Evolutionary Conservation of Structural and Functional Coupling between the BRM AT-Hook and Bromodomain

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The BAF chromatin remodeling complex plays a vital role in genome regulation.
• BRM and BRG1, the central ATPases of BAF, possess a C-terminal bromodomain that binds acetylated lysines.
• This bromodomain also interacts with DNA via an adjacent lysine/arginine-rich patch.

Purpose of the Study:

• To investigate the evolutionary conservation of the AT-hook and bromodomain module in BAF.
• To dissect the functional contribution of conserved elements in DNA association.
• To understand the structural and functional coupling between the AT-hook and bromodomain.

Main Methods:

• Comparative sequence analysis to assess evolutionary conservation.
• Site-directed mutagenesis to probe functional roles of specific residues.
• Nuclear Magnetic Resonance (NMR) spectroscopy to determine structural interactions.
• Fluorescence anisotropy to measure DNA binding affinity.

Main Results:

• The AT-hook, linker, and bromodomain patch are ancient, conserved over approximately one billion years.
• The lysine/arginine-rich patch and AT-hook elements are critical for high DNA affinity.
• The linker is dispensable for DNA binding affinity but essential for maintaining the relative conformation of the AT-hook and bromodomain.

Conclusions:

• The AT-hook and bromodomain module exhibits ancient conservation, highlighting its functional importance.
• Structural and functional coupling between the AT-hook and bromodomain, mediated by the linker, is crucial for BAF complex activity.
• These findings provide insights into the molecular mechanisms underlying BAF-mediated genome regulation.