High mobility group proteins: the multifaceted regulators of chromatin dynamics

DNA super-coiling and architectural proteins are the key players that maintain the chromatin in its compact state. Genomic DNA needs to be packaged such that it takes minimum space and can simultaneously be accessed for various DNA dependent processes. Architectural proteins are instrumental in organizing the dynamic higher order chromatin structure by effectuating a concerted effort among themselves and other nuclear proteins across spatio-temporal scales. The regulation of these proteins and their interaction with DNA modify the cellular phenotype by the modulation of gene expression. This review focuses on the structure–function relationship of three broad families of High mobility groups (HMGs) of protein, namely HMGA, HMGN and HMG-Box which are major chromatin architectural components of the eukaryotes. These nuclear elements not only act as architectural proteins but also play a multifaceted role in chromatin dynamics by facilitating interaction with nucleosomes, nucleosome-remodeling machines, transcription factors and histones.