ChromatinRemodelingKomplexe

Chromatin remodeling refers to the dynamic modification of chromatin architecture that regulates access to DNA. It encompasses ATP-dependent processes that reposition, eject, or restructure nucleosomes, thereby altering the ability of transcription factors, RNA polymerase II, and DNA repair enzymes to access genetic information. Remodeling is essential for transcription initiation and elongation, replication, and repair, and it helps coordinate gene expression programs with cellular context.

The activity is carried out by several conserved families of chromatin-remodeling complexes. The major groups include SWI/SNF, ISWI, CHD, and INO80. These complexes use energy from ATP hydrolysis to slide nucleosomes along DNA, evict histones, or replace standard histones with variants. They often function in concert with histone modifiers and chaperones and are recruited to specific genomic loci by transcription factors or by recognition of histone marks. Access to DNA is thus modulated in a highly regulated, context-dependent manner.

Biological significance and disease relevance are broad. Chromatin remodeling shapes promoter and enhancer accessibility, influences transcriptional programs during development and differentiation, and participates in DNA replication and repair. Dysregulation or mutation of remodeling factors is linked to developmental disorders and cancer; for example, mutations in SWI/SNF subunits such as BRG1 (SMARCA4) and ARID1A are found in various tumors. Beyond development and disease, remodeling interacts with other epigenetic processes to orchestrate gene expression responses to environmental and developmental cues.