ChromatinRemodelling

Chromatin remodeling, also spelled chromatin remodelling, refers to the dynamic modification of chromatin architecture that regulates access to DNA. It is driven by ATP-dependent chromatin-remodeling complexes that use energy from ATP hydrolysis to reposition, eject, or restructure nucleosomes, thereby altering DNA accessibility for processes such as transcription, replication, and repair.

The major families of chromatin remodelers include SWI/SNF, ISWI, CHD, and INO80, each containing an ATPase subunit of the SNF2 family. These remodelers act by sliding nucleosomes along DNA, evicting histone dimers or entire octamers, and exchanging histone variants. Through these activities, they create nucleosome-free regions at promoters or regulatory elements, expose DNA sequences for binding by transcription factors, and influence higher-order chromatin structure.

Chromatin remodeling is closely coordinated with histone modifications and histone variant exchange. Post-translational modifications such as acetylation and methylation of histones can recruit or modulate remodelers, while histone chaperones and variant incorporation (for example H2A.Z or H3.3) can complement remodeling to establish accessible or repressive chromatin states.

Functional consequences of remodeling include enabling transcription initiation by facilitating pre-initiation complex assembly, aiding elongation by removing or repositioning nucleosomes ahead of RNA polymerase II, and assisting in DNA replication and repair by reorganizing nucleosome barriers. Regulation occurs through recruitment by transcription factors, post-translational modifications of remodelers, and interactions with chromatin modifiers and chaperones. Malfunction or misregulation of chromatin remodeling is linked to developmental disorders and various cancers, highlighting its essential role in genome regulation.