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Histone post-translational modifications play significant roles in gene regulation processes. Among many approaches, chemical protein synthesis has been a successful and promising method for the preparation of homogeneous products of site-specifically modified histones for elucidation of their biological significance. In this short review, we describe the recent advances in synthetic toolbox for histone proteins such as thioester precursors, chemical ubiquitination, and one-pot peptide ligation., Competing Interests: Conflict of interest statement The authors declare no conflict of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Reversible post-translational modifications of histone proteins in eukaryotic chromatin are closely tied to gene function and cellular development. Specific combinations of histone modifications, or marks, are implicated in distinct DNA-templated processes mediated by a range of chromatin-associated enzymes that install, erase and interpret the histone code. Mechanistic studies of the precise biochemical relationship between sets of marks and their effects on chromatin function are significantly complicated by the dynamic nature and heterogeneity of marks in cellular chromatin. Protein semisynthesis is a chemical technique that enables the piecewise assembly of uniformly and site-specifically modified histones in quantities sufficient for biophysical and biochemical analyses. Recent pioneering efforts in semisynthesis have yielded access to histones site-specifically modified by entire proteins, such as ubiquitin (Ub) and the small ubiquitin-like modifier (SUMO). Herein, we highlight key studies of biochemical crosstalk involving Ub and SUMO in chromatin that were enabled by histone semisynthesis., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Chromatin is the physiological template of genetic information in all eukaryotic cells, a highly organised complex of DNA and histone proteins central in regulating gene expression and genome organisation. A multitude of histone post-translational modifications (PTMs) have been discovered, providing a glance into the complex interplay of these epigenetic marks in cellular processes. In the last decade, synthetic and chemical biology techniques have emerged to study these modifications, including genetic code expansion, histone semisynthesis and post-translational chemical mutagenesis. These methods allow for the creation of histones carrying synthetic modifications which can in turn be assembled into designer nucleosomes. Their application in vitro and in vivo is now beginning to have an important impact on chromatin biology. Efforts towards introducing multiple labile modifications in histones as well as expanding their use in cellular biology promise new powerful tools to study epigenetics., (Copyright © 2018. Published by Elsevier Ltd.)

Histone modifications dynamically regulate chromatin structure and function, thereby mediating many processes that require access to DNA. Chemical protein synthesis has emerged as a powerful approach for generating homogeneously modified histone analogues in workable amounts for subsequent incorporation into nucleosome arrays for biochemical, functional and structural studies. This short review focuses on the strength of total chemical protein synthesis and semisynthetic approaches to generate ubiquitylated histones in their native or non-native forms and the utility of these analogues to decode the role of ubiquitylation in epigenetics., (Copyright © 2018 Elsevier Ltd. All rights reserved.)