Structural implications of combinatorial interactions within subnucleosomes

Chromatin organizes genomic DNA into a dynamic, compact structure that regulates the genome's accessibility and stability. A increasing amount of research suggests that subnucleosomal particles serve as crucial structural intermediates during chromatin assembly, remodeling, and centromere maintenance, despite the nucleosome general acceptance as the fundamental repeating unit of chromatin. H3:H4and CENP-A:H4 complexes create tetrameric subnucleosome structures that are crucial for nucleosome assembly and for creating the unique centromeric chromatin architecture. Under different physiological conditions, these particles can affect chromatin stability, histone–DNA interactions, and DNA wrapping. By altering the electrostatic interactions between DNA and histone proteins and by maintaining higher-order chromatin structures, divalent cations like Mg²⁺ are known to control chromatin compaction. Nevertheless, limited is referred to about how Mg²⁺ influences the stability and structural dynamics of subnucleosomal structures. In this study, we use atomistic molecular dynamics simulations to study the conformational dynamics and structural characteristics of H3:H4 and CENP-A:H4 subnucleosomes, as well as how Mg²⁺ ions affect their overall structural organization, stability, and interaction patterns.