone chaperones, represented by the human sNASP protein, make a high affinity interaction with a discrete peptide epitope located within the globular domain of histone H3
Similar to other chaperone–histone interactions characterized far, the residues of H3 that mediate interaction with sNASP are sequestered within the nucleosome structure (Supplementary Figure S4D), offering an explanation as to why sNASP is found predominantly associated with soluble histones

Summary

Introduction

With respect to histones H3 and H4 in human cells, a growing number of chaperones, including ASF1, the HAT1 complex, NASP, the CAF1 complex, HIRA, DAXX, MCM2 and the FACT complex have been shown to interact with histones in their soluble, non-chromatin bound state [3,4,5,6,7,8,9,10,11,12]. These histone chaperones represent a very diverse set of protein folds. Understanding how these different protein folds interact with their histone substrates is of great importance in understanding chromatin assembly and disassembly processes at the molecular level

Methods

Results

Conclusion