Chemical “Diversity” of Chromatin Through Histone Variants and Histone Modifications

Abstract

The eukaryotic genome is highly complex and compartmentalized into distinct physical and functional domains. Although the majority of genomic DNA is wrapped around histone proteins in the same manner to form repeating units of nucleosomes, the use of distinct histone variants and the myriad of posttranslational modifications (PTMs) on different histones and amino acid residues create great diversity among these nucleosomes. In this review, we summarize some of the most recent findings in the histone variant and PTM fields and update the readers on our current understanding of various histone-related pathways. Furthermore, we discuss how homotypic or heterotypic deposition of histone variants as well as symmetric or asymmetric histone PTMs within the nucleosome context can further expand the diversity and functionality of chromatin. Altogether, this review highlights the complexity of chromatin composition and organization and their regulatory functions within the eukaryotic genome.