Understanding nucleosome dynamics and their links to gene expression and DNA replication

Key Points Nucleosomes are highly dynamic nucleoprotein complexes involved in almost every genomic process across all eukaryotic organisms. Both individual histone and full nucleosome turnover is under tight regulation that is mediated by a diverse set of chaperones and remodellers. Subnucleosomal structures are dynamically generated as intermediaries during transcription and replication and are predicted to exist throughout the genome at specific loci. The precise positioning of a nucleosome is a highly regulated process owing to numerous chaperones and remodeller complexes. Perturbations of nucleosome positioning have been linked to changes in gene expression levels. Nucleosome disassembly and inheritance is carefully regulated during DNA replication with the restoration of the pre-replication positioning linked to transcription. The presence of nucleosomes and their substructures affects local chromatin structure and function. Thus, nucleosome occupancy, their exact positioning and composition need to be dynamically regulated. Advances in genomic technologies have improved our understanding of nucleosome dynamics in various cellular processes, most notably DNA replication and transcription. Advances in genomics technology have provided the means to probe myriad chromatin interactions at unprecedented spatial and temporal resolution. This has led to a profound understanding of nucleosome organization within the genome, revealing that nucleosomes are highly dynamic. Nucleosome dynamics are governed by a complex interplay of histone composition, histone post-translational modifications, nucleosome occupancy and positioning within chromatin, which are influenced by numerous regulatory factors, including general regulatory factors, chromatin remodellers, chaperones and polymerases. It is now known that these dynamics regulate diverse cellular processes ranging from gene transcription to DNA replication and repair.