BAFkomplekser

BAF complexes, short for BRG1/BRM Associated Factor complexes, are a family of ATP-dependent chromatin remodeling machines in eukaryotes that belong to the SWI/SNF superfamily. They use energy from ATP hydrolysis to reposition, eject, or restructure nucleosomes, thereby modulating DNA accessibility for transcription, replication, and repair. In metazoans, BAF complexes regulate gene expression during development and differentiation, and their activity integrates with lineage-specific transcription factors and epigenetic marks.

Composition and variants: A BAF complex typically contains a catalytic ATPase, which can be BRG1 (SMARCA4) or BRM (SMARCA2), together with core and accessory subunits. Canonical BAF (cBAF) includes ARID1A or ARID1B (BAF250A/B); PBAF is distinguished by ARID2 and PBRM1 (BAF180); a related assembly called GBAF or ncBAF includes BRD9 and GLTSCR1/GLTSCR1L. The precise subunit composition varies across cell types and developmental stages, giving rise to functional specialization.

Function and mechanisms: BAF complexes are recruited to regulatory regions by transcription factors and histone marks, and remodel the local chromatin landscape to either promote or restrict transcription. They influence cell fate decisions, responses to signaling, and genomic integrity, often through interactions with other chromatin modifiers and transcriptional co-regulators.

Clinical relevance: Alterations in BAF subunits are among the most common drivers of cancer and are implicated in developmental disorders. Loss of SMARCB1/INI1 is a hallmark of malignant rhabdoid tumors; ARID1A mutations are frequent in several cancers; BRG1/SMARCA4 mutations occur in various tumors. Such changes can disrupt chromatin remodeling and gene expression programs.