Structure and function of protein modules in chromatin biology

Chromatin-mediated gene transcription or silencing is a dynamic process in which binding of various proteins or protein complexes can displace nucleosomal histones from DNA to relieve repression or drive the gene into a highly repressed, silent state. Covalent modifications to DNA and histones associated with chromatin structural change play a crucial role in transcriptional regulation, with particular modifications on certain residues associated with a specific transcriptional outcome. In recent years a number of structural domains have been identified within chromatin-associated proteins, including DNA or RNA binding domains, protein-protein interaction domains and domains that recognize specific covalent modifications to histone tails. In this review we discuss the structural features of these protein modules and the functional roles they play in chromatin biology.