Neuronal activity-induced BRG1 phosphorylation regulates enhancer activation

Area of Science:

• Molecular Biology
• Neuroscience
• Epigenetics

Background:

• Neuronal activity triggers gene expression changes through enhancer elements.
• The SWI/SNF-related BAF complex, containing BRG1, is implicated in chromatin remodeling.

Purpose of the Study:

• To investigate the role of BRG1 in regulating neuronal activity-induced enhancers.
• To elucidate the mechanism by which BRG1 controls enhancer activity and gene expression.

Main Methods:

• Chromatin immunoprecipitation (ChIP) assays to assess protein recruitment to enhancers.
• Analysis of enhancer-promoter looping and RNA polymerase II binding.
• Generation and analysis of mice with specific BRG1 mutations (non-phosphorylatable and phosphomimic).
• Behavioral tests in mice to assess anxiety-like phenotypes and stress responses.

Main Results:

• BRG1 is recruited to enhancers in an H3K27Ac-dependent manner upon neuronal stimulation.
• BRG1 influences cohesin binding, enhancer-promoter looping, RNA polymerase II recruitment, and enhancer RNA expression.
• A specific serine phosphorylation site on BRG1, sensitive to CaMKII, modulates its interactions with co-factors.
• Mutant mice with non-phosphorylatable BRG1 show impaired activity-dependent gene induction, while phosphomimic BRG1 enhances it.
• BRG1 phosphorylation is linked to anxiety-like behaviors and altered stress responses in mice.

Conclusions:

• BRG1 is a critical regulator of neuronal activity-induced enhancers.
• Phosphorylation of BRG1 acts as a molecular switch, connecting neuronal signaling to gene activation via enhancers.
• Dysregulation of this BRG1-mediated mechanism contributes to altered stress responses and anxiety-like phenotypes.