The SWI/SNF PBAF complex facilitates REST occupancy at repressive chromatin

Area of Science:

• Chromatin biology
• Cancer epigenetics
• Molecular mechanisms of gene regulation

Background:

• SWI/SNF chromatin remodelers exist in distinct complexes with varied functions.
• Mutations in SWI/SNF subunits, like ARID2 in melanoma, alter chromatin accessibility.
• The interplay between PBAF, PRC2, and transcription factors in cancer is not fully understood.

Purpose of the Study:

• To investigate the role of PBAF complexes in melanoma epigenomics.
• To understand how ARID2 mutations affect chromatin states and gene expression in melanoma.
• To elucidate the functional relationship between PBAF, PRC2, and the REST transcription factor.

Main Methods:

• Comprehensive epigenomic profiling of SWI/SNF complexes in melanoma and melanocytes.
• Time-resolved assays to assess chromatin remodeling sensitivity.
• Analysis of transcription factor binding (REST) at PBAF-occupied regions.
• Correlation of gene expression signatures with ARID2 mutation status in patient cohorts.

Main Results:

• Identified PBAF-exclusive regions co-localized with PRC2 and repressive chromatin.
• PBAF-bound regions exhibit lower sensitivity to ATPase-mediated remodeling compared to BAF sites.
• PBAF/PRC2-bound loci are enriched for the repressive transcription factor REST.
• ARID2 loss disrupts PBAF, impairing REST binding and leading to upregulation of synaptic/neuronal genes.
• This gene signature is conserved in melanoma patients with ARID2 mutations.

Conclusions:

• PBAF plays a unique role in facilitating REST accessibility at repressed chromatin.
• ARID2 mutations in melanoma disrupt PBAF function, leading to aberrant gene expression.
• These findings highlight a novel epigenetic mechanism in melanoma pathogenesis with potential therapeutic implications.